1 /*- 2 * Copyright (c) 1985, 1986, 1992, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Diomidis Spinellis and James A. Woods, derived from original 7 * work by Spencer Thomas and Joseph Orost. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. All advertising materials mentioning features or use of this software 18 * must display the following acknowledgement: 19 * This product includes software developed by the University of 20 * California, Berkeley and its contributors. 21 * 4. Neither the name of the University nor the names of its contributors 22 * may be used to endorse or promote products derived from this software 23 * without specific prior written permission. 24 * 25 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 28 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 29 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 33 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 34 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 35 * SUCH DAMAGE. 36 * 37 * @(#)zopen.c 8.1 (Berkeley) 6/27/93 38 * $FreeBSD: src/usr.bin/compress/zopen.c,v 1.5.6.1 2002/07/16 00:52:08 tjr Exp $ 39 * $DragonFly: src/usr.bin/compress/zopen.c,v 1.3 2003/10/02 17:42:27 hmp Exp $ 40 */ 41 42 /*- 43 * fcompress.c - File compression ala IEEE Computer, June 1984. 44 * 45 * Compress authors: 46 * Spencer W. Thomas (decvax!utah-cs!thomas) 47 * Jim McKie (decvax!mcvax!jim) 48 * Steve Davies (decvax!vax135!petsd!peora!srd) 49 * Ken Turkowski (decvax!decwrl!turtlevax!ken) 50 * James A. Woods (decvax!ihnp4!ames!jaw) 51 * Joe Orost (decvax!vax135!petsd!joe) 52 * 53 * Cleaned up and converted to library returning I/O streams by 54 * Diomidis Spinellis <dds@doc.ic.ac.uk>. 55 * 56 * zopen(filename, mode, bits) 57 * Returns a FILE * that can be used for read or write. The modes 58 * supported are only "r" and "w". Seeking is not allowed. On 59 * reading the file is decompressed, on writing it is compressed. 60 * The output is compatible with compress(1) with 16 bit tables. 61 * Any file produced by compress(1) can be read. 62 */ 63 64 #include <sys/param.h> 65 #include <sys/stat.h> 66 67 #include <ctype.h> 68 #include <errno.h> 69 #include <signal.h> 70 #include <stdio.h> 71 #include <stdlib.h> 72 #include <string.h> 73 #include <unistd.h> 74 #include "zopen.h" 75 76 #define BITS 16 /* Default bits. */ 77 #define HSIZE 69001 /* 95% occupancy */ 78 79 /* A code_int must be able to hold 2**BITS values of type int, and also -1. */ 80 typedef long code_int; 81 typedef long count_int; 82 83 typedef u_char char_type; 84 static char_type magic_header[] = 85 {'\037', '\235'}; /* 1F 9D */ 86 87 #define BIT_MASK 0x1f /* Defines for third byte of header. */ 88 #define BLOCK_MASK 0x80 89 90 /* 91 * Masks 0x40 and 0x20 are free. I think 0x20 should mean that there is 92 * a fourth header byte (for expansion). 93 */ 94 #define INIT_BITS 9 /* Initial number of bits/code. */ 95 96 #define MAXCODE(n_bits) ((1 << (n_bits)) - 1) 97 98 struct s_zstate { 99 FILE *zs_fp; /* File stream for I/O */ 100 char zs_mode; /* r or w */ 101 enum { 102 S_START, S_MIDDLE, S_EOF 103 } zs_state; /* State of computation */ 104 u_int zs_n_bits; /* Number of bits/code. */ 105 u_int zs_maxbits; /* User settable max # bits/code. */ 106 code_int zs_maxcode; /* Maximum code, given n_bits. */ 107 code_int zs_maxmaxcode; /* Should NEVER generate this code. */ 108 