Annotation of src/usr.bin/compress/zopen.c, Revision 1.2
1.2 ! deraadt 1: /* $OpenBSD: zopen.c,v 1.5 1995/03/26 09:44:53 glass Exp $ */
1.1 deraadt 2: /* $NetBSD: zopen.c,v 1.5 1995/03/26 09:44:53 glass Exp $ */
3:
4: /*-
5: * Copyright (c) 1985, 1986, 1992, 1993
6: * The Regents of the University of California. All rights reserved.
7: *
8: * This code is derived from software contributed to Berkeley by
9: * Diomidis Spinellis and James A. Woods, derived from original
10: * work by Spencer Thomas and Joseph Orost.
11: *
12: * Redistribution and use in source and binary forms, with or without
13: * modification, are permitted provided that the following conditions
14: * are met:
15: * 1. Redistributions of source code must retain the above copyright
16: * notice, this list of conditions and the following disclaimer.
17: * 2. Redistributions in binary form must reproduce the above copyright
18: * notice, this list of conditions and the following disclaimer in the
19: * documentation and/or other materials provided with the distribution.
20: * 3. All advertising materials mentioning features or use of this software
21: * must display the following acknowledgement:
22: * This product includes software developed by the University of
23: * California, Berkeley and its contributors.
24: * 4. Neither the name of the University nor the names of its contributors
25: * may be used to endorse or promote products derived from this software
26: * without specific prior written permission.
27: *
28: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38: * SUCH DAMAGE.
39: */
40:
41: #if defined(LIBC_SCCS) && !defined(lint)
42: #if 0
43: static char sccsid[] = "@(#)zopen.c 8.1 (Berkeley) 6/27/93";
44: #else
1.2 ! deraadt 45: static char rcsid[] = "$OpenBSD: zopen.c,v 1.5 1995/03/26 09:44:53 glass Exp $";
1.1 deraadt 46: #endif
47: #endif /* LIBC_SCCS and not lint */
48:
49: /*-
50: * fcompress.c - File compression ala IEEE Computer, June 1984.
51: *
52: * Compress authors:
53: * Spencer W. Thomas (decvax!utah-cs!thomas)
54: * Jim McKie (decvax!mcvax!jim)
55: * Steve Davies (decvax!vax135!petsd!peora!srd)
56: * Ken Turkowski (decvax!decwrl!turtlevax!ken)
57: * James A. Woods (decvax!ihnp4!ames!jaw)
58: * Joe Orost (decvax!vax135!petsd!joe)
59: *
60: * Cleaned up and converted to library returning I/O streams by
61: * Diomidis Spinellis <dds@doc.ic.ac.uk>.
62: *
63: * zopen(filename, mode, bits)
64: * Returns a FILE * that can be used for read or write. The modes
65: * supported are only "r" and "w". Seeking is not allowed. On
66: * reading the file is decompressed, on writing it is compressed.
67: * The output is compatible with compress(1) with 16 bit tables.
68: * Any file produced by compress(1) can be read.
69: */
70:
71: #include <sys/param.h>
72: #include <sys/stat.h>
73:
74: #include <ctype.h>
75: #include <errno.h>
76: #include <signal.h>
77: #include <stdio.h>
78: #include <stdlib.h>
79: #include <string.h>
80: #include <unistd.h>
81:
82: #define BITS 16 /* Default bits. */
83: #define HSIZE 69001 /* 95% occupancy */
84:
85: /* A code_int must be able to hold 2**BITS values of type int, and also -1. */
86: typedef long code_int;
87: typedef long count_int;
88:
89: typedef u_char char_type;
90: static char_type magic_header[] =
91: {'\037', '\235'}; /* 1F 9D */
92:
93: #define BIT_MASK 0x1f /* Defines for third byte of header. */
94: #define BLOCK_MASK 0x80
95:
96: /*
97: * Masks 0x40 and 0x20 are free. I think 0x20 should mean that there is
98: * a fourth header byte (for expansion).
