1 /*
2  * compress - File compression ala IEEE Computer, June 1984.
3  *
4  * Algorithm from "A Technique for High Performance Data Compression",
5  * Terry A. Welch, IEEE Computer Vol 17, No 6 (June 1984), pp 8-19.
6  *
7  * Usage: compress [-dfvc] [-b bits] [file ...]
8  * Inputs:
9  *	-b:	limit the max number of bits/code.
10  *	-c:	write output on stdout, don't remove original.
11  *	-d:	decompress instead.
12  *	-f:	Forces output file to be generated, even if one already
13  *		exists, and even if no space is saved by compressing.
14  *		If -f is not used, the user will be prompted if stdin is
15  *		a tty, otherwise, the output file will not be overwritten.
16  *	-v:	Write compression statistics
17  *
18  * 	file ...: Files to be compressed.  If none specified, stdin is used.
19  * Outputs:
20  *	file.Z:	Compressed form of file with same mode, owner, and utimes
21  * 		or stdout (if stdin used as input)
22  *
23  * Assumptions:
24  *	When filenames are given, replaces with the compressed version
25  *	(.Z suffix) only if the file decreases in size.
26  * Algorithm:
27  * 	Modified Lempel-Ziv method (LZW).  Basically finds common
28  * substrings and replaces them with a variable size code.  This is
29  * deterministic, and can be done on the fly.  Thus, the decompression
30  * procedure needs no input table, but tracks the way the table was built.
31 
32  * Authors:	Spencer W. Thomas	(decvax!harpo!utah-cs!utah-gr!thomas)
33  *		Jim McKie		(decvax!mcvax!jim)
34  *		Steve Davies		(decvax!vax135!petsd!peora!srd)
35  *		Ken Turkowski		(decvax!decwrl!turtlevax!ken)
36  *		James A. Woods		(decvax!ihnp4!ames!jaw)
37  *		Joe Orost		(decvax!vax135!petsd!joe)
38  */
39 
40 #ifndef USED
41 #  define USED(x) if(x);else
42 #endif
43 
44 #define _PLAN9_SOURCE
45 #define _BSD_EXTENSION
46 #define _POSIX_SOURCE
47 
48 #include <u.h>
49 #include <stdio.h>
50 #include <ctype.h>
51 #include <stdlib.h>
52 #include <unistd.h>
53 #include <string.h>
54 #include <signal.h>
55 #include <utime.h>
56 #include <sys/types.h>
57 #include <sys/stat.h>
58 
59 #define	min(a,b)	((a>b) ? b : a)
60 
61 #define BITS	16
62 #define HSIZE	69001		/* 95% occupancy */
63 
64 /*
65  * a code_int must be able to hold 2**BITS values of type int, and also -1
66  */
67 typedef long	code_int;
68 typedef long	count_int;
69 
70 static char rcs_ident[] = "$Header: compress.c,v 4.0 85/07/30 12:50:00 joe Release $";
71 
72 uchar magic_header[] = { 0x1F, 0x9D };	/* 1F 9D */
73 
74 /* Defines for third byte of header */
75 #define BIT_MASK	0x1f
76 #define BLOCK_MASK	0x80
77 /* Masks 0x40 and 0x20 are free.  I think 0x20 should mean that there is
78 	a fourth header byte (for expansion).
79 */
80 #define INIT_BITS 9			/* initial number of bits/code */
81 
82 #define ARGVAL() (*++(*argv) || (--argc && *++argv))
83 
84 int n_bits;				/* number of bits/code */
85 int maxbits = BITS;			/* user settable max # bits/code */
86 code_int maxcode;			/* maximum code, given n_bits */
87 code_int maxmaxcode = 1 << BITS;	/* should NEVER generate this code */
88 
89 #define MAXCODE(n_bits)	((1 << (n_bits)) - 1)
90 
91 count_int htab[HSIZE];
92 ushort codetab[HSIZE];
93 
94 #define htabof(i)	htab[i]
95 #define codetabof(i)	codetab[i]
96 
97 code_int hsize = HSIZE;			/* for dynamic table sizing */
98 count_int fsize;
99 
100 /*
101  * To save much memory, we overlay the table used by compress() with those
102  * used by decompress().  The tab_prefix table is the same size and type
103  * as the codetab.  The tab_suffix table needs 2**BITS characters.  We
104  * get this from the beginning of htab.  The output stack uses the rest
105  * of htab, and contains characters.  There is plenty of room for any
106  * possible stack (stack used to be 8000 characters).
