1 /* $NetBSD: zopen.c,v 1.6 1997/09/15 10:58:39 lukem 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 1.6 1997/09/15 10:58:39 lukem 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 __P((struct s_zstate *)); 207 static void cl_hash __P((struct s_zstate *, count_int)); 208 static code_int getcode __P((struct s_zstate *)); 209 static int output __P((struct s_zstate *, code_int)); 210 static int zclose __P((void *)); 211 FILE *zopen __P((const char *, const char *, int)); 212 static int zread __P((void *, char *, int)); 213 static int zwrite __P((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(cookie, wbp, num) 243 void *cookie; 244 const char *wbp; 245 int num; 246 { 247 code_int i; 248 int c, disp; 249 struct s_zstate *zs; 250 const u_char *bp; 251 u_char tmp; 252 int count; 253 254 if (num == 0) 255 return (0); 256 257 zs = cookie; 258 count = num; 259 bp = (u_char *)wbp; 260 if (state == S_MIDDLE) 261 goto middle; 262 state = S_MIDDLE; 263 264 maxmaxcode = 1L << maxbits; 265 if (fwrite(magic_header, 266 sizeof(char), sizeof(magic_header), fp) != sizeof(magic_header)) 267 return (-1); 268 tmp = (u_char)(maxbits | block_compress); 269 if (fwrite(&tmp, sizeof(char), sizeof(tmp), fp) != sizeof(tmp)) 270 return (-1); 271 272 offset = 0; 273 bytes_out = 3; /* Includes 3-byte header mojo. */ 274 out_count = 0; 275 clear_flg = 0; 276 ratio = 0; 277 in_count = 1; 278 checkpoint = CHECK_GAP; 279 maxcode = MAXCODE(n_bits = INIT_BITS); 280 free_ent = ((block_compress) ? FIRST : 256); 281 282 ent = *bp++; 283 --count; 284 285 hshift = 0; 286 for (fcode = (long)hsize; fcode < 65536L; fcode *= 2L) 287 hshift++; 288 hshift = 8 - hshift; /* Set hash code range bound. */ 289 290 hsize_reg = hsize; 291 cl_hash(zs, (count_int)hsize_reg); /* Clear hash table. */ 292 293 middle: for (i = 0; count--;) { 294 c = *bp++; 295 in_count++; 296 fcode = (long)(((long)c << maxbits) + ent); 297 i = ((c << hshift) ^ ent); /* Xor hashing. */ 298 299 if (htabof(i) == fcode) { 300 ent = codetabof(i); 301 continue; 302 } else if ((long)htabof(i) < 0) /* Empty slot. */ 303 goto nomatch; 304 disp = hsize_reg - i; /* Secondary hash (after G. Knott). */ 305 if (i == 0) 306 disp = 1; 307 probe: if ((i -= disp) < 0) 308 i += hsize_reg; 309 310 if (htabof(i) == fcode) { 311 ent = codetabof(i); 312 continue; 313 } 314 if ((long)htabof(i) >= 0) 315 goto probe; 316 nomatch: if (output(zs, (code_int) ent) == -1) 317 return (-1); 318 out_count++; 319 ent = c; 320 if (free_ent < maxmaxcode) { 321 codetabof(i) = free_ent++; /* code -> hashtable */ 322 htabof(i) = fcode; 323 } else if ((count_int)in_count >= 324 checkpoint && block_compress) { 325 if (cl_block(zs) == -1) 326 return (-1); 327 } 328 } 329 return (num); 330 } 331 332 static int 333 zclose(cookie) 334 void *cookie; 335 { 336 struct s_zstate *zs; 337 int rval; 338 339 zs = cookie; 340 if (zmode == 'w') { /* Put out the final code. */ 341 if (output(zs, (code_int) ent) == -1) { 342 (void)fclose(fp); 343 free(zs); 344 return (-1); 345 } 346 out_count++; 347 if (output(zs, (code_int) - 1) == -1) { 348 (void)fclose(fp); 349 free(zs); 350 return (-1); 351 } 352 } 353 rval = fclose(fp) == EOF ? -1 : 0; 354 free(zs); 355 return (rval); 356 } 357 358 /*- 359 * Output the given code. 360 * Inputs: 361 * code: A n_bits-bit integer. If == -1, then EOF. This assumes 362 * that n_bits =< (long)wordsize - 1. 