1e39f8626a
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b842b7fd9b1289be31f0b7ee8e62e48e550747cf by Greg Falcon <gfalcon@google.com>:
Change the Cord str_format formatter to use iteration instead of CordReader.
When Cord is publicly released, CordReader is not going with it.
PiperOrigin-RevId: 284780736
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28e76c08ea7185a7ff9f4e0e02ae565fbbf7980f by Greg Falcon <gfalcon@google.com>:
Implementation detail change.
Introduce ABSL_NAMESPACE_BEGIN and _END annotation macros which indicate the beginning and end of a `namespace absl` scope. Currently these do nothing, but they will be used to inject an inline namespace for LTS builds (to avoid symbol collisions against other Abseil versions).
These macros should not be used by end users, because end users should never write `namespace absl {` in their own code.
This CL applies these annotations to all code under //absl/base/. The rest of Abseil will be annotated in this way in follow-up CLs.
PiperOrigin-RevId: 284776410
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e1711dc6d696dcca50d4e7d4b4d8f3076575b7ec by Abseil Team <absl-team@google.com>:
--help changed to report long flags.
PiperOrigin-RevId: 284757720
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78f66a68f428bbbd19d8d60e1125f43ba765fd35 by Tom Manshreck <shreck@google.com>:
Update comment on + or - in SimpleAToi()
PiperOrigin-RevId: 284231843
GitOrigin-RevId: b842b7fd9b1289be31f0b7ee8e62e48e550747cf
Change-Id: I3046b31391bd11c8bc4abab7785a863c377cd757
94 lines
3.3 KiB
C++
94 lines
3.3 KiB
C++
//
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// Copyright 2017 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// -----------------------------------------------------------------------------
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// File: cycleclock.h
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// -----------------------------------------------------------------------------
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//
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// This header file defines a `CycleClock`, which yields the value and frequency
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// of a cycle counter that increments at a rate that is approximately constant.
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//
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// NOTE:
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//
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// The cycle counter frequency is not necessarily related to the core clock
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// frequency and should not be treated as such. That is, `CycleClock` cycles are
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// not necessarily "CPU cycles" and code should not rely on that behavior, even
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// if experimentally observed.
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//
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// An arbitrary offset may have been added to the counter at power on.
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//
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// On some platforms, the rate and offset of the counter may differ
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// slightly when read from different CPUs of a multiprocessor. Usually,
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// we try to ensure that the operating system adjusts values periodically
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// so that values agree approximately. If you need stronger guarantees,
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// consider using alternate interfaces.
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//
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// The CPU is not required to maintain the ordering of a cycle counter read
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// with respect to surrounding instructions.
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#ifndef ABSL_BASE_INTERNAL_CYCLECLOCK_H_
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#define ABSL_BASE_INTERNAL_CYCLECLOCK_H_
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#include <cstdint>
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#include "absl/base/config.h"
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace base_internal {
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// -----------------------------------------------------------------------------
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// CycleClock
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// -----------------------------------------------------------------------------
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class CycleClock {
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public:
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// CycleClock::Now()
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//
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// Returns the value of a cycle counter that counts at a rate that is
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// approximately constant.
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static int64_t Now();
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// CycleClock::Frequency()
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//
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// Returns the amount by which `CycleClock::Now()` increases per second. Note
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// that this value may not necessarily match the core CPU clock frequency.
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static double Frequency();
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private:
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CycleClock() = delete; // no instances
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CycleClock(const CycleClock&) = delete;
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CycleClock& operator=(const CycleClock&) = delete;
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};
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using CycleClockSourceFunc = int64_t (*)();
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class CycleClockSource {
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private:
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// CycleClockSource::Register()
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//
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// Register a function that provides an alternate source for the unscaled CPU
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// cycle count value. The source function must be async signal safe, must not
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// call CycleClock::Now(), and must have a frequency that matches that of the
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// unscaled clock used by CycleClock. A nullptr value resets CycleClock to use
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// the default source.
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static void Register(CycleClockSourceFunc source);
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};
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} // namespace base_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_BASE_INTERNAL_CYCLECLOCK_H_
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