107  */
108 
109 #define tab_prefixof(i)	codetabof(i)
110 #define tab_suffixof(i)	((uchar *)(htab))[i]
111 #define de_stack		((uchar *)&tab_suffixof(1<<BITS))
112 
113 code_int free_ent = 0;			/* first unused entry */
114 int exit_stat = 0;
115 
116 void	cl_block(void);
117 void	cl_hash(count_int);
118 void	compress(void);
119 void	copystat(char *, char *);
120 void	decompress(void);
121 int	foreground(void);
122 code_int getcode(void);
123 void	onintr(int);
124 void	oops(int);
125 void	output(code_int);
126 void	prratio(FILE *, long, long);
127 void	version(void);
128 void	writeerr(void);
129 
130 void
131 Usage(void)
132 {
133 #ifdef DEBUG
134 	fprintf(stderr,"Usage: compress [-cdfDV] [-b maxbits] [file ...]\n");
135 #else
136 	fprintf(stderr,"Usage: compress [-cdfvV] [-b maxbits] [file ...]\n");
137 #endif /* DEBUG */
138 }
139 
140 int debug = 0;
141 int nomagic = 0;	/* Use a 3-byte magic number header, unless old file */
142 int zcat_flg = 0;	/* Write output on stdout, suppress messages */
143 int quiet = 1;		/* don't tell me about compression */
144 
145 /*
146  * block compression parameters -- after all codes are used up,
147  * and compression rate changes, start over.
148  */
149 int block_compress = BLOCK_MASK;
150 int clear_flg = 0;
151 long ratio = 0;
152 #define CHECK_GAP 10000	/* ratio check interval */
153 count_int checkpoint = CHECK_GAP;
154 /*
155  * the next two codes should not be changed lightly, as they must not
156  * lie within the contiguous general code space.
157  */
158 #define FIRST	257	/* first free entry */
159 #define	CLEAR	256	/* table clear output code */
160 
161 int force = 0;
162 char ofname [100];
163 #ifdef DEBUG
164 int verbose = 0;
165 #endif /* DEBUG */
166 void (*bgnd_flag)(int);
167 
168 int do_decomp = 0;
169 
170 int
171 main(argc, argv)
172 int argc;
173 char **argv;
174 {
175 	int overwrite = 0;	/* Do not overwrite unless given -f flag */
176 	char tempname[512];
177 	char **filelist, **fileptr;
178 	char *cp;
179 	struct stat statbuf;
180 
181 	if ( (bgnd_flag = signal ( SIGINT, SIG_IGN )) != SIG_IGN ) {
182 		signal(SIGINT, onintr);
183 		signal(SIGSEGV, oops);
184 	}
185 
186 	filelist = fileptr = (char **)(malloc(argc * sizeof(*argv)));
187 	*filelist = NULL;
188 
189 	if((cp = strrchr(argv[0], '/')) != 0)
190 		cp++;
191 	else
192 		cp = argv[0];
193 	if(strcmp(cp, "uncompress") == 0)
194 		do_decomp = 1;
195 	else if(strcmp(cp, "zcat") == 0) {
196 		do_decomp = 1;
197 		zcat_flg = 1;
198 	}
199 
200 	/*
201 	 * Argument Processing
202 	 * All flags are optional.
203 	 * -C	generate output compatible with compress 2.0.
204 	 * -D	debug
205 	 * -V	print Version; debug verbose
206 	 * -b maxbits	maxbits.  If -b is specified, then maxbits MUST be
207 	 *		given also.
208 	 * -c	cat all output to stdout
209 	 * -d	do_decomp
210 	 * -f	force overwrite of output file
211 	 * -n	no header: useful to uncompress old files
212 	 * -v	unquiet
213 	 * if a string is left, must be an input filename.
214 	 */
215 	for (argc--, argv++; argc > 0; argc--, argv++) {
216 	if (**argv == '-') {	/* A flag argument */
217 		while (*++(*argv)) {	/* Process all flags in this arg */
218 		switch (**argv) {
219 		case 'C':
220 			block_compress = 0;
221 			break;
222 #ifdef DEBUG
223 		case 'D':
224 			debug = 1;
225 			break;
226 		case 'V':
227 			verbose = 1;
228 			version();
229 			break;
230 #else
231 		case 'V':
232 			version();
233 			break;
234 #endif
235 		case 'b':
236 			if (!ARGVAL()) {
237 				fprintf(stderr, "Missing maxbits\n");
238 				Usage();
239 				exit(1);
240 			}
241 			maxbits = atoi(*argv);
242 			goto nextarg;
243 		case 'c':
244 			zcat_flg = 1;
245 			break;
246 		case 'd':
247 			do_decomp = 1;
248 			break;
249 		case 'f':
250 		case 'F':
251 			overwrite = 1;
252 			force = 1;
253 			break;
254 		case 'n':
255 			nomagic = 1;
256 			break;
257 		case 'q':
258 			quiet = 1;
259 			break;
260 		case 'v':
261 			quiet = 0;
262 			break;
263 		default:
264 			fprintf(stderr, "Unknown flag: '%c'; ", **argv);
265 			Usage();
266 			exit(1);
267 		}
268 		}
269 	} else {			/* Input file name */
270 		*fileptr++ = *argv;	/* Build input file list */
