base/threading/platform_thread.h

   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.
   4
   5 // WARNING: You should *NOT* be using this class directly.  PlatformThread is
   6 // the low-level platform-specific abstraction to the OS's threading interface.
   7 // You should instead be using a message-loop driven Thread, see thread.h.
   8
   9 #ifndef BASE_THREADING_PLATFORM_THREAD_H_
  10 #define BASE_THREADING_PLATFORM_THREAD_H_
  11
  12 #include "base/base_export.h"
  13 #include "base/basictypes.h"
  14 #include "base/time.h"
  15 #include "build/build_config.h"
  16
  17 #if defined(OS_WIN)
  18 #include <windows.h>
  19 #elif defined(OS_POSIX)
  20 #include <pthread.h>
  21 #include <unistd.h>
  22 #endif
  23
  24 namespace base {
  25
  26 // PlatformThreadHandle should not be assumed to be a numeric type, since the
  27 // standard intends to allow pthread_t to be a structure.  This means you
  28 // should not initialize it to a value, like 0.  If it's a member variable, the
  29 // constructor can safely "value initialize" using () in the initializer list.
  30 #if defined(OS_WIN)
  31 typedef DWORD PlatformThreadId;
  32 typedef void* PlatformThreadHandle;  // HANDLE
  33 const PlatformThreadHandle kNullThreadHandle = NULL;
  34 #elif defined(OS_POSIX)
  35 typedef pthread_t PlatformThreadHandle;
  36 const PlatformThreadHandle kNullThreadHandle = 0;
  37 typedef pid_t PlatformThreadId;
  38 #endif
  39
  40 const PlatformThreadId kInvalidThreadId = 0;
  41
  42 // Valid values for SetThreadPriority()
  43 enum ThreadPriority{
  44   kThreadPriority_Normal,
  45   // Suitable for low-latency, glitch-resistant audio.
  46   kThreadPriority_RealtimeAudio
  47 };
  48
  49 // A namespace for low-level thread functions.
  50 class BASE_EXPORT PlatformThread {
  51  public:
  52   // Implement this interface to run code on a background thread.  Your
  53   // ThreadMain method will be called on the newly created thread.
  54   class BASE_EXPORT Delegate {
  55    public:
  56     virtual void ThreadMain() = 0;
  57
  58    protected:
  59     virtual ~Delegate() {}
  60   };
  61
  62   // Gets the current thread id, which may be useful for logging purposes.
  63   static PlatformThreadId CurrentId();
  64
  65   // Yield the current thread so another thread can be scheduled.
  66   static void YieldCurrentThread();
  67
  68   // Sleeps for the specified duration.
  69   static void Sleep(base::TimeDelta duration);
  70
  71   // Sets the thread name visible to debuggers/tools. This has no effect
  72   // otherwise. This name pointer is not copied internally. Thus, it must stay
  73   // valid until the thread ends.
  74   static void SetName(const char* name);
  75
  76   // Gets the thread name, if previously set by SetName.
  77   static const char* GetName();
  78
  79   // Creates a new thread.  The |stack_size| parameter can be 0 to indicate
  80   // that the default stack size should be used.  Upon success,
  81   // |*thread_handle| will be assigned a handle to the newly created thread,
  82   // and |delegate|'s ThreadMain method will be executed on the newly created
  83   // thread.
  84   // NOTE: When you are done with the thread handle, you must call Join to
  85   // release system resources associated with the thread.  You must ensure that
  86   // the Delegate object outlives the thread.
  87   static bool Create(size_t stack_size, Delegate* delegate,
  88                      PlatformThreadHandle* thread_handle);
  89
  90   // CreateWithPriority() does the same thing as Create() except the priority of
  91   // the thread is set based on |priority|.  Can be used in place of Create()
  92   // followed by SetThreadPriority().  SetThreadPriority() has not been
  93   // implemented on the Linux platform yet, this is the only way to get a high
  94   // priority thread on Linux.
  95   static bool CreateWithPriority(size_t stack_size, Delegate* delegate,
  96                                  PlatformThreadHandle* thread_handle,
  97                                  ThreadPriority priority);
  98
  99   // CreateNonJoinable() does the same thing as Create() except the thread
 100   // cannot be Join()'d.  Therefore, it also does not output a
 101   // PlatformThreadHandle.
 102   static bool CreateNonJoinable(size_t stack_size, Delegate* delegate);
 103
 104   // Joins with a thread created via the Create function.  This function blocks
 105   // the caller until the designated thread exits.  This will invalidate
 106   // |thread_handle|.
 107   static void Join(PlatformThreadHandle thread_handle);
 108
 109   // Sets the priority of the thread specified in |handle| to |priority|.
 110   // This does not work on Linux, use CreateWithPriority() instead.
 111   static void SetThreadPriority(PlatformThreadHandle handle,
 112                                 ThreadPriority priority);
 113
 114  private:
 115   DISALLOW_IMPLICIT_CONSTRUCTORS(PlatformThread);
 116 };
 117
 118 }  // namespace base
 119
 120 #endif  // BASE_THREADING_PLATFORM_THREAD_H_