1 /* $NetBSD: zopen.c,v 1.7 2002/05/26 22:25:38 wiz Exp $ */ 2 3 /*- 4 * Copyright (c) 1985, 1986, 1992, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Diomidis Spinellis and James A. Woods, derived from original 9 * work by Spencer Thomas and Joseph Orost. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by the University of 22 * California, Berkeley and its contributors. 23 * 4. Neither the name of the University nor the names of its contributors 24 * may be used to endorse or promote products derived from this software 25 * without specific prior written permission. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 28 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 29 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 30 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 31 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 32 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 33 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 34 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 35 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 36 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 37 * SUCH DAMAGE. 38 */ 39 40 #if defined(LIBC_SCCS) && !defined(lint) 41 #if 0 42 static char sccsid[] = "@(#)zopen.c 8.1 (Berkeley) 6/27/93"; 43 #else 44 static char rcsid[] = "$NetBSD: zopen.c,v 1.7 2002/05/26 22:25:38 wiz Exp $"; 45 #endif 46 #endif /* LIBC_SCCS and not lint */ 47 48 /*- 49 * fcompress.c - File compression ala IEEE Computer, June 1984. 50 * 51 * Compress authors: 52 * Spencer W. Thomas (decvax!utah-cs!thomas) 53 * Jim McKie (decvax!mcvax!jim) 54 * Steve Davies (decvax!vax135!petsd!peora!srd) 55 * Ken Turkowski (decvax!decwrl!turtlevax!ken) 56 * James A. Woods (decvax!ihnp4!ames!jaw) 57 * Joe Orost (decvax!vax135!petsd!joe) 58 * 59 * Cleaned up and converted to library returning I/O streams by 60 * Diomidis Spinellis <dds@doc.ic.ac.uk>. 61 * 62 * zopen(filename, mode, bits) 63 * Returns a FILE * that can be used for read or write. The modes 64 * supported are only "r" and "w". Seeking is not allowed. On 65 * reading the file is decompressed, on writing it is compressed. 66 * The output is compatible with compress(1) with 16 bit tables. 67 * Any file produced by compress(1) can be read. 68 */ 69 70 #include <sys/param.h> 71 #include <sys/stat.h> 72 73 #include <ctype.h> 74 #include <errno.h> 75 #include <signal.h> 76 #include <stdio.h> 77 #include <stdlib.h> 78 #include <string.h> 79 #include <unistd.h> 80 81 #define BITS 16 /* Default bits. */ 82 #define HSIZE 69001 /* 95% occupancy */ 83 84 /* A code_int must be able to hold 2**BITS values of type int, and also -1. */ 85 typedef long code_int; 86 typedef long count_int; 87 88 typedef u_char char_type; 89 static char_type magic_header[] = 90 {'\037', '\235'}; /* 1F 9D */ 91 92 #define BIT_MASK 0x1f /* Defines for third byte of header. */ 93 #define BLOCK_MASK 0x80 94 95 /* 96 * Masks 0x40 and 0x20 are free. I think 0x20 should mean that there is 97 * a fourth header byte (for expansion). 