1/*- 2 * SPDX-License-Identifier: BSD-3-Clause 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. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36 37#include <sys/cdefs.h> 38/*- 39 * fcompress.c - File compression ala IEEE Computer, June 1984. 40 * 41 * Compress authors: 42 * Spencer W. Thomas (decvax!utah-cs!thomas) 43 * Jim McKie (decvax!mcvax!jim) 44 * Steve Davies (decvax!vax135!petsd!peora!srd) 45 * Ken Turkowski (decvax!decwrl!turtlevax!ken) 46 * James A. Woods (decvax!ihnp4!ames!jaw) 47 * Joe Orost (decvax!vax135!petsd!joe) 48 * 49 * Cleaned up and converted to library returning I/O streams by 50 * Diomidis Spinellis <dds@doc.ic.ac.uk>. 51 * 52 * zopen(filename, mode, bits) 53 * Returns a FILE * that can be used for read or write. The modes 54 * supported are only "r" and "w". Seeking is not allowed. On 55 * reading the file is decompressed, on writing it is compressed. 56 * The output is compatible with compress(1) with 16 bit tables. 57 * Any file produced by compress(1) can be read. 58 */ 59 60#include <sys/param.h> 61#include <sys/stat.h> 62 63#include <ctype.h> 64#include <errno.h> 65#include <signal.h> 66#include <stdio.h> 67#include <stdlib.h> 68#include <string.h> 69#include <unistd.h> 70#include "zopen.h" 71 72#define BITS 16 /* Default bits. */ 73#define HSIZE 69001 /* 95% occupancy */ 74 75/* A code_int must be able to hold 2**BITS values of type int, and also -1. */ 76typedef long code_int; 77typedef long count_int; 78 79typedef u_char char_type; 80static char_type magic_header[] = 81 {'\037', '\235'}; /* 1F 9D */ 82 83#define BIT_MASK 0x1f /* Defines for third byte of header. */ 84#define BLOCK_MASK 0x80 85 86/* 87 * Masks 0x40 and 0x20 are free. I think 0x20 should mean that there is 88 * a fourth header byte (for expansion). 89 */ 90#define INIT_BITS 9 /* Initial number of bits/code. */ 91 92#define MAXCODE(n_bits) ((1 << (n_bits)) - 1) 93 94struct s_zstate { 95 FILE *zs_fp; /* File stream for I/O */ 96 char zs_mode; /* r or w */ 97 enum { 98 S_START, S_MIDDLE, S_EOF 99 } zs_state; /* State of computation */ 100 u_int zs_n_bits; /* Number of bits/code. */ 101 u_int zs_maxbits; /* User settable max # bits/code. */ 102 code_int zs_maxcode; /* Maximum code, given n_bits. */ 103 code_int zs_maxmaxcode; /* Should NEVER generate this code. */ 104 count_int zs_htab [HSIZE]; 105 u_short zs_codetab [HSIZE]; 106 code_int zs_hsize; /* For dynamic table sizing. */ 107 code_int zs_free_ent; /* First unused entry. */ 108 /* 109 * Block compression parameters -- after all codes are used up, 110 * and compression rate changes, start over. 111 */ 112 int zs_block_compress; 113 int zs_clear_flg; 114 long zs_ratio; 115 count_int zs_checkpoint; 116 u_int zs_offset; 117 long zs_in_count; /* Length of input. */ 118 long zs_bytes_out; /* Length of compressed output. */ 119 long zs_out_count; /* # of codes output (for debugging). */ 120 char_type zs_buf[BITS]; 121 union { 122 struct { 123 long zs_fcode; 124 code_int zs_ent; 125 code_int zs_hsize_reg; 126 int zs_hshift; 127 } w; /* Write parameters */ 128 struct { 129 char_type *zs_stackp; 130 int zs_finchar; 131 code_int zs_code, zs_oldcode, zs_incode; 132 int zs_roffset, zs_size; 133 char_type zs_gbuf[BITS]; 134 } r; /* Read