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-rw-r--r--image/SourceBuffer.cpp700
1 files changed, 700 insertions, 0 deletions
diff --git a/image/SourceBuffer.cpp b/image/SourceBuffer.cpp
new file mode 100644
index 0000000000..cb7b1c178a
--- /dev/null
+++ b/image/SourceBuffer.cpp
@@ -0,0 +1,700 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SourceBuffer.h"
+
+#include <algorithm>
+#include <cmath>
+#include <cstring>
+#include "mozilla/Likely.h"
+#include "nsIInputStream.h"
+#include "MainThreadUtils.h"
+#include "SurfaceCache.h"
+
+using std::max;
+using std::min;
+
+namespace mozilla {
+namespace image {
+
+//////////////////////////////////////////////////////////////////////////////
+// SourceBufferIterator implementation.
+//////////////////////////////////////////////////////////////////////////////
+
+SourceBufferIterator::~SourceBufferIterator() {
+ if (mOwner) {
+ mOwner->OnIteratorRelease();
+ }
+}
+
+SourceBufferIterator& SourceBufferIterator::operator=(
+ SourceBufferIterator&& aOther) {
+ if (mOwner) {
+ mOwner->OnIteratorRelease();
+ }
+
+ mOwner = std::move(aOther.mOwner);
+ mState = aOther.mState;
+ mData = aOther.mData;
+ mChunkCount = aOther.mChunkCount;
+ mByteCount = aOther.mByteCount;
+ mRemainderToRead = aOther.mRemainderToRead;
+
+ return *this;
+}
+
+SourceBufferIterator::State SourceBufferIterator::AdvanceOrScheduleResume(
+ size_t aRequestedBytes, IResumable* aConsumer) {
+ MOZ_ASSERT(mOwner);
+
+ if (MOZ_UNLIKELY(!HasMore())) {
+ MOZ_ASSERT_UNREACHABLE("Should not advance a completed iterator");
+ return COMPLETE;
+ }
+
+ // The range of data [mOffset, mOffset + mNextReadLength) has just been read
+ // by the caller (or at least they don't have any interest in it), so consume
+ // that data.
+ MOZ_ASSERT(mData.mIterating.mNextReadLength <=
+ mData.mIterating.mAvailableLength);
+ mData.mIterating.mOffset += mData.mIterating.mNextReadLength;
+ mData.mIterating.mAvailableLength -= mData.mIterating.mNextReadLength;
+
+ // An iterator can have a limit imposed on it to read only a subset of a
+ // source buffer. If it is present, we need to mimic the same behaviour as
+ // the owning SourceBuffer.
+ if (MOZ_UNLIKELY(mRemainderToRead != SIZE_MAX)) {
+ MOZ_ASSERT(mData.mIterating.mNextReadLength <= mRemainderToRead);
+ mRemainderToRead -= mData.mIterating.mNextReadLength;
+
+ if (MOZ_UNLIKELY(mRemainderToRead == 0)) {
+ mData.mIterating.mNextReadLength = 0;
+ SetComplete(NS_OK);
+ return COMPLETE;
+ }
+
+ if (MOZ_UNLIKELY(aRequestedBytes > mRemainderToRead)) {
+ aRequestedBytes = mRemainderToRead;
+ }
+ }
+
+ mData.mIterating.mNextReadLength = 0;
+
+ if (MOZ_LIKELY(mState == READY)) {
+ // If the caller wants zero bytes of data, that's easy enough; we just
+ // configured ourselves for a zero-byte read above! In theory we could do
+ // this even in the START state, but it's not important for performance and
+ // breaking the ability of callers to assert that the pointer returned by
+ // Data() is non-null doesn't seem worth it.
+ if (aRequestedBytes == 0) {
+ MOZ_ASSERT(mData.mIterating.mNextReadLength == 0);
+ return READY;
+ }
+
+ // Try to satisfy the request out of our local buffer. This is potentially
+ // much faster than requesting data from our owning SourceBuffer because we
+ // don't have to take the lock. Note that if we have anything at all in our
+ // local buffer, we use it to satisfy the request; @aRequestedBytes is just
+ // the *maximum* number of bytes we can return.
