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