parameters */ 135 } u; 136}; 137 138/* Definitions to retain old variable names */ 139#define fp zs->zs_fp 140#define zmode zs->zs_mode 141#define state zs->zs_state 142#define n_bits zs->zs_n_bits 143#define maxbits zs->zs_maxbits 144#define maxcode zs->zs_maxcode 145#define maxmaxcode zs->zs_maxmaxcode 146#define htab zs->zs_htab 147#define codetab zs->zs_codetab 148#define hsize zs->zs_hsize 149#define free_ent zs->zs_free_ent 150#define block_compress zs->zs_block_compress 151#define clear_flg zs->zs_clear_flg 152#define ratio zs->zs_ratio 153#define checkpoint zs->zs_checkpoint 154#define offset zs->zs_offset 155#define in_count zs->zs_in_count 156#define bytes_out zs->zs_bytes_out 157#define out_count zs->zs_out_count 158#define buf zs->zs_buf 159#define fcode zs->u.w.zs_fcode 160#define hsize_reg zs->u.w.zs_hsize_reg 161#define ent zs->u.w.zs_ent 162#define hshift zs->u.w.zs_hshift 163#define stackp zs->u.r.zs_stackp 164#define finchar zs->u.r.zs_finchar 165#define code zs->u.r.zs_code 166#define oldcode zs->u.r.zs_oldcode 167#define incode zs->u.r.zs_incode 168#define roffset zs->u.r.zs_roffset 169#define size zs->u.r.zs_size 170#define gbuf zs->u.r.zs_gbuf 171 172/* 173 * To save much memory, we overlay the table used by compress() with those 174 * used by decompress(). The tab_prefix table is the same size and type as 175 * the codetab. The tab_suffix table needs 2**BITS characters. We get this 176 * from the beginning of htab. The output stack uses the rest of htab, and 177 * contains characters. There is plenty of room for any possible stack 178 * (stack used to be 8000 characters). 179 */ 180 181#define htabof(i) htab[i] 182#define codetabof(i) codetab[i] 183 184#define tab_prefixof(i) codetabof(i) 185#define tab_suffixof(i) ((char_type *)(htab))[i] 186#define de_stack ((char_type *)&tab_suffixof(1 << BITS)) 187 188#define CHECK_GAP 10000 /* Ratio check interval. */ 189 190/* 191 * the next two codes should not be changed lightly, as they must not 192 * lie within the contiguous general code space. 193 */ 194#define FIRST 257 /* First free entry. */ 195#define CLEAR 256 /* Table clear output code. */ 196 197static int cl_block(struct s_zstate *); 198static void cl_hash(struct s_zstate *, count_int); 199static code_int getcode(struct s_zstate *); 200static int output(struct s_zstate *, code_int); 201static int zclose(void *); 202static int zread(void *, char *, int); 203static int zwrite(void *, const char *, int); 204 205/*- 206 * Algorithm from "A Technique for High Performance Data Compression", 207 * Terry A. Welch, IEEE Computer Vol 17, No 6 (June 1984), pp 8-19. 208 * 209 * Algorithm: 210 * Modified Lempel-Ziv method (LZW). Basically finds common 211 * substrings and replaces them with a variable size code. This is 212 * deterministic, and can be done on the fly. Thus, the decompression 213 * procedure needs no input table, but tracks the way the table was built. 