+ if (mData.mIterating.mAvailableLength > 0) {
+ return AdvanceFromLocalBuffer(aRequestedBytes);
+ }
+ }
+
+ // Our local buffer is empty, so we'll have to request data from our owning
+ // SourceBuffer.
+ return mOwner->AdvanceIteratorOrScheduleResume(*this, aRequestedBytes,
+ aConsumer);
+}
+
+bool SourceBufferIterator::RemainingBytesIsNoMoreThan(size_t aBytes) const {
+ MOZ_ASSERT(mOwner);
+ return mOwner->RemainingBytesIsNoMoreThan(*this, aBytes);
+}
+
+//////////////////////////////////////////////////////////////////////////////
+// SourceBuffer implementation.
+//////////////////////////////////////////////////////////////////////////////
+
+const size_t SourceBuffer::MIN_CHUNK_CAPACITY;
+const size_t SourceBuffer::MAX_CHUNK_CAPACITY;
+
+SourceBuffer::SourceBuffer()
+ : mMutex("image::SourceBuffer"), mConsumerCount(0), mCompacted(false) {}
+
+SourceBuffer::~SourceBuffer() {
+ MOZ_ASSERT(mConsumerCount == 0,
+ "SourceBuffer destroyed with active consumers");
+}
+
+nsresult SourceBuffer::AppendChunk(Maybe<Chunk>&& aChunk) {
+ mMutex.AssertCurrentThreadOwns();
+
+ if (MOZ_UNLIKELY(!aChunk)) {
+ return NS_ERROR_OUT_OF_MEMORY;
+ }
+
+ if (MOZ_UNLIKELY(aChunk->AllocationFailed())) {
+ return NS_ERROR_OUT_OF_MEMORY;
+ }
+
+ if (MOZ_UNLIKELY(!mChunks.AppendElement(std::move(*aChunk), fallible))) {
+ return NS_ERROR_OUT_OF_MEMORY;
+ }
+
+ return NS_OK;
+}
+
+Maybe<SourceBuffer::Chunk> SourceBuffer::CreateChunk(
+ size_t aCapacity, size_t aExistingCapacity /* = 0 */,
+ bool aRoundUp /* = true */) {
+ if (MOZ_UNLIKELY(aCapacity == 0)) {
+ MOZ_ASSERT_UNREACHABLE("Appending a chunk of zero size?");
+ return Nothing();
+ }
+
+ // Round up if requested.
+ size_t finalCapacity = aRoundUp ? RoundedUpCapacity(aCapacity) : aCapacity;
+
+ // Use the size of the SurfaceCache as an additional heuristic to avoid
+ // allocating huge buffers. Generally images do not get smaller when decoded,
+ // so if we could store the source data in the SurfaceCache, we assume that
+ // there's no way we'll be able to store the decoded version.
+ if (MOZ_UNLIKELY(!SurfaceCache::CanHold(finalCapacity + aExistingCapacity))) {
+ NS_WARNING(
+ "SourceBuffer refused to create chunk too large for SurfaceCache");
+ return Nothing();
+ }
+
+ return Some(Chunk(finalCapacity));
+}
+
+nsresult SourceBuffer::Compact() {
+ mMutex.AssertCurrentThreadOwns();
+
+ MOZ_ASSERT(mConsumerCount == 0, "Should have no consumers here");
+ MOZ_ASSERT(mWaitingConsumers.Length() == 0, "Shouldn't have waiters");
+ MOZ_ASSERT(mStatus, "Should be complete here");
+
+ // If we've tried to compact once, don't attempt again.
+ if (mCompacted) {
+ return NS_OK;
+ }
+
+ mCompacted = true;
+
+ // Compact our waiting consumers list, since we're complete and no future
+ // consumer will ever have to wait.
+ mWaitingConsumers.Compact();
+
+ // If we have no chunks, then there's nothing to compact.
+ if (mChunks.Length() < 1) {
+ return NS_OK;
+ }
+
+ // If we have one chunk, then we can compact if it has excess capacity.
