Export of internal Abseil changes

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9fc37c11b9e46287acef00ee06ed9adcba54dd13 by Greg Falcon <gfalcon@google.com>:

Rename absl::hash_internal::HashState to absl::hash_internal::MixingHashState.

Before this change, we had two classes named HashState: absl::HashState, the public API used for type erasure, and absl::hash_internal::HashState, the internal concrete implementation ordinarily used.

The internal class used to be named `CityHashState`, but we renamed it to `HashState` it when we changed underlying hash implementation to wyhash.  This inadvertent naming conflict made the code much harder to read, and this change intends to undo that.

PiperOrigin-RevId: 373481959

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4aec55ffddebd085c239352a2e20721091f719a1 by Greg Falcon <gfalcon@google.com>:

Introduce absl::HashOf(), a convenience wrapper around absl::Hash that calculates hashes from the values of its arguments.

PiperOrigin-RevId: 373461406

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86b5fd8db50bbc8bd0aa9258523527381fe0445d by Abseil Team <absl-team@google.com>:

Improve speed of BlockingCounter by making its most common path lock free.

With the new implementation, the fast path of BlockingCounter::DecrementCount()
is only a fetch_sub operation. This is most times much more efficient than the
previous implementation (full mutex lock/unlock). As a matter of fact, in most
actual usecases in practice, the waiter thread is already waiting on the
Wait() call when DecrementCount() is called, which makes Mutex::Unlock() take
the slow path as there's a waiter thread that it might need to wake up.

PiperOrigin-RevId: 373394164

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65c876be5eac0cd32583ff8535ede4109d39cf3f by Martijn Vels <mvels@google.com>:

Move the 'sample copied cord' logic into MaybeTrackCord(),

This changes move the logic for selecting if a cord should remain being sampled from Cord to CordzInfo::MaybeTrackCord, and updates the documentation for the latter method.

PiperOrigin-RevId: 373363168

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e84410bd0aada293a81dfb82656c952e209e21fb by Martijn Vels <mvels@google.com>:

Add check for the first call to cordz_should_profile() for each thread.

This prevents the first cord of a newly created thread to be always sampled, which is a 'bad' kind of determinism for sampling.

PiperOrigin-RevId: 373229768

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bf09c589dc099ac8f4af780bf7e609c53c27574c by Samuel Benzaquen <sbenza@google.com>:

Refactor the Flags structure into an enum.
This gives us more control over the representation and allows for easier
merging during parsing.

PiperOrigin-RevId: 373163038

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b947b0c51083b7b6508284b5d31819596c91729e by Derek Mauro <dmauro@google.com>:

Fixes warnings about shadowed variables
Fixes #956

PiperOrigin-RevId: 373158133
GitOrigin-RevId: 9fc37c11b9e46287acef00ee06ed9adcba54dd13
Change-Id: I91f35699f9bf439d1a870c6493946a310afe088c

1 files changed, 22 insertions, 0 deletions

diff --git a/absl/hash/hash_test.cc b/absl/hash/hash_test.cc
index 1d2e6cf0..02b7733d 100644
--- a/absl/hash/hash_test.cc
+++ b/absl/hash/hash_test.cc
@@ -973,4 +973,26 @@ TEST(HashTest, DoesNotUseImplicitConversionsToBool) {
             absl::Hash<ValueWithBoolConversion>()(ValueWithBoolConversion{1}));
 }
 
+TEST(HashOf, MatchesHashForSingleArgument) {
+  std::string s = "forty two";
+  int i = 42;
+  double d = 42.0;
+  std::tuple<int, int> t{4, 2};
+
+  EXPECT_EQ(absl::HashOf(s), absl::Hash<std::string>{}(s));
+  EXPECT_EQ(absl::HashOf(i), absl::Hash<int>{}(i));
+  EXPECT_EQ(absl::HashOf(d), absl::Hash<double>{}(d));
+  EXPECT_EQ(absl::HashOf(t), (absl::Hash<std::tuple<int, int>>{}(t)));
+}
+
+TEST(HashOf, MatchesHashOfTupleForMultipleArguments) {
+  std::string hello = "hello";
+  std::string world = "world";
+
+  EXPECT_EQ(absl::HashOf(), absl::HashOf(std::make_tuple()));
+  EXPECT_EQ(absl::HashOf(hello), absl::HashOf(std::make_tuple(hello)));
+  EXPECT_EQ(absl::HashOf(hello, world),
+            absl::HashOf(std::make_tuple(hello, world)));
+}
+
 }  // namespace