99: */
100: #define INIT_BITS 9 /* Initial number of bits/code. */
101:
102: #define MAXCODE(n_bits) ((1 << (n_bits)) - 1)
103:
104: struct s_zstate {
105: FILE *zs_fp; /* File stream for I/O */
106: char zs_mode; /* r or w */
107: enum {
108: S_START, S_MIDDLE, S_EOF
109: } zs_state; /* State of computation */
110: int zs_n_bits; /* Number of bits/code. */
111: int zs_maxbits; /* User settable max # bits/code. */
112: code_int zs_maxcode; /* Maximum code, given n_bits. */
113: code_int zs_maxmaxcode; /* Should NEVER generate this code. */
114: count_int zs_htab [HSIZE];
115: u_short zs_codetab [HSIZE];
116: code_int zs_hsize; /* For dynamic table sizing. */
117: code_int zs_free_ent; /* First unused entry. */
118: /*
119: * Block compression parameters -- after all codes are used up,
120: * and compression rate changes, start over.
121: */
122: int zs_block_compress;
123: int zs_clear_flg;
124: long zs_ratio;
125: count_int zs_checkpoint;
126: int zs_offset;
127: long zs_in_count; /* Length of input. */
128: long zs_bytes_out; /* Length of compressed output. */
129: long zs_out_count; /* # of codes output (for debugging). */
130: char_type zs_buf[BITS];
131: union {
132: struct {
133: long zs_fcode;
134: code_int zs_ent;
135: code_int zs_hsize_reg;
136: int zs_hshift;
137: } w; /* Write paramenters */
138: struct {
139: char_type *zs_stackp;
140: int zs_finchar;
141: code_int zs_code, zs_oldcode, zs_incode;
142: int zs_roffset, zs_size;
143: char_type zs_gbuf[BITS];
144: } r; /* Read parameters */
145: } u;
146: };
147:
148: /* Definitions to retain old variable names */
149: #define fp zs->zs_fp
150: #define zmode zs->zs_mode
151: #define state zs->zs_state
152: #define n_bits zs->zs_n_bits
153: #define maxbits zs->zs_maxbits
154: #define maxcode zs->zs_maxcode
155: #define maxmaxcode zs->zs_maxmaxcode
156: #define htab zs->zs_htab
157: #define codetab zs->zs_codetab
158: #define hsize zs->zs_hsize
159: #define free_ent zs->zs_free_ent
160: #define block_compress zs->zs_block_compress
161: #define clear_flg zs->zs_clear_flg
162: #define ratio zs->zs_ratio
163: #define checkpoint zs->zs_checkpoint
164: #define offset zs->zs_offset
165: #define in_count zs->zs_in_count
166: #define bytes_out zs->zs_bytes_out
167: #define out_count zs->zs_out_count
168: #define buf zs->zs_buf
169: #define fcode zs->u.w.zs_fcode
170: #define hsize_reg zs->u.w.zs_hsize_reg
171: #define ent zs->u.w.zs_ent
172: #define hshift zs->u.w.zs_hshift
173: #define stackp zs->u.r.zs_stackp
174: #define finchar zs->u.r.zs_finchar
175: #define code zs->u.r.zs_code
176: #define oldcode zs->u.r.zs_oldcode
177: #define incode zs->u.r.zs_incode
178: #define roffset zs->u.r.zs_roffset
179: #define size zs->u.r.zs_size
180: #define gbuf zs->u.r.zs_gbuf
181:
182: /*
183: * To save much memory, we overlay the table used by compress() with those
184: * used by decompress(). The tab_prefix table is the same size and type as
185: * the codetab. The tab_suffix table needs 2**BITS characters. We get this
186: * from the beginning of htab. The output stack uses the rest of htab, and
187: * contains characters. There is plenty of room for any possible stack
188: * (stack used to be 8000 characters).
189: */
190:
191: #define htabof(i) htab[i]
192: #define codetabof(i) codetab[i]
193:
194: #define tab_prefixof(i) codetabof(i)
195: #define tab_suffixof(i) ((char_type *)(htab))[i]
196: #define de_stack ((char_type *)&tab_suffixof(1 << BITS))
197:
198: #define CHECK_GAP 10000 /* Ratio check interval. */
199:
200: /*
201: * the next two codes should not be changed lightly, as they must not
202: * lie within the contiguous general code space.
203: */
204: #define FIRST 257 /* First free entry. */
205: #define CLEAR 256 /* Table clear output code. */
206:
207: static int cl_block __P((struct s_zstate *));
208: static void cl_hash __P((struct s_zstate *, count_int));
209: static code_int getcode __P((struct s_zstate *));
210: static int output __P((struct s_zstate *, code_int));
211: static int zclose __P((void *));
212: static int zread __P((void *, char *, int));
213: static int zwrite __P((void *, const char *, int));
214:
215: /*-
216: * Algorithm from "A Technique for High Performance Data Compression",
217: * Terry A. Welch, IEEE Computer Vol 17, No 6 (June 1984), pp 8-19.
