94 lines
2.8 KiB
C++
94 lines
2.8 KiB
C++
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_THREADING_THREAD_LOCAL_STORAGE_H_
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#define BASE_THREADING_THREAD_LOCAL_STORAGE_H_
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#include "base/base_export.h"
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#include "base/basictypes.h"
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#if defined(OS_POSIX)
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#include <pthread.h>
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#endif
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namespace base {
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// Wrapper for thread local storage. This class doesn't do much except provide
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// an API for portability.
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class BASE_EXPORT ThreadLocalStorage {
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public:
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// Prototype for the TLS destructor function, which can be optionally used to
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// cleanup thread local storage on thread exit. 'value' is the data that is
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// stored in thread local storage.
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typedef void (*TLSDestructorFunc)(void* value);
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// StaticSlot uses its own struct initializer-list style static
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// initialization, as base's LINKER_INITIALIZED requires a constructor and on
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// some compilers (notably gcc 4.4) this still ends up needing runtime
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// initialization.
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#define TLS_INITIALIZER {0}
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// A key representing one value stored in TLS.
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// Initialize like
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// ThreadLocalStorage::StaticSlot my_slot = TLS_INITIALIZER;
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// If you're not using a static variable, use the convenience class
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// ThreadLocalStorage::Slot (below) instead.
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struct BASE_EXPORT StaticSlot {
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// Set up the TLS slot. Called by the constructor.
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// 'destructor' is a pointer to a function to perform per-thread cleanup of
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// this object. If set to NULL, no cleanup is done for this TLS slot.
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// Returns false on error.
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bool Initialize(TLSDestructorFunc destructor);
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// Free a previously allocated TLS 'slot'.
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// If a destructor was set for this slot, removes
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// the destructor so that remaining threads exiting
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// will not free data.
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void Free();
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// Get the thread-local value stored in slot 'slot'.
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// Values are guaranteed to initially be zero.
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void* Get() const;
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// Set the thread-local value stored in slot 'slot' to
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// value 'value'.
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void Set(void* value);
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bool initialized() const { return initialized_; }
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// The internals of this struct should be considered private.
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bool initialized_;
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#if defined(OS_WIN)
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int slot_;
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#elif defined(OS_POSIX)
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pthread_key_t key_;
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#endif
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};
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// A convenience wrapper around StaticSlot with a constructor. Can be used
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// as a member variable.
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class BASE_EXPORT Slot : public StaticSlot {
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public:
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// Calls StaticSlot::Initialize().
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explicit Slot(TLSDestructorFunc destructor = NULL);
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private:
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using StaticSlot::initialized_;
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#if defined(OS_WIN)
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using StaticSlot::slot_;
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#elif defined(OS_POSIX)
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using StaticSlot::key_;
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#endif
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DISALLOW_COPY_AND_ASSIGN(Slot);
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};
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DISALLOW_COPY_AND_ASSIGN(ThreadLocalStorage);
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};
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} // namespace base
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#endif // BASE_THREADING_THREAD_LOCAL_STORAGE_H_
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