SnappyUncompressInputStream.h

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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/. */

#ifndef mozilla_SnappyUncompressInputStream_h__

#define mozilla_SnappyUncompressInputStream_h__

#include "mozilla/Attributes.h"

#include "mozilla/UniquePtr.h"

#include "nsCOMPtr.h"

#include "nsIInputStream.h"

#include "nsISupportsImpl.h"

#include "SnappyFrameUtils.h"

namespace mozilla {

class SnappyUncompressInputStream final : public nsIInputStream,

                                          protected detail::SnappyFrameUtils {

 public:

  // Construct a new blocking stream to uncompress the given base stream.  The

  // base stream must also be blocking.  The base stream does not have to be

  // buffered.

  explicit SnappyUncompressInputStream(nsIInputStream* aBaseStream);

 private:

  virtual ~SnappyUncompressInputStream();

  // Parse the next chunk of data.  This may populate mBuffer and set

  // mBufferFillSize.  This should not be called when mBuffer already

  // contains data.

  nsresult ParseNextChunk(uint32_t* aBytesReadOut);

  // Convenience routine to Read() from the base stream until we get

  // the given number of bytes or reach EOF.

//

  // aBuf           - The buffer to write the bytes into.

  // aCount         - Max number of bytes to read. If the stream closes

  //                  fewer bytes my be read.

  // aMinValidCount - A minimum expected number of bytes.  If we find

  //                  fewer than this many bytes, then return

  //                  NS_ERROR_CORRUPTED_CONTENT.  If nothing was read due

  //                  due to EOF (aBytesReadOut == 0), then NS_OK is returned.

  // aBytesReadOut  - An out parameter indicating how many bytes were read.

  nsresult ReadAll(char* aBuf, uint32_t aCount, uint32_t aMinValidCount,

                   uint32_t* aBytesReadOut);

  // Convenience routine to determine how many bytes of uncompressed data

  // we currently have in our buffer.

  size_t UncompressedLength() const;

  nsCOMPtr<nsIInputStream> mBaseStream;

  // Buffer to hold compressed data.  Must copy here since we need a large

  // flat buffer to run the uncompress process on. Always the same length

  // of SnappyFrameUtils::MaxCompressedBufferLength(snappy::kBlockSize)

  // bytes long.

  mozilla::UniquePtr<char[]> mCompressedBuffer;

  // Buffer storing the resulting uncompressed data.  Exactly snappy::kBlockSize

  // bytes long.

  mozilla::UniquePtr<char[]> mUncompressedBuffer;

  // Number of bytes of uncompressed data in mBuffer.

  size_t mUncompressedBytes;

  // Next byte of mBuffer to return in ReadSegments().  Must be less than

  // mBufferFillSize

  size_t mNextByte;

  // Next chunk in the stream that has been parsed during read-ahead.

  ChunkType mNextChunkType;

  // Length of next chunk's length that has been determined during read-ahead.

  size_t mNextChunkDataLength;

  // The stream must begin with a StreamIdentifier chunk.  Are we still

  // expecting it?

  bool mNeedFirstStreamIdentifier;

 public:

  NS_DECL_THREADSAFE_ISUPPORTS

  NS_DECL_NSIINPUTSTREAM

};

}  // namespace mozilla

#endif  // mozilla_SnappyUncompressInputStream_h__