diff options
Diffstat (limited to 'absl/strings')
| -rw-r--r-- | absl/strings/BUILD.bazel | 32 | ||||
| -rw-r--r-- | absl/strings/CMakeLists.txt | 35 | ||||
| -rw-r--r-- | absl/strings/internal/cord_internal.cc | 4 | ||||
| -rw-r--r-- | absl/strings/internal/cord_rep_btree.cc | 947 | ||||
| -rw-r--r-- | absl/strings/internal/cord_rep_btree.h | 851 | ||||
| -rw-r--r-- | absl/strings/internal/cord_rep_btree_test.cc | 1352 | ||||
| -rw-r--r-- | absl/strings/internal/cord_rep_test_util.h | 185 |
7 files changed, 3406 insertions, 0 deletions
diff --git a/absl/strings/BUILD.bazel b/absl/strings/BUILD.bazel index b70aac3e..c686e05a 100644 --- a/absl/strings/BUILD.bazel +++ b/absl/strings/BUILD.bazel @@ -269,11 +269,13 @@ cc_library( name = "cord_internal", srcs = [ "internal/cord_internal.cc", + "internal/cord_rep_btree.cc", "internal/cord_rep_consume.cc", "internal/cord_rep_ring.cc", ], hdrs = [ "internal/cord_internal.h", + "internal/cord_rep_btree.h", "internal/cord_rep_consume.h", "internal/cord_rep_flat.h", "internal/cord_rep_ring.h", @@ -296,6 +298,23 @@ cc_library( "//absl/container:layout", "//absl/functional:function_ref", "//absl/meta:type_traits", + "//absl/types:span", + ], +) + +cc_test( + name = "cord_rep_btree_test", + size = "medium", + srcs = ["internal/cord_rep_btree_test.cc"], + copts = ABSL_TEST_COPTS, + visibility = ["//visibility:private"], + deps = [ + ":cord_internal", + ":cord_rep_test_util", + ":strings", + "//absl/base:config", + "//absl/base:raw_logging_internal", + "@com_google_googletest//:gtest_main", ], ) @@ -578,6 +597,19 @@ cc_library( ) cc_library( + name = "cord_rep_test_util", + testonly = 1, + hdrs = ["internal/cord_rep_test_util.h"], + copts = ABSL_DEFAULT_COPTS, + deps = [ + ":cord_internal", + ":strings", + "//absl/base:config", + "//absl/base:raw_logging_internal", + ], +) + +cc_library( name = "cordz_test_helpers", testonly = 1, hdrs = ["cordz_test_helpers.h"], diff --git a/absl/strings/CMakeLists.txt b/absl/strings/CMakeLists.txt index d79ef712..2ddd3c48 100644 --- a/absl/strings/CMakeLists.txt +++ b/absl/strings/CMakeLists.txt @@ -555,12 +555,14 @@ absl_cc_library( cord_internal HDRS "internal/cord_internal.h" + "internal/cord_rep_btree.h" "internal/cord_rep_consume.h" "internal/cord_rep_flat.h" "internal/cord_rep_ring.h" "internal/cord_rep_ring_reader.h" SRCS "internal/cord_internal.cc" + "internal/cord_rep_btree.cc" "internal/cord_rep_consume.cc" "internal/cord_rep_ring.cc" COPTS @@ -849,6 +851,21 @@ absl_cc_library( absl_cc_library( NAME + cord_rep_test_util + HDRS + "internal/cord_rep_test_util.h" + COPTS + ${ABSL_TEST_COPTS} + DEPS + absl::config + absl::cord_internal + absl::raw_logging_internal + absl::strings + TESTONLY +) + +absl_cc_library( + NAME cord_test_helpers HDRS "cord_test_helpers.h" @@ -924,6 +941,24 @@ absl_cc_test( absl_cc_test( NAME + cord_rep_btree_test + SRCS + "internal/cord_rep_btree_test.cc" + COPTS + ${ABSL_TEST_COPTS} + DEPS + absl::base + absl::config + absl::cord_internal + absl::cord_rep_test_util + absl::core_headers + absl::raw_logging_internal + absl::strings + GTest::gmock_main +) + +absl_cc_test( + NAME cord_ring_test SRCS "cord_ring_test.cc" diff --git a/absl/strings/internal/cord_internal.cc b/absl/strings/internal/cord_internal.cc index 6a0b051c..f79cb628 100644 --- a/absl/strings/internal/cord_internal.cc +++ b/absl/strings/internal/cord_internal.cc @@ -18,6 +18,7 @@ #include <memory> #include "absl/container/inlined_vector.h" +#include "absl/strings/internal/cord_rep_btree.h" #include "absl/strings/internal/cord_rep_flat.h" #include "absl/strings/internal/cord_rep_ring.h" @@ -50,6 +51,9 @@ void CordRep::Destroy(CordRep* rep) { rep = left; continue; } + } else if (rep->tag == BTREE) { + CordRepBtree::Destroy(rep->btree()); + rep = nullptr; } else if (rep->tag == RING) { CordRepRing::Destroy(rep->ring()); rep = nullptr; diff --git a/absl/strings/internal/cord_rep_btree.cc b/absl/strings/internal/cord_rep_btree.cc new file mode 100644 index 00000000..6978cfd2 --- /dev/null +++ b/absl/strings/internal/cord_rep_btree.cc @@ -0,0 +1,947 @@ +// Copyright 2021 The Abseil Authors +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#include "absl/strings/internal/cord_rep_btree.h" + +#include <cassert> +#include <cstdint> +#include <iostream> +#include <string> + +#include "absl/base/attributes.h" +#include "absl/base/config.h" +#include "absl/base/internal/raw_logging.h" +#include "absl/strings/internal/cord_internal.h" +#include "absl/strings/internal/cord_rep_consume.h" +#include "absl/strings/internal/cord_rep_flat.h" +#include "absl/strings/str_cat.h" +#include "absl/strings/string_view.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace cord_internal { + +namespace { + +using NodeStack = CordRepBtree * [CordRepBtree::kMaxDepth]; +using EdgeType = CordRepBtree::EdgeType; +using OpResult = CordRepBtree::OpResult; +using CopyResult = CordRepBtree::CopyResult; + +constexpr auto kFront = CordRepBtree::kFront; +constexpr auto kBack = CordRepBtree::kBack; + +// Implementation of the various 'Dump' functions. +// Prints the entire tree structure or 'rep'. External callers should +// not specify 'depth' and leave it to its default (0) value. +// Rep may be a CordRepBtree tree, or a SUBSTRING / EXTERNAL / FLAT node. +void DumpAll(const CordRep* rep, bool include_contents, std::ostream& stream, + int depth = 0) { + // Allow for full height trees + substring -> flat / external nodes. + assert(depth <= CordRepBtree::kMaxDepth + 2); + std::string sharing = const_cast<CordRep*>(rep)->refcount.IsOne() + ? std::string("Private") + : absl::StrCat("Shared(", rep->refcount.Get(), ")"); + std::string sptr = absl::StrCat("0x", absl::Hex(rep)); + + // Dumps the data contents of `rep` if `include_contents` is true. + // Always emits a new line character. + auto maybe_dump_data = [&stream, include_contents](const CordRep* r) { + if (include_contents) { + // Allow for up to 60 wide display of content data, which with some + // indentation and prefix / labels keeps us within roughly 80-100 wide. + constexpr size_t kMaxDataLength = 60; + stream << ", data = \"" + << CordRepBtree::EdgeData(r).substr(0, kMaxDataLength) + << (r->length > kMaxDataLength ? "\"..." : "\""); + } + stream << '\n'; + }; + + // For each level, we print the 'shared/private' state and the rep pointer, + // indented by two spaces per recursive depth. + stream << std::string(depth * 2, ' ') << sharing << " (" << sptr << ") "; + + if (rep->tag == BTREE) { + const CordRepBtree* node = rep->btree(); + std::string label = + node->height() ? absl::StrCat("Node(", node->height(), ")") : "Leaf"; + stream << label << ", len = " << node->length + << ", begin = " << node->begin() << ", end = " << node->end() + << "\n"; + for (CordRep* edge : node->Edges()) { + DumpAll(edge, include_contents, stream, depth + 1); + } + } else if (rep->tag == SUBSTRING) { + const CordRepSubstring* substring = rep->substring(); + stream << "Substring, len = " << rep->length + << ", start = " << substring->start; + maybe_dump_data(rep); + DumpAll(substring->child, include_contents, stream, depth + 1); + } else if (rep->tag >= FLAT) { + stream << "Flat, len = " << rep->length; + maybe_dump_data(rep); + } else if (rep->tag == EXTERNAL) { + stream << "Extn, len = " << rep->length; + maybe_dump_data(rep); + } +} + +// TODO(b/192061034): add 'bytes to copy' logic to avoid large slop on substring +// small data out of large reps, and general efficiency of 'always copy small +// data'. Consider making this a cord rep internal library function. +CordRepSubstring* CreateSubstring(CordRep* rep, size_t offset, size_t n) { + assert(n != 0); + assert(offset + n <= rep->length); + assert(offset != 0 || n != rep->length); + + if (rep->tag == SUBSTRING) { + CordRepSubstring* substring = rep->substring(); + offset += substring->start; + rep = CordRep::Ref(substring->child); + CordRep::Unref(substring); + } + CordRepSubstring* substring = new CordRepSubstring(); + substring->length = n; + substring->tag = SUBSTRING; + substring->start = offset; + substring->child = rep; + return substring; +} + +// TODO(b/192061034): consider making this a cord rep library function. +inline CordRep* MakeSubstring(CordRep* rep, size_t offset, size_t n) { + if (n == rep->length) return rep; + if (n == 0) return CordRep::Unref(rep), nullptr; + return CreateSubstring(rep, offset, n); +} + +// TODO(b/192061034): consider making this a cord rep library function. +inline CordRep* MakeSubstring(CordRep* rep, size_t offset) { + if (offset == 0) return rep; + return CreateSubstring(rep, offset, rep->length - offset); +} + +template <EdgeType edge_type> +inline absl::string_view Consume(absl::string_view s, size_t n) { + return edge_type == kBack ? s.substr(n) : s.substr(0, s.size() - n); +} + +template <EdgeType edge_type> +inline absl::string_view Consume(char* dst, absl::string_view s, size_t n) { + if (edge_type == kBack) { + memcpy(dst, s.data(), n); + return s.substr(n); + } else { + const size_t offset = s.size() - n; + memcpy(dst, s.data() + offset, n); + return s.substr(0, offset); + } +} + +// Known issue / optimization weirdness: the store associated with the +// decrement introduces traffic between cpus (even if the result of that +// traffic does nothing), making this faster than a single call to +// refcount.Decrement() checking the zero refcount condition. +template <typename R, typename Fn> +inline void FastUnref(R* r, Fn&& fn) { + if (r->refcount.IsOne()) { + fn(r); + } else if (!r->refcount.DecrementExpectHighRefcount()) { + fn(r); + } +} + +// Deletes a leaf node data edge. Requires `rep` to be an EXTERNAL or FLAT +// node, or a SUBSTRING of an EXTERNAL or FLAT node. +void DeleteLeafEdge(CordRep* rep) { + for (;;) { + if (rep->tag >= FLAT) { + CordRepFlat::Delete(rep->flat()); + return; + } + if (rep->tag == EXTERNAL) { + CordRepExternal::Delete(rep->external()); + return; + } + assert(rep->tag == SUBSTRING); + CordRepSubstring* substring = rep->substring(); + rep = substring->child; + assert(rep->tag == EXTERNAL || rep->tag >= FLAT); + delete substring; + if (rep->refcount.Decrement()) return; + } +} + +// StackOperations contains the logic to build a left-most or right-most stack +// (leg) down to the leaf level of a btree, and 'unwind' / 'Finalize' methods to +// propagate node changes up the stack. +template <EdgeType edge_type> +struct StackOperations { + // Returns true if the node at 'depth' is not shared, i.e. has a refcount + // of one and all of its parent nodes have a refcount of one. + inline bool owned(int depth) const { return depth < share_depth; } + + // Returns the node at 'depth'. + inline CordRepBtree* node(int depth) const { return stack[depth]; } + + // Builds a `depth` levels deep stack starting at `tree` recording which nodes + // are private in the form of the 'share depth' where nodes are shared. + inline CordRepBtree* BuildStack(CordRepBtree* tree, int depth) { + assert(depth <= tree->height()); + int current_depth = 0; + while (current_depth < depth && tree->refcount.IsOne()) { + stack[current_depth++] = tree; + tree = tree->Edge(edge_type)->btree(); + } + share_depth = current_depth + (tree->refcount.IsOne() ? 1 : 0); + while (current_depth < depth) { + stack[current_depth++] = tree; + tree = tree->Edge(edge_type)->btree(); + } + return tree; + } + + // Builds a stack with the invariant that all nodes are private owned / not + // shared. This is used in iterative updates where a previous propagation + // guaranteed all nodes are owned / private. + inline void BuildOwnedStack(CordRepBtree* tree, int height) { + assert(height <= CordRepBtree::kMaxHeight); + int depth = 0; + while (depth < height) { + assert(tree->refcount.IsOne()); + stack[depth++] = tree; + tree = tree->Edge(edge_type)->btree(); + } + assert(tree->refcount.IsOne()); + share_depth = depth + 1; + } + + // Processes the final 'top level' result action for the tree. + // See the 'Action' enum for the various action implications. + static inline CordRepBtree* Finalize(CordRepBtree* tree, OpResult result) { + switch (result.action) { + case CordRepBtree::kPopped: + if (ABSL_PREDICT_FALSE(tree->height() >= CordRepBtree::kMaxHeight)) { + ABSL_RAW_LOG(FATAL, "Max height exceeded"); + } + return edge_type == kBack ? CordRepBtree::New(tree, result.tree) + : CordRepBtree::New(result.tree, tree); + case CordRepBtree::kCopied: + CordRep::Unref(tree); + ABSL_FALLTHROUGH_INTENDED; + case CordRepBtree::kSelf: + return result.tree; + } + ABSL_INTERNAL_UNREACHABLE; + return result.tree; + } + + // Propagate the action result in 'result' up into all nodes of the stack + // starting at depth 'depth'. 'length' contains the extra length of data that + // was added at the lowest level, and is updated into all nodes of the stack. + // See the 'Action' enum for the various action implications. + // If 'propagate' is true, then any copied node values are updated into the + // stack, which is used for iterative processing on the same stack. + template <bool propagate = false> + inline CordRepBtree* Unwind(CordRepBtree* tree, int depth, size_t length, + OpResult result) { + // TODO(mvels): revisit the below code to check if 3 loops with 3 + // (incremental) conditions is faster than 1 loop with a switch. + // Benchmarking and perf recordings indicate the loop with switch is + // fastest, likely because of indirect jumps on the tight case values and + // dense branches. But it's worth considering 3 loops, as the `action` + // transitions are mono directional. E.g.: + // while (action == kPopped) { + // ... + // } + // while (action == kCopied) { + // ... + // } + // ... + // We also found that an "if () do {}" loop here seems faster, possibly + // because it allows the branch predictor more granular heuristics on + // 'single leaf' (`depth` == 0) and 'single depth' (`depth` == 1) cases + // which appear to be the most common use cases. + if (depth != 0) { + do { + CordRepBtree* node = stack[--depth]; + const bool owned = depth < share_depth; + switch (result.action) { + case CordRepBtree::kPopped: + assert(!propagate); + result = node->AddEdge<edge_type>(owned, result.tree, length); + break; + case CordRepBtree::kCopied: + result = node->SetEdge<edge_type>(owned, result.tree, length); + if (propagate) stack[depth] = result.tree; + break; + case CordRepBtree::kSelf: + node->length += length; + while (depth > 0) { + node = stack[--depth]; + node->length += length; + } + return node; + } + } while (depth > 0); + } + return Finalize(tree, result); + } + + // Invokes `Unwind` with `propagate=true` to update the stack node values. + inline CordRepBtree* Propagate(CordRepBtree* tree, int depth, size_t length, + OpResult result) { + return Unwind</*propagate=*/true>(tree, depth, length, result); + } + + // `share_depth` contains the depth at which the nodes in the stack become + // shared. I.e., if the top most level is shared (i.e.: `!refcount.IsOne()`), + // then `share_depth` is 0. If the 2nd node is shared (and implicitly all + // nodes below that) then `share_depth` is 1, etc. A `share_depth` greater + // than the depth of the stack indicates that none of the nodes in the stack + // are shared. + int share_depth; + + NodeStack stack; +}; + +} // namespace + +void CordRepBtree::Dump(const CordRep* rep, absl::string_view label, + bool include_contents, std::ostream& stream) { + stream << "===================================\n"; + if (!label.empty()) { + stream << label << '\n'; + stream << "-----------------------------------\n"; + } + if (rep) { + DumpAll(rep, include_contents, stream); + } else { + stream << "NULL\n"; + } +} + +void CordRepBtree::Dump(const CordRep* rep, absl::string_view label, + std::ostream& stream) { + Dump(rep, label, false, stream); +} + +void CordRepBtree::Dump(const CordRep* rep, std::ostream& stream) { + Dump(rep, absl::string_view(), false, stream); +} + +void CordRepBtree::DestroyLeaf(CordRepBtree* tree, size_t begin, size_t end) { + for (CordRep* edge : tree->Edges(begin, end)) { + FastUnref(edge, DeleteLeafEdge); + } + Delete(tree); +} + +void CordRepBtree::DestroyNonLeaf(CordRepBtree* tree, size_t begin, + size_t end) { + for (CordRep* edge : tree->Edges(begin, end)) { + FastUnref(edge->btree(), Destroy); + } + Delete(tree); +} + +bool CordRepBtree::IsValid(const CordRepBtree* tree) { +#define NODE_CHECK_VALID(x) \ + if (!