363 * Outputs: 364 * Outputs code to the file. 365 * Assumptions: 366 * Chars are 8 bits long. 367 * Algorithm: 368 * Maintain a BITS character long buffer (so that 8 codes will 369 * fit in it exactly). Use the VAX insv instruction to insert each 370 * code in turn. When the buffer fills up empty it and start over. 371 */ 372 373 static char_type lmask[9] = 374 {0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80, 0x00}; 375 static char_type rmask[9] = 376 {0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff}; 377 378 static int 379 output(zs, ocode) 380 struct s_zstate *zs; 381 code_int ocode; 382 { 383 int bits, r_off; 384 char_type *bp; 385 386 r_off = offset; 387 bits = n_bits; 388 bp = buf; 389 if (ocode >= 0) { 390 /* Get to the first byte. */ 391 bp += (r_off >> 3); 392 r_off &= 7; 393 /* 394 * Since ocode is always >= 8 bits, only need to mask the first 395 * hunk on the left. 396 */ 397 *bp = (*bp & rmask[r_off]) | ((ocode << r_off) & lmask[r_off]); 398 bp++; 399 bits -= (8 - r_off); 400 ocode >>= 8 - r_off; 401 /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */ 402 if (bits >= 8) { 403 *bp++ = ocode; 404 ocode >>= 8; 405 bits -= 8; 406 } 407 /* Last bits. */ 408 if (bits) 409 *bp = ocode; 410 offset += n_bits; 411 if (offset == (n_bits << 3)) { 412 bp = buf; 413 bits = n_bits; 414 bytes_out += bits; 415 if (fwrite(bp, sizeof(char), bits, fp) != bits) 416 return (-1); 417 bp += bits; 418 bits = 0; 419 offset = 0; 420 } 421 /* 422 * If the next entry is going to be too big for the ocode size, 423 * then increase it, if possible. 424 */ 425 if (free_ent > maxcode || (clear_flg > 0)) { 426 /* 427 * Write the whole buffer, because the input side won't 428 * discover the size increase until after it has read it. 429 */ 430 if (offset > 0) { 431 if (fwrite(buf, 1, n_bits, fp) != n_bits) 432 return (-1); 433 bytes_out += n_bits; 434 } 435 offset = 0; 436 437 if (clear_flg) { 438 maxcode = MAXCODE(n_bits = INIT_BITS); 439 clear_flg = 0; 440 } else { 441 n_bits++; 442 if (n_bits == maxbits) 443 maxcode = maxmaxcode; 444 else 445 maxcode = MAXCODE(n_bits); 446 } 447 } 448 } else { 449 /* At EOF, write the rest of the buffer. */ 450 if (offset > 0) { 451 offset = (offset + 7) / 8; 452 if (fwrite(buf, 1, offset, fp) != offset) 453 return (-1); 454 bytes_out += offset; 455 } 456 offset = 0; 457 } 458 return (0); 459 } 460 461 /* 462 * Decompress read. This routine adapts to the codes in the file building 463 * the "string" table on-the-fly; requiring no table to be stored in the 464 * compressed file. The tables used herein are shared with those of the 465 * compress() routine. See the definitions above. 