The Tor Browser: security/sandbox/chromium/base/threading/thread_local

     1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.

     2 // Use of this source code is governed by a BSD-style license that can be

     3 // found in the LICENSE file.

     5 #ifndef BASE_THREADING_THREAD_LOCAL_STORAGE_H_

     6 #define BASE_THREADING_THREAD_LOCAL_STORAGE_H_

     8 #include "base/base_export.h"

     9 #include "base/basictypes.h"

    11 #if defined(OS_POSIX)

    12 #include <pthread.h>

    13 #endif

    15 namespace base {

    17 // Wrapper for thread local storage.  This class doesn't do much except provide

    18 // an API for portability.

    19 class BASE_EXPORT ThreadLocalStorage {

    20  public:

    22   // Prototype for the TLS destructor function, which can be optionally used to

    23   // cleanup thread local storage on thread exit.  'value' is the data that is

    24   // stored in thread local storage.

    25   typedef void (*TLSDestructorFunc)(void* value);

    27   // StaticSlot uses its own struct initializer-list style static

    28   // initialization, as base's LINKER_INITIALIZED requires a constructor and on

    29   // some compilers (notably gcc 4.4) this still ends up needing runtime

    30   // initialization.

    31   #define TLS_INITIALIZER {0}

    33   // A key representing one value stored in TLS.

    34   // Initialize like

    35   //   ThreadLocalStorage::StaticSlot my_slot = TLS_INITIALIZER;

    36   // If you're not using a static variable, use the convenience class

    37   // ThreadLocalStorage::Slot (below) instead.

    38   struct BASE_EXPORT StaticSlot {

    39     // Set up the TLS slot.  Called by the constructor.

    40     // 'destructor' is a pointer to a function to perform per-thread cleanup of

    41     // this object.  If set to NULL, no cleanup is done for this TLS slot.

    42     // Returns false on error.

    43     bool Initialize(TLSDestructorFunc destructor);

    45     // Free a previously allocated TLS 'slot'.

    46     // If a destructor was set for this slot, removes

    47     // the destructor so that remaining threads exiting

    48     // will not free data.

    49     void Free();

    51     // Get the thread-local value stored in slot 'slot'.

    52     // Values are guaranteed to initially be zero.

    53     void* Get() const;

    55     // Set the thread-local value stored in slot 'slot' to

    56     // value 'value'.

    57     void Set(void* value);

    59     bool initialized() const { return initialized_; }

    61     // The internals of this struct should be considered private.

    62     bool initialized_;

    63 #if defined(OS_WIN)

    64     int slot_;

    65 #elif defined(OS_POSIX)

    66     pthread_key_t key_;

    67 #endif

    69   };

    71   // A convenience wrapper around StaticSlot with a constructor. Can be used

    72   // as a member variable.

    73   class BASE_EXPORT Slot : public StaticSlot {

    74    public:

    75     // Calls StaticSlot::Initialize().

    76     explicit Slot(TLSDestructorFunc destructor = NULL);

    78    private:

    79     using StaticSlot::initialized_;

    80 #if defined(OS_WIN)

    81     using StaticSlot::slot_;

    82 #elif defined(OS_POSIX)

    83     using StaticSlot::key_;

    84 #endif

    85     DISALLOW_COPY_AND_ASSIGN(Slot);

    86   };

    88   DISALLOW_COPY_AND_ASSIGN(ThreadLocalStorage);

    89 };

    91 }  // namespace base

    93 #endif  // BASE_THREADING_THREAD_LOCAL_STORAGE_H_

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