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 38 #if defined(LIBC_SCCS) && !defined(lint) 39 static char sccsid[] = "@(#)zopen.c 8.1 (Berkeley) 6/27/93"; 40 #endif /* LIBC_SCCS and not lint */ 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 int zs_n_bits; /* Number of bits/code. */ 105 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 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 __P((struct s_zstate *)); 202 static void cl_hash __P((struct s_zstate *, count_int)); 203 static code_int getcode __P((struct s_zstate *)); 204 static int output __P((struct s_zstate *, code_int)); 205 static int zclose __P((void *)); 206 static int zread __P((void *, char *, int)); 207 static int zwrite __P((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(cookie, wbp, num) 237 void *cookie; 238 const char *wbp; 239 int num; 240 { 241 register code_int i; 242 register int c, disp; 243 struct s_zstate *zs; 244 const u_char *bp; 245 u_char tmp; 246 int count; 247 248 if (num == 0) 249 return (0); 250 251 zs = cookie; 252 count = num; 253 bp = (u_char *)wbp; 254 if (state == S_MIDDLE) 255 goto middle; 256 state = S_MIDDLE; 257 258 maxmaxcode = 1L << maxbits; 259 if (fwrite(magic_header, 260 sizeof(char), sizeof(magic_header), fp) != sizeof(magic_header)) 261 return (-1); 262 tmp = (u_char)((maxbits) | block_compress); 263 if (fwrite(&tmp, sizeof(char), sizeof(tmp), fp) != sizeof(tmp)) 264 return (-1); 265 266 offset = 0; 267 bytes_out = 3; /* Includes 3-byte header mojo. */ 268 out_count = 0; 269 clear_flg = 0; 270 ratio = 0; 271 in_count = 1; 272 checkpoint = CHECK_GAP; 273 maxcode = MAXCODE(n_bits = INIT_BITS); 274 free_ent = ((block_compress) ? FIRST : 256); 275 276 ent = *bp++; 277 --count; 278 279 hshift = 0; 280 for (fcode = (long)hsize; fcode < 65536L; fcode *= 2L) 281 hshift++; 282 hshift = 8 - hshift; /* Set hash code range bound. */ 283 284 hsize_reg = hsize; 285 cl_hash(zs, (count_int)hsize_reg); /* Clear hash table. */ 286 287 middle: for (i = 0; count--;) { 288 c = *bp++; 289 in_count++; 290 fcode = (long)(((long)c << maxbits) + ent); 291 i = ((c << hshift) ^ ent); /* Xor hashing. */ 292 293 if (htabof(i) == fcode) { 294 ent = codetabof(i); 295 continue; 296 } else if ((long)htabof(i) < 0) /* Empty slot. */ 297 goto nomatch; 298 disp = hsize_reg - i; /* Secondary hash (after G. Knott). */ 299 if (i == 0) 300 disp = 1; 301 probe: if ((i -= disp) < 0) 302 i += hsize_reg; 303 304 if (htabof(i) == fcode) { 305 ent = codetabof(i); 306 continue; 307 } 308 if ((long)htabof(i) >= 0) 309 goto probe; 310 nomatch: if (output(zs, (code_int) ent) == -1) 311 return (-1); 312 out_count++; 313 ent = c; 314 if (free_ent < maxmaxcode) { 315 codetabof(i) = free_ent++; /* code -> hashtable */ 316 htabof(i) = fcode; 317 } else if ((count_int)in_count >= 318 checkpoint && block_compress) { 319 if (cl_block(zs) == -1) 320 return (-1); 321 } 322 } 323 return (num); 324 } 325 326 static int 327 zclose(cookie) 328 void *cookie; 329 { 330 struct s_zstate *zs; 331 int rval; 332 333 zs = cookie; 334 if (zmode == 'w') { /* Put out the final code. */ 335 if (output(zs, (code_int) ent) == -1) { 336 (void)fclose(fp); 337 free(zs); 338 return (-1); 339 } 340 out_count++; 341 if (output(zs, (code_int) - 1) == -1) { 342 (void)fclose(fp); 343 free(zs); 344 return (-1); 345 } 346 } 347 rval = fclose(fp) == EOF ? -1 : 0; 348 free(zs); 349 return (rval); 350 } 351 352 /*- 353 * Output the given code. 354 * Inputs: 355 * code: A n_bits-bit integer. If == -1, then EOF. This assumes 356 * that n_bits =< (long)wordsize - 1. 