271 		*fileptr = NULL;
272 		/* process nextarg; */
273 	}
274 nextarg:
275 		continue;
276 	}
277 
278 	if(maxbits < INIT_BITS) maxbits = INIT_BITS;
279 	if (maxbits > BITS) maxbits = BITS;
280 	maxmaxcode = 1 << maxbits;
281 
282 	if (*filelist != NULL) {
283 	for (fileptr = filelist; *fileptr; fileptr++) {
284 		exit_stat = 0;
285 		if (do_decomp != 0) {			/* DECOMPRESSION */
286 		/* Check for .Z suffix */
287 		if (strcmp(*fileptr + strlen(*fileptr) - 2, ".Z") != 0) {
288 			/* No .Z: tack one on */
289 			strcpy(tempname, *fileptr);
290 			strcat(tempname, ".Z");
291 			*fileptr = tempname;
292 		}
293 		/* Open input file */
294 		if ((freopen(*fileptr, "r", stdin)) == NULL) {
295 			perror(*fileptr);
296 			continue;
297 		}
298 		/* Check the magic number */
299 		if (nomagic == 0) {
300 			if ((getchar() != (magic_header[0] & 0xFF))
301 			|| (getchar() != (magic_header[1] & 0xFF))) {
302 				fprintf(stderr, "%s: not in compressed format\n",
303 					*fileptr);
304 				continue;
305 			}
306 			maxbits = getchar();	/* set -b from file */
307 			block_compress = maxbits & BLOCK_MASK;
308 			maxbits &= BIT_MASK;
309 			maxmaxcode = 1 << maxbits;
310 			if(maxbits > BITS) {
311 				fprintf(stderr,
312 		"%s: compressed with %d bits, can only handle %d bits\n",
313 					*fileptr, maxbits, BITS);
314 				continue;
315 			}
316 		}
317 		/* Generate output filename */
318 		strcpy(ofname, *fileptr);
319 		ofname[strlen(*fileptr) - 2] = '\0';  /* Strip off .Z */
320 		} else {				/* COMPRESSION */
321 		if (strcmp(*fileptr + strlen(*fileptr) - 2, ".Z") == 0) {
322 			fprintf(stderr,
323 				"%s: already has .Z suffix -- no change\n",
324 				*fileptr);
325 			continue;
326 		}
327 		/* Open input file */
328 		if ((freopen(*fileptr, "r", stdin)) == NULL) {
329 			perror(*fileptr);
330 			continue;
331 		}
332 		(void) stat(*fileptr, &statbuf);
333 		fsize = (long) statbuf.st_size;
334 		/*
335 		 * tune hash table size for small files -- ad hoc,
336 		 * but the sizes match earlier #defines, which
337 		 * serve as upper bounds on the number of output codes.
338 		 */
339 		hsize = HSIZE;
340 		if (fsize < (1 << 12))
341 			hsize = min(5003, HSIZE);
342 		else if (fsize < (1 << 13))
343 			hsize = min(9001, HSIZE);
344 		else if (fsize < (1 << 14))
345 			hsize = min (18013, HSIZE);
346 		else if (fsize < (1 << 15))
347 			hsize = min (35023, HSIZE);
348 		else if (fsize < 47000)
349 			hsize = min (50021, HSIZE);
350 
351 		/* Generate output filename */
352 		strcpy(ofname, *fileptr);
353 #ifndef BSD4_2
354 		if ((cp=strrchr(ofname,'/')) != NULL)
355 			cp++;
356 		else
357 			cp = ofname;
358 		/*
359 		 *** changed 12 to 25;  should be NAMELEN-3, but I don't want
360 		 * to fight the headers.	ehg 5 Nov 92 **
361 		 */
362 		if (strlen(cp) > 25) {
363 			fprintf(stderr, "%s: filename too long to tack on .Z\n",
364 				cp);
365 			continue;
366 		}
367 #endif
368 		strcat(ofname, ".Z");
369 		}
370 		/* Check for overwrite of existing file */
371 		if (overwrite == 0 && zcat_flg == 0 &&
372 		   stat(ofname, &statbuf) == 0) {
373 			char response[2];
374 
375 			response[0] = 'n';
376 			fprintf(stderr, "%s already exists;", ofname);
377 			if (foreground()) {
378 				fprintf(stderr,
379 				    " do you wish to overwrite %s (y or n)? ",
380 					ofname);
381 				fflush(stderr);
382 				(void) read(2, response, 2);
383 				while (response[1] != '\n')
384 					if (read(2, response+1, 1) < 0) {
385 						/* Ack! */
386 						perror("stderr");
387 						break;
388 					}
389 			}
390 			if (response[0] != 'y') {
391 				fprintf(stderr, "\tnot overwritten\n");
392 				continue;
393 			}
394 		}
395 		if(zcat_flg == 0) {		/* Open output file */
396 			if (freopen(ofname, "w", stdout) == NULL) {
397 				perror(ofname);
398 				continue;
399 			}
400 			if(!quiet)
401 				fprintf(stderr, "%s: ", *fileptr);
402 		}
403 
404 		/* Actually do the compression/decompression */
405 		if (do_decomp == 0)
406 			compress();
407 #ifndef DEBUG
408 		else
409 			decompress();
410 #else
411 		else if (debug == 0)
412 			decompress();
413 		else
414 			printcodes();
415 		if (verbose)
416 			dump_tab();
