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, 80 insertions, 0 deletions

diff --git a/services/audioflinger/LibsndfileSource.cpp b/services/audioflinger/LibsndfileSource.cpp
new file mode 100644
index 0000000..28317d6
--- /dev/null
+++ b/services/audioflinger/LibsndfileSource.cpp
@@ -0,0 +1,80 @@
+/*
+ * 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 "LibsndfileSource"
+//#define LOG_NDEBUG 0
+
+#include <utils/Errors.h>
+#include <utils/Log.h>
+#include "LibsndfileSource.h"
+
+namespace android {
+
+LibsndfileSource::LibsndfileSource(SNDFILE *sndfile, const SF_INFO &sfinfo, bool loop) :
+    NBAIO_Source(Format_from_SR_C(sfinfo.samplerate, sfinfo.channels)),
+    mSndfile(sndfile),
+    mEstimatedFramesUntilEOF(sfinfo.frames),
+    mLooping(loop && sfinfo.seekable),
+    mReadAnyFramesThisLoopCycle(false)
+{
+}
+
+LibsndfileSource::~LibsndfileSource()
+{
+    // do not close mSndfile; we don't own it
+}
+
+ssize_t LibsndfileSource::availableToRead()
+{
+    // after we reach the presumed EOF, report infinity just in case there's actually more
+    return !mLooping && mEstimatedFramesUntilEOF > 0 ? mEstimatedFramesUntilEOF : SSIZE_MAX;
+}
+
+ssize_t LibsndfileSource::read(void *buffer, size_t count)
+{
+    if (!mNegotiated) {
+        return (ssize_t) NEGOTIATE;
+    }
+    if (mSndfile == NULL) {
+        return (ssize_t) NO_INIT;
+    }
+    sf_count_t actual = sf_readf_short(mSndfile, (short *) buffer, (sf_count_t) count);
+    // Detect EOF by zero frames read, not by mFramesUntilEOF as it could be inaccurate
+    if (actual == 0) {
+        if (mLooping) {
+            if (mReadAnyFramesThisLoopCycle) {
+                (void) sf_seek(mSndfile, (sf_count_t) 0, SEEK_SET);
+                mReadAnyFramesThisLoopCycle = false;
+            } else {
+                // We didn't read any frames during the current loop cycle, so disable
+                // further looping to prevent the caller from busy waiting at read().
+                // This is especially important when looping an empty file.
+                mLooping = false;
+            }
+        }
+    } else {
+        mFramesRead += actual;
+        if (actual >= mEstimatedFramesUntilEOF) {
+            mEstimatedFramesUntilEOF = 0;
+        } else {
+            mEstimatedFramesUntilEOF -= actual;
+        }
+        mReadAnyFramesThisLoopCycle = true;
+    }
+    return actual;
+}
+
+}   // namespace android