Export of internal Abseil changes

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f9476c95cf7625d7b0fc4661f253b0aac4341044 by Abseil Team <absl-team@google.com>:

Add a test to verify that the new checksum field in Hashtablez is calculated

PiperOrigin-RevId: 356744293

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ff8a3612463000e8c3d451e50367a3c65cb6cf21 by Abseil Team <absl-team@google.com>:

Remove the implied support comment for port.h, attributes.h, and integral_types.h's C compatibility from the header documentations.

Abseil-cpp is a C++ library; this brings port.h, attributes.h, and integral_types.h, into our stance for the rest of Abseil (aka, no assurance of C compatibility)

There is no guarantee that future changes to port.h, attributes.h, and integral_types.h, and their dependencies, will remain compatible with C, even for macros and definitions that currently are.

PiperOrigin-RevId: 356727505

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be62292016381deee628dbb3f36cb6009bcc0282 by Abseil Team <absl-team@google.com>:

internal change

PiperOrigin-RevId: 356608125

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13b35f17171df3d6853ea7088797b3be611505fc by Evan Brown <ezb@google.com>:

Clarify the comments for CapacityToGrowth/GrowthToLowerboundCapacity methods to specify the intent that capacity should equal growth when `capacity+1 < kWidth`.

Also add testing for this behavior.

PiperOrigin-RevId: 356579041
GitOrigin-RevId: f9476c95cf7625d7b0fc4661f253b0aac4341044
Change-Id: Iadd094d109b4869998f2427319ef66d1cf1e8eff

1 files changed, 11 insertions, 3 deletions

diff --git a/absl/container/internal/raw_hash_set.h b/absl/container/internal/raw_hash_set.h
index 74b2ef4c..80fc2cba 100644
--- a/absl/container/internal/raw_hash_set.h
+++ b/absl/container/internal/raw_hash_set.h
@@ -468,8 +468,16 @@ inline size_t NormalizeCapacity(size_t n) {
   return n ? ~size_t{} >> countl_zero(n) : 1;
 }
 
-// We use 7/8th as maximum load factor.
-// For 16-wide groups, that gives an average of two empty slots per group.
+// General notes on capacity/growth methods below:
+// - We use 7/8th as maximum load factor. For 16-wide groups, that gives an
+//   average of two empty slots per group.
+// - For (capacity+1) >= Group::kWidth, growth is 7/8*capacity.
+// - For (capacity+1) < Group::kWidth, growth == capacity. In this case, we
+//   never need to probe (the whole table fits in one group) so we don't need a
+//   load factor less than 1.
+
+// Given `capacity` of the table, returns the size (i.e. number of full slots)
+// at which we should grow the capacity.
 inline size_t CapacityToGrowth(size_t capacity) {
   assert(IsValidCapacity(capacity));
   // `capacity*7/8`
@@ -480,7 +488,7 @@ inline size_t CapacityToGrowth(size_t capacity) {
   return capacity - capacity / 8;
 }
 // From desired "growth" to a lowerbound of the necessary capacity.
-// Might not be a valid one and required NormalizeCapacity().
+// Might not be a valid one and requires NormalizeCapacity().
 inline size_t GrowthToLowerboundCapacity(size_t growth) {
   // `growth*8/7`
   if (Group::kWidth == 8 && growth == 7) {