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 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34#if defined(LIBC_SCCS) && !defined(lint) 35static char sccsid[] = "@(#)zopen.c 8.1 (Berkeley) 6/27/93"; 36#endif /* LIBC_SCCS and not lint */ 37 38#include <sys/cdefs.h> 39__FBSDID("$FreeBSD$"); 40 41/*- 42 * fcompress.c - File compression ala IEEE Computer, June 1984. 43 * 44 * Compress authors: 45 * Spencer W. Thomas (decvax!utah-cs!thomas) 46 * Jim McKie (decvax!mcvax!jim) 47 * Steve Davies (decvax!vax135!petsd!peora!srd) 48 * Ken Turkowski (decvax!decwrl!turtlevax!ken) 49 * James A. Woods (decvax!ihnp4!ames!jaw) 50 * Joe Orost (decvax!vax135!petsd!joe) 51 * 52 * Cleaned up and converted to library returning I/O streams by 53 * Diomidis Spinellis <dds@doc.ic.ac.uk>. 54 * 55 * zopen(filename, mode, bits) 56 * Returns a FILE * that can be used for read or write. The modes 57 * supported are only "r" and "w". Seeking is not allowed. On 58 * reading the file is decompressed, on writing it is compressed. 59 * The output is compatible with compress(1) with 16 bit tables. 60 * Any file produced by compress(1) can be read. 61 */ 62 63#include <sys/param.h> 64#include <sys/stat.h> 65 66#include <ctype.h> 67#include <errno.h> 68#include <signal.h> 69#include <stdio.h> 70#include <stdlib.h> 71#include <string.h> 72#include <unistd.h> 73#include "zopen.h" 74 75#define BITS 16 /* Default bits. */ 76#define HSIZE 69001 /* 95% occupancy */ 77 78/* A code_int must be able to hold 2**BITS values of type int, and also -1. */ 79typedef long code_int; 80typedef long count_int; 81 82typedef u_char char_type; 83static char_type magic_header[] = 84 {'\037', '\235'}; /* 1F 9D */ 85 86#define BIT_MASK 0x1f /* Defines for third byte of header. */ 87#define BLOCK_MASK 0x80 88 89/* 90 * Masks 0x40 and 0x20 are free. I think 0x20 should mean that there is 91 * a fourth header byte (for expansion). 92 */ 93#define INIT_BITS 9 /* Initial number of bits/code. */ 94 95#define MAXCODE(n_bits) ((1 << (n_bits)) - 1) 96 97struct s_zstate { 98 FILE *zs_fp; /* File stream for I/O */ 99 char zs_mode; /* r or w */ 100 enum { 101 S_START, S_MIDDLE, S_EOF 102 } zs_state; /* State of computation */ 103 u_int zs_n_bits; /* Number of bits/code. */ 104 u_int zs_maxbits; /* User settable max # bits/code. */ 105 code_int zs_maxcode; /* Maximum code, given n_bits. */ 106 code_int zs_maxmaxcode; /* Should NEVER generate this code. */ 107 count_int zs_htab [HSIZE]; 108 u_short zs_codetab [HSIZE]; 109 code_int zs_hsize; /* For dynamic table sizing. */ 110 code_int zs_free_ent; /* First unused entry. */ 111 /* 112 * Block compression parameters -- after all codes are used up, 113 * and compression rate changes, start over. 114 */ 115 int zs_block_compress; 116 int zs_clear_flg; 117 long zs_ratio; 118 count_int zs_checkpoint; 119 u_int zs_offset; 120 long zs_in_count; /* Length of input. */ 121 long zs_bytes_out; /* Length of compressed output. */ 122 long zs_out_count; /* # of codes output (for debugging). */ 123 char_type zs_buf[BITS]; 124 union { 125 struct { 126 long zs_fcode; 127 code_int zs_ent; 128 code_int zs_hsize_reg; 129 int zs_hshift; 130 } w; /* Write