98 */ 99 #define INIT_BITS 9 /* Initial number of bits/code. */ 100 101 #define MAXCODE(n_bits) ((1 << (n_bits)) - 1) 102 103 struct s_zstate { 104 FILE *zs_fp; /* File stream for I/O */ 105 char zs_mode; /* r or w */ 106 enum { 107 S_START, S_MIDDLE, S_EOF 108 } zs_state; /* State of computation */ 109 int zs_n_bits; /* Number of bits/code. */ 110 int zs_maxbits; /* User settable max # bits/code. */ 111 code_int zs_maxcode; /* Maximum code, given n_bits. */ 112 code_int zs_maxmaxcode; /* Should NEVER generate this code. */ 113 count_int zs_htab [HSIZE]; 114 u_short zs_codetab [HSIZE]; 115 code_int zs_hsize; /* For dynamic table sizing. */ 116 code_int zs_free_ent; /* First unused entry. */ 117 /* 118 * Block compression parameters -- after all codes are used up, 119 * and compression rate changes, start over. 120 */ 121 int zs_block_compress; 122 int zs_clear_flg; 123 long zs_ratio; 124 count_int zs_checkpoint; 125 int zs_offset; 126 long zs_in_count; /* Length of input. */ 127 long zs_bytes_out; /* Length of compressed output. */ 128 long zs_out_count; /* # of codes output (for debugging). */ 129 char_type zs_buf[BITS]; 130 union { 131 struct { 132 long zs_fcode; 133 code_int zs_ent; 134 code_int zs_hsize_reg; 135 int zs_hshift; 136 } w; /* Write paramenters */ 137 struct { 138 char_type *zs_stackp; 139 int zs_finchar; 140 code_int zs_code, zs_oldcode, zs_incode; 141 int zs_roffset, zs_size; 142 char_type zs_gbuf[BITS]; 143 } r; /* Read parameters */ 144 } u; 145 }; 146 147 /* Definitions to retain old variable names */ 148 #define fp zs->zs_fp 149 #define zmode zs->zs_mode 150 #define state zs->zs_state 151 #define n_bits zs->zs_n_bits 152 #define maxbits zs->zs_maxbits 153 #define maxcode zs->zs_maxcode 154 #define maxmaxcode zs->zs_maxmaxcode 155 #define htab zs->zs_htab 156 #define codetab zs->zs_codetab 157 #define hsize zs->zs_hsize 158 #define free_ent zs->zs_free_ent 159 #define block_compress zs->zs_block_compress 160 #define clear_flg zs->zs_clear_flg 161 #define ratio zs->zs_ratio 162 #define checkpoint zs->zs_checkpoint 163 #define offset zs->zs_offset 164 #define in_count zs->zs_in_count 165 #define bytes_out zs->zs_bytes_out 166 #define out_count zs->zs_out_count 167 #define buf zs->zs_buf 168 #define fcode zs->u.w.zs_fcode 169 #define hsize_reg zs->u.w.zs_hsize_reg 170 #define ent zs->u.w.zs_ent 171 #define hshift zs->u.w.zs_hshift 172 #define stackp zs->u.r.zs_stackp 173 #define finchar zs->u.r.zs_finchar 174 #define code zs->u.r.zs_code 175 #define oldcode zs->u.r.zs_oldcode 176 #define incode zs->u.r.zs_incode 177 #define roffset zs->u.r.zs_roffset 178 #define size zs->u.r.zs_size 179 #define gbuf zs->u.r.zs_gbuf 180 181 /* 182 * To save much memory, we overlay the table used by compress() with those 183 * used by decompress(). The tab_prefix table is the same size and type as 184 * the codetab. The tab_suffix table needs 2**BITS characters. We get this 185 * from the beginning of htab. The output stack uses the rest of htab, and 186 * contains characters. There is plenty of room for any possible stack 187 * (stack used to be 8000 characters). 188 */ 189 190 #define htabof(i) htab[i] 191 #define codetabof(i) codetab[i] 192 193 #define tab_prefixof(i) codetabof(i) 194 #define tab_suffixof(i) ((char_type *)(htab))[i] 195 #define de_stack ((char_type *)&tab_suffixof(1 << BITS)) 196 197 #define CHECK_GAP 10000 /* Ratio check interval. */ 198 199 /* 200 * the next two codes should not be changed lightly, as they must not 201 * lie within the contiguous general code space. 