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-rw-r--r--xpcom/io/SnappyCompressOutputStream.cpp256
1 files changed, 256 insertions, 0 deletions
diff --git a/xpcom/io/SnappyCompressOutputStream.cpp b/xpcom/io/SnappyCompressOutputStream.cpp
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+++ b/xpcom/io/SnappyCompressOutputStream.cpp
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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 "mozilla/SnappyCompressOutputStream.h"
+
+#include <algorithm>
+#include "nsStreamUtils.h"
+#include "snappy/snappy.h"
+
+namespace mozilla {
+
+NS_IMPL_ISUPPORTS(SnappyCompressOutputStream, nsIOutputStream);
+
+// static
+const size_t
+SnappyCompressOutputStream::kMaxBlockSize = snappy::kBlockSize;
+
+SnappyCompressOutputStream::SnappyCompressOutputStream(nsIOutputStream* aBaseStream,
+ size_t aBlockSize)
+ : mBaseStream(aBaseStream)
+ , mBlockSize(std::min(aBlockSize, kMaxBlockSize))
+ , mNextByte(0)
+ , mCompressedBufferLength(0)
+ , mStreamIdentifierWritten(false)
+{
+ MOZ_ASSERT(mBlockSize > 0);
+
+ // This implementation only supports sync base streams. Verify this in debug
+ // builds. Note, this can be simpler than the check in
+ // SnappyUncompressInputStream because we don't have to deal with the
+ // nsStringInputStream oddness of being non-blocking and sync.
+#ifdef DEBUG
+ bool baseNonBlocking;
+ nsresult rv = mBaseStream->IsNonBlocking(&baseNonBlocking);
+ MOZ_ASSERT(NS_SUCCEEDED(rv));
+ MOZ_ASSERT(!baseNonBlocking);
+#endif
+}
+
+size_t
+SnappyCompressOutputStream::BlockSize() const
+{
+ return mBlockSize;
+}
+
+NS_IMETHODIMP
+SnappyCompressOutputStream::Close()
+{
+ if (!mBaseStream) {
+ return NS_OK;
+ }
+
+ nsresult rv = Flush();
+ if (NS_WARN_IF(NS_FAILED(rv))) { return rv; }
+
+ mBaseStream->Close();
+ mBaseStream = nullptr;
+
+ mBuffer = nullptr;
+ mCompressedBuffer = nullptr;
+
+ return NS_OK;
+}
+
+NS_IMETHODIMP
+SnappyCompressOutputStream::Flush()
+{
+ if (!mBaseStream) {
+ return NS_BASE_STREAM_CLOSED;
+ }
+
+ nsresult rv = FlushToBaseStream();
+ if (NS_WARN_IF(NS_FAILED(rv))) { return rv; }
+
+ mBaseStream->Flush();
+
+ return NS_OK;
+}
+
+NS_IMETHODIMP
+SnappyCompressOutputStream::Write(const char* aBuf, uint32_t aCount,
+ uint32_t* aResultOut)
+{
+ return WriteSegments(NS_CopySegmentToBuffer, const_cast<char*>(aBuf), aCount,
+ aResultOut);
+}
+
+NS_IMETHODIMP
+SnappyCompressOutputStream::WriteFrom(nsIInputStream*, uint32_t, uint32_t*)
+{
+ return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+SnappyCompressOutputStream::WriteSegments(nsReadSegmentFun aReader,
+ void* aClosure,
+ uint32_t aCount,
+ uint32_t* aBytesWrittenOut)
+{
+ *aBytesWrittenOut = 0;
+
+ if (!mBaseStream) {
+ return NS_BASE_STREAM_CLOSED;
+ }
+
+ if (!mBuffer) {
+ mBuffer.reset(new (fallible) char[mBlockSize]);
+ if (NS_WARN_IF(!mBuffer)) {
+ return NS_ERROR_OUT_OF_MEMORY;
+ }
+ }
+
+ while (aCount > 0) {
+ // Determine how much space is left in our flat, uncompressed buffer.
+ MOZ_ASSERT(mNextByte <= mBlockSize);
+ uint32_t remaining = mBlockSize - mNextByte;
+
+ // If it is full, then compress and flush the data to the base stream.
+ if (remaining == 0) {
+ nsresult rv = FlushToBaseStream();
+ if (NS_WARN_IF(NS_FAILED(rv))) { return rv; }
+
+ // Now the entire buffer should be available for copying.