214 */ 215 216/*- 217 * compress write 218 * 219 * Algorithm: use open addressing double hashing (no chaining) on the 220 * prefix code / next character combination. We do a variant of Knuth's 221 * algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime 222 * secondary probe. Here, the modular division first probe is gives way 223 * to a faster exclusive-or manipulation. Also do block compression with 224 * an adaptive reset, whereby the code table is cleared when the compression 225 * ratio decreases, but after the table fills. The variable-length output 226 * codes are re-sized at this point, and a special CLEAR code is generated 227 * for the decompressor. Late addition: construct the table according to 228 * file size for noticeable speed improvement on small files. Please direct 229 * questions about this implementation to ames!jaw. 230 */ 231static int 232zwrite(void *cookie, const char *wbp, int num) 233{ 234 code_int i; 235 int c, disp; 236 struct s_zstate *zs; 237 const u_char *bp; 238 u_char tmp; 239 int count; 240 241 if (num == 0) 242 return (0); 243 244 zs = cookie; 245 count = num; 246 bp = (const u_char *)wbp; 247 if (state == S_MIDDLE) 248 goto middle; 249 state = S_MIDDLE; 250 251 maxmaxcode = 1L << maxbits; 252 if (fwrite(magic_header, 253 sizeof(char), sizeof(magic_header), fp) != sizeof(magic_header)) 254 return (-1); 255 tmp = (u_char)((maxbits) | block_compress); 256 if (fwrite(&tmp, sizeof(char), sizeof(tmp), fp) != sizeof(tmp)) 257 return (-1); 258 259 offset = 0; 260 bytes_out = 3; /* Includes 3-byte header mojo. */ 261 out_count = 0; 262 clear_flg = 0; 263 ratio = 0; 264 in_count = 1; 265 checkpoint = CHECK_GAP; 266 maxcode = MAXCODE(n_bits = INIT_BITS); 267 free_ent = ((block_compress) ? FIRST : 256); 268 269 ent = *bp++; 270 --count; 271 272 hshift = 0; 273 for (fcode = (long)hsize; fcode < 65536L; fcode *= 2L) 274 hshift++; 275 hshift = 8 - hshift; /* Set hash code range bound. */ 276 277 hsize_reg = hsize; 278 cl_hash(zs, (count_int)hsize_reg); /* Clear hash table. */ 279 280middle: for (i = 0; count--;) { 281 c = *bp++; 282 in_count++; 283 fcode = (long)(((long)c << maxbits) + ent); 284 i = ((c << hshift) ^ ent); /* Xor hashing. */ 285 286 if (htabof(i) == fcode) { 287 ent = codetabof(i); 288 continue; 289 } else if ((long)htabof(i) < 0) /* Empty slot. */ 290 goto nomatch; 291 disp = hsize_reg - i; /* Secondary hash (after G. Knott). */ 292 if (i == 0) 293 disp = 1; 294probe: if ((i -= disp) < 0) 295 i += hsize_reg; 296 297 if (htabof(i) == fcode) { 298 ent = codetabof(i); 299 continue; 300 } 301 if ((long)htabof(i) >= 0) 302 goto probe; 303nomatch: if (output(zs, (code_int) ent) == -1) 304 return (-1); 305 out_count++; 306 ent = c; 307 if (free_ent < maxmaxcode) { 308 codetabof(i) = free_ent++; /* code -> hashtable */ 309 htabof(i) = fcode; 310 } else if ((count_int)in_count >= 311 checkpoint && block_compress) { 312 if (cl_block(zs) == -1) 313 return (-1); 314 } 315 } 316 return (num); 317} 318 319static int 320zclose(void *cookie) 321{ 322 struct s_zstate *zs; 323 int rval; 324 325 zs = cookie; 326 if (zmode == 'w') { /* Put out the final code. */ 327 if (output(zs, (code_int) ent) == -1) { 328 (void)fclose(fp); 329 free(zs); 330 return (-1); 331 } 332 out_count++; 333 if (output(zs, (code_int) - 1) == -1) { 334 (void)fclose(fp); 335 free(zs); 336 return (-1); 337 } 338 } 339 rval = fclose(fp) == EOF ? -1 : 0; 340 free(zs); 341 return (rval); 342} 343 344/*- 345 * Output the given code. 346 * Inputs: 347 * code: A n_bits-bit integer. If == -1, then EOF. This assumes 348 * that n_bits =< (long)wordsize - 1. 