(x)) { \ + ABSL_RAW_LOG(ERROR, "CordRepBtree::CheckValid() FAILED: %s", #x); \ + return false; \ + } +#define NODE_CHECK_EQ(x, y) \ + if ((x) != (y)) { \ + ABSL_RAW_LOG(ERROR, \ + "CordRepBtree::CheckValid() FAILED: %s != %s (%s vs %s)", #x, \ + #y, absl::StrCat(x).c_str(), absl::StrCat(y).c_str()); \ + return false; \ + } + + NODE_CHECK_VALID(tree != nullptr); + NODE_CHECK_EQ(tree->tag, BTREE); + NODE_CHECK_VALID(tree->height() <= kMaxHeight); + NODE_CHECK_VALID(tree->begin() < tree->capacity()); + NODE_CHECK_VALID(tree->end() <= tree->capacity()); + NODE_CHECK_VALID(tree->begin() <= tree->end()); + size_t child_length = 0; + for (CordRep* edge : tree->Edges()) { + NODE_CHECK_VALID(edge != nullptr); + if (tree->height() > 0) { + NODE_CHECK_VALID(edge->tag == BTREE); + NODE_CHECK_VALID(edge->btree()->height() == tree->height() - 1); + } else { + NODE_CHECK_VALID(IsDataEdge(edge)); + } + child_length += edge->length; + } + NODE_CHECK_EQ(child_length, tree->length); + if (tree->height() > 0) { + for (CordRep* edge : tree->Edges()) { + if (!IsValid(edge->btree())) return false; + } + } + return true; + +#undef NODE_CHECK_VALID +#undef NODE_CHECK_EQ +} + +#ifndef NDEBUG + +CordRepBtree* CordRepBtree::AssertValid(CordRepBtree* tree) { + if (!IsValid(tree)) { + Dump(tree, "CordRepBtree validation failed:", false, std::cout); + ABSL_RAW_LOG(FATAL, "CordRepBtree::CheckValid() FAILED"); + } + return tree; +} + +const CordRepBtree* CordRepBtree::AssertValid(const CordRepBtree* tree) { + if (!IsValid(tree)) { + Dump(tree, "CordRepBtree validation failed:", false, std::cout); + ABSL_RAW_LOG(FATAL, "CordRepBtree::CheckValid() FAILED"); + } + return tree; +} + +#endif // NDEBUG + +template <EdgeType edge_type> +inline OpResult CordRepBtree::AddEdge(bool owned, CordRep* edge, size_t delta) { + if (size() >= kMaxCapacity) return {New(edge), kPopped}; + OpResult result = ToOpResult(owned); + result.tree->Add<edge_type>(edge); + result.tree->length += delta; + return result; +} + +template <EdgeType edge_type> +OpResult CordRepBtree::SetEdge(bool owned, CordRep* edge, size_t delta) { + OpResult result; + const size_t idx = index(edge_type); + if (owned) { + result = {this, kSelf}; + CordRep::Unref(edges_[idx]); + } else { + // Create a copy containing all unchanged edges. Unchanged edges are the + // open interval [begin, back) or [begin + 1, end) depending on `edge_type`. + // We conveniently cover both case using a constexpr `shift` being 0 or 1 + // as `end :== back + 1`. + result = {CopyRaw(), kCopied}; + constexpr int shift = edge_type == kFront ? 1 : 0; + for (CordRep* r : Edges(begin() + shift, back() + shift)) { + CordRep::Ref(r); + } + } + result.tree->edges_[idx] = edge; + result.tree->length += delta; + return result; +} + +template <EdgeType edge_type> +CordRepBtree* CordRepBtree::AddCordRep(CordRepBtree* tree, CordRep* rep) { + const int depth = tree->height(); + const size_t length = rep->length; + StackOperations<edge_type> ops; + CordRepBtree* leaf = ops.BuildStack(tree, depth); + const OpResult result = + leaf->AddEdge<edge_type>(ops.owned(depth), rep, length); + return ops.Unwind(tree, depth, length, result); +} + +template <> +CordRepBtree* CordRepBtree::NewLeaf<kBack>(absl::string_view data, + size_t extra) { + CordRepBtree* leaf = CordRepBtree::New(0); + size_t length = 0; + size_t end = 0; + const size_t cap = leaf->capacity(); + while (!data.empty() && end != cap) { + auto* flat = CordRepFlat::New(data.length() + extra); + flat->length = (std::min)(data.length(), flat->Capacity()); + length += flat->length; + leaf->edges_[end++] = flat; + data = Consume<kBack>(flat->Data(), data, flat->length); + } + leaf->length = length; + leaf->set_end(end); + return leaf; +} + +template <> +CordRepBtree* CordRepBtree::NewLeaf<kFront>(absl::string_view data, + size_t extra) { + CordRepBtree* leaf = CordRepBtree::New(0); + size_t length = 0; + size_t begin = leaf->capacity(); + leaf->set_end(leaf->capacity()); + while (!data.empty() && begin != 0) { + auto* flat = CordRepFlat::New(data.length() + extra); + flat->length = (std::min)(data.length(), flat->Capacity()); + length += flat->length; + leaf->edges_[--begin] = flat; + data = Consume<kFront>(flat->Data(), data, flat->length); + } + leaf->length = length; + leaf->set_begin(begin); + return leaf; +} + +template <> +absl::string_view CordRepBtree::AddData<kBack>(absl::string_view data, + size_t extra) { + assert(!data.empty()); + assert(size() < capacity()); + AlignBegin(); + const size_t cap = capacity(); + do { + CordRepFlat* flat = CordRepFlat::New(data.length() + extra); + const size_t n = (std::min)(data.length(), flat->Capacity()); + flat->length = n; + edges_[fetch_add_end(1)] = flat; + data = Consume<kBack>(flat->Data(), data, n); + } while (!data.empty() && end() != cap); + return data; +} + +template <> +absl::string_view CordRepBtree::AddData<kFront>(absl::string_view data, + size_t extra) { + assert(!data.empty()); + assert(size() < capacity()); + AlignEnd(); + do { + CordRepFlat* flat = CordRepFlat::New(data.length() + extra); + const size_t n = (std::min)(data.length(), flat->Capacity()); + flat->length = n; + edges_[sub_fetch_begin(1)] = flat; + data = Consume<kFront>(flat->Data(), data, n); + } while (!data.empty() && begin() != 0); + return data; +} + +template <EdgeType edge_type> +CordRepBtree* CordRepBtree::AddData(CordRepBtree* tree, absl::string_view data, + size_t extra) { + if (ABSL_PREDICT_FALSE(data.empty())) return tree; + + const size_t original_data_size = data.size(); + int depth = tree->height(); + StackOperations<edge_type> ops; + CordRepBtree* leaf = ops.BuildStack(tree, depth); + + // If there is capacity in the last edge, append as much data + // as possible into this last edge. + if (leaf->size() < leaf->capacity()) { + OpResult result = leaf->ToOpResult(ops.owned(depth)); + data = result.tree->AddData<edge_type>(data, extra); + if (data.empty()) { + result.tree->length += original_data_size; + return ops.Unwind(tree, depth, original_data_size, result); + } + + // We added some data into this leaf, but not all. Propagate the added + // length to the top most node, and rebuild the stack with any newly copied + // or updated nodes. From this point on, the path (leg) from the top most + // node to the right-most node towards the leaf node is privately owned. + size_t delta = original_data_size - data.size(); + assert(delta > 0); + result.tree->length += delta; + tree = ops.Propagate(tree, depth, delta, result); + ops.share_depth = depth + 1; + } + + // We were unable to append all data into the existing right-most leaf node. + // This means all remaining data must be put into (a) new leaf node(s) which + // we append to the tree. To make this efficient, we iteratively build full + // leaf nodes from `data` until the created leaf contains all remaining data. + // We utilize the `Unwind` method to merge the created leaf into the first + // level towards root that has capacity. On each iteration with remaining + // data, we rebuild the stack in the knowledge that right-most nodes are + // privately owned after the first `Unwind` completes. + for (;;) { + OpResult result = {CordRepBtree::NewLeaf<edge_type>(data, extra), kPopped}; + if (result.tree->length == data.size()) { + return ops.Unwind(tree, depth, result.tree->length, result); + } + data = Consume<edge_type>(data, result.tree->length); + tree = ops.Unwind(tree, depth, result.tree->length, result); + depth = tree->height(); + ops.BuildOwnedStack(tree, depth); + } +} + +template <EdgeType edge_type> +CordRepBtree* CordRepBtree::Merge(CordRepBtree* dst, CordRepBtree* src) { + assert(dst->height() >= src->height()); + + // Capture source length as we may consume / destroy `src`. + const size_t length = src->length; + + // We attempt to merge `src` at its corresponding height in `dst`. + const int depth = dst->height() - src->height(); + StackOperations<edge_type> ops; + CordRepBtree* merge_node = ops.BuildStack(dst, depth); + + // If there is enough space in `merge_node` for all edges from `src`, add all + // edges to this node, making a fresh copy as needed if not privately owned. + // If `merge_node` does not have capacity for `src`, we rely on `Unwind` and + // `Finalize` to merge `src` into the first level towards `root` where there + // is capacity for another edge, or create a new top level node. + OpResult result; + if (merge_node->size() + src->size() <= kMaxCapacity) { + result = merge_node->ToOpResult(ops.owned(depth)); + result.tree->Add<edge_type>(src->Edges()); + result.tree->length += src->length; + if (src->refcount.IsOne()) { + Delete(src); + } else { + for (CordRep* edge : src->Edges()) CordRep::Ref(edge); + CordRepBtree::Unref(src); + } + } else { + result = {src, kPopped}; + } + + // Unless we merged at the top level (i.e.: src and dst are equal height), + // unwind the result towards the top level, and finalize the result. + if (depth) { + return ops.Unwind(dst, depth, length, result); + } + return ops.Finalize(dst, result); +} + +CopyResult CordRepBtree::CopySuffix(size_t offset) { + assert(offset < this->length); + + // As long as `offset` starts inside the last edge, we can 'drop' the current + // depth. For the most extreme example: if offset references the last data + // edge in the tree, there is only a single edge / path from the top of the + // tree to that last edge, so we can drop all the nodes except that edge. + // The fast path check for this is `back->length >= length - offset`. + int height = this->height(); + CordRepBtree* node = this; + size_t len = node->length - offset; + CordRep* back = node->Edge(kBack); + while (back->length >= len) { + offset = back->length - len; + if (--height < 0) { + return {MakeSubstring(CordRep::Ref(back), offset), height}; + } + node = back->btree(); + back = node->Edge(kBack); + } + if (offset == 0) return {CordRep::Ref(node), height}; + + // Offset does not point into the last edge, so we span at least two edges. + // Find the index of offset with `IndexBeyond` which provides us the edge + // 'beyond' the offset if offset is not a clean starting point of an edge. + Position pos = node->IndexBeyond(offset); + CordRepBtree* sub = node->CopyToEndFrom(pos.index, len); + const CopyResult result = {sub, height}; + + // `pos.n` contains a non zero value if the offset is not an exact starting + // point of an edge. In this case, `pos.n` contains the 'trailing' amount of + // bytes of the edge preceding that in `pos.index`. We need to iteratively + // adjust the preceding edge with the 'broken' offset until we have a perfect + // start of the edge. + while (pos.n != 0) { + assert(pos.index >= 1); + const size_t begin = pos.index - 1; + sub->set_begin(begin); + CordRep* const edge = node->Edge(begin); + + len = pos.n; + offset = edge->length - len; + + if (--height < 0) { + sub->edges_[begin] = MakeSubstring(CordRep::Ref(edge), offset, len); + return result; + } + + node = edge->btree(); + pos = node->IndexBeyond(offset); + + CordRepBtree* nsub = node->CopyToEndFrom(pos.index, len); + sub->edges_[begin] = nsub; + sub = nsub; + } + sub->set_begin(pos.index); + return result; +} + +CopyResult CordRepBtree::CopyPrefix(size_t n) { + assert(n > 0); + assert(n <= this->length); + + // As long as `n` does not exceed the length of the first edge, we can 'drop' + // the current depth. For the most extreme example: if we'd copy a 1 byte + // prefix from a tree, there is only a single edge / path from the top of the + // tree to the single data edge containing this byte, so we can drop all the + // nodes except the data node. + int height = this->height(); + CordRepBtree* node = this; + CordRep* front = node->Edge(kFront); + while (front->length >= n) { + if (--height < 0) return {MakeSubstring(CordRep::Ref(front), 0, n), -1}; + node = front->btree(); + front = node->Edge(kFront); + } + if (node->length == n) return {CordRep::Ref(node), height}; + + // `n` spans at least two nodes, find the end point of the span. + Position pos = node->IndexOf(n); + + // Create a partial copy of the node up to `pos.index`, with a defined length + // of `n`. Any 'partial last edge' is added further below as needed. + CordRepBtree* sub = node->CopyBeginTo(pos.index, n); + const CopyResult result = {sub, height}; + + // `pos.n` contains the 'offset inside the edge for IndexOf(n)'. As long as + // this is not zero, we don't have a 'clean cut', so we need to make a + // (partial) copy of that last edge, and repeat this until pos.n is zero. + while (pos.n != 0) { + size_t end = pos.index; + n = pos.n; + + CordRep* edge = node->Edge(pos.index); + if (--height < 0) { + sub->edges_[end++] = MakeSubstring(CordRep::Ref(edge), 0, n); + sub->set_end(end); + AssertValid(result.edge->btree()); + return result; + } + + node = edge->btree(); + pos = node->IndexOf(n); + CordRepBtree* nsub = node->CopyBeginTo(pos.index, n); + sub->edges_[end++] = nsub; + sub->set_end(end); + sub = nsub; + } + sub->set_end(pos.index); + AssertValid(result.edge->btree()); + return result; +} + +CordRep* CordRepBtree::SubTree(size_t offset, size_t n) { + assert(n <= this->length); + assert(offset <= this->length - n); + if (ABSL_PREDICT_FALSE(n == 0)) return nullptr; + + CordRepBtree* node = this; + int height = node->height(); + Position front = node->IndexOf(offset); + CordRep* left = node->edges_[front.index]; + while (front.n + n <= left->length) { + if (--height < 0) return MakeSubstring(CordRep::Ref(left), front.n, n); + node = left->btree(); + front = node->IndexOf(front.n); + left = node->edges_[front.index]; + } + + const Position back = node->IndexBefore(front, n); + CordRep* const right = node->edges_[back.index]; + assert(back.index > front.index); + + // Get partial suffix and prefix entries. + CopyResult prefix; + CopyResult suffix; + if (height > 0) { + // Copy prefix and suffix of the boundary nodes. + prefix = left->btree()->CopySuffix(front.n); + suffix = right->btree()->CopyPrefix(back.n); + + // If there is an edge between the prefix and suffix edges, then the tree + // must remain at its previous (full) height. If we have no edges between + // prefix and suffix edges, then the tree must be as high as either the + // suffix or