xpcom/io/SnappyFrameUtils.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_SnappyFrameUtils_h__
   8 #define mozilla_SnappyFrameUtils_h__
   9
  10 #include <cstddef>
  11
  12 #include "mozilla/Attributes.h"
  13 #include "nsError.h"
  14
  15 namespace mozilla {
  16 namespace detail {
  17
  18 //
  19 // Utility class providing primitives necessary to build streams based
  20 // on the snappy compressor.  This essentially abstracts the framing format
  21 // defined in:
  22 //
  23 //  other-licences/snappy/src/framing_format.txt
  24 //
  25 // NOTE: Currently only the StreamIdentifier and CompressedData chunks are
  26 //       supported.
  27 //
  28 class SnappyFrameUtils {
  29  public:
  30   enum ChunkType {
  31     Unknown,
  32     StreamIdentifier,
  33     CompressedData,
  34     UncompressedData,
  35     Padding,
  36     Reserved,
  37     ChunkTypeCount
  38   };
  39
  40   static const size_t kChunkTypeLength = 1;
  41   static const size_t kChunkLengthLength = 3;
  42   static const size_t kHeaderLength = kChunkTypeLength + kChunkLengthLength;
  43   static const size_t kStreamIdentifierDataLength = 6;
  44   static const size_t kCRCLength = 4;
  45
  46   static nsresult WriteStreamIdentifier(char* aDest, size_t aDestLength,
  47                                         size_t* aBytesWrittenOut);
  48
  49   static nsresult WriteCompressedData(char* aDest, size_t aDestLength,
  50                                       const char* aData, size_t aDataLength,
  51                                       size_t* aBytesWrittenOut);
  52
  53   static nsresult ParseHeader(const char* aSource, size_t aSourceLength,
  54                               ChunkType* aTypeOut, size_t* aDataLengthOut);
  55
  56   static nsresult ParseData(char* aDest, size_t aDestLength, ChunkType aType,
  57                             const char* aData, size_t aDataLength,
  58                             size_t* aBytesWrittenOut, size_t* aBytesReadOut);
  59
  60   static nsresult ParseStreamIdentifier(char* aDest, size_t aDestLength,
  61                                         const char* aData, size_t aDataLength,
  62                                         size_t* aBytesWrittenOut,
  63                                         size_t* aBytesReadOut);
  64
  65   static nsresult ParseCompressedData(char* aDest, size_t aDestLength,
  66                                       const char* aData, size_t aDataLength,
  67                                       size_t* aBytesWrittenOut,
  68                                       size_t* aBytesReadOut);
  69
  70   static size_t MaxCompressedBufferLength(size_t aSourceLength);
  71
  72  protected:
  73   SnappyFrameUtils() = default;
  74   virtual ~SnappyFrameUtils() = default;
  75 };
  76
  77 }  // namespace detail
  78 }  // namespace mozilla
  79
  80 #endif  // mozilla_SnappyFrameUtils_h__