466 */ 467 static int 468 zread(cookie, rbp, num) 469 void *cookie; 470 char *rbp; 471 int num; 472 { 473 u_int count; 474 struct s_zstate *zs; 475 u_char *bp, header[3]; 476 477 if (num == 0) 478 return (0); 479 480 zs = cookie; 481 count = num; 482 bp = (u_char *)rbp; 483 switch (state) { 484 case S_START: 485 state = S_MIDDLE; 486 break; 487 case S_MIDDLE: 488 goto middle; 489 case S_EOF: 490 goto eof; 491 } 492 493 /* Check the magic number */ 494 if (fread(header, 495 sizeof(char), sizeof(header), fp) != sizeof(header) || 496 memcmp(header, magic_header, sizeof(magic_header)) != 0) { 497 errno = EFTYPE; 498 return (-1); 499 } 500 maxbits = header[2]; /* Set -b from file. */ 501 block_compress = maxbits & BLOCK_MASK; 502 maxbits &= BIT_MASK; 503 maxmaxcode = 1L << maxbits; 504 if (maxbits > BITS) { 505 errno = EFTYPE; 506 return (-1); 507 } 508 /* As above, initialize the first 256 entries in the table. */ 509 maxcode = MAXCODE(n_bits = INIT_BITS); 510 for (code = 255; code >= 0; code--) { 511 tab_prefixof(code) = 0; 512 tab_suffixof(code) = (char_type) code; 513 } 514 free_ent = block_compress ? FIRST : 256; 515 516 finchar = oldcode = getcode(zs); 517 if (oldcode == -1) /* EOF already? */ 518 return (0); /* Get out of here */ 519 520 /* First code must be 8 bits = char. */ 521 *bp++ = (u_char)finchar; 522 count--; 523 stackp = de_stack; 524 525 while ((code = getcode(zs)) > -1) { 526 527 if ((code == CLEAR) && block_compress) { 528 for (code = 255; code >= 0; code--) 529 tab_prefixof(code) = 0; 530 clear_flg = 1; 531 free_ent = FIRST - 1; 532 if ((code = getcode(zs)) == -1) /* O, untimely death! */ 533 break; 534 } 535 incode = code; 536 537 /* Special case for KwKwK string. */ 538 if (code >= free_ent) { 539 *stackp++ = finchar; 540 code = oldcode; 541 } 542 543 /* Generate output characters in reverse order. */ 544 while (code >= 256) { 545 *stackp++ = tab_suffixof(code); 546 code = tab_prefixof(code); 547 } 548 *stackp++ = finchar = tab_suffixof(code); 549 550 /* And put them out in forward order. */ 551 middle: do { 552 if (count-- == 0) 553 return (num); 554 *bp++ = *--stackp; 555 } while (stackp > de_stack); 556 557 /* Generate the new entry. */ 558 if ((code = free_ent) < maxmaxcode) { 559 tab_prefixof(code) = (u_short) oldcode; 560 tab_suffixof(code) = finchar; 561 free_ent = code + 1; 562 } 563 564 /* Remember previous code. */ 565 oldcode = incode; 566 } 567 state = S_EOF; 568 eof: return (num - count); 569 } 570 571 /*- 572 * Read one code from the standard input. If EOF, return -1. 573 * Inputs: 574 * stdin 575 * Outputs: 576 * code or -1 is returned. 577 */ 578 static code_int 579 getcode(zs) 580 struct s_zstate *zs; 581 { 582 code_int gcode; 583 int r_off, bits; 584 char_type *bp; 585 586 bp = gbuf; 587 if (clear_flg > 0 || roffset >= size || free_ent > maxcode) { 588 /* 589 * If the next entry will be too big for the current gcode 590 * size, then we must increase the size. This implies reading 591 * a new buffer full, too. 592 */ 593 if (free_ent > maxcode) { 594 n_bits++; 595 if (n_bits == maxbits) /* Won't get any bigger now. */ 596 maxcode = maxmaxcode; 597 else 598 maxcode = MAXCODE(n_bits); 599 } 600 if (clear_flg > 0) { 601 maxcode = MAXCODE(n_bits = INIT_BITS); 602 clear_flg = 0; 603 } 604 size = fread(gbuf, 1, n_bits, fp); 605 if (size <= 0) /* End of file. */ 606 return (-1); 607 roffset = 0; 608 /* Round size down to integral number of codes. */ 609 size = (size << 3) - (n_bits - 1); 610 } 611 r_off = roffset; 612 bits = n_bits; 613 614 /* Get to the first byte. */ 615 bp += (r_off >> 3); 