218: *
219: * Algorithm:
220: * Modified Lempel-Ziv method (LZW). Basically finds common
221: * substrings and replaces them with a variable size code. This is
222: * deterministic, and can be done on the fly. Thus, the decompression
223: * procedure needs no input table, but tracks the way the table was built.
224: */
225:
226: /*-
227: * compress write
228: *
229: * Algorithm: use open addressing double hashing (no chaining) on the
230: * prefix code / next character combination. We do a variant of Knuth's
231: * algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime
232: * secondary probe. Here, the modular division first probe is gives way
233: * to a faster exclusive-or manipulation. Also do block compression with
234: * an adaptive reset, whereby the code table is cleared when the compression
235: * ratio decreases, but after the table fills. The variable-length output
236: * codes are re-sized at this point, and a special CLEAR code is generated
237: * for the decompressor. Late addition: construct the table according to
238: * file size for noticeable speed improvement on small files. Please direct
239: * questions about this implementation to ames!jaw.
240: */
241: static int
242: zwrite(cookie, wbp, num)
243: void *cookie;
244: const char *wbp;
245: int num;
246: {
247: register code_int i;
248: register int c, disp;
249: struct s_zstate *zs;
250: const u_char *bp;
251: u_char tmp;
252: int count;
253:
254: if (num == 0)
255: return (0);
256:
257: zs = cookie;
258: count = num;
259: bp = (u_char *)wbp;
260: if (state == S_MIDDLE)
261: goto middle;
262: state = S_MIDDLE;
263:
264: maxmaxcode = 1L << maxbits;
265: if (fwrite(magic_header,
266: sizeof(char), sizeof(magic_header), fp) != sizeof(magic_header))
267: return (-1);
268: tmp = (u_char)(maxbits | block_compress);
269: if (fwrite(&tmp, sizeof(char), sizeof(tmp), fp) != sizeof(tmp))
270: return (-1);
271:
272: offset = 0;
273: bytes_out = 3; /* Includes 3-byte header mojo. */
274: out_count = 0;
275: clear_flg = 0;
276: ratio = 0;
277: in_count = 1;
278: checkpoint = CHECK_GAP;
279: maxcode = MAXCODE(n_bits = INIT_BITS);
280: free_ent = ((block_compress) ? FIRST : 256);
281:
282: ent = *bp++;
283: --count;
284:
285: hshift = 0;
286: for (fcode = (long)hsize; fcode < 65536L; fcode *= 2L)
287: hshift++;
288: hshift = 8 - hshift; /* Set hash code range bound. */
289:
290: hsize_reg = hsize;
291: cl_hash(zs, (count_int)hsize_reg); /* Clear hash table. */
292:
293: middle: for (i = 0; count--;) {
294: c = *bp++;
295: in_count++;
296: fcode = (long)(((long)c << maxbits) + ent);
297: i = ((c << hshift) ^ ent); /* Xor hashing. */
298:
299: if (htabof(i) == fcode) {
300: ent = codetabof(i);
301: continue;
302: } else if ((long)htabof(i) < 0) /* Empty slot. */
303: goto nomatch;
304: disp = hsize_reg - i; /* Secondary hash (after G. Knott). */
305: if (i == 0)
306: disp = 1;
307: probe: if ((i -= disp) < 0)
308: i += hsize_reg;
309:
310: if (htabof(i) == fcode) {
311: ent = codetabof(i);
312: continue;
313: }
314: if ((long)htabof(i) >= 0)
315: goto probe;
316: nomatch: if (output(zs, (code_int) ent) == -1)
317: return (-1);
318: out_count++;
319: ent = c;
320: if (free_ent < maxmaxcode) {
321: codetabof(i) = free_ent++; /* code -> hashtable */
322: htabof(i) = fcode;
323: } else if ((count_int)in_count >=
324: checkpoint && block_compress) {
325: if (cl_block(zs) == -1)
326: return (-1);
327: }
328: }
329: return (num);
330: }
331:
332: static int
333: zclose(cookie)
334: void *cookie;
335: {
336: struct s_zstate *zs;
337: int rval;
338:
339: zs = cookie;
340: if (zmode == 'w') { /* Put out the final code. */
341: if (output(zs, (code_int) ent) == -1) {
342: (void)fclose(fp);
343: free(zs);
344: return (-1);
345: }
346: out_count++;
347: if (output(zs, (code_int) - 1) == -1) {
348: (void)fclose(fp);
349: free(zs);
350: return (-1);
351: }
352: }
353: rval = fclose(fp) == EOF ? -1 : 0;
354: free(zs);
355: return (rval);
356: }
357:
358: /*-
359: * Output the given code.
