michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
michael@0:  * You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef SeekableZStream_h
michael@0: #define SeekableZStream_h
michael@0: 
michael@0: #include "Zip.h"
michael@0: 
michael@0: /**
michael@0:  * Seekable compressed stream are created by splitting the original
michael@0:  * decompressed data in small chunks and compress these chunks
michael@0:  * individually.
michael@0:  *
michael@0:  * The seekable compressed file format consists in a header defined below,
michael@0:  * followed by a table of 32-bits words containing the offsets for each
michael@0:  * individual compressed chunk, then followed by the compressed chunks.
michael@0:  */
michael@0: 
michael@0: #pragma pack(1)
michael@0: struct SeekableZStreamHeader: public Zip::SignedEntity<SeekableZStreamHeader>
michael@0: {
michael@0:   SeekableZStreamHeader()
michael@0:   : Zip::SignedEntity<SeekableZStreamHeader>(magic)
michael@0:   , totalSize(0), chunkSize(0), dictSize(0), nChunks(0), lastChunkSize(0)
michael@0:   , windowBits(0), filter(0) { }
michael@0: 
michael@0:   /* Reuse Zip::SignedEntity to handle the magic number used in the Seekable
michael@0:    * ZStream file format. The magic number is "SeZz". */
michael@0:   static const uint32_t magic = 0x7a5a6553;
michael@0: 
michael@0:   /* Total size of the stream, including the 4 magic bytes. */
michael@0:   le_uint32 totalSize;
michael@0: 
michael@0:   /* Chunk size */
michael@0:   le_uint16 chunkSize;
michael@0: 
michael@0:   /* Size of the dictionary */
michael@0:   le_uint16 dictSize;
michael@0: 
michael@0:   /* Number of chunks */
michael@0:   le_uint32 nChunks;
michael@0: 
michael@0:   /* Size of last chunk (> 0, <= Chunk size) */
michael@0:   le_uint16 lastChunkSize;
michael@0: 
michael@0:   /* windowBits value used when deflating */
michael@0:   signed char windowBits;
michael@0: 
michael@0:   /* Filter Id */
michael@0:   unsigned char filter;
michael@0: };
michael@0: #pragma pack()
michael@0: 
michael@0: static_assert(sizeof(SeekableZStreamHeader) == 5 * 4,
michael@0:               "SeekableZStreamHeader should be 5 32-bits words");
michael@0: 
michael@0: /**
michael@0:  * Helper class used to decompress Seekable ZStreams.
michael@0:  */
michael@0: class SeekableZStream {
michael@0: public:
michael@0:   /* Initialize from the given buffer. Returns whether initialization
michael@0:    * succeeded (true) or failed (false). */
michael@0:   bool Init(const void *buf, size_t length);
michael@0: 
michael@0:   /* Decompresses starting from the given chunk. The decompressed data is
michael@0:    * stored at the given location. The given length, in bytes, indicates
michael@0:    * how much data to decompress. If length is 0, then exactly one chunk
michael@0:    * is decompressed.
michael@0:    * Returns whether decompression succeeded (true) or failed (false). */
michael@0:   bool Decompress(void *where, size_t chunk, size_t length = 0);
michael@0: 
michael@0:   /* Decompresses the given chunk at the given address. If a length is given,
michael@0:    * only decompresses that amount of data instead of the entire chunk.
michael@0:    * Returns whether decompression succeeded (true) or failed (false). */
michael@0:   bool DecompressChunk(void *where, size_t chunk, size_t length = 0);
michael@0:  
michael@0:   /* Returns the uncompressed size of the complete zstream */
michael@0:   const size_t GetUncompressedSize() const
michael@0:   {
michael@0:     return (offsetTable.numElements() - 1) * chunkSize + lastChunkSize;
michael@0:   }
michael@0: 
michael@0:   /* Returns the chunk size of the given chunk */
michael@0:   const size_t GetChunkSize(size_t chunk = 0) const {
michael@0:     return (chunk == offsetTable.numElements() - 1) ? lastChunkSize : chunkSize;
michael@0:   }
michael@0: 
michael@0:   /* Returns the number of chunks */
michael@0:   const size_t GetChunksNum() const {
michael@0:     return offsetTable.numElements();
michael@0:   }
michael@0: 
michael@0:   /**
michael@0:    * Filters used to improve compression rate.
michael@0:    */
michael@0:   enum FilterDirection {
michael@0:     FILTER,
michael@0:     UNFILTER
michael@0:   };
michael@0:   typedef void (*ZStreamFilter)(off_t, FilterDirection,
michael@0:                                   unsigned char *, size_t);
michael@0: 
michael@0:   enum FilterId {
michael@0:     NONE,
michael@0:     BCJ_THUMB,
michael@0:     BCJ_ARM,
michael@0:     BCJ_X86,
michael@0:     FILTER_MAX
michael@0:   };
michael@0:   static ZStreamFilter GetFilter(FilterId id);
michael@0: 
michael@0:   static ZStreamFilter GetFilter(uint16_t id) {
michael@0:     return GetFilter(static_cast<FilterId>(id));
michael@0:   }
michael@0: 
michael@0: private:
michael@0:   /* RAW Seekable SZtream buffer */
michael@0:   const unsigned char *buffer;
michael@0: 
michael@0:   /* Total size of the stream, including the 4 magic bytes. */
michael@0:   uint32_t totalSize;
michael@0: 
michael@0:   /* Chunk size */
michael@0:   uint32_t chunkSize;
michael@0: 
michael@0:   /* Size of last chunk (> 0, <= Chunk size) */
michael@0:   uint32_t lastChunkSize;
michael@0: 
michael@0:   /* windowBits value used when deflating */
michael@0:   int windowBits;
michael@0: 
michael@0:   /* Offsets table */
michael@0:   Array<le_uint32> offsetTable;
michael@0: 
michael@0:   /* Filter */
michael@0:   ZStreamFilter filter;
michael@0: 
michael@0:   /* Deflate dictionary */
michael@0:   Array<unsigned char> dictionary;
michael@0: };
michael@0: 
michael@0: inline void
michael@0: operator++(SeekableZStream::FilterId &other)
michael@0: {
michael@0:   const int orig = static_cast<int>(other);
michael@0:   other = static_cast<SeekableZStream::FilterId>(orig + 1);
michael@0: }
michael@0: 
michael@0: #endif /* SeekableZStream_h */