--- /dev/null
+// Copyright 2014 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "emugl/common/message_channel.h"
+
+namespace emugl {
+
+MessageChannelBase::MessageChannelBase(size_t capacity) :
+ mPos(0U),
+ mCount(0U),
+ mCapacity(capacity),
+ mLock(),
+ mCanRead(),
+ mCanWrite() {}
+
+MessageChannelBase::~MessageChannelBase() {}
+
+size_t MessageChannelBase::beforeWrite() {
+ mLock.lock();
+ while (mCount >= mCapacity) {
+ mCanWrite.wait(&mLock);
+ }
+ size_t result = mPos + mCount;
+ if (result >= mCapacity) {
+ result -= mCapacity;
+ }
+ return result;
+}
+
+void MessageChannelBase::afterWrite() {
+ mCount++;
+ mCanRead.signal();
+ mLock.unlock();
+}
+
+size_t MessageChannelBase::beforeRead() {
+ mLock.lock();
+ while (mCount == 0) {
+ mCanRead.wait(&mLock);
+ }
+ return mPos;
+}
+
+void MessageChannelBase::afterRead() {
+ if (++mPos == mCapacity) {
+ mPos = 0U;
+ }
+ mCount--;
+ mCanWrite.signal();
+ mLock.unlock();
+}
+
+} // namespace emugl