v42bis.c
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/*
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* SpanDSP - a series of DSP components for telephony
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| 3 |
*
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| 4 |
* v42bis.c
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| 5 |
*
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* Written by Steve Underwood <steveu@coppice.org>
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*
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* Copyright (C) 2005 Steve Underwood
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*
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* All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License version 2.1,
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 19 |
* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this program; if not, write to the Free Software
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| 23 |
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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* $Id: v42bis.c,v 1.37 2009/02/10 13:06:47 steveu Exp $
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*/
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| 28 |
/* THIS IS A WORK IN PROGRESS. IT IS NOT FINISHED.
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Currently it performs the core compression and decompression functions OK.
|
| 30 |
However, a number of the bells and whistles in V.42bis are incomplete. */
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| 32 |
/*! \file */
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| 34 |
#if defined(HAVE_CONFIG_H)
|
| 35 |
#include "config.h" |
| 36 |
#endif
|
| 37 |
|
| 38 |
#include <stdio.h> |
| 39 |
#include <stdlib.h> |
| 40 |
#include <inttypes.h> |
| 41 |
#include <string.h> |
| 42 |
#include <errno.h> |
| 43 |
#include <fcntl.h> |
| 44 |
#include <ctype.h> |
| 45 |
#include <assert.h> |
| 46 |
|
| 47 |
#include "spandsp/telephony.h" |
| 48 |
#include "spandsp/logging.h" |
| 49 |
#include "spandsp/bit_operations.h" |
| 50 |
#include "spandsp/v42bis.h" |
| 51 |
|
| 52 |
#include "spandsp/private/logging.h" |
| 53 |
#include "spandsp/private/v42bis.h" |
| 54 |
|
| 55 |
/* Fixed parameters from the spec. */
|
| 56 |
#define V42BIS_N3 8 /* Character size (bits) */ |
| 57 |
#define V42BIS_N4 256 /* Number of characters in the alphabet */ |
| 58 |
#define V42BIS_N5 (V42BIS_N4 + V42BIS_N6) /* Index number of first dictionary entry used to store a string */ |
| 59 |
#define V42BIS_N6 3 /* Number of control codewords */ |
| 60 |
|
| 61 |
/* Control code words in compressed mode */
|
| 62 |
enum
|
| 63 |
{
|
| 64 |
V42BIS_ETM = 0, /* Enter transparent mode */ |
| 65 |
V42BIS_FLUSH = 1, /* Flush data */ |
| 66 |
V42BIS_STEPUP = 2 /* Step up codeword size */ |
| 67 |
}; |
| 68 |
|
| 69 |
/* Command codes in transparent mode */
|
| 70 |
enum
|
| 71 |
{
|
| 72 |
V42BIS_ECM = 0, /* Enter compression mode */ |
| 73 |
V42BIS_EID = 1, /* Escape character in data */ |
| 74 |
V42BIS_RESET = 2 /* Force reinitialisation */ |
| 75 |
}; |
| 76 |
|
| 77 |
static __inline__ void push_compressed_raw_octet(v42bis_compress_state_t *ss, int octet) |
| 78 |
{
|
| 79 |
ss->output_buf[ss->output_octet_count++] = (uint8_t) octet; |
| 80 |
if (ss->output_octet_count >= ss->max_len)
|
| 81 |
{
|
| 82 |
ss->handler(ss->user_data, ss->output_buf, ss->output_octet_count); |