+ if (mChunks.Length() == 1 && mChunks[0].Length() == mChunks[0].Capacity()) {
+ return NS_OK;
+ }
+
+ // If the last chunk has the maximum capacity, then we know the total size
+ // will be quite large and not worth consolidating. We can likely/cheapily
+ // trim the last chunk if it is too big however.
+ size_t capacity = mChunks.LastElement().Capacity();
+ if (capacity == MAX_CHUNK_CAPACITY) {
+ size_t lastLength = mChunks.LastElement().Length();
+ if (lastLength != capacity) {
+ mChunks.LastElement().SetCapacity(lastLength);
+ }
+ return NS_OK;
+ }
+
+ // We can compact our buffer. Determine the total length.
+ size_t length = 0;
+ for (uint32_t i = 0; i < mChunks.Length(); ++i) {
+ length += mChunks[i].Length();
+ }
+
+ // If our total length is zero (which means ExpectLength() got called, but no
+ // data ever actually got written) then just empty our chunk list.
+ if (MOZ_UNLIKELY(length == 0)) {
+ mChunks.Clear();
+ return NS_OK;
+ }
+
+ Chunk& mergeChunk = mChunks[0];
+ if (MOZ_UNLIKELY(!mergeChunk.SetCapacity(length))) {
+ NS_WARNING("Failed to reallocate chunk for SourceBuffer compacting - OOM?");
+ return NS_OK;
+ }
+
+ // Copy our old chunks into the newly reallocated first chunk.
+ for (uint32_t i = 1; i < mChunks.Length(); ++i) {
+ size_t offset = mergeChunk.Length();
+ MOZ_ASSERT(offset < mergeChunk.Capacity());
+ MOZ_ASSERT(offset + mChunks[i].Length() <= mergeChunk.Capacity());
+
+ memcpy(mergeChunk.Data() + offset, mChunks[i].Data(), mChunks[i].Length());
+ mergeChunk.AddLength(mChunks[i].Length());
+ }
+
+ MOZ_ASSERT(mergeChunk.Length() == mergeChunk.Capacity(),
+ "Compacted chunk has slack space");
+
+ // Remove the redundant chunks.
+ mChunks.RemoveLastElements(mChunks.Length() - 1);
+ mChunks.Compact();
+
+ return NS_OK;
+}
+
+/* static */
+size_t SourceBuffer::RoundedUpCapacity(size_t aCapacity) {
+ // Protect against overflow.
+ if (MOZ_UNLIKELY(SIZE_MAX - aCapacity < MIN_CHUNK_CAPACITY)) {
+ return aCapacity;
+ }
+
+ // Round up to the next multiple of MIN_CHUNK_CAPACITY (which should be the
+ // size of a page).
+ size_t roundedCapacity =
+ (aCapacity + MIN_CHUNK_CAPACITY - 1) & ~(MIN_CHUNK_CAPACITY - 1);
+ MOZ_ASSERT(roundedCapacity >= aCapacity, "Bad math?");
+ MOZ_ASSERT(roundedCapacity - aCapacity < MIN_CHUNK_CAPACITY, "Bad math?");
+
+ return roundedCapacity;
+}
+
+size_t SourceBuffer::FibonacciCapacityWithMinimum(size_t aMinCapacity) {
+ mMutex.AssertCurrentThreadOwns();
+
+ // We grow the source buffer using a Fibonacci growth rate. It will be capped
+ // at MAX_CHUNK_CAPACITY, unless the available data exceeds that.
