Export of internal Abseil changes

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d56207f5535c3aad1624e33d20777ea6e66f51a7 by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 397830482

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7f7ff3e88e0d3cd61d63da477b2a08e61a1aeea2 by Evan Brown <ezb@google.com>:

Update implementation details comment in raw_hash_set to include information about the heap allocation's layout.

PiperOrigin-RevId: 397786239

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fde783b12a79ae8d587d1027bc8736dff6844897 by Abseil Team <absl-team@google.com>:

Add comments on #endif to make nesting clearer

PiperOrigin-RevId: 397684219
GitOrigin-RevId: d56207f5535c3aad1624e33d20777ea6e66f51a7
Change-Id: I43dc2b5c982f1ef2b21f82b6133c49c428baf223

1 files changed, 11 insertions, 0 deletions

diff --git a/absl/container/internal/raw_hash_set.h b/absl/container/internal/raw_hash_set.h
index 212052ea..5c5db12e 100644
--- a/absl/container/internal/raw_hash_set.h
+++ b/absl/container/internal/raw_hash_set.h
@@ -87,6 +87,17 @@
 //
 // This probing function guarantees that after N probes, all the groups of the
 // table will be probed exactly once.
+//
+// The control state and slot array are stored contiguously in a shared heap
+// allocation. The layout of this allocation is: `capacity()` control bytes,
+// one sentinel control byte, `Group::kWidth - 1` cloned control bytes,
+// <possible padding>, `capacity()` slots. The sentinel control byte is used in
+// iteration so we know when we reach the end of the table. The cloned control
+// bytes at the end of the table are cloned from the beginning of the table so
+// groups that begin near the end of the table can see a full group. In cases in
+// which there are more than `capacity()` cloned control bytes, the extra bytes
+// are `kEmpty`, and these ensure that we always see at least one empty slot and
+// can stop an unsuccessful search.
 
 #ifndef ABSL_CONTAINER_INTERNAL_RAW_HASH_SET_H_
 #define ABSL_CONTAINER_INTERNAL_RAW_HASH_SET_H_