Add Darwin thread.h implementation.

webrtc/base/thread_darwin.mm

+/*
+ *  Copyright 2017 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/base/thread.h"
+
+#import <Foundation/Foundation.h>
+
+#include "webrtc/base/platform_thread.h"
+
+/*
+ * This file contains platform-specific implementations for several
+ * methods in rtc::Thread.
+ */
+
+namespace {
+void InitCocoaMultiThreading() {
+  if ([NSThread isMultiThreaded] == NO) {
+    // The sole purpose of this autorelease pool is to avoid a console
+    // message on Leopard that tells us we're autoreleasing the thread
+    // with no autorelease pool in place.
+    @autoreleasepool {
+      [NSThread detachNewThreadSelector:@selector(class)
+                               toTarget:[NSObject class]
+                             withObject:nil];
+    }
+  }
+
+  RTC_DCHECK([NSThread isMultiThreaded]);
+}
+}
+
+namespace rtc {
+
+ThreadManager::ThreadManager() {
+  pthread_key_create(&key_, nullptr);
+#ifndef NO_MAIN_THREAD_WRAPPING
+  WrapCurrentThread();
+#endif
+  // This is necessary to alert the cocoa runtime of the fact that
+  // we are running in a multithreaded environment.
+  InitCocoaMultiThreading();
+}
+
+ThreadManager::~ThreadManager() {
+  @autoreleasepool {
+    UnwrapCurrentThread();
+    pthread_key_delete(key_);
+  }
+}
+
+// static
+void* Thread::PreRun(void* pv) {
+  ThreadInit* init = static_cast<ThreadInit*>(pv);
+  ThreadManager::Instance()->SetCurrentThread(init->thread);
+  rtc::SetCurrentThreadName(init->thread->name_.c_str());
+  @autoreleasepool {
+    if (init->runnable) {
+      init->runnable->Run(init->thread);
+    } else {
+      init->thread->Run();
+    }
+  }
+  delete init;
+  return nullptr;
+}
+
+bool Thread::ProcessMessages(int cmsLoop) {
+  int64_t msEnd = (kForever == cmsLoop) ? 0 : TimeAfter(cmsLoop);
+  int cmsNext = cmsLoop;
+
+  while (true) {
+    @autoreleasepool {
+      Message msg;
+      if (!Get(&msg, cmsNext))
+        return !IsQuitting();
+      Dispatch(&msg);
+
+      if (cmsLoop != kForever) {
+        cmsNext = static_cast<int>(TimeUntil(msEnd));
+        if (cmsNext < 0)
+          return true;
+      }
+    }
+  }
+}
+}  // namespace rtc