| 83 |
ss->output_octet_count = 0;
|
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} |
| 85 |
} |
| 86 |
/*- End of function --------------------------------------------------------*/
|
| 87 |
|
| 88 |
static __inline__ void push_compressed_code(v42bis_compress_state_t *ss, int code) |
| 89 |
{
|
| 90 |
ss->output_bit_buffer |= code << (32 - ss->v42bis_parm_c2 - ss->output_bit_count);
|
| 91 |
ss->output_bit_count += ss->v42bis_parm_c2; |
| 92 |
while (ss->output_bit_count >= 8) |
| 93 |
{
|
| 94 |
push_compressed_raw_octet(ss, ss->output_bit_buffer >> 24);
|
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ss->output_bit_buffer <<= 8;
|
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ss->output_bit_count -= 8;
|
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} |
| 98 |
} |
| 99 |
/*- End of function --------------------------------------------------------*/
|
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|
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static __inline__ void push_compressed_octet(v42bis_compress_state_t *ss, int code) |
| 102 |
{
|
| 103 |
ss->output_bit_buffer |= code << (32 - 8 - ss->output_bit_count); |
| 104 |
ss->output_bit_count += 8;
|
| 105 |
while (ss->output_bit_count >= 8) |
| 106 |
{
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| 107 |
push_compressed_raw_octet(ss, ss->output_bit_buffer >> 24);
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ss->output_bit_buffer <<= 8;
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ss->output_bit_count -= 8;
|
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} |
| 111 |
} |
| 112 |
/*- End of function --------------------------------------------------------*/
|
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|
| 114 |
int v42bis_compress(v42bis_state_t *s, const uint8_t *buf, int len) |
| 115 |
{
|
| 116 |
int ptr;
|
| 117 |
int i;
|
| 118 |
uint32_t octet; |
| 119 |
uint32_t code; |
| 120 |
v42bis_compress_state_t *ss; |
| 121 |
|
| 122 |
ss = &s->compress; |
| 123 |
if ((s->v42bis_parm_p0 & 2) == 0) |
| 124 |
{
|
| 125 |
/* Compression is off - just push the incoming data out */
|
| 126 |
for (i = 0; i < len - ss->max_len; i += ss->max_len) |
| 127 |
ss->handler(ss->user_data, buf + i, ss->max_len); |
| 128 |
if (i < len)
|
| 129 |
ss->handler(ss->user_data, buf + i, len - i); |
| 130 |
return 0; |
| 131 |
} |
| 132 |
ptr = 0;
|
| 133 |
if (ss->first && len > 0) |
| 134 |
{
|
| 135 |
octet = buf[ptr++]; |
| 136 |
ss->string_code = octet + V42BIS_N6; |
| 137 |
if (ss->transparent)
|
| 138 |
push_compressed_octet(ss, octet); |
| 139 |
ss->first = FALSE; |
| 140 |
} |
| 141 |
while (ptr < len)
|
| 142 |
{
|
| 143 |
octet = buf[ptr++]; |
| 144 |
if ((ss->dict[ss->string_code].children[octet >> 5] & (1 << (octet & 0x1F)))) |
| 145 |
{
|
| 146 |
/* The leaf exists. Now find it in the table. */
|
| 147 |
/* TODO: This is a brute force scan for a match. We need something better. */
|
| 148 |
for (code = 0; code < ss->v42bis_parm_c3; code++) |
| 149 |
{
|
| 150 |
if (ss->dict[code].parent_code == ss->string_code && ss->dict[code].node_octet == octet)
|
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break;
|
| 152 |
} |
| 153 |
} |
| 154 |
else
|
| 155 |
{
|
| 156 |
/* The leaf does not exist. */
|
| 157 |
code = s->v42bis_parm_n2; |
| 158 |
} |
| 159 |
/* 6.3(b) If the string matches a dictionary entry, and the entry is not that entry
|
| 160 |
