1 /* $NetBSD: zopen.c,v 1.5 1995/03/26 09:44:53 glass 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 1.5 1995/03/26 09:44:53 glass 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 static int zread __P((void *, char *, int)); 212 static int zwrite __P((void *, const char *, int)); 213 214 /*- 215 * Algorithm from "A Technique for High Performance Data Compression", 216 * Terry A. Welch, IEEE Computer Vol 17, No 6 (June 1984), pp 8-19. 217 * 218 * Algorithm: 219 * Modified Lempel-Ziv method (LZW). Basically finds common 220 * substrings and replaces them with a variable size code. This is 221 * deterministic, and can be done on the fly. Thus, the decompression 222 * procedure needs no input table, but tracks the way the table was built. 223 */ 224 225 /*- 226 * compress write 227 * 228 * Algorithm: use open addressing double hashing (no chaining) on the 229 * prefix code / next character combination. We do a variant of Knuth's 230 * algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime 231 * secondary probe. Here, the modular division first probe is gives way 232 * to a faster exclusive-or manipulation. Also do block compression with 233 * an adaptive reset, whereby the code table is cleared when the compression 234 * ratio decreases, but after the table fills. The variable-length output 235 * codes are re-sized at this point, and a special CLEAR code is generated 236 * for the decompressor. Late addition: construct the table according to 237 * file size for noticeable speed improvement on small files. Please direct 238 * questions about this implementation to ames!jaw. 239 */ 240 static int 241 zwrite(cookie, wbp, num) 242 void *cookie; 243 const char *wbp; 244 int num; 245 { 246 register code_int i; 247 register int c, disp; 248 struct s_zstate *zs; 249 const u_char *bp; 250 u_char tmp; 251 int count; 252 253 if (num == 0) 254 return (0); 255 256 zs = cookie; 257 count = num; 258 bp = (u_char *)wbp; 259 if (state == S_MIDDLE) 260 goto middle; 261 state = S_MIDDLE; 262 263 maxmaxcode = 1L << maxbits; 264 if (fwrite(magic_header, 265 sizeof(char), sizeof(magic_header), fp) != sizeof(magic_header)) 266 return (-1); 267 tmp = (u_char)(maxbits | block_compress); 268 if (fwrite(&tmp, sizeof(char), sizeof(tmp), fp) != sizeof(tmp)) 269 return (-1); 270 271 offset = 0; 272 bytes_out = 3; /* Includes 3-byte header mojo. */ 273 out_count = 0; 274 clear_flg = 0; 275 ratio = 0; 276 in_count = 1; 277 checkpoint = CHECK_GAP; 278 maxcode = MAXCODE(n_bits = INIT_BITS); 279 free_ent = ((block_compress) ? FIRST : 256); 280 281 ent = *bp++; 282 --count; 283 284 hshift = 0; 285 for (fcode = (long)hsize; fcode < 65536L; fcode *= 2L) 286 hshift++; 287 hshift = 8 - hshift; /* Set hash code range bound. */ 288 289 hsize_reg = hsize; 290 cl_hash(zs, (count_int)hsize_reg); /* Clear hash table. */ 291 292 middle: for (i = 0; count--;) { 293 c = *bp++; 294 in_count++; 295 fcode = (long)(((long)c << maxbits) + ent); 296 i = ((c << hshift) ^ ent); /* Xor hashing. */ 297 298 if (htabof(i) == fcode) { 299 ent = codetabof(i); 300 continue; 301 } else if ((long)htabof(i) < 0) /* Empty slot. */ 302 goto nomatch; 303 disp = hsize_reg - i; /* Secondary hash (after G. Knott). */ 304 if (i == 0) 305 disp = 1; 306 probe: if ((i -= disp) < 0) 307 i += hsize_reg; 308 309 if (htabof(i) == fcode) { 310 ent = codetabof(i); 311 continue; 312 } 313 if ((long)htabof(i) >= 0) 314 goto probe; 315 nomatch: if (output(zs, (code_int) ent) == -1) 316 return (-1); 