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 // Used for logging. Always an integer value.
  27 #if defined(OS_WIN)
  28 typedef DWORD PlatformThreadId;
  29 #elif defined(OS_POSIX)
  30 typedef pid_t PlatformThreadId;
  31 #endif
  32
  33 // Used for thread checking and debugging.
  34 // Meant to be as fast as possible.
  35 // These are produced by PlatformThread::CurrentRef(), and used to later
  36 // check if we are on the same thread or not by using ==. These are safe
  37 // to copy between threads, but can't be copied to another process as they
  38 // have no meaning there. Also, the internal identifier can be re-used
  39 // after a thread dies, so a PlatformThreadRef cannot be reliably used
  40 // to distinguish a new thread from an old, dead thread.
  41 class PlatformThreadRef {
  42  public:
  43 #if defined(OS_WIN)
  44   typedef DWORD RefType;
  45 #elif defined(OS_POSIX)
  46   typedef pthread_t RefType;
  47 #endif
  48   PlatformThreadRef()
  49       : id_(0) {
  50   }
  51
  52   explicit PlatformThreadRef(RefType id)
  53       : id_(id) {
  54   }
  55
  56   bool operator==(PlatformThreadRef other) const {
  57     return id_ == other.id_;
  58   }
  59
  60   bool is_null() const {
  61     return id_ == 0;
  62   }
  63  private:
  64   RefType id_;
  65 };
  66
  67 // Used to operate on threads.
  68 class PlatformThreadHandle {
  69  public:
  70 #if defined(OS_WIN)
  71   typedef void* Handle;
  72 #elif defined(OS_POSIX)
  73   typedef pthread_t Handle;
  74 #endif
  75
  76   PlatformThreadHandle()
  77       : handle_(0),
  78         id_(0) {
  79   }
  80
  81   explicit PlatformThreadHandle(Handle handle)
  82       : handle_(handle),
  83         id_(0) {
  84   }
  85
  86   PlatformThreadHandle(Handle handle,
  87                        PlatformThreadId id)
  88       : handle_(handle),
  89         id_(id) {
  90   }
  91
  92   bool is_equal(const PlatformThreadHandle& other) const {
  93     return handle_ == other.handle_;
  94   }
  95
  96   bool is_null() const {
  97     return !handle_;
  98   }
  99
 100   Handle platform_handle() const {
 101     return handle_;
 102   }
 103
 104  private:
 105   friend class PlatformThread;
 106
 107   Handle handle_;
 108   PlatformThreadId id_;
 109 };
 110
 111 const PlatformThreadId kInvalidThreadId(0);
 112
 113 // Valid values for SetThreadPriority()
 114 enum ThreadPriority{
 115   kThreadPriority_Normal,
 116   // Suitable for low-latency, glitch-resistant audio.
 117   kThreadPriority_RealtimeAudio,
 118   // Suitable for threads which generate data for the display (at ~60Hz).
 119   kThreadPriority_Display,
 120   // Suitable for threads that shouldn't disrupt high priority work.
 121   kThreadPriority_Background
 122 };
 123
 124 // A namespace for low-level thread functions.
 125 class BASE_EXPORT PlatformThread {
 126  public:
 127   // Implement this interface to run code on a background thread.  Your
 128   // ThreadMain method will be called on the newly created thread.
 129   class BASE_EXPORT Delegate {
 130    public:
 131     virtual void ThreadMain() = 0;
 132
 133    protected:
 134     virtual ~Delegate() {}
 135   };
 136
 137   // Gets the current thread id, which may be useful for logging purposes.
 138   static PlatformThreadId CurrentId();
 139
 140   // Gets the current thread reference, which can be used to check if
 141   // we're on the right thread quickly.
 142   static PlatformThreadRef CurrentRef();
 143
 144   // Get the current handle.
 145   static PlatformThreadHandle CurrentHandle();
 146
 147   // Yield the current thread so another thread can be scheduled.
 148   static void YieldCurrentThread();
 149
 150   // Sleeps for the specified duration.
 151   static void Sleep(base::TimeDelta duration);
 152
 153   // Sets the thread name visible to debuggers/tools. This has no effect
 154   // otherwise. This name pointer is not copied internally. Thus, it must stay
 155   // valid until the thread ends.
 156   static void SetName(const char* name);
 157
 158   // Gets the thread name, if previously set by SetName.
 159   static const char* GetName();
 160
 161   // Creates a new thread.  The |stack_size| parameter can be 0 to indicate
 162   // that the default stack size should be used.  Upon success,
 163   // |*thread_handle| will be assigned a handle to the newly created thread,
 164   // and |delegate|'s ThreadMain method will be executed on the newly created
 165   // thread.
 166   // NOTE: When you are done with the thread handle, you must call Join to
 167   // release system resources associated with the thread.  You must ensure that
 168   // the Delegate object outlives the thread.
 169   static bool Create(size_t stack_size, Delegate* delegate,
 170                      PlatformThreadHandle* thread_handle);
 171
 172   // CreateWithPriority() does the same thing as Create() except the priority of
 173   // the thread is set based on |priority|.  Can be used in place of Create()
 174   // followed by SetThreadPriority().  SetThreadPriority() has not been
 175   // implemented on the Linux platform yet, this is the only way to get a high
 176   // priority thread on Linux.
 177   static bool CreateWithPriority(size_t stack_size, Delegate* delegate,
 178                                  PlatformThreadHandle* thread_handle,
 179                                  ThreadPriority priority);
 180
 181   // CreateNonJoinable() does the same thing as Create() except the thread
 182   // cannot be Join()'d.  Therefore, it also does not output a
 183   // PlatformThreadHandle.
 184   static bool CreateNonJoinable(size_t stack_size, Delegate* delegate);
 185
 186   // Joins with a thread created via the Create function.  This function blocks
 187   // the caller until the designated thread exits.  This will invalidate
 188   // |thread_handle|.
 189   static void Join(PlatformThreadHandle thread_handle);
 190
 191   static void SetThreadPriority(PlatformThreadHandle handle,
 192                                 ThreadPriority priority);
 193
 194  private:
 195   DISALLOW_IMPLICIT_CONSTRUCTORS(PlatformThread);
 196 };
 197
 198 }  // namespace base
 199
 200 #endif  // BASE_THREADING_PLATFORM_THREAD_H_