mfbt/Compression.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 /* Various simple compression/decompression functions. */
   8
   9 #ifndef mozilla_Compression_h_
  10 #define mozilla_Compression_h_
  11
  12 #include "mozilla/Assertions.h"
  13 #include "mozilla/Types.h"
  14 #include "mozilla/Result.h"
  15 #include "mozilla/Span.h"
  16 #include "mozilla/UniquePtr.h"
  17
  18 struct LZ4F_cctx_s;  // compression context
  19 struct LZ4F_dctx_s;  // decompression context
  20
  21 namespace mozilla {
  22 namespace Compression {
  23
  24 /**
  25  * LZ4 is a very fast byte-wise compression algorithm.
  26  *
  27  * Compared to Google's Snappy it is faster to compress and decompress and
  28  * generally produces output of about the same size.
  29  *
  30  * Compared to zlib it compresses at about 10x the speed, decompresses at about
  31  * 4x the speed and produces output of about 1.5x the size.
  32  */
  33
  34 class LZ4 {
  35  public:
  36   /**
  37    * Compresses |aInputSize| bytes from |aSource| into |aDest|. Destination
  38    * buffer must be already allocated, and must be sized to handle worst cases
  39    * situations (input data not compressible). Worst case size evaluation is
  40    * provided by function maxCompressedSize()
  41    *
  42    * @param aInputSize is the input size. Max supported value is ~1.9GB
  43    * @return the number of bytes written in buffer |aDest|
  44    */
  45   static MFBT_API size_t compress(const char* aSource, size_t aInputSize,
  46                                   char* aDest);
  47
  48   /**
  49    * Compress |aInputSize| bytes from |aSource| into an output buffer
  50    * |aDest| of maximum size |aMaxOutputSize|.  If it cannot achieve it,
  51    * compression will stop, and result of the function will be zero,
  52    * |aDest| will still be written to, but since the number of input
  53    * bytes consumed is not returned the result is not usable.
  54    *
  55    * This function never writes outside of provided output buffer.
  56    *
  57    * @param aInputSize is the input size. Max supported value is ~1.9GB
  58    * @param aMaxOutputSize is the size of the destination buffer (which must
  59    *   be already allocated)
  60    * @return the number of bytes written in buffer |aDest| or 0 if the
  61    *   compression fails
  62    */
  63   static MFBT_API size_t compressLimitedOutput(const char* aSource,
  64                                                size_t aInputSize, char* aDest,
  65                                                size_t aMaxOutputSize);
  66
  67   /**
  68    * If the source stream is malformed, the function will stop decoding
  69    * and return false.
  70    *
  71    * This function never writes outside of provided buffers, and never
  72    * modifies input buffer.
  73    *
  74    * Note: destination buffer must be already allocated, and its size must be a
  75    *       minimum of |aOutputSize| bytes.
  76    *
  77    * @param aOutputSize is the output size, therefore the original size
  78    * @return true on success, false on failure
  79    */
  80   static MFBT_API MOZ_MUST_USE bool decompress(const char* aSource, char* aDest,
  81                                                size_t aOutputSize);
  82
  83   /**
  84    * If the source stream is malformed, the function will stop decoding
  85    * and return false.
  86    *
  87    * This function never writes beyond aDest + aMaxOutputSize, and is
  88    * therefore protected against malicious data packets.
  89    *
  90    * Note: Destination buffer must be already allocated.  This version is
  91    *       slightly slower than the decompress without the aMaxOutputSize.
  92    *
  93    * @param aInputSize is the length of the input compressed data
  94    * @param aMaxOutputSize is the size of the destination buffer (which must be
  95    *   already allocated)
  96    * @param aOutputSize the actual number of bytes decoded in the destination
  97    *   buffer (necessarily <= aMaxOutputSize)
  98    * @return true on success, false on failure
  99    */
 100   static MFBT_API MOZ_MUST_USE bool decompress(const char* aSource,
 101                                                size_t aInputSize, char* aDest,
 102                                                size_t aMaxOutputSize,
 103                                                size_t* aOutputSize);
 104
 105   /**
 106    * If the source stream is malformed, the function will stop decoding
 107    * and return false.
 108    *
 109    * This function never writes beyond aDest + aMaxOutputSize, and is
 110    * therefore protected against malicious data packets. It also ignores
 111    * unconsumed input upon reaching aMaxOutputSize and can therefore be used
 112    * for partial decompression.
 113    *
 114    * Note: Destination buffer must be already allocated.  This version is
 115    *       slightly slower than the decompress without the aMaxOutputSize.
