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authorGravatar Abseil Team <absl-team@google.com>2020-04-06 20:53:47 -0700
committerGravatar Gennadiy Rozental <rogeeff@google.com>2020-04-07 00:10:49 -0400
commit73ea9a95720c4f4faff9b1bcbad48d23f2cb2a46 (patch)
tree97596c4ce8c4a0df539826ea021a870ffe93e065 /absl/strings
parentc01b9916e705dc067d4e3d219ef60b49277353bd (diff)
Export of internal Abseil changes
-- 87cdfd6aa40941e116cd79ef70f9a7a8271db163 by Abseil Team <absl-team@google.com>: Fix a typo in random.h API documentation. PiperOrigin-RevId: 305176308 -- 8a38e1df49a18a954daca3ce617fd69045ff4c19 by Derek Mauro <dmauro@google.com>: Import GitHub #647: Allow external add_subdirectory for using GoogleTest PiperOrigin-RevId: 305156797 -- b1a2441536d4964fbe4e2329e74c322e6c41a4e6 by Gennadiy Rozental <rogeeff@google.com>: temporary roll back. PiperOrigin-RevId: 305149619 -- c78767577264348d2f881893f9407aadfe73ab75 by CJ Johnson <johnsoncj@google.com>: Rollback update to linux_clang-latest container while investigating a compiler bug. PiperOrigin-RevId: 304897689 -- 3c6fd38f53d2e982569fdba4043f75271c7b5de4 by Derek Mauro <dmauro@google.com>: Update linux_clang-latest container to one based on Ubuntu 18.04, which has libstdc++-8. PiperOrigin-RevId: 304885120 GitOrigin-RevId: 87cdfd6aa40941e116cd79ef70f9a7a8271db163 Change-Id: Iefa6efee93907ec0eecb8add804c5cc2f052b64d
Diffstat (limited to 'absl/strings')
-rw-r--r--absl/strings/cord.cc248
-rw-r--r--absl/strings/cord.h232
-rw-r--r--absl/strings/cord_test.cc47
3 files changed, 174 insertions, 353 deletions
diff --git a/absl/strings/cord.cc b/absl/strings/cord.cc
index 7de7766c..fa490c18 100644
--- a/absl/strings/cord.cc
+++ b/absl/strings/cord.cc
@@ -31,6 +31,7 @@
#include "absl/base/macros.h"
#include "absl/base/port.h"
#include "absl/container/fixed_array.h"
+#include "absl/container/inlined_vector.h"
#include "absl/strings/escaping.h"
#include "absl/strings/internal/cord_internal.h"
#include "absl/strings/internal/resize_uninitialized.h"
@@ -132,14 +133,6 @@ inline const CordRepExternal* CordRep::external() const {
return static_cast<const CordRepExternal*>(this);
}
-using CordTreeConstPath = CordTreePath<const CordRep*, MaxCordDepth()>;
-
-// This type is used to store the list of pending nodes during re-balancing.
-// Its maximum size is 2 * MaxCordDepth() because the tree has a maximum
-// possible depth of MaxCordDepth() and every concat node along a tree path
-// could theoretically be split during rebalancing.
-using RebalancingStack = CordTreePath<CordRep*, 2 * MaxCordDepth()>;
-
} // namespace cord_internal
static const size_t kFlatOverhead = offsetof(CordRep, data);
@@ -188,78 +181,64 @@ static constexpr size_t TagToLength(uint8_t tag) {
// Enforce that kMaxFlatSize maps to a well-known exact tag value.
static_assert(TagToAllocatedSize(224) == kMaxFlatSize, "Bad tag logic");
-constexpr size_t Fibonacci(uint8_t n, const size_t a = 0, const size_t b = 1) {
- return n == 0
- ? a
- : n == 1 ? b
- : Fibonacci(n - 1, b,
- (a > (size_t(-1) - b)) ? size_t(-1) : a + b);
+constexpr uint64_t Fibonacci(unsigned char n, uint64_t a = 0, uint64_t b = 1) {
+ return n == 0 ? a : Fibonacci(n - 1, b, a + b);
}
+static_assert(Fibonacci(63) == 6557470319842,
+ "Fibonacci values computed incorrectly");
+
// Minimum length required for a given depth tree -- a tree is considered
// balanced if
-// length(t) >= kMinLength[depth(t)]
-// The node depth is allowed to become larger to reduce rebalancing
-// for larger strings (see ShouldRebalance).