417 #endif						/* DEBUG */
418 		if(zcat_flg == 0) {
419 			copystat(*fileptr, ofname);	/* Copy stats */
420 			if (exit_stat == 1 || !quiet)
421 				putc('\n', stderr);
422 		}
423 	}
424 	} else {		/* Standard input */
425 	if (do_decomp == 0) {
426 		compress();
427 #ifdef DEBUG
428 		if(verbose)
429 			dump_tab();
430 #endif
431 		if(!quiet)
432 			putc('\n', stderr);
433 	} else {
434 		/* Check the magic number */
435 		if (nomagic == 0) {
436 		if ((getchar()!=(magic_header[0] & 0xFF))
437 		 || (getchar()!=(magic_header[1] & 0xFF))) {
438 			fprintf(stderr, "stdin: not in compressed format\n");
439 			exit(1);
440 		}
441 		maxbits = getchar();	/* set -b from file */
442 		block_compress = maxbits & BLOCK_MASK;
443 		maxbits &= BIT_MASK;
444 		maxmaxcode = 1 << maxbits;
445 		fsize = 100000;		/* assume stdin large for USERMEM */
446 		if(maxbits > BITS) {
447 			fprintf(stderr,
448 			"stdin: compressed with %d bits, can only handle %d bits\n",
449 			maxbits, BITS);
450 			exit(1);
451 		}
452 		}
453 #ifndef DEBUG
454 		decompress();
455 #else
456 		if (debug == 0)
457 			decompress();
458 		else
459 			printcodes();
460 		if (verbose)
461 			dump_tab();
462 #endif						/* DEBUG */
463 	}
464 	}
465 	exit(exit_stat);
466 	return 0;
467 }
468 
469 static int offset;
470 long in_count = 1;		/* length of input */
471 long bytes_out;			/* length of compressed output */
472 long out_count = 0;		/* # of codes output (for debugging) */
473 
474 /*
475  * compress stdin to stdout
476  *
477  * Algorithm:  use open addressing double hashing (no chaining) on the
478  * prefix code / next character combination.  We do a variant of Knuth's
479  * algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime
480  * secondary probe.  Here, the modular division first probe is gives way
481  * to a faster exclusive-or manipulation.  Also do block compression with
482  * an adaptive reset, whereby the code table is cleared when the compression
483  * ratio decreases, but after the table fills.  The variable-length output
484  * codes are re-sized at this point, and a special CLEAR code is generated
485  * for the decompressor.  Late addition:  construct the table according to
486  * file size for noticeable speed improvement on small files.  Please direct
487  * questions about this implementation to ames!jaw.
488  */
489 void
490 compress(void)
491 {
492 	code_int ent, hsize_reg;
493 	code_int i;
494 	int c, disp, hshift;
495 	long fcode;
496 
497 	if (nomagic == 0) {
498 		putchar(magic_header[0]);
499 		putchar(magic_header[1]);
500 		putchar((char)(maxbits | block_compress));
501 		if(ferror(stdout))
502 			writeerr();
503 	}
504 	offset = 0;
505 	bytes_out = 3;		/* includes 3-byte header mojo */
506 	out_count = 0;
507 	clear_flg = 0;
508 	ratio = 0;
509 	in_count = 1;
510 	checkpoint = CHECK_GAP;
511 	maxcode = MAXCODE(n_bits = INIT_BITS);
512 	free_ent = (block_compress? FIRST: 256);
513 
514 	ent = getchar ();
515 
516 	hshift = 0;
517 	for (fcode = (long)hsize;  fcode < 65536L; fcode *= 2)
518 		hshift++;
519 	hshift = 8 - hshift;		/* set hash code range bound */
520 
521 	hsize_reg = hsize;
522 	cl_hash( (count_int) hsize_reg);		/* clear hash table */
523 
524 	while ((c = getchar()) != EOF) {
525 		in_count++;
526 		fcode = (long) (((long) c << maxbits) + ent);
527 	 	i = ((c << hshift) ^ ent);	/* xor hashing */
528 
529 		if (htabof (i) == fcode) {
530 			ent = codetabof(i);
531 			continue;
532 		} else if ((long)htabof(i) < 0 )	/* empty slot */
533 			goto nomatch;
534 	 	disp = hsize_reg - i;	/* secondary hash (after G. Knott) */
535 		if (i == 0)
536 			disp = 1;
537 probe:
538 		if ((i -= disp) < 0)
539 			i += hsize_reg;
540 
541 		if (htabof (i) == fcode) {
542 			ent = codetabof(i);
543 			continue;
544 		}
545 		if ((long)htabof(i) > 0)
546 			goto probe;
547 nomatch:
548 		output((code_int)ent);
549 		out_count++;
550 	 	ent = c;
551 		if (free_ent < maxmaxcode) {
552 	 		codetabof(i) = free_ent++;	/* code -> hashtable */
553 			htabof(i) = fcode;
554 		} else if ((count_int)in_count >= checkpoint && block_compress)
555 			cl_block ();
556 	}
557 	/*
558 	* Put out the final code.