349 * Outputs: 350 * Outputs code to the file. 351 * Assumptions: 352 * Chars are 8 bits long. 353 * Algorithm: 354 * Maintain a BITS character long buffer (so that 8 codes will 355 * fit in it exactly). Use the VAX insv instruction to insert each 356 * code in turn. When the buffer fills up empty it and start over. 357 */ 358 359static char_type lmask[9] = 360 {0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80, 0x00}; 361static char_type rmask[9] = 362 {0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff}; 363 364static int 365output(struct s_zstate *zs, code_int ocode) 366{ 367 int r_off; 368 u_int bits; 369 char_type *bp; 370 371 r_off = offset; 372 bits = n_bits; 373 bp = buf; 374 if (ocode >= 0) { 375 /* Get to the first byte. */ 376 bp += (r_off >> 3); 377 r_off &= 7; 378 /* 379 * Since ocode is always >= 8 bits, only need to mask the first 380 * hunk on the left. 381 */ 382 *bp = (*bp & rmask[r_off]) | ((ocode << r_off) & lmask[r_off]); 383 bp++; 384 bits -= (8 - r_off); 385 ocode >>= 8 - r_off; 386 /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */ 387 if (bits >= 8) { 388 *bp++ = ocode; 389 ocode >>= 8; 390 bits -= 8; 391 } 392 /* Last bits. */ 393 if (bits) 394 *bp = ocode; 395 offset += n_bits; 396 if (offset == (n_bits << 3)) { 397 bp = buf; 398 bits = n_bits; 399 bytes_out += bits; 400 if (fwrite(bp, sizeof(char), bits, fp) != bits) 401 return (-1); 402 bp += bits; 403 bits = 0; 404 offset = 0; 405 } 406 /* 407 * If the next entry is going to be too big for the ocode size, 408 * then increase it, if possible. 409 */ 410 if (free_ent > maxcode || (clear_flg > 0)) { 411 /* 412 * Write the whole buffer, because the input side won't 413 * discover the size increase until after it has read it. 414 */ 415 if (offset > 0) { 416 if (fwrite(buf, 1, n_bits, fp) != n_bits) 417 return (-1); 418 bytes_out += n_bits; 419 } 420 offset = 0; 421 422 if (clear_flg) { 423 maxcode = MAXCODE(n_bits = INIT_BITS); 424 clear_flg = 0; 425 } else { 426 n_bits++; 427 if (n_bits == maxbits) 428 maxcode = maxmaxcode; 429 else 430 maxcode = MAXCODE(n_bits); 431 } 432 } 433 } else { 434 /* At EOF, write the rest of the buffer. */ 435 if (offset > 0) { 436 offset = (offset + 7) / 8; 437 if (fwrite(buf, 1, offset, fp) != offset) 438 return (-1); 439 bytes_out += offset; 440 } 441 offset = 0; 442 } 443 return (0); 444} 445 446/* 447 * Decompress read. This routine adapts to the codes in the file building 448 * the "string" table on-the-fly; requiring no table to be stored in the 449 * compressed file. The tables used herein are shared with those of the 450 * compress() routine. See the definitions above. 451 */ 452static int 453zread(void *cookie, char *rbp, int num) 454{ 455 u_int count; 456 struct s_zstate *zs; 457 u_char *bp, header[3]; 458 459 if (num == 0) 460 return (0); 461 462 zs = cookie; 463 count = num; 464 bp = (u_char *)rbp; 465 switch (state) { 466 case S_START: 467 state = S_MIDDLE; 468 break; 469 case S_MIDDLE: 470 goto middle; 471 case S_EOF: 472 goto eof; 473 } 474 475 /* Check the magic number */ 476 if (fread(header, 477 sizeof(char), sizeof(header), fp) != sizeof(header) || 478 memcmp(header, magic_header, sizeof(magic_header)) != 