-constexpr size_t kMinLength[] = {
- Fibonacci(2), Fibonacci(3), Fibonacci(4), Fibonacci(5), Fibonacci(6),
- Fibonacci(7), Fibonacci(8), Fibonacci(9), Fibonacci(10), Fibonacci(11),
- Fibonacci(12), Fibonacci(13), Fibonacci(14), Fibonacci(15), Fibonacci(16),
- Fibonacci(17), Fibonacci(18), Fibonacci(19), Fibonacci(20), Fibonacci(21),
- Fibonacci(22), Fibonacci(23), Fibonacci(24), Fibonacci(25), Fibonacci(26),
- Fibonacci(27), Fibonacci(28), Fibonacci(29), Fibonacci(30), Fibonacci(31),
- Fibonacci(32), Fibonacci(33), Fibonacci(34), Fibonacci(35), Fibonacci(36),
- Fibonacci(37), Fibonacci(38), Fibonacci(39), Fibonacci(40), Fibonacci(41),
- Fibonacci(42), Fibonacci(43), Fibonacci(44), Fibonacci(45), Fibonacci(46),
- Fibonacci(47), Fibonacci(48), Fibonacci(49), Fibonacci(50), Fibonacci(51),
- Fibonacci(52), Fibonacci(53), Fibonacci(54), Fibonacci(55), Fibonacci(56),
- Fibonacci(57), Fibonacci(58), Fibonacci(59), Fibonacci(60), Fibonacci(61),
- Fibonacci(62), Fibonacci(63), Fibonacci(64), Fibonacci(65), Fibonacci(66),
- Fibonacci(67), Fibonacci(68), Fibonacci(69), Fibonacci(70), Fibonacci(71),
- Fibonacci(72), Fibonacci(73), Fibonacci(74), Fibonacci(75), Fibonacci(76),
- Fibonacci(77), Fibonacci(78), Fibonacci(79), Fibonacci(80), Fibonacci(81),
- Fibonacci(82), Fibonacci(83), Fibonacci(84), Fibonacci(85), Fibonacci(86),
- Fibonacci(87), Fibonacci(88), Fibonacci(89), Fibonacci(90), Fibonacci(91),
- Fibonacci(92), Fibonacci(93), Fibonacci(94), Fibonacci(95)};
-
-static_assert(sizeof(kMinLength) / sizeof(size_t) >=
- (cord_internal::MaxCordDepth() + 1),
- "Not enough elements in kMinLength array to cover all the "
- "supported Cord depth(s)");
-
-inline bool ShouldRebalance(const CordRep* node) {
- if (node->tag != CONCAT) return false;
-
- size_t node_depth = node->concat()->depth();
-
- if (node_depth <= 15) return false;
-
- // Rebalancing Cords is expensive, so we reduce how often rebalancing occurs
- // by allowing shallow Cords to have twice the depth that the Fibonacci rule
- // would otherwise imply. Deep Cords need to follow the rule more closely,
- // however to ensure algorithm correctness. We implement this with linear
- // interpolation. Cords of depth 16 are treated as though they have a depth
- // of 16 * 1/2, and Cords of depth MaxCordDepth() interpolate to
- // MaxCordDepth() * 1.
- return node->length <
- kMinLength[(node_depth * (cord_internal::MaxCordDepth() - 16)) /
- (2 * cord_internal::MaxCordDepth() - 16 - node_depth)];
-}
-
-// Unlike root balancing condition this one is part of the re-balancing
-// algorithm and has to be always matching against right depth for
-// algorithm to be correct.
-inline bool IsNodeBalanced(const CordRep* node) {
- if (node->tag != CONCAT) return true;
-
- size_t node_depth = node->concat()->depth();
-
- return node->length >= kMinLength[node_depth];
+// length(t) >= min_length[depth(t)]
+// The root node depth is allowed to become twice as large to reduce rebalancing
+// for larger strings (see IsRootBalanced).
+static constexpr uint64_t min_length[] = {
+ Fibonacci(2), Fibonacci(3), Fibonacci(4), Fibonacci(5),
+ Fibonacci(6), Fibonacci(7), Fibonacci(8), Fibonacci(9),
+ Fibonacci(10), Fibonacci(11), Fibonacci(12), Fibonacci(13),
+ Fibonacci(14), Fibonacci(15), Fibonacci(16), Fibonacci(17),
+ Fibonacci(18), Fibonacci(19), Fibonacci(20), Fibonacci(21),
+ Fibonacci(22), Fibonacci(23), Fibonacci(24), Fibonacci(25),
+ Fibonacci(26), Fibonacci(27), Fibonacci(28), Fibonacci(29),
+ Fibonacci(30), Fibonacci(31), Fibonacci(32), Fibonacci(33),
+ Fibonacci(34), Fibonacci(35), Fibonacci(36), Fibonacci(37),
+ Fibonacci(38), Fibonacci(39), Fibonacci(40), Fibonacci(41),
+ Fibonacci(42), Fibonacci(43), Fibonacci(44), Fibonacci(45),
+ Fibonacci(46), Fibonacci(47),
+ 0xffffffffffffffffull, // Avoid overflow
+};
+
+static const int kMinLengthSize = ABSL_ARRAYSIZE(min_length);
+
+// The inlined size to use with absl::InlinedVector.
+//
+// Note: The InlinedVectors in this file (and in cord.h) do not need to use
+// the same value for their inlined size. The fact that they do is historical.
+// It may be desirable for each to use a different inlined size optimized for
+// that InlinedVector's usage.
+//
+// TODO(jgm): Benchmark to see if there's a more optimal value than 47 for
+// the inlined vector size (47 exists for backward compatibility).
+static const int kInlinedVectorSize = 47;
+
+static inline bool IsRootBalanced(CordRep* node) {
+ if (node->tag != CONCAT) {
+ return true;
+ } else if (node->concat()->depth() <= 15) {
+ return true;
+ } else if (node->concat()->depth() > kMinLengthSize) {
+ return false;
+ } else {
+ // Allow depth to become twice as large as implied by fibonacci rule to
+ // reduce rebalancing for larger strings.