360: * Inputs:
361: * code: A n_bits-bit integer. If == -1, then EOF. This assumes
362: * that n_bits =< (long)wordsize - 1.
363: * Outputs:
364: * Outputs code to the file.
365: * Assumptions:
366: * Chars are 8 bits long.
367: * Algorithm:
368: * Maintain a BITS character long buffer (so that 8 codes will
369: * fit in it exactly). Use the VAX insv instruction to insert each
370: * code in turn. When the buffer fills up empty it and start over.
371: */
372:
373: static char_type lmask[9] =
374: {0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80, 0x00};
375: static char_type rmask[9] =
376: {0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff};
377:
378: static int
379: output(zs, ocode)
380: struct s_zstate *zs;
381: code_int ocode;
382: {
383: register int bits, r_off;
384: register char_type *bp;
385:
386: r_off = offset;
387: bits = n_bits;
388: bp = buf;
389: if (ocode >= 0) {
390: /* Get to the first byte. */
391: bp += (r_off >> 3);
392: r_off &= 7;
393: /*
394: * Since ocode is always >= 8 bits, only need to mask the first
395: * hunk on the left.
396: */
397: *bp = (*bp & rmask[r_off]) | (ocode << r_off) & lmask[r_off];
398: bp++;
399: bits -= (8 - r_off);
400: ocode >>= 8 - r_off;
401: /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */
402: if (bits >= 8) {
403: *bp++ = ocode;
404: ocode >>= 8;
405: bits -= 8;
406: }
407: /* Last bits. */
408: if (bits)
409: *bp = ocode;
410: offset += n_bits;
411: if (offset == (n_bits << 3)) {
412: bp = buf;
413: bits = n_bits;
414: bytes_out += bits;
415: if (fwrite(bp, sizeof(char), bits, fp) != bits)
416: return (-1);
417: bp += bits;
418: bits = 0;
419: offset = 0;
420: }
421: /*
422: * If the next entry is going to be too big for the ocode size,
423: * then increase it, if possible.
424: */
425: if (free_ent > maxcode || (clear_flg > 0)) {
426: /*
427: * Write the whole buffer, because the input side won't
428: * discover the size increase until after it has read it.
429: */
430: if (offset > 0) {
431: if (fwrite(buf, 1, n_bits, fp) != n_bits)
432: return (-1);
433: bytes_out += n_bits;
434: }
435: offset = 0;
436:
437: if (clear_flg) {
438: maxcode = MAXCODE(n_bits = INIT_BITS);
439: clear_flg = 0;
440: } else {
441: n_bits++;
442: if (n_bits == maxbits)
443: maxcode = maxmaxcode;
444: else
445: maxcode = MAXCODE(n_bits);
446: }
447: }
448: } else {
449: /* At EOF, write the rest of the buffer. */
450: if (offset > 0) {
451: offset = (offset + 7) / 8;
452: if (fwrite(buf, 1, offset, fp) != offset)
453: return (-1);
454: bytes_out += offset;
455: }
456: offset = 0;
457: }
458: return (0);
459: }
460:
461: /*
462: * Decompress read. This routine adapts to the codes in the file building
463: * the "string" table on-the-fly; requiring no table to be stored in the
464: * compressed file. The tables used herein are shared with those of the
465: * compress() routine. See the definitions above.