202 */ 203 #define FIRST 257 /* First free entry. */ 204 #define CLEAR 256 /* Table clear output code. */ 205 206 static int cl_block(struct s_zstate *); 207 static void cl_hash(struct s_zstate *, count_int); 208 static code_int getcode(struct s_zstate *); 209 static int output(struct s_zstate *, code_int); 210 static int zclose(void *); 211 FILE *zopen(const char *, const char *, int); 212 static int zread(void *, char *, int); 213 static int zwrite(void *, const char *, int); 214 215 /*- 216 * Algorithm from "A Technique for High Performance Data Compression", 217 * Terry A. Welch, IEEE Computer Vol 17, No 6 (June 1984), pp 8-19. 218 * 219 * Algorithm: 220 * Modified Lempel-Ziv method (LZW). Basically finds common 221 * substrings and replaces them with a variable size code. This is 222 * deterministic, and can be done on the fly. Thus, the decompression 223 * procedure needs no input table, but tracks the way the table was built. 224 */ 225 226 /*- 227 * compress write 228 * 229 * Algorithm: use open addressing double hashing (no chaining) on the 230 * prefix code / next character combination. We do a variant of Knuth's 231 * algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime 232 * secondary probe. Here, the modular division first probe is gives way 233 * to a faster exclusive-or manipulation. Also do block compression with 234 * an adaptive reset, whereby the code table is cleared when the compression 235 * ratio decreases, but after the table fills. The variable-length output 236 * codes are re-sized at this point, and a special CLEAR code is generated 237 * for the decompressor. Late addition: construct the table according to 238 * file size for noticeable speed improvement on small files. Please direct 239 * questions about this implementation to ames!jaw. 240 */ 241 static int 242 zwrite(void *cookie, const char *wbp, int num) 243 { 244 code_int i; 245 int c, disp; 246 struct s_zstate *zs; 247 const u_char *bp; 248 u_char tmp; 249 int count; 250 251 if (num == 0) 252 return (0); 253 254 zs = cookie; 255 count = num; 256 bp = (u_char *)wbp; 257 if (state == S_MIDDLE) 258 goto middle; 259 state = S_MIDDLE; 260 261 maxmaxcode = 1L << maxbits; 262 if (fwrite(magic_header, 263 sizeof(char), sizeof(magic_header), fp) != sizeof(magic_header)) 264 return (-1); 265 tmp = (u_char)(maxbits | block_compress); 266 if (fwrite(&tmp, sizeof(char), sizeof(tmp), fp) != sizeof(tmp)) 267 return (-1); 268 269 offset = 0; 270 bytes_out = 3; /* Includes 3-byte header mojo. */ 271 out_count = 0; 272 clear_flg = 0; 273 ratio = 0; 274 in_count = 1; 275 checkpoint = CHECK_GAP; 276 maxcode = MAXCODE(n_bits = INIT_BITS); 277 free_ent = ((block_compress) ? FIRST : 256); 278 279 ent = *bp++; 280 --count; 281 282 hshift = 0; 283 for (fcode = (long)hsize; fcode < 65536L; fcode *= 2L) 284 hshift++; 285 hshift = 8 - hshift; /* Set hash code range bound. */ 286 287 hsize_reg = hsize; 288 cl_hash(zs, (count_int)hsize_reg); /* Clear hash table. */ 289 290 middle: for (i = 0; count--;) { 291 c = *bp++; 292 in_count++; 293 fcode = (long)(((long)c << maxbits) + ent); 294 i = ((c << hshift) ^ ent); /* Xor hashing. */ 295 296 if (htabof(i) == fcode) { 297 ent = codetabof(i); 298 continue; 299 } else if ((long)htabof(i) < 0) /* Empty slot. */ 300 goto nomatch; 301 disp = hsize_reg - i; /* Secondary hash (after G. Knott). */ 302 if (i == 0) 303 disp = 1; 304 probe: if ((i -= disp) < 0) 305 i += hsize_reg; 306 307 if (htabof(i) == fcode) { 308 ent = codetabof(i); 309 continue; 310 } 311 if ((long)htabof(i) >= 0) 312 goto probe; 313 nomatch: if (output(zs, (code_int) ent) == -1) 314 return (-1); 315 out_count++; 316 ent = c; 317 