357 * Outputs: 358 * Outputs code to the file. 359 * Assumptions: 360 * Chars are 8 bits long. 361 * Algorithm: 362 * Maintain a BITS character long buffer (so that 8 codes will 363 * fit in it exactly). Use the VAX insv instruction to insert each 364 * code in turn. When the buffer fills up empty it and start over. 365 */ 366 367 static char_type lmask[9] = 368 {0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80, 0x00}; 369 static char_type rmask[9] = 370 {0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff}; 371 372 static int 373 output(zs, ocode) 374 struct s_zstate *zs; 375 code_int ocode; 376 { 377 register int bits, r_off; 378 register 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(cookie, rbp, num) 463 void *cookie; 464 char *rbp; 465 int num; 466 { 467 register u_int count; 468 struct s_zstate *zs; 469 u_char *bp, header[3]; 470 471 if (num == 0) 472 return (0); 473 474 zs = cookie; 475 count = num; 476 bp = (u_char *)rbp; 477 switch (state) { 478 case S_START: 479 state = S_MIDDLE; 480 break; 481 case S_MIDDLE: 482 goto middle; 483 case S_EOF: 484 goto eof; 485 } 486 487 /* Check the magic number */ 488 if (fread(header, 489 sizeof(char), sizeof(header), fp) != sizeof(header) || 490 memcmp(header, magic_header, sizeof(magic_header)) != 0) { 491 errno = EFTYPE; 492 return (-1); 493 } 494 maxbits = header[2]; /* Set -b from file. */ 495 block_compress = maxbits & BLOCK_MASK; 496 maxbits &= BIT_MASK; 497 maxmaxcode = 1L << maxbits; 498 if (maxbits > BITS) { 499 errno = EFTYPE; 500 return (-1); 501 } 502 /* As above, initialize the first 256 entries in the table. */ 503 maxcode = MAXCODE(n_bits = INIT_BITS); 504 for (code = 255; code >= 0; code--) { 505 tab_prefixof(code) = 0; 506 tab_suffixof(code) = (char_type) code; 507 } 508 free_ent = block_compress ? FIRST : 256; 509 510 finchar = oldcode = getcode(zs); 511 if (oldcode == -1) /* EOF already? */ 512 return (0); /* Get out of here */ 513 514 /* First code must be 8 bits = char. */ 515 *bp++ = (u_char)finchar; 516 count--; 517 stackp = de_stack; 518 519 while ((code = getcode(zs)) > -1) { 520 521 if ((code == CLEAR) && block_compress) { 522 for (code = 255; code >= 0; code--) 523 tab_prefixof(code) = 0; 524 clear_flg = 1; 525 free_ent = FIRST - 1; 526 if ((code = getcode(zs)) == -1) /* O, untimely death! */ 527 break; 528 } 529 incode = code; 530 531 /* Special case for KwKwK string. */ 532 if (code >= free_ent) { 533 *stackp++ = finchar; 534 code = oldcode; 535 } 536 537 /* Generate output characters in reverse order. */ 538 while (code >= 256) { 539 *stackp++ = tab_suffixof(code); 540 code = tab_prefixof(code); 541 } 542 *stackp++ = finchar = tab_suffixof(code); 543 544 /* And put them out in forward order. */ 545 middle: do { 546 if (count-- == 0) 547 return (num); 548 *bp++ = *--stackp; 549 } while (stackp > de_stack); 550 551 /* Generate the new entry. */ 552 if ((code = free_ent) < maxmaxcode) { 553 tab_prefixof(code) = (u_short) oldcode; 554 tab_suffixof(code) = finchar; 555 free_ent = code + 1; 556 } 557 558 /* Remember previous code. */ 559 oldcode = incode; 560 } 561 state = S_EOF; 562 eof: return (num - count); 563 } 564 565 /*- 566 * Read one code from the standard input. If EOF, return -1. 567 * Inputs: 568 * stdin 569 * Outputs: 570 * code or -1 is returned. 