created by the last invocation of the string matching procedure, then the
|
| 161 |
next character shall be read and appended to the string and this step
|
| 162 |
repeated. */
|
| 163 |
if (code < ss->v42bis_parm_c3 && code != ss->latest_code)
|
| 164 |
{
|
| 165 |
/* The string was found */
|
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ss->string_code = code; |
| 167 |
ss->string_length++; |
| 168 |
} |
| 169 |
else
|
| 170 |
{
|
| 171 |
/* The string is not in the table. */
|
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if (!ss->transparent)
|
| 173 |
{
|
| 174 |
/* 7.4 Encoding - we now have the longest matchable string, and will need to output the code for it. */
|
| 175 |
while (ss->v42bis_parm_c1 >= ss->v42bis_parm_c3 && ss->v42bis_parm_c3 <= s->v42bis_parm_n2)
|
| 176 |
{
|
| 177 |
/* We need to increase the codeword size */
|
| 178 |
/* 7.4(a) */
|
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push_compressed_code(ss, V42BIS_STEPUP); |
| 180 |
/* 7.4(b) */
|
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ss->v42bis_parm_c2++; |
| 182 |
/* 7.4(c) */
|
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ss->v42bis_parm_c3 <<= 1;
|
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/* 7.4(d) this might need to be repeated, so we loop */
|
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} |
| 186 |
/* 7.5 Transfer - output the last state of the string */
|
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push_compressed_code(ss, ss->string_code); |
| 188 |
} |
| 189 |
/* 7.6 Dictionary updating */
|
| 190 |
/* 6.4 Add the string to the dictionary */
|
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/* 6.4(b) The string is not in the table. */
|
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if (code != ss->latest_code && ss->string_length < s->v42bis_parm_n7)
|
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{
|
| 194 |
ss->latest_code = ss->v42bis_parm_c1; |
| 195 |
/* 6.4(a) The length of the string is in range for adding to the dictionary */
|
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/* If the last code was a leaf, it no longer is */
|
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ss->dict[ss->string_code].leaves++; |
| 198 |
ss->dict[ss->string_code].children[octet >> 5] |= (1 << (octet & 0x1F)); |
| 199 |
/* The new one is definitely a leaf */
|
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ss->dict[ss->v42bis_parm_c1].parent_code = (uint16_t) ss->string_code; |
| 201 |
ss->dict[ss->v42bis_parm_c1].leaves = 0;
|
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ss->dict[ss->v42bis_parm_c1].node_octet = (uint8_t) octet; |
| 203 |
/* 7.7 Node recovery */
|
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/* 6.5 Recovering a dictionary entry to use next */
|
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for (;;)
|
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{
|
| 207 |
/* 6.5(a) and (b) */
|
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if ((int) (++ss->v42bis_parm_c1) >= s->v42bis_parm_n2) |
| 209 |
ss->v42bis_parm_c1 = V42BIS_N5; |
| 210 |
/* 6.5(c) We need to reuse a leaf node */
|
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if (ss->dict[ss->v42bis_parm_c1].leaves)
|
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continue;
|
| 213 |
if (ss->dict[ss->v42bis_parm_c1].parent_code == 0xFFFF) |
| 214 |
break;
|
| 215 |
/* 6.5(d) Detach the leaf node from its parent, and re-use it */
|
| 216 |