if (free_ent < maxmaxcode) { 318 codetabof(i) = free_ent++; /* code -> hashtable */ 319 htabof(i) = fcode; 320 } else if ((count_int)in_count >= 321 checkpoint && block_compress) { 322 if (cl_block(zs) == -1) 323 return (-1); 324 } 325 } 326 return (num); 327 } 328 329 static int 330 zclose(void *cookie) 331 { 332 struct s_zstate *zs; 333 int rval; 334 335 zs = cookie; 336 if (zmode == 'w') { /* Put out the final code. */ 337 if (output(zs, (code_int) ent) == -1) { 338 (void)fclose(fp); 339 free(zs); 340 return (-1); 341 } 342 out_count++; 343 if (output(zs, (code_int) - 1) == -1) { 344 (void)fclose(fp); 345 free(zs); 346 return (-1); 347 } 348 } 349 rval = fclose(fp) == EOF ? -1 : 0; 350 free(zs); 351 return (rval); 352 } 353 354 /*- 355 * Output the given code. 356 * Inputs: 357 * code: A n_bits-bit integer. If == -1, then EOF. This assumes 358 * that n_bits =< (long)wordsize - 1. 359 * Outputs: 360 * Outputs code to the file. 361 * Assumptions: 362 * Chars are 8 bits long. 363 * Algorithm: 364 * Maintain a BITS character long buffer (so that 8 codes will 365 * fit in it exactly). Use the VAX insv instruction to insert each 366 * code in turn. When the buffer fills up empty it and start over. 367 */ 368 369 static char_type lmask[9] = 370 {0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80, 0x00}; 371 static char_type rmask[9] = 372 {0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff}; 373 374 static int 375 output(struct s_zstate *zs, code_int ocode) 376 { 377 int bits, r_off; 378 char_type *bp; 379 380 r_off = offset; 381 bits = n_bits; 382 bp = buf; 383 if (ocode >= 0) { 384 /* Get to the first byte. */ 385 bp += (r_off >> 3); 386 r_off &= 7; 387 /* 388 * Since ocode is always >= 8 bits, only need to mask the first 389 * hunk on the left. 390 */ 391 *bp = (*bp & rmask[r_off]) | ((ocode << r_off) & lmask[r_off]); 392 bp++; 393 bits -= (8 - r_off); 394 ocode >>= 8 - r_off; 395 /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */ 396 if (bits >= 8) { 397 *bp++ = ocode; 398 ocode >>= 8; 399 bits -= 8; 400 } 401 /* Last bits. */ 402 if (bits) 403 *bp = ocode; 404 offset += n_bits; 405 if (offset == (n_bits << 3)) { 406 bp = buf; 407 bits = n_bits; 408 bytes_out += bits; 409 if (fwrite(bp, sizeof(char), bits, fp) != bits) 410 return (-1); 411 bp += bits; 412 bits = 0; 413 offset = 0; 414 } 415 /* 416 * If the next entry is going to be too big for the ocode size, 417 * then increase it, if possible. 418 */ 419 if (free_ent > maxcode || (clear_flg > 0)) { 420 /* 421 * Write the whole buffer, because the input side won't 422 * discover the size increase until after it has read it. 423 */ 424 if (offset > 0) { 425 if (fwrite(buf, 1, n_bits, fp) != n_bits) 426 return (-1); 427 bytes_out += n_bits; 428 } 429 offset = 0; 430 431 if (clear_flg) { 432 maxcode = MAXCODE(n_bits = INIT_BITS); 433 clear_flg = 0; 434 } else { 435 n_bits++; 436 if (n_bits == maxbits) 437 maxcode = maxmaxcode; 438 else 439 maxcode = MAXCODE(n_bits); 440 } 441 } 442 } else { 443 /* At EOF, write the rest of the buffer. */ 444 if (offset > 0) { 445 offset = (offset + 7) / 8; 446 if (fwrite(buf, 1, offset, fp) != offset) 447 return (-1); 448 bytes_out += offset; 449 } 450 offset = 0; 451 } 452 return (0); 453 } 454 455 /* 456 * Decompress read. This routine adapts to the codes in the file building 457 * the "string" table on-the-fly; requiring no table to be stored in the 458 * compressed file. The tables used herein are shared with those of the 459 * compress() routine. See the definitions above. 