Allow Cord to store chunked checksums

PiperOrigin-RevId: 494587777
Change-Id: I41504edca6fcf750d52602fa84a33bc7fe5fbb48

8 files changed, 68 insertions, 26 deletions

diff --git a/absl/strings/BUILD.bazel b/absl/strings/BUILD.bazel
index 3c852989..d86f59f0 100644
--- a/absl/strings/BUILD.bazel
+++ b/absl/strings/BUILD.bazel
@@ -324,6 +324,7 @@ cc_library(
         "//absl/container:compressed_tuple",
         "//absl/container:inlined_vector",
         "//absl/container:layout",
+        "//absl/crc:crc_cord_state",
         "//absl/functional:function_ref",
         "//absl/meta:type_traits",
         "//absl/types:span",
@@ -405,6 +406,7 @@ cc_test(
         ":cord_internal",
         ":cord_rep_test_util",
         "//absl/base:config",
+        "//absl/crc:crc_cord_state",
         "@com_google_googletest//:gtest_main",
     ],
 )
@@ -463,6 +465,7 @@ cc_library(
         "//absl/base:raw_logging_internal",
         "//absl/container:fixed_array",
         "//absl/container:inlined_vector",
+        "//absl/crc:crc_cord_state",
         "//absl/functional:function_ref",
         "//absl/meta:type_traits",
         "//absl/numeric:bits",
@@ -659,6 +662,7 @@ cc_test(
         ":cordz_update_scope",
         ":cordz_update_tracker",
         "//absl/base:config",
+        "//absl/crc:crc_cord_state",
         "//absl/synchronization",
         "//absl/synchronization:thread_pool",
         "@com_google_googletest//:gtest_main",
diff --git a/absl/strings/CMakeLists.txt b/absl/strings/CMakeLists.txt
index 33e4ff1b..a23b34a1 100644
--- a/absl/strings/CMakeLists.txt
+++ b/absl/strings/CMakeLists.txt
@@ -605,6 +605,7 @@ absl_cc_library(
     absl::compressed_tuple
     absl::config
     absl::core_headers
+    absl::crc_cord_state
     absl::endian
     absl::inlined_vector
     absl::layout
@@ -783,6 +784,7 @@ absl_cc_test(
     absl::cordz_statistics
     absl::cordz_update_scope
     absl::cordz_update_tracker
+    absl::crc_cord_state
     absl::thread_pool
     GTest::gmock_main
 )
@@ -882,6 +884,7 @@ absl_cc_library(
     absl::cordz_update_scope
     absl::cordz_update_tracker
     absl::core_headers
+    absl::crc_cord_state
     absl::endian
     absl::fixed_array
     absl::function_ref
@@ -1054,6 +1057,7 @@ absl_cc_test(
     absl::config
     absl::cord_internal
     absl::cord_rep_test_util
+    absl::crc_cord_state
     GTest::gmock_main
 )
 
diff --git a/absl/strings/cord.cc b/absl/strings/cord.cc
index 92822c05..0bac4164 100644
--- a/absl/strings/cord.cc
+++ b/absl/strings/cord.cc
@@ -35,6 +35,7 @@
 #include "absl/base/port.h"
 #include "absl/container/fixed_array.h"
 #include "absl/container/inlined_vector.h"
+#include "absl/crc/internal/crc_cord_state.h"
 #include "absl/strings/cord_buffer.h"
 #include "absl/strings/escaping.h"
 #include "absl/strings/internal/cord_data_edge.h"
@@ -854,28 +855,44 @@ inline absl::string_view Cord::InlineRep::FindFlatStartPiece() const {
   return absl::string_view(node->external()->base + offset, length);
 }
 
-void Cord::SetExpectedChecksum(uint32_t crc) {
+void Cord::SetCrcCordState(crc_internal::CrcCordState state) {
   auto constexpr method = CordzUpdateTracker::kSetExpectedChecksum;
   if (empty()) {
     contents_.MaybeRemoveEmptyCrcNode();
-    CordRep* rep = CordRepCrc::New(nullptr, crc);
+    CordRep* rep = CordRepCrc::New(nullptr, std::move(state));
     contents_.EmplaceTree(rep, method);
   } else if (!contents_.is_tree()) {
     CordRep* rep = contents_.MakeFlatWithExtraCapacity(0);
-    rep = CordRepCrc::New(rep, crc);
+    rep = CordRepCrc::New(rep, std::move(state));
     contents_.EmplaceTree(rep, method);
   } else {
     const CordzUpdateScope scope(contents_.data_.cordz_info(), method);
-    CordRep* rep = CordRepCrc::New(contents_.data_.as_tree(), crc);
+    CordRep* rep = CordRepCrc::New(contents_.data_.as_tree(), std::move(state));
     contents_.SetTree(rep, scope);
   }
 }
 