count_int zs_htab [HSIZE]; 109 u_short zs_codetab [HSIZE]; 110 code_int zs_hsize; /* For dynamic table sizing. */ 111 code_int zs_free_ent; /* First unused entry. */ 112 /* 113 * Block compression parameters -- after all codes are used up, 114 * and compression rate changes, start over. 115 */ 116 int zs_block_compress; 117 int zs_clear_flg; 118 long zs_ratio; 119 count_int zs_checkpoint; 120 u_int zs_offset; 121 long zs_in_count; /* Length of input. */ 122 long zs_bytes_out; /* Length of compressed output. */ 123 long zs_out_count; /* # of codes output (for debugging). */ 124 char_type zs_buf[BITS]; 125 union { 126 struct { 127 long zs_fcode; 128 code_int zs_ent; 129 code_int zs_hsize_reg; 130 int zs_hshift; 131 } w; /* Write paramenters */ 132 struct { 133 char_type *zs_stackp; 134 int zs_finchar; 135 code_int zs_code, zs_oldcode, zs_incode; 136 int zs_roffset, zs_size; 137 char_type zs_gbuf[BITS]; 138 } r; /* Read parameters */ 139 } u; 140 }; 141 142 /* Definitions to retain old variable names */ 143 #define fp zs->zs_fp 144 #define zmode zs->zs_mode 145 #define state zs->zs_state 146 #define n_bits zs->zs_n_bits 147 #define maxbits zs->zs_maxbits 148 #define maxcode zs->zs_maxcode 149 #define maxmaxcode zs->zs_maxmaxcode 150 #define htab zs->zs_htab 151 #define codetab zs->zs_codetab 152 #define hsize zs->zs_hsize 153 #define free_ent zs->zs_free_ent 154 #define block_compress zs->zs_block_compress 155 #define clear_flg zs->zs_clear_flg 156 #define ratio zs->zs_ratio 157 #define checkpoint zs->zs_checkpoint 158 #define offset zs->zs_offset 159 #define in_count zs->zs_in_count 160 #define bytes_out zs->zs_bytes_out 161 #define out_count zs->zs_out_count 162 #define buf zs->zs_buf 163 #define fcode zs->u.w.zs_fcode 164 #define hsize_reg zs->u.w.zs_hsize_reg 165 #define ent zs->u.w.zs_ent 166 #define hshift zs->u.w.zs_hshift 167 #define stackp zs->u.r.zs_stackp 168 #define finchar zs->u.r.zs_finchar 169 #define code zs->u.r.zs_code 170 #define oldcode zs->u.r.zs_oldcode 171 #define incode zs->u.r.zs_incode 172 #define roffset zs->u.r.zs_roffset 173 #define size zs->u.r.zs_size 174 #define gbuf zs->u.r.zs_gbuf 175 176 /* 177 * To save much memory, we overlay the table used by compress() with those 178 * used by decompress(). The tab_prefix table is the same size and type as 179 * the codetab. The tab_suffix table needs 2**BITS characters. We get this 180 * from the beginning of htab. The output stack uses the rest of htab, and 181 * contains characters. There is plenty of room for any possible stack 182 * (stack used to be 8000 characters). 183 */ 184 185 #define htabof(i) htab[i] 186 #define codetabof(i) codetab[i] 187 188 #define tab_prefixof(i) codetabof(i) 189 #define tab_suffixof(i) ((char_type *)(htab))[i] 190 #define de_stack ((char_type *)&tab_suffixof(1 << BITS)) 191 192 #define CHECK_GAP 10000 /* Ratio check interval. */ 193 194 /* 195 * the next two codes should not be changed lightly, as they must not 196 * lie within the contiguous general code space. 197 */ 198 #define FIRST 257 /* First free entry. */ 199 #define CLEAR 256 /* Table clear output code. */ 200 201 static int cl_block(struct s_zstate *); 202 static void cl_hash(struct s_zstate *, count_int); 203 static code_int getcode(struct s_zstate *); 204 static int output(struct s_zstate *, code_int); 205 static int zclose(void *); 206 static int zread(void *, char *, int); 207 static int zwrite(void *, const char *, int); 208 209 /*- 210 * Algorithm from "A Technique for High Performance Data Compression", 211 * Terry A. Welch, IEEE Computer Vol 17, No 6 (June 1984), pp 8-19. 