+ return (node->length >= min_length[node->concat()->depth() / 2]);
+ }
}
static CordRep* Rebalance(CordRep* node);
-static void DumpNode(const CordRep* rep, bool include_data, std::ostream* os);
-static bool VerifyNode(const CordRep* root, const CordRep* start_node,
+static void DumpNode(CordRep* rep, bool include_data, std::ostream* os);
+static bool VerifyNode(CordRep* root, CordRep* start_node,
bool full_validation);
static inline CordRep* VerifyTree(CordRep* node) {
@@ -306,8 +285,7 @@ __attribute__((preserve_most))
static void UnrefInternal(CordRep* rep) {
assert(rep != nullptr);
- cord_internal::RebalancingStack pending;
-
+ absl::InlinedVector<CordRep*, kInlinedVectorSize> pending;
while (true) {
if (rep->tag == CONCAT) {
CordRepConcat* rep_concat = rep->concat();
@@ -389,11 +367,6 @@ static void SetConcatChildren(CordRepConcat* concat, CordRep* left,
concat->length = left->length + right->length;
concat->set_depth(1 + std::max(Depth(left), Depth(right)));
-
- ABSL_INTERNAL_CHECK(concat->depth() <= cord_internal::MaxCordDepth(),
- "Cord depth exceeds max");
- ABSL_INTERNAL_CHECK(concat->length >= left->length, "Cord is too long");
- ABSL_INTERNAL_CHECK(concat->length >= right->length, "Cord is too long");
}
// Create a concatenation of the specified nodes.
@@ -419,7 +392,7 @@ static CordRep* RawConcat(CordRep* left, CordRep* right) {
static CordRep* Concat(CordRep* left, CordRep* right) {
CordRep* rep = RawConcat(left, right);
- if (rep != nullptr && ShouldRebalance(rep)) {
+ if (rep != nullptr && !IsRootBalanced(rep)) {
rep = Rebalance(rep);
}
return VerifyTree(rep);
@@ -714,14 +687,6 @@ void Cord::InlineRep::ClearSlow() {
memset(data_, 0, sizeof(data_));
}
-inline Cord::InternalChunkIterator Cord::internal_chunk_begin() const {
- return InternalChunkIterator(this);
-}
-
-inline Cord::InternalChunkRange Cord::InternalChunks() const {
- return InternalChunkRange(this);
-}
-
// --------------------------------------------------------------------
// Constructors and destructors
@@ -918,7 +883,7 @@ void Cord::Prepend(absl::string_view src) {
static CordRep* RemovePrefixFrom(CordRep* node, size_t n) {
if (n >= node->length) return nullptr;
if (n == 0) return Ref(node);
- cord_internal::CordTreeMutablePath rhs_stack;
+ absl::InlinedVector<CordRep*, kInlinedVectorSize> rhs_stack;
while (node->tag == CONCAT) {
assert(n <= node->length);
@@ -959,7 +924,7 @@ static CordRep* RemovePrefixFrom(CordRep* node, size_t n) {
static CordRep* RemoveSuffixFrom(CordRep* node, size_t n) {
if (n >= node->length) return nullptr;
if (n == 0) return Ref(node);
- absl::cord_internal::CordTreeMutablePath lhs_stack;
+ absl::InlinedVector<CordRep*, kInlinedVectorSize> lhs_stack;
bool inplace_ok = node->refcount.IsOne();
while (node->tag == CONCAT) {
@@ -1030,7 +995,6 @@ void Cord::RemoveSuffix(size_t n) {
// Work item for NewSubRange().
struct SubRange {
- SubRange() = default;
SubRange(CordRep* a_node, size_t a_pos, size_t a_n)
: node(a_node), pos(a_pos), n(a_n) {}
CordRep* node; // nullptr means concat last 2 results.
@@ -1039,11 +1003,8 @@ struct SubRange {
};
static CordRep* NewSubRange(CordRep* node, size_t pos, size_t n) {
- cord_internal::CordTreeMutablePath results;
- // The algorithm below in worst case scenario adds up to 3 nodes to the `todo`
- // list, but we also pop one out on every cycle. If original tree has depth d
- // todo list can grew up to 2*d in size.
- cord_internal::CordTreePath<SubRange, 2 * cord_internal::MaxCordDepth()> todo;
+ absl::InlinedVector<CordRep*, kInlinedVectorSize> results;
+ absl::InlinedVector<SubRange, kInlinedVectorSize> todo;
todo.push_back(SubRange(node, pos, n));
do {
const SubRange& sr = todo.back();
@@ -1080,7 +1041,7 @@ static CordRep* NewSubRange(CordRep* node, size_t pos, size_t n) {
}
} while (!todo.empty());
assert(results.size() == 1);
- return results.back();
+ return results[0];
}
Cord Cord::Subcord(size_t pos, size_t new_size) const {
@@ -1096,7 +1057,7 @@ Cord Cord::Subcord(size_t pos, size_t new_size) const {
} else if (new_size == 0) {
// We want to return empty subcord, so nothing to do.