559 	*/
560 	output( (code_int)ent );
561 	out_count++;
562 	output( (code_int)-1 );
563 
564 	/*
565 	* Print out stats on stderr
566 	*/
567 	if(zcat_flg == 0 && !quiet) {
568 #ifdef DEBUG
569 	fprintf( stderr,
570 		"%ld chars in, %ld codes (%ld bytes) out, compression factor: ",
571 		in_count, out_count, bytes_out );
572 	prratio( stderr, in_count, bytes_out );
573 	fprintf( stderr, "\n");
574 	fprintf( stderr, "\tCompression as in compact: " );
575 	prratio( stderr, in_count-bytes_out, in_count );
576 	fprintf( stderr, "\n");
577 	fprintf( stderr, "\tLargest code (of last block) was %d (%d bits)\n",
578 		free_ent - 1, n_bits );
579 #else /* !DEBUG */
580 	fprintf( stderr, "Compression: " );
581 	prratio( stderr, in_count-bytes_out, in_count );
582 #endif /* DEBUG */
583 	}
584 	if(bytes_out > in_count)	/* exit(2) if no savings */
585 		exit_stat = 2;
586 }
587 
588 /*
589  * TAG( output )
590  *
591  * Output the given code.
592  * Inputs:
593  * 	code:	A n_bits-bit integer.  If == -1, then EOF.  This assumes
594  *		that n_bits =< (long)wordsize - 1.
595  * Outputs:
596  * 	Outputs code to the file.
597  * Assumptions:
598  *	Chars are 8 bits long.
599  * Algorithm:
600  * 	Maintain a BITS character long buffer (so that 8 codes will
601  * fit in it exactly).  When the buffer fills up empty it and start over.
602  */
603 
604 static char buf[BITS];
605 
606 uchar lmask[9] = {0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80, 0x00};
607 uchar rmask[9] = {0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff};
608 
609 void
610 output( code )
611 code_int  code;
612 {
613 #ifdef DEBUG
614 	static int col = 0;
615 #endif
616 	int r_off = offset, bits= n_bits;
617 	char *bp = buf;
618 
619 #ifdef DEBUG
620 	if (verbose)
621 		fprintf(stderr, "%5d%c", code,
622 			(col+=6) >= 74? (col = 0, '\n'): ' ');
623 #endif
624 	if (code >= 0) {
625 		/*
626 		 * byte/bit numbering on the VAX is simulated by the
627 		 * following code
628 		 */
629 		/*
630 		 * Get to the first byte.
631 		 */
632 		bp += (r_off >> 3);
633 		r_off &= 7;
634 		/*
635 		 * Since code is always >= 8 bits, only need to mask the first
636 		 * hunk on the left.
637 		 */
638 		*bp = (*bp & rmask[r_off]) | (code << r_off) & lmask[r_off];
639 		bp++;
640 		bits -=  8 - r_off;
641 		code >>= 8 - r_off;
642 		/* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */
643 		if ( bits >= 8 ) {
644 			*bp++ = code;
645 			code >>= 8;
646 			bits -= 8;
647 		}
648 		/* Last bits. */
649 		if(bits)
650 			*bp = code;
651 
652 		offset += n_bits;
653 		if ( offset == (n_bits << 3) ) {
654 			bp = buf;
655 			bits = n_bits;
656 			bytes_out += bits;
657 			do {
658 				putchar(*bp++);
659 			} while(--bits);
660 			offset = 0;
661 		}
662 
663 		/*
664 		 * If the next entry is going to be too big for the code size,
665 		 * then increase it, if possible.
666 		 */
667 		if ( free_ent > maxcode || (clear_flg > 0)) {
668 			/*
669 			* Write the whole buffer, because the input side won't
670 			* discover the size increase until after it has read it.
671 			*/
672 			if ( offset > 0 ) {
673 				if( fwrite( buf, 1, n_bits, stdout ) != n_bits)
674 					writeerr();
675 				bytes_out += n_bits;
676 			}
677 			offset = 0;
678 
679 			if ( clear_flg ) {
680 				maxcode = MAXCODE (n_bits = INIT_BITS);
681 				clear_flg = 0;
682 			} else {
683 				n_bits++;
684 				if ( n_bits == maxbits )
685 					maxcode = maxmaxcode;
686 				else
687 					maxcode = MAXCODE(n_bits);
688 			}
689 #ifdef DEBUG
690 			if ( debug ) {
691 				fprintf(stderr,
692 					"\nChange to %d bits\n", n_bits);
693 				col = 0;
694 			}
695 #endif
696 		}
697 	} else {
698 		/*
699 		 * At EOF, write the rest of the buffer.
700 		 */
701 		if ( offset > 0 )
702 			fwrite( buf, 1, (offset + 7) / 8, stdout );
703 		bytes_out += (offset + 7) / 8;
704 		offset = 0;
705 		fflush( stdout );
706 #ifdef DEBUG
707 		if ( verbose )
708 			fprintf( stderr, "\n" );
709 #endif
710 		if( ferror( stdout ) )
711 			writeerr();
712 	}
713 }
714 
715 /*
716  * Decompress stdin to stdout.  This routine adapts to the codes in the
717  * file building the "string" table on-the-fly; requiring no table to
718  * be stored in the compressed file.  The tables used herein are shared
719  * with those of the compress() routine.  See the definitions above.