parameters */ 131 struct { 132 char_type *zs_stackp; 133 int zs_finchar; 134 code_int zs_code, zs_oldcode, zs_incode; 135 int zs_roffset, zs_size; 136 char_type zs_gbuf[BITS]; 137 } r; /* Read parameters */ 138 } u; 139}; 140 141/* Definitions to retain old variable names */ 142#define fp zs->zs_fp 143#define zmode zs->zs_mode 144#define state zs->zs_state 145#define n_bits zs->zs_n_bits 146#define maxbits zs->zs_maxbits 147#define maxcode zs->zs_maxcode 148#define maxmaxcode zs->zs_maxmaxcode 149#define htab zs->zs_htab 150#define codetab zs->zs_codetab 151#define hsize zs->zs_hsize 152#define free_ent zs->zs_free_ent 153#define block_compress zs->zs_block_compress 154#define clear_flg zs->zs_clear_flg 155#define ratio zs->zs_ratio 156#define checkpoint zs->zs_checkpoint 157#define offset zs->zs_offset 158#define in_count zs->zs_in_count 159#define bytes_out zs->zs_bytes_out 160#define out_count zs->zs_out_count 161#define buf zs->zs_buf 162#define fcode zs->u.w.zs_fcode 163#define hsize_reg zs->u.w.zs_hsize_reg 164#define ent zs->u.w.zs_ent 165#define hshift zs->u.w.zs_hshift 166#define stackp zs->u.r.zs_stackp 167#define finchar zs->u.r.zs_finchar 168#define code zs->u.r.zs_code 169#define oldcode zs->u.r.zs_oldcode 170#define incode zs->u.r.zs_incode 171#define roffset zs->u.r.zs_roffset 172#define size zs->u.r.zs_size 173#define gbuf zs->u.r.zs_gbuf 174 175/* 176 * To save much memory, we overlay the table used by compress() with those 177 * used by decompress(). The tab_prefix table is the same size and type as 178 * the codetab. The tab_suffix table needs 2**BITS characters. We get this 179 * from the beginning of htab. The output stack uses the rest of htab, and 180 * contains characters. There is plenty of room for any possible stack 181 * (stack used to be 8000 characters). 182 */ 183 184#define htabof(i) htab[i] 185#define codetabof(i) codetab[i] 186 187#define tab_prefixof(i) codetabof(i) 188#define tab_suffixof(i) ((char_type *)(htab))[i] 189#define de_stack ((char_type *)&tab_suffixof(1 << BITS)) 190 191#define CHECK_GAP 10000 /* Ratio check interval. */ 192 193/* 194 * the next two codes should not be changed lightly, as they must not 195 * lie within the contiguous general code space. 196 */ 197#define FIRST 257 /* First free entry. */ 198#define CLEAR 256 /* Table clear output code. */ 199 200static int cl_block(struct s_zstate *); 201static void cl_hash(struct s_zstate *, count_int); 202static code_int getcode(struct s_zstate *); 203static int output(struct s_zstate *, code_int); 204static int zclose(void *); 205static int zread(void *, char *, int); 206static int zwrite(void *, const char *, int); 207 208/*- 209 * Algorithm from "A Technique for High Performance Data Compression", 210 * Terry A. Welch, IEEE Computer Vol 17, No 6 (June 1984), pp 8-19. 211 * 212 * Algorithm: 213 * Modified Lempel-Ziv method (LZW). Basically finds common 214 * substrings and replaces them with a variable size code. This is 215 * deterministic, and can be done on the fly. Thus, the decompression 216 * procedure needs no input table, but tracks the way the table was built. 