Export of internal Abseil changes

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2c5c118f0615ba90e48ee2f18eccc9f511740f6d by Samuel Benzaquen <sbenza@google.com>:

Rename internal macros to follow the convention in absl.

PiperOrigin-RevId: 299906738

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92d84a707c7ebc4ec19bdd92d5765d1b6d218c1e by Derek Mauro <dmauro@google.com>:

Import GitHub #629: Skip the .exe suffix in the helpshort filter on Windows

PiperOrigin-RevId: 299892396

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2a6910d4be6c67a8376628764121b528ff53504d by Abseil Team <absl-team@google.com>:

Use unsigned int128 intrinsic when available. It generates better branchless code.

PiperOrigin-RevId: 299848585

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110c16cf0a739e1df5028fb6fbd03ef5dde1d278 by Derek Mauro <dmauro@google.com>:

Import GitHub #594: Avoid reading the registry for Windows UWP apps

PiperOrigin-RevId: 299821671

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d8397d367e88163e5e8a47f379c716352dc91d03 by Greg Falcon <gfalcon@google.com>:

Add absl::Hash support for Cord.  The hash function is heterogeneous with other string types: a Cord and a string with the same byte sequence will hash to the same value.

SwissTable types know about Cord, and will allow heterogeneous lookup (e.g., you can pass a Cord to flat_hash_map<string, T>::find(), and vice versa.)

Add a missing dependency to the cmake Cord target.

PiperOrigin-RevId: 299443713
GitOrigin-RevId: 2c5c118f0615ba90e48ee2f18eccc9f511740f6d
Change-Id: I7b087c7984b0cb52c4b337d49266c467b98ebdf9

1 files changed, 21 insertions, 0 deletions

diff --git a/absl/hash/internal/hash.h b/absl/hash/internal/hash.h
index 1cc2c5e5..025d287f 100644
--- a/absl/hash/internal/hash.h
+++ b/absl/hash/internal/hash.h
@@ -43,6 +43,7 @@
 #include "absl/container/fixed_array.h"
 #include "absl/meta/type_traits.h"
 #include "absl/numeric/int128.h"
+#include "absl/strings/cord.h"
 #include "absl/strings/string_view.h"
 #include "absl/types/optional.h"
 #include "absl/types/variant.h"
@@ -413,6 +414,7 @@ H AbslHashValue(H hash_state, const std::shared_ptr<T>& ptr) {
 // All the string-like types supported here provide the same hash expansion for
 // the same character sequence. These types are:
 //
+//  - `absl::Cord`
 //  - `std::string` (and std::basic_string<char, std::char_traits<char>, A> for
 //      any allocator A)
 //  - `absl::string_view` and `std::string_view`
@@ -441,6 +443,25 @@ H AbslHashValue(
       str.size());
 }
 
+template <typename H>
+H HashFragmentedCord(H hash_state, const absl::Cord& c) {
+  PiecewiseCombiner combiner;
+  c.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)), c.size());
+}
+
+template <typename H>
+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 hash_internal::HashFragmentedCord(std::move(hash_state), c);
+}
+
 // -----------------------------------------------------------------------------
 // AbslHashValue for Sequence Containers
 // -----------------------------------------------------------------------------