 116    *
 117    * @param aInputSize is the length of the input compressed data
 118    * @param aMaxOutputSize is the size of the destination buffer (which must be
 119    *   already allocated)
 120    * @param aOutputSize the actual number of bytes decoded in the destination
 121    *   buffer (necessarily <= aMaxOutputSize)
 122    * @return true on success, false on failure
 123    */
 124   static MFBT_API MOZ_MUST_USE bool decompressPartial(const char* aSource,
 125                                                       size_t aInputSize,
 126                                                       char* aDest,
 127                                                       size_t aMaxOutputSize,
 128                                                       size_t* aOutputSize);
 129
 130   /*
 131    * Provides the maximum size that LZ4 may output in a "worst case"
 132    * scenario (input data not compressible) primarily useful for memory
 133    * allocation of output buffer.
 134    * note : this function is limited by "int" range (2^31-1)
 135    *
 136    * @param aInputSize is the input size. Max supported value is ~1.9GB
 137    * @return maximum output size in a "worst case" scenario
 138    */
 139   static inline size_t maxCompressedSize(size_t aInputSize) {
 140     size_t max = (aInputSize + (aInputSize / 255) + 16);
 141     MOZ_ASSERT(max > aInputSize);
 142     return max;
 143   }
 144 };
 145
 146 /**
 147  * Context for LZ4 Frame-based streaming compression. Use this if you
 148  * want to incrementally compress something or if you want to compress
 149  * something such that another application can read it.
 150  */
 151 class LZ4FrameCompressionContext final {
 152  public:
 153   MFBT_API LZ4FrameCompressionContext(int aCompressionLevel, size_t aMaxSrcSize,
 154                                       bool aChecksum, bool aStableSrc = false);
 155
 156   MFBT_API ~LZ4FrameCompressionContext();
 157
 158   size_t GetRequiredWriteBufferLength() { return mWriteBufLen; }
 159
 160   /**
 161    * Begin streaming frame-based compression.
 162    *
 163    * @return a Result with a Span containing the frame header, or an lz4 error
 164    * code (size_t).
 165    */
 166   MFBT_API Result<Span<const char>, size_t> BeginCompressing(
 167       Span<char> aWriteBuffer);
 168
 169   /**
 170    * Continue streaming frame-based compression with the provided input.
 171    *
 172    * @param aInput input buffer to be compressed.
 173    * @return a Result with a Span containing compressed output, or an lz4 error
 174    * code (size_t).
 175    */
 176   MFBT_API Result<Span<const char>, size_t> ContinueCompressing(
 177       Span<const char> aInput);
 178
 179   /**
 180    * Finalize streaming frame-based compression with the provided input.
 181    *
 182    * @return a Result with a Span containing compressed output and the frame
 183    * footer, or an lz4 error code (size_t).
 184    */
 185   MFBT_API Result<Span<const char>, size_t> EndCompressing();
 186
 187  private:
 188   LZ4F_cctx_s* mContext;
 189   int mCompressionLevel;
 190   bool mGenerateChecksum;
 191   bool mStableSrc;
 192   size_t mMaxSrcSize;
 193   size_t mWriteBufLen;
 194   Span<char> mWriteBuffer;
 195 };
 196
 197 struct LZ4FrameDecompressionResult {
 198   size_t mSizeRead;
 199   size_t mSizeWritten;
 200   bool mFinished;
 201 };
 202
 203 /**
 204  * Context for LZ4 Frame-based streaming decompression. Use this if you
 205  * want to decompress something compressed by LZ4FrameCompressionContext
 206  * or by another application.
 207  */
 208 class LZ4FrameDecompressionContext final {
 209  public:
 210   explicit MFBT_API LZ4FrameDecompressionContext(bool aStableDest = false);
 211   MFBT_API ~LZ4FrameDecompressionContext();
 212
 213   /**
 214    * Decompress a buffer/part of a buffer compressed with
 215    * LZ4FrameCompressionContext or another application.
 216    *
 217    * @param aOutput output buffer to be write results into.
 218    * @param aInput input buffer to be decompressed.
 219    * @return a Result with information on bytes read/written and whether we
 220    * completely decompressed the input into the output, or an lz4 error code
 221    * (size_t).
 222    */
 223   MFBT_API Result<LZ4FrameDecompressionResult, size_t> Decompress(
 224       Span<char> aOutput, Span<const char> aInput);
 225
 226  private:
 227   LZ4F_dctx_s* mContext;
 228   bool mStableDest;
 229 };
 230
 231 } /* namespace Compression */
 232 } /* namespace mozilla */
 233
 234 #endif /* mozilla_Compression_h_ */