217 */ 218 219/*- 220 * compress write 221 * 222 * Algorithm: use open addressing double hashing (no chaining) on the 223 * prefix code / next character combination. We do a variant of Knuth's 224 * algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime 225 * secondary probe. Here, the modular division first probe is gives way 226 * to a faster exclusive-or manipulation. Also do block compression with 227 * an adaptive reset, whereby the code table is cleared when the compression 228 * ratio decreases, but after the table fills. The variable-length output 229 * codes are re-sized at this point, and a special CLEAR code is generated 230 * for the decompressor. Late addition: construct the table according to 231 * file size for noticeable speed improvement on small files. Please direct 232 * questions about this implementation to ames!jaw. 233 */ 234static int 235zwrite(void *cookie, const char *wbp, int num) 236{ 237 code_int i; 238 int c, disp; 239 struct s_zstate *zs; 240 const u_char *bp; 241 u_char tmp; 242 int count; 243 244 if (num == 0) 245 return (0); 246 247 zs = cookie; 248 count = num; 249 bp = (const u_char *)wbp; 250 if (state == S_MIDDLE) 251 goto middle; 252 state = S_MIDDLE; 253 254 maxmaxcode = 1L << maxbits; 255 if (fwrite(magic_header, 256 sizeof(char), sizeof(magic_header), fp) != sizeof(magic_header)) 257 return (-1); 258 tmp = (u_char)((maxbits) | block_compress); 259 if (fwrite(&tmp, sizeof(char), sizeof(tmp), fp) != sizeof(tmp)) 260 return (-1); 261 262 offset = 0; 263 bytes_out = 3; /* Includes 3-byte header mojo. */ 264 out_count = 0; 265 clear_flg = 0; 266 ratio = 0; 267 in_count = 1; 268 checkpoint = CHECK_GAP; 269 maxcode = MAXCODE(n_bits = INIT_BITS); 270 free_ent = ((block_compress) ? FIRST : 256); 271 272 ent = *bp++; 273 --count; 274 275 hshift = 0; 276 for (fcode = (long)hsize; fcode < 65536L; fcode *= 2L) 277 hshift++; 278 hshift = 8 - hshift; /* Set hash code range bound. */ 279 280 hsize_reg = hsize; 281 cl_hash(zs, (count_int)hsize_reg); /* Clear hash table. */ 282 283middle: for (i = 0; count--;) { 284 c = *bp++; 285 in_count++; 286 fcode = (long)(((long)c << maxbits) + ent); 287 i = ((c << hshift) ^ ent); /* Xor hashing. */ 288 289 if (htabof(i) == fcode) { 290 ent = codetabof(i); 291 continue; 292 } else if ((long)htabof(i) < 0) /* Empty slot. */ 293 goto nomatch; 294 disp = hsize_reg - i; /* Secondary hash (after G. Knott). */ 295 if (i == 0) 296 disp = 1; 297probe: if ((i -= disp) < 0) 298 i += hsize_reg; 299 300 if (htabof(i) == fcode) { 301 ent = codetabof(i); 302 continue; 303 } 304 if ((long)htabof(i) >= 0) 305 goto probe; 306nomatch: if (output(zs, (code_int) ent) == -1) 307 return (-1); 308 out_count++; 309 ent = c; 310 if (free_ent < maxmaxcode) { 311 codetabof(i) = free_ent++; /* code -> hashtable */ 312 htabof(i) = fcode; 313 } else if ((count_int)in_count >= 314 checkpoint && block_compress) { 315 if (cl_block(zs) == -1) 316 return (-1); 317 } 318 } 319 return (num); 320} 321 322static int 323zclose(void *cookie) 324{ 325 struct s_zstate *zs; 326 int rval; 327 328 zs = cookie; 329 if (zmode == 'w') { /* Put out the final code. */ 330 if (output(zs, (code_int) ent) == -1) { 331 (void)fclose(fp); 332 free(zs); 333 return (-1); 334 } 335 out_count++; 336 if (output(zs, (code_int) - 1) == -1) { 337 (void)fclose(fp); 338 free(zs); 339 return (-1); 340 } 341 } 342 rval = fclose(fp) == EOF ? -1 : 0; 343 free(zs); 344 return (rval); 345} 346 347/*- 348 * Output the given code. 349 * Inputs: 350 * code: A n_bits-bit integer. If == -1, then EOF. This assumes 351 * that n_bits =< (long)wordsize - 1. 