460 */ 461 static int 462 zread(void *cookie, char *rbp, int num) 463 { 464 u_int count; 465 struct s_zstate *zs; 466 u_char *bp, header[3]; 467 468 if (num == 0) 469 return (0); 470 471 zs = cookie; 472 count = num; 473 bp = (u_char *)rbp; 474 switch (state) { 475 case S_START: 476 state = S_MIDDLE; 477 break; 478 case S_MIDDLE: 479 goto middle; 480 case S_EOF: 481 goto eof; 482 } 483 484 /* Check the magic number */ 485 if (fread(header, 486 sizeof(char), sizeof(header), fp) != sizeof(header) || 487 memcmp(header, magic_header, sizeof(magic_header)) != 0) { 488 errno = EFTYPE; 489 return (-1); 490 } 491 maxbits = header[2]; /* Set -b from file. */ 492 block_compress = maxbits & BLOCK_MASK; 493 maxbits &= BIT_MASK; 494 maxmaxcode = 1L << maxbits; 495 if (maxbits > BITS) { 496 errno = EFTYPE; 497 return (-1); 498 } 499 /* As above, initialize the first 256 entries in the table. */ 500 maxcode = MAXCODE(n_bits = INIT_BITS); 501 for (code = 255; code >= 0; code--) { 502 tab_prefixof(code) = 0; 503 tab_suffixof(code) = (char_type) code; 504 } 505 free_ent = block_compress ? FIRST : 256; 506 507 finchar = oldcode = getcode(zs); 508 if (oldcode == -1) /* EOF already? */ 509 return (0); /* Get out of here */ 510 511 /* First code must be 8 bits = char. */ 512 *bp++ = (u_char)finchar; 513 count--; 514 stackp = de_stack; 515 516 while ((code = getcode(zs)) > -1) { 517 518 if ((code == CLEAR) && block_compress) { 519 for (code = 255; code >= 0; code--) 520 tab_prefixof(code) = 0; 521 clear_flg = 1; 522 free_ent = FIRST - 1; 523 if ((code = getcode(zs)) == -1) /* O, untimely death! */ 524 break; 525 } 526 incode = code; 527 528 /* Special case for KwKwK string. */ 529 if (code >= free_ent) { 530 *stackp++ = finchar; 531 code = oldcode; 532 } 533 534 /* Generate output characters in reverse order. */ 535 while (code >= 256) { 536 *stackp++ = tab_suffixof(code); 537 code = tab_prefixof(code); 538 } 539 *stackp++ = finchar = tab_suffixof(code); 540 541 /* And put them out in forward order. */ 542 middle: do { 543 if (count-- == 0) 544 return (num); 545 *bp++ = *--stackp; 546 } while (stackp > de_stack); 547 548 /* Generate the new entry. */ 549 if ((code = free_ent) < maxmaxcode) { 550 tab_prefixof(code) = (u_short) oldcode; 551 tab_suffixof(code) = finchar; 552 free_ent = code + 1; 553 } 554 555 /* Remember previous code. */ 556 oldcode = incode; 557 } 558 state = S_EOF; 559 eof: return (num - count); 560 } 561 562 /*- 563 * Read one code from the standard input. If EOF, return -1. 564 * Inputs: 565 * stdin 566 * Outputs: 567 * code or -1 is returned. 568 */ 569 static code_int 570 getcode(struct s_zstate *zs) 571 { 572 code_int gcode; 573 int r_off, bits; 574 char_type *bp; 575 576 bp = gbuf; 577 if (clear_flg > 0 || roffset >= size || free_ent > maxcode) { 578 /* 579 * If the next entry will be too big for the current gcode 580 * size, then we must increase the size. This implies reading 581 * a new buffer full, too. 582 */ 583 if (free_ent > maxcode) { 584 n_bits++; 585 if (n_bits == maxbits) /* Won't get any bigger now. */ 586 maxcode = maxmaxcode; 587 else 588 maxcode = MAXCODE(n_bits); 589 } 590 if (clear_flg > 0) { 591 maxcode = MAXCODE(n_bits = INIT_BITS); 592 clear_flg = 0; 593 } 594 size = fread(gbuf, 1, n_bits, fp); 595 if (size <= 