+void Cord::SetExpectedChecksum(uint32_t crc) {
+  // Construct a CrcCordState with a single chunk.
+  crc_internal::CrcCordState state;
+  state.mutable_rep()->prefix_crc.push_back(
+      crc_internal::CrcCordState::PrefixCrc(size(), absl::crc32c_t{crc}));
+  SetCrcCordState(std::move(state));
+}
+
+const crc_internal::CrcCordState* Cord::MaybeGetCrcCordState() const {
+  if (!contents_.is_tree() || !contents_.tree()->IsCrc()) {
+    return nullptr;
+  }
+  return &contents_.tree()->crc()->crc_cord_state;
+}
+
 absl::optional<uint32_t> Cord::ExpectedChecksum() const {
   if (!contents_.is_tree() || !contents_.tree()->IsCrc()) {
     return absl::nullopt;
   }
-  return contents_.tree()->crc()->crc;
+  return static_cast<uint32_t>(
+      contents_.tree()->crc()->crc_cord_state.Checksum());
 }
 
 inline int Cord::CompareSlowPath(absl::string_view rhs, size_t compared_size,
@@ -1255,7 +1272,7 @@ static void DumpNode(CordRep* rep, bool include_data, std::ostream* os,
       *os << "NULL\n";
       leaf = true;
     } else if (rep->IsCrc()) {
-      *os << "CRC crc=" << rep->crc()->crc << "\n";
+      *os << "CRC crc=" << rep->crc()->crc_cord_state.Checksum() << "\n";
       indent += kIndentStep;
       rep = rep->crc()->child;
     } else if (rep->IsSubstring()) {
diff --git a/absl/strings/cord.h b/absl/strings/cord.h
index 6e3da89e..1349b115 100644
--- a/absl/strings/cord.h
+++ b/absl/strings/cord.h
@@ -76,6 +76,7 @@
 #include "absl/base/macros.h"
 #include "absl/base/port.h"
 #include "absl/container/inlined_vector.h"
+#include "absl/crc/internal/crc_cord_state.h"
 #include "absl/functional/function_ref.h"
 #include "absl/meta/type_traits.h"
 #include "absl/strings/cord_analysis.h"
@@ -1002,6 +1003,10 @@ class Cord {
     });
     return H::combine(combiner.finalize(std::move(hash_state)), size());
   }
+
+  friend class CrcCord;
+  void SetCrcCordState(crc_internal::CrcCordState state);
+  const crc_internal::CrcCordState* MaybeGetCrcCordState() const;
 };
 
 ABSL_NAMESPACE_END
diff --git a/absl/strings/internal/cord_rep_crc.cc b/absl/strings/internal/cord_rep_crc.cc
index 7d7273ef..dbe54cc4 100644
--- a/absl/strings/internal/cord_rep_crc.cc
+++ b/absl/strings/internal/cord_rep_crc.cc
@@ -16,6 +16,7 @@
 
 #include <cassert>
 #include <cstdint>
+#include <utility>
 
 #include "absl/base/config.h"
 #include "absl/strings/internal/cord_internal.h"
@@ -24,10 +25,10 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace cord_internal {
 
-CordRepCrc* CordRepCrc::New(CordRep* child, uint32_t crc) {
+CordRepCrc* CordRepCrc::New(CordRep* child, crc_internal::CrcCordState state) {
   if (child != nullptr && child->IsCrc()) {
     if (child->refcount.IsOne()) {
-      child->crc()->crc = crc;
+      child->crc()->crc_cord_state = std::move(state);
       return child->crc();
     }
     CordRep* old = child;
@@ -39,7 +40,7 @@ CordRepCrc* CordRepCrc::New(CordRep* child, uint32_t crc) {
   new_cordrep->length = child != nullptr ? child->length : 0;
   new_cordrep->tag = cord_internal::CRC;
   new_cordrep->child = child;
-  new_cordrep->crc = crc;
+  new_cordrep->crc_cord_state = std::move(state);
   return new_cordrep;
 }
 
diff --git a/absl/strings/internal/cord_rep_crc.h b/absl/strings/internal/cord_rep_crc.h
index 455a1127..379d7a60 100644
--- a/absl/strings/internal/cord_rep_crc.h
+++ b/absl/strings/internal/cord_rep_crc.h
@@ -20,6 +20,7 @@
 
