1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/mozglue/linker/SeekableZStream.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,151 @@
1.4 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.5 + * License, v. 2.0. If a copy of the MPL was not distributed with this file,
1.6 + * You can obtain one at http://mozilla.org/MPL/2.0/. */
1.7 +
1.8 +#ifndef SeekableZStream_h
1.9 +#define SeekableZStream_h
1.10 +
1.11 +#include "Zip.h"
1.12 +
1.13 +/**
1.14 + * Seekable compressed stream are created by splitting the original
1.15 + * decompressed data in small chunks and compress these chunks
1.16 + * individually.
1.17 + *
1.18 + * The seekable compressed file format consists in a header defined below,
1.19 + * followed by a table of 32-bits words containing the offsets for each
1.20 + * individual compressed chunk, then followed by the compressed chunks.
1.21 + */
1.22 +
1.23 +#pragma pack(1)
1.24 +struct SeekableZStreamHeader: public Zip::SignedEntity<SeekableZStreamHeader>
1.25 +{
1.26 + SeekableZStreamHeader()
1.27 + : Zip::SignedEntity<SeekableZStreamHeader>(magic)
1.28 + , totalSize(0), chunkSize(0), dictSize(0), nChunks(0), lastChunkSize(0)
1.29 + , windowBits(0), filter(0) { }
1.30 +
1.31 + /* Reuse Zip::SignedEntity to handle the magic number used in the Seekable
1.32 + * ZStream file format. The magic number is "SeZz". */
1.33 + static const uint32_t magic = 0x7a5a6553;
1.34 +
1.35 + /* Total size of the stream, including the 4 magic bytes. */
1.36 + le_uint32 totalSize;
1.37 +
1.38 + /* Chunk size */
1.39 + le_uint16 chunkSize;
1.40 +
1.41 + /* Size of the dictionary */
1.42 + le_uint16 dictSize;
1.43 +
1.44 + /* Number of chunks */
1.45 + le_uint32 nChunks;
1.46 +
1.47 + /* Size of last chunk (> 0, <= Chunk size) */
1.48 + le_uint16 lastChunkSize;
1.49 +
1.50 + /* windowBits value used when deflating */
1.51 + signed char windowBits;
1.52 +
1.53 + /* Filter Id */
1.54 + unsigned char filter;
1.55 +};
1.56 +#pragma pack()
1.57 +
1.58 +static_assert(sizeof(SeekableZStreamHeader) == 5 * 4,
1.59 + "SeekableZStreamHeader should be 5 32-bits words");
1.60 +
1.61 +/**
1.62 + * Helper class used to decompress Seekable ZStreams.
1.63 + */
1.64 +class SeekableZStream {
1.65 +public:
1.66 + /* Initialize from the given buffer. Returns whether initialization
1.67 + * succeeded (true) or failed (false). */
1.68 + bool Init(const void *buf, size_t length);
1.69 +
1.70 + /* Decompresses starting from the given chunk. The decompressed data is
1.71 + * stored at the given location. The given length, in bytes, indicates
1.72 + * how much data to decompress. If length is 0, then exactly one chunk
1.73 + * is decompressed.
1.74 + * Returns whether decompression succeeded (true) or failed (false). */
1.75 + bool Decompress(void *where, size_t chunk, size_t length = 0);
1.76 +
1.77 + /* Decompresses the given chunk at the given address. If a length is given,
1.78 + * only decompresses that amount of data instead of the entire chunk.
1.79 + * Returns whether decompression succeeded (true) or failed (false). */
1.80 + bool DecompressChunk(void *where, size_t chunk, size_t length = 0);
1.81 +
1.82 + /* Returns the uncompressed size of the complete zstream */
1.83 + const size_t GetUncompressedSize() const
1.84 + {
1.85 + return (offsetTable.numElements() - 1) * chunkSize + lastChunkSize;
1.86 + }
1.87 +
1.88 + /* Returns the chunk size of the given chunk */
1.89 + const size_t GetChunkSize(size_t chunk = 0) const {
1.90 + return (chunk == offsetTable.numElements() - 1) ? lastChunkSize : chunkSize;
1.91 + }
1.92 +
1.93 + /* Returns the number of chunks */
1.94 + const size_t GetChunksNum() const {
1.95 + return offsetTable.numElements();
1.96 + }
1.97 +
1.98 + /**
1.99 + * Filters used to improve compression rate.
1.100 + */
1.101 + enum FilterDirection {
1.102 + FILTER,
1.103 + UNFILTER
1.104 + };
1.105 + typedef void (*ZStreamFilter)(off_t, FilterDirection,
1.106 + unsigned char *, size_t);
1.107 +
1.108 + enum FilterId {
1.109 + NONE,
1.110 + BCJ_THUMB,
1.111 + BCJ_ARM,
1.112 + BCJ_X86,
1.113 + FILTER_MAX
1.114 + };
1.115 + static ZStreamFilter GetFilter(FilterId id);
1.116 +
1.117 + static ZStreamFilter GetFilter(uint16_t id) {
1.118 + return GetFilter(static_cast<FilterId>(id));
1.119 + }
1.120 +
1.121 +private:
1.122 + /* RAW Seekable SZtream buffer */
1.123 + const unsigned char *buffer;
1.124 +
1.125 + /* Total size of the stream, including the 4 magic bytes. */
1.126 + uint32_t totalSize;
1.127 +
1.128 + /* Chunk size */
1.129 + uint32_t chunkSize;
1.130 +
1.131 + /* Size of last chunk (> 0, <= Chunk size) */
1.132 + uint32_t lastChunkSize;
1.133 +
1.134 + /* windowBits value used when deflating */
1.135 + int windowBits;
1.136 +
1.137 + /* Offsets table */
1.138 + Array<le_uint32> offsetTable;
1.139 +
1.140 + /* Filter */
1.141 + ZStreamFilter filter;
1.142 +
1.143 + /* Deflate dictionary */
1.144 + Array<unsigned char> dictionary;
1.145 +};
1.146 +
1.147 +inline void
1.148 +operator++(SeekableZStream::FilterId &other)
1.149 +{
1.150 + const int orig = static_cast<int>(other);
1.151 + other = static_cast<SeekableZStream::FilterId>(orig + 1);
1.152 +}
1.153 +
1.154 +#endif /* SeekableZStream_h */
