xpcom/io/SnappyUncompressInputStream.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_SnappyUncompressInputStream_h__
   8 #define mozilla_SnappyUncompressInputStream_h__
   9
  10 #include "mozilla/Attributes.h"
  11 #include "mozilla/UniquePtr.h"
  12 #include "nsCOMPtr.h"
  13 #include "nsIInputStream.h"
  14 #include "nsISupportsImpl.h"
  15 #include "SnappyFrameUtils.h"
  16
  17 namespace mozilla {
  18
  19 class SnappyUncompressInputStream final : public nsIInputStream
  20                                         , protected detail::SnappyFrameUtils
  21 {
  22 public:
  23   // Construct a new blocking stream to uncompress the given base stream.  The
  24   // base stream must also be blocking.  The base stream does not have to be
  25   // buffered.
  26   explicit SnappyUncompressInputStream(nsIInputStream* aBaseStream);
  27
  28 private:
  29   virtual ~SnappyUncompressInputStream();
  30
  31   // Parse the next chunk of data.  This may populate mBuffer and set
  32   // mBufferFillSize.  This should not be called when mBuffer already
  33   // contains data.
  34   nsresult ParseNextChunk(uint32_t* aBytesReadOut);
  35
  36   // Convenience routine to Read() from the base stream until we get
  37   // the given number of bytes or reach EOF.
  38   //
  39   // aBuf           - The buffer to write the bytes into.
  40   // aCount         - Max number of bytes to read. If the stream closes
  41   //                  fewer bytes my be read.
  42   // aMinValidCount - A minimum expected number of bytes.  If we find
  43   //                  fewer than this many bytes, then return
  44   //                  NS_ERROR_CORRUPTED_CONTENT.  If nothing was read due
  45   //                  due to EOF (aBytesReadOut == 0), then NS_OK is returned.
  46   // aBytesReadOut  - An out parameter indicating how many bytes were read.
  47   nsresult ReadAll(char* aBuf, uint32_t aCount, uint32_t aMinValidCount,
  48                    uint32_t* aBytesReadOut);
  49
  50   // Convenience routine to determine how many bytes of uncompressed data
  51   // we currently have in our buffer.
  52   size_t UncompressedLength() const;
  53
  54   nsCOMPtr<nsIInputStream> mBaseStream;
  55
  56   // Buffer to hold compressed data.  Must copy here since we need a large
  57   // flat buffer to run the uncompress process on. Always the same length
  58   // of SnappyFrameUtils::MaxCompressedBufferLength(snappy::kBlockSize)
  59   // bytes long.
  60   mozilla::UniquePtr<char[]> mCompressedBuffer;
  61
  62   // Buffer storing the resulting uncompressed data.  Exactly snappy::kBlockSize
  63   // bytes long.
  64   mozilla::UniquePtr<char[]> mUncompressedBuffer;
  65
  66   // Number of bytes of uncompressed data in mBuffer.
  67   size_t mUncompressedBytes;
  68
  69   // Next byte of mBuffer to return in ReadSegments().  Must be less than
  70   // mBufferFillSize
  71   size_t mNextByte;
  72
  73   // Next chunk in the stream that has been parsed during read-ahead.
  74   ChunkType mNextChunkType;
  75
  76   // Length of next chunk's length that has been determined during read-ahead.
  77   size_t mNextChunkDataLength;
  78
  79   // The stream must begin with a StreamIdentifier chunk.  Are we still
  80   // expecting it?
  81   bool mNeedFirstStreamIdentifier;
  82
  83 public:
  84   NS_DECL_THREADSAFE_ISUPPORTS
  85   NS_DECL_NSIINPUTSTREAM
  86 };
  87
  88 } // namespace mozilla
  89
  90 #endif // mozilla_SnappyUncompressInputStream_h__