466: */
467: static int
468: zread(cookie, rbp, num)
469: void *cookie;
470: char *rbp;
471: int num;
472: {
473: register u_int count;
474: struct s_zstate *zs;
475: u_char *bp, header[3];
476:
477: if (num == 0)
478: return (0);
479:
480: zs = cookie;
481: count = num;
482: bp = (u_char *)rbp;
483: switch (state) {
484: case S_START:
485: state = S_MIDDLE;
486: break;
487: case S_MIDDLE:
488: goto middle;
489: case S_EOF:
490: goto eof;
491: }
492:
493: /* Check the magic number */
494: if (fread(header,
495: sizeof(char), sizeof(header), fp) != sizeof(header) ||
496: memcmp(header, magic_header, sizeof(magic_header)) != 0) {
497: errno = EFTYPE;
498: return (-1);
499: }
500: maxbits = header[2]; /* Set -b from file. */
501: block_compress = maxbits & BLOCK_MASK;
502: maxbits &= BIT_MASK;
503: maxmaxcode = 1L << maxbits;
504: if (maxbits > BITS) {
505: errno = EFTYPE;
506: return (-1);
507: }
508: /* As above, initialize the first 256 entries in the table. */
509: maxcode = MAXCODE(n_bits = INIT_BITS);
510: for (code = 255; code >= 0; code--) {
511: tab_prefixof(code) = 0;
512: tab_suffixof(code) = (char_type) code;
513: }
514: free_ent = block_compress ? FIRST : 256;
515:
516: finchar = oldcode = getcode(zs);
517: if (oldcode == -1) /* EOF already? */
518: return (0); /* Get out of here */
519:
520: /* First code must be 8 bits = char. */
521: *bp++ = (u_char)finchar;
522: count--;
523: stackp = de_stack;
524:
525: while ((code = getcode(zs)) > -1) {
526:
527: if ((code == CLEAR) && block_compress) {
528: for (code = 255; code >= 0; code--)
529: tab_prefixof(code) = 0;
530: clear_flg = 1;
531: free_ent = FIRST - 1;
532: if ((code = getcode(zs)) == -1) /* O, untimely death! */
533: break;
534: }
535: incode = code;
536:
537: /* Special case for KwKwK string. */
538: if (code >= free_ent) {
539: *stackp++ = finchar;
540: code = oldcode;
541: }
542:
543: /* Generate output characters in reverse order. */
544: while (code >= 256) {
545: *stackp++ = tab_suffixof(code);
546: code = tab_prefixof(code);
547: }
548: *stackp++ = finchar = tab_suffixof(code);
549:
550: /* And put them out in forward order. */
551: middle: do {
552: if (count-- == 0)
553: return (num);
554: *bp++ = *--stackp;
555: } while (stackp > de_stack);
556:
557: /* Generate the new entry. */
558: if ((code = free_ent) < maxmaxcode) {
559: tab_prefixof(code) = (u_short) oldcode;
560: tab_suffixof(code) = finchar;
561: free_ent = code + 1;
562: }
563:
564: /* Remember previous code. */
565: oldcode = incode;
566: }
567: state = S_EOF;
568: eof: return (num - count);
569: }
570:
571: /*-
572: * Read one code from the standard input. If EOF, return -1.
573: * Inputs:
574: * stdin
575: * Outputs:
576: * code or -1 is returned.
577: */
578: static code_int
579: getcode(zs)
580: struct s_zstate *zs;
581: {
582: register code_int gcode;
583: register int r_off, bits;
584: register char_type *bp;
585:
586: bp = gbuf;
587: if (clear_flg > 0 || roffset >= size || free_ent > maxcode) {
588: /*
589: * If the next entry will be too big for the current gcode
590: * size, then we must increase the size. This implies reading
591: * a new buffer full, too.
