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. */
76 typedef long code_int;
77 typedef long count_int;
78
79 typedef u_char char_type;
80 static 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
94 struct 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
197 static int cl_block(struct s_zstate *);
198 static void cl_hash(struct s_zstate *, count_int);
199 static code_int getcode(struct s_zstate *);
200 static int output(struct s_zstate *, code_int);
201 static int zclose(void *);
202 static int zread(void *, char *, int);
203 static 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 */
231 static int
zwrite(void * cookie,const char * wbp,int num)232 zwrite(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
280 middle: 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;
294 probe: 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;
303 nomatch: 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
319 static int
zclose(void * cookie)320 zclose(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
359 static char_type lmask[9] =
360 {0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80, 0x00};
361 static char_type rmask[9] =
362 {0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff};
363
364 static int
output(struct s_zstate * zs,code_int ocode)365 output(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 */
452 static int
zread(void * cookie,char * rbp,int num)453 zread(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. */
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 && 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;
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
getcode(struct s_zstate * zs)572 getcode(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 if (bits > 0)
624 gcode |= (*bp & rmask[bits]) << r_off;
625 roffset += n_bits;
626
627 return (gcode);
628 }
629
630 static int
cl_block(struct s_zstate * zs)631 cl_block(struct s_zstate *zs) /* Table clear for block compress. */
632 {
633 long rat;
634
635 checkpoint = in_count + CHECK_GAP;
636
637 if (in_count > 0x007fffff) { /* Shift will overflow. */
638 rat = bytes_out >> 8;
639 if (rat == 0) /* Don't divide by zero. */
640 rat = 0x7fffffff;
641 else
642 rat = in_count / rat;
643 } else
644 rat = (in_count << 8) / bytes_out; /* 8 fractional bits. */
645 if (rat > ratio)
646 ratio = rat;
647 else {
648 ratio = 0;
649 cl_hash(zs, (count_int) hsize);
650 free_ent = FIRST;
651 clear_flg = 1;
652 if (output(zs, (code_int) CLEAR) == -1)
653 return (-1);
654 }
655 return (0);
656 }
657
658 static void
cl_hash(struct s_zstate * zs,count_int cl_hsize)659 cl_hash(struct s_zstate *zs, count_int cl_hsize) /* Reset code table. */
660 {
661 count_int *htab_p;
662 long i, m1;
663
664 m1 = -1;
665 htab_p = htab + cl_hsize;
666 i = cl_hsize - 16;
667 do { /* Might use Sys V memset(3) here. */
668 *(htab_p - 16) = m1;
669 *(htab_p - 15) = m1;
670 *(htab_p - 14) = m1;
671 *(htab_p - 13) = m1;
672 *(htab_p - 12) = m1;
673 *(htab_p - 11) = m1;
674 *(htab_p - 10) = m1;
675 *(htab_p - 9) = m1;
676 *(htab_p - 8) = m1;
677 *(htab_p - 7) = m1;
678 *(htab_p - 6) = m1;
679 *(htab_p - 5) = m1;
680 *(htab_p - 4) = m1;
681 *(htab_p - 3) = m1;
682 *(htab_p - 2) = m1;
683 *(htab_p - 1) = m1;
684 htab_p -= 16;
685 } while ((i -= 16) >= 0);
686 for (i += 16; i > 0; i--)
687 *--htab_p = m1;
688 }
689
690 FILE *
zopen(const char * fname,const char * mode,int bits)691 zopen(const char *fname, const char *mode, int bits)
692 {
693 struct s_zstate *zs;
694
695 if ((mode[0] != 'r' && mode[0] != 'w') || mode[1] != '\0' ||
696 bits < 0 || bits > BITS) {
697 errno = EINVAL;
698 return (NULL);
699 }
700
701 if ((zs = calloc(1, sizeof(struct s_zstate))) == NULL)
702 return (NULL);
703
704 maxbits = bits ? bits : BITS; /* User settable max # bits/code. */
705 maxmaxcode = 1L << maxbits; /* Should NEVER generate this code. */
706 hsize = HSIZE; /* For dynamic table sizing. */
707 free_ent = 0; /* First unused entry. */
708 block_compress = BLOCK_MASK;
709 clear_flg = 0;
710 ratio = 0;
711 checkpoint = CHECK_GAP;
712 in_count = 1; /* Length of input. */
713 out_count = 0; /* # of codes output (for debugging). */
714 state = S_START;
715 roffset = 0;
716 size = 0;
717
718 /*
719 * Layering compress on top of stdio in order to provide buffering,
720 * and ensure that reads and write work with the data specified.
721 */
722 if ((fp = fopen(fname, mode)) == NULL) {
723 free(zs);
724 return (NULL);
725 }
726 switch (*mode) {
727 case 'r':
728 zmode = 'r';
729 return (funopen(zs, zread, NULL, NULL, zclose));
730 case 'w':
731 zmode = 'w';
732 return (funopen(zs, NULL, zwrite, NULL, zclose));
733 }
734 /* NOTREACHED */
735 return (NULL);
736 }
737