prefix edges (which are collapsed to their minimum heights). + if (front.index + 1 == back.index) { + height = (std::max)(prefix.height, suffix.height) + 1; + } + + // Raise prefix and suffixes to the new tree height. + for (int h = prefix.height + 1; h < height; ++h) { + prefix.edge = CordRepBtree::New(prefix.edge); + } + for (int h = suffix.height + 1; h < height; ++h) { + suffix.edge = CordRepBtree::New(suffix.edge); + } + } else { + // Leaf node, simply take substrings for prefix and suffix. + prefix = CopyResult{MakeSubstring(CordRep::Ref(left), front.n), -1}; + suffix = CopyResult{MakeSubstring(CordRep::Ref(right), 0, back.n), -1}; + } + + // Compose resulting tree. + CordRepBtree* sub = CordRepBtree::New(height); + size_t end = 0; + sub->edges_[end++] = prefix.edge; + for (CordRep* r : node->Edges(front.index + 1, back.index)) { + sub->edges_[end++] = CordRep::Ref(r); + } + sub->edges_[end++] = suffix.edge; + sub->set_end(end); + sub->length = n; + return AssertValid(sub); +} + +CordRepBtree* CordRepBtree::MergeTrees(CordRepBtree* left, + CordRepBtree* right) { + return left->height() >= right->height() ? Merge<kBack>(left, right) + : Merge<kFront>(right, left); +} + +bool CordRepBtree::IsFlat(absl::string_view* fragment) const { + if (height() == 0 && size() == 1) { + if (fragment) *fragment = Data(begin()); + return true; + } + return false; +} + +bool CordRepBtree::IsFlat(size_t offset, const size_t n, + absl::string_view* fragment) const { + assert(n <= this->length); + assert(offset <= this->length - n); + if (ABSL_PREDICT_FALSE(n == 0)) return false; + int height = this->height(); + const CordRepBtree* node = this; + for (;;) { + const Position front = node->IndexOf(offset); + const CordRep* edge = node->Edge(front.index); + if (edge->length < front.n + n) return false; + if (--height < 0) { + if (fragment) *fragment = EdgeData(edge).substr(front.n, n); + return true; + } + offset = front.n; + node = node->Edge(front.index)->btree(); + } +} + +char CordRepBtree::GetCharacter(size_t offset) const { + assert(offset < length); + const CordRepBtree* node = this; + int height = node->height(); + for (;;) { + Position front = node->IndexOf(offset); + if (--height < 0) return node->Data(front.index)[front.n]; + offset = front.n; + node = node->Edge(front.index)->btree(); + } +} + +Span<char> CordRepBtree::GetAppendBufferSlow(size_t size) { + // The inlined version in `GetAppendBuffer()` deals with all heights <= 3. + assert(height() >= 4); + assert(refcount.IsOne()); + + // Build a stack of nodes we may potentially need to update if we find a + // non-shared FLAT with capacity at the leaf level. + const int depth = height(); + CordRepBtree* node = this; + CordRepBtree* stack[kMaxDepth]; + for (int i = 0; i < depth; ++i) { + node = node->Edge(kBack)->btree(); + if (!node->refcount.IsOne()) return {}; + stack[i] = node; + } + + // Must be a privately owned flat. + CordRep* const edge = node->Edge(kBack); + if (!edge->refcount.IsOne() || edge->tag < FLAT) return {}; + + // Must have capacity. + const size_t avail = edge->flat()->Capacity() - edge->length; + if (avail == 0) return {}; + + // Build span on remaining capacity. + size_t delta = (std::min)(size, avail); + Span<char> span = {edge->flat()->Data() + edge->length, delta}; + edge->length += delta; + this->length += delta; + for (int i = 0; i < depth; ++i) { + stack[i]->length += delta; + } + return span; +} + +CordRepBtree* CordRepBtree::CreateSlow(CordRep* rep) { + if (rep->tag == BTREE) return rep->btree(); + + CordRepBtree* node = nullptr; + auto consume = [&node](CordRep* r, size_t offset, size_t length) { + r = MakeSubstring(r, offset, length); + if (node == nullptr) { + node = New(r); + } else { + node = CordRepBtree::AddCordRep<kBack>(node, r); + } + }; + Consume(rep, consume); + return node; +} + +CordRepBtree* CordRepBtree::AppendSlow(CordRepBtree* tree, CordRep* rep) { + if (ABSL_PREDICT_TRUE(rep->tag == BTREE)) { + return MergeTrees(tree, rep->btree()); + } + auto consume = [&tree](CordRep* r, size_t offset, size_t length) { + r = MakeSubstring(r, offset, length); + tree = CordRepBtree::AddCordRep<kBack>(tree, r); + }; + Consume(rep, consume); + return tree; +} + +CordRepBtree* CordRepBtree::PrependSlow(CordRepBtree* tree, CordRep* rep) { + if (ABSL_PREDICT_TRUE(rep->tag == BTREE)) { + return MergeTrees(rep->btree(), tree); + } + auto consume = [&tree](CordRep* r, size_t offset, size_t length) { + r = MakeSubstring(r, offset, length); + tree = CordRepBtree::AddCordRep<kFront>(tree, r); + }; + ReverseConsume(rep, consume); + return tree; +} + +CordRepBtree* CordRepBtree::Append(CordRepBtree* tree, absl::string_view data, + size_t extra) { + return CordRepBtree::AddData<kBack>(tree, data, extra); +} + +CordRepBtree* CordRepBtree::Prepend(CordRepBtree* tree, absl::string_view data, + size_t extra) { + return CordRepBtree::AddData<kFront>(tree, data, extra); +} + +template CordRepBtree* CordRepBtree::AddCordRep<kFront>(CordRepBtree* tree, + CordRep* rep); +template CordRepBtree* CordRepBtree::AddCordRep<kBack>(CordRepBtree* tree, + CordRep* rep); +template CordRepBtree* CordRepBtree::AddData<kFront>(CordRepBtree* tree, + absl::string_view data, + size_t extra); +template CordRepBtree* CordRepBtree::AddData<kBack>(CordRepBtree* tree, + absl::string_view data, + size_t extra); + +} // namespace cord_internal +ABSL_NAMESPACE_END +} // namespace absl diff --git a/absl/strings/internal/cord_rep_btree.h b/absl/strings/internal/cord_rep_btree.h new file mode 100644 index 00000000..f4118fc0 --- /dev/null +++ b/absl/strings/internal/cord_rep_btree.h @@ -0,0 +1,851 @@ +// Copyright 2021 The Abseil Authors +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#ifndef ABSL_STRINGS_INTERNAL_CORD_REP_BTREE_H_ +#define ABSL_STRINGS_INTERNAL_CORD_REP_BTREE_H_ + +#include <cassert> +#include <cstdint> +#include <iosfwd> + +#include "absl/base/config.h" +#include "absl/base/internal/raw_logging.h" +#include "absl/base/optimization.h" +#include "absl/strings/internal/cord_internal.h" +#include "absl/strings/internal/cord_rep_btree.h" +#include "absl/strings/internal/cord_rep_flat.h" +#include "absl/strings/string_view.h" +#include "absl/types/span.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace cord_internal { + +class CordRepBtreeNavigator; + +// CordRepBtree is as the name implies a btree implementation of a Cordrep tree. +// Data is stored at the leaf level only, non leaf nodes contain down pointers +// only. Allowed types of data edges are FLAT, EXTERNAL and SUBSTRINGs of FLAT +// or EXTERNAL nodes. The implementation allows for data to be added to either +// end of the tree only, it does not provide any 'insert' logic. This has the +// benefit that we can expect good fill ratios: all nodes except the outer +// 'legs' will have 100% fill ratios for trees built using Append/Prepend +// methods. Merged trees will typically have a fill ratio well above 50% as in a +// similar fashion, one side of the merged tree will typically have a 100% fill +// ratio, and the 'open' end will average 50%. All operations are O(log(n)) or +// better, and the tree never needs balancing. +// +// All methods accepting a CordRep* or CordRepBtree* adopt a reference on that +// input unless explicitly stated otherwise. All functions returning a CordRep* +// or CordRepBtree* instance transfer a reference back to the caller. +// Simplified, callers both 'donate' and 'consume' a reference count on each +// call, simplifying the API. An example of building a tree: +// +// CordRepBtree* tree = CordRepBtree::Create(MakeFlat("Hello")); +// tree = CordRepBtree::Append(tree, MakeFlat("world")); +// +// In the above example, all inputs are consumed, making each call affecting +// `tree` reference count neutral. The returned `tree` value can be different +// from the input if the input is shared with other threads, or if the tree +// grows in height, but callers typically never have to concern themselves with +// that and trust that all methods DTRT at all times. +class CordRepBtree : public CordRep { + public: + // EdgeType identifies `front` and `back` enum values. + // Various implementations in CordRepBtree such as `Add` and `Edge` are + // generic and templated on operating on either of the boundary edges. + // For more information on the possible edges contained in a CordRepBtree + // instance see the documentation for `edges_`. + enum class EdgeType { kFront, kBack }; + + // Convenience constants into `EdgeType` + static constexpr EdgeType kFront = EdgeType::kFront; + static constexpr EdgeType kBack = EdgeType::kBack; + + // Maximum number of edges: based on experiments and performance data, we can + // pick suitable values resulting in optimum cacheline aligned values. The + // preferred values are based on 64-bit systems where we aim to align this + // class onto 64 bytes, i.e.: 6 = 64 bytes, 14 = 128 bytes, etc. + // TODO(b/192061034): experiment with alternative sizes. + static constexpr size_t kMaxCapacity = 6; + + // Reasonable maximum height of the btree. We can expect a fill ratio of at + // least 50%: trees are always expanded at the front or back. Concatenating + // trees will then typically fold at the top most node, where the lower nodes + // are at least at capacity on one side of joined inputs. At a lower fill + // rate of 4 edges per node, we have capacity for ~16 million leaf nodes. + // We will fail / abort if an application ever exceeds this height, which + // should be extremely rare (near impossible) and be an indication of an + // application error: we do not assume it reasonable for any application to + // operate correctly with such monster trees. + // Another compelling reason for the number `12` is that any contextual stack + // required for navigation or insertion requires 12 words and 12 bytes, which + // fits inside 2 cache lines with some room to spare, and is reasonable as a + // local stack variable compared to Cord's current near 400 bytes stack use. + // The maximum `height` value of a node is then `kMaxDepth - 1` as node height + // values start with a value of 0 for leaf nodes. + static constexpr int kMaxDepth = 12; + static constexpr int kMaxHeight = kMaxDepth - 1; + + // `Action` defines the action for unwinding changes done at the btree's leaf + // level that need to be propagated up to the parent node(s). Each operation + // on a node has an effect / action defined as follows: + // - kSelf + // The operation (add / update, etc) was performed directly on the node as + // the node is private to the current thread (i.e.: not shared directly or + // indirectly through a refcount > 1). Changes can be propagated directly to + // all parent nodes as all parent nodes are also then private to the current + // thread. + // - kCopied + // The operation (add / update, etc) was performed on a copy of the original + // node, as the node is (potentially) directly or indirectly shared with + // other threads. Changes need to be propagated into the parent nodes where + // the old down pointer must be unreffed and replaced with this new copy. + // Such changes to parent nodes may themselves require a copy if the parent + // node is also shared. A kCopied action can propagate all the way to the + // top node where we then must unref the `tree` input provided by the + // caller, and return the new copy. + // - kPopped + // The operation (typically add) could not be satisfied due to insufficient + // capacity in the targeted node, and a new 'leg' was created that needs to + // be added into the parent node. For example, adding a FLAT inside a leaf + // node that is at capacity will create a new leaf node containing that + // FLAT, that needs to be 'popped' up the btree. Such 'pop' actions can + // cascade up the tree if parent nodes are also at capacity. A 'Popped' + // action propagating all the way to the top of the tree will result in + // the tree becoming one level higher than the current tree through a final + // `CordRepBtree::New(tree, popped)` call, resulting in a new top node + // referencing the old tree and the new (fully popped upwards) 'leg'. + enum Action { kSelf, kCopied, kPopped }; + + // Result of an operation on a node. See the `Action` enum for details. + struct OpResult { + CordRepBtree* tree; + Action action; + }; + + // Return value of the CopyPrefix and CopySuffix methods which can + // return a node or data edge at any height inside the tree. + // A height of 0 defines the lowest (leaf) node, a height of -1 identifies + // `edge` as being a plain data node: EXTERNAL / FLAT or SUBSTRING thereof. + struct CopyResult { + CordRep* edge; + int height; + }; + + // Logical position inside a node: + // - index: index of the edge. + // - n: size or offset value depending on context. + struct Position { + size_t index; + size_t n; + }; + + // Creates a btree from the given input. Adopts a ref of `rep`. + // If the input `rep` is itself a btree, i.e., `tag == BTREE`, then this + // function immediately returns `rep->btree()`. If the input is a valid data + // edge (see IsDataEdge()), then a new leaf node is returned containing `rep` + // as the sole data edge. Else, the input is assumed to be a (legacy) concat + // tree, and the input is consumed and transformed into a btree(). + static CordRepBtree* Create(CordRep* rep); + + // Destroys the provided tree. Should only be called by cord internal API's, + // typically after a ref_count.Decrement() on the last reference count. + static void Destroy(CordRepBtree* tree); + + // Appends / Prepends an existing CordRep instance to this tree. + // The below methods accept three types of input: + // 1) `rep` is a data node (See `IsDataNode` for valid data edges). + // `rep` is appended or prepended to this tree 'as is'. + // 2) `rep` is a BTREE. + // `rep` is merged into `tree` respecting the Append/Prepend order. + // 3) `rep` is some other (legacy) type. + // `rep` is converted in place and added to `tree` + // Requires `tree` and `rep` to be not null. + static CordRepBtree* Append(CordRepBtree* tree, CordRep* rep); + static CordRepBtree* Prepend(CordRepBtree* tree, CordRep* rep); + + // Append/Prepend the data in `data` to this tree. + // The `extra` parameter defines how much extra capacity should be allocated + // for any additional FLAT being allocated. This is an optimization hint from + // the caller. For example, a caller may need to add 2 string_views of data + // "abc" and "defghi" which are not consecutive. The caller can in this case + // invoke `AddData(tree, "abc", 6)`, and any newly added flat is allocated + // where possible with at least 6 bytes of extra capacity beyond `length`. + // This helps avoiding data getting fragmented over multiple flats. + // There is no limit on the size of `data`. If `data` can not be stored inside + // a single flat, then the function will iteratively add flats until all data + // has been consumed and appended or prepended to the tree. + static CordRepBtree* Append(CordRepBtree* tree, string_view data, + size_t extra = 0); + static CordRepBtree* Prepend(CordRepBtree* tree, string_view data, + size_t extra = 0); + + // Returns a new tree, containing `n` bytes of data from this instance + // starting at offset `offset`. Where possible, the returned tree shares + // (re-uses) data edges and nodes with this instance to minimize the + // combined memory footprint of both trees. + // Requires `offset + n <= length`. Returns `nullptr` if `n` is zero. + CordRep* SubTree(size_t offset, size_t n); + + // Returns the character at the given offset. + char GetCharacter(size_t offset) const; + + // Returns true if this node holds a single data edge, and if so, sets + // `fragment` to reference the contained data. `fragment` is an optional + // output parameter and allowed to be null. + bool IsFlat(absl::string_view* fragment) const; + + // Returns true if the data of `n` bytes starting at offset `offset` + // is contained in a single data edge, and if so, sets fragment to reference + // the contained data. `fragment` is an optional output parameter and allowed + // to be null. + bool IsFlat(size_t offset, size_t n, absl::string_view* fragment) const; + + // Returns a span (mutable range of bytes) of up to `size` bytes into the + // last FLAT data edge inside this tree under the following conditions: + // - none of the nodes down into the FLAT node are shared. + // - the last data edge in this tree is a non-shared FLAT. + // - the referenced FLAT has additional capacity available. + // If all these conditions are met, a non-empty span is returned, and the + // length of the flat node and involved tree nodes have been increased by + // `span.length()`. The caller is responsible for immediately assigning values + // to all uninitialized data reference by the returned span. + // Requires `this->refcount.IsOne()`: this function forces the caller to do + // this fast path check on the top level node, as this is the most commonly + // shared node of a cord tree. + Span<char> GetAppendBuffer(size_t size); + + // Returns the `height` of the tree. The height of a tree is limited to + // kMaxHeight. `height` is implemented as an `int` as in some places we + // use negative (-1) values for 'data edges'. + int height() const { return static_cast<int>(storage[0]); } + + // Properties: begin, back, end, front/back boundary indexes. + size_t begin() const { return static_cast<size_t>(storage[1]); } + size_t back() const { return static_cast<size_t>(storage[2]) - 1; } + size_t end() const { return static_cast<size_t>(storage[2]); } + size_t index(EdgeType edge) const { + return edge == kFront ? begin() : back(); + } + + // Properties: size and capacity. + // `capacity` contains the current capacity of this instance, where + // `kMaxCapacity` contains the maximum capacity of a btree node. + // For now, `capacity` and `kMaxCapacity` return the same value, but this may + // change in the future if we see benefit in dynamically sizing 'small' nodes + // to 'large' nodes for large data trees. + size_t size() const { return end() - begin(); } + size_t capacity() const { return kMaxCapacity; } + + // Edge access + inline CordRep* Edge(size_t index) const; + inline CordRep* Edge(EdgeType edge_type) const; + inline absl::Span<CordRep* const> Edges() const; + inline absl::Span<CordRep* const> Edges(size_t begin, size_t end) const; + + // Returns reference to the data edge at `index`. + // Requires this instance to be a leaf node, and `index` to be valid index. + inline absl::string_view Data(size_t index) const; + + static const char* EdgeDataPtr(const CordRep* r); + static absl::string_view EdgeData(const CordRep* r); + + // Returns true if the provided rep is a FLAT, EXTERNAL or a SUBSTRING node + // holding a FLAT or EXTERNAL child rep. + static bool IsDataEdge(const CordRep* rep); + + // Diagnostics + static bool IsValid(const CordRepBtree* tree); + static CordRepBtree* AssertValid(CordRepBtree* tree); + static const CordRepBtree* AssertValid(const CordRepBtree* tree); + static void Dump(const CordRep* rep, std::ostream& stream); + static void Dump(const CordRep* rep, absl::string_view label, + std::ostream& stream); + static void Dump(const CordRep* rep, absl::string_view label, + bool include_contents, std::ostream& stream); + + // Adds the edge `edge` to this node if possible. `owned` indicates if the + // current node is potentially shared or not with other threads. Returns: + // - {kSelf, <this>} + // The edge was directly added to this node. + // - {kCopied, <node>} + // The edge was added to a copy of this node. + // - {kPopped, New(edge, height())} + // A new leg with the edge was created as this node has no extra capacity. + template <EdgeType edge_type> + inline OpResult AddEdge(bool owned, CordRep* edge, size_t delta); + + // Replaces the front or back edge with the provided new edge. Returns: + // - {kSelf, <this>} + // The edge was directly set in this node. The old edge is unreffed. + // - {kCopied, <node>} + // A copy of this node was created with the new edge value. + // In both cases, the function adopts a reference on `edge`. + template <EdgeType edge_type> + OpResult SetEdge(bool owned, CordRep* edge, size_t delta); + + // Creates a new empty node at the specified height. + static CordRepBtree* New(int height = 0); + + // Creates a new node containing `rep`, with the height being computed + // automatically based on the type of `rep`. + static CordRepBtree* New(CordRep* rep); + + // Creates a new node containing both `front` and `back` at height + // `front.height() + 1`. Requires `back.height() == front.height()`. + static CordRepBtree* New(CordRepBtree* front, CordRepBtree* back); + + private: + CordRepBtree() = default; + ~CordRepBtree() = default; + + // Initializes the main properties `tag`, `begin`, `end`, `height`. + inline void InitInstance(int height, size_t begin = 0, size_t end = 0); + + // Direct property access begin / end + void set_begin(size_t begin) { storage[1] = static_cast<uint8_t>(begin); } + void set_end(size_t end) { storage[2] = static_cast<uint8_t>(end); } + + // Decreases the value of `begin` by `n`, and returns the new value. Notice + // how this returns the new value unlike atomic::fetch_add which returns the + // old value. This is because this is used to prepend edges at 'begin - 1'. + size_t sub_fetch_begin(size_t n) { + storage[1] -= static_cast<uint8_t>(n); + return storage[1]; + } + + // Increases the value of `end` by `n`, and returns the previous value. This + // function is typically used to append edges at 'end'. + size_t fetch_add_end(size_t n) { + const uint8_t current = storage[2]; + storage[2] = static_cast<uint8_t>(current + n); + return current; + } + + // Returns the index of the last edge starting on, or before `offset`, with + // `n` containing the relative offset of `offset` inside that edge. + // Requires `offset` < length. + Position IndexOf(size_t offset) const; + + // Returns the index of the last edge starting before `offset`, with `n` + // containing the relative offset of `offset` inside that edge. + // This function is useful to find the edges for some span of bytes ending at + // `offset` (i.e., `n` bytes). For example: + // + // Position pos = IndexBefore(n) + // edges = Edges(begin(), pos.index) // All full edges (may be empty) + // last = Sub(Edge(pos.index), 0, pos.n) // Last partial edge (may be empty) + // + // Requires 0 < `offset` <= length. + Position IndexBefore(size_t offset) const; + + // Identical to the above function except starting from the position `front`. + // This function is equivalent to `IndexBefore(front.n + offset)`, with + // the difference that this function is optimized to start at `front.index`. + Position IndexBefore(Position front, size_t offset) const; + + // Returns the index of the edge directly beyond the edge containing offset + // `offset`, with `n` containing the distance of that edge from `offset`. + // This function is useful for iteratively finding suffix nodes and remaining + // partial bytes in left-most suffix nodes as for example in CopySuffix. + // Requires `offset` < length. + Position IndexBeyond(size_t offset) const; + + // Destruction + static void DestroyLeaf(CordRepBtree* tree, size_t begin, size_t end); + static void DestroyNonLeaf(CordRepBtree* tree, size_t begin, size_t end); + static void DestroyTree(CordRepBtree* tree, size_t begin, size_t end); + static void Delete(CordRepBtree* tree) { delete tree; } + + // Creates a new leaf node containing as much data as possible from `data`. + // The data is added either forwards or reversed depending on `edge_type`. + // Callers must check the length of the returned node to determine if all data + // was copied or not. + // See the `Append/Prepend` function for the meaning and purpose of `extra`. + template <EdgeType edge_type> + static CordRepBtree* NewLeaf(absl::string_view data, size_t extra); + + // Creates a raw copy of this Btree node, copying all properties, but + // without adding any references to existing edges. + CordRepBtree* CopyRaw() const; + + // Creates a full copy of this Btree node, adding a reference on all edges. + CordRepBtree* Copy() const; + + // Creates a partial copy of this Btree node, copying all edges up to `end`, + // adding a reference on each copied edge, and sets the length of the newly + // created copy to `new_length`. + CordRepBtree* CopyBeginTo(size_t end, size_t new_length) const; + + // Creates a partial copy of this Btree node, copying all edges starting at + // `begin`, adding a reference on each copied edge, and sets the length of + // the newly created copy to `new_length`. + CordRepBtree* CopyToEndFrom(size_t begin, size_t new_length) const; + + // Returns a tree containing the result of appending `right` to `left`. + static CordRepBtree* MergeTrees(CordRepBtree* left, CordRepBtree* right); + + // Fallback functions for `Create()`, `Append()` and `Prepend()` which + // deal with legacy / non conforming input, i.e.: CONCAT trees. + static CordRepBtree* CreateSlow(CordRep* rep); + static CordRepBtree* AppendSlow(CordRepBtree*, CordRep* rep); + static CordRepBtree* PrependSlow(CordRepBtree*, CordRep* rep); + + // Aligns existing edges to start at index 0, to allow for a new edge to be + // added to the back of the current edges. + inline void AlignBegin(); + + // Aligns existing edges to end at `capacity`, to allow for a new edge to be + // added in front of the current edges. + inline void AlignEnd(); + + // Adds the provided edge to this node. + // Requires this node to have capacity for the edge. Realigns / moves + // existing edges as needed to prepend or append the new edge. + template <EdgeType edge_type> + inline void Add(CordRep* rep); + + // Adds the provided edges to this node. + // Requires this node to have capacity for the edges. Realigns / moves + // existing edges as needed to prepend or append the new edges. + template <EdgeType edge_type> + inline void Add(absl::Span<CordRep* const>); + + // Adds data from `data` to this node until either all data has been consumed, + // or there is no more capacity for additional flat nodes inside this node. + // Requires the current node to be a leaf node, data to be non empty, and the + // current node to have capacity for at least one more data edge. + // Returns any remaining data from `data` that was not added, which is + // depending on the edge type (front / back) either the remaining prefix of + // suffix of the input. + // See the `Append/Prepend` function for the meaning and purpose of `extra`. + template <EdgeType edge_type> + absl::string_view AddData(absl::string_view data, size_t extra); + + // Replace the front or back edge with the provided value. + // Adopts a reference on `edge` and unrefs the old edge. + template <EdgeType edge_type> + inline void SetEdge(CordRep* edge); + + // Returns a partial copy of the current tree containing the first `n` bytes + // of data. `CopyResult` contains both the resulting edge and its height. The + // resulting tree may be less high than the current tree, or even be a single + // matching data edge. For example, if `n == 1`, then the result will be the + // single data edge, and height will be set to -1 (one below the owning leaf + // node). If n == 0, this function returns null. + // Requires `n <= length` + CopyResult CopyPrefix(size_t n); + + // Returns a partial copy of the current tree containing all data starting + // after `offset`. `CopyResult` contains both the resulting edge and its + // height. The resulting tree may be less high than the current tree, or even + // be a single matching data edge. For example, if `n == length - 1`, then the + // result will be a single data edge, and height will be set to -1 (one below + // the owning leaf node). + // Requires `offset < length` + CopyResult CopySuffix(size_t offset); + + // Returns a OpResult value of {this, kSelf} or {Copy(), kCopied} + // depending on the value of `owned`. + inline OpResult ToOpResult(bool owned); + + // Adds `rep` to the specified tree, returning the modified tree. + template <EdgeType edge_type> + static CordRepBtree* AddCordRep(CordRepBtree* tree, CordRep* rep); + + // Adds `data` to the specified tree, returning the modified tree. + // See the `Append/Prepend` function for the meaning and purpose of `extra`. + template <EdgeType edge_type> + static CordRepBtree* AddData(CordRepBtree* tree, absl::string_view data, + size_t extra = 0); + + // Merges `src` into `dst` with `src` being added either before (kFront) or + // after (kBack) `dst`. Requires the height of `dst` to be greater than or + // equal to the height of `src`. + template <EdgeType edge_type> + static CordRepBtree* Merge(CordRepBtree* dst, CordRepBtree* src); + + // Fallback version of GetAppendBuffer for large trees: GetAppendBuffer() + // implements an inlined version for trees of limited height (3 levels), + // GetAppendBufferSlow implements the logic for large trees. + Span<char> GetAppendBufferSlow(size_t size); + + // `edges_` contains all edges starting from this instance. + // These are explicitly `child` edges only, a cord btree (or any cord tree in + // that respect) does not store `parent` pointers anywhere: multiple trees / + // parents can reference the same shared child edge. The type of these edges + // depends on the height of the node. `Leaf nodes` (height == 0) contain `data + // edges` (external or flat nodes, or sub-strings thereof). All other nodes + // (height > 0) contain pointers to BTREE nodes with a height of `height - 1`. + CordRep* edges_[kMaxCapacity]; + + friend class CordRepBtreeTestPeer; + friend class CordRepBtreeNavigator; +}; + +inline CordRepBtree* CordRep::btree() { + assert(tag == BTREE); + return static_cast<CordRepBtree*>(this); +} + +inline const CordRepBtree* CordRep::btree() const { + assert(tag == BTREE); + return static_cast<const CordRepBtree*>(this); +} + +inline void CordRepBtree::InitInstance(int height, size_t begin, size_t end) { + tag = BTREE; + storage[0] = height; + storage[1] = begin; + storage[2] = end; +} + +inline CordRep* CordRepBtree::Edge(size_t index) const { + assert(index >= begin()); + assert(index < end()); + return edges_[index]; +} + +inline CordRep* CordRepBtree::Edge(EdgeType edge_type) const { + return edges_[edge_type == kFront ? begin() : back()]; +} + +inline absl::Span<CordRep* const> CordRepBtree::Edges() const { + return {edges_ + begin(), size()}; +} + +inline absl::Span<CordRep* const> CordRepBtree::Edges(size_t begin, + size_t end) const { + assert(begin <= end); + assert(begin >= this->begin()); + assert(end <= this->end()); + return {edges_ + begin, static_cast<size_t>(end - begin)}; +} + +inline const char* CordRepBtree::EdgeDataPtr(const CordRep* r) { + assert(IsDataEdge(r)); + size_t offset = 0; + if (r->tag == SUBSTRING) { + offset = r->substring()->start; + r = r->substring()->child; + } + return (r->tag >= FLAT ? r->flat()->Data() : r->external()->base) + offset; +} + +inline absl::string_view CordRepBtree::EdgeData(const CordRep* r) { + return absl::string_view(EdgeDataPtr(r), r->length); +} + +inline absl::string_view CordRepBtree::Data(size_t index) const { + assert(height() == 0); + return EdgeData(Edge(index)); +} + +inline bool CordRepBtree::IsDataEdge(const CordRep* rep) { + // The fast path is that `rep` is an EXTERNAL or FLAT node, making the below + // if a single, well predicted branch. We then repeat the FLAT or EXTERNAL + // check in the slow path the SUBSTRING check to optimize for the hot path. + if (rep->tag == EXTERNAL || rep->tag >= FLAT) return true; + if (rep->tag == SUBSTRING) rep = rep->substring()->child; + return rep->tag == EXTERNAL || rep->tag >= FLAT; +} + +inline CordRepBtree* CordRepBtree::New(int height) { + CordRepBtree* tree = new CordRepBtree; + tree->length = 0; + tree->InitInstance(height); + return tree; +} + +inline CordRepBtree* CordRepBtree::New(CordRep* rep) { + CordRepBtree* tree = new CordRepBtree; + int height = rep->tag == BTREE ? rep->btree()->height() + 1 : 0; + tree->length = rep->length; + tree->InitInstance(height, /*begin=*/0, /*end=*/1); + tree->edges_[0] = rep; + return tree; +} + +inline CordRepBtree* CordRepBtree::New(CordRepBtree* front, + CordRepBtree* back) { + assert(front->height() == back->height()); + CordRepBtree* tree = new CordRepBtree; + tree->length = front->length + back->length; + tree->InitInstance(front->height() + 1, /*begin=*/0, /*end=*/2); + tree->edges_[0] = front; + tree->edges_[1] = back; + return tree; +} + +inline void CordRepBtree::DestroyTree(CordRepBtree* tree, size_t begin, + size_t end) { + if (tree->height() == 0) { + DestroyLeaf(tree, begin, end); + } else { + DestroyNonLeaf(tree, begin, end); + } +} + +inline void CordRepBtree::Destroy(CordRepBtree* tree) { + DestroyTree(tree, tree->begin(), tree->end()); +} + +inline CordRepBtree* CordRepBtree::CopyRaw() const { + auto* tree = static_cast<CordRepBtree*>(::operator new(sizeof(CordRepBtree))); + memcpy(static_cast<void*>(tree), this, sizeof(CordRepBtree)); + new (&tree->refcount) Refcount; + return tree; +} + +inline CordRepBtree* CordRepBtree::Copy() const { + CordRepBtree* tree = CopyRaw(); + for (CordRep* rep : Edges()) CordRep::Ref(rep); + return tree; +} + +inline CordRepBtree* CordRepBtree::CopyToEndFrom(size_t begin, + size_t new_length) const { + assert(begin >= this->begin()); + assert(begin <= this->end()); + CordRepBtree* tree = CopyRaw(); + tree->length = new_length; + tree->set_begin(begin); + for (CordRep* edge : tree->Edges()) CordRep::Ref(edge); + return tree; +} + +inline CordRepBtree* CordRepBtree::CopyBeginTo(size_t end, + size_t new_length) const { + assert(end <= capacity()); + assert(end >= this->begin()); + CordRepBtree* tree = CopyRaw(); + tree->length = new_length; + tree->set_end(end); + for (CordRep* edge : tree->Edges()) CordRep::Ref(edge); + return tree; +} + +inline void CordRepBtree::AlignBegin() { + // The below code itself does not need to be fast as typically we have + // mono-directional append/prepend calls, and `begin` / `end` are typically + // adjusted no more than once. But we want to avoid potential register clobber + // effects, making the compiler emit register save/store/spills, and minimize + // the size of code. + const size_t delta = begin(); + if (ABSL_PREDICT_FALSE(delta != 0)) { + const size_t new_end = end() - delta; + set_begin(0); + set_end(new_end); + // TODO(mvels): we can write this using 2 loads / 2 stores depending on + // total size for the kMaxCapacity = 6 case. I.e., we can branch (switch) on + // size, and then do overlapping load/store of up to 4 pointers (inlined as + // XMM, YMM or ZMM load/store) and up to 2 pointers (XMM / YMM), which is a) + // compact and b) not clobbering any registers. + ABSL_INTERNAL_ASSUME(new_end <= kMaxCapacity); +#ifdef __clang__ +#pragma unroll 1 +#endif + for (size_t i = 0; i < new_end; ++i) { + edges_[i] = edges_[i + delta]; + } + } +} + +inline void CordRepBtree::AlignEnd() { + // See comments in `AlignBegin` for motivation on the hand-rolled for loops. + const size_t delta = capacity() - end(); + if (delta != 0) { + const size_t new_begin = begin() + delta; + const size_t new_end = end() + delta; + set_begin(new_begin); + set_end(new_end); + ABSL_INTERNAL_ASSUME(new_end <= kMaxCapacity); +#ifdef __clang__ +#pragma unroll 1 +#endif + for (size_t i = new_end - 1; i >= new_begin; --i) { + edges_[i] = edges_[i - delta]; + } + } +} + +template <> +inline void CordRepBtree::Add<CordRepBtree::kBack>(CordRep* rep) { + AlignBegin(); + edges_[fetch_add_end(1)] = rep; +} + +template <> +inline void CordRepBtree::Add<CordRepBtree::kBack>( + absl::Span<CordRep* const> edges) { + AlignBegin(); + size_t new_end = end(); + for (CordRep* edge : edges) edges_[new_end++] = edge; + set_end(new_end); +} + +template <> +inline void CordRepBtree::Add<CordRepBtree::kFront>(CordRep* rep) { + AlignEnd(); + edges_[sub_fetch_begin(1)] = rep; +} + +template <> +inline void CordRepBtree::Add<CordRepBtree::kFront>( + absl::Span<CordRep* const> edges) { + AlignEnd(); + size_t new_begin = begin() - edges.size(); + set_begin(new_begin); + for (CordRep* edge : edges) edges_[new_begin++] = edge; +} + +template <CordRepBtree::EdgeType edge_type> +inline void CordRepBtree::SetEdge(CordRep* edge) { + const int idx = edge_type == kFront ? begin() : back(); + CordRep::Unref(edges_[idx]); + edges_[idx] = edge; +} + +inline CordRepBtree::OpResult CordRepBtree::ToOpResult(bool owned) { + return owned ? OpResult{this, kSelf} : OpResult{Copy(), kCopied}; +} + +inline CordRepBtree::Position CordRepBtree::IndexOf(size_t offset) const { + assert(offset < length); + size_t index = begin(); + while (offset >= edges_[index]->length) offset -= edges_[index++]->length; + return {index, offset}; +} + +inline CordRepBtree::Position CordRepBtree::IndexBefore(size_t offset) const { + assert(offset > 0); + assert(offset <= length); + size_t index = begin(); + while (offset > edges_[index]->length) offset -= edges_[index++]->length; + return {index, offset}; +} + +inline CordRepBtree::Position CordRepBtree::IndexBefore(Position front, + size_t offset) const { + size_t index = front.index; + offset = offset + front.n; + while (offset > edges_[index]->length) offset -= edges_[index++]->length; + return {index, offset}; +} + +inline CordRepBtree::Position CordRepBtree::IndexBeyond( + const size_t offset) const { + // We need to find the edge which `starting offset` is beyond (>=)`offset`. + // For this we can't use the `offset -= length` logic of IndexOf. Instead, we + // track the offset of the `current edge` in `off`, which we increase as we + // iterate over the edges until we find the matching edge. + size_t off = 0; + size_t index = begin(); + while (offset > off) off += edges_[index++]->length; + return {index, off - offset}; +} + +inline CordRepBtree* CordRepBtree::Create(CordRep* rep) { + if (IsDataEdge(rep)) return New(rep); + return CreateSlow(rep); +} + +inline Span<char> CordRepBtree::GetAppendBuffer(size_t size) { + assert(refcount.IsOne()); + CordRepBtree* tree = this; + const int height = this->height(); + CordRepBtree* n1 = tree; + CordRepBtree* n2 = tree; + CordRepBtree* n3 = tree; + switch (height) { + case 3: + tree = tree->Edge(kBack)->btree(); + if (!tree->refcount.IsOne()) return {}; + n2 = tree; + ABSL_FALLTHROUGH_INTENDED; + case 2: + tree = tree->Edge(kBack)->btree(); + if (!tree->refcount.IsOne()) return {}; + n1 = tree; + ABSL_FALLTHROUGH_INTENDED; + case 1: + tree = tree->Edge(kBack)->btree(); + if (!tree->refcount.IsOne()) return {}; + ABSL_FALLTHROUGH_INTENDED; + case 0: + CordRep* edge = tree->Edge(kBack); + if (!edge->refcount.IsOne()) return {}; + if (edge->tag < FLAT) return {}; + size_t avail = edge->flat()->Capacity() - edge->length; + if (avail == 0) return {}; + size_t delta = (std::min)(size, avail); + Span<char> span = {edge->flat()->Data() + edge->length, delta}; + edge->length += delta; + switch (height) { + case 3: + n3->length += delta; + ABSL_FALLTHROUGH_INTENDED; + case 2: + n2->length += delta; + ABSL_FALLTHROUGH_INTENDED; + case 1: + n1->length += delta; + ABSL_FALLTHROUGH_INTENDED; + case 0: + tree->length += delta; + return span; + } + break; + } + return GetAppendBufferSlow(size); +} + +extern template CordRepBtree* CordRepBtree::AddCordRep<CordRepBtree::kBack>( + CordRepBtree* tree, CordRep* rep); + +extern template CordRepBtree* CordRepBtree::AddCordRep<CordRepBtree::kFront>( + CordRepBtree* tree, CordRep* rep); + +inline CordRepBtree* CordRepBtree::Append(CordRepBtree* tree, CordRep* rep) { + if (ABSL_PREDICT_TRUE(IsDataEdge(rep))) { + return CordRepBtree::AddCordRep<kBack>(tree, rep); + } + return AppendSlow(tree, rep); +} + +inline CordRepBtree* CordRepBtree::Prepend(CordRepBtree* tree, CordRep* rep) { + if (ABSL_PREDICT_TRUE(IsDataEdge(rep))) { + return CordRepBtree::AddCordRep<kFront>(tree, rep); + } + return PrependSlow(tree, rep); +} + +#ifdef NDEBUG + +inline CordRepBtree* CordRepBtree::AssertValid(CordRepBtree* tree) { + return tree; +} + +inline const CordRepBtree* CordRepBtree::AssertValid(const CordRepBtree* tree) { + return tree; +} + +#endif + +} // namespace cord_internal +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_STRINGS_INTERNAL_CORD_REP_BTREE_H_ diff --git a/absl/strings/internal/cord_rep_btree_test.cc b/absl/strings/internal/cord_rep_btree_test.cc new file mode 100644 index 00000000..7a0b7811 --- /dev/null +++ b/absl/strings/internal/cord_rep_btree_test.cc @@ -0,0 +1,1352 @@ +// Copyright 2021 The Abseil Authors +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#include "absl/strings/internal/cord_rep_btree.h" + +#include <cmath> +#include <deque> +#include <iostream> +#include <string> +#include <vector> + +#include "gmock/gmock.h" +#include "gtest/gtest.h" +#include "absl/base/config.h" +#include "absl/base/internal/raw_logging.h" +#include "absl/strings/internal/cord_internal.h" +#include "absl/strings/internal/cord_rep_test_util.h" +#include "absl/strings/str_cat.h" +#include "absl/strings/string_view.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace cord_internal { + +class CordRepBtreeTestPeer { + public: + static void SetEdge(CordRepBtree* node, size_t idx, CordRep* edge) { + node->edges_[idx] = edge; + } + static void AddEdge(CordRepBtree* node, CordRep* edge) { + node->edges_[node->fetch_add_end(1)] = edge; + } +}; + +namespace { + +using ::absl::cordrep_testing::AutoUnref; +using ::absl::cordrep_testing::CordToString; +using ::absl::cordrep_testing::CreateFlatsFromString; +using ::absl::cordrep_testing::CreateRandomString; +using ::absl::cordrep_testing::MakeConcat; +using ::absl::cordrep_testing::MakeExternal; +using ::absl::cordrep_testing::MakeFlat; +using ::absl::cordrep_testing::MakeSubstring; +using ::testing::_; +using ::testing::AllOf; +using ::testing::AnyOf; +using ::testing::Conditional; +using ::testing::ElementsAre; +using ::testing::ElementsAreArray; +using ::testing::Eq; +using ::testing::HasSubstr; +using ::testing::Ne; +using ::testing::Not; +using ::testing::SizeIs; +using ::testing::TypedEq; + +MATCHER_P(EqFlatHolding, data, "Equals flat holding data") { + if (arg->tag < FLAT) { + *result_listener << "Expected FLAT, got tag " << static_cast<int>(arg->tag); + return false; + } + std::string actual = CordToString(arg); + if (actual != data) { + *result_listener << "Expected flat holding \"" << data + << "\", got flat holding \"" << actual << "\""; + return false; + } + return true; +} + +MATCHER_P(IsNode, height, absl::StrCat("Is a valid node of height ", height)) { + if (arg == nullptr) { + *result_listener << "Expected NODE, got nullptr"; + return false; + } + if (arg->tag != BTREE) { + *result_listener << "Expected NODE, got " << static_cast<int>(arg->tag); + return false; + } + if (!CordRepBtree::IsValid(arg->btree())) { + CordRepBtree::Dump(arg->btree(), "Expected valid NODE, got:", false, + *result_listener->stream()); + return false; + } + if (arg->btree()->height() != height) { + *result_listener << "Expected NODE of height " << height << ", got " + << arg->btree()->height(); + return false; + } + return true; +} + +MATCHER_P2(IsSubstring, start, length, + absl::StrCat("Is a substring(start = ", start, ", length = ", length, + ")")) { + if (arg == nullptr) { + *result_listener << "Expected substring, got nullptr"; + return false; + } + if (arg->tag != SUBSTRING) { + *result_listener << "Expected SUBSTRING, got " + << static_cast<int>(arg->tag); + return false; + } + const CordRepSubstring* const substr = arg->substring(); + if (substr->start != start || substr->length != length) { + *result_listener << "Expected substring(" << start << ", " << length + << "), got substring(" << substr->start << ", " + << substr->length << ")"; + return false; + } + return true; +} + +// DataConsumer is a simple helper class used by tests to 'consume' string +// fragments from the provided input in forward or backward direction. +class DataConsumer { + public: + // Starts consumption of `data`. Caller must make sure `data` outlives this + // instance. Consumes data starting at the front if `forward` is true, else + // consumes data from the back. + DataConsumer(absl::string_view data, bool forward) + : data_(data), forward_(forward) {} + + // Return the next `n` bytes from referenced data. + absl::string_view Next(size_t n) { + assert(n <= data_.size() - consumed_); + consumed_ += n; + return data_.substr(forward_ ? consumed_ - n : data_.size() - consumed_, n); + } + + // Returns all data consumed so far. + absl::string_view Consumed() const { + return forward_ ? data_.substr(0, consumed_) + : data_.substr(data_.size() - consumed_); + } + + private: + absl::string_view data_; + size_t consumed_ = 0; + bool forward_; +}; + +// BtreeAdd returns either CordRepBtree::Append or CordRepBtree::Prepend. +CordRepBtree* BtreeAdd(CordRepBtree* node, bool append, + absl::string_view data) { + return append ? CordRepBtree::Append(node, data) + : CordRepBtree::Prepend(node, data); +} + +// Recursively collects all leaf edges from `tree` and appends them to `edges`. +void GetLeafEdges(const CordRepBtree* tree, std::vector<CordRep*>& edges) { + if (tree->height() == 0) { + for (CordRep* edge : tree->Edges()) { + edges.push_back(edge); + } + } else { + for (CordRep* edge : tree->Edges()) { + GetLeafEdges(edge->btree(), edges); + } + } +} + +// Recursively collects and returns all leaf edges from `tree`. +std::vector<CordRep*> GetLeafEdges(const CordRepBtree* tree) { + std::vector<CordRep*> edges; + GetLeafEdges(tree, edges); + return edges; +} + +// Creates a flat containing the hexadecimal value of `i` zero padded +// to at least 4 digits prefixed with "0x", e.g.: "0x04AC". +CordRepFlat* MakeHexFlat(size_t i) { + return MakeFlat(absl::StrCat("0x", absl::Hex(i, absl::kZeroPad4))); +} + +CordRepBtree* MakeLeaf(size_t size = CordRepBtree::kMaxCapacity) { + assert(size <= CordRepBtree::kMaxCapacity); + CordRepBtree* leaf = CordRepBtree::Create(MakeHexFlat(0)); + for (size_t i = 1; i < size; ++i) { + leaf = CordRepBtree::Append(leaf, MakeHexFlat(i)); + } + return leaf; +} + +CordRepBtree* MakeTree(size_t size, bool append = true) { + CordRepBtree* tree = CordRepBtree::Create(MakeHexFlat(0)); + for (size_t i = 1; i < size; ++i) { + tree = append ? CordRepBtree::Append(tree, MakeHexFlat(i)) + : CordRepBtree::Prepend(tree, MakeHexFlat(i)); + } + return tree; +} + +CordRepBtree* CreateTree(absl::string_view data, size_t chunk_size) { + std::vector<CordRep*> flats = CreateFlatsFromString(data, chunk_size); + auto it = flats.begin(); + CordRepBtree* tree = CordRepBtree::Create(*it); + while (++it != flats.end()) tree = CordRepBtree::Append(tree, *it); + return tree; +} + +CordRepBtree* CreateTreeReverse(absl::string_view data, size_t chunk_size) { + std::vector<CordRep*> flats = CreateFlatsFromString(data, chunk_size); + auto rit = flats.rbegin(); + CordRepBtree* tree = CordRepBtree::Create(*rit); + while (++rit != flats.rend()) tree = CordRepBtree::Prepend(tree, *rit); + return tree; +} + +class CordRepBtreeTest : public testing::TestWithParam<bool> { + public: + bool shared() const { return GetParam(); } + + static std::string ToString(testing::TestParamInfo<bool> param) { + return param.param ? "Shared" : "Private"; + } +}; + +INSTANTIATE_TEST_SUITE_P(WithParam, CordRepBtreeTest, testing::Bool(), + CordRepBtreeTest::ToString); + +class CordRepBtreeHeightTest : public testing::TestWithParam<int> { + public: + int height() const { return GetParam(); } + + static std::string ToString(testing::TestParamInfo<int> param) { + return absl::StrCat(param.param); + } +}; + +INSTANTIATE_TEST_SUITE_P(WithHeights, CordRepBtreeHeightTest, + testing::Range(0, CordRepBtree::kMaxHeight), + CordRepBtreeHeightTest::ToString); + +using TwoBools = testing::tuple<bool, bool>; + +class CordRepBtreeDualTest : public testing::TestWithParam<TwoBools> { + public: + bool first_shared() const { return std::get<0>(GetParam()); } + bool second_shared() const { return std::get<1>(GetParam()); } + + static std::string ToString(testing::TestParamInfo<TwoBools> param) { + if (std::get<0>(param.param)) { + return std::get<1>(param.param) ? "BothShared" : "FirstShared"; + } + return std::get<1>(param.param) ? "SecondShared" : "Private"; + } +}; + +INSTANTIATE_TEST_SUITE_P(WithParam, CordRepBtreeDualTest, + testing::Combine(testing::Bool(), testing::Bool()), + CordRepBtreeDualTest::ToString); + +TEST(CordRepBtreeTest, SizeIsMultipleOf64) { + // Only enforce for fully 64-bit platforms. + if (sizeof(size_t) == 8 && sizeof(void*) == 8) { + EXPECT_THAT(sizeof(CordRepBtree) % 64, Eq(0)) << "Should be multiple of 64"; + } +} + +TEST(CordRepBtreeTest, NewDestroyEmptyTree) { + auto* tree = CordRepBtree::New(); + EXPECT_THAT(tree->size(), Eq(0)); + EXPECT_THAT(tree->height(), Eq(0)); + EXPECT_THAT(tree->Edges(), ElementsAre()); + CordRepBtree::Destroy(tree); +} + +TEST(CordRepBtreeTest, NewDestroyEmptyTreeAtHeight) { + auto* tree = CordRepBtree::New(3); + EXPECT_THAT(tree->size(), Eq(0)); + EXPECT_THAT(tree->height(), Eq(3)); + EXPECT_THAT(tree->Edges(), ElementsAre()); + CordRepBtree::Destroy(tree); +} + +TEST(CordRepBtreeTest, Btree) { + CordRep* rep = CordRepBtree::New(); + EXPECT_THAT(rep->btree(), Eq(rep)); + EXPECT_THAT(static_cast<const CordRep*>(rep)->btree(), Eq(rep)); + CordRep::Unref(rep); +#if defined(GTEST_HAS_DEATH_TEST) && !defined(NDEBUG) + rep = MakeFlat("Hello world"); + EXPECT_DEATH(rep->btree(), ".*"); + EXPECT_DEATH(static_cast<const CordRep*>(rep)->btree(), ".*"); + CordRep::Unref(rep); +#endif +} + +TEST(CordRepBtreeTest, EdgeData) { + CordRepFlat* flat = MakeFlat("Hello world"); + CordRepExternal* external = MakeExternal("Hello external"); + CordRep* substr1 = MakeSubstring(1, 6, CordRep::Ref(flat)); + CordRep* substr2 = MakeSubstring(1, 6, CordRep::Ref(external)); + CordRep* concat = MakeConcat(CordRep::Ref(flat), CordRep::Ref(external)); + CordRep* bad_substr = MakeSubstring(1, 2, CordRep::Ref(substr1)); + + EXPECT_TRUE(CordRepBtree::IsDataEdge(flat)); + EXPECT_THAT(CordRepBtree::EdgeDataPtr(flat), + TypedEq<const void*>(flat->Data())); + EXPECT_THAT(CordRepBtree::EdgeData(flat), Eq("Hello world")); + + EXPECT_TRUE(CordRepBtree::IsDataEdge(external)); + EXPECT_THAT(CordRepBtree::EdgeDataPtr(external), + TypedEq<const void*>(external->base)); + EXPECT_THAT(CordRepBtree::EdgeData(external), Eq("Hello external")); + + EXPECT_TRUE(CordRepBtree::IsDataEdge(substr1)); + EXPECT_THAT(CordRepBtree::EdgeDataPtr(substr1), + TypedEq<const void*>(flat->Data() + 1)); + EXPECT_THAT(CordRepBtree::EdgeData(substr1), Eq("ello w")); + + EXPECT_TRUE(CordRepBtree::IsDataEdge(substr2)); + EXPECT_THAT(CordRepBtree::EdgeDataPtr(substr2), + TypedEq<const void*>(external->base + 1)); + EXPECT_THAT(CordRepBtree::EdgeData(substr2), Eq("ello e")); + + EXPECT_FALSE(CordRepBtree::IsDataEdge(concat)); + EXPECT_FALSE(CordRepBtree::IsDataEdge(bad_substr)); +#if defined(GTEST_HAS_DEATH_TEST) && !defined(NDEBUG) + EXPECT_DEATH(CordRepBtree::EdgeData(concat), ".*"); + EXPECT_DEATH(CordRepBtree::EdgeDataPtr(concat), ".*"); + EXPECT_DEATH(CordRepBtree::EdgeData(bad_substr), ".*"); + EXPECT_DEATH(CordRepBtree::EdgeDataPtr(bad_substr), ".*"); +#endif + + CordRep::Unref(bad_substr); + CordRep::Unref(concat); + CordRep::Unref(substr2); + CordRep::Unref(substr1); + CordRep::Unref(external); + CordRep::Unref(flat); +} + +TEST(CordRepBtreeTest, CreateUnrefLeaf) { + auto* flat = MakeFlat("a"); + auto* leaf = CordRepBtree::Create(flat); + EXPECT_THAT(leaf->size(), Eq(1)); + EXPECT_THAT(leaf->height(), Eq(0)); + EXPECT_THAT(leaf->Edges(), ElementsAre(flat)); + CordRepBtree::Unref(leaf); +} + +TEST(CordRepBtreeTest, NewUnrefNode) { + auto* leaf = CordRepBtree::Create(MakeFlat("a")); + CordRepBtree* tree = CordRepBtree::New(leaf); + EXPECT_THAT(tree->size(), Eq(1)); + EXPECT_THAT(tree->height(), Eq(1)); + EXPECT_THAT(tree->Edges(), ElementsAre(leaf)); + CordRepBtree::Unref(tree); +} + +TEST_P(CordRepBtreeTest, AppendToLeafToCapacity) { + AutoUnref refs; + std::vector<CordRep*> flats; + flats.push_back(MakeHexFlat(0)); + auto* leaf = CordRepBtree::Create(flats.back()); + + for (size_t i = 1; i < CordRepBtree::kMaxCapacity; ++i) { + refs.RefIf(shared(), leaf); + flats.push_back(MakeHexFlat(i)); + auto* result = CordRepBtree::Append(leaf, flats.back()); + EXPECT_THAT(result->height(), Eq(0)); + EXPECT_THAT(result, Conditional(shared(), Ne(leaf), Eq(leaf))); + EXPECT_THAT(result->Edges(), ElementsAreArray(flats)); + leaf = result; + } + CordRep::Unref(leaf); +} + +TEST_P(CordRepBtreeTest, PrependToLeafToCapacity) { + AutoUnref refs; + std::deque<CordRep*> flats; + flats.push_front(MakeHexFlat(0)); + auto* leaf = CordRepBtree::Create(flats.front()); + + for (size_t i = 1; i < CordRepBtree::kMaxCapacity; ++i) { + refs.RefIf(shared(), leaf); + flats.push_front(MakeHexFlat(i)); + auto* result = CordRepBtree::Prepend(leaf, flats.front()); + EXPECT_THAT(result->height(), Eq(0)); + EXPECT_THAT(result, Conditional(shared(), Ne(leaf), Eq(leaf))); + EXPECT_THAT(result->Edges(), ElementsAreArray(flats)); + leaf = result; + } + CordRep::Unref(leaf); +} + +// This test specifically aims at code aligning data at either the front or the +// back of the contained `edges[]` array, alternating Append and Prepend will +// move `begin()` and `end()` values as needed for each added value. +TEST_P(CordRepBtreeTest, AppendPrependToLeafToCapacity) { + AutoUnref refs; + std::deque<CordRep*> flats; + flats.push_front(MakeHexFlat(0)); + auto* leaf = CordRepBtree::Create(flats.front()); + + for (size_t i = 1; i < CordRepBtree::kMaxCapacity; ++i) { + refs.RefIf(shared(), leaf); + CordRepBtree* result; + if (i % 2 != 0) { + flats.push_front(MakeHexFlat(i)); + result = CordRepBtree::Prepend(leaf, flats.front()); + } else { + flats.push_back(MakeHexFlat(i)); + result = CordRepBtree::Append(leaf, flats.back()); + } + EXPECT_THAT(result->height(), Eq(0)); + EXPECT_THAT(result, Conditional(shared(), Ne(leaf), Eq(leaf))); + EXPECT_THAT(result->Edges(), ElementsAreArray(flats)); + leaf = result; + } + CordRep::Unref(leaf); +} + +TEST_P(CordRepBtreeTest, AppendToLeafBeyondCapacity) { + AutoUnref refs; + auto* leaf = MakeLeaf(); + refs.RefIf(shared(), leaf); + CordRep* flat = MakeFlat("abc"); + auto* result = CordRepBtree::Append(leaf, flat); + ASSERT_THAT(result, IsNode(1)); + EXPECT_THAT(result, Ne(leaf)); + absl::Span<CordRep* const> edges = result->Edges(); + ASSERT_THAT(edges, ElementsAre(leaf, IsNode(0))); + EXPECT_THAT(edges[1]->btree()->Edges(), ElementsAre(flat)); + CordRep::Unref(result); +} + +TEST_P(CordRepBtreeTest, PrependToLeafBeyondCapacity) { + AutoUnref refs; + auto* leaf = MakeLeaf(); + refs.RefIf(shared(), leaf); + CordRep* flat = MakeFlat("abc"); + auto* result = CordRepBtree::Prepend(leaf, flat); + ASSERT_THAT(result, IsNode(1)); + EXPECT_THAT(result, Ne(leaf)); + absl::Span<CordRep* const> edges = result->Edges(); + ASSERT_THAT(edges, ElementsAre(IsNode(0), leaf)); + EXPECT_THAT(edges[0]->btree()->Edges(), ElementsAre(flat)); + CordRep::Unref(result); +} + +TEST_P(CordRepBtreeTest, AppendToTreeOneDeep) { + constexpr size_t max_cap = CordRepBtree::kMaxCapacity; + AutoUnref refs; + std::vector<CordRep*> flats; + flats.push_back(MakeHexFlat(0)); + CordRepBtree* tree = CordRepBtree::Create(flats.back()); + for (size_t i = 1; i <= max_cap; ++i) { + flats.push_back(MakeHexFlat(i)); + tree = CordRepBtree::Append(tree, flats.back()); + } + ASSERT_THAT(tree, IsNode(1)); + + for (size_t i = max_cap + 1; i < max_cap * max_cap; ++i) { + // Ref top level tree based on param. + // Ref leaf node once every 4 iterations, which should not have an + // observable effect other than that the leaf itself is copied. + refs.RefIf(shared(), tree); + refs.RefIf(i % 4 == 0, tree->Edges().back()); + + flats.push_back(MakeHexFlat(i)); + CordRepBtree* result = CordRepBtree::Append(tree, flats.back()); + ASSERT_THAT(result, IsNode(1)); + ASSERT_THAT(result, Conditional(shared(), Ne(tree), Eq(tree))); + std::vector<CordRep*> edges = GetLeafEdges(result); + ASSERT_THAT(edges, ElementsAreArray(flats)); + tree = result; + } + CordRep::Unref(tree); +} + +TEST_P(CordRepBtreeTest, AppendToTreeTwoDeep) { + constexpr size_t max_cap = CordRepBtree::kMaxCapacity; + AutoUnref refs; + std::vector<CordRep*> flats; + flats.push_back(MakeHexFlat(0)); + CordRepBtree* tree = CordRepBtree::Create(flats.back()); + for (size_t i = 1; i <= max_cap * max_cap; ++i) { + flats.push_back(MakeHexFlat(i)); + tree = CordRepBtree::Append(tree, flats.back()); + } + ASSERT_THAT(tree, IsNode(2)); + for (size_t i = max_cap * max_cap + 1; i < max_cap * max_cap * max_cap; ++i) { + // Ref top level tree based on param. + // Ref child node once every 16 iterations, and leaf node every 4 + // iterrations which which should not have an observable effect other than + // the node and/or the leaf below it being copied. + refs.RefIf(shared(), tree); + refs.RefIf(i % 16 == 0, tree->Edges().back()); + refs.RefIf(i % 4 == 0, tree->Edges().back()->btree()->Edges().back()); + + flats.push_back(MakeHexFlat(i)); + CordRepBtree* result = CordRepBtree::Append(tree, flats.back()); + ASSERT_THAT(result, IsNode(2)); + ASSERT_THAT(result, Conditional(shared(), Ne(tree), Eq(tree))); + std::vector<CordRep*> edges = GetLeafEdges(result); + ASSERT_THAT(edges, ElementsAreArray(flats)); + tree = result; + } + CordRep::Unref(tree); +} + +TEST_P(CordRepBtreeTest, PrependToTreeOneDeep) { + constexpr size_t max_cap = CordRepBtree::kMaxCapacity; + AutoUnref refs; + std::deque<CordRep*> flats; + flats.push_back(MakeHexFlat(0)); + CordRepBtree* tree = CordRepBtree::Create(flats.back()); + for (size_t i = 1; i <= max_cap; ++i) { + flats.push_front(MakeHexFlat(i)); + tree = CordRepBtree::Prepend(tree, flats.front()); + } + ASSERT_THAT(tree, IsNode(1)); + + for (size_t i = max_cap + 1; i < max_cap * max_cap; ++i) { + // Ref top level tree based on param. + // Ref leaf node once every 4 iterations which should not have an observable + // effect other than than the leaf itself is copied. + refs.RefIf(shared(), tree); + refs.RefIf(i % 4 == 0, tree->Edges().back()); + + flats.push_front(MakeHexFlat(i)); + CordRepBtree* result = CordRepBtree::Prepend(tree, flats.front()); + ASSERT_THAT(result, IsNode(1)); + ASSERT_THAT(result, Conditional(shared(), Ne(tree), Eq(tree))); + std::vector<CordRep*> edges = GetLeafEdges(result); + ASSERT_THAT(edges, ElementsAreArray(flats)); + tree = result; + } + CordRep::Unref(tree); +} + +TEST_P(CordRepBtreeTest, PrependToTreeTwoDeep) { + constexpr size_t max_cap = CordRepBtree::kMaxCapacity; + AutoUnref refs; + std::deque<CordRep*> flats; + flats.push_back(MakeHexFlat(0)); + CordRepBtree* tree = CordRepBtree::Create(flats.back()); + for (size_t i = 1; i <= max_cap * max_cap; ++i) { + flats.push_front(MakeHexFlat(i)); + tree = CordRepBtree::Prepend(tree, flats.front()); + } + ASSERT_THAT(tree, IsNode(2)); + for (size_t i = max_cap * max_cap + 1; i < max_cap * max_cap * max_cap; ++i) { + // Ref top level tree based on param. + // Ref child node once every 16 iterations, and leaf node every 4 + // iterrations which which should not have an observable effect other than + // the node and/or the leaf below it being copied. + refs.RefIf(shared(), tree); + refs.RefIf(i % 16 == 0, tree->Edges().back()); + refs.RefIf(i % 4 == 0, tree->Edges().back()->btree()->Edges().back()); + + flats.push_front(MakeHexFlat(i)); + CordRepBtree* result = CordRepBtree::Prepend(tree, flats.front()); + ASSERT_THAT(result, IsNode(2)); + ASSERT_THAT(result, Conditional(shared(), Ne(tree), Eq(tree))); + std::vector<CordRep*> edges = GetLeafEdges(result); + ASSERT_THAT(edges, ElementsAreArray(flats)); + tree = result; + } + CordRep::Unref(tree); +} + +TEST_P(CordRepBtreeDualTest, MergeLeafsNotExceedingCapacity) { + for (bool use_append : {false, true}) { + SCOPED_TRACE(use_append ? "Using Append" : "Using Prepend"); + + AutoUnref refs; + std::vector<CordRep*> flats; + + // Build `left` side leaf appending all contained flats to `flats` + CordRepBtree* left = MakeLeaf(3); + GetLeafEdges(left, flats); + refs.RefIf(first_shared(), left); + + // Build `right` side leaf appending all contained flats to `flats` + CordRepBtree* right = MakeLeaf(2); + GetLeafEdges(right, flats); + refs.RefIf(second_shared(), right); + + CordRepBtree* tree = use_append ? CordRepBtree::Append(left, right) + : CordRepBtree::Prepend(right, left); + EXPECT_THAT(tree, IsNode(0)); + + // `tree` contains all flats originally belonging to `left` and `right`. + EXPECT_THAT(tree->Edges(), ElementsAreArray(flats)); + CordRepBtree::Unref(tree); + } +} + +TEST_P(CordRepBtreeDualTest, MergeLeafsExceedingCapacity) { + for (bool use_append : {false, true}) { + SCOPED_TRACE(use_append ? "Using Append" : "Using Prepend"); + + AutoUnref refs; + + // Build `left` side tree appending all contained flats to `flats` + CordRepBtree* left = MakeLeaf(CordRepBtree::kMaxCapacity - 2); + refs.RefIf(first_shared(), left); + + // Build `right` side tree appending all contained flats to `flats` + CordRepBtree* right = MakeLeaf(CordRepBtree::kMaxCapacity - 1); + refs.RefIf(second_shared(), right); + + CordRepBtree* tree = use_append ? CordRepBtree::Append(left, right) + : CordRepBtree::Prepend(right, left); + EXPECT_THAT(tree, IsNode(1)); + EXPECT_THAT(tree->Edges(), ElementsAre(left, right)); + CordRepBtree::Unref(tree); + } +} + +TEST_P(CordRepBtreeDualTest, MergeEqualHeightTrees) { + for (bool use_append : {false, true}) { + SCOPED_TRACE(use_append ? "Using Append" : "Using Prepend"); + + AutoUnref refs; + std::vector<CordRep*> flats; + + // Build `left` side tree appending all contained flats to `flats` + CordRepBtree* left = MakeTree(CordRepBtree::kMaxCapacity * 3); + GetLeafEdges(left, flats); + refs.RefIf(first_shared(), left); + + // Build `right` side tree appending all contained flats to `flats` + CordRepBtree* right = MakeTree(CordRepBtree::kMaxCapacity * 2); + GetLeafEdges(right, flats); + refs.RefIf(second_shared(), right); + + CordRepBtree* tree = use_append ? CordRepBtree::Append(left, right) + : CordRepBtree::Prepend(right, left); + EXPECT_THAT(tree, IsNode(1)); + EXPECT_THAT(tree->Edges(), SizeIs(5)); + + // `tree` contains all flats originally belonging to `left` and `right`. + EXPECT_THAT(GetLeafEdges(tree), ElementsAreArray(flats)); + CordRepBtree::Unref(tree); + } +} + +TEST_P(CordRepBtreeDualTest, MergeLeafWithTreeNotExceedingLeafCapacity) { + for (bool use_append : {false, true}) { + SCOPED_TRACE(use_append ? "Using Append" : "Using Prepend"); + + AutoUnref refs; + std::vector<CordRep*> flats; + + // Build `left` side tree appending all added flats to `flats` + CordRepBtree* left = MakeTree(CordRepBtree::kMaxCapacity * 2 + 2); + GetLeafEdges(left, flats); + refs.RefIf(first_shared(), left); + + // Build `right` side tree appending all added flats to `flats` + CordRepBtree* right = MakeTree(3); + GetLeafEdges(right, flats); + refs.RefIf(second_shared(), right); + + CordRepBtree* tree = use_append ? CordRepBtree::Append(left, right) + : CordRepBtree::Prepend(right, left); + EXPECT_THAT(tree, IsNode(1)); + EXPECT_THAT(tree->Edges(), SizeIs(3)); + + // `tree` contains all flats originally belonging to `left` and `right`. + EXPECT_THAT(GetLeafEdges(tree), ElementsAreArray(flats)); + CordRepBtree::Unref(tree); + } +} + +TEST_P(CordRepBtreeDualTest, MergeLeafWithTreeExceedingLeafCapacity) { + for (bool use_append : {false, true}) { + SCOPED_TRACE(use_append ? "Using Append" : "Using Prepend"); + + AutoUnref refs; + std::vector<CordRep*> flats; + + // Build `left` side tree appending all added flats to `flats` + CordRepBtree* left = MakeTree(CordRepBtree::kMaxCapacity * 3 - 2); + GetLeafEdges(left, flats); + refs.RefIf(first_shared(), left); + + // Build `right` side tree appending all added flats to `flats` + CordRepBtree* right = MakeTree(3); + GetLeafEdges(right, flats); + refs.RefIf(second_shared(), right); + + CordRepBtree* tree = use_append ? CordRepBtree::Append(left, right) + : CordRepBtree::Prepend(right, left); + EXPECT_THAT(tree, IsNode(1)); + EXPECT_THAT(tree->Edges(), SizeIs(4)); + + // `tree` contains all flats originally belonging to `left` and `right`. + EXPECT_THAT(GetLeafEdges(tree), ElementsAreArray(flats)); + CordRepBtree::Unref(tree); + } +} + +void RefEdgesAt(size_t depth, AutoUnref& refs, CordRepBtree* tree) { + absl::Span<CordRep* const> edges = tree->Edges(); + if (depth == 0) { + refs.Ref(edges.front()); + refs.Ref(edges.back()); + } else { + assert(tree->height() > 0); + RefEdgesAt(depth - 1, refs, edges.front()->btree()); + RefEdgesAt(depth - 1, refs, edges.back()->btree()); + } +} + +TEST(CordRepBtreeTest, MergeFuzzTest) { + constexpr size_t max_cap = CordRepBtree::kMaxCapacity; + std::minstd_rand rnd; + std::uniform_int_distribution<int> coin_flip(0, 1); + std::uniform_int_distribution<int> dice_throw(1, 6); + + auto random_leaf_count = [&]() { + std::uniform_int_distribution<int> dist_height(0, 3); + std::uniform_int_distribution<int> dist_leaf(0, max_cap - 1); + const size_t height = dist_height(rnd); + return (height ? pow(max_cap, height) : 0) + dist_leaf(rnd); + }; + + for (int i = 0; i < 10000; ++i) { + AutoUnref refs; + std::vector<CordRep*> flats; + + CordRepBtree* left = MakeTree(random_leaf_count(), coin_flip(rnd)); + GetLeafEdges(left, flats); + if (dice_throw(rnd) == 1) { + std::uniform_int_distribution<int> dist(0, left->height()); + RefEdgesAt(dist(rnd), refs, left); + } + + CordRepBtree* right = MakeTree(random_leaf_count(), coin_flip(rnd)); + GetLeafEdges(right, flats); + if (dice_throw(rnd) == 1) { + std::uniform_int_distribution<int> dist(0, right->height()); + RefEdgesAt(dist(rnd), refs, right); + } + + CordRepBtree* tree = CordRepBtree::Append(left, right); + EXPECT_THAT(GetLeafEdges(tree), ElementsAreArray(flats)); + CordRepBtree::Unref(tree); + } +} + +TEST(CordRepBtreeTest, SubTree) { + // Create tree of at least 2 levels high + constexpr size_t max_cap = CordRepBtree::kMaxCapacity; + const size_t n = max_cap * max_cap * 2; + const std::string data = CreateRandomString(n * 3); + std::vector<CordRep*> flats; + for (absl::string_view s = data; !s.empty(); s.remove_prefix(3)) { + flats.push_back(MakeFlat(s.substr(0, 3))); + } + CordRepBtree* node = CordRepBtree::Create(CordRep::Ref(flats[0])); + for (size_t i = 1; i < flats.size(); ++i) { + node = CordRepBtree::Append(node, CordRep::Ref(flats[i])); + } + + for (int offset = 0; offset < data.length(); ++offset) { + for (int length = 1; length <= data.length() - offset; ++length) { + CordRep* rep = node->SubTree(offset, length); + EXPECT_THAT(CordToString(rep), Eq(data.substr(offset, length))); + CordRep::Unref(rep); + } + } + CordRepBtree::Unref(node); + for (CordRep* rep : flats) { + CordRep::Unref(rep); + } +} + +TEST(CordRepBtreeTest, SubTreeOnExistingSubstring) { + // This test verifies that a SubTree call on a pre-existing (large) substring + // adjusts the existing substring if not shared, and else rewrites the + // existing substring. + AutoUnref refs; + std::string data = CreateRandomString(1000); + CordRepBtree* leaf = CordRepBtree::Create(MakeFlat("abc")); + CordRep* flat = MakeFlat(data); + leaf = CordRepBtree::Append(leaf, flat); + + // Setup tree containing substring. + CordRep* result = leaf->SubTree(0, 3 + 990); + ASSERT_THAT(result->tag, Eq(BTREE)); + CordRep::Unref(leaf); + leaf = result->btree(); + ASSERT_THAT(leaf->Edges(), ElementsAre(_, IsSubstring(0, 990))); + EXPECT_THAT(leaf->Edges()[1]->substring()->child, Eq(flat)); + + // Verify substring of substring. + result = leaf->SubTree(3 + 5, 970); + ASSERT_THAT(result, IsSubstring(5, 970)); + EXPECT_THAT(result->substring()->child, Eq(flat)); + CordRep::Unref(result); + + CordRep::Unref(leaf); +} + +TEST_P(CordRepBtreeTest, AddDataToLeaf) { + const size_t n = CordRepBtree::kMaxCapacity; + const std::string data = CreateRandomString(n * 3); + + for (bool append : {true, false}) { + AutoUnref refs; + DataConsumer consumer(data, append); + SCOPED_TRACE(append ? "Append" : "Prepend"); + + CordRepBtree* leaf = CordRepBtree::Create(MakeFlat(consumer.Next(3))); + for (size_t i = 1; i < n; ++i) { + refs.RefIf(shared(), leaf); + CordRepBtree* result = BtreeAdd(leaf, append, consumer.Next(3)); + EXPECT_THAT(result, Conditional(shared(), Ne(leaf), Eq(leaf))); + EXPECT_THAT(CordToString(result), Eq(consumer.Consumed())); + leaf = result; + } + CordRep::Unref(leaf); + } +} + +TEST_P(CordRepBtreeTest, AppendDataToTree) { + AutoUnref refs; + size_t n = CordRepBtree::kMaxCapacity + CordRepBtree::kMaxCapacity / 2; + std::string data = CreateRandomString(n * 3); + CordRepBtree* tree = refs.RefIf(shared(), CreateTree(data, 3)); + CordRepBtree* leaf0 = tree->Edges()[0]->btree(); + CordRepBtree* leaf1 = tree->Edges()[1]->btree(); + CordRepBtree* result = CordRepBtree::Append(tree, "123456789"); + EXPECT_THAT(result, Conditional(shared(), Ne(tree), Eq(tree))); + EXPECT_THAT(result->Edges(), + ElementsAre(leaf0, Conditional(shared(), Ne(leaf1), Eq(leaf1)))); + EXPECT_THAT(CordToString(result), Eq(data + "123456789")); + CordRep::Unref(result); +} + +TEST_P(CordRepBtreeTest, PrependDataToTree) { + AutoUnref refs; + size_t n = CordRepBtree::kMaxCapacity + CordRepBtree::kMaxCapacity / 2; + std::string data = CreateRandomString(n * 3); + CordRepBtree* tree = refs.RefIf(shared(), CreateTreeReverse(data, 3)); + CordRepBtree* leaf0 = tree->Edges()[0]->btree(); + CordRepBtree* leaf1 = tree->Edges()[1]->btree(); + CordRepBtree* result = CordRepBtree::Prepend(tree, "123456789"); + EXPECT_THAT(result, Conditional(shared(), Ne(tree), Eq(tree))); + EXPECT_THAT(result->Edges(), + ElementsAre(Conditional(shared(), Ne(leaf0), Eq(leaf0)), leaf1)); + EXPECT_THAT(CordToString(result), Eq("123456789" + data)); + CordRep::Unref(result); +} + +TEST_P(CordRepBtreeTest, AddDataToTreeThreeLevelsDeep) { + constexpr size_t max_cap = CordRepBtree::kMaxCapacity; + const size_t n = max_cap * max_cap * max_cap; + const std::string data = CreateRandomString(n * 3); + + for (bool append : {true, false}) { + AutoUnref refs; + DataConsumer consumer(data, append); + SCOPED_TRACE(append ? "Append" : "Prepend"); + + // Fill leaf + CordRepBtree* tree = CordRepBtree::Create(MakeFlat(consumer.Next(3))); + for (size_t i = 1; i < max_cap; ++i) { + tree = BtreeAdd(tree, append, consumer.Next(3)); + } + ASSERT_THAT(CordToString(tree), Eq(consumer.Consumed())); + + // Fill to maximum at one deep + refs.RefIf(shared(), tree); + CordRepBtree* result = BtreeAdd(tree, append, consumer.Next(3)); + ASSERT_THAT(result, IsNode(1)); + ASSERT_THAT(result, Ne(tree)); + ASSERT_THAT(CordToString(result), Eq(consumer.Consumed())); + tree = result; + for (size_t i = max_cap + 1; i < max_cap * max_cap; ++i) { + refs.RefIf(shared(), tree); + result = BtreeAdd(tree, append, consumer.Next(3)); + ASSERT_THAT(result, Conditional(shared(), Ne(tree), Eq(tree))); + ASSERT_THAT(CordToString(result), Eq(consumer.Consumed())); + tree = result; + } + + // Fill to maximum at two deep + refs.RefIf(shared(), tree); + result = BtreeAdd(tree, append, consumer.Next(3)); + ASSERT_THAT(result, IsNode(2)); + ASSERT_THAT(result, Ne(tree)); + ASSERT_THAT(CordToString(result), Eq(consumer.Consumed())); + tree = result; + for (size_t i = max_cap * max_cap + 1; i < max_cap * max_cap * max_cap; + ++i) { + refs.RefIf(shared(), tree); + result = BtreeAdd(tree, append, consumer.Next(3)); + ASSERT_THAT(result, Conditional(shared(), Ne(tree), Eq(tree))); + ASSERT_THAT(CordToString(result), Eq(consumer.Consumed())); + tree = result; + } + + CordRep::Unref(tree); + } +} + +TEST_P(CordRepBtreeTest, AddLargeDataToLeaf) { + const size_t max_cap = CordRepBtree::kMaxCapacity; + const size_t n = max_cap * max_cap * max_cap * 3 + 2; + const std::string data = CreateRandomString(n * kMaxFlatLength); + + for (bool append : {true, false}) { + AutoUnref refs; + SCOPED_TRACE(append ? "Append" : "Prepend"); + + CordRepBtree* leaf = CordRepBtree::Create(MakeFlat("abc")); + refs.RefIf(shared(), leaf); + CordRepBtree* result = BtreeAdd(leaf, append, data); + EXPECT_THAT(CordToString(result), Eq(append ? "abc" + data : data + "abc")); + CordRep::Unref(result); + } +} + +TEST_P(CordRepBtreeDualTest, CreateFromConcat) { + AutoUnref refs; + CordRep* flats[] = {MakeFlat("abcdefgh"), MakeFlat("ijklm"), + MakeFlat("nopqrstuv"), MakeFlat("wxyz")}; + auto* left = MakeConcat(flats[0], flats[1]); + auto* right = MakeConcat(flats[2], refs.RefIf(first_shared(), flats[3])); + auto* concat = refs.RefIf(second_shared(), MakeConcat(left, right)); + CordRepBtree* result = CordRepBtree::Create(concat); + ASSERT_TRUE(CordRepBtree::IsValid(result)); + EXPECT_THAT(result->length, Eq(26)); + EXPECT_THAT(CordToString(result), Eq("abcdefghijklmnopqrstuvwxyz")); + CordRep::Unref(result); +} + +TEST_P(CordRepBtreeDualTest, AppendConcat) { + AutoUnref refs; + CordRep* flats[] = {MakeFlat("defgh"), MakeFlat("ijklm"), + MakeFlat("nopqrstuv"), MakeFlat("wxyz")}; + auto* left = MakeConcat(flats[0], flats[1]); + auto* right = MakeConcat(flats[2], refs.RefIf(first_shared(), flats[3])); + auto* concat = refs.RefIf(second_shared(), MakeConcat(left, right)); + CordRepBtree* result = CordRepBtree::Create(MakeFlat("abc")); + result = CordRepBtree::Append(result, concat); + ASSERT_TRUE(CordRepBtree::IsValid(result)); + EXPECT_THAT(result->length, Eq(26)); + EXPECT_THAT(CordToString(result), Eq("abcdefghijklmnopqrstuvwxyz")); + CordRep::Unref(result); +} + +TEST_P(CordRepBtreeDualTest, PrependConcat) { + AutoUnref refs; + CordRep* flats[] = {MakeFlat("abcdefgh"), MakeFlat("ijklm"), + MakeFlat("nopqrstuv"), MakeFlat("wx")}; + auto* left = MakeConcat(flats[0], flats[1]); + auto* right = MakeConcat(flats[2], refs.RefIf(first_shared(), flats[3])); + auto* concat = refs.RefIf(second_shared(), MakeConcat(left, right)); + CordRepBtree* result = CordRepBtree::Create(MakeFlat("yz")); + result = CordRepBtree::Prepend(result, concat); + ASSERT_TRUE(CordRepBtree::IsValid(result)); + EXPECT_THAT(result->length, Eq(26)); + EXPECT_THAT(CordToString(result), Eq("abcdefghijklmnopqrstuvwxyz")); + CordRep::Unref(result); +} + +TEST_P(CordRepBtreeTest, CreateFromTreeReturnsTree) { + AutoUnref refs; + CordRepBtree* leaf = CordRepBtree::Create(MakeFlat("Hello world")); + refs.RefIf(shared(), leaf); + CordRepBtree* result = CordRepBtree::Create(leaf); + EXPECT_THAT(result, Eq(leaf)); + CordRep::Unref(result); +} + +TEST_P(CordRepBtreeTest, ExceedMaxHeight) { + AutoUnref refs; + CordRepBtree* tree = MakeLeaf(); + for (int h = 1; h <= CordRepBtree::kMaxHeight; ++h) { + CordRepBtree* newtree = CordRepBtree::New(tree); + for (size_t i = 1; i < CordRepBtree::kMaxCapacity; ++i) { + newtree = CordRepBtree::Append(newtree, CordRep::Ref(tree)); + } + tree = newtree; + } + refs.RefIf(shared(), tree); +#if defined(GTEST_HAS_DEATH_TEST) + EXPECT_DEATH(tree = CordRepBtree::Append(tree, MakeFlat("Boom")), ".*"); +#endif + CordRep::Unref(tree); +} + +TEST(CordRepBtreeTest, GetCharacter) { + size_t n = CordRepBtree::kMaxCapacity * CordRepBtree::kMaxCapacity + 2; + std::string data = CreateRandomString(n * 3); + CordRepBtree* tree = CreateTree(data, 3); + // Add a substring node for good measure. + tree = tree->Append(tree, MakeSubstring(4, 5, MakeFlat("abcdefghijklm"))); + data += "efghi"; + for (size_t i = 0; i < data.length(); ++i) { + ASSERT_THAT(tree->GetCharacter(i), Eq(data[i])); + } + CordRep::Unref(tree); +} + +TEST_P(CordRepBtreeTest, IsFlatSingleFlat) { + CordRepBtree* leaf = CordRepBtree::Create(MakeFlat("Hello world")); + + absl::string_view fragment; + EXPECT_TRUE(leaf->IsFlat(nullptr)); + EXPECT_TRUE(leaf->IsFlat(&fragment)); + EXPECT_THAT(fragment, Eq("Hello world")); + fragment = ""; + EXPECT_TRUE(leaf->IsFlat(0, 11, nullptr)); + EXPECT_TRUE(leaf->IsFlat(0, 11, &fragment)); + EXPECT_THAT(fragment, Eq("Hello world")); + + // Arbitrary ranges must check true as well. + EXPECT_TRUE(leaf->IsFlat(1, 4, &fragment)); + EXPECT_THAT(fragment, Eq("ello")); + EXPECT_TRUE(leaf->IsFlat(6, 5, &fragment)); + EXPECT_THAT(fragment, Eq("world")); + + CordRep::Unref(leaf); +} + +TEST(CordRepBtreeTest, IsFlatMultiFlat) { + size_t n = CordRepBtree::kMaxCapacity * CordRepBtree::kMaxCapacity + 2; + std::string data = CreateRandomString(n * 3); + CordRepBtree* tree = CreateTree(data, 3); + // Add substring nodes for good measure. + tree = tree->Append(tree, MakeSubstring(4, 3, MakeFlat("abcdefghijklm"))); + tree = tree->Append(tree, MakeSubstring(8, 3, MakeFlat("abcdefghijklm"))); + data += "efgijk"; + + EXPECT_FALSE(tree->IsFlat(nullptr)); + absl::string_view fragment = "Can't touch this"; + EXPECT_FALSE(tree->IsFlat(&fragment)); + EXPECT_THAT(fragment, Eq("Can't touch this")); + + for (size_t offset = 0; offset < data.size(); offset += 3) { + EXPECT_TRUE(tree->IsFlat(offset, 3, nullptr)); + EXPECT_TRUE(tree->IsFlat(offset, 3, &fragment)); + EXPECT_THAT(fragment, Eq(data.substr(offset, 3))); + + fragment = "Can't touch this"; + if (offset > 0) { + EXPECT_FALSE(tree->IsFlat(offset - 1, 4, nullptr)); + EXPECT_FALSE(tree->IsFlat(offset - 1, 4, &fragment)); + EXPECT_THAT(fragment, Eq("Can't touch this")); + } + if (offset < data.size() - 4) { + EXPECT_FALSE(tree->IsFlat(offset, 4, nullptr)); + EXPECT_FALSE(tree->IsFlat(offset, 4, &fragment)); + EXPECT_THAT(fragment, Eq("Can't touch this")); + } + } + + CordRep::Unref(tree); +} + +#if defined(GTEST_HAS_DEATH_TEST) && !defined(NDEBUG) + +TEST_P(CordRepBtreeHeightTest, GetAppendBufferNotPrivate) { + CordRepBtree* tree = CordRepBtree::Create(MakeExternal("Foo")); + CordRepBtree::Ref(tree); + EXPECT_DEATH(tree->GetAppendBuffer(1), ".