/* Possibly make the parent a leaf node again */
|
| 217 |
ss->dict[ss->dict[ss->v42bis_parm_c1].parent_code].leaves--; |
| 218 |
ss->dict[ss->dict[ss->v42bis_parm_c1].parent_code].children[ss->dict[ss->v42bis_parm_c1].node_octet >> 5] &= ~(1 << (ss->dict[ss->v42bis_parm_c1].node_octet & 0x1F)); |
| 219 |
ss->dict[ss->v42bis_parm_c1].parent_code = 0xFFFF;
|
| 220 |
break;
|
| 221 |
} |
| 222 |
} |
| 223 |
else
|
| 224 |
{
|
| 225 |
ss->latest_code = 0xFFFFFFFF;
|
| 226 |
} |
| 227 |
/* 7.8 Data compressibility test */
|
| 228 |
/* Filter on the balance of what went into the compressor, and what came out */
|
| 229 |
ss->compressibility_filter += ((((8*ss->string_length - ss->v42bis_parm_c2) << 20) - ss->compressibility_filter) >> 10); |
| 230 |
if (ss->compression_mode == V42BIS_COMPRESSION_MODE_DYNAMIC)
|
| 231 |
{
|
| 232 |
/* Work out if it is appropriate to change between transparent and
|
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compressed mode. */
|
| 234 |
if (ss->transparent)
|
| 235 |
{
|
| 236 |
if (ss->compressibility_filter > 0) |
| 237 |
{
|
| 238 |
if (++ss->compressibility_persistence > 1000) |
| 239 |
{
|
| 240 |
/* Schedule a switch to compressed mode */
|
| 241 |
ss->change_transparency = -1;
|
| 242 |
ss->compressibility_persistence = 0;
|
| 243 |
} |
| 244 |
} |
| 245 |
else
|
| 246 |
{
|
| 247 |
ss->compressibility_persistence = 0;
|
| 248 |
} |
| 249 |
} |
| 250 |
else
|
| 251 |
{
|
| 252 |
if (ss->compressibility_filter < 0) |
| 253 |
{
|
| 254 |
if (++ss->compressibility_persistence > 1000) |
| 255 |
{
|
| 256 |
/* Schedule a switch to transparent mode */
|
| 257 |
ss->change_transparency = 1;
|
| 258 |
ss->compressibility_persistence = 0;
|
| 259 |
} |
| 260 |
} |
| 261 |
else
|
| 262 |
{
|
| 263 |
ss->compressibility_persistence = 0;
|
| 264 |
} |
| 265 |
} |
| 266 |
} |
| 267 |
if (ss->change_transparency)
|
| 268 |
{
|
| 269 |
if (ss->change_transparency < 0) |
| 270 |
{
|
| 271 |
if (ss->transparent)
|
| 272 |
{
|
| 273 |
printf("Going compressed\n");
|
| 274 |
/* 7.8.1 Transition to compressed mode */
|
| 275 |
/* Switch out of transparent now, between codes. We need to send the octet which did not
|
| 276 |
match, just before switching. */
|
| 277 |
if (octet == ss->escape_code)
|
| 278 |
{
|
| 279 |
push_compressed_octet(ss, ss->escape_code++); |
| 280 |
push_compressed_octet(ss, V42BIS_EID); |
| 281 |
} |
| 282 |
else
|
| 283 |
{
|
| 284 |
push_compressed_octet(ss, octet); |
| 285 |
} |
| 286 |
push_compressed_octet(ss, ss->escape_code++); |
| 287 |
push_compressed_octet(ss, V42BIS_ECM); |
| 288 |
ss->transparent = FALSE; |
| 289 |
} |
| 290 |
} |
| 291 |
else
|
| 292 |
{
|
| 293 |
if (!ss->transparent)
|
| 294 |
{
|
| 295 |
printf("Going transparent\n");
|
| 296 |
/* 7.8.2 Transition to transparent mode */
|
| 297 |
/* Switch into transparent now, between codes, and the unmatched octet should
|
| 298 |
go out in transparent mode, just below */
|
| 299 |
push_compressed_code(ss, V42BIS_ETM); |
| 300 |
ss->transparent = TRUE; |
| 301 |
} |
| 302 |
} |
| 303 |
ss->change_transparency = 0;
|
| 304 |
} |
| 305 |
/* 7.8.3 Reset function - TODO */
|
| 306 |
ss->string_code = octet + V42BIS_N6; |
| 307 |
ss->string_length = 1;
|
| 308 |
} |
| 309 |
if (ss->transparent)
|
| 310 |
{
|
| 311 |
if (octet == ss->escape_code)
|
| 312 |
{
|
| 313 |
push_compressed_octet(ss, ss->escape_code++); |
| 314 |
push_compressed_octet(ss, V42BIS_EID); |
| 315 |
} |
| 316 |
else
|