352 * Outputs: 353 * Outputs code to the file. 354 * Assumptions: 355 * Chars are 8 bits long. 356 * Algorithm: 357 * Maintain a BITS character long buffer (so that 8 codes will 358 * fit in it exactly). Use the VAX insv instruction to insert each 359 * code in turn. When the buffer fills up empty it and start over. 360 */ 361 362static char_type lmask[9] = 363 {0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80, 0x00}; 364static char_type rmask[9] = 365 {0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff}; 366 367static int 368output(struct s_zstate *zs, code_int ocode) 369{ 370 int r_off; 371 u_int bits; 372 char_type *bp; 373 374 r_off = offset; 375 bits = n_bits; 376 bp = buf; 377 if (ocode >= 0) { 378 /* Get to the first byte. */ 379 bp += (r_off >> 3); 380 r_off &= 7; 381 /* 382 * Since ocode is always >= 8 bits, only need to mask the first 383 * hunk on the left. 384 */ 385 *bp = (*bp & rmask[r_off]) | ((ocode << r_off) & lmask[r_off]); 386 bp++; 387 bits -= (8 - r_off); 388 ocode >>= 8 - r_off; 389 /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */ 390 if (bits >= 8) { 391 *bp++ = ocode; 392 ocode >>= 8; 393 bits -= 8; 394 } 395 /* Last bits. */ 396 if (bits) 397 *bp = ocode; 398 offset += n_bits; 399 if (offset == (n_bits << 3)) { 400 bp = buf; 401 bits = n_bits; 402 bytes_out += bits; 403 if (fwrite(bp, sizeof(char), bits, fp) != bits) 404 return (-1); 405 bp += bits; 406 bits = 0; 407 offset = 0; 408 } 409 /* 410 * If the next entry is going to be too big for the ocode size, 411 * then increase it, if possible. 412 */ 413 if (free_ent > maxcode || (clear_flg > 0)) { 414 /* 415 * Write the whole buffer, because the input side won't 416 * discover the size increase until after it has read it. 417 */ 418 if (offset > 0) { 419 if (fwrite(buf, 1, n_bits, fp) != n_bits) 420 return (-1); 421 bytes_out += n_bits; 422 } 423 offset = 0; 424 425 if (clear_flg) { 426 maxcode = MAXCODE(n_bits = INIT_BITS); 427 clear_flg = 0; 428 } else { 429 n_bits++; 430 if (n_bits == maxbits) 431 maxcode = maxmaxcode; 432 else 433 maxcode = MAXCODE(n_bits); 434 } 435 } 436 } else { 437 /* At EOF, write the rest of the buffer. */ 438 if (offset > 0) { 439 offset = (offset + 7) / 8; 440 if (fwrite(buf, 1, offset, fp) != offset) 441 return (-1); 442 bytes_out += offset; 443 } 444 offset = 0; 445 } 446 return (0); 447} 448 449/* 450 * Decompress read. This routine adapts to the codes in the file building 451 * the "string" table on-the-fly; requiring no table to be stored in the 452 * compressed file. The tables used herein are shared with those of the 453 * compress() routine. See the definitions above. 