195 lines
8.7 KiB
C
195 lines
8.7 KiB
C
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/* This file is part of libmspack.
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* (C) 2003-2004 Stuart Caie.
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*
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* The LZX method was created by Jonathan Forbes and Tomi Poutanen, adapted
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* by Microsoft Corporation.
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*
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* libmspack is free software; you can redistribute it and/or modify it under
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* the terms of the GNU Lesser General Public License (LGPL) version 2.1
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*
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* For further details, see the file COPYING.LIB distributed with libmspack
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*/
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#ifndef MSPACK_LZX_H
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#define MSPACK_LZX_H 1
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* LZX compression / decompression definitions */
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/* some constants defined by the LZX specification */
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#define LZX_MIN_MATCH (2)
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#define LZX_MAX_MATCH (257)
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#define LZX_NUM_CHARS (256)
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#define LZX_BLOCKTYPE_INVALID (0) /* also blocktypes 4-7 invalid */
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#define LZX_BLOCKTYPE_VERBATIM (1)
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#define LZX_BLOCKTYPE_ALIGNED (2)
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#define LZX_BLOCKTYPE_UNCOMPRESSED (3)
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#define LZX_PRETREE_NUM_ELEMENTS (20)
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#define LZX_ALIGNED_NUM_ELEMENTS (8) /* aligned offset tree #elements */
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#define LZX_NUM_PRIMARY_LENGTHS (7) /* this one missing from spec! */
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#define LZX_NUM_SECONDARY_LENGTHS (249) /* length tree #elements */
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/* LZX huffman defines: tweak tablebits as desired */
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#define LZX_PRETREE_MAXSYMBOLS (LZX_PRETREE_NUM_ELEMENTS)
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#define LZX_PRETREE_TABLEBITS (6)
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#define LZX_MAINTREE_MAXSYMBOLS (LZX_NUM_CHARS + 50*8)
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#define LZX_MAINTREE_TABLEBITS (12)
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#define LZX_LENGTH_MAXSYMBOLS (LZX_NUM_SECONDARY_LENGTHS+1)
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#define LZX_LENGTH_TABLEBITS (12)
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#define LZX_ALIGNED_MAXSYMBOLS (LZX_ALIGNED_NUM_ELEMENTS)
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#define LZX_ALIGNED_TABLEBITS (7)
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#define LZX_LENTABLE_SAFETY (64) /* table decoding overruns are allowed */
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#define LZX_FRAME_SIZE (32768) /* the size of a frame in LZX */
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struct lzxd_stream {
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struct mspack_system *sys; /* I/O routines */
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struct mspack_file *input; /* input file handle */
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struct mspack_file *output; /* output file handle */
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off_t offset; /* number of bytes actually output */
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off_t length; /* overall decompressed length of stream */
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unsigned char *window; /* decoding window */
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unsigned int window_size; /* window size */
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unsigned int window_posn; /* decompression offset within window */
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unsigned int frame_posn; /* current frame offset within in window */
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unsigned int frame; /* the number of 32kb frames processed */
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unsigned int reset_interval; /* which frame do we reset the compressor? */
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unsigned int R0, R1, R2; /* for the LRU offset system */
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unsigned int block_length; /* uncompressed length of this LZX block */
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unsigned int block_remaining; /* uncompressed bytes still left to decode */
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signed int intel_filesize; /* magic header value used for transform */
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signed int intel_curpos; /* current offset in transform space */
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unsigned char intel_started; /* has intel E8 decoding started? */
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unsigned char block_type; /* type of the current block */
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unsigned char header_read; /* have we started decoding at all yet? */
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unsigned char posn_slots; /* how many posn slots in stream? */
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unsigned char input_end; /* have we reached the end of input? */
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int error;
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/* I/O buffering */
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unsigned char *inbuf, *i_ptr, *i_end, *o_ptr, *o_end;
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unsigned int bit_buffer, bits_left, inbuf_size;
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/* huffman code lengths */
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unsigned char PRETREE_len [LZX_PRETREE_MAXSYMBOLS + LZX_LENTABLE_SAFETY];
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unsigned char MAINTREE_len [LZX_MAINTREE_MAXSYMBOLS + LZX_LENTABLE_SAFETY];
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unsigned char LENGTH_len [LZX_LENGTH_MAXSYMBOLS + LZX_LENTABLE_SAFETY];
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unsigned char ALIGNED_len [LZX_ALIGNED_MAXSYMBOLS + LZX_LENTABLE_SAFETY];
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/* huffman decoding tables */
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unsigned short PRETREE_table [(1 << LZX_PRETREE_TABLEBITS) +
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(LZX_PRETREE_MAXSYMBOLS * 2)];
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unsigned short MAINTREE_table[(1 << LZX_MAINTREE_TABLEBITS) +
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(LZX_MAINTREE_MAXSYMBOLS * 2)];
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unsigned short LENGTH_table [(1 << LZX_LENGTH_TABLEBITS) +
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(LZX_LENGTH_MAXSYMBOLS * 2)];
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unsigned short ALIGNED_table [(1 << LZX_ALIGNED_TABLEBITS) +
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(LZX_ALIGNED_MAXSYMBOLS * 2)];
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unsigned char LENGTH_empty;
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/* this is used purely for doing the intel E8 transform */
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unsigned char e8_buf[LZX_FRAME_SIZE];
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};
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/**
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* Allocates and initialises LZX decompression state for decoding an LZX
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* stream.
