70 lines
2.4 KiB
C++
70 lines
2.4 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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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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* http://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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#pragma once
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#include <cstdint>
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namespace folly {
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/**
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* Get a process-specific identifier for the current thread.
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*
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* The return value will uniquely identify the thread within the current
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* process.
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*
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* Note that the return value does not necessarily correspond to an operating
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* system thread ID. The return value is also only unique within the current
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* process: getCurrentThreadID() may return the same value for two concurrently
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* running threads in separate processes.
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*
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* The thread ID may be reused once the thread it corresponds to has been
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* joined.
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*/
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uint64_t getCurrentThreadID();
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/**
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* Get the operating-system level thread ID for the current thread.
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*
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* The returned value will uniquely identify this thread on the system.
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*
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* This makes it more suitable for logging or displaying in user interfaces
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* than the result of getCurrentThreadID().
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*
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* There are some potential caveats about this API, however:
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*
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* - In theory there is no guarantee that application threads map one-to-one to
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* kernel threads. An application threading implementation could potentially
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* share one OS thread across multiple application threads, and/or it could
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* potentially move application threads between different OS threads over
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* time. However, in practice all of the platforms we currently support have
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* a one-to-one mapping between userspace threads and operating system
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* threads.
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*
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* - This API may also be slightly slower than getCurrentThreadID() on some
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* platforms. This API may require a system call, where getCurrentThreadID()
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* may only need to read thread-local memory.
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*
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* On Linux the returned value is a pid_t, and can be used in contexts
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* requiring a thread pid_t.
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*
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* The thread ID may be reused once the thread it corresponds to has been
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* joined.
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*/
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uint64_t getOSThreadID();
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} // namespace folly
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