tor-browser

The Tor Browser
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thread_local_storage.h (2994B)

      1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
      2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
      3 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
      4 // Use of this source code is governed by a BSD-style license that can be
      5 // found in the LICENSE file.
      6 
      7 #ifndef BASE_THREAD_LOCAL_STORAGE_H_
      8 #define BASE_THREAD_LOCAL_STORAGE_H_
      9 
     10 #include "base/basictypes.h"
     11 
     12 #if defined(XP_UNIX)
     13 #  include <pthread.h>
     14 #endif
     15 
     16 // Wrapper for thread local storage.  This class doesn't do much except provide
     17 // an API for portability.
     18 class ThreadLocalStorage {
     19 public:
     20  // Prototype for the TLS destructor function, which can be optionally used to
     21  // cleanup thread local storage on thread exit.  'value' is the data that is
     22  // stored in thread local storage.
     23  typedef void (*TLSDestructorFunc)(void* value);
     24 
     25  // A key representing one value stored in TLS.
     26  class Slot {
     27   public:
     28    explicit Slot(TLSDestructorFunc destructor = NULL);
     29 
     30    // This constructor should be used for statics.
     31    // It returns an uninitialized Slot.
     32    explicit Slot(base::LinkerInitialized x) {}
     33 
     34    // Set up the TLS slot.  Called by the constructor.
     35    // 'destructor' is a pointer to a function to perform per-thread cleanup of
     36    // this object.  If set to NULL, no cleanup is done for this TLS slot.
     37    // Returns false on error.
     38    bool Initialize(TLSDestructorFunc destructor);
     39 
     40    // Free a previously allocated TLS 'slot'.
     41    // If a destructor was set for this slot, removes
     42    // the destructor so that remaining threads exiting
     43    // will not free data.
     44    void Free();
     45 
     46    // Get the thread-local value stored in slot 'slot'.
     47    // Values are guaranteed to initially be zero.
     48    void* Get() const;
     49 
     50    // Set the thread-local value stored in slot 'slot' to
     51    // value 'value'.
     52    void Set(void* value);
     53 
     54    bool initialized() const { return initialized_; }
     55 
     56   private:
     57    // The internals of this struct should be considered private.
     58    bool initialized_;
     59 #if defined(XP_WIN)
     60    int slot_;
     61 #else
     62    pthread_key_t key_;
     63 #endif
     64 
     65    DISALLOW_COPY_AND_ASSIGN(Slot);
     66  };
     67 
     68 #if defined(XP_WIN)
     69  // Function called when on thread exit to call TLS
     70  // destructor functions.  This function is used internally.
     71  static void ThreadExit();
     72 
     73 private:
     74  // Function to lazily initialize our thread local storage.
     75  static void** Initialize();
     76 
     77 private:
     78  // The maximum number of 'slots' in our thread local storage stack.
     79  // For now, this is fixed.  We could either increase statically, or
     80  // we could make it dynamic in the future.
     81  static const int kThreadLocalStorageSize = 64;
     82 
     83  static long tls_key_;
     84  static long tls_max_;
     85  static TLSDestructorFunc tls_destructors_[kThreadLocalStorageSize];
     86 #endif  // XP_WIN
     87 
     88  DISALLOW_COPY_AND_ASSIGN(ThreadLocalStorage);
     89 };
     90 
     91 // Temporary backwards-compatible name.
     92 // TODO(evanm): replace all usage of TLSSlot.
     93 typedef ThreadLocalStorage::Slot TLSSlot;
     94 
     95 #endif  // BASE_THREAD_LOCAL_STORAGE_H_