} else if (new_size <= InlineRep::kMaxInline) {
- Cord::InternalChunkIterator it = internal_chunk_begin();
+ Cord::ChunkIterator it = chunk_begin();
it.AdvanceBytes(pos);
char* dest = sub_cord.contents_.data_;
size_t remaining_size = new_size;
@@ -1119,12 +1080,11 @@ Cord Cord::Subcord(size_t pos, size_t new_size) const {
class CordForest {
public:
- explicit CordForest(size_t length) : root_length_(length), trees_({}) {}
+ explicit CordForest(size_t length)
+ : root_length_(length), trees_(kMinLengthSize, nullptr) {}
void Build(CordRep* cord_root) {
- // We are adding up to two nodes to the `pending` list, but we also popping
- // one, so the size of `pending` will never exceed `MaxCordDepth()`.
- cord_internal::CordTreeMutablePath pending(cord_root);
+ std::vector<CordRep*> pending = {cord_root};
while (!pending.empty()) {
CordRep* node = pending.back();
@@ -1136,20 +1096,21 @@ class CordForest {
}
CordRepConcat* concat_node = node->concat();
- if (IsNodeBalanced(concat_node)) {
- AddNode(node);
- continue;
- }
- pending.push_back(concat_node->right);
- pending.push_back(concat_node->left);
-
- if (concat_node->refcount.IsOne()) {
- concat_node->left = concat_freelist_;
- concat_freelist_ = concat_node;
+ if (concat_node->depth() >= kMinLengthSize ||
+ concat_node->length < min_length[concat_node->depth()]) {
+ pending.push_back(concat_node->right);
+ pending.push_back(concat_node->left);
+
+ if (concat_node->refcount.IsOne()) {
+ concat_node->left = concat_freelist_;
+ concat_freelist_ = concat_node;
+ } else {
+ Ref(concat_node->right);
+ Ref(concat_node->left);
+ Unref(concat_node);
+ }
} else {
- Ref(concat_node->right);
- Ref(concat_node->left);
- Unref(concat_node);
+ AddNode(node);
}
}
}
@@ -1181,7 +1142,7 @@ class CordForest {
// Collect together everything with which we will merge with node
int i = 0;
- for (; node->length >= kMinLength[i + 1]; ++i) {
+ for (; node->length > min_length[i + 1]; ++i) {
auto& tree_at_i = trees_[i];
if (tree_at_i == nullptr) continue;
@@ -1192,7 +1153,7 @@ class CordForest {
sum = AppendNode(node, sum);
// Insert sum into appropriate place in the forest
- for (; sum->length >= kMinLength[i]; ++i) {
+ for (; sum->length >= min_length[i]; ++i) {
auto& tree_at_i = trees_[i];
if (tree_at_i == nullptr) continue;
@@ -1200,7 +1161,7 @@ class CordForest {
tree_at_i = nullptr;
}
- // kMinLength[0] == 1, which means sum->length >= kMinLength[0]
+ // min_length[0] == 1, which means sum->length >= min_length[0]
assert(i > 0);
trees_[i - 1] = sum;
}
@@ -1233,7 +1194,9 @@ class CordForest {
}
size_t root_length_;
- std::array<cord_internal::CordRep*, cord_internal::MaxCordDepth()> trees_;
+
+ // use an inlined vector instead of a flat array to get bounds checking
+ absl::InlinedVector<CordRep*, kInlinedVectorSize> trees_;
// List of concat nodes we can re-use for Cord balancing.
CordRepConcat* concat_freelist_ = nullptr;
@@ -1334,7 +1297,7 @@ inline absl::string_view Cord::InlineRep::FindFlatStartPiece() const {
inline int Cord::CompareSlowPath(absl::string_view rhs, size_t compared_size,
size_t size_to_compare) const {
- auto advance = [](Cord::InternalChunkIterator* it, absl::string_view* chunk) {
+ auto advance = [](Cord::ChunkIterator* it, absl::string_view* chunk) {
if (!chunk->empty()) return true;
++*it;
if (it->bytes_remaining_ == 0) return false;
@@ -1342,7 +1305,7 @@ inline int Cord::CompareSlowPath(absl::string_view rhs, size_t compared_size,
return true;
};
- Cord::InternalChunkIterator lhs_it = internal_chunk_begin();
+ Cord::ChunkIterator lhs_it = chunk_begin();
// compared_size is inside first chunk.
absl::string_view lhs_chunk =
@@ -1364,7 +1327,7 @@ inline int Cord::CompareSlowPath(absl::string_view rhs, size_t compared_size,
inline int Cord::CompareSlowPath(const Cord& rhs, size_t compared_size,
size_t size_to_compare) const {
- auto advance = [](Cord::InternalChunkIterator* it, absl::string_view* chunk) {
+ auto advance = [](Cord::ChunkIterator* it, absl::string_view* chunk) {
if (!chunk->empty()) return true;
++*it;
if (it->bytes_remaining_ == 0) return false;
@@ -1372,8 +1335,8 @@ inline int Cord::CompareSlowPath(const Cord& rhs, size_t compared_size,
return true;
};
- Cord::InternalChunkIterator lhs_it = internal_chunk_begin();
- Cord::InternalChunkIterator rhs_it = rhs.internal_chunk_begin();
+ Cord::ChunkIterator lhs_it = chunk_begin();
+ Cord::ChunkIterator rhs_it = rhs.chunk_begin();
// compared_size is inside both first chunks.