720  */
721 void
722 decompress(void)
723 {
724 	int finchar;
725 	code_int code, oldcode, incode;
726 	uchar *stackp;
727 
728 	/*
729 	* As above, initialize the first 256 entries in the table.
730 	*/
731 	maxcode = MAXCODE(n_bits = INIT_BITS);
732 	for (code = 255; code >= 0; code--) {
733 		tab_prefixof(code) = 0;
734 		tab_suffixof(code) = (uchar)code;
735 	}
736 	free_ent = (block_compress? FIRST: 256);
737 
738 	finchar = oldcode = getcode();
739 	if(oldcode == -1)		/* EOF already? */
740 		return;			/* Get out of here */
741 	putchar((char)finchar);		/* first code must be 8 bits = char */
742 	if(ferror(stdout))		/* Crash if can't write */
743 		writeerr();
744 	stackp = de_stack;
745 
746 	while ((code = getcode()) > -1) {
747 		if ((code == CLEAR) && block_compress) {
748 			for (code = 255; code >= 0; code--)
749 				tab_prefixof(code) = 0;
750 			clear_flg = 1;
751 			free_ent = FIRST - 1;
752 			if ((code = getcode()) == -1)	/* O, untimely death! */
753 				break;
754 		}
755 		incode = code;
756 		/*
757 		 * Special case for KwKwK string.
758 		 */
759 		if (code >= free_ent) {
760 			*stackp++ = finchar;
761 			code = oldcode;
762 		}
763 
764 		/*
765 		 * Generate output characters in reverse order
766 		 */
767 		while (code >= 256) {
768 			*stackp++ = tab_suffixof(code);
769 			code = tab_prefixof(code);
770 		}
771 		*stackp++ = finchar = tab_suffixof(code);
772 
773 		/*
774 		 * And put them out in forward order
775 		 */
776 		do {
777 			putchar(*--stackp);
778 		} while (stackp > de_stack);
779 
780 		/*
781 		 * Generate the new entry.
782 		 */
783 		if ( (code=free_ent) < maxmaxcode ) {
784 			tab_prefixof(code) = (ushort)oldcode;
785 			tab_suffixof(code) = finchar;
786 			free_ent = code+1;
787 		}
788 		/*
789 		 * Remember previous code.
790 		 */
791 		oldcode = incode;
792 	}
793 	fflush(stdout);
794 	if(ferror(stdout))
795 		writeerr();
796 }
797 
798 /*
799  * TAG( getcode )
800  *
801  * Read one code from the standard input.  If EOF, return -1.
802  * Inputs:
803  * 	stdin
804  * Outputs:
805  * 	code or -1 is returned.
806  */
807 code_int
808 getcode()
809 {
810 	int r_off, bits;
811 	code_int code;
812 	static int offset = 0, size = 0;
813 	static uchar buf[BITS];
814 	uchar *bp = buf;
815 
816 	if ( clear_flg > 0 || offset >= size || free_ent > maxcode ) {
817 		/*
818 		 * If the next entry will be too big for the current code
819 		 * size, then we must increase the size.  This implies reading
820 		 * a new buffer full, too.
821 		 */
822 		if ( free_ent > maxcode ) {
823 			n_bits++;
824 			if ( n_bits == maxbits )
825 				maxcode = maxmaxcode; /* won't get any bigger now */
826 			else
827 				maxcode = MAXCODE(n_bits);
828 		}
829 		if ( clear_flg > 0) {
830 			maxcode = MAXCODE(n_bits = INIT_BITS);
831 			clear_flg = 0;
832 		}
833 		size = fread(buf, 1, n_bits, stdin);
834 		if (size <= 0)
835 			return -1;			/* end of file */
836 		offset = 0;
837 		/* Round size down to integral number of codes */
838 		size = (size << 3) - (n_bits - 1);
839 	}
840 	r_off = offset;
841 	bits = n_bits;
842 	/*
843 	 * Get to the first byte.
844 	 */
845 	bp += (r_off >> 3);
846 	r_off &= 7;
847 	/* Get first part (low order bits) */
848 	code = (*bp++ >> r_off);
849 	bits -= (8 - r_off);
850 	r_off = 8 - r_off;		/* now, offset into code word */
851 	/* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */
852 	if (bits >= 8) {
853 		code |= *bp++ << r_off;
854 		r_off += 8;
855 		bits -= 8;
856 	}
857 	/* high order bits. */
858 	code |= (*bp & rmask[bits]) << r_off;
859 	offset += n_bits;
860 	return code;
861 }
862 
863 #ifdef DEBUG
864 printcodes()
865 {
866 	/*
867 	* Just print out codes from input file.  For debugging.