+
+ size_t length = mChunks.Length();
+
+ if (length == 0 || aMinCapacity > MAX_CHUNK_CAPACITY) {
+ return aMinCapacity;
+ }
+
+ if (length == 1) {
+ return min(max(2 * mChunks[0].Capacity(), aMinCapacity),
+ MAX_CHUNK_CAPACITY);
+ }
+
+ return min(
+ max(mChunks[length - 1].Capacity() + mChunks[length - 2].Capacity(),
+ aMinCapacity),
+ MAX_CHUNK_CAPACITY);
+}
+
+void SourceBuffer::AddWaitingConsumer(IResumable* aConsumer) {
+ mMutex.AssertCurrentThreadOwns();
+
+ MOZ_ASSERT(!mStatus, "Waiting when we're complete?");
+
+ if (aConsumer) {
+ mWaitingConsumers.AppendElement(aConsumer);
+ }
+}
+
+void SourceBuffer::ResumeWaitingConsumers() {
+ mMutex.AssertCurrentThreadOwns();
+
+ if (mWaitingConsumers.Length() == 0) {
+ return;
+ }
+
+ for (uint32_t i = 0; i < mWaitingConsumers.Length(); ++i) {
+ mWaitingConsumers[i]->Resume();
+ }
+
+ mWaitingConsumers.Clear();
+}
+
+nsresult SourceBuffer::ExpectLength(size_t aExpectedLength) {
+ MOZ_ASSERT(aExpectedLength > 0, "Zero expected size?");
+
+ MutexAutoLock lock(mMutex);
+
+ if (MOZ_UNLIKELY(mStatus)) {
+ MOZ_ASSERT_UNREACHABLE("ExpectLength after SourceBuffer is complete");
+ return NS_OK;
+ }
+
+ if (MOZ_UNLIKELY(mChunks.Length() > 0)) {
+ MOZ_ASSERT_UNREACHABLE("Duplicate or post-Append call to ExpectLength");
+ return NS_OK;
+ }
+
+ if (MOZ_UNLIKELY(!SurfaceCache::CanHold(aExpectedLength))) {
+ NS_WARNING("SourceBuffer refused to store too large buffer");
+ return HandleError(NS_ERROR_INVALID_ARG);
+ }
+
+ size_t length = min(aExpectedLength, MAX_CHUNK_CAPACITY);
+ if (MOZ_UNLIKELY(NS_FAILED(AppendChunk(CreateChunk(length,
+ /* aExistingCapacity */ 0,
+ /* aRoundUp */ false))))) {
+ return HandleError(NS_ERROR_OUT_OF_MEMORY);
+ }
+
+ return NS_OK;
+}
+
+nsresult SourceBuffer::Append(const char* aData, size_t aLength) {
+ MOZ_ASSERT(aData, "Should have a buffer");
+ MOZ_ASSERT(aLength > 0, "Writing a zero-sized chunk");
+
+ size_t currentChunkCapacity = 0;
+ size_t currentChunkLength = 0;
+ char* currentChunkData = nullptr;
+ size_t currentChunkRemaining = 0;
+ size_t forCurrentChunk = 0;
+ size_t forNextChunk = 0;
+ size_t nextChunkCapacity = 0;
+ size_t totalCapacity = 0;
+
+ {
+ MutexAutoLock lock(mMutex);
+
+ if (MOZ_UNLIKELY(mStatus)) {
+ // This SourceBuffer is already complete; ignore further data.
+ return NS_ERROR_FAILURE;
+ }
+
+ if (MOZ_UNLIKELY(mChunks.Length() == 0)) {
+ if (MOZ_UNLIKELY(NS_FAILED(AppendChunk(CreateChunk(aLength))))) {
+ return HandleError(NS_ERROR_OUT_OF_MEMORY);
+ }
+ }
+
+ // Copy out the current chunk's information so we can release the lock.
+ // Note that this wouldn't be safe if multiple producers were allowed!
+ Chunk& currentChunk = mChunks.LastElement();
+ currentChunkCapacity = currentChunk.Capacity();
+ currentChunkLength = currentChunk.Length();
+ currentChunkData = currentChunk.Data();
+
+ // Partition this data between the current chunk and the next chunk.
+ // (Because we always allocate a chunk big enough to fit everything passed
+ // to Append, we'll never need more than those two chunks to store
+ // everything.)
+ currentChunkRemaining = currentChunkCapacity - currentChunkLength;
+ forCurrentChunk = min(aLength, currentChunkRemaining);
+ forNextChunk = aLength - forCurrentChunk;
+
+ // If we'll need another chunk, determine what its capacity should be while
+ // we still hold the lock.
