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 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. */ 79 typedef long code_int; 80 typedef long count_int; 81 82 typedef u_char char_type; 83 static 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 97 struct 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 int zs_n_bits; /* Number of bits/code. */ 104 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 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 paramenters */ 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. */ 199 200 static int cl_block __P((struct s_zstate *)); 201 static void cl_hash __P((struct s_zstate *, count_int)); 202 static code_int getcode __P((struct s_zstate *)); 203 static int output __P((struct s_zstate *, code_int)); 204 static int zclose __P((void *)); 205 static int zread __P((void *, char *, int)); 206 static int zwrite __P((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 */ 234 static int 235 zwrite(cookie, wbp, num) 236 void *cookie; 237 const char *wbp; 238 int num; 239 { 240 register code_int i; 241 register int c, disp; 242 struct s_zstate *zs; 243 const u_char *bp; 244 u_char tmp; 245 int count; 246 247 if (num == 0) 248 return (0); 249 250 zs = cookie; 251 count = num; 252 bp = (u_char *)wbp; 253 if (state == S_MIDDLE) 254 goto middle; 255 state = S_MIDDLE; 256 257 maxmaxcode = 1L << BITS; 258 if (fwrite(magic_header, 259 sizeof(char), sizeof(magic_header), fp) != sizeof(magic_header)) 260 return (-1); 261 tmp = (u_char)(BITS | block_compress); 262 if (fwrite(&tmp, sizeof(char), sizeof(tmp), fp) != sizeof(tmp)) 263 return (-1); 264 265 offset = 0; 266 bytes_out = 3; /* Includes 3-byte header mojo. */ 267 out_count = 0; 268 clear_flg = 0; 269 ratio = 0; 270 in_count = 1; 271 checkpoint = CHECK_GAP; 272 maxcode = MAXCODE(n_bits = INIT_BITS); 273 free_ent = ((block_compress) ? FIRST : 256); 274 275 ent = *bp++; 276 --count; 277 278 hshift = 0; 279 for (fcode = (long)hsize; fcode < 65536L; fcode *= 2L) 280 hshift++; 281 hshift = 8 - hshift; /* Set hash code range bound. */ 282 283 hsize_reg = hsize; 284 cl_hash(zs, (count_int)hsize_reg); /* Clear hash table. */ 285 286 middle: for (i = 0; count--;) { 287 c = *bp++; 288 in_count++; 289 fcode = (long)(((long)c << maxbits) + ent); 290 i = ((c << hshift) ^ ent); /* Xor hashing. */ 291 292 if (htabof(i) == fcode) { 293 ent = codetabof(i); 294 continue; 295 } else if ((long)htabof(i) < 0) /* Empty slot. */ 296 goto nomatch; 297 disp = hsize_reg - i; /* Secondary hash (after G. Knott). */ 298 if (i == 0) 299 disp = 1; 300 probe: if ((i -= disp) < 0) 301 i += hsize_reg; 302 303 if (htabof(i) == fcode) { 304 ent = codetabof(i); 305 continue; 306 } 307 if ((long)htabof(i) >= 0) 308 goto probe; 309 nomatch: if (output(zs, (code_int) ent) == -1) 310 return (-1); 311 out_count++; 312 ent = c; 313 if (free_ent < maxmaxcode) { 314 codetabof(i) = free_ent++; /* code -> hashtable */ 315 htabof(i) = fcode; 316 } else if ((count_int)in_count >= 317 checkpoint && block_compress) { 318 if (cl_block(zs) == -1) 319 return (-1); 320 } 321 } 322 return (num); 323 } 324 325 static int 326 zclose(cookie) 327 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(zs, ocode) 373 struct s_zstate *zs; 374 code_int ocode; 375 { 376 register int bits, r_off; 377 register char_type *bp; 378 379 r_off = offset; 380 bits = n_bits; 381 bp = buf; 382 if (ocode >= 0) { 383 /* Get to the first byte. */ 384 bp += (r_off >> 3); 385 r_off &= 7; 386 /* 387 * Since ocode is always >= 8 bits, only need to mask the first 388 * hunk on the left. 389 */ 390 *bp = (*bp & rmask[r_off]) | (ocode << r_off) & lmask[r_off]; 391 bp++; 392 bits -= (8 - r_off); 393 ocode >>= 8 - r_off; 394 /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */ 395 if (bits >= 8) { 396 *bp++ = ocode; 397 ocode >>= 8; 398 bits -= 8; 399 } 400 /* Last bits. */ 401 if (bits) 402 *bp = ocode; 403 offset += n_bits; 404 if (offset == (n_bits << 3)) { 405 bp = buf; 406 bits = n_bits; 407 bytes_out += bits; 408 if (fwrite(bp, sizeof(char), bits, fp) != bits) 409 return (-1); 410 bp += bits; 411 bits = 0; 412 offset = 0; 413 } 414 /* 415 * If the next entry is going to be too big for the ocode size, 416 * then increase it, if possible. 