0) { 479 errno = EFTYPE; 480 return (-1); 481 } 482 maxbits = header[2]; /* Set -b from file. */ 483 block_compress = maxbits & BLOCK_MASK; 484 maxbits &= BIT_MASK; 485 maxmaxcode = 1L << maxbits; 486 if (maxbits > BITS || maxbits < 12) { 487 errno = EFTYPE; 488 return (-1); 489 } 490 /* As above, initialize the first 256 entries in the table. */ 491 maxcode = MAXCODE(n_bits = INIT_BITS); 492 for (code = 255; code >= 0; code--) { 493 tab_prefixof(code) = 0; 494 tab_suffixof(code) = (char_type) code; 495 } 496 free_ent = block_compress ? FIRST : 256; 497 498 finchar = oldcode = getcode(zs); 499 if (oldcode == -1) /* EOF already? */ 500 return (0); /* Get out of here */ 501 502 /* First code must be 8 bits = char. */ 503 *bp++ = (u_char)finchar; 504 count--; 505 stackp = de_stack; 506 507 while ((code = getcode(zs)) > -1) { 508 509 if ((code == CLEAR) && block_compress) { 510 for (code = 255; code >= 0; code--) 511 tab_prefixof(code) = 0; 512 clear_flg = 1; 513 free_ent = FIRST; 514 oldcode = -1; 515 continue; 516 } 517 incode = code; 518 519 /* Special case for kWkWk string. */ 520 if (code >= free_ent) { 521 if (code > free_ent || oldcode == -1) { 522 /* Bad stream. */ 523 errno = EINVAL; 524 return (-1); 525 } 526 *stackp++ = finchar; 527 code = oldcode; 528 } 529 /* 530 * The above condition ensures that code < free_ent. 531 * The construction of tab_prefixof in turn guarantees that 532 * each iteration decreases code and therefore stack usage is 533 * bound by 1 << BITS - 256. 534 */ 535 536 /* Generate output characters in reverse order. */ 537 while (code >= 256) { 538 *stackp++ = tab_suffixof(code); 539 code = tab_prefixof(code); 540 } 541 *stackp++ = finchar = tab_suffixof(code); 542 543 /* And put them out in forward order. */ 544middle: do { 545 if (count-- == 0) 546 return (num); 547 *bp++ = *--stackp; 548 } while (stackp > de_stack); 549 550 /* Generate the new entry. */ 551 if ((code = free_ent) < maxmaxcode && oldcode != -1) { 552 tab_prefixof(code) = (u_short) oldcode; 553 tab_suffixof(code) = finchar; 554 free_ent = code + 1; 555 } 556 557 /* Remember previous code. */ 558 oldcode = incode; 559 } 560 state = S_EOF; 561eof: return (num - count); 562} 563 564/*- 565 * Read one code from the standard input. If EOF, return -1. 566 * Inputs: 567 * stdin 568 * Outputs: 569 * code or -1 is returned. 570 */ 571static code_int 572getcode(struct s_zstate *zs) 573{ 574 code_int gcode; 575 int r_off, bits; 576 char_type *bp; 577 578 bp = gbuf; 579 if (clear_flg > 0 || roffset >= size || free_ent > maxcode) { 580 /* 581 * If the next entry will be too big for the current gcode 582 * size, then we must increase the size. This implies reading 583 * a new buffer full, too. 584 */ 585 if (free_ent > maxcode) { 586 n_bits++; 587 if (n_bits == maxbits) /* Won't get any bigger now. */ 588 maxcode = maxmaxcode; 589 else 590 maxcode = MAXCODE(n_bits); 591 } 592 if (clear_flg > 0) { 593 maxcode = MAXCODE(n_bits = INIT_BITS); 594 clear_flg = 0; 595 } 596 size = fread(gbuf, 1, n_bits, fp); 597 if (size <= 0) /* End of file. */ 598 return (-1); 599 roffset = 0; 600 /* Round size down to integral number of codes. */ 601 size = (size << 3) - (n_bits - 1); 602 } 603 r_off = roffset; 604 bits = n_bits; 605 606 /* Get to the first byte. */ 607 bp += (r_off >> 3); 608 r_off &= 7; 609 610 /* Get first part (low order bits). */ 611 gcode = (*bp++ >> r_off); 612 bits -= (8 - r_off); 613 r_off = 8 - r_off; /* Now, roffset into gcode word. */ 614 615 /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */ 616 if (bits >= 8) { 617 gcode |= *bp++ << r_off; 618 r_off += 8; 619 bits -= 8; 620 } 621 622 /* High order bits. */ 623 gcode |= (*bp & rmask[bits]) << r_off; 624 roffset += n_bits; 625 626 return (gcode); 627} 628 629static int 630cl_block(struct s_zstate *zs) /* Table clear for block compress. */ 631{ 632 long rat; 633 634 checkpoint = in_count + CHECK_GAP; 635 636 if (in_count > 0x007fffff) { /* Shift will overflow. */ 637 rat = bytes_out >> 8; 638 if (rat == 0) /* Don't divide by zero. */ 639 rat = 0x7fffffff; 640 else 641 rat = in_count / rat; 642 } else 643 rat = (in_count << 8) / bytes_out; /* 8 fractional bits. */ 644 if (rat > ratio) 645 ratio = rat; 646 else { 647 ratio = 0; 648 cl_hash(zs, (count_int) hsize); 649 free_ent = FIRST; 650 clear_flg = 1; 651 if (output(zs, (code_int) CLEAR) == -1) 652 return (-1); 653 } 654 return (0); 655} 656 657static void 658cl_hash(struct s_zstate *zs, count_int cl_hsize) /* Reset code table. */ 659{ 660 count_int *htab_p; 661 long i, m1; 662 663 m1 = -1; 664 htab_p = htab + cl_hsize; 665 i = cl_hsize - 16; 666 do { /* Might use Sys V memset(3) here. */ 667 *(htab_p - 16) = m1; 668 *(htab_p - 15) = m1; 669 *(htab_p - 14) = m1; 670 *(htab_p - 13) = m1; 671 *(htab_p - 12) = m1; 672 *(htab_p - 11) = m1; 673 *(htab_p - 10) = m1; 674 *(htab_p - 9) = m1; 675 *(htab_p - 8) = m1; 676 *(htab_p - 7) = m1; 677 *(htab_p - 6) = m1; 678 *(htab_p - 5) = m1; 679 *(htab_p - 4) = m1; 680 *(htab_p - 3) = m1; 681 *(htab_p - 2) = m1; 682 *(htab_p - 1) = m1; 683 htab_p -= 16; 684 } while ((i -= 16) >= 0); 685 for (i += 16; i > 0; i--) 686 *--htab_p = m1; 687} 688 689FILE * 690zopen(const char *fname, const char *mode, int bits) 691{ 692 struct s_zstate *zs; 693 694 if ((mode[0] != 'r' && mode[0] != 'w') || mode[1] != '\0' || 695 bits < 0 || bits > BITS) { 696 errno = EINVAL; 697 return (NULL); 698 } 699 700 if ((zs = calloc(1, sizeof(struct s_zstate))) == NULL) 701 return (NULL); 702 703 maxbits = bits ? bits : BITS; /* User settable max # bits/code. */ 704 maxmaxcode = 1L << maxbits; /* Should NEVER generate this code. */ 705 hsize = HSIZE; /* For dynamic table sizing. */ 706 free_ent = 0; /* First unused entry. */ 707 block_compress = BLOCK_MASK; 708 clear_flg = 0; 709 ratio = 0; 710 checkpoint = CHECK_GAP; 711 in_count = 1; /* Length of input. */ 712 out_count = 0; /* # of codes output (for debugging). */ 713 state = S_START; 714 roffset = 0; 715 size = 0; 716 717 /* 718 * Layering compress on top of stdio in order to provide buffering, 719 * and ensure that reads and write work with the data specified. 720 */ 721 if ((fp = fopen(fname, mode)) == NULL) { 722 free(zs); 723 return (NULL); 724 } 725 switch (*mode) { 726 case 'r': 727 zmode = 'r'; 728 return (funopen(zs, zread, NULL, NULL, zclose)); 729 case 'w': 730 zmode = 'w'; 731 return (funopen(zs, NULL, zwrite, NULL, zclose)); 732 } 733 /* NOTREACHED */ 734 return (NULL); 735} 736