Export of internal Abseil changes

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a9ac6567c0933d786d68c10011e3f3ff9deedf89 by Greg Falcon <gfalcon@google.com>:

Add absl::FunctionRef, a type analogous to the proposed C++23 std::function_ref.

Like std::function, FunctionRef can be used to type-erase any callable (invokable) object.  However, FunctionRef works by reference: it does not store a copy of the type-erased object.  If the wrapped object is destroyed before the FunctionRef, the reference becomes dangling.

FunctionRef relates to std::function in much the same way that string_view relates to std::string.

Because of these limitations, FunctionRef is best used only as a function argument type, and only where the function will be invoked immediately (rather than saved for later use).  When `const std::function<...>&` is used in this way, `absl::FunctionRef<...>` is a better-performing replacement.

PiperOrigin-RevId: 275484044

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1f7c4df3760f8b93e5a5baf40b070eca1d3f4c98 by Abseil Team <absl-team@google.com>:

Add FastHexToBufferZeroPad16() function for blazingly fast hex encoding of uint64_t.

PiperOrigin-RevId: 275420901

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08d48ac004eba57cf2f1ada827181a2995f74807 by Abseil Team <absl-team@google.com>:

Avoid applying the workaround for MSVC's static initialization problems when using clang-cl.

PiperOrigin-RevId: 275366326

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40be82bd2b34670b5458c0a72a0475086153c2d6 by Abseil Team <absl-team@google.com>:

Added comments to SimpleAtof()/SimpleAtod() that clarify that they
always use the "C" locale, unlike the standard functions strtod()
and strtof() referenced now in the comments.

PiperOrigin-RevId: 275355815

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086779dacb3f6f2b3ab59947e94e79046bdb1fe1 by Jorg Brown <jorg@google.com>:

Move the hex conversion table used by escaping.cc into numbers.h so
that other parts of Abseil can more efficiently access it.

PiperOrigin-RevId: 275331251

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3c4ed1b04e55d96a40cbe70fb70929ffbb0c0432 by Abseil Team <absl-team@google.com>:

Avoid applying the workaround for MSVC's static initialization problems when using clang-cl.

PiperOrigin-RevId: 275323858

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56ceb58ab688c3761978308609b09a1ac2739c9a by Derek Mauro <dmauro@google.com>:

Add script for testing on Alpine Linux (for musl test coverage)

PiperOrigin-RevId: 275321244
GitOrigin-RevId: a9ac6567c0933d786d68c10011e3f3ff9deedf89
Change-Id: I39799fa03768ddb44f3166200c860e1da4461807

1 files changed, 28 insertions, 2 deletions

diff --git a/absl/strings/numbers_test.cc b/absl/strings/numbers_test.cc
index d964e562..b92b9a8c 100644
--- a/absl/strings/numbers_test.cc
+++ b/absl/strings/numbers_test.cc
@@ -17,6 +17,7 @@
 #include "absl/strings/numbers.h"
 
 #include <sys/types.h>
+
 #include <cfenv>  // NOLINT(build/c++11)
 #include <cinttypes>
 #include <climits>
@@ -36,10 +37,11 @@
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include "absl/base/internal/raw_logging.h"
-#include "absl/strings/str_cat.h"
-
+#include "absl/random/distributions.h"
+#include "absl/random/random.h"
 #include "absl/strings/internal/numbers_test_common.h"
 #include "absl/strings/internal/pow10_helper.h"
+#include "absl/strings/str_cat.h"
 
 namespace {
 
@@ -1187,4 +1189,28 @@ TEST(StrToUint64Base, PrefixOnly) {
   }
 }
 
+void TestFastHexToBufferZeroPad16(uint64_t v) {
+  char buf[16];
+  auto digits = absl::numbers_internal::FastHexToBufferZeroPad16(v, buf);
+  absl::string_view res(buf, 16);
+  char buf2[17];
+  snprintf(buf2, sizeof(buf2), "%016" PRIx64, v);
+  EXPECT_EQ(res, buf2) << v;
+  size_t expected_digits = snprintf(buf2, sizeof(buf2), "%" PRIx64, v);
+  EXPECT_EQ(digits, expected_digits) << v;
+}
+
+TEST(FastHexToBufferZeroPad16, Smoke) {
+  TestFastHexToBufferZeroPad16(std::numeric_limits<uint64_t>::min());
+  TestFastHexToBufferZeroPad16(std::numeric_limits<uint64_t>::max());
+  TestFastHexToBufferZeroPad16(std::numeric_limits<int64_t>::min());
+  TestFastHexToBufferZeroPad16(std::numeric_limits<int64_t>::max());
+  absl::BitGen rng;
+  for (int i = 0; i < 100000; ++i) {
+    TestFastHexToBufferZeroPad16(
+        absl::LogUniform(rng, std::numeric_limits<uint64_t>::min(),
+                         std::numeric_limits<uint64_t>::max()));
+  }
+}
+
 }  // namespace