417 */ 418 if (free_ent > maxcode || (clear_flg > 0)) { 419 /* 420 * Write the whole buffer, because the input side won't 421 * discover the size increase until after it has read it. 422 */ 423 if (offset > 0) { 424 if (fwrite(buf, 1, n_bits, fp) != n_bits) 425 return (-1); 426 bytes_out += n_bits; 427 } 428 offset = 0; 429 430 if (clear_flg) { 431 maxcode = MAXCODE(n_bits = INIT_BITS); 432 clear_flg = 0; 433 } else { 434 n_bits++; 435 if (n_bits == maxbits) 436 maxcode = maxmaxcode; 437 else 438 maxcode = MAXCODE(n_bits); 439 } 440 } 441 } else { 442 /* At EOF, write the rest of the buffer. */ 443 if (offset > 0) { 444 offset = (offset + 7) / 8; 445 if (fwrite(buf, 1, offset, fp) != offset) 446 return (-1); 447 bytes_out += offset; 448 } 449 offset = 0; 450 } 451 return (0); 452 } 453 454 /* 455 * Decompress read. This routine adapts to the codes in the file building 456 * the "string" table on-the-fly; requiring no table to be stored in the 457 * compressed file. The tables used herein are shared with those of the 458 * compress() routine. See the definitions above. 459 */ 460 static int 461 zread(cookie, rbp, num) 462 void *cookie; 463 char *rbp; 464 int num; 465 { 466 register u_int count; 467 struct s_zstate *zs; 468 u_char *bp, header[3]; 469 470 if (num == 0) 471 return (0); 472 473 zs = cookie; 474 count = num; 475 bp = (u_char *)rbp; 476 switch (state) { 477 case S_START: 478 state = S_MIDDLE; 479 break; 480 case S_MIDDLE: 481 goto middle; 482 case S_EOF: 483 goto eof; 484 } 485 486 /* Check the magic number */ 487 if (fread(header, 488 sizeof(char), sizeof(header), fp) != sizeof(header) || 489 memcmp(header, magic_header, sizeof(magic_header)) != 0) { 490 errno = EFTYPE; 491 return (-1); 492 } 493 maxbits = header[2]; /* Set -b from file. */ 494 block_compress = maxbits & BLOCK_MASK; 495 maxbits &= BIT_MASK; 496 maxmaxcode = 1L << maxbits; 497 if (maxbits > BITS) { 498 errno = EFTYPE; 499 return (-1); 500 } 501 /* As above, initialize the first 256 entries in the table. */ 502 maxcode = MAXCODE(n_bits = INIT_BITS); 503 for (code = 255; code >= 0; code--) { 504 tab_prefixof(code) = 0; 505 tab_suffixof(code) = (char_type) code; 506 } 507 free_ent = block_compress ? FIRST : 256; 508 509 finchar = oldcode = getcode(zs); 510 if (oldcode == -1) /* EOF already? */ 511 return (0); /* Get out of here */ 512 513 /* First code must be 8 bits = char. */ 514 *bp++ = (u_char)finchar; 515 count--; 516 stackp = de_stack; 517 518 while ((code = getcode(zs)) > -1) { 519 520 if ((code == CLEAR) && block_compress) { 521 for (code = 255; code >= 0; code--) 522 tab_prefixof(code) = 0; 523 clear_flg = 1; 524 free_ent = FIRST - 1; 525 if ((code = getcode(zs)) == -1) /* O, untimely death! */ 526 break; 527 } 528 incode = code; 529 530 /* Special case for KwKwK string. */ 531 if (code >= free_ent) { 532 *stackp++ = finchar; 533 code = oldcode; 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. */ 544 middle: 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) { 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; 561 eof: 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 */ 571 static code_int 572 getcode(zs) 573 struct s_zstate *zs; 574 { 575 register code_int gcode; 576 register int r_off, bits; 577 register char_type *bp; 578 579 bp = gbuf; 580 if (clear_flg > 0 || roffset >= size || free_ent > maxcode) { 581 /* 582 * If the next entry will be too big for the current gcode 583 * size, then we must increase the size. This