Non-blocking audio I/O interface, WIP

Yet another abstraction similar to AudioTrack::Buffer and AudioBufferProvider,
but with support for streaming, non-blocking, and eventually PTS.

This is intended to be used as follows:
 - primary HAL output stream implements a Sink
 - primary HAL input stream implements a Source
 - Pipe implements a Sink
 - PipeReader implements a Source or TimedSource (not shown yet),
   which supports "read at PTS"
 - fast AudioTrack on server side will implement a Source using cblk
 - normal AudioTrack on server side will not be changed initially
 - fast AudioRecord on server side will implement a Sink using cblk
 - normal AudioRecord on server side will not be changed initially
 - fast mixer thread will read from Sources and write to a Sink,
   or (unlikely) implement a Source and multiple Sinks
 - Visualization and PCM logger will read from Source or TimedSource
 - A2DP normal mixer will be connected directly to its output stream
   and there will be a kind of OutputTrack for duplication that will
   read from a Sink with non-blocking write fed by the fast mixer.

Patch set 3 changes:
 - Add more implementations of NBAIO interfaces:
   added SourceAudioBufferProvider, MonoPipe, MonoPipeReader.
 - Added Format_sampleRate and Format_channelCount.
 - Extract out the roundUp() method.
 - Respond to most comments from previous code review.
 - The new classes are untested.

Patch set 4 changes:
 - Fix bugs in MonoPipe::write() and MonoPipeReader::read()
 - Fix bug initializing mFrameBitShift too early
 - renamed roundUp() to roundup()
 - Fix Android.mk
 - Add LOG_TAG an LOG_NDEBUG, use ALOG_ASSERT and utils/Log.h instead of assert
 - Fix build warnings
 - Move constructor and destructor bodies from .h to .cpp
 - Line length 100
 - Following naming conventions for #include double-include protector macros
 - Include what you use
 - More NBAIO logging
 - MonoPipe write can be blocking

Patch set 5 changes:
 - Address code review comments
 - Use a static library so unused implementations don't take memory
 - Comment out libsndfile dependency
 - Remove debugging LOGV and LOG_NDEBUG

Patch set 6 changes (would be 6 at old location, actually 2 at new location):
 - Address code review comments on patchset 5
 - For MonoPipe, allow the full pipe to be used, no need to omit one slot
 - Don't do atomic releasing stores unless needed

Still to do:
 - I'm not happy with the Pipe class names
 - Update build/ for new static library?

Change-Id: Ie6c61f05ce06b676b033be448a8ef9025a2ffcfd

1 files changed, 70 insertions, 0 deletions

diff --git a/services/audioflinger/Pipe.cpp b/services/audioflinger/Pipe.cpp
new file mode 100644
index 0000000..e5b3561
--- /dev/null
+++ b/services/audioflinger/Pipe.cpp
@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2012 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.
+ */
+
+#define LOG_TAG "Pipe"
+//#define LOG_NDEBUG 0
+
+#include <cutils/atomic.h>
+#include <cutils/compiler.h>
+#include <utils/Log.h>
+#include "Pipe.h"
+#include "roundup.h"
+
+namespace android {
+
+Pipe::Pipe(size_t maxFrames, NBAIO_Format format) :
+        NBAIO_Sink(format),
+        mMaxFrames(roundup(maxFrames)),
+        mBuffer(malloc(mMaxFrames * Format_frameSize(format))),
+        mRear(0),
+        mReaders(0)
+{
+}
+
+Pipe::~Pipe()
+{
+    ALOG_ASSERT(android_atomic_acquire_load(&mReaders) == 0);
+    free(mBuffer);
+}
+
+ssize_t Pipe::write(const void *buffer, size_t count)
+{
+    // count == 0 is unlikely and not worth checking for
+    if (CC_UNLIKELY(!mNegotiated)) {
+        return NEGOTIATE;
+    }
+    // write() is not multi-thread safe w.r.t. itself, so no mutex or atomic op needed to read mRear
+    size_t rear = mRear & (mMaxFrames - 1);
+    size_t written = mMaxFrames - rear;
+    if (CC_LIKELY(written > count)) {
+        written = count;
+    }
+    memcpy((char *) mBuffer + (rear << mBitShift), buffer, written << mBitShift);
+    if (CC_UNLIKELY(rear + written == mMaxFrames)) {
+        if (CC_UNLIKELY((count -= written) > rear)) {
+            count = rear;
+        }
+        if (CC_LIKELY(count > 0)) {
+            memcpy(mBuffer, (char *) buffer + (written << mBitShift), count << mBitShift);
+            written += count;
+        }
+    }
+    android_atomic_release_store(written + mRear, &mRear);
+    mFramesWritten += written;
+    return written;
+}
+
+}   // namespace android