616 r_off &= 7; 617 618 /* Get first part (low order bits). */ 619 gcode = (*bp++ >> r_off); 620 bits -= (8 - r_off); 621 r_off = 8 - r_off; /* Now, roffset into gcode word. */ 622 623 /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */ 624 if (bits >= 8) { 625 gcode |= *bp++ << r_off; 626 r_off += 8; 627 bits -= 8; 628 } 629 630 /* High order bits. */ 631 gcode |= (*bp & rmask[bits]) << r_off; 632 roffset += n_bits; 633 634 return (gcode); 635 } 636 637 static int 638 cl_block(zs) /* Table clear for block compress. */ 639 struct s_zstate *zs; 640 { 641 long rat; 642 643 checkpoint = in_count + CHECK_GAP; 644 645 if (in_count > 0x007fffff) { /* Shift will overflow. */ 646 rat = bytes_out >> 8; 647 if (rat == 0) /* Don't divide by zero. */ 648 rat = 0x7fffffff; 649 else 650 rat = in_count / rat; 651 } else 652 rat = (in_count << 8) / bytes_out; /* 8 fractional bits. */ 653 if (rat > ratio) 654 ratio = rat; 655 else { 656 ratio = 0; 657 cl_hash(zs, (count_int) hsize); 658 free_ent = FIRST; 659 clear_flg = 1; 660 if (output(zs, (code_int) CLEAR) == -1) 661 return (-1); 662 } 663 return (0); 664 } 665 666 static void 667 cl_hash(zs, cl_hsize) /* Reset code table. */ 668 struct s_zstate *zs; 669 count_int cl_hsize; 670 { 671 count_int *htab_p; 672 long i, m1; 673 674 m1 = -1; 675 htab_p = htab + cl_hsize; 676 i = cl_hsize - 16; 677 do { /* Might use Sys V memset(3) here. */ 678 *(htab_p - 16) = m1; 679 *(htab_p - 15) = m1; 680 *(htab_p - 14) = m1; 681 *(htab_p - 13) = m1; 682 *(htab_p - 12) = m1; 683 *(htab_p - 11) = m1; 684 *(htab_p - 10) = m1; 685 *(htab_p - 9) = m1; 686 *(htab_p - 8) = m1; 687 *(htab_p - 7) = m1; 688 *(htab_p - 6) = m1; 689 *(htab_p - 5) = m1; 690 *(htab_p - 4) = m1; 691 *(htab_p - 3) = m1; 692 *(htab_p - 2) = m1; 693 *(htab_p - 1) = m1; 694 htab_p -= 16; 695 } while ((i -= 16) >= 0); 696 for (i += 16; i > 0; i--) 697 *--htab_p = m1; 698 } 699 700 FILE * 701 zopen(fname, mode, bits) 702 const char *fname, *mode; 703 int bits; 704 { 705 struct s_zstate *zs; 706 707 if ((mode[0] != 'r' && mode[0] != 'w') || mode[1] != '\0' || 708 bits < 0 || bits > BITS) { 709 errno = EINVAL; 710 return (NULL); 711 } 712 713 if ((zs = calloc(1, sizeof(struct s_zstate))) == NULL) 714 return (NULL); 715 716 maxbits = bits ? bits : BITS; /* User settable max # bits/code. */ 717 maxmaxcode = 1 << maxbits; /* Should NEVER generate this code. */ 718 hsize = HSIZE; /* For dynamic table sizing. */ 719 free_ent = 0; /* First unused entry. */ 720 block_compress = BLOCK_MASK; 721 clear_flg = 0; 722 ratio = 0; 723 checkpoint = CHECK_GAP; 724 in_count = 1; /* Length of input. */ 725 out_count = 0; /* # of codes output (for debugging). */ 726 state = S_START; 727 roffset = 0; 728 size = 0; 729 730 /* 731 * Layering compress on top of stdio in order to provide buffering, 732 * and ensure that reads and write work with the data specified. 733 */ 734 if ((fp = fopen(fname, mode)) == NULL) { 735 free(zs); 736 return (NULL); 737 } 738 switch (*mode) { 739 case 'r': 740 zmode = 'r'; 741 return (funopen(zs, zread, NULL, NULL, zclose)); 742 case 'w': 743 zmode = 'w'; 744 return (funopen(zs, NULL, zwrite, NULL, zclose)); 745 } 746 /* NOTREACHED */ 747 return (NULL); 748 } 749