+ nextChunkCapacity =
+ forNextChunk > 0 ? FibonacciCapacityWithMinimum(forNextChunk) : 0;
+
+ for (uint32_t i = 0; i < mChunks.Length(); ++i) {
+ totalCapacity += mChunks[i].Capacity();
+ }
+ }
+
+ // Write everything we can fit into the current chunk.
+ MOZ_ASSERT(currentChunkLength + forCurrentChunk <= currentChunkCapacity);
+ memcpy(currentChunkData + currentChunkLength, aData, forCurrentChunk);
+
+ // If there's something left, create a new chunk and write it there.
+ Maybe<Chunk> nextChunk;
+ if (forNextChunk > 0) {
+ MOZ_ASSERT(nextChunkCapacity >= forNextChunk, "Next chunk too small?");
+ nextChunk = CreateChunk(nextChunkCapacity, totalCapacity);
+ if (MOZ_LIKELY(nextChunk && !nextChunk->AllocationFailed())) {
+ memcpy(nextChunk->Data(), aData + forCurrentChunk, forNextChunk);
+ nextChunk->AddLength(forNextChunk);
+ }
+ }
+
+ // Update shared data structures.
+ {
+ MutexAutoLock lock(mMutex);
+
+ // Update the length of the current chunk.
+ Chunk& currentChunk = mChunks.LastElement();
+ MOZ_ASSERT(currentChunk.Data() == currentChunkData, "Multiple producers?");
+ MOZ_ASSERT(currentChunk.Length() == currentChunkLength,
+ "Multiple producers?");
+
+ currentChunk.AddLength(forCurrentChunk);
+
+ // If we created a new chunk, add it to the series.
+ if (forNextChunk > 0) {
+ if (MOZ_UNLIKELY(!nextChunk)) {
+ return HandleError(NS_ERROR_OUT_OF_MEMORY);
+ }
+
+ if (MOZ_UNLIKELY(NS_FAILED(AppendChunk(std::move(nextChunk))))) {
+ return HandleError(NS_ERROR_OUT_OF_MEMORY);
+ }
+ }
+
+ // Resume any waiting readers now that there's new data.
+ ResumeWaitingConsumers();
+ }
+
+ return NS_OK;
+}
+
+static nsresult AppendToSourceBuffer(nsIInputStream*, void* aClosure,
+ const char* aFromRawSegment, uint32_t,
+ uint32_t aCount, uint32_t* aWriteCount) {
+ SourceBuffer* sourceBuffer = static_cast<SourceBuffer*>(aClosure);
+
+ // Copy the source data. Unless we hit OOM, we squelch the return value here,
+ // because returning an error means that ReadSegments stops reading data, and
+ // we want to ensure that we read everything we get. If we hit OOM then we
+ // return a failed status to the caller.
+ nsresult rv = sourceBuffer->Append(aFromRawSegment, aCount);
+ if (rv == NS_ERROR_OUT_OF_MEMORY) {
+ return rv;
+ }
+
+ // Report that we wrote everything we got.
+ *aWriteCount = aCount;
+
+ return NS_OK;
+}
+
+nsresult SourceBuffer::AppendFromInputStream(nsIInputStream* aInputStream,
+ uint32_t aCount) {
+ uint32_t bytesRead;
+ nsresult rv = aInputStream->ReadSegments(AppendToSourceBuffer, this, aCount,
+ &bytesRead);
+ if (NS_WARN_IF(NS_FAILED(rv))) {
+ return rv;
+ }
+
+ if (bytesRead == 0) {
+ // The loading of the image has been canceled.
+ return NS_ERROR_FAILURE;
+ }
+
+ if (bytesRead != aCount) {
+ // Only some of the given data was read. We may have failed in
+ // SourceBuffer::Append but ReadSegments swallowed the error. Otherwise the
+ // stream itself failed to yield the data.
+ MutexAutoLock lock(mMutex);
+ if (mStatus) {
+ MOZ_ASSERT(NS_FAILED(*mStatus));
+ return *mStatus;
+ }
+
+ MOZ_ASSERT_UNREACHABLE("AppendToSourceBuffer should consume everything");
+ }
+
+ return rv;
+}
+
+void SourceBuffer::Complete(nsresult aStatus) {
+ MutexAutoLock lock(mMutex);
+
+ // When an error occurs internally (e.g. due to an OOM), we save the status.