0) /* End of file. */ 596 return (-1); 597 roffset = 0; 598 /* Round size down to integral number of codes. */ 599 size = (size << 3) - (n_bits - 1); 600 } 601 r_off = roffset; 602 bits = n_bits; 603 604 /* Get to the first byte. */ 605 bp += (r_off >> 3); 606 r_off &= 7; 607 608 /* Get first part (low order bits). */ 609 gcode = (*bp++ >> r_off); 610 bits -= (8 - r_off); 611 r_off = 8 - r_off; /* Now, roffset into gcode word. */ 612 613 /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */ 614 if (bits >= 8) { 615 gcode |= *bp++ << r_off; 616 r_off += 8; 617 bits -= 8; 618 } 619 620 /* High order bits. */ 621 gcode |= (*bp & rmask[bits]) << r_off; 622 roffset += n_bits; 623 624 return (gcode); 625 } 626 627 static int 628 cl_block(struct s_zstate *zs) /* Table clear for block compress. */ 629 { 630 long rat; 631 632 checkpoint = in_count + CHECK_GAP; 633 634 if (in_count > 0x007fffff) { /* Shift will overflow. */ 635 rat = bytes_out >> 8; 636 if (rat == 0) /* Don't divide by zero. */ 637 rat = 0x7fffffff; 638 else 639 rat = in_count / rat; 640 } else 641 rat = (in_count << 8) / bytes_out; /* 8 fractional bits. */ 642 if (rat > ratio) 643 ratio = rat; 644 else { 645 ratio = 0; 646 cl_hash(zs, (count_int) hsize); 647 free_ent = FIRST; 648 clear_flg = 1; 649 if (output(zs, (code_int) CLEAR) == -1) 650 return (-1); 651 } 652 return (0); 653 } 654 655 static void 656 cl_hash(struct s_zstate *zs, count_int cl_hsize) /* Reset code table. */ 657 { 658 count_int *htab_p; 659 long i, m1; 660 661 m1 = -1; 662 htab_p = htab + cl_hsize; 663 i = cl_hsize - 16; 664 do { /* Might use Sys V memset(3) here. */ 665 *(htab_p - 16) = m1; 666 *(htab_p - 15) = m1; 667 *(htab_p - 14) = m1; 668 *(htab_p - 13) = m1; 669 *(htab_p - 12) = m1; 670 *(htab_p - 11) = m1; 671 *(htab_p - 10) = m1; 672 *(htab_p - 9) = m1; 673 *(htab_p - 8) = m1; 674 *(htab_p - 7) = m1; 675 *(htab_p - 6) = m1; 676 *(htab_p - 5) = m1; 677 *(htab_p - 4) = m1; 678 *(htab_p - 3) = m1; 679 *(htab_p - 2) = m1; 680 *(htab_p - 1) = m1; 681 htab_p -= 16; 682 } while ((i -= 16) >= 0); 683 for (i += 16; i > 0; i--) 684 *--htab_p = m1; 685 } 686 687 FILE * 688 zopen(const char *fname, const char *mode, int bits) 689 { 690 struct s_zstate *zs; 691 692 if ((mode[0] != 'r' && mode[0] != 'w') || mode[1] != '\0' || 693 bits < 0 || bits > BITS) { 694 errno = EINVAL; 695 return (NULL); 696 } 697 698 if ((zs = calloc(1, sizeof(struct s_zstate))) == NULL) 699 return (NULL); 700 701 maxbits = bits ? bits : BITS; /* User settable max # bits/code. */ 702 maxmaxcode = 1 << maxbits; /* Should NEVER generate this code. */ 703 hsize = HSIZE; /* For dynamic table sizing. */ 704 free_ent = 0; /* First unused entry. */ 705 block_compress = BLOCK_MASK; 706 clear_flg = 0; 707 ratio = 0; 708 checkpoint = CHECK_GAP; 709 in_count = 1; /* Length of input. */ 710 out_count = 0; /* # of codes output (for debugging). */ 711 state = S_START; 712 roffset = 0; 713 size = 0; 714 715 /* 716 * Layering compress on top of stdio in order to provide buffering, 717 * and ensure that reads and write work with the data specified. 718 */ 719 if ((fp = fopen(fname, mode)) == NULL) { 720 free(zs); 721 return (NULL); 722 } 723 switch (*mode) { 724 case 'r': 725 zmode = 'r'; 726 return (funopen(zs, zread, NULL, NULL, zclose)); 727 case 'w': 728 zmode = 'w'; 729 return (funopen(zs, NULL, zwrite, NULL, zclose)); 730 } 731 /* NOTREACHED */ 732 return (NULL); 733 } 734