Initial work

external/android-emugl/shared/emugl/common/message_channel.cpp

@@ -0,0 +1,64 @@
+// 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