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*
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* This routine uses system->alloc() to allocate memory. If memory
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* allocation fails, or the parameters to this function are invalid,
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* NULL is returned.
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*
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* @param system an mspack_system structure used to read from
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* the input stream and write to the output
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* stream, also to allocate and free memory.
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* @param input an input stream with the LZX data.
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* @param output an output stream to write the decoded data to.
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* @param window_bits the size of the decoding window, which must be
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* between 15 and 21 inclusive.
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* @param reset_interval the interval at which the LZX bitstream is
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* reset, in multiples of LZX frames (32678
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* bytes), e.g. a value of 2 indicates the input
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* stream resets after every 65536 output bytes.
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* A value of 0 indicates that the bistream never
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* resets, such as in CAB LZX streams.
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* @param input_buffer_size the number of bytes to use as an input
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* bitstream buffer.
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* @param output_length the length in bytes of the entirely
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* decompressed output stream, if known in
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* advance. It is used to correctly perform the
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* Intel E8 transformation, which must stop 6
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* bytes before the very end of the
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* decompressed stream. It is not otherwise used
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* or adhered to. If the full decompressed
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* length is known in advance, set it here.
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* If it is NOT known, use the value 0, and call
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* lzxd_set_output_length() once it is
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* known. If never set, 4 of the final 6 bytes
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* of the output stream may be incorrect.
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* @return a pointer to an initialised lzxd_stream structure, or NULL if
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* there was not enough memory or parameters to the function were wrong.
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*/
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extern struct lzxd_stream *lzxd_init(struct mspack_system *system,
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struct mspack_file *input,
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struct mspack_file *output,
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int window_bits,
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int reset_interval,
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int input_buffer_size,
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off_t output_length);
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/* see description of output_length in lzxd_init() */
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extern void lzxd_set_output_length(struct lzxd_stream *lzx,
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off_t output_length);
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/**
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* Decompresses entire or partial LZX streams.
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*
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* The number of bytes of data that should be decompressed is given as the
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* out_bytes parameter.<EFBFBD>If more bytes are decoded than are needed, they
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* will be kept over for a later invocation.
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*
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* The output bytes will be passed to the system->write() function given in
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* lzxd_init(), using the output file handle given in lzxd_init(). More than
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* one call may be made to system->write().
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* Input bytes will be read in as necessary using the system->read()
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* function given in lzxd_init(), using the input file handle given in
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* lzxd_init(). This will continue until system->read() returns 0 bytes,
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* or an error. Errors will be passed out of the function as
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* MSPACK_ERR_READ errors. Input streams should convey an "end of input
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* stream" by refusing to supply all the bytes that LZX asks for when they
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* reach the end of the stream, rather than return an error code.
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*
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* If any error code other than MSPACK_ERR_OK is returned, the stream
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* should be considered unusable and lzxd_decompress() should not be
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* called again on this stream.
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*
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* @param lzx LZX decompression state, as allocated by lzxd_init().
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* @param out_bytes the number of bytes of data to decompress.
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* @return an error code, or MSPACK_ERR_OK if successful
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*/
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extern int lzxd_decompress(struct lzxd_stream *lzx, off_t out_bytes);
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/**
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* Frees all state associated with an LZX data stream. This will call
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* system->free() using the system pointer given in lzxd_init().
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*
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* @param lzx LZX decompression state to free.
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*/
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void lzxd_free(struct lzxd_stream *lzx);
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#ifdef __cplusplus
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}
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#endif
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#endif
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