absl::string_view lhs_chunk =
@@ -1507,9 +1470,7 @@ void Cord::CopyToArraySlowPath(char* dst) const {
}
}
-template <typename StorageType>
-Cord::GenericChunkIterator<StorageType>&
-Cord::GenericChunkIterator<StorageType>::operator++() {
+Cord::ChunkIterator& Cord::ChunkIterator::operator++() {
ABSL_HARDENING_ASSERT(bytes_remaining_ > 0 &&
"Attempted to iterate past `end()`");
assert(bytes_remaining_ >= current_chunk_.size());
@@ -1549,8 +1510,7 @@ Cord::GenericChunkIterator<StorageType>::operator++() {
return *this;
}
-template <typename StorageType>
-Cord Cord::GenericChunkIterator<StorageType>::AdvanceAndReadBytes(size_t n) {
+Cord Cord::ChunkIterator::AdvanceAndReadBytes(size_t n) {
ABSL_HARDENING_ASSERT(bytes_remaining_ >= n &&
"Attempted to iterate past `end()`");
Cord subcord;
@@ -1664,8 +1624,7 @@ Cord Cord::GenericChunkIterator<StorageType>::AdvanceAndReadBytes(size_t n) {
return subcord;
}
-template <typename StorageType>
-void Cord::GenericChunkIterator<StorageType>::AdvanceBytesSlowPath(size_t n) {
+void Cord::ChunkIterator::AdvanceBytesSlowPath(size_t n) {
assert(bytes_remaining_ >= n && "Attempted to iterate past `end()`");
assert(n >= current_chunk_.size()); // This should only be called when
// iterating to a new node.
@@ -1851,18 +1810,18 @@ absl::string_view Cord::FlattenSlowPath() {
}
}
-static void DumpNode(const CordRep* rep, bool include_data, std::ostream* os) {
+static void DumpNode(CordRep* rep, bool include_data, std::ostream* os) {
const int kIndentStep = 1;
int indent = 0;
- cord_internal::CordTreeConstPath stack;
- cord_internal::CordTreePath<int, cord_internal::MaxCordDepth()> indents;
+ absl::InlinedVector<CordRep*, kInlinedVectorSize> stack;
+ absl::InlinedVector<int, kInlinedVectorSize> indents;
for (;;) {
*os << std::setw(3) << rep->refcount.Get();
*os << " " << std::setw(7) << rep->length;
*os << " [";
- if (include_data) *os << static_cast<const void*>(rep);
+ if (include_data) *os << static_cast<void*>(rep);
*os << "]";
- *os << " " << (IsNodeBalanced(rep) ? 'b' : 'u');
+ *os << " " << (IsRootBalanced(rep) ? 'b' : 'u');
*os << " " << std::setw(indent) << "";
if (rep->tag == CONCAT) {
*os << "CONCAT depth=" << Depth(rep) << "\n";
@@ -1883,7 +1842,7 @@ static void DumpNode(const CordRep* rep, bool include_data, std::ostream* os) {
} else {
*os << "FLAT cap=" << TagToLength(rep->tag) << " [";
if (include_data)
- *os << absl::CEscape(absl::string_view(rep->data, rep->length));
+ *os << absl::CEscape(std::string(rep->data, rep->length));
*os << "]\n";
}
if (stack.empty()) break;
@@ -1896,19 +1855,19 @@ static void DumpNode(const CordRep* rep, bool include_data, std::ostream* os) {
ABSL_INTERNAL_CHECK(indents.empty(), "");
}
-static std::string ReportError(const CordRep* root, const CordRep* node) {
+static std::string ReportError(CordRep* root, CordRep* node) {
std::ostringstream buf;
buf << "Error at node " << node << " in:";
DumpNode(root, true, &buf);
return buf.str();
}
-static bool VerifyNode(const CordRep* root, const CordRep* start_node,
+static bool VerifyNode(CordRep* root, CordRep* start_node,
bool full_validation) {
- cord_internal::CordTreeConstPath worklist;
+ absl::InlinedVector<CordRep*, 2> worklist;
worklist.push_back(start_node);
do {
- const CordRep* node = worklist.back();
+ CordRep* node = worklist.back();
worklist.pop_back();
ABSL_INTERNAL_CHECK(node != nullptr, ReportError(root, node));
@@ -1958,7 +1917,7 @@ static bool VerifyNode(const CordRep* root, const CordRep* start_node,
// Iterate over the tree. cur_node is never a leaf node and leaf nodes will
// never be appended to tree_stack. This reduces overhead from manipulating
// tree_stack.