+ // This will indirectly trigger a failure higher up and that will call
+ // SourceBuffer::Complete. Since it doesn't necessarily know we are already
+ // complete, it is safe to ignore.
+ if (mStatus && (MOZ_UNLIKELY(NS_SUCCEEDED(*mStatus) ||
+ aStatus != NS_IMAGELIB_ERROR_FAILURE))) {
+ MOZ_ASSERT_UNREACHABLE("Called Complete more than once");
+ return;
+ }
+
+ if (MOZ_UNLIKELY(NS_SUCCEEDED(aStatus) && IsEmpty())) {
+ // It's illegal to succeed without writing anything.
+ aStatus = NS_ERROR_FAILURE;
+ }
+
+ mStatus = Some(aStatus);
+
+ // Resume any waiting consumers now that we're complete.
+ ResumeWaitingConsumers();
+
+ // If we still have active consumers, just return.
+ if (mConsumerCount > 0) {
+ return;
+ }
+
+ // Attempt to compact our buffer down to a single chunk.
+ Compact();
+}
+
+bool SourceBuffer::IsComplete() {
+ MutexAutoLock lock(mMutex);
+ return bool(mStatus);
+}
+
+size_t SourceBuffer::SizeOfIncludingThisWithComputedFallback(
+ MallocSizeOf aMallocSizeOf) const {
+ MutexAutoLock lock(mMutex);
+
+ size_t n = aMallocSizeOf(this);
+ n += mChunks.ShallowSizeOfExcludingThis(aMallocSizeOf);
+
+ for (uint32_t i = 0; i < mChunks.Length(); ++i) {
+ size_t chunkSize = aMallocSizeOf(mChunks[i].Data());
+
+ if (chunkSize == 0) {
+ // We're on a platform where moz_malloc_size_of always returns 0.
+ chunkSize = mChunks[i].Capacity();
+ }
+
+ n += chunkSize;
+ }
+
+ return n;
+}
+
+SourceBufferIterator SourceBuffer::Iterator(size_t aReadLength) {
+ {
+ MutexAutoLock lock(mMutex);
+ mConsumerCount++;
+ }
+
+ return SourceBufferIterator(this, aReadLength);
+}
+
+void SourceBuffer::OnIteratorRelease() {
+ MutexAutoLock lock(mMutex);
+
+ MOZ_ASSERT(mConsumerCount > 0, "Consumer count doesn't add up");
+ mConsumerCount--;
+
+ // If we still have active consumers, or we're not complete yet, then return.
+ if (mConsumerCount > 0 || !mStatus) {
+ return;
+ }
+
+ // Attempt to compact our buffer down to a single chunk.
+ Compact();
+}
+
+bool SourceBuffer::RemainingBytesIsNoMoreThan(
+ const SourceBufferIterator& aIterator, size_t aBytes) const {
+ MutexAutoLock lock(mMutex);
+
+ // If we're not complete, we always say no.
+ if (!mStatus) {
+ return false;
+ }
+
+ // If the iterator's at the end, the answer is trivial.
+ if (!aIterator.HasMore()) {
+ return true;
+ }
+
+ uint32_t iteratorChunk = aIterator.mData.mIterating.mChunk;
+ size_t iteratorOffset = aIterator.mData.mIterating.mOffset;
+ size_t iteratorLength = aIterator.mData.mIterating.mAvailableLength;
+
+ // Include the bytes the iterator is currently pointing to in the limit, so
+ // that the current chunk doesn't have to be a special case.
+ size_t bytes = aBytes + iteratorOffset + iteratorLength;
+
+ // Count the length over all of our chunks, starting with the one that the
+ // iterator is currently pointing to. (This is O(N), but N is expected to be
+ // ~1, so it doesn't seem worth caching the length separately.)
