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// Copyright (c) 2006-2008 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_THREAD_LOCAL_STORAGE_H_
#define BASE_THREAD_LOCAL_STORAGE_H_
#include "base/basictypes.h"
#if defined(OS_POSIX)
#include <pthread.h>
#endif
// Wrapper for thread local storage. This class doesn't do much except provide
// an API for portability.
class 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);
// A key representing one value stored in TLS.
class Slot {
public:
explicit Slot(TLSDestructorFunc destructor = NULL);
// This constructor should be used for statics.
// It returns an uninitialized Slot.
explicit Slot(base::LinkerInitialized x) {}
// 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_; }
private:
// 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
DISALLOW_COPY_AND_ASSIGN(Slot);
};
#if defined(OS_WIN)
// Function called when on thread exit to call TLS
// destructor functions. This function is used internally.
static void ThreadExit();
private:
// Function to lazily initialize our thread local storage.
static void **Initialize();
private:
// The maximum number of 'slots' in our thread local storage stack.
// For now, this is fixed. We could either increase statically, or
// we could make it dynamic in the future.
static const int kThreadLocalStorageSize = 64;
static long tls_key_;
static long tls_max_;
static TLSDestructorFunc tls_destructors_[kThreadLocalStorageSize];
#endif // OS_WIN
DISALLOW_COPY_AND_ASSIGN(ThreadLocalStorage);
};
// Temporary backwards-compatible name.
// TODO(evanm): replace all usage of TLSSlot.
typedef ThreadLocalStorage::Slot TLSSlot;
#endif // BASE_THREAD_LOCAL_STORAGE_H_
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