- cord_internal::CordTreeConstPath tree_stack;
+ absl::InlinedVector<const CordRep*, kInlinedVectorSize> tree_stack;
const CordRep* cur_node = rep;
while (true) {
const CordRep* next_node = nullptr;
@@ -2005,9 +1964,6 @@ std::ostream& operator<<(std::ostream& out, const Cord& cord) {
return out;
}
-template class Cord::GenericChunkIterator<cord_internal::CordTreeMutablePath>;
-template class Cord::GenericChunkIterator<cord_internal::CordTreeDynamicPath>;
-
namespace strings_internal {
size_t CordTestAccess::FlatOverhead() { return kFlatOverhead; }
size_t CordTestAccess::MaxFlatLength() { return kMaxFlatLength; }
diff --git a/absl/strings/cord.h b/absl/strings/cord.h
index d5b9363f..5136f926 100644
--- a/absl/strings/cord.h
+++ b/absl/strings/cord.h
@@ -123,132 +123,12 @@ H HashFragmentedCord(H, const Cord&);
// Additionally, the API provides iterator utilities to iterate through Cord
// data via chunks or character bytes.
//
-
-namespace cord_internal {
-
-// It's expensive to keep a Cord's tree perfectly balanced, so instead we keep
-// trees approximately balanced. A tree node N of depth D(N) that contains a
-// string of L(N) characters is considered balanced if L >= Fibonacci(D + 2).
-// The "+ 2" is used to ensure that every balanced leaf node contains at least
-// one character. Here we presume that
-// Fibonacci(0) = 0
-// Fibonacci(1) = 1
-// Fibonacci(2) = 1
-// Fibonacci(3) = 2
-// ...
-// The algorithm is based on paper by Hans Boehm et al:
-// https://www.cs.rit.edu/usr/local/pub/jeh/courses/QUARTERS/FP/Labs/CedarRope/rope-paper.pdf
-// In this paper authors shows that rebalancing based on cord forest of already
-// balanced subtrees can be proven to never produce tree of depth larger than
-// largest Fibonacci number representable in the same integral type as cord size
-// For 64 bit integers this is the 93rd Fibonacci number. For 32 bit integrals
-// this is 47th Fibonacci number.
-constexpr size_t MaxCordDepth() { return sizeof(size_t) == 8 ? 93 : 47; }
-
-// This class models fixed max size stack of CordRep pointers.
-// The elements are being pushed back and popped from the back.
-template <typename CordRepPtr, size_t N>
-class CordTreePath {
- public:
- CordTreePath() {}
- explicit CordTreePath(CordRepPtr root) { push_back(root); }
-
- bool empty() const { return size_ == 0; }
- size_t size() const { return size_; }
- void clear() { size_ = 0; }
-
- CordRepPtr back() { return data_[size_ - 1]; }
-
- void pop_back() {
- --size_;
- assert(size_ < N);
- }
- void push_back(CordRepPtr elem) { data_[size_++] = elem; }
-
- private:
- CordRepPtr data_[N];
- size_t size_ = 0;
-};
-
-// Fixed length container for mutable "path" in cord tree, which can hold any
-// possible valid path in cord tree.
-using CordTreeMutablePath = CordTreePath<CordRep*, MaxCordDepth()>;
-// Variable length container for mutable "path" in cord tree. It starts with
-// capacity for 15 elements and grow if necessary.
-using CordTreeDynamicPath =
- absl::InlinedVector<absl::cord_internal::CordRep*, 15>;
-} // namespace cord_internal
-
-// A Cord is a sequence of characters.
class Cord {
private:
template <typename T>
using EnableIfString =
absl::enable_if_t<std::is_same<T, std::string>::value, int>;
- //----------------------------------------------------------------------------
- // Cord::GenericChunkIterator
- //----------------------------------------------------------------------------
- //
- // A `Cord::GenericChunkIterator` provides an interface for the standard
- // `Cord::ChunkIterator` as well as some private implementations.
- template <typename StorageType>
- class GenericChunkIterator {
- public:
- using iterator_category = std::input_iterator_tag;
- using value_type = absl::string_view;
- using difference_type = ptrdiff_t;
- using pointer = const value_type*;
- using reference = value_type;
-
- GenericChunkIterator() = default;
-
- GenericChunkIterator& operator++();
- GenericChunkIterator operator++(int);
- bool operator==(const GenericChunkIterator& other) const;
- bool operator!=(const GenericChunkIterator& other) const;
- reference operator*() const;
- pointer operator->() const;
-
- friend class Cord;
- friend class CharIterator;
-
- private:
- // Constructs a `begin()` iterator from `cord`.
- explicit GenericChunkIterator(const Cord* cord);
-
- // Removes `n` bytes from `current_chunk_`. Expects `n` to be smaller than
- // `current_chunk_.size()`.
- void RemoveChunkPrefix(size_t n);
- Cord AdvanceAndReadBytes(size_t n);
- void AdvanceBytes(size_t n);
- // Iterates `n` bytes, where `n` is expected to be greater than or equal to
- // `current_chunk_.size()`.
- void AdvanceBytesSlowPath(size_t n);
-
- // A view into bytes of the current `CordRep`. It may only be a view to a
- // suffix of bytes if this is being used by `CharIterator`.
- absl::string_view current_chunk_;
- // The current leaf, or `nullptr` if the iterator points to short data.
- // If the current chunk is a substring node, current_leaf_ points to the
- // underlying flat or external node.