+ MOZ_ASSERT(!mNextByte);
+ remaining = mBlockSize;
+ }
+
+ uint32_t numToRead = std::min(remaining, aCount);
+ uint32_t numRead = 0;
+
+ nsresult rv = aReader(this, aClosure, &mBuffer[mNextByte],
+ *aBytesWrittenOut, numToRead, &numRead);
+
+ // As defined in nsIOutputStream.idl, do not pass reader func errors.
+ if (NS_FAILED(rv)) {
+ return NS_OK;
+ }
+
+ // End-of-file
+ if (numRead == 0) {
+ return NS_OK;
+ }
+
+ mNextByte += numRead;
+ *aBytesWrittenOut += numRead;
+ aCount -= numRead;
+ }
+
+ return NS_OK;
+}
+
+NS_IMETHODIMP
+SnappyCompressOutputStream::IsNonBlocking(bool* aNonBlockingOut)
+{
+ *aNonBlockingOut = false;
+ return NS_OK;
+}
+
+SnappyCompressOutputStream::~SnappyCompressOutputStream()
+{
+ Close();
+}
+
+nsresult
+SnappyCompressOutputStream::FlushToBaseStream()
+{
+ MOZ_ASSERT(mBaseStream);
+
+ // Lazily create the compressed buffer on our first flush. This
+ // allows us to report OOM during stream operation. This buffer
+ // will then get re-used until the stream is closed.
+ if (!mCompressedBuffer) {
+ mCompressedBufferLength = MaxCompressedBufferLength(mBlockSize);
+ mCompressedBuffer.reset(new (fallible) char[mCompressedBufferLength]);
+ if (NS_WARN_IF(!mCompressedBuffer)) {
+ return NS_ERROR_OUT_OF_MEMORY;
+ }
+ }
+
+ // The first chunk must be a StreamIdentifier chunk. Write it out
+ // if we have not done so already.
+ nsresult rv = MaybeFlushStreamIdentifier();
+ if (NS_WARN_IF(NS_FAILED(rv))) { return rv; }
+
+ // Compress the data to our internal compressed buffer.
+ size_t compressedLength;
+ rv = WriteCompressedData(mCompressedBuffer.get(), mCompressedBufferLength,
+ mBuffer.get(), mNextByte, &compressedLength);
+ if (NS_WARN_IF(NS_FAILED(rv))) { return rv; }
+ MOZ_ASSERT(compressedLength > 0);
+
+ mNextByte = 0;
+
+ // Write the compressed buffer out to the base stream.
+ uint32_t numWritten = 0;
+ rv = WriteAll(mCompressedBuffer.get(), compressedLength, &numWritten);
+ if (NS_WARN_IF(NS_FAILED(rv))) { return rv; }
+ MOZ_ASSERT(compressedLength == numWritten);
+
+ return NS_OK;
+}
+
+nsresult
+SnappyCompressOutputStream::MaybeFlushStreamIdentifier()
+{
+ MOZ_ASSERT(mCompressedBuffer);
+
+ if (mStreamIdentifierWritten) {
+ return NS_OK;
+ }
+
+ // Build the StreamIdentifier in our compressed buffer.
+ size_t compressedLength;
+ nsresult rv = WriteStreamIdentifier(mCompressedBuffer.get(),
+ mCompressedBufferLength,
+ &compressedLength);
+ if (NS_WARN_IF(NS_FAILED(rv))) { return rv; }
+
+ // Write the compressed buffer out to the base stream.
+ uint32_t numWritten = 0;
+ rv = WriteAll(mCompressedBuffer.get(), compressedLength, &numWritten);
+ if (NS_WARN_IF(NS_FAILED(rv))) { return rv; }
+ MOZ_ASSERT(compressedLength == numWritten);
+
+ mStreamIdentifierWritten = true;
+
+ return NS_OK;
+}
+
+nsresult
+SnappyCompressOutputStream::WriteAll(const char* aBuf, uint32_t aCount,
+ uint32_t* aBytesWrittenOut)
+{
+ *aBytesWrittenOut = 0;
+
+ if (!mBaseStream) {
+ return NS_BASE_STREAM_CLOSED;
+ }
+
+ uint32_t offset = 0;
+ while (aCount > 0) {
+ uint32_t numWritten = 0;
+ nsresult rv = mBaseStream->Write(aBuf + offset, aCount, &numWritten);
+ if (NS_WARN_IF(NS_FAILED(rv))) { return rv; }
+ offset += numWritten;
+ aCount -= numWritten;
+ *aBytesWrittenOut += numWritten;
+ }
+
+ return NS_OK;
+}
+
+} // namespace mozilla