base: Support setting thread priorities generically.

base/threading/platform_thread.h

Index: base/threading/platform_thread.h
diff --git a/base/threading/platform_thread.h b/base/threading/platform_thread.h
index 576695a4e7b5f8028f47cc5e02921b551ffb0a39..c021f1a834c86758c271e1cfdb2b2747ae17521f 100644
--- a/base/threading/platform_thread.h
+++ b/base/threading/platform_thread.h
@@ -19,6 +19,7 @@
 #elif defined(OS_POSIX)
 #include <pthread.h>
 #include <unistd.h>
+#include <ostream>

[jar (doing other things), 2013/05/15 02:18:36]

nit: probably alphabetize by placing before line 20.

[epennerAtGoogle, 2013/05/15 05:09:08]

Done. I actually removed this.

[epenner, 2013/05/17 19:18:13]

I went ahead and removed this.

 #endif
 
 namespace base {
@@ -32,9 +33,48 @@ typedef DWORD PlatformThreadId;
 typedef void* PlatformThreadHandle;  // HANDLE
 const PlatformThreadHandle kNullThreadHandle = NULL;
 #elif defined(OS_POSIX)
-typedef pthread_t PlatformThreadHandle;
-const PlatformThreadHandle kNullThreadHandle = 0;
 typedef pid_t PlatformThreadId;
+struct PlatformThreadHandle {

[jar (doing other things), 2013/05/15 02:18:36]

nit: this should probably be a class.

You'll probably want a copy constructors and such.

[epennerAtGoogle, 2013/05/15 05:09:08]

I made it a class to protect members, but default copy seems okay?

[epenner, 2013/05/17 19:18:13]

I made it into a class to protect private members, but default copy constructor
etc. is fine?

+  PlatformThreadHandle()
+    : handle(),
+      id(0) {
+  }
+
+  PlatformThreadHandle(pthread_t handle)

[jar (doing other things), 2013/05/15 02:18:36]

nit: explicit.

[epennerAtGoogle, 2013/05/15 05:09:08]

Done.

[epenner, 2013/05/17 19:18:13]

Done.

+    : handle(handle),
+      id(0) {
+  }
+
+  PlatformThreadHandle(pthread_t handle,
+                       PlatformThreadId id)
+    : handle(handle),
+      id(id) {
+  }
+
+  operator bool() const {
+    return !!handle;
+  }
+
+  bool operator!() {

[jar (doing other things), 2013/05/15 02:18:36]

Instead of operator overload, use method names, like IsNull()

[epennerAtGoogle, 2013/05/15 05:09:08]

I couldn't do this because the handle on windows was an integer type. So I have
now refactored windows also uses this container (and changed all call sites).

Done.

+    return !handle;
+  }
+
+  bool operator==(const PlatformThreadHandle& other) {

[jar (doing other things), 2013/05/15 02:18:36]

nit: again, just define a method name.

[epennerAtGoogle, 2013/05/15 05:09:08]

Done.

+    return handle == other.handle;
+  }
+
+  bool operator!=(const PlatformThreadHandle& other) {
+    return handle != other.handle;
+  }
+
+  pthread_t handle;
+  PlatformThreadId id;
+};
+
+const PlatformThreadHandle kNullThreadHandle(0);
+std::ostream& operator<< (std::ostream &out,

[jar (doing other things), 2013/05/15 02:18:36]

This is pretty uncommon, as use of streams is not generally endorsed.  Why did
you add this? To help with CHECK_*() calls?

[epennerAtGoogle, 2013/05/15 05:09:08]

Yes, I'm trying to remove it by changing a few call-sites.

+                          const PlatformThreadHandle& handle);
+
 #endif
 
 const PlatformThreadId kInvalidThreadId = 0;
@@ -43,7 +83,11 @@ const PlatformThreadId kInvalidThreadId = 0;
 enum ThreadPriority{
   kThreadPriority_Normal,
   // Suitable for low-latency, glitch-resistant audio.
-  kThreadPriority_RealtimeAudio
+  kThreadPriority_RealtimeAudio,
+  // Suitable for threads which generate data for the display (at ~60Hz).
+  kThreadPriority_Display,
+  // Suitable for threads that shouldn't disrupt high priority work.
+  kThreadPriority_Background
 };
 
 // A namespace for low-level thread functions.
@@ -62,6 +106,9 @@ class BASE_EXPORT PlatformThread {
   // Gets the current thread id, which may be useful for logging purposes.
   static PlatformThreadId CurrentId();
 
+  // Get the current handle.
+  static PlatformThreadHandle CurrentHandle();
+
   // Yield the current thread so another thread can be scheduled.
   static void YieldCurrentThread();
 
@@ -106,8 +153,6 @@ class BASE_EXPORT PlatformThread {
   // |thread_handle|.
   static void Join(PlatformThreadHandle thread_handle);
 
-  // Sets the priority of the thread specified in |handle| to |priority|.
-  // This does not work on Linux, use CreateWithPriority() instead.
   static void SetThreadPriority(PlatformThreadHandle handle,
                                 ThreadPriority priority);