+ size_t lengthSoFar = 0;
+ for (uint32_t i = iteratorChunk; i < mChunks.Length(); ++i) {
+ lengthSoFar += mChunks[i].Length();
+ if (lengthSoFar > bytes) {
+ return false;
+ }
+ }
+
+ return true;
+}
+
+SourceBufferIterator::State SourceBuffer::AdvanceIteratorOrScheduleResume(
+ SourceBufferIterator& aIterator, size_t aRequestedBytes,
+ IResumable* aConsumer) {
+ MutexAutoLock lock(mMutex);
+
+ MOZ_ASSERT(aIterator.HasMore(),
+ "Advancing a completed iterator and "
+ "AdvanceOrScheduleResume didn't catch it");
+
+ if (MOZ_UNLIKELY(mStatus && NS_FAILED(*mStatus))) {
+ // This SourceBuffer is complete due to an error; all reads fail.
+ return aIterator.SetComplete(*mStatus);
+ }
+
+ if (MOZ_UNLIKELY(mChunks.Length() == 0)) {
+ // We haven't gotten an initial chunk yet.
+ AddWaitingConsumer(aConsumer);
+ return aIterator.SetWaiting(!!aConsumer);
+ }
+
+ uint32_t iteratorChunkIdx = aIterator.mData.mIterating.mChunk;
+ MOZ_ASSERT(iteratorChunkIdx < mChunks.Length());
+
+ const Chunk& currentChunk = mChunks[iteratorChunkIdx];
+ size_t iteratorEnd = aIterator.mData.mIterating.mOffset +
+ aIterator.mData.mIterating.mAvailableLength;
+ MOZ_ASSERT(iteratorEnd <= currentChunk.Length());
+ MOZ_ASSERT(iteratorEnd <= currentChunk.Capacity());
+
+ if (iteratorEnd < currentChunk.Length()) {
+ // There's more data in the current chunk.
+ return aIterator.SetReady(iteratorChunkIdx, currentChunk.Data(),
+ iteratorEnd, currentChunk.Length() - iteratorEnd,
+ aRequestedBytes);
+ }
+
+ if (iteratorEnd == currentChunk.Capacity() &&
+ !IsLastChunk(iteratorChunkIdx)) {
+ // Advance to the next chunk.
+ const Chunk& nextChunk = mChunks[iteratorChunkIdx + 1];
+ return aIterator.SetReady(iteratorChunkIdx + 1, nextChunk.Data(), 0,
+ nextChunk.Length(), aRequestedBytes);
+ }
+
+ MOZ_ASSERT(IsLastChunk(iteratorChunkIdx), "Should've advanced");
+
+ if (mStatus) {
+ // There's no more data and this SourceBuffer completed successfully.
+ MOZ_ASSERT(NS_SUCCEEDED(*mStatus), "Handled failures earlier");
+ return aIterator.SetComplete(*mStatus);
+ }
+
+ // We're not complete, but there's no more data right now. Arrange to wake up
+ // the consumer when we get more data.
+ AddWaitingConsumer(aConsumer);
+ return aIterator.SetWaiting(!!aConsumer);
+}
+
+nsresult SourceBuffer::HandleError(nsresult aError) {
+ MOZ_ASSERT(NS_FAILED(aError), "Should have an error here");
+ MOZ_ASSERT(aError == NS_ERROR_OUT_OF_MEMORY || aError == NS_ERROR_INVALID_ARG,
+ "Unexpected error; may want to notify waiting readers, which "
+ "HandleError currently doesn't do");
+
+ mMutex.AssertCurrentThreadOwns();
+
+ NS_WARNING("SourceBuffer encountered an unrecoverable error");
+
+ // Record the error.
+ mStatus = Some(aError);
+
+ // Drop our references to waiting readers.
+ mWaitingConsumers.Clear();
+
+ return *mStatus;
+}
+
+bool SourceBuffer::IsEmpty() {
+ mMutex.AssertCurrentThreadOwns();
+ return mChunks.Length() == 0 || mChunks[0].Length() == 0;
+}
+
+bool SourceBuffer::IsLastChunk(uint32_t aChunk) {
+ mMutex.AssertCurrentThreadOwns();
+ return aChunk + 1 == mChunks.Length();
+}
+
+} // namespace image
+} // namespace mozilla