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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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// This file includes routines to find out characteristics
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// of the machine a program is running on. It is undoubtedly
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// system-dependent.
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// Functions listed here that accept a pid_t as an argument act on the
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// current process if the pid_t argument is 0
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// All functions here are thread-hostile due to file caching unless
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// commented otherwise.
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#ifndef ABSL_BASE_INTERNAL_SYSINFO_H_
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#define ABSL_BASE_INTERNAL_SYSINFO_H_
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#ifndef _WIN32
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#include <sys/types.h>
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#endif
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#include <cstdint>
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#include "absl/base/config.h"
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#include "absl/base/port.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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// Nominal core processor cycles per second of each processor. This is _not_
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// necessarily the frequency of the CycleClock counter (see cycleclock.h)
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// Thread-safe.
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double NominalCPUFrequency();
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// Number of logical processors (hyperthreads) in system. Thread-safe.
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int NumCPUs();
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// Return the thread id of the current thread, as told by the system.
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// No two currently-live threads implemented by the OS shall have the same ID.
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// Thread ids of exited threads may be reused. Multiple user-level threads
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// may have the same thread ID if multiplexed on the same OS thread.
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//
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// On Linux, you may send a signal to the resulting ID with kill(). However,
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// it is recommended for portability that you use pthread_kill() instead.
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#ifdef _WIN32
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// On Windows, process id and thread id are of the same type according to the
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// return types of GetProcessId() and GetThreadId() are both DWORD, an unsigned
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// 32-bit type.
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using pid_t = uint32_t;
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#endif
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pid_t GetTID();
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// Like GetTID(), but caches the result in thread-local storage in order
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// to avoid unnecessary system calls. Note that there are some cases where
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// one must call through to GetTID directly, which is why this exists as a
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// separate function. For example, GetCachedTID() is not safe to call in
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// an asynchronous signal-handling context nor right after a call to fork().
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pid_t GetCachedTID();
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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_SYSINFO_H_
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