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