317 out_count++; 318 ent = c; 319 if (free_ent < maxmaxcode) { 320 codetabof(i) = free_ent++; /* code -> hashtable */ 321 htabof(i) = fcode; 322 } else if ((count_int)in_count >= 323 checkpoint && block_compress) { 324 if (cl_block(zs) == -1) 325 return (-1); 326 } 327 } 328 return (num); 329 } 330 331 static int 332 zclose(cookie) 333 void *cookie; 334 { 335 struct s_zstate *zs; 336 int rval; 337 338 zs = cookie; 339 if (zmode == 'w') { /* Put out the final code. */ 340 if (output(zs, (code_int) ent) == -1) { 341 (void)fclose(fp); 342 free(zs); 343 return (-1); 344 } 345 out_count++; 346 if (output(zs, (code_int) - 1) == -1) { 347 (void)fclose(fp); 348 free(zs); 349 return (-1); 350 } 351 } 352 rval = fclose(fp) == EOF ? -1 : 0; 353 free(zs); 354 return (rval); 355 } 356 357 /*- 358 * Output the given code. 359 * Inputs: 360 * code: A n_bits-bit integer. If == -1, then EOF. This assumes 361 * that n_bits =< (long)wordsize - 1. 362 * Outputs: 363 * Outputs code to the file. 364 * Assumptions: 365 * Chars are 8 bits long. 366 * Algorithm: 367 * Maintain a BITS character long buffer (so that 8 codes will 368 * fit in it exactly). Use the VAX insv instruction to insert each 369 * code in turn. When the buffer fills up empty it and start over. 370 */ 371 372 static char_type lmask[9] = 373 {0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80, 0x00}; 374 static char_type rmask[9] = 375 {0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff}; 376 377 static int 378 output(zs, ocode) 379 struct s_zstate *zs; 380 code_int ocode; 381 { 382 register int bits, r_off; 383 register char_type *bp; 384 385 r_off = offset; 386 bits = n_bits; 387 bp = buf; 388 if (ocode >= 0) { 389 /* Get to the first byte. */ 390 bp += (r_off >> 3); 391 r_off &= 7; 392 /* 393 * Since ocode is always >= 8 bits, only need to mask the first 394 * hunk on the left. 395 */ 396 *bp = (*bp & rmask[r_off]) | (ocode << r_off) & lmask[r_off]; 397 bp++; 398 bits -= (8 - r_off); 399 ocode >>= 8 - r_off; 400 /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */ 401 if (bits >= 8) { 402 *bp++ = ocode; 403 ocode >>= 8; 404 bits -= 8; 405 } 406 /* Last bits. */ 407 if (bits) 408 *bp = ocode; 409 offset += n_bits; 410 if (offset == (n_bits << 3)) { 411 bp = buf; 412 bits = n_bits; 413 bytes_out += bits; 414 if (fwrite(bp, sizeof(char), bits, fp) != bits) 415 return (-1); 416 bp += bits; 417 bits = 0; 418 offset = 0; 419 } 420 /* 421 * If the next entry is going to be too big for the ocode size, 422 * then increase it, if possible. 423 */ 424 if (free_ent > maxcode || (clear_flg > 0)) { 425 /* 426 * Write the whole buffer, because the input side won't 427 * discover the size increase until after it has read it. 428 */ 429 if (offset > 0) { 430 if (fwrite(buf, 1, n_bits, fp) != n_bits) 431 return (-1); 432 bytes_out += n_bits; 433 } 434 offset = 0; 435 436 if (clear_flg) { 437 maxcode = MAXCODE(n_bits = INIT_BITS); 438 clear_flg = 0; 439 } else { 440 n_bits++; 441 if (n_bits == maxbits) 442 maxcode = maxmaxcode; 443 else 444 maxcode = MAXCODE(n_bits); 445 } 446 } 447 } else { 448 /* At EOF, write the rest of the buffer. */ 449 if (offset > 0) { 450 offset = (offset + 7) / 8; 451 if (fwrite(buf, 1, offset, fp) != offset) 452 return (-1); 453 bytes_out += offset; 454 } 455 offset = 0; 456 } 457 return (0); 458 } 459 460 /* 461 * Decompress read. This routine adapts to the codes in the file building 462 * the "string" table on-the-fly; requiring no table to be stored in the 463 * compressed file. The tables used herein are shared with those of the 464 * compress() routine. See the definitions above. 