Export of internal Abseil changes

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f50d25c8f8491ef7031cbbcad78edd15f98c2bd1 by Abseil Team <absl-team@google.com>:

Add myriad2 to HAVE_MMAP
Remove mutex_nonprod and associated defines.

PiperOrigin-RevId: 333759830

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25ef4c577ea983aa3fcd6cfe2af6cdc62a06f520 by Samuel Benzaquen <sbenza@google.com>:

Internal refactor.
Represent the data with a union to allow for better constexpr support in the future.

PiperOrigin-RevId: 333756733
GitOrigin-RevId: f50d25c8f8491ef7031cbbcad78edd15f98c2bd1
Change-Id: Ieecd2c47cb20de638726eb3f9fc2e5682d05dcca

1 files changed, 39 insertions, 0 deletions

diff --git a/absl/strings/internal/cord_internal.h b/absl/strings/internal/cord_internal.h
index d456eef8..00b9baa9 100644
--- a/absl/strings/internal/cord_internal.h
+++ b/absl/strings/internal/cord_internal.h
@@ -85,6 +85,17 @@ struct CordRepConcat;
 struct CordRepSubstring;
 struct CordRepExternal;
 
+// Various representations that we allow
+enum CordRepKind {
+  CONCAT        = 0,
+  EXTERNAL      = 1,
+  SUBSTRING     = 2,
+
+  // We have different tags for different sized flat arrays,
+  // starting with FLAT
+  FLAT          = 3,
+};
+
 struct CordRep {
   // The following three fields have to be less than 32 bytes since
   // that is the smallest supported flat node size.
@@ -167,6 +178,34 @@ struct CordRepExternalImpl
   }
 };
 
+enum {
+  kMaxInline = 15,
+  // Tag byte & kMaxInline means we are storing a pointer.
+  kTreeFlag = 1 << 4,
+  // Tag byte & kProfiledFlag means we are profiling the Cord.
+  kProfiledFlag = 1 << 5
+};
+
+// If the data has length <= kMaxInline, we store it in `as_chars`, and
+// store the size in `tagged_size`.
+// Else we store it in a tree and store a pointer to that tree in
+// `as_tree.rep` and store a tag in `tagged_size`.
+struct AsTree {
+  absl::cord_internal::CordRep* rep;
+  char padding[kMaxInline + 1 - sizeof(absl::cord_internal::CordRep*) - 1];
+  char tagged_size;
+};
+union InlineData {
+  constexpr InlineData() : as_chars{} {}
+  explicit constexpr InlineData(AsTree tree) : as_tree(tree) {}
+
+  AsTree as_tree;
+  char as_chars[kMaxInline + 1];
+};
+static_assert(sizeof(InlineData) == kMaxInline + 1, "");
+static_assert(sizeof(AsTree) == sizeof(InlineData), "");
+static_assert(offsetof(AsTree, tagged_size) == kMaxInline, "");
+
 }  // namespace cord_internal
 ABSL_NAMESPACE_END
 }  // namespace absl