571 */ 572 static code_int 573 getcode(zs) 574 struct s_zstate *zs; 575 { 576 register code_int gcode; 577 register int r_off, bits; 578 register char_type *bp; 579 580 bp = gbuf; 581 if (clear_flg > 0 || roffset >= size || free_ent > maxcode) { 582 /* 583 * If the next entry will be too big for the current gcode 584 * size, then we must increase the size. This implies reading 585 * a new buffer full, too. 586 */ 587 if (free_ent > maxcode) { 588 n_bits++; 589 if (n_bits == maxbits) /* Won't get any bigger now. */ 590 maxcode = maxmaxcode; 591 else 592 maxcode = MAXCODE(n_bits); 593 } 594 if (clear_flg > 0) { 595 maxcode = MAXCODE(n_bits = INIT_BITS); 596 clear_flg = 0; 597 } 598 size = fread(gbuf, 1, n_bits, fp); 599 if (size <= 0) /* End of file. */ 600 return (-1); 601 roffset = 0; 602 /* Round size down to integral number of codes. */ 603 size = (size << 3) - (n_bits - 1); 604 } 605 r_off = roffset; 606 bits = n_bits; 607 608 /* Get to the first byte. */ 609 bp += (r_off >> 3); 610 r_off &= 7; 611 612 /* Get first part (low order bits). */ 613 gcode = (*bp++ >> r_off); 614 bits -= (8 - r_off); 615 r_off = 8 - r_off; /* Now, roffset into gcode word. */ 616 617 /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */ 618 if (bits >= 8) { 619 gcode |= *bp++ << r_off; 620 r_off += 8; 621 bits -= 8; 622 } 623 624 /* High order bits. */ 625 gcode |= (*bp & rmask[bits]) << r_off; 626 roffset += n_bits; 627 628 return (gcode); 629 } 630 631 static int 632 cl_block(zs) /* Table clear for block compress. */ 633 struct s_zstate *zs; 634 { 635 register long rat; 636 637 checkpoint = in_count + CHECK_GAP; 638 639 if (in_count > 0x007fffff) { /* Shift will overflow. */ 640 rat = bytes_out >> 8; 641 if (rat == 0) /* Don't divide by zero. */ 642 rat = 0x7fffffff; 643 else 644 rat = in_count / rat; 645 } else 646 rat = (in_count << 8) / bytes_out; /* 8 fractional bits. */ 647 if (rat > ratio) 648 ratio = rat; 649 else { 650 ratio = 0; 651 cl_hash(zs, (count_int) hsize); 652 free_ent = FIRST; 653 clear_flg = 1; 654 if (output(zs, (code_int) CLEAR) == -1) 655 return (-1); 656 } 657 return (0); 658 } 659 660 static void 661 cl_hash(zs, cl_hsize) /* Reset code table. */ 662 struct s_zstate *zs; 663 register count_int cl_hsize; 664 { 665 register count_int *htab_p; 666 register long i, m1; 667 668 m1 = -1; 669 htab_p = htab + cl_hsize; 670 i = cl_hsize - 16; 671 do { /* Might use Sys V memset(3) here. */ 672 *(htab_p - 16) = m1; 673 *(htab_p - 15) = m1; 674 *(htab_p - 14) = m1; 675 *(htab_p - 13) = m1; 676 *(htab_p - 12) = m1; 677 *(htab_p - 11) = m1; 678 *(htab_p - 10) = m1; 679 *(htab_p - 9) = m1; 680 *(htab_p - 8) = m1; 681 *(htab_p - 7) = m1; 682 *(htab_p - 6) = m1; 683 *(htab_p - 5) = m1; 684 *(htab_p - 4) = m1; 685 *(htab_p - 3) = m1; 686 *(htab_p - 2) = m1; 687 *(htab_p - 1) = m1; 688 htab_p -= 16; 689 } while ((i -= 16) >= 0); 690 for (i += 16; i > 0; i--) 691 *--htab_p = m1; 692 } 693 694 FILE * 695 zopen(fname, mode, bits) 696 const char *fname, *mode; 697 int bits; 698 { 699 struct s_zstate *zs; 700 701 if ((mode[0] != 'r' && mode[0] != 'w') || mode[1] != '\0' || 702 bits < 0 || bits > BITS) { 703 errno = EINVAL; 704 return (NULL); 705 } 706 707 if ((zs = calloc(1, sizeof(struct s_zstate))) == NULL) 708 return (NULL); 709 710 maxbits = bits ? bits : BITS; /* User settable max # bits/code. */ 711 maxmaxcode = 1L << maxbits; /* Should NEVER generate this code. */ 712 hsize = HSIZE; /* For dynamic table sizing. */ 713 free_ent = 0; /* First unused entry. */ 714 block_compress = BLOCK_MASK; 715 clear_flg = 0; 716 ratio = 0; 717 checkpoint = CHECK_GAP; 718 in_count = 1; /* Length of input. */ 719 out_count = 0; /* # of codes output (for debugging). */ 720 state = S_START; 721 roffset = 0; 722 size = 0; 723 724 /* 725 * Layering compress on top of stdio in order to provide buffering, 726 * and ensure that reads and write work with the data specified. 727 */ 728 if ((fp = fopen(fname, mode)) == NULL) { 729 free(zs); 730 return (NULL); 731 } 732 switch (*mode) { 733 case 'r': 734 zmode = 'r'; 735 return (funopen(zs, zread, NULL, NULL, zclose)); 736 case 'w': 737 zmode = 'w'; 738 return (funopen(zs, NULL, zwrite, NULL, zclose)); 739 } 740 /* NOTREACHED */ 741 return (NULL); 742 } 743