| 317 |
{
|
| 318 |
push_compressed_octet(ss, octet); |
| 319 |
} |
| 320 |
} |
| 321 |
} |
| 322 |
return 0; |
| 323 |
} |
| 324 |
/*- End of function --------------------------------------------------------*/
|
| 325 |
|
| 326 |
int v42bis_compress_flush(v42bis_state_t *s)
|
| 327 |
{
|
| 328 |
v42bis_compress_state_t *ss; |
| 329 |
|
| 330 |
ss = &s->compress; |
| 331 |
if (!ss->transparent)
|
| 332 |
{
|
| 333 |
/* Output the last state of the string */
|
| 334 |
push_compressed_code(ss, ss->string_code); |
| 335 |
/* TODO: We use a positive FLUSH at all times. It is really needed, if the
|
| 336 |
previous step resulted in no leftover bits. */
|
| 337 |
push_compressed_code(ss, V42BIS_FLUSH); |
| 338 |
} |
| 339 |
while (ss->output_bit_count > 0) |
| 340 |
{
|
| 341 |
push_compressed_raw_octet(ss, ss->output_bit_buffer >> 24);
|
| 342 |
ss->output_bit_buffer <<= 8;
|
| 343 |
ss->output_bit_count -= 8;
|
| 344 |
} |
| 345 |
/* Now push out anything remaining. */
|
| 346 |
if (ss->output_octet_count > 0) |
| 347 |
{
|
| 348 |
ss->handler(ss->user_data, ss->output_buf, ss->output_octet_count); |
| 349 |
ss->output_octet_count = 0;
|
| 350 |
} |
| 351 |
return 0; |
| 352 |
} |
| 353 |
/*- End of function --------------------------------------------------------*/
|
| 354 |
|
| 355 |
#if 0
|
| 356 |
int v42bis_compress_dump(v42bis_state_t *s)
|
| 357 |
{
|
| 358 |
int i;
|
| 359 |
|
| 360 |
for (i = 0; i < V42BIS_MAX_CODEWORDS; i++)
|
| 361 |
{
|
| 362 |
if (s->compress.dict[i].parent_code != 0xFFFF)
|
| 363 |
{
|
| 364 |
printf("Entry %4x, prior %4x, leaves %d, octet %2x\n", i, s->compress.dict[i].parent_code, s->compress.dict[i].leaves, s->compress.dict[i].node_octet);
|
| 365 |
}
|
| 366 |
}
|
| 367 |
return 0;
|
| 368 |
}
|
| 369 |
/*- End of function --------------------------------------------------------*/
|
| 370 |
#endif
|
| 371 |
|
| 372 |
int v42bis_decompress(v42bis_state_t *s, const uint8_t *buf, int len) |
| 373 |
{
|
| 374 |
int ptr;
|
| 375 |
int i;
|
| 376 |
int this_length;
|
| 377 |
uint8_t *string; |
| 378 |
uint32_t code; |
| 379 |
uint32_t new_code; |
| 380 |
int code_len;
|
| 381 |
v42bis_decompress_state_t *ss; |
| 382 |
uint8_t decode_buf[V42BIS_MAX_STRING_SIZE]; |
| 383 |
|
| 384 |
ss = &s->decompress; |
| 385 |
if ((s->v42bis_parm_p0 & 1) == 0) |
| 386 |
{
|
| 387 |
/* Compression is off - just push the incoming data out */
|
| 388 |
for (i = 0; i < len - ss->max_len; i += ss->max_len) |
| 389 |
ss->handler(ss->user_data, buf + i, ss->max_len); |
| 390 |
if (i < len)
|
| 391 |
ss->handler(ss->user_data, buf + i, len - i); |
| 392 |
return 0; |
| 393 |
} |
| 394 |
ptr = 0;
|
| 395 |
code_len = (ss->transparent) ? 8 : ss->v42bis_parm_c2;
|
| 396 |
for (;;)
|
| 397 |
{
|
| 398 |
/* Fill up the bit buffer. */
|
| 399 |
while (ss->input_bit_count < 32 - 8 && ptr < len) |
| 400 |
{
|
| 401 |
ss->input_bit_count += 8;
|
| 402 |
ss->input_bit_buffer |= (uint32_t) buf[ptr++] << (32 - ss->input_bit_count);
|
| 403 |
} |
| 404 |
if (ss->input_bit_count < code_len)
|
| 405 |
break;
|
| 406 |
new_code = ss->input_bit_buffer >> (32 - code_len);
|
| 407 |
ss->input_bit_count -= code_len; |
| 408 |
ss->input_bit_buffer <<= code_len; |
| 409 |
if (ss->transparent)
|
| 410 |
{
|
| 411 |
code = new_code; |
| 412 |
if (ss->escaped)
|
| 413 |
{
|
| 414 |
ss->escaped = FALSE; |
| 415 |
if (code == V42BIS_ECM)
|
| 416 |
{
|
| 417 |
printf("Hit V42BIS_ECM\n");
|
| 418 |
ss->transparent = FALSE; |
| 419 |