592: */
593: if (free_ent > maxcode) {
594: n_bits++;
595: if (n_bits == maxbits) /* Won't get any bigger now. */
596: maxcode = maxmaxcode;
597: else
598: maxcode = MAXCODE(n_bits);
599: }
600: if (clear_flg > 0) {
601: maxcode = MAXCODE(n_bits = INIT_BITS);
602: clear_flg = 0;
603: }
604: size = fread(gbuf, 1, n_bits, fp);
605: if (size <= 0) /* End of file. */
606: return (-1);
607: roffset = 0;
608: /* Round size down to integral number of codes. */
609: size = (size << 3) - (n_bits - 1);
610: }
611: r_off = roffset;
612: bits = n_bits;
613:
614: /* Get to the first byte. */
615: bp += (r_off >> 3);
616: r_off &= 7;
617:
618: /* Get first part (low order bits). */
619: gcode = (*bp++ >> r_off);
620: bits -= (8 - r_off);
621: r_off = 8 - r_off; /* Now, roffset into gcode word. */
622:
623: /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */
624: if (bits >= 8) {
625: gcode |= *bp++ << r_off;
626: r_off += 8;
627: bits -= 8;
628: }
629:
630: /* High order bits. */
631: gcode |= (*bp & rmask[bits]) << r_off;
632: roffset += n_bits;
633:
634: return (gcode);
635: }
636:
637: static int
638: cl_block(zs) /* Table clear for block compress. */
639: struct s_zstate *zs;
640: {
641: register long rat;
642:
643: checkpoint = in_count + CHECK_GAP;
644:
645: if (in_count > 0x007fffff) { /* Shift will overflow. */
646: rat = bytes_out >> 8;
647: if (rat == 0) /* Don't divide by zero. */
648: rat = 0x7fffffff;
649: else
650: rat = in_count / rat;
651: } else
652: rat = (in_count << 8) / bytes_out; /* 8 fractional bits. */
653: if (rat > ratio)
654: ratio = rat;
655: else {
656: ratio = 0;
657: cl_hash(zs, (count_int) hsize);
658: free_ent = FIRST;
659: clear_flg = 1;
660: if (output(zs, (code_int) CLEAR) == -1)
661: return (-1);
662: }
663: return (0);
664: }
665:
666: static void
667: cl_hash(zs, cl_hsize) /* Reset code table. */
668: struct s_zstate *zs;
669: register count_int cl_hsize;
670: {
671: register count_int *htab_p;
672: register long i, m1;
673:
674: m1 = -1;
675: htab_p = htab + cl_hsize;
676: i = cl_hsize - 16;
677: do { /* Might use Sys V memset(3) here. */
678: *(htab_p - 16) = m1;
679: *(htab_p - 15) = m1;
680: *(htab_p - 14) = m1;
681: *(htab_p - 13) = m1;
682: *(htab_p - 12) = m1;
683: *(htab_p - 11) = m1;
684: *(htab_p - 10) = m1;
685: *(htab_p - 9) = m1;
686: *(htab_p - 8) = m1;
687: *(htab_p - 7) = m1;
688: *(htab_p - 6) = m1;
689: *(htab_p - 5) = m1;
690: *(htab_p - 4) = m1;
691: *(htab_p - 3) = m1;
692: *(htab_p - 2) = m1;
693: *(htab_p - 1) = m1;
694: htab_p -= 16;
695: } while ((i -= 16) >= 0);
696: for (i += 16; i > 0; i--)
697: *--htab_p = m1;
698: }
699:
700: FILE *
701: zopen(fname, mode, bits)
702: const char *fname, *mode;
703: int bits;
704: {
705: struct s_zstate *zs;
706:
707: if (mode[0] != 'r' && mode[0] != 'w' || mode[1] != '\0' ||
708: bits < 0 || bits > BITS) {
709: errno = EINVAL;
710: return (NULL);
711: }
712:
713: if ((zs = calloc(1, sizeof(struct s_zstate))) == NULL)
714: return (NULL);
715:
716: maxbits = bits ? bits : BITS; /* User settable max # bits/code. */
717: maxmaxcode = 1 << maxbits; /* Should NEVER generate this code. */
718: hsize = HSIZE; /* For dynamic table sizing. */
719: free_ent = 0; /* First unused entry. */
720: block_compress = BLOCK_MASK;
721: clear_flg = 0;
722: ratio = 0;
723: checkpoint = CHECK_GAP;
724: in_count = 1; /* Length of input. */
725: out_count = 0; /* # of codes output (for debugging). */
726: state = S_START;
727: roffset = 0;
728: size = 0;
729:
730: /*
731: * Layering compress on top of stdio in order to provide buffering,
732: * and ensure that reads and write work with the data specified.
733: */
734: if ((fp = fopen(fname, mode)) == NULL) {
735: free(zs);
736: return (NULL);
737: }
738: switch (*mode) {
739: case 'r':
740: zmode = 'r';
741: return (funopen(zs, zread, NULL, NULL, zclose));
742: case 'w':
743: zmode = 'w';
744: return (funopen(zs, NULL, zwrite, NULL, zclose));
745: }
746: /* NOTREACHED */
747: }
![[BACK]](/icons/back.gif){kind=icon}
Return to zopen.c CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / compress