212 * 213 * Algorithm: 214 * Modified Lempel-Ziv method (LZW). Basically finds common 215 * substrings and replaces them with a variable size code. This is 216 * deterministic, and can be done on the fly. Thus, the decompression 217 * procedure needs no input table, but tracks the way the table was built. 218 */ 219 220 /*- 221 * compress write 222 * 223 * Algorithm: use open addressing double hashing (no chaining) on the 224 * prefix code / next character combination. We do a variant of Knuth's 225 * algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime 226 * secondary probe. Here, the modular division first probe is gives way 227 * to a faster exclusive-or manipulation. Also do block compression with 228 * an adaptive reset, whereby the code table is cleared when the compression 229 * ratio decreases, but after the table fills. The variable-length output 230 * codes are re-sized at this point, and a special CLEAR code is generated 231 * for the decompressor. Late addition: construct the table according to 232 * file size for noticeable speed improvement on small files. Please direct 233 * questions about this implementation to ames!jaw. 234 */ 235 static int 236 zwrite(void *cookie, const char *wbp, int num) 237 { 238 code_int i; 239 int c, disp; 240 struct s_zstate *zs; 241 const u_char *bp; 242 u_char tmp; 243 int count; 244 245 if (num == 0) 246 return (0); 247 248 zs = cookie; 249 count = num; 250 bp = wbp; 251 if (state == S_MIDDLE) 252 goto middle; 253 state = S_MIDDLE; 254 255 maxmaxcode = 1L << maxbits; 256 if (fwrite(magic_header, 257 sizeof(char), sizeof(magic_header), fp) != sizeof(magic_header)) 258 return (-1); 259 tmp = (u_char)((maxbits) | block_compress); 260 if (fwrite(&tmp, sizeof(char), sizeof(tmp), fp) != sizeof(tmp)) 261 return (-1); 262 263 offset = 0; 264 bytes_out = 3; /* Includes 3-byte header mojo. */ 265 out_count = 0; 266 clear_flg = 0; 267 ratio = 0; 268 in_count = 1; 269 checkpoint = CHECK_GAP; 270 maxcode = MAXCODE(n_bits = INIT_BITS); 271 free_ent = ((block_compress) ? FIRST : 256); 272 273 ent = *bp++; 274 --count; 275 276 hshift = 0; 277 for (fcode = (long)hsize; fcode < 65536L; fcode *= 2L) 278 hshift++; 279 hshift = 8 - hshift; /* Set hash code range bound. */ 280 281 hsize_reg = hsize; 282 cl_hash(zs, (count_int)hsize_reg); /* Clear hash table. */ 283 284 middle: for (i = 0; count--;) { 285 c = *bp++; 286 in_count++; 287 fcode = (long)(((long)c << maxbits) + ent); 288 i = ((c << hshift) ^ ent); /* Xor hashing. */ 289 290 if (htabof(i) == fcode) { 291 ent = codetabof(i); 292 continue; 293 } else if ((long)htabof(i) < 0) /* Empty slot. */ 294 goto nomatch; 295 disp = hsize_reg - i; /* Secondary hash (after G. Knott). */ 296 if (i == 0) 297 disp = 1; 298 probe: if ((i -= disp) < 0) 299 i += hsize_reg; 300 301 if (htabof(i) == fcode) { 302 ent = codetabof(i); 303 continue; 304 } 305 if ((long)htabof(i) >= 0) 306 goto probe; 307 nomatch: if (output(zs, (code_int) ent) == -1) 308 return (-1); 309 out_count++; 310 ent = c; 311 if (free_ent < maxmaxcode) { 312 codetabof(i) = free_ent++; /* code -> hashtable */ 313 htabof(i) = fcode; 314 } else if ((count_int)in_count >= 315 checkpoint && block_compress) { 316 if (cl_block(zs) == -1) 317 return (-1); 318 } 319 } 320 return (num); 321 } 322 323 static int 324 zclose(void *cookie) 325 { 326 struct s_zstate *zs; 327 int rval; 328 329 zs = cookie; 330 if (zmode == 'w') { /* Put out the final code. */ 331 if (output(zs, (code_int) ent) == -1) { 332 (void)fclose(fp); 333 free(zs); 334 return (-1); 335 } 336 out_count++; 337 if (output(zs, (code_int) - 1) == -1) { 338 (void)fclose(fp); 339 free(zs); 340 return (-1); 341 } 342 } 343 rval = fclose(fp) == EOF ? -1 : 0; 344 free(zs); 345 return (rval); 346 } 347 348 /*- 349 * Output the given code. 350 * Inputs: 351 * code: A n_bits-bit integer. If == -1, then EOF. This assumes 352 * that n_bits =< (long)wordsize - 1. 353 * Outputs: 354 * Outputs code to the file. 355 * Assumptions: 356 * Chars are 8 bits long. 357 * Algorithm: 358 * Maintain a BITS character long buffer (so that 8 codes will 359 * fit in it exactly). Use the VAX insv instruction to insert each 360 * code in turn. When the buffer fills up empty it and start over. 361 */ 362 363 static char_type lmask[9] = 364 {0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80, 0x00}; 365 static char_type rmask[9] = 366 {0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff}; 367 368 static int 369 output(struct s_zstate *zs, code_int ocode) 370 { 371 int r_off; 372 u_int bits; 373 char_type *bp; 374 375 r_off = offset; 376 bits = n_bits; 377 bp = buf; 378 if (ocode >= 0) { 379 /* Get to the first byte. */ 380 bp += (r_off >> 3); 381 r_off &= 7; 382 /* 383 * Since ocode is always >= 8 bits, only need to mask the first 384 * hunk on the left. 385 */ 386 *bp = (*bp & rmask[r_off]) | ((ocode << r_off) & lmask[r_off]); 387 bp++; 388 bits -= (8 - r_off); 389 ocode >>= 8 - r_off; 390 /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */ 391 if (bits >= 8) { 392 *bp++ = ocode; 393 ocode >>= 8; 394 bits -= 8; 395 } 396 /* Last bits. */ 397 if (bits) 398 *bp = ocode; 399 offset += n_bits; 400 if (offset == (n_bits << 3)) { 401 bp = buf; 402 bits = n_bits; 403 bytes_out += bits; 404 if (fwrite(bp, sizeof(char), bits, fp) != bits) 405 return (-1); 406 bp += bits; 407 bits = 0; 408 offset = 0; 409 } 410 /* 411 * If the next entry is going to be too big for the ocode size, 412 * then increase it, if possible. 413 */ 414 if (free_ent > maxcode || (clear_flg > 0)) { 415 /* 416 * Write the whole buffer, because the input side won't 417 * discover the size increase until after it has read it. 418 */ 419 if (offset > 0) { 420 if (fwrite(buf, 1, n_bits, fp) != n_bits) 421 return (-1); 422 bytes_out += n_bits; 423 } 424 offset = 0; 425 426 if (clear_flg) { 427 maxcode = MAXCODE(n_bits = INIT_BITS); 428 clear_flg = 0; 429 } else { 430 n_bits++; 431 if (n_bits == maxbits) 432 maxcode = maxmaxcode; 433 else 434 maxcode = MAXCODE(n_bits); 435 } 436 } 437 } else { 438 /* At EOF, write the rest of the buffer. */ 439 if (offset > 0) { 440 offset = (offset + 7) / 8; 441 if (fwrite(buf, 1, offset, fp) != offset) 442 return (-1); 443 bytes_out += offset; 444 } 445 offset = 0; 446 } 447 return (0); 448 } 449 450 /* 451 * Decompress read. This routine adapts to the codes in the file building 452 * the "string" table on-the-fly; requiring no table to be stored in the 453 * compressed file. The tables used herein are shared with those of the 454 * compress() routine. See the definitions above. 