454 */ 455static int 456zread(void *cookie, char *rbp, int num) 457{ 458 u_int count; 459 struct s_zstate *zs; 460 u_char *bp, header[3]; 461 462 if (num == 0) 463 return (0); 464 465 zs = cookie; 466 count = num; 467 bp = (u_char *)rbp; 468 switch (state) { 469 case S_START: 470 state = S_MIDDLE; 471 break; 472 case S_MIDDLE: 473 goto middle; 474 case S_EOF: 475 goto eof; 476 } 477 478 /* Check the magic number */ 479 if (fread(header, 480 sizeof(char), sizeof(header), fp) != sizeof(header) || 481 memcmp(header, magic_header, sizeof(magic_header)) != 0) { 482 errno = EFTYPE; 483 return (-1); 484 } 485 maxbits = header[2]; /* Set -b from file. */ 486 block_compress = maxbits & BLOCK_MASK; 487 maxbits &= BIT_MASK; 488 maxmaxcode = 1L << maxbits; 489 if (maxbits > BITS || maxbits < 12) { 490 errno = EFTYPE; 491 return (-1); 492 } 493 /* As above, initialize the first 256 entries in the table. */ 494 maxcode = MAXCODE(n_bits = INIT_BITS); 495 for (code = 255; code >= 0; code--) { 496 tab_prefixof(code) = 0; 497 tab_suffixof(code) = (char_type) code; 498 } 499 free_ent = block_compress ? FIRST : 256; 500 501 finchar = oldcode = getcode(zs); 502 if (oldcode == -1) /* EOF already? */ 503 return (0); /* Get out of here */ 504 505 /* First code must be 8 bits = char. */ 506 *bp++ = (u_char)finchar; 507 count--; 508 stackp = de_stack; 509 510 while ((code = getcode(zs)) > -1) { 511 512 if ((code == CLEAR) && block_compress) { 513 for (code = 255; code >= 0; code--) 514 tab_prefixof(code) = 0; 515 clear_flg = 1; 516 free_ent = FIRST; 517 oldcode = -1; 518 continue; 519 } 520 incode = code; 521 522 /* Special case for kWkWk string. */ 523 if (code >= free_ent) { 524 if (code > free_ent || oldcode == -1) { 525 /* Bad stream. */ 526 errno = EINVAL; 527 return (-1); 528 } 529 *stackp++ = finchar; 530 code = oldcode; 531 } 532 /* 533 * The above condition ensures that code < free_ent. 534 * The construction of tab_prefixof in turn guarantees that 535 * each iteration decreases code and therefore stack usage is 536 * bound by 1 << BITS - 256. 537 */ 538 539 /* Generate output characters in reverse order. */ 540 while (code >= 256) { 541 *stackp++ = tab_suffixof(code); 542 code = tab_prefixof(code); 543 } 544 *stackp++ = finchar = tab_suffixof(code); 545 546 /* And put them out in forward order. */ 547middle: do { 548 if (count-- == 0) 549 return (num); 550 *bp++ = *--stackp; 551 } while (stackp > de_stack); 552 553 /* Generate the new entry. */ 554 if ((code = free_ent) < maxmaxcode && oldcode != -1) { 555 tab_prefixof(code) = (u_short) oldcode; 556 tab_suffixof(code) = finchar; 557 free_ent = code + 1; 558 } 559 560 /* Remember previous code. */ 561 oldcode = incode; 562 } 563 state = S_EOF; 564eof: return (num - count); 565} 566 567/*- 568 * Read one code from the standard input. If EOF, return -1. 569 * Inputs: 570 * stdin 571 * Outputs: 572 * code or -1 is returned. 