465 */ 466 static int 467 zread(cookie, rbp, num) 468 void *cookie; 469 char *rbp; 470 int num; 471 { 472 register u_int count; 473 struct s_zstate *zs; 474 u_char *bp, header[3]; 475 476 if (num == 0) 477 return (0); 478 479 zs = cookie; 480 count = num; 481 bp = (u_char *)rbp; 482 switch (state) { 483 case S_START: 484 state = S_MIDDLE; 485 break; 486 case S_MIDDLE: 487 goto middle; 488 case S_EOF: 489 goto eof; 490 } 491 492 /* Check the magic number */ 493 if (fread(header, 494 sizeof(char), sizeof(header), fp) != sizeof(header) || 495 memcmp(header, magic_header, sizeof(magic_header)) != 0) { 496 errno = EFTYPE; 497 return (-1); 498 } 499 maxbits = header[2]; /* Set -b from file. */ 500 block_compress = maxbits & BLOCK_MASK; 501 maxbits &= BIT_MASK; 502 maxmaxcode = 1L << maxbits; 503 if (maxbits > BITS) { 504 errno = EFTYPE; 505 return (-1); 506 } 507 /* As above, initialize the first 256 entries in the table. */ 508 maxcode = MAXCODE(n_bits = INIT_BITS); 509 for (code = 255; code >= 0; code--) { 510 tab_prefixof(code) = 0; 511 tab_suffixof(code) = (char_type) code; 512 } 513 free_ent = block_compress ? FIRST : 256; 514 515 finchar = oldcode = getcode(zs); 516 if (oldcode == -1) /* EOF already? */ 517 return (0); /* Get out of here */ 518 519 /* First code must be 8 bits = char. */ 520 *bp++ = (u_char)finchar; 521 count--; 522 stackp = de_stack; 523 524 while ((code = getcode(zs)) > -1) { 525 526 if ((code == CLEAR) && block_compress) { 527 for (code = 255; code >= 0; code--) 528 tab_prefixof(code) = 0; 529 clear_flg = 1; 530 free_ent = FIRST - 1; 531 if ((code = getcode(zs)) == -1) /* O, untimely death! */ 532 break; 533 } 534 incode = code; 535 536 /* Special case for KwKwK string. */ 537 if (code >= free_ent) { 538 *stackp++ = finchar; 539 code = oldcode; 540 } 541 542 /* Generate output characters in reverse order. */ 543 while (code >= 256) { 544 *stackp++ = tab_suffixof(code); 545 code = tab_prefixof(code); 546 } 547 *stackp++ = finchar = tab_suffixof(code); 548 549 /* And put them out in forward order. */ 550 middle: do { 551 if (count-- == 0) 552 return (num); 553 *bp++ = *--stackp; 554 } while (stackp > de_stack); 555 556 /* Generate the new entry. */ 557 if ((code = free_ent) < maxmaxcode) { 558 tab_prefixof(code) = (u_short) oldcode; 559 tab_suffixof(code) = finchar; 560 free_ent = code + 1; 561 } 562 563 /* Remember previous code. */ 564 oldcode = incode; 565 } 566 state = S_EOF; 567 eof: return (num - count); 568 } 569 570 /*- 571 * Read one code from the standard input. If EOF, return -1. 572 * Inputs: 573 * stdin 574 * Outputs: 575 * code or -1 is returned. 576 */ 577 static code_int 578 getcode(zs) 579 struct s_zstate *zs; 580 { 581 register code_int gcode; 582 register int r_off, bits; 583 register char_type *bp; 584 585 bp = gbuf; 586 if (clear_flg > 0 || roffset >= size || free_ent > maxcode) { 587 /* 588 * If the next entry will be too big for the current gcode 589 * size, then we must increase the size. This implies reading 590 * a new buffer full, too. 591 */ 592 if (free_ent > maxcode) { 593 n_bits++; 594 if (n_bits == maxbits) /* Won't get any bigger now. */ 595 maxcode = maxmaxcode; 596 else 597 maxcode = MAXCODE(n_bits); 598 } 599 if (clear_flg > 0) { 600 maxcode = MAXCODE(n_bits = INIT_BITS); 601 clear_flg = 0; 602 } 603 size = fread(gbuf, 1, n_bits, fp); 604 if (size <= 0) /* End of file. */ 605 return (-1); 606 roffset = 0; 607 /* Round size down to integral number of codes. */ 608 size = (size << 3) - (n_bits - 1); 609 } 610 r_off = roffset; 611 bits = n_bits; 612 613 /* Get to the first byte. */ 614 bp += (r_off >> 3); 615 r_off &= 7; 616 617 /* Get first part (low order bits). */ 618 gcode = (*bp++ >> r_off); 619 bits -= (8 - r_off); 620 r_off = 8 - r_off; /* Now, roffset into gcode word. */ 621 622 /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */ 623 if (bits >= 8) { 624 gcode |= *bp++ << r_off; 625 r_off += 8; 626 bits -= 8; 627 } 628 629 /* High order bits. */ 630 gcode |= (*bp & rmask[bits]) << r_off; 631 roffset += n_bits; 632 633 return (gcode); 634 } 635 636 static int 637 cl_block(zs) /* Table clear for block compress. */ 638 struct s_zstate *zs; 639 { 640 register long rat; 641 642 checkpoint = in_count + CHECK_GAP; 643 644 if (in_count > 0x007fffff) { /* Shift will overflow. */ 645 rat = bytes_out >> 8; 646 if (rat == 0) /* Don't divide by zero. */ 647 rat = 0x7fffffff; 648 else 649 rat = in_count / rat; 650 } else 651 rat = (in_count << 8) / bytes_out; /* 8 fractional bits. */ 652 if (rat > ratio) 653 ratio = rat; 654 else { 655 ratio = 0; 656 cl_hash(zs, (count_int) hsize); 657 free_ent = FIRST; 658 clear_flg = 1; 659 if (output(zs, (code_int) CLEAR) == -1) 660 return (-1); 661 } 662 return (0); 663 } 664 665 static void 666 cl_hash(zs, cl_hsize) /* Reset code table. */ 667 struct s_zstate *zs; 668 register count_int cl_hsize; 669 { 670 register count_int *htab_p; 671 register long i, m1; 672 673 m1 = -1; 674 htab_p = htab + cl_hsize; 675 i = cl_hsize - 16; 676 do { /* Might use Sys V memset(3) here. */ 677 *(htab_p - 16) = m1; 678 *(htab_p - 15) = m1; 679 *(htab_p - 14) = m1; 680 *(htab_p - 13) = m1; 681 *(htab_p - 12) = m1; 682 *(htab_p - 11) = m1; 683 *(htab_p - 10) = m1; 684 *(htab_p - 9) = m1; 685 *(htab_p - 8) = m1; 686 *(htab_p - 7) = m1; 687 *(htab_p - 6) = m1; 688 *(htab_p - 5) = m1; 689 *(htab_p - 4) = m1; 690 *(htab_p - 3) = m1; 691 *(htab_p - 2) = m1; 692 *(htab_p - 1) = m1; 693 htab_p -= 16; 694 } while ((i -= 16) >= 0); 695 for (i += 16; i > 0; i--) 696 *--htab_p = m1; 697 } 698 699 FILE * 700 zopen(fname, mode, bits) 701 const char *fname, *mode; 702 int bits; 703 { 704 struct s_zstate *zs; 705 706 if (mode[0] != 'r' && mode[0] != 'w' || mode[1] != '\0' || 707 bits < 0 || bits > BITS) { 708 errno = EINVAL; 709 return (NULL); 710 } 711 712 if ((zs = calloc(1, sizeof(struct s_zstate))) == NULL) 713 return (NULL); 714 715 maxbits = bits ? bits : BITS; /* User settable max # bits/code. */ 716 maxmaxcode = 1 << maxbits; /* Should NEVER generate this code. */ 717 hsize = HSIZE; /* For dynamic table sizing. */ 718 free_ent = 0; /* First unused entry. */ 719 block_compress = BLOCK_MASK; 720 clear_flg = 0; 721 ratio = 0; 722 checkpoint = CHECK_GAP; 723 in_count = 1; /* Length of input. */ 724 out_count = 0; /* # of codes output (for debugging). */ 725 state = S_START; 726 roffset = 0; 727 size = 0; 728 729 /* 730 * Layering compress on top of stdio in order to provide buffering, 731 * and ensure that reads and write work with the data specified. 732 */ 733 if ((fp = fopen(fname, mode)) == NULL) { 734 free(zs); 735 return (NULL); 736 } 737 switch (*mode) { 738 case 'r': 739 zmode = 'r'; 740 return (funopen(zs, zread, NULL, NULL, zclose)); 741 case 'w': 742 zmode = 'w'; 743 return (funopen(zs, NULL, zwrite, NULL, zclose)); 744 } 745 /* NOTREACHED */ 746 } 747