455 */ 456 static int 457 zread(void *cookie, char *rbp, int num) 458 { 459 u_int count; 460 struct s_zstate *zs; 461 u_char *bp, header[3]; 462 463 if (num == 0) 464 return (0); 465 466 zs = cookie; 467 count = num; 468 bp = (u_char *)rbp; 469 switch (state) { 470 case S_START: 471 state = S_MIDDLE; 472 break; 473 case S_MIDDLE: 474 goto middle; 475 case S_EOF: 476 goto eof; 477 } 478 479 /* Check the magic number */ 480 if (fread(header, 481 sizeof(char), sizeof(header), fp) != sizeof(header) || 482 memcmp(header, magic_header, sizeof(magic_header)) != 0) { 483 errno = EFTYPE; 484 return (-1); 485 } 486 maxbits = header[2]; /* Set -b from file. */ 487 block_compress = maxbits & BLOCK_MASK; 488 maxbits &= BIT_MASK; 489 maxmaxcode = 1L << maxbits; 490 if (maxbits > BITS) { 491 errno = EFTYPE; 492 return (-1); 493 } 494 /* As above, initialize the first 256 entries in the table. */ 495 maxcode = MAXCODE(n_bits = INIT_BITS); 496 for (code = 255; code >= 0; code--) { 497 tab_prefixof(code) = 0; 498 tab_suffixof(code) = (char_type) code; 499 } 500 free_ent = block_compress ? FIRST : 256; 501 502 finchar = oldcode = getcode(zs); 503 if (oldcode == -1) /* EOF already? */ 504 return (0); /* Get out of here */ 505 506 /* First code must be 8 bits = char. */ 507 *bp++ = (u_char)finchar; 508 count--; 509 stackp = de_stack; 510 511 while ((code = getcode(zs)) > -1) { 512 513 if ((code == CLEAR) && block_compress) { 514 for (code = 255; code >= 0; code--) 515 tab_prefixof(code) = 0; 516 clear_flg = 1; 517 free_ent = FIRST - 1; 518 if ((code = getcode(zs)) == -1) /* O, untimely death! */ 519 break; 520 } 521 incode = code; 522 523 /* Special case for KwKwK string. */ 524 if (code >= free_ent) { 525 *stackp++ = finchar; 526 code = oldcode; 527 } 528 529 /* Generate output characters in reverse order. */ 530 while (code >= 256) { 531 *stackp++ = tab_suffixof(code); 532 code = tab_prefixof(code); 533 } 534 *stackp++ = finchar = tab_suffixof(code); 535 536 /* And put them out in forward order. */ 537 middle: do { 538 if (count-- == 0) 539 return (num); 540 *bp++ = *--stackp; 541 } while (stackp > de_stack); 542 543 /* Generate the new entry. */ 544 if ((code = free_ent) < maxmaxcode) { 545 tab_prefixof(code) = (u_short) oldcode; 546 tab_suffixof(code) = finchar; 547 free_ent = code + 1; 548 } 549 550 /* Remember previous code. */ 551 oldcode = incode; 552 } 553 state = S_EOF; 554 eof: return (num - count); 555 } 556 557 /*- 558 * Read one code from the standard input. If EOF, return -1. 559 * Inputs: 560 * stdin 561 * Outputs: 562 * code or -1 is returned. 563 */ 564 static code_int 565 getcode(struct s_zstate *zs) 566 { 567 code_int gcode; 568 int r_off, bits; 569 char_type *bp; 570 571 bp = gbuf; 572 if (clear_flg > 0 || roffset >= size || free_ent > maxcode) { 573 /* 574 * If the next entry will be too big for the current gcode 575 * size, then we must increase the size. This implies reading 576 * a new buffer full, too. 577 */ 578 if (free_ent > maxcode) { 579 n_bits++; 580 if (n_bits == maxbits) /* Won't get any bigger now. */ 581 maxcode = maxmaxcode; 582 else 583 maxcode = MAXCODE(n_bits); 584 } 585 if (clear_flg > 0) { 586 maxcode = MAXCODE(n_bits = INIT_BITS); 587 clear_flg = 0; 588 } 589 size = fread(gbuf, 1, n_bits, fp); 590 if (size <= 0) /* End of file. */ 591 return (-1); 592 