868 	*/
869 	code_int code;
870 	int col = 0, bits;
871 
872 	bits = n_bits = INIT_BITS;
873 	maxcode = MAXCODE(n_bits);
874 	free_ent = ((block_compress) ? FIRST : 256 );
875 	while ( ( code = getcode() ) >= 0 ) {
876 	if ( (code == CLEAR) && block_compress ) {
877 			free_ent = FIRST - 1;
878 			clear_flg = 1;
879 	}
880 	else if ( free_ent < maxmaxcode )
881 		free_ent++;
882 	if ( bits != n_bits ) {
883 		fprintf(stderr, "\nChange to %d bits\n", n_bits );
884 		bits = n_bits;
885 		col = 0;
886 	}
887 	fprintf(stderr, "%5d%c", code, (col+=6) >= 74 ? (col = 0, '\n') : ' ' );
888 	}
889 	putc( '\n', stderr );
890 	exit( 0 );
891 }
892 
893 code_int sorttab[1<<BITS];	/* sorted pointers into htab */
894 
895 #define STACK_SIZE	15000
896 
897 dump_tab()	/* dump string table */
898 {
899 	int i, first, c, ent;
900 	int stack_top = STACK_SIZE;
901 
902 	if(do_decomp == 0) {	/* compressing */
903 	int flag = 1;
904 
905 	for(i=0; i<hsize; i++) {	/* build sort pointers */
906 		if((long)htabof(i) >= 0) {
907 			sorttab[codetabof(i)] = i;
908 		}
909 	}
910 	first = block_compress ? FIRST : 256;
911 	for(i = first; i < free_ent; i++) {
912 		fprintf(stderr, "%5d: \"", i);
913 		de_stack[--stack_top] = '\n';
914 		de_stack[--stack_top] = '"';
915 		stack_top = in_stack((htabof(sorttab[i])>>maxbits)&0xff,
916 	stack_top);
917 		for(ent=htabof(sorttab[i]) & ((1<<maxbits)-1);
918 			ent > 256;
919 			ent=htabof(sorttab[ent]) & ((1<<maxbits)-1)) {
920 			stack_top = in_stack(htabof(sorttab[ent]) >> maxbits,
921 						stack_top);
922 		}
923 		stack_top = in_stack(ent, stack_top);
924 		fwrite( &de_stack[stack_top], 1, STACK_SIZE-stack_top, stderr);
925 			stack_top = STACK_SIZE;
926 	}
927 	} else if(!debug) {	/* decompressing */
928 
929 	for ( i = 0; i < free_ent; i++ ) {
930 		ent = i;
931 		c = tab_suffixof(ent);
932 		if ( isascii(c) && isprint(c) )
933 		fprintf( stderr, "%5d: %5d/'%c'  \"",
934 				ent, tab_prefixof(ent), c );
935 		else
936 		fprintf( stderr, "%5d: %5d/\\%03o \"",
937 				ent, tab_prefixof(ent), c );
938 		de_stack[--stack_top] = '\n';
939 		de_stack[--stack_top] = '"';
940 		for ( ; ent != NULL;
941 			ent = (ent >= FIRST ? tab_prefixof(ent) : NULL) ) {
942 		stack_top = in_stack(tab_suffixof(ent), stack_top);
943 		}
944 		fwrite( &de_stack[stack_top], 1, STACK_SIZE - stack_top, stderr );
945 		stack_top = STACK_SIZE;
946 	}
947 	}
948 }
949 
950 int
951 in_stack(int c, int stack_top)
952 {
953 	if ( (isascii(c) && isprint(c) && c != '\\') || c == ' ' ) {
954 		de_stack[--stack_top] = c;
955 	} else {
956 		switch( c ) {
957 		case '\n': de_stack[--stack_top] = 'n'; break;
958 		case '\t': de_stack[--stack_top] = 't'; break;
959 		case '\b': de_stack[--stack_top] = 'b'; break;
960 		case '\f': de_stack[--stack_top] = 'f'; break;
961 		case '\r': de_stack[--stack_top] = 'r'; break;
962 		case '\\': de_stack[--stack_top] = '\\'; break;
963 		default:
964 	 	de_stack[--stack_top] = '0' + c % 8;
965 	 	de_stack[--stack_top] = '0' + (c / 8) % 8;
966 	 	de_stack[--stack_top] = '0' + c / 64;
967 	 	break;
968 		}
969 		de_stack[--stack_top] = '\\';
970 	}
971 	return stack_top;
972 }
973 #endif /* DEBUG */
974 
975 void
976 writeerr(void)
977 {
978 	perror(ofname);
979 	unlink(ofname);
980 	exit(1);
981 }
982 
983 void
984 copystat(ifname, ofname)
985 char *ifname, *ofname;
986 {
987 	int mode;
988 	time_t timep[2];			/* should be struct utimbuf */
989 	struct stat statbuf;
990 
991 	fclose(stdout);
992 	if (stat(ifname, &statbuf)) {		/* Get stat on input file */
993 		perror(ifname);
994 		return;
995 	}
996 	if (!S_ISREG(statbuf.st_mode)) {
997 		if (quiet)
998 			fprintf(stderr, "%s: ", ifname);
999 		fprintf(stderr, " -- not a regular file: unchanged");
1000 		exit_stat = 1;
1001 	} else if (exit_stat == 2 && !force) {
1002 		/* No compression: remove file.Z */
1003 		if (!quiet)
1004 			fprintf(stderr, " -- file unchanged");
1005 	} else {			/* Successful Compression */
1006 		exit_stat = 0;
1007 		mode = statbuf.st_mode & 0777;
1008 		if (chmod(ofname, mode))		/* Copy modes */
1009 			perror(ofname);
1010 		/* Copy ownership */
1011 		chown(ofname, statbuf.st_uid, statbuf.st_gid);
1012 		timep[0] = statbuf.st_atime;
1013 		timep[1] = statbuf.st_mtime;
1014 		/* Update last accessed and modified times */
1015 		utime(ofname, (struct utimbuf *)timep);
1016 //		if (unlink(ifname))	/* Remove input file */
1017 //			perror(ifname);
1018 		return;			/* success */
1019 	}
1020 
1021 	/* Unsuccessful return -- one of the tests failed */
1022 	if (unlink(ofname))
1023 		perror(ofname);
1024 }
1025 
1026 /*
1027  * This routine returns 1 if we are running in the foreground and stderr
1028  * is a tty.