implies reading 584 * a new buffer full, too. 585 */ 586 if (free_ent > maxcode) { 587 n_bits++; 588 if (n_bits == maxbits) /* Won't get any bigger now. */ 589 maxcode = maxmaxcode; 590 else 591 maxcode = MAXCODE(n_bits); 592 } 593 if (clear_flg > 0) { 594 maxcode = MAXCODE(n_bits = INIT_BITS); 595 clear_flg = 0; 596 } 597 size = fread(gbuf, 1, n_bits, fp); 598 if (size <= 0) /* End of file. */ 599 return (-1); 600 roffset = 0; 601 /* Round size down to integral number of codes. */ 602 size = (size << 3) - (n_bits - 1); 603 } 604 r_off = roffset; 605 bits = n_bits; 606 607 /* Get to the first byte. */ 608 bp += (r_off >> 3); 609 r_off &= 7; 610 611 /* Get first part (low order bits). */ 612 gcode = (*bp++ >> r_off); 613 bits -= (8 - r_off); 614 r_off = 8 - r_off; /* Now, roffset into gcode word. */ 615 616 /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */ 617 if (bits >= 8) { 618 gcode |= *bp++ << r_off; 619 r_off += 8; 620 bits -= 8; 621 } 622 623 /* High order bits. */ 624 gcode |= (*bp & rmask[bits]) << r_off; 625 roffset += n_bits; 626 627 return (gcode); 628 } 629 630 static int 631 cl_block(zs) /* Table clear for block compress. */ 632 struct s_zstate *zs; 633 { 634 register long rat; 635 636 checkpoint = in_count + CHECK_GAP; 637 638 if (in_count > 0x007fffff) { /* Shift will overflow. */ 639 rat = bytes_out >> 8; 640 if (rat == 0) /* Don't divide by zero. */ 641 rat = 0x7fffffff; 642 else 643 rat = in_count / rat; 644 } else 645 rat = (in_count << 8) / bytes_out; /* 8 fractional bits. */ 646 if (rat > ratio) 647 ratio = rat; 648 else { 649 ratio = 0; 650 cl_hash(zs, (count_int) hsize); 651 free_ent = FIRST; 652 clear_flg = 1; 653 if (output(zs, (code_int) CLEAR) == -1) 654 return (-1); 655 } 656 return (0); 657 } 658 659 static void 660 cl_hash(zs, cl_hsize) /* Reset code table. */ 661 struct s_zstate *zs; 662 register count_int cl_hsize; 663 { 664 register count_int *htab_p; 665 register long i, m1; 666 667 m1 = -1; 668 htab_p = htab + cl_hsize; 669 i = cl_hsize - 16; 670 do { /* Might use Sys V memset(3) here. */ 671 *(htab_p - 16) = m1; 672 *(htab_p - 15) = m1; 673 *(htab_p - 14) = m1; 674 *(htab_p - 13) = m1; 675 *(htab_p - 12) = m1; 676 *(htab_p - 11) = m1; 677 *(htab_p - 10) = m1; 678 *(htab_p - 9) = m1; 679 *(htab_p - 8) = m1; 680 *(htab_p - 7) = m1; 681 *(htab_p - 6) = m1; 682 *(htab_p - 5) = m1; 683 *(htab_p - 4) = m1; 684 *(htab_p - 3) = m1; 685 *(htab_p - 2) = m1; 686 *(htab_p - 1) = m1; 687 htab_p -= 16; 688 } while ((i -= 16) >= 0); 689 for (i += 16; i > 0; i--) 690 *--htab_p = m1; 691 } 692 693 FILE * 694 zopen(fname, mode, bits) 695 const char *fname, *mode; 696 int bits; 697 { 698 struct s_zstate *zs; 699 700 if (mode[0] != 'r' && mode[0] != 'w' || mode[1] != '\0' || 701 bits < 0 || bits > BITS) { 702 errno = EINVAL; 703 return (NULL); 704 } 705 706 if ((zs = calloc(1, sizeof(struct s_zstate))) == NULL) 707 return (NULL); 708 709 maxbits = bits ? bits : BITS; /* User settable max # bits/code. */ 710 maxmaxcode = 1 << BITS; /* Should NEVER generate this code. */ 711 hsize = HSIZE; /* For dynamic table sizing. */ 712 free_ent = 0; /* First unused entry. */ 713 block_compress = BLOCK_MASK; 714 clear_flg = 0; 715 ratio = 0; 716 checkpoint = CHECK_GAP; 717 in_count = 1; /* Length of input. */ 718 out_count = 0; /* # of codes output (for debugging). */ 719 state = S_START; 720 roffset = 0; 721 size = 0; 722 723 /* 724 * Layering compress on top of stdio in order to provide buffering, 725 * and ensure that reads and write work with the data specified. 726 */ 727 if ((fp = fopen(fname, mode)) == NULL) { 728 free(zs); 729 return (NULL); 730 } 731 switch (*mode) { 732 case 'r': 733 zmode = 'r'; 734 return (funopen(zs, zread, NULL, NULL, zclose)); 735 case 'w': 736 zmode = 'w'; 737 return (funopen(zs, NULL, zwrite, NULL, zclose)); 738 } 739 /* NOTREACHED */ 740 } 741