nsresult
SourceBufferResource::Seek(int32_t aWhence, int64_t aOffset)
{
SBR_DEBUG("Seek(aWhence=%d, aOffset=%lld)",
aWhence, aOffset);
ReentrantMonitorAutoEnter mon(mMonitor);
int64_t newOffset = mOffset;
switch (aWhence) {
case nsISeekableStream::NS_SEEK_END:
newOffset = GetLength() - aOffset;
break;
case nsISeekableStream::NS_SEEK_CUR:
newOffset += aOffset;
break;
case nsISeekableStream::NS_SEEK_SET:
newOffset = aOffset;
break;
}
SBR_DEBUGV("newOffset=%lld GetOffset()=%llu GetLength()=%llu)",
newOffset, mInputBuffer.GetOffset(), GetLength());
nsresult rv = SeekInternal(newOffset);
mon.NotifyAll();
return rv;
}
nsresult
SourceBufferResource::Read(char* aBuffer, uint32_t aCount, uint32_t* aBytes)
{
SBR_DEBUGV("Read(aBuffer=%p, aCount=%u, aBytes=%p)",
aBuffer, aCount, aBytes);
ReentrantMonitorAutoEnter mon(mMonitor);
return ReadInternal(aBuffer, aCount, aBytes, /* aMayBlock = */ true);
}
nsresult
SourceBufferResource::ReadInternal(char* aBuffer, uint32_t aCount, uint32_t* aBytes, bool aMayBlock)
{
mMonitor.AssertCurrentThreadIn();
MOZ_ASSERT_IF(!aMayBlock, aBytes);
// Cache the offset for the read in case mOffset changes while waiting on the
// monitor below. It's basically impossible to implement these API semantics
// sanely. :-(
uint64_t readOffset = mOffset;
while (aMayBlock &&
!mEnded &&
readOffset + aCount > static_cast<uint64_t>(GetLength())) {
SBR_DEBUGV("waiting for data");
mMonitor.Wait();
// The callers of this function should have checked this, but it's
// possible that we had an eviction while waiting on the monitor.
if (readOffset < mInputBuffer.GetOffset()) {
return NS_ERROR_FAILURE;
}
}
uint32_t available = GetLength() - readOffset;
uint32_t count = std::min(aCount, available);
SBR_DEBUGV("readOffset=%llu GetLength()=%u available=%u count=%u mEnded=%d",
readOffset, GetLength(), available, count, mEnded);
if (available == 0) {
SBR_DEBUGV("reached EOF");
*aBytes = 0;
return NS_OK;
}
mInputBuffer.CopyData(readOffset, count, aBuffer);
*aBytes = count;
// From IRC:
// <@cpearce>bholley: *this* is why there should only every be a ReadAt() and
// no Read() on a Stream abstraction! there's no good answer, they all suck.
mOffset = readOffset + count;
return NS_OK;
}