1 /* This file is part of libmspack. 2 * (C) 2003-2004 Stuart Caie. 3 * 4 * The Quantum method was created by David Stafford, adapted by Microsoft 5 * Corporation. 6 * 7 * libmspack is free software; you can redistribute it and/or modify it under 8 * the terms of the GNU Lesser General Public License (LGPL) version 2.1 9 * 10 * For further details, see the file COPYING.LIB distributed with libmspack 11 */ 12 13 #ifndef MSPACK_QTM_H 14 #define MSPACK_QTM_H 1 15 16 #ifdef __cplusplus 17 extern "C" { 18 #endif 19 20 /* Quantum compression / decompression definitions */ 21 22 #define QTM_FRAME_SIZE (32768) 23 24 struct qtmd_modelsym { 25 unsigned short sym, cumfreq; 26 }; 27 28 struct qtmd_model { 29 int shiftsleft, entries; 30 struct qtmd_modelsym *syms; 31 }; 32 33 struct qtmd_stream { 34 struct mspack_system *sys; /* I/O routines */ 35 struct mspack_file *input; /* input file handle */ 36 struct mspack_file *output; /* output file handle */ 37 38 unsigned char *window; /* decoding window */ 39 unsigned int window_size; /* window size */ 40 unsigned int window_posn; /* decompression offset within window */ 41 unsigned int frame_todo; /* bytes remaining for current frame */ 42 43 unsigned short H, L, C; /* high/low/current: arith coding state */ 44 unsigned char header_read; /* have we started decoding a new frame? */ 45 46 int error; 47 48 /* I/O buffers */ 49 unsigned char *inbuf, *i_ptr, *i_end, *o_ptr, *o_end; 50 unsigned int bit_buffer, inbuf_size; 51 unsigned char bits_left, input_end; 52 53 /* four literal models, each representing 64 symbols 54 * model0 for literals from 0 to 63 (selector = 0) 55 * model1 for literals from 64 to 127 (selector = 1) 56 * model2 for literals from 128 to 191 (selector = 2) 57 * model3 for literals from 129 to 255 (selector = 3) */ 58 struct qtmd_model model0, model1, model2, model3; 59 60 /* three match models. 61 * model4 for match with fixed length of 3 bytes 62 * model5 for match with fixed length of 4 bytes 63 * model6 for variable length match, encoded with model6len model */ 64 struct qtmd_model model4, model5, model6, model6len; 65 66 /* selector model. 0-6 to say literal (0,1,2,3) or match (4,5,6) */ 67 struct qtmd_model model7; 68 69 /* symbol arrays for all models */ 70 struct qtmd_modelsym m0sym[64 + 1]; 71 struct qtmd_modelsym m1sym[64 + 1]; 72 struct qtmd_modelsym m2sym[64 + 1]; 73 struct qtmd_modelsym m3sym[64 + 1]; 74 struct qtmd_modelsym m4sym[24 + 1]; 75 struct qtmd_modelsym m5sym[36 + 1]; 76 struct qtmd_modelsym m6sym[42 + 1], m6lsym[27 + 1]; 77 struct qtmd_modelsym m7sym[7 + 1]; 78 }; 79 80 /* allocates Quantum decompression state for decoding the given stream. 81 * 82 * - returns NULL if window_bits is outwith the range 10 to 21 (inclusive). 83 * 84 * - uses system->alloc() to allocate memory 85 * 86 * - returns NULL if not enough memory 87 * 88 * - window_bits is the size of the Quantum window, from 1Kb (10) to 2Mb (21). 89 * 90 * - input_buffer_size is the number of bytes to use to store bitstream data. 91 */ 92 extern struct qtmd_stream *qtmd_init(struct mspack_system *system, 93 struct mspack_file *input, 94 struct mspack_file *output, 95 int window_bits, 96 int input_buffer_size); 97 98 /* decompresses, or decompresses more of, a Quantum stream. 99 * 100 * - out_bytes of data will be decompressed and the function will return 101 * with an MSPACK_ERR_OK return code. 102 * 103 * - decompressing will stop as soon as out_bytes is reached. if the true 104 * amount of bytes decoded spills over that amount, they will be kept for 105 * a later invocation of qtmd_decompress(). 106 * 107 * - the output bytes will be passed to the system->write() function given in 108 * qtmd_init(), using the output file handle given in qtmd_init(). More 109 * than one call may be made to system->write() 110 * 111 * - Quantum will read input bytes as necessary using the system->read() 112 * function given in qtmd_init(), using the input file handle given in 113 * qtmd_init(). This will continue until system->read() returns 0 bytes, 114 * or an error. 115 */ 116 extern int qtmd_decompress(struct qtmd_stream *qtm, off_t out_bytes); 117 118 /* frees all state associated with a Quantum data stream 119 * 120 * - calls system->free() using the system pointer given in qtmd_init() 121 */ 122 void qtmd_free(struct qtmd_stream *qtm); 123 124 #ifdef __cplusplus 125 } 126 #endif 127 128 #endif 129