 #include "absl/base/config.h"
 #include "absl/base/optimization.h"
+#include "absl/crc/internal/crc_cord_state.h"
 #include "absl/strings/internal/cord_internal.h"
 
 namespace absl {
@@ -34,14 +35,14 @@ namespace cord_internal {
 // the contained checksum is the user's responsibility.
 struct CordRepCrc : public CordRep {
   CordRep* child;
-  uint32_t crc;
+  absl::crc_internal::CrcCordState crc_cord_state;
 
   // Consumes `child` and returns a CordRepCrc prefixed tree containing `child`.
   // If the specified `child` is itself a CordRepCrc node, then this method
-  // either replaces the existing node, or directly updates the crc value in it
+  // either replaces the existing node, or directly updates the crc state in it
   // depending on the node being shared or not, i.e.: refcount.IsOne().
   // `child` must only be null if the Cord is empty. Never returns null.
-  static CordRepCrc* New(CordRep* child, uint32_t crc);
+  static CordRepCrc* New(CordRep* child, crc_internal::CrcCordState state);
 
   // Destroys (deletes) the provided node. `node` must not be null.
   static void Destroy(CordRepCrc* node);
diff --git a/absl/strings/internal/cord_rep_crc_test.cc b/absl/strings/internal/cord_rep_crc_test.cc
index 42a9110b..3d27c33c 100644
--- a/absl/strings/internal/cord_rep_crc_test.cc
+++ b/absl/strings/internal/cord_rep_crc_test.cc
@@ -17,6 +17,7 @@
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include "absl/base/config.h"
+#include "absl/crc/internal/crc_cord_state.h"
 #include "absl/strings/internal/cord_internal.h"
 #include "absl/strings/internal/cord_rep_test_util.h"
 
@@ -38,33 +39,40 @@ TEST(CordRepCrc, RemoveCrcWithNullptr) {
 
 #endif  // !NDEBUG && GTEST_HAS_DEATH_TEST
 
+absl::crc_internal::CrcCordState MakeCrcCordState(uint32_t crc) {
+  crc_internal::CrcCordState state;
+  state.mutable_rep()->prefix_crc.push_back(
+      crc_internal::CrcCordState::PrefixCrc(42, crc32c_t{crc}));
+  return state;
+}
+
 TEST(CordRepCrc, NewDestroy) {
   CordRep* rep = cordrep_testing::MakeFlat("Hello world");
-  CordRepCrc* crc = CordRepCrc::New(rep, 12345);
+  CordRepCrc* crc = CordRepCrc::New(rep, MakeCrcCordState(12345));
   EXPECT_TRUE(crc->refcount.IsOne());
   EXPECT_THAT(crc->child, Eq(rep));
-  EXPECT_THAT(crc->crc, Eq(12345u));
+  EXPECT_THAT(crc->crc_cord_state.Checksum(), Eq(crc32c_t{12345u}));
   EXPECT_TRUE(rep->refcount.IsOne());
   CordRepCrc::Destroy(crc);
 }
 
 TEST(CordRepCrc, NewExistingCrcNotShared) {
   CordRep* rep = cordrep_testing::MakeFlat("Hello world");
-  CordRepCrc* crc = CordRepCrc::New(rep, 12345);
-  CordRepCrc* new_crc = CordRepCrc::New(crc, 54321);
+  CordRepCrc* crc = CordRepCrc::New(rep, MakeCrcCordState(12345));
+  CordRepCrc* new_crc = CordRepCrc::New(crc, MakeCrcCordState(54321));
   EXPECT_THAT(new_crc, Eq(crc));
   EXPECT_TRUE(new_crc->refcount.IsOne());
   EXPECT_THAT(new_crc->child, Eq(rep));
-  EXPECT_THAT(new_crc->crc, Eq(54321u));
+  EXPECT_THAT(new_crc->crc_cord_state.Checksum(), Eq(crc32c_t{54321u}));
   EXPECT_TRUE(rep->refcount.IsOne());
   CordRepCrc::Destroy(new_crc);
 }
 