code_len = ss->v42bis_parm_c2; |
| 420 |
} |
| 421 |
else if (code == V42BIS_EID) |
| 422 |
{
|
| 423 |
printf("Hit V42BIS_EID\n");
|
| 424 |
ss->output_buf[ss->output_octet_count++] = ss->escape_code - 1;
|
| 425 |
if (ss->output_octet_count >= ss->max_len - s->v42bis_parm_n7)
|
| 426 |
{
|
| 427 |
ss->handler(ss->user_data, ss->output_buf, ss->output_octet_count); |
| 428 |
ss->output_octet_count = 0;
|
| 429 |
} |
| 430 |
} |
| 431 |
else if (code == V42BIS_RESET) |
| 432 |
{
|
| 433 |
printf("Hit V42BIS_RESET\n");
|
| 434 |
} |
| 435 |
else
|
| 436 |
{
|
| 437 |
printf("Hit V42BIS_???? - %" PRIu32 "\n", code); |
| 438 |
} |
| 439 |
} |
| 440 |
else if (code == ss->escape_code) |
| 441 |
{
|
| 442 |
ss->escape_code++; |
| 443 |
ss->escaped = TRUE; |
| 444 |
} |
| 445 |
else
|
| 446 |
{
|
| 447 |
ss->output_buf[ss->output_octet_count++] = (uint8_t) code; |
| 448 |
if (ss->output_octet_count >= ss->max_len - s->v42bis_parm_n7)
|
| 449 |
{
|
| 450 |
ss->handler(ss->user_data, ss->output_buf, ss->output_octet_count); |
| 451 |
ss->output_octet_count = 0;
|
| 452 |
} |
| 453 |
} |
| 454 |
} |
| 455 |
else
|
| 456 |
{
|
| 457 |
if (new_code < V42BIS_N6)
|
| 458 |
{
|
| 459 |
/* We have a control code. */
|
| 460 |
switch (new_code)
|
| 461 |
{
|
| 462 |
case V42BIS_ETM:
|
| 463 |
printf("Hit V42BIS_ETM\n");
|
| 464 |
ss->transparent = TRUE; |
| 465 |
code_len = 8;
|
| 466 |
break;
|
| 467 |
case V42BIS_FLUSH:
|
| 468 |
printf("Hit V42BIS_FLUSH\n");
|
| 469 |
v42bis_decompress_flush(s); |
| 470 |
break;
|
| 471 |
case V42BIS_STEPUP:
|
| 472 |
/* We need to increase the codeword size */
|
| 473 |
printf("Hit V42BIS_STEPUP\n");
|
| 474 |
if (ss->v42bis_parm_c3 >= s->v42bis_parm_n2)
|
| 475 |
{
|
| 476 |
/* Invalid condition */
|
| 477 |
return -1; |
| 478 |
} |
| 479 |
code_len = ++ss->v42bis_parm_c2; |
| 480 |
ss->v42bis_parm_c3 <<= 1;
|
| 481 |
break;
|
| 482 |
} |
| 483 |
continue;
|
| 484 |
} |
| 485 |
if (ss->first)
|
| 486 |
{
|
| 487 |
ss->first = FALSE; |
| 488 |
ss->octet = new_code - V42BIS_N6; |
| 489 |
ss->output_buf[0] = (uint8_t) ss->octet;
|
| 490 |
ss->output_octet_count = 1;
|
| 491 |
if (ss->output_octet_count >= ss->max_len - s->v42bis_parm_n7)
|
| 492 |
{
|
| 493 |
ss->handler(ss->user_data, ss->output_buf, ss->output_octet_count); |
| 494 |
ss->output_octet_count = 0;
|
| 495 |
} |
| 496 |
ss->old_code = new_code; |
| 497 |
continue;
|
| 498 |
} |
| 499 |
/* Start at the end of the buffer, and decode backwards */
|
| 500 |
string = &decode_buf[V42BIS_MAX_STRING_SIZE - 1];
|
| 501 |
/* Check the received code is valid. It can't be too big, as we pulled only the expected number
|
| 502 |
of bits from the input stream. It could, however, be unknown. */
|
| 503 |
if (ss->dict[new_code].parent_code == 0xFFFF) |
| 504 |
return -1; |
| 505 |
/* Otherwise we do a straight decode of the new code. */
|
| 506 |
code = new_code; |
| 507 |
/* Trace back through the octets which form the string, and output them. */
|
| 508 |
while (code >= V42BIS_N5)
|
| 509 |
{
|
| 510 |
if (code > 4095) {printf("Code is 0x%" PRIu32 "\n", code); exit(2);} |
| 511 |
*string-- = ss->dict[code].node_octet; |
| 512 |
code = ss->dict[code].parent_code; |
| 513 |
} |
| 514 |
*string = (uint8_t) (code - V42BIS_N6); |
| 515 |
ss->octet = code - V42BIS_N6; |
| 516 |
/* Output the decoded string. */
|
| 517 |
this_length = V42BIS_MAX_STRING_SIZE - (int) (string - decode_buf);
|
| 518 |
memcpy(ss->output_buf + ss->output_octet_count, string, this_length); |