*"); + CordRepBtree::Unref(tree); + CordRepBtree::Unref(tree); +} + +#endif // defined(GTEST_HAS_DEATH_TEST) && !defined(NDEBUG) + +TEST_P(CordRepBtreeHeightTest, GetAppendBufferNotFlat) { + CordRepBtree* tree = CordRepBtree::Create(MakeExternal("Foo")); + for (int i = 1; i <= height(); ++i) { + tree = CordRepBtree::New(tree); + } + EXPECT_THAT(tree->GetAppendBuffer(1), SizeIs(0)); + CordRepBtree::Unref(tree); +} + +TEST_P(CordRepBtreeHeightTest, GetAppendBufferFlatNotPrivate) { + CordRepFlat* flat = MakeFlat("abc"); + CordRepBtree* tree = CordRepBtree::Create(CordRep::Ref(flat)); + for (int i = 1; i <= height(); ++i) { + tree = CordRepBtree::New(tree); + } + EXPECT_THAT(tree->GetAppendBuffer(1), SizeIs(0)); + CordRepBtree::Unref(tree); + CordRep::Unref(flat); +} + +TEST_P(CordRepBtreeHeightTest, GetAppendBufferTreeNotPrivate) { + if (height() == 0) return; + AutoUnref refs; + CordRepFlat* flat = MakeFlat("abc"); + CordRepBtree* tree = CordRepBtree::Create(CordRep::Ref(flat)); + for (int i = 1; i <= height(); ++i) { + if (i == (height() + 1) / 2) refs.Ref(tree); + tree = CordRepBtree::New(tree); + } + EXPECT_THAT(tree->GetAppendBuffer(1), SizeIs(0)); + CordRepBtree::Unref(tree); + CordRep::Unref(flat); +} + +TEST_P(CordRepBtreeHeightTest, GetAppendBufferFlatNoCapacity) { + CordRepFlat* flat = MakeFlat("abc"); + flat->length = flat->Capacity(); + CordRepBtree* tree = CordRepBtree::Create(flat); + for (int i = 1; i <= height(); ++i) { + tree = CordRepBtree::New(tree); + } + EXPECT_THAT(tree->GetAppendBuffer(1), SizeIs(0)); + CordRepBtree::Unref(tree); +} + +TEST_P(CordRepBtreeHeightTest, GetAppendBufferFlatWithCapacity) { + CordRepFlat* flat = MakeFlat("abc"); + CordRepBtree* tree = CordRepBtree::Create(flat); + for (int i = 1; i <= height(); ++i) { + tree = CordRepBtree::New(tree); + } + absl::Span<char> span = tree->GetAppendBuffer(2); + EXPECT_THAT(span, SizeIs(2)); + EXPECT_THAT(span.data(), TypedEq<void*>(flat->Data() + 3)); + EXPECT_THAT(tree->length, Eq(5)); + + size_t avail = flat->Capacity() - 5; + span = tree->GetAppendBuffer(avail + 100); + EXPECT_THAT(span, SizeIs(avail)); + EXPECT_THAT(span.data(), TypedEq<void*>(flat->Data() + 5)); + EXPECT_THAT(tree->length, Eq(5 + avail)); + + CordRepBtree::Unref(tree); +} + +TEST(CordRepBtreeTest, Dump) { + // Handles nullptr + std::stringstream ss; + CordRepBtree::Dump(nullptr, ss); + CordRepBtree::Dump(nullptr, "Once upon a label", ss); + CordRepBtree::Dump(nullptr, "Once upon a label", false, ss); + CordRepBtree::Dump(nullptr, "Once upon a label", true, ss); + + // Cover legal edges + CordRepFlat* flat = MakeFlat("Hello world"); + CordRepExternal* external = MakeExternal("Hello external"); + CordRep* substr_flat = MakeSubstring(1, 6, CordRep::Ref(flat)); + CordRep* substr_external = MakeSubstring(2, 7, CordRep::Ref(external)); + + // Build tree + CordRepBtree* tree = CordRepBtree::Create(flat); + tree = CordRepBtree::Append(tree, external); + tree = CordRepBtree::Append(tree, substr_flat); + tree = CordRepBtree::Append(tree, substr_external); + + // Repeat until we have a tree + while (tree->height() == 0) { + tree = CordRepBtree::Append(tree, CordRep::Ref(flat)); + tree = CordRepBtree::Append(tree, CordRep::Ref(external)); + tree = CordRepBtree::Append(tree, CordRep::Ref(substr_flat)); + tree = CordRepBtree::Append(tree, CordRep::Ref(substr_external)); + } + + for (int api = 0; api <= 3; ++api) { + absl::string_view api_scope; + std::stringstream ss; + switch (api) { + case 0: + api_scope = "Bare"; + CordRepBtree::Dump(tree, ss); + break; + case 1: + api_scope = "Label only"; + CordRepBtree::Dump(tree, "Once upon a label", ss); + break; + case 2: + api_scope = "Label no content"; + CordRepBtree::Dump(tree, "Once upon a label", false, ss); + break; + default: + api_scope = "Label and content"; + CordRepBtree::Dump(tree, "Once upon a label", true, ss); + break; + } + SCOPED_TRACE(api_scope); + std::string str = ss.str(); + + // Contains Node(depth) / Leaf and private / shared indicators + EXPECT_THAT(str, AllOf(HasSubstr("Node(1)"), HasSubstr("Leaf"), + HasSubstr("Private"), HasSubstr("Shared"))); + + // Contains length and start offset of all data edges + EXPECT_THAT(str, AllOf(HasSubstr("len = 11"), HasSubstr("len = 14"), + HasSubstr("len = 6"), HasSubstr("len = 7"), + HasSubstr("start = 1"), HasSubstr("start = 2"))); + + // Contains address of all data edges + EXPECT_THAT( + str, AllOf(HasSubstr(absl::StrCat("0x", absl::Hex(flat))), + HasSubstr(absl::StrCat("0x", absl::Hex(external))), + HasSubstr(absl::StrCat("0x", absl::Hex(substr_flat))), + HasSubstr(absl::StrCat("0x", absl::Hex(substr_external))))); + + if (api != 0) { + // Contains label + EXPECT_THAT(str, HasSubstr("Once upon a label")); + } + + if (api != 3) { + // Does not contain contents + EXPECT_THAT(str, Not(AnyOf((HasSubstr("data = \"Hello world\""), + HasSubstr("data = \"Hello external\""), + HasSubstr("data = \"ello w\""), + HasSubstr("data = \"llo ext\""))))); + } else { + // Contains contents + EXPECT_THAT(str, AllOf((HasSubstr("data = \"Hello world\""), + HasSubstr("data = \"Hello external\""), + HasSubstr("data = \"ello w\""), + HasSubstr("data = \"llo ext\"")))); + } + } + + CordRep::Unref(tree); +} + +TEST(CordRepBtreeTest, IsValid) { + EXPECT_FALSE(CordRepBtree::IsValid(nullptr)); + + CordRepBtree* empty = CordRepBtree::New(0); + EXPECT_TRUE(CordRepBtree::IsValid(empty)); + CordRep::Unref(empty); + + for (bool as_tree : {false, true}) { + CordRepBtree* leaf = CordRepBtree::Create(MakeFlat("abc")); + CordRepBtree* tree = as_tree ? CordRepBtree::New(leaf) : nullptr; + CordRepBtree* check = as_tree ? tree : leaf; + + ASSERT_TRUE(CordRepBtree::IsValid(check)); + leaf->length--; + EXPECT_FALSE(CordRepBtree::IsValid(check)); + leaf->length++; + + ASSERT_TRUE(CordRepBtree::IsValid(check)); + leaf->tag--; + EXPECT_FALSE(CordRepBtree::IsValid(check)); + leaf->tag++; + + // Height + ASSERT_TRUE(CordRepBtree::IsValid(check)); + leaf->storage[0] = static_cast<uint8_t>(CordRepBtree::kMaxHeight + 1); + EXPECT_FALSE(CordRepBtree::IsValid(check)); + leaf->storage[0] = 1; + EXPECT_FALSE(CordRepBtree::IsValid(check)); + leaf->storage[0] = 0; + + // Begin + ASSERT_TRUE(CordRepBtree::IsValid(check)); + const uint8_t begin = leaf->storage[1]; + leaf->storage[1] = static_cast<uint8_t>(CordRepBtree::kMaxCapacity); + EXPECT_FALSE(CordRepBtree::IsValid(check)); + leaf->storage[1] = 2; + EXPECT_FALSE(CordRepBtree::IsValid(check)); + leaf->storage[1] = begin; + + // End + ASSERT_TRUE(CordRepBtree::IsValid(check)); + const uint8_t end = leaf->storage[2]; + leaf->storage[2] = static_cast<uint8_t>(CordRepBtree::kMaxCapacity + 1); + EXPECT_FALSE(CordRepBtree::IsValid(check)); + leaf->storage[2] = end; + + // DataEdge tag and value + ASSERT_TRUE(CordRepBtree::IsValid(check)); + CordRep* const edge = leaf->Edges()[0]; + const uint8_t tag = edge->tag; + CordRepBtreeTestPeer::SetEdge(leaf, begin, nullptr); + EXPECT_FALSE(CordRepBtree::IsValid(check)); + CordRepBtreeTestPeer::SetEdge(leaf, begin, edge); + edge->tag = BTREE; + EXPECT_FALSE(CordRepBtree::IsValid(check)); + edge->tag = tag; + + if (as_tree) { + ASSERT_TRUE(CordRepBtree::IsValid(check)); + leaf->length--; + EXPECT_FALSE(CordRepBtree::IsValid(check)); + leaf->length++; + + // Height + ASSERT_TRUE(CordRepBtree::IsValid(check)); + tree->storage[0] = static_cast<uint8_t>(2); + EXPECT_FALSE(CordRepBtree::IsValid(check)); + tree->storage[0] = 1; + + // Btree edge + ASSERT_TRUE(CordRepBtree::IsValid(check)); + CordRep* const edge = tree->Edges()[0]; + const uint8_t tag = edge->tag; + edge->tag = FLAT; + EXPECT_FALSE(CordRepBtree::IsValid(check)); + edge->tag = tag; + } + + ASSERT_TRUE(CordRepBtree::IsValid(check)); + CordRep::Unref(check); + } +} + +TEST(CordRepBtreeTest, AssertValid) { + CordRepBtree* tree = CordRepBtree::Create(MakeFlat("abc")); + const CordRepBtree* ctree = tree; + EXPECT_THAT(CordRepBtree::AssertValid(tree), Eq(tree)); + EXPECT_THAT(CordRepBtree::AssertValid(ctree), Eq(ctree)); + +#if defined(GTEST_HAS_DEATH_TEST) + CordRepBtree* nulltree = nullptr; + const CordRepBtree* cnulltree = nullptr; + EXPECT_DEBUG_DEATH( + EXPECT_THAT(CordRepBtree::AssertValid(nulltree), Eq(nulltree)), ".*"); + EXPECT_DEBUG_DEATH( + EXPECT_THAT(CordRepBtree::AssertValid(cnulltree), Eq(cnulltree)), ".*"); + + tree->length--; + EXPECT_DEBUG_DEATH(EXPECT_THAT(CordRepBtree::AssertValid(tree), Eq(tree)), + ".*"); + EXPECT_DEBUG_DEATH(EXPECT_THAT(CordRepBtree::AssertValid(ctree), Eq(ctree)), + ".*"); + tree->length++; +#endif + CordRep::Unref(tree); +} + +} // namespace +} // namespace cord_internal +ABSL_NAMESPACE_END +} // namespace absl diff --git a/absl/strings/internal/cord_rep_test_util.h b/absl/strings/internal/cord_rep_test_util.h new file mode 100644 index 00000000..bc500064 --- /dev/null +++ b/absl/strings/internal/cord_rep_test_util.h @@ -0,0 +1,185 @@ +// Copyright 2021 The Abseil Authors +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#ifndef ABSL_STRINGS_INTERNAL_CORD_REP_TEST_UTIL_H_ +#define ABSL_STRINGS_INTERNAL_CORD_REP_TEST_UTIL_H_ + +#include <cassert> +#include <memory> +#include <random> +#include <string> +#include <vector> + +#include "absl/base/config.h" +#include "absl/base/internal/raw_logging.h" +#include "absl/strings/internal/cord_internal.h" +#include "absl/strings/internal/cord_rep_btree.h" +#include "absl/strings/internal/cord_rep_flat.h" +#include "absl/strings/string_view.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace cordrep_testing { + +inline cord_internal::CordRepSubstring* MakeSubstring( + size_t start, size_t len, cord_internal::CordRep* rep) { + auto* sub = new cord_internal::CordRepSubstring; + sub->tag = cord_internal::SUBSTRING; + sub->start = start; + sub->length = len <= 0 ? rep->length - start + len : len; + sub->child = rep; + return sub; +} + +inline cord_internal::CordRepConcat* MakeConcat(cord_internal::CordRep* left, + cord_internal::CordRep* right, + int depth = 0) { + auto* concat = new cord_internal::CordRepConcat; + concat->tag = cord_internal::CONCAT; + concat->length = left->length + right->length; + concat->left = left; + concat->right = right; + concat->set_depth(depth); + return concat; +} + +inline cord_internal::CordRepFlat* MakeFlat(absl::string_view value) { + assert(value.length() <= cord_internal::kMaxFlatLength); + auto* flat = cord_internal::CordRepFlat::New(value.length()); + flat->length = value.length(); + memcpy(flat->Data(), value.data(), value.length()); + return flat; +} + +// Creates an external node for testing +inline cord_internal::CordRepExternal* MakeExternal(absl::string_view s) { + struct Rep : public cord_internal::CordRepExternal { + std::string s; + explicit Rep(absl::string_view sv) : s(sv) { + this->tag = cord_internal::EXTERNAL; + this->base = s.data(); + this->length = s.length(); + this->releaser_invoker = [](cord_internal::CordRepExternal* self) { + delete static_cast<Rep*>(self); + }; + } + }; + return new Rep(s); +} + +inline std::string CreateRandomString(size_t n) { + absl::string_view data = + "abcdefghijklmnopqrstuvwxyz" + "ABCDEFGHIJKLMNOPQRSTUVWXYZ" + "0123456789~!@#$%^&*()_+=-<>?:\"{}[]|"; + std::minstd_rand rnd; + std::uniform_int_distribution<size_t> dist(0, data.size() - 1); + std::string s(n, ' '); + for (size_t i = 0; i < n; ++i) { + s[i] = data[dist(rnd)]; + } + return s; +} + +// Creates an array of flats from the provided string, chopping +// the provided string up into flats of size `chunk_size` characters +// resulting in roughly `data.size() / chunk_size` total flats. +inline std::vector<cord_internal::CordRep*> CreateFlatsFromString( + absl::string_view data, size_t chunk_size) { + assert(chunk_size > 0); + std::vector<cord_internal::CordRep*> flats; + for (absl::string_view s = data; !s.empty(); s.remove_prefix(chunk_size)) { + flats.push_back(MakeFlat(s.substr(0, chunk_size))); + } + return flats; +} + +inline cord_internal::CordRepBtree* CordRepBtreeFromFlats( + absl::Span<cord_internal::CordRep* const> flats) { + assert(!flats.empty()); + auto* node = cord_internal::CordRepBtree::Create(flats[0]); + for (size_t i = 1; i < flats.size(); ++i) { + node = cord_internal::CordRepBtree::Append(node, flats[i]); + } + return node; +} + +inline void CordToString(cord_internal::CordRep* rep, std::string& s) { + size_t offset = 0; + size_t length = rep->length; + while (rep->tag == cord_internal::SUBSTRING) { + offset += rep->substring()->start; + rep = rep->substring()->child; + } + if (rep->tag == cord_internal::BTREE) { + for (cord_internal::CordRep* edge : rep->btree()->Edges()) { + CordToString(edge, s); + } + } else if (rep->tag >= cord_internal::FLAT) { + s.append(rep->flat()->Data() + offset, length); + } else if (rep->tag == cord_internal::EXTERNAL) { + s.append(rep->external()->base + offset, length); + } else { + ABSL_RAW_LOG(FATAL, "Unsupported tag %d", rep->tag); + } +} + +inline std::string CordToString(cord_internal::CordRep* rep) { + std::string s; + s.reserve(rep->length); + CordToString(rep, s); + return s; +} + +// RAII Helper class to automatically unref reps on destruction. +class AutoUnref { + public: + ~AutoUnref() { + for (CordRep* rep : unrefs_) CordRep::Unref(rep); + } + + // Adds `rep` to the list of reps to be unreffed at destruction. + template <typename CordRepType> + CordRepType* Add(CordRepType* rep) { + unrefs_.push_back(rep); + return rep; + } + + // Increments the reference count of `rep` by one, and adds it to + // the list of reps to be unreffed at destruction. + template <typename CordRepType> + CordRepType* Ref(CordRepType* rep) { + unrefs_.push_back(CordRep::Ref(rep)); + return rep; + } + + // Increments the reference count of `rep` by one if `condition` is true, + // and adds it to the list of reps to be unreffed at destruction. + template <typename CordRepType> + CordRepType* RefIf(bool condition, CordRepType* rep) { + if (condition) unrefs_.push_back(CordRep::Ref(rep)); + return rep; + } + + private: + using CordRep = absl::cord_internal::CordRep; + + std::vector<CordRep*> unrefs_; +}; + +} // namespace cordrep_testing +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_STRINGS_INTERNAL_CORD_REP_TEST_UTIL_H_ |