 TEST(CordRepCrc, NewExistingCrcShared) {
   CordRep* rep = cordrep_testing::MakeFlat("Hello world");
-  CordRepCrc* crc = CordRepCrc::New(rep, 12345);
+  CordRepCrc* crc = CordRepCrc::New(rep, MakeCrcCordState(12345));
   CordRep::Ref(crc);
-  CordRepCrc* new_crc = CordRepCrc::New(crc, 54321);
+  CordRepCrc* new_crc = CordRepCrc::New(crc, MakeCrcCordState(54321));
 
   EXPECT_THAT(new_crc, Ne(crc));
   EXPECT_TRUE(new_crc->refcount.IsOne());
@@ -72,19 +80,19 @@ TEST(CordRepCrc, NewExistingCrcShared) {
   EXPECT_FALSE(rep->refcount.IsOne());
   EXPECT_THAT(crc->child, Eq(rep));
   EXPECT_THAT(new_crc->child, Eq(rep));
-  EXPECT_THAT(crc->crc, Eq(12345u));
-  EXPECT_THAT(new_crc->crc, Eq(54321u));
+  EXPECT_THAT(crc->crc_cord_state.Checksum(), Eq(crc32c_t{12345u}));
+  EXPECT_THAT(new_crc->crc_cord_state.Checksum(), Eq(crc32c_t{54321u}));
 
   CordRep::Unref(crc);
   CordRep::Unref(new_crc);
 }
 
 TEST(CordRepCrc, NewEmpty) {
-  CordRepCrc* crc = CordRepCrc::New(nullptr, 12345);
+  CordRepCrc* crc = CordRepCrc::New(nullptr, MakeCrcCordState(12345));
   EXPECT_TRUE(crc->refcount.IsOne());
   EXPECT_THAT(crc->child, IsNull());
   EXPECT_THAT(crc->length, Eq(0u));
-  EXPECT_THAT(crc->crc, Eq(12345u));
+  EXPECT_THAT(crc->crc_cord_state.Checksum(), Eq(crc32c_t{12345u}));
   EXPECT_TRUE(crc->refcount.IsOne());
   CordRepCrc::Destroy(crc);
 }
@@ -98,7 +106,7 @@ TEST(CordRepCrc, RemoveCrcNotCrc) {
 
 TEST(CordRepCrc, RemoveCrcNotShared) {
   CordRep* rep = cordrep_testing::MakeFlat("Hello world");
-  CordRepCrc* crc = CordRepCrc::New(rep, 12345);
+  CordRepCrc* crc = CordRepCrc::New(rep, MakeCrcCordState(12345));
   CordRep* nocrc = RemoveCrcNode(crc);
   EXPECT_THAT(nocrc, Eq(rep));
   EXPECT_TRUE(rep->refcount.IsOne());
@@ -107,7 +115,7 @@ TEST(CordRepCrc, RemoveCrcNotShared) {
 
 TEST(CordRepCrc, RemoveCrcShared) {
   CordRep* rep = cordrep_testing::MakeFlat("Hello world");
-  CordRepCrc* crc = CordRepCrc::New(rep, 12345);
+  CordRepCrc* crc = CordRepCrc::New(rep, MakeCrcCordState(12345));
   CordRep::Ref(crc);
   CordRep* nocrc = RemoveCrcNode(crc);
   EXPECT_THAT(nocrc, Eq(rep));
diff --git a/absl/strings/internal/cordz_info_statistics_test.cc b/absl/strings/internal/cordz_info_statistics_test.cc
index 6d6feb52..53d2f2ea 100644
--- a/absl/strings/internal/cordz_info_statistics_test.cc
+++ b/absl/strings/internal/cordz_info_statistics_test.cc
@@ -19,6 +19,7 @@
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include "absl/base/config.h"
+#include "absl/crc/internal/crc_cord_state.h"
 #include "absl/strings/cord.h"
 #include "absl/strings/internal/cord_internal.h"
 #include "absl/strings/internal/cord_rep_btree.h"
@@ -451,7 +452,8 @@ TEST(CordzInfoStatisticsTest, BtreeNodeShared) {
 TEST(CordzInfoStatisticsTest, Crc) {
   RefHelper ref;
   auto* left = Flat(1000);
-  auto* crc = ref.NeedsUnref(CordRepCrc::New(left, 12345));
+  auto* crc =
+      ref.NeedsUnref(CordRepCrc::New(left, crc_internal::CrcCordState()));
 
   CordzStatistics expected;
   expected.size = left->length;