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* Copyright (C) 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include "Configuration.h"
namespace android {
// Describes the underrun status for a single "pull" attempt
enum FastTrackUnderrunStatus {
UNDERRUN_FULL, // framesReady() is full frame count, no underrun
UNDERRUN_PARTIAL, // framesReady() is non-zero but < full frame count, partial underrun
UNDERRUN_EMPTY, // framesReady() is zero, total underrun
// Underrun counters are not reset to zero for new tracks or if track generation changes.
// This packed representation is used to keep the information atomic.
union FastTrackUnderruns {
FastTrackUnderruns() { mAtomic = 0;
COMPILE_TIME_ASSERT_FUNCTION_SCOPE(sizeof(FastTrackUnderruns) == sizeof(uint32_t)); }
FastTrackUnderruns(const FastTrackUnderruns& copyFrom) : mAtomic(copyFrom.mAtomic) { }
FastTrackUnderruns& operator=(const FastTrackUnderruns& rhs)
{ if (this != &rhs) mAtomic = rhs.mAtomic; return *this; }
struct {
#define UNDERRUN_BITS 10
#define UNDERRUN_MASK ((1 << UNDERRUN_BITS) - 1)
uint32_t mFull : UNDERRUN_BITS; // framesReady() is full frame count
uint32_t mPartial : UNDERRUN_BITS; // framesReady() is non-zero but < full frame count
uint32_t mEmpty : UNDERRUN_BITS; // framesReady() is zero
FastTrackUnderrunStatus mMostRecent : 2; // status of most recent framesReady()
} mBitFields;
uint32_t mAtomic;
// Represents the dump state of a fast track
struct FastTrackDump {
FastTrackDump() : mFramesReady(0) { }
/*virtual*/ ~FastTrackDump() { }
FastTrackUnderruns mUnderruns;
size_t mFramesReady; // most recent value only; no long-term statistics kept
// The FastMixerDumpState keeps a cache of FastMixer statistics that can be logged by dumpsys.
// Each individual native word-sized field is accessed atomically. But the
// overall structure is non-atomic, that is there may be an inconsistency between fields.
// No barriers or locks are used for either writing or reading.
// Only POD types are permitted, and the contents shouldn't be trusted (i.e. do range checks).
// It has a different lifetime than the FastMixer, and so it can't be a member of FastMixer.
struct FastMixerDumpState : FastThreadDumpState {
uint32_t samplingN = kSamplingNforLowRamDevice
/*virtual*/ ~FastMixerDumpState();
void dump(int fd) const; // should only be called on a stable copy, not the original
uint32_t mWriteSequence; // incremented before and after each write()
uint32_t mFramesWritten; // total number of frames written successfully
uint32_t mNumTracks; // total number of active fast tracks
uint32_t mWriteErrors; // total number of write() errors
uint32_t mSampleRate;
size_t mFrameCount;
uint32_t mTrackMask; // mask of active tracks
FastTrackDump mTracks[FastMixerState::kMaxFastTracks];
// Compile-time constant for a "low RAM device", must be a power of 2 <= kSamplingN.
// This value was chosen such that each array uses 1 small page (4 Kbytes).
static const uint32_t kSamplingNforLowRamDevice = 0x400;
// Increase sampling window after construction, must be a power of 2 <= kSamplingN
void increaseSamplingN(uint32_t samplingN);
} // android