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/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 #if defined(OS_WIN)
  27 typedef DWORD PlatformThreadId;
  28 #elif defined(OS_POSIX)
  29 typedef pid_t PlatformThreadId;
  30 #endif
  31
  32 class PlatformThreadHandle {
  33  public:
  34 #if defined(OS_WIN)
  35   typedef void* Handle;
  36 #elif defined(OS_POSIX)
  37   typedef pthread_t Handle;
  38 #endif
  39
  40   PlatformThreadHandle()
  41       : handle_(0),
  42         id_(0) {
  43   }
  44
  45   explicit PlatformThreadHandle(Handle handle)
  46       : handle_(handle),
  47         id_(0) {
  48   }
  49
  50   PlatformThreadHandle(Handle handle,
  51                        PlatformThreadId id)
  52       : handle_(handle),
  53         id_(id) {
  54   }
  55
  56   bool is_equal(const PlatformThreadHandle& other) {
  57     return handle_ == other.handle_;
  58   }
  59
  60   bool is_null() {
  61     return !handle_;
  62   }
  63
  64   Handle platform_handle() {
  65     return handle_;
  66   }
  67
  68  private:
  69   friend class PlatformThread;
  70
  71   Handle handle_;
  72   PlatformThreadId id_;
  73 };
  74
  75 const PlatformThreadId kInvalidThreadId(0);
  76
  77 // Valid values for SetThreadPriority()
  78 enum ThreadPriority{
  79   kThreadPriority_Normal,
  80   // Suitable for low-latency, glitch-resistant audio.
  81   kThreadPriority_RealtimeAudio,
  82   // Suitable for threads which generate data for the display (at ~60Hz).
  83   kThreadPriority_Display,
  84   // Suitable for threads that shouldn't disrupt high priority work.
  85   kThreadPriority_Background
  86 };
  87
  88 // A namespace for low-level thread functions.
  89 class BASE_EXPORT PlatformThread {
  90  public:
  91   // Implement this interface to run code on a background thread.  Your
  92   // ThreadMain method will be called on the newly created thread.
  93   class BASE_EXPORT Delegate {
  94    public:
  95     virtual void ThreadMain() = 0;
  96
  97    protected:
  98     virtual ~Delegate() {}
  99   };
 100
 101   // Gets the current thread id, which may be useful for logging purposes.
 102   static PlatformThreadId CurrentId();
 103
 104   // Get the current handle.
 105   static PlatformThreadHandle CurrentHandle();
 106
 107   // Yield the current thread so another thread can be scheduled.
 108   static void YieldCurrentThread();
 109
 110   // Sleeps for the specified duration.
 111   static void Sleep(base::TimeDelta duration);
 112
 113   // Sets the thread name visible to debuggers/tools. This has no effect
 114   // otherwise. This name pointer is not copied internally. Thus, it must stay
 115   // valid until the thread ends.
 116   static void SetName(const char* name);
 117
 118   // Gets the thread name, if previously set by SetName.
 119   static const char* GetName();
 120
 121   // Creates a new thread.  The |stack_size| parameter can be 0 to indicate
 122   // that the default stack size should be used.  Upon success,
 123   // |*thread_handle| will be assigned a handle to the newly created thread,
 124   // and |delegate|'s ThreadMain method will be executed on the newly created
 125   // thread.
 126   // NOTE: When you are done with the thread handle, you must call Join to
 127   // release system resources associated with the thread.  You must ensure that
 128   // the Delegate object outlives the thread.
 129   static bool Create(size_t stack_size, Delegate* delegate,
 130                      PlatformThreadHandle* thread_handle);
 131
 132   // CreateWithPriority() does the same thing as Create() except the priority of
 133   // the thread is set based on |priority|.  Can be used in place of Create()
 134   // followed by SetThreadPriority().  SetThreadPriority() has not been
 135   // implemented on the Linux platform yet, this is the only way to get a high
 136   // priority thread on Linux.
 137   static bool CreateWithPriority(size_t stack_size, Delegate* delegate,
 138                                  PlatformThreadHandle* thread_handle,
 139                                  ThreadPriority priority);
 140
 141   // CreateNonJoinable() does the same thing as Create() except the thread
 142   // cannot be Join()'d.  Therefore, it also does not output a
 143   // PlatformThreadHandle.
 144   static bool CreateNonJoinable(size_t stack_size, Delegate* delegate);
 145
 146   // Joins with a thread created via the Create function.  This function blocks
 147   // the caller until the designated thread exits.  This will invalidate
 148   // |thread_handle|.
 149   static void Join(PlatformThreadHandle thread_handle);
 150
 151   static void SetThreadPriority(PlatformThreadHandle handle,
 152                                 ThreadPriority priority);
 153
 154  private:
 155   DISALLOW_IMPLICIT_CONSTRUCTORS(PlatformThread);
 156 };
 157
 158 }  // namespace base
 159
 160 #endif  // BASE_THREADING_PLATFORM_THREAD_H_