- cord_internal::CordRep* current_leaf_ = nullptr;
- // The number of bytes left in the `Cord` over which we are iterating.
- size_t bytes_remaining_ = 0;
- StorageType stack_of_right_children_;
- };
- template <typename IteratorType>
- class GenericChunkRange {
- public:
- explicit GenericChunkRange(const Cord* cord) : cord_(cord) {}
-
- IteratorType begin() const { return IteratorType(cord_); }
- IteratorType end() const { return IteratorType(); }
-
- private:
- const Cord* cord_;
- };
-
public:
// Cord::Cord() Constructors
@@ -464,8 +344,51 @@ class Cord {
// * The iterator keeps state that can grow for Cords that contain many
// nodes and are imbalanced due to sharing. Prefer to pass this type by
// const reference instead of by value.
- using ChunkIterator =
- GenericChunkIterator<cord_internal::CordTreeDynamicPath>;
+ class ChunkIterator {
+ public:
+ using iterator_category = std::input_iterator_tag;
+ using value_type = absl::string_view;
+ using difference_type = ptrdiff_t;
+ using pointer = const value_type*;
+ using reference = value_type;
+
+ ChunkIterator() = default;
+
+ ChunkIterator& operator++();
+ ChunkIterator operator++(int);
+ bool operator==(const ChunkIterator& other) const;
+ bool operator!=(const ChunkIterator& other) const;
+ reference operator*() const;
+ pointer operator->() const;
+
+ friend class Cord;
+ friend class CharIterator;
+
+ private:
+ // Constructs a `begin()` iterator from `cord`.
+ explicit ChunkIterator(const Cord* cord);
+
+ // Removes `n` bytes from `current_chunk_`. Expects `n` to be smaller than
+ // `current_chunk_.size()`.
+ void RemoveChunkPrefix(size_t n);
+ Cord AdvanceAndReadBytes(size_t n);
+ void AdvanceBytes(size_t n);
+ // Iterates `n` bytes, where `n` is expected to be greater than or equal to
+ // `current_chunk_.size()`.
+ void AdvanceBytesSlowPath(size_t n);
+
+ // A view into bytes of the current `CordRep`. It may only be a view to a
+ // suffix of bytes if this is being used by `CharIterator`.
+ absl::string_view current_chunk_;
+ // The current leaf, or `nullptr` if the iterator points to short data.
+ // If the current chunk is a substring node, current_leaf_ points to the
+ // underlying flat or external node.
+ absl::cord_internal::CordRep* current_leaf_ = nullptr;
+ // The number of bytes left in the `Cord` over which we are iterating.
+ size_t bytes_remaining_ = 0;
+ absl::InlinedVector<absl::cord_internal::CordRep*, 4>
+ stack_of_right_children_;
+ };
// Cord::ChunkIterator::chunk_begin()
//
@@ -504,7 +427,16 @@ class Cord {
//
// Implementation note: `ChunkRange` is simply a convenience wrapper over
// `Cord::chunk_begin()` and `Cord::chunk_end()`.
- using ChunkRange = GenericChunkRange<ChunkIterator>;
+ class ChunkRange {
+ public:
+ explicit ChunkRange(const Cord* cord) : cord_(cord) {}
+
+ ChunkIterator begin() const;
+ ChunkIterator end() const;
+
+ private:
+ const Cord* cord_;
+ };
// Cord::Chunks()
//
@@ -800,14 +732,6 @@ class Cord {
static bool GetFlatAux(absl::cord_internal::CordRep* rep,
absl::string_view* fragment);
- // Iterators for use inside Cord implementation
- using InternalChunkIterator =
- GenericChunkIterator<cord_internal::CordTreeMutablePath>;
- using InternalChunkRange = GenericChunkRange<InternalChunkIterator>;
-
- InternalChunkIterator internal_chunk_begin() const;
- InternalChunkRange InternalChunks() const;
-
// Helper for ForEachChunk()
static void ForEachChunkAux(
absl::cord_internal::CordRep* rep,
@@ -842,11 +766,6 @@ class Cord {
void AppendImpl(C&& src);
};
-extern template class Cord::GenericChunkIterator<
- cord_internal::CordTreeMutablePath>;
-extern template class Cord::GenericChunkIterator<
- cord_internal::CordTreeDynamicPath>;
-
ABSL_NAMESPACE_END
} // namespace absl
@@ -1186,9 +1105,7 @@ inline bool Cord::StartsWith(absl::string_view rhs) const {
return EqualsImpl(rhs, rhs_size);
}
-template <typename StorageType>
-inline Cord::GenericChunkIterator<StorageType>::GenericChunkIterator(
- const Cord* cord)
+inline Cord::ChunkIterator::ChunkIterator(const Cord* cord)
: bytes_remaining_(cord->size()) {
if (cord->empty()) return;
if (cord->contents_.is_tree()) {
@@ -1199,50 +1116,37 @@ inline Cord::GenericChunkIterator<StorageType>::GenericChunkIterator(
}
}
-template <typename StorageType>
