Adds a modified copy of talk/base to webrtc/base. It is the first step in migrating talk/base to webrtc/base.

BUG=N/A
R=andrew@webrtc.org, wu@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/12199004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6107 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/base/worker.cc

@@ -0,0 +1,75 @@
+/*
+ *  Copyright 2004 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/worker.h"
+
+#include "webrtc/base/common.h"
+#include "webrtc/base/logging.h"
+#include "webrtc/base/thread.h"
+
+namespace rtc {
+
+enum {
+  MSG_HAVEWORK = 0,
+};
+
+Worker::Worker() : worker_thread_(NULL) {}
+
+Worker::~Worker() {
+  // We need to already be stopped before being destroyed. We cannot call
+  // StopWork() from here because the subclass's data has already been
+  // destructed, so OnStop() cannot be called.
+  ASSERT(!worker_thread_);
+}
+
+bool Worker::StartWork() {
+  rtc::Thread *me = rtc::Thread::Current();
+  if (worker_thread_) {
+    if (worker_thread_ == me) {
+      // Already working on this thread, so nothing to do.
+      return true;
+    } else {
+      LOG(LS_ERROR) << "Automatically switching threads is not supported";
+      ASSERT(false);
+      return false;
+    }
+  }
+  worker_thread_ = me;
+  OnStart();
+  return true;
+}
+
+bool Worker::StopWork() {
+  if (!worker_thread_) {
+    // Already not working, so nothing to do.
+    return true;
+  } else if (worker_thread_ != rtc::Thread::Current()) {
+    LOG(LS_ERROR) << "Stopping from a different thread is not supported";
+    ASSERT(false);
+    return false;
+  }
+  OnStop();
+  worker_thread_->Clear(this, MSG_HAVEWORK);
+  worker_thread_ = NULL;
+  return true;
+}
+
+void Worker::HaveWork() {
+  ASSERT(worker_thread_ != NULL);
+  worker_thread_->Post(this, MSG_HAVEWORK);
+}
+
+void Worker::OnMessage(rtc::Message *msg) {
+  ASSERT(msg->message_id == MSG_HAVEWORK);
+  ASSERT(worker_thread_ == rtc::Thread::Current());
+  OnHaveWork();
+}
+
+}  // namespace rtc