roffset = 0; 593 /* Round size down to integral number of codes. */ 594 size = (size << 3) - (n_bits - 1); 595 } 596 r_off = roffset; 597 bits = n_bits; 598 599 /* Get to the first byte. */ 600 bp += (r_off >> 3); 601 r_off &= 7; 602 603 /* Get first part (low order bits). */ 604 gcode = (*bp++ >> r_off); 605 bits -= (8 - r_off); 606 r_off = 8 - r_off; /* Now, roffset into gcode word. */ 607 608 /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */ 609 if (bits >= 8) { 610 gcode |= *bp++ << r_off; 611 r_off += 8; 612 bits -= 8; 613 } 614 615 /* High order bits. */ 616 gcode |= (*bp & rmask[bits]) << r_off; 617 roffset += n_bits; 618 619 return (gcode); 620 } 621 622 static int 623 cl_block(struct s_zstate *zs) /* Table clear for block compress. */ 624 { 625 long rat; 626 627 checkpoint = in_count + CHECK_GAP; 628 629 if (in_count > 0x007fffff) { /* Shift will overflow. */ 630 rat = bytes_out >> 8; 631 if (rat == 0) /* Don't divide by zero. */ 632 rat = 0x7fffffff; 633 else 634 rat = in_count / rat; 635 } else 636 rat = (in_count << 8) / bytes_out; /* 8 fractional bits. */ 637 if (rat > ratio) 638 ratio = rat; 639 else { 640 ratio = 0; 641 cl_hash(zs, (count_int) hsize); 642 free_ent = FIRST; 643 clear_flg = 1; 644 if (output(zs, (code_int) CLEAR) == -1) 645 return (-1); 646 } 647 return (0); 648 } 649 650 static void 651 cl_hash(struct s_zstate *zs, count_int cl_hsize) /* Reset code table. */ 652 { 653 count_int *htab_p; 654 long i, m1; 655 656 m1 = -1; 657 htab_p = htab + cl_hsize; 658 i = cl_hsize - 16; 659 do { /* Might use Sys V memset(3) here. */ 660 *(htab_p - 16) = m1; 661 *(htab_p - 15) = m1; 662 *(htab_p - 14) = m1; 663 *(htab_p - 13) = m1; 664 *(htab_p - 12) = m1; 665 *(htab_p - 11) = m1; 666 *(htab_p - 10) = m1; 667 *(htab_p - 9) = m1; 668 *(htab_p - 8) = m1; 669 *(htab_p - 7) = m1; 670 *(htab_p - 6) = m1; 671 *(htab_p - 5) = m1; 672 *(htab_p - 4) = m1; 673 *(htab_p - 3) = m1; 674 *(htab_p - 2) = m1; 675 *(htab_p - 1) = m1; 676 htab_p -= 16; 677 } while ((i -= 16) >= 0); 678 for (i += 16; i > 0; i--) 679 *--htab_p = m1; 680 } 681 682 FILE * 683 zopen(const char *fname, const char *mode, int bits) 684 { 685 struct s_zstate *zs; 686 687 if ((mode[0] != 'r' && mode[0] != 'w') || mode[1] != '\0' || 688 bits < 0 || bits > BITS) { 689 errno = EINVAL; 690 return (NULL); 691 } 692 693 if ((zs = calloc(1, sizeof(struct s_zstate))) == NULL) 694 return (NULL); 695 696 maxbits = bits ? bits : BITS; /* User settable max # bits/code. */ 697 maxmaxcode = 1L << maxbits; /* Should NEVER generate this code. */ 698 hsize = HSIZE; /* For dynamic table sizing. */ 699 free_ent = 0; /* First unused entry. */ 700 block_compress = BLOCK_MASK; 701 clear_flg = 0; 702 ratio = 0; 703 checkpoint = CHECK_GAP; 704 in_count = 1; /* Length of input. */ 705 out_count = 0; /* # of codes output (for debugging). */ 706 state = S_START; 707 roffset = 0; 708 size = 0; 709 710 /* 711 * Layering compress on top of stdio in order to provide buffering, 712 * and ensure that reads and write work with the data specified. 713 */ 714 if ((fp = fopen(fname, mode)) == NULL) { 715 free(zs); 716 return (NULL); 717 } 718 switch (*mode) { 719 case 'r': 720 zmode = 'r'; 721 return (funopen(zs, zread, NULL, NULL, zclose)); 722 case 'w': 723 zmode = 'w'; 724 return (funopen(zs, NULL, zwrite, NULL, zclose)); 725 } 726 /* NOTREACHED */ 727 return (NULL); 728 } 729