| 519 |
ss->output_octet_count += this_length; |
| 520 |
if (ss->output_octet_count >= ss->max_len - s->v42bis_parm_n7)
|
| 521 |
{
|
| 522 |
ss->handler(ss->user_data, ss->output_buf, ss->output_octet_count); |
| 523 |
ss->output_octet_count = 0;
|
| 524 |
} |
| 525 |
/* 6.4 Add the string to the dictionary */
|
| 526 |
if (ss->last_length < s->v42bis_parm_n7)
|
| 527 |
{
|
| 528 |
/* 6.4(a) The string does not exceed N7 in length */
|
| 529 |
if (ss->last_old_code != ss->old_code
|
| 530 |
|| |
| 531 |
ss->last_extra_octet != *string) |
| 532 |
{
|
| 533 |
/* 6.4(b) The string is not in the table. */
|
| 534 |
ss->dict[ss->old_code].leaves++; |
| 535 |
/* The new one is definitely a leaf */
|
| 536 |
ss->dict[ss->v42bis_parm_c1].parent_code = (uint16_t) ss->old_code; |
| 537 |
ss->dict[ss->v42bis_parm_c1].leaves = 0;
|
| 538 |
ss->dict[ss->v42bis_parm_c1].node_octet = (uint8_t) ss->octet; |
| 539 |
/* 6.5 Recovering a dictionary entry to use next */
|
| 540 |
for (;;)
|
| 541 |
{
|
| 542 |
/* 6.5(a) and (b) */
|
| 543 |
if (++ss->v42bis_parm_c1 >= s->v42bis_parm_n2)
|
| 544 |
ss->v42bis_parm_c1 = V42BIS_N5; |
| 545 |
/* 6.5(c) We need to reuse a leaf node */
|
| 546 |
if (ss->dict[ss->v42bis_parm_c1].leaves)
|
| 547 |
continue;
|
| 548 |
/* 6.5(d) This is a leaf node, so re-use it */
|
| 549 |
/* Possibly make the parent a leaf node again */
|
| 550 |
if (ss->dict[ss->v42bis_parm_c1].parent_code != 0xFFFF) |
| 551 |
ss->dict[ss->dict[ss->v42bis_parm_c1].parent_code].leaves--; |
| 552 |
ss->dict[ss->v42bis_parm_c1].parent_code = 0xFFFF;
|
| 553 |
break;
|
| 554 |
} |
| 555 |
} |
| 556 |
} |
| 557 |
/* Record the addition to the dictionary, so we can check for repeat attempts
|
| 558 |
at the next code - see II.4.3 */
|
| 559 |
ss->last_old_code = ss->old_code; |
| 560 |
ss->last_extra_octet = *string; |
| 561 |
|
| 562 |
ss->old_code = new_code; |
| 563 |
ss->last_length = this_length; |
| 564 |
} |
| 565 |
} |
| 566 |
return 0; |
| 567 |
} |
| 568 |
/*- End of function --------------------------------------------------------*/
|
| 569 |
|
| 570 |
int v42bis_decompress_flush(v42bis_state_t *s)
|
| 571 |
{
|
| 572 |
v42bis_decompress_state_t *ss; |
| 573 |
|
| 574 |
ss = &s->decompress; |
| 575 |
/* Push out anything remaining. */
|
| 576 |
if (ss->output_octet_count > 0) |
| 577 |
{
|
| 578 |
ss->handler(ss->user_data, ss->output_buf, ss->output_octet_count); |
| 579 |
ss->output_octet_count = 0;
|
| 580 |
} |
| 581 |
return 0; |
| 582 |
} |
| 583 |
/*- End of function --------------------------------------------------------*/
|
| 584 |
|
| 585 |
#if 0
|
| 586 |
int v42bis_decompress_dump(v42bis_state_t *s)
|
| 587 |
{
|
| 588 |
int i;
|
| 589 |
|
| 590 |
for (i = 0; i < V42BIS_MAX_CODEWORDS; i++)
|
| 591 |
{
|
| 592 |
if (s->decompress.dict[i].parent_code != 0xFFFF)
|
| 593 |
{
|
| 594 |
printf("Entry %4x, prior %4x, leaves %d, octet %2x\n", i, s->decompress.dict[i].parent_code, s->decompress.dict[i].leaves, s->decompress.dict[i].node_octet);
|
| 595 |
}
|
| 596 |
}
|
| 597 |
return 0;
|
| 598 |
}
|
| 599 |
/*- End of function --------------------------------------------------------*/
|
| 600 |
#endif
|
| 601 |
|
| 602 |
void v42bis_compression_control(v42bis_state_t *s, int mode) |
| 603 |
{
|
| 604 |
s->compress.compression_mode = mode; |
| 605 |
switch (mode)
|
| 606 |
{
|
| 607 |
case V42BIS_COMPRESSION_MODE_ALWAYS:
|
| 608 |
s->compress.change_transparency = -1;
|
| 609 |
