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