-inline Cord::GenericChunkIterator<StorageType>
-Cord::GenericChunkIterator<StorageType>::operator++(int) {
- GenericChunkIterator tmp(*this);
+inline Cord::ChunkIterator Cord::ChunkIterator::operator++(int) {
+ ChunkIterator tmp(*this);
operator++();
return tmp;
}
-template <typename StorageType>
-inline bool Cord::GenericChunkIterator<StorageType>::operator==(
- const GenericChunkIterator<StorageType>& other) const {
+inline bool Cord::ChunkIterator::operator==(const ChunkIterator& other) const {
return bytes_remaining_ == other.bytes_remaining_;
}
-template <typename StorageType>
-inline bool Cord::GenericChunkIterator<StorageType>::operator!=(
- const GenericChunkIterator<StorageType>& other) const {
+inline bool Cord::ChunkIterator::operator!=(const ChunkIterator& other) const {
return !(*this == other);
}
-template <typename StorageType>
-inline typename Cord::GenericChunkIterator<StorageType>::reference
-Cord::GenericChunkIterator<StorageType>::operator*() const {
+inline Cord::ChunkIterator::reference Cord::ChunkIterator::operator*() const {
ABSL_HARDENING_ASSERT(bytes_remaining_ != 0);
return current_chunk_;
}
-template <typename StorageType>
-inline typename Cord::GenericChunkIterator<StorageType>::pointer
-Cord::GenericChunkIterator<StorageType>::operator->() const {
+inline Cord::ChunkIterator::pointer Cord::ChunkIterator::operator->() const {
ABSL_HARDENING_ASSERT(bytes_remaining_ != 0);
return &current_chunk_;
}
-template <typename StorageType>
-inline void Cord::GenericChunkIterator<StorageType>::RemoveChunkPrefix(
- size_t n) {
+inline void Cord::ChunkIterator::RemoveChunkPrefix(size_t n) {
assert(n < current_chunk_.size());
current_chunk_.remove_prefix(n);
bytes_remaining_ -= n;
}
-template <typename StorageType>
-inline void Cord::GenericChunkIterator<StorageType>::AdvanceBytes(size_t n) {
+inline void Cord::ChunkIterator::AdvanceBytes(size_t n) {
if (ABSL_PREDICT_TRUE(n < current_chunk_.size())) {
RemoveChunkPrefix(n);
} else if (n != 0) {
@@ -1256,6 +1160,14 @@ inline Cord::ChunkIterator Cord::chunk_begin() const {
inline Cord::ChunkIterator Cord::chunk_end() const { return ChunkIterator(); }
+inline Cord::ChunkIterator Cord::ChunkRange::begin() const {
+ return cord_->chunk_begin();
+}
+
+inline Cord::ChunkIterator Cord::ChunkRange::end() const {
+ return cord_->chunk_end();
+}
+
inline Cord::ChunkRange Cord::Chunks() const { return ChunkRange(this); }
inline Cord::CharIterator& Cord::CharIterator::operator++() {
diff --git a/absl/strings/cord_test.cc b/absl/strings/cord_test.cc
index 0ec93b4c..49178498 100644
--- a/absl/strings/cord_test.cc
+++ b/absl/strings/cord_test.cc
@@ -1403,53 +1403,6 @@ TEST(CordChunkIterator, Operations) {
VerifyChunkIterator(subcords, 128);
}
-TEST(CordChunkIterator, MaxLengthFullTree) {
- // Start with a 1-byte cord, and then double its length in a loop. We should
- // be able to do this until the point where we would overflow size_t.
-
- absl::Cord cord;
- size_t size = 1;
- AddExternalMemory("x", &cord);
- EXPECT_EQ(cord.size(), size);
-
- const int kCordLengthDoublingLimit = std::numeric_limits<size_t>::digits - 1;
- for (int i = 0; i < kCordLengthDoublingLimit; ++i) {
- cord.Prepend(absl::Cord(cord));
- size <<= 1;
-
- EXPECT_EQ(cord.size(), size);
-
- auto chunk_it = cord.chunk_begin();
- EXPECT_EQ(*chunk_it, "x");
- }
-
- EXPECT_DEATH_IF_SUPPORTED(
- (cord.Prepend(absl::Cord(cord)), *cord.chunk_begin()),
- "Cord is too long");
-}
-
-TEST(CordChunkIterator, MaxDepth) {
- // By reusing nodes, it's possible in pathological cases to build a Cord that
- // exceeds both the maximum permissible length and depth. In this case, the
- // violation of the maximum depth is reported.
- absl::Cord left_child;
- AddExternalMemory("x", &left_child);
- absl::Cord root = left_child;
-
- for (int i = 0; i < absl::cord_internal::MaxCordDepth() - 2; ++i) {
- size_t new_size = left_child.size() + root.size();
- root.Prepend(left_child);
- EXPECT_EQ(root.size(), new_size);
-
- auto chunk_it = root.chunk_begin();
- EXPECT_EQ(*chunk_it, "x");
-
- std::swap(left_child, root);
- }
-
- EXPECT_DEATH_IF_SUPPORTED(root.Prepend(left_child), "Cord is too long");
-}
-
TEST(CordCharIterator, Traits) {
static_assert(std::is_copy_constructible<absl::Cord::CharIterator>::value,
"");