break;
|
| 610 |
case V42BIS_COMPRESSION_MODE_NEVER:
|
| 611 |
s->compress.change_transparency = 1;
|
| 612 |
break;
|
| 613 |
} |
| 614 |
} |
| 615 |
/*- End of function --------------------------------------------------------*/
|
| 616 |
|
| 617 |
v42bis_state_t *v42bis_init(v42bis_state_t *s, |
| 618 |
int negotiated_p0,
|
| 619 |
int negotiated_p1,
|
| 620 |
int negotiated_p2,
|
| 621 |
v42bis_frame_handler_t frame_handler, |
| 622 |
void *frame_user_data,
|
| 623 |
int max_frame_len,
|
| 624 |
v42bis_data_handler_t data_handler, |
| 625 |
void *data_user_data,
|
| 626 |
int max_data_len)
|
| 627 |
{
|
| 628 |
int i;
|
| 629 |
|
| 630 |
if (negotiated_p1 < 512 || negotiated_p1 > 65535) |
| 631 |
return NULL; |
| 632 |
if (negotiated_p2 < 6 || negotiated_p2 > V42BIS_MAX_STRING_SIZE) |
| 633 |
return NULL; |
| 634 |
if (s == NULL) |
| 635 |
{
|
| 636 |
if ((s = (v42bis_state_t *) malloc(sizeof(*s))) == NULL) |
| 637 |
return NULL; |
| 638 |
} |
| 639 |
memset(s, 0, sizeof(*s)); |
| 640 |
|
| 641 |
s->compress.handler = frame_handler; |
| 642 |
s->compress.user_data = frame_user_data; |
| 643 |
s->compress.max_len = (max_frame_len < 1024) ? max_frame_len : 1024; |
| 644 |
|
| 645 |
s->decompress.handler = data_handler; |
| 646 |
s->decompress.user_data = data_user_data; |
| 647 |
s->decompress.max_len = (max_data_len < 1024) ? max_data_len : 1024; |
| 648 |
|
| 649 |
s->v42bis_parm_p0 = negotiated_p0; /* default is both ways off */
|
| 650 |
|
| 651 |
s->v42bis_parm_n1 = top_bit(negotiated_p1 - 1) + 1; |
| 652 |
s->v42bis_parm_n2 = negotiated_p1; |
| 653 |
s->v42bis_parm_n7 = negotiated_p2; |
| 654 |
|
| 655 |
/* 6.5 */
|
| 656 |
s->compress.v42bis_parm_c1 = |
| 657 |
s->decompress.v42bis_parm_c1 = V42BIS_N5; |
| 658 |
|
| 659 |
s->compress.v42bis_parm_c2 = |
| 660 |
s->decompress.v42bis_parm_c2 = V42BIS_N3 + 1;
|
| 661 |
|
| 662 |
s->compress.v42bis_parm_c3 = |
| 663 |
s->decompress.v42bis_parm_c3 = 2*V42BIS_N4;
|
| 664 |
|
| 665 |
s->compress.first = |
| 666 |
s->decompress.first = TRUE; |
| 667 |
for (i = 0; i < V42BIS_MAX_CODEWORDS; i++) |
| 668 |
{
|
| 669 |
s->compress.dict[i].parent_code = |
| 670 |
s->decompress.dict[i].parent_code = 0xFFFF;
|
| 671 |
s->compress.dict[i].leaves = |
| 672 |
s->decompress.dict[i].leaves = 0;
|
| 673 |
} |
| 674 |
/* Point the root nodes for decompression to themselves. It doesn't matter much what
|
| 675 |
they are set to, as long as they are considered "known" codes. */
|
| 676 |
for (i = 0; i < V42BIS_N5; i++) |
| 677 |
s->decompress.dict[i].parent_code = (uint16_t) i; |
| 678 |
s->compress.string_code = 0xFFFFFFFF;
|
| 679 |
s->compress.latest_code = 0xFFFFFFFF;
|
| 680 |
|
| 681 |
s->decompress.last_old_code = 0xFFFFFFFF;
|
| 682 |
s->decompress.last_extra_octet = -1;
|
| 683 |
|
| 684 |
s->compress.compression_mode = V42BIS_COMPRESSION_MODE_DYNAMIC; |
| 685 |
|
| 686 |
return s;
|
| 687 |
} |
| 688 |
/*- End of function --------------------------------------------------------*/
|
| 689 |
|
| 690 |
int v42bis_release(v42bis_state_t *s)
|
| 691 |
{
|
| 692 |
return 0; |
| 693 |
} |
| 694 |
/*- End of function --------------------------------------------------------*/
|
| 695 |
|
| 696 |
int v42bis_free(v42bis_state_t *s)
|
| 697 |
{
|
| 698 |
free(s); |
| 699 |
return 0; |
| 700 |
} |
| 701 |
/*- End of function --------------------------------------------------------*/
|
| 702 |
/*- End of file ------------------------------------------------------------*/
|
