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/**********************************************************************
Audacity: A Digital Audio Editor
@file AudioGraphTask.cpp
Dominic Mazzoni
Vaughan Johnson
Martyn Shaw
Paul Licameli split from PerTrackEffect.cpp
**********************************************************************/
#include "AudioGraphTask.h"
#include "AudioGraphBuffers.h"
#include "AudioGraphSink.h"
#include "AudioGraphSource.h"
#include "SampleCount.h"
#include <cassert>
AudioGraph::Task::Task(Source &source, Buffers &buffers, Sink &sink)
: mSource{ source }, mBuffers{ buffers }, mSink{ sink }
{
assert(source.AcceptsBlockSize(buffers.BlockSize()));
assert(source.AcceptsBuffers(buffers));
assert(sink.AcceptsBuffers(buffers));
}
bool AudioGraph::Task::RunLoop()
{
// Satisfy invariant initially
mBuffers.Rewind();
Status status{};
do {
assert(mBuffers.Remaining() >= mBuffers.BlockSize());
status = RunOnce();
} while (status == Status::More);
return status == Status::Done;
}
auto AudioGraph::Task::RunOnce() -> Status
{
const auto blockSize = mBuffers.BlockSize();
assert(mBuffers.Remaining() >= blockSize); // pre
#ifndef NDEBUG
// Variable used only for a loop termination sanity check
std::optional<sampleCount> oldRemaining;
if (mRanOnce)
oldRemaining.emplace(mSource.Remaining());
// else Remaining() may not be meaningful
#endif
if (auto oCurBlockSize = mSource.Acquire(mBuffers, blockSize)) {
const auto curBlockSize = *oCurBlockSize;
#ifndef NDEBUG
mRanOnce = true;
const auto remaining = mSource.Remaining();
// Assert a post of Acquire which is part of proof of termination
assert(!mSource.Terminates() || !oldRemaining ||
*oldRemaining == remaining);
oldRemaining.emplace(remaining);
// Assert another post that guarantees progress (even if not terminating)
assert(blockSize == 0 || remaining == 0 || curBlockSize > 0);
#endif
if (curBlockSize == 0)
// post (same as pre) obviously preserved
return Status::Done;
// post of source.Acquire() satisfies pre of sink.Release()
assert(curBlockSize <= blockSize);
if (!mSink.Release(mBuffers, curBlockSize))
return Status::Fail;
// This may break the post
mBuffers.Advance(curBlockSize);
// posts of source.Acquire() and source.Release()
// give termination guarantee
assert(mSource.Remaining() == 0 || curBlockSize > 0);
if (!mSource.Release())
return Status::Fail;
#ifndef NDEBUG
// Assert a post of Release
assert(!mSource.Terminates() ||
mSource.Remaining() == remaining - curBlockSize);
#endif
// Reestablish the post
if (!mSink.Acquire(mBuffers))
return Status::Fail;
assert(mBuffers.Remaining() >= blockSize);
return Status::More;
}
else
return Status::Fail;
}
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