573 */ 574static code_int 575getcode(struct s_zstate *zs) 576{ 577 code_int gcode; 578 int r_off, bits; 579 char_type *bp; 580 581 bp = gbuf; 582 if (clear_flg > 0 || roffset >= size || free_ent > maxcode) { 583 /* 584 * If the next entry will be too big for the current gcode 585 * size, then we must increase the size. This implies reading 586 * a new buffer full, too. 587 */ 588 if (free_ent > maxcode) { 589 n_bits++; 590 if (n_bits == maxbits) /* Won't get any bigger now. */ 591 maxcode = maxmaxcode; 592 else 593 maxcode = MAXCODE(n_bits); 594 } 595 if (clear_flg > 0) { 596 maxcode = MAXCODE(n_bits = INIT_BITS); 597 clear_flg = 0; 598 } 599 size = fread(gbuf, 1, n_bits, fp); 600 if (size <= 0) /* End of file. */ 601 return (-1); 602 roffset = 0; 603 /* Round size down to integral number of codes. */ 604 size = (size << 3) - (n_bits - 1); 605 } 606 r_off = roffset; 607 bits = n_bits; 608 609 /* Get to the first byte. */ 610 bp += (r_off >> 3); 611 r_off &= 7; 612 613 /* Get first part (low order bits). */ 614 gcode = (*bp++ >> r_off); 615 bits -= (8 - r_off); 616 r_off = 8 - r_off; /* Now, roffset into gcode word. */ 617 618 /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */ 619 if (bits >= 8) { 620 gcode |= *bp++ << r_off; 621 r_off += 8; 622 bits -= 8; 623 } 624 625 /* High order bits. */ 626 gcode |= (*bp & rmask[bits]) << r_off; 627 roffset += n_bits; 628 629 return (gcode); 630} 631 632static int 633cl_block(struct s_zstate *zs) /* Table clear for block compress. */ 634{ 635 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 660static void 661cl_hash(struct s_zstate *zs, count_int cl_hsize) /* Reset code table. */ 662{ 663 count_int *htab_p; 664 long i, m1; 665 666 m1 = -1; 667 htab_p = htab + cl_hsize; 668 i = cl_hsize - 16; 669 do { /* Might use Sys V memset(3) here. */ 670 *(htab_p - 16) = m1; 671 *(htab_p - 15) = m1; 672 *(htab_p - 14) = m1; 673 *(htab_p - 13) = m1; 674 *(htab_p - 12) = m1; 675 *(htab_p - 11) = m1; 676 *(htab_p - 10) = m1; 677 *(htab_p - 9) = m1; 678 *(htab_p - 8) = m1; 679 *(htab_p - 7) = m1; 680 *(htab_p - 6) = m1; 681 *(htab_p - 5) = m1; 682 *(htab_p - 4) = m1; 683 *(htab_p - 3) = m1; 684 *(htab_p - 2) = m1; 685 *(htab_p - 1) = m1; 686 htab_p -= 16; 687 } while ((i -= 16) >= 0); 688 for (i += 16; i > 0; i--) 689 *--htab_p = m1; 690} 691 692FILE * 693zopen(const char *fname, const char *mode, int bits) 694{ 695 struct s_zstate *zs; 696 697 if ((mode[0] != 'r' && mode[0] != 'w') || mode[1] != '\0' || 698 bits < 0 || bits > BITS) { 699 errno = EINVAL; 700 return (NULL); 701 } 702 703 if ((zs = calloc(1, sizeof(struct s_zstate))) == NULL) 704 return (NULL); 705 706 maxbits = bits ? bits : BITS; /* User settable max # bits/code. */ 707 maxmaxcode = 1L << maxbits; /* Should NEVER generate this code. */ 708 hsize = HSIZE; /* For dynamic table sizing. */ 709 free_ent = 0; /* First unused entry. */ 710 block_compress = BLOCK_MASK; 711 clear_flg = 0; 712 ratio = 0; 713 checkpoint = CHECK_GAP; 714 in_count = 1; /* Length of input. */ 715 out_count = 0; /* # of codes output (for debugging). */ 716 state = S_START; 717 roffset = 0; 718 size = 0; 719 720 /* 721 * Layering compress on top of stdio in order to provide buffering, 722 * and ensure that reads and write work with the data specified. 723 */ 724 if ((fp = fopen(fname, mode)) == NULL) { 725 free(zs); 726 return (NULL); 727 } 728 switch (*mode) { 729 case 'r': 730 zmode = 'r'; 731 return (funopen(zs, zread, NULL, NULL, zclose)); 732 case 'w': 733 zmode = 'w'; 734 return (funopen(zs, NULL, zwrite, NULL, zclose)); 735 } 736 /* NOTREACHED */ 737 return (NULL); 738} 739