Export of internal Abseil changes

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b885a238ec13effcc407e250583e293052bd7984 by Greg Falcon <gfalcon@google.com>:

Remove the dependency of //absl/hash on //absl/strings:cord.

The `AbslHashValue` definition should reside in cord.h, but the implementation currently needs internal details from the hash library.  This CL changes the way that Cord gains access to those internals.  Note that PiecewiseCombiner remains an internal namespace API, and we still reserve the right to make changes to it.

The cord_benchmark shows no statistically significant changes in hash<Cord> performance with this change.

PiperOrigin-RevId: 307393448

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ca449f230ee719d069d9217ba28a07bf5b3bd8b1 by Derek Mauro <dmauro@google.com>:

Move the extension to use absl::Format() with absl::Cord as a sink to cord.h

PiperOrigin-RevId: 307077162
GitOrigin-RevId: b885a238ec13effcc407e250583e293052bd7984
Change-Id: If24a90782c786fa0b4343bc7d72d053b66c153ea

1 files changed, 25 insertions, 6 deletions

diff --git a/absl/strings/cord.h b/absl/strings/cord.h
index 2d92f6d69e19..9d99b2afd7e0 100644
--- a/absl/strings/cord.h
+++ b/absl/strings/cord.h
@@ -90,10 +90,6 @@ class CordTestPeer;
 template <typename Releaser>
 Cord MakeCordFromExternal(absl::string_view, Releaser&&);
 void CopyCordToString(const Cord& src, std::string* dst);
-namespace hash_internal {
-template <typename H>
-H HashFragmentedCord(H, const Cord&);
-}
 
 // Cord
 //
@@ -615,10 +611,22 @@ class Cord {
   // If the cord was already flat, the contents are not modified.
   absl::string_view Flatten();
 
+  // Support absl::Cord as a sink object for absl::Format().
+  friend void AbslFormatFlush(absl::Cord* cord, absl::string_view part) {
+    cord->Append(part);
+  }
+
+  template <typename H>
+  friend H AbslHashValue(H hash_state, const absl::Cord& c) {
+    absl::optional<absl::string_view> maybe_flat = c.TryFlat();
+    if (maybe_flat.has_value()) {
+      return H::combine(std::move(hash_state), *maybe_flat);
+    }
+    return c.HashFragmented(std::move(hash_state));
+  }
+
  private:
   friend class CordTestPeer;
-  template <typename H>
-  friend H absl::hash_internal::HashFragmentedCord(H, const Cord&);
   friend bool operator==(const Cord& lhs, const Cord& rhs);
   friend bool operator==(const Cord& lhs, absl::string_view rhs);
 
@@ -763,6 +771,17 @@ class Cord {
   // Helper for Append()
   template <typename C>
   void AppendImpl(C&& src);
+
+  // Helper for AbslHashValue()
+  template <typename H>
+  H HashFragmented(H hash_state) const {
+    typename H::AbslInternalPiecewiseCombiner combiner;
+    ForEachChunk([&combiner, &hash_state](absl::string_view chunk) {
+      hash_state = combiner.add_buffer(std::move(hash_state), chunk.data(),
+                                       chunk.size());
+    });
+    return H::combine(combiner.finalize(std::move(hash_state)), size());
+  }
 };
 
 ABSL_NAMESPACE_END