Export of internal Abseil changes

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912c205cf80c4ed24a08000c04263403857b7f75 by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 373620391

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d454f10549d27d7b025d1ce0ef90a0cdec42c361 by Martijn Vels <mvels@google.com>:

Add SetCordRepForTesting() helper to CordzInfo

PiperOrigin-RevId: 373602832

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7a2d7bdd2e60fb51333e81cd71ebd0a4edb60704 by Evan Brown <ezb@google.com>:

For StrAppend, make sure to follow exponential growth like std::string::append.

PiperOrigin-RevId: 373589332

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24397f19bce45133a42feaa7c883009ef9325095 by Greg Falcon <gfalcon@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 373569246
GitOrigin-RevId: 912c205cf80c4ed24a08000c04263403857b7f75
Change-Id: I5444f7ca2c0980685ca5c51596c259b845d69673

1 files changed, 23 insertions, 0 deletions

diff --git a/absl/strings/internal/resize_uninitialized.h b/absl/strings/internal/resize_uninitialized.h
index e42628e3..749c66e7 100644
--- a/absl/strings/internal/resize_uninitialized.h
+++ b/absl/strings/internal/resize_uninitialized.h
@@ -17,6 +17,7 @@
 #ifndef ABSL_STRINGS_INTERNAL_RESIZE_UNINITIALIZED_H_
 #define ABSL_STRINGS_INTERNAL_RESIZE_UNINITIALIZED_H_
 
+#include <algorithm>
 #include <string>
 #include <type_traits>
 #include <utility>
@@ -66,6 +67,28 @@ inline void STLStringResizeUninitialized(string_type* s, size_t new_size) {
   ResizeUninitializedTraits<string_type>::Resize(s, new_size);
 }
 
+// Used to ensure exponential growth so that the amortized complexity of
+// increasing the string size by a small amount is O(1), in contrast to
+// O(str->size()) in the case of precise growth.
+template <typename string_type>
+void STLStringReserveAmortized(string_type* s, size_t new_size) {
+  const size_t cap = s->capacity();
+  if (new_size > cap) {
+    // Make sure to always grow by at least a factor of 2x.
+    s->reserve((std::max)(new_size, 2 * cap));
+  }
+}
+
+// Like STLStringResizeUninitialized(str, new_size), except guaranteed to use
+// exponential growth so that the amortized complexity of increasing the string
+// size by a small amount is O(1), in contrast to O(str->size()) in the case of
+// precise growth.
+template <typename string_type>
+void STLStringResizeUninitializedAmortized(string_type* s, size_t new_size) {
+  STLStringReserveAmortized(s, new_size);
+  STLStringResizeUninitialized(s, new_size);
+}
+
 }  // namespace strings_internal
 ABSL_NAMESPACE_END
 }  // namespace absl