1029  */
1030 int
1031 foreground(void)
1032 {
1033 	if(bgnd_flag)			/* background? */
1034 		return 0;
1035 	else				/* foreground */
1036 		return isatty(2);	/* and stderr is a tty */
1037 }
1038 
1039 void
1040 onintr(int x)
1041 {
1042 	USED(x);
1043 	unlink(ofname);
1044 	exit(1);
1045 }
1046 
1047 void
1048 oops(int x)		/* wild pointer -- assume bad input */
1049 {
1050 	USED(x);
1051 	if (do_decomp == 1)
1052 		fprintf(stderr, "uncompress: corrupt input\n");
1053 	unlink(ofname);
1054 	exit(1);
1055 }
1056 
1057 void
1058 cl_block(void)		/* table clear for block compress */
1059 {
1060 	long rat;
1061 
1062 	checkpoint = in_count + CHECK_GAP;
1063 #ifdef DEBUG
1064 	if ( debug ) {
1065 		fprintf ( stderr, "count: %ld, ratio: ", in_count );
1066 		prratio ( stderr, in_count, bytes_out );
1067 		fprintf ( stderr, "\n");
1068 	}
1069 #endif /* DEBUG */
1070 
1071 	if (in_count > 0x007fffff) {	/* shift will overflow */
1072 		rat = bytes_out >> 8;
1073 		if (rat == 0)		/* Don't divide by zero */
1074 			rat = 0x7fffffff;
1075 		else
1076 			rat = in_count / rat;
1077 	} else
1078 		rat = (in_count << 8) / bytes_out;	/* 8 fractional bits */
1079 	if (rat > ratio)
1080 		ratio = rat;
1081 	else {
1082 		ratio = 0;
1083 #ifdef DEBUG
1084 		if (verbose)
1085 			dump_tab();	/* dump string table */
1086 #endif
1087 		cl_hash((count_int)hsize);
1088 		free_ent = FIRST;
1089 		clear_flg = 1;
1090 		output((code_int)CLEAR);
1091 #ifdef DEBUG
1092 		if (debug)
1093 			fprintf(stderr, "clear\n");
1094 #endif /* DEBUG */
1095 	}
1096 }
1097 
1098 void
1099 cl_hash(count_int hsize)		/* reset code table */
1100 {
1101 	count_int *htab_p = htab+hsize;
1102 	long i;
1103 	long m1 = -1;
1104 
1105 	i = hsize - 16;
1106  	do {				/* might use Sys V memset(3) here */
1107 		*(htab_p-16) = m1;
1108 		*(htab_p-15) = m1;
1109 		*(htab_p-14) = m1;
1110 		*(htab_p-13) = m1;
1111 		*(htab_p-12) = m1;
1112 		*(htab_p-11) = m1;
1113 		*(htab_p-10) = m1;
1114 		*(htab_p-9) = m1;
1115 		*(htab_p-8) = m1;
1116 		*(htab_p-7) = m1;
1117 		*(htab_p-6) = m1;
1118 		*(htab_p-5) = m1;
1119 		*(htab_p-4) = m1;
1120 		*(htab_p-3) = m1;
1121 		*(htab_p-2) = m1;
1122 		*(htab_p-1) = m1;
1123 		htab_p -= 16;
1124 	} while ((i -= 16) >= 0);
1125 	for ( i += 16; i > 0; i-- )
1126 		*--htab_p = m1;
1127 }
1128 
1129 void
1130 prratio(stream, num, den)
1131 FILE *stream;
1132 long num, den;
1133 {
1134 	int q;				/* Doesn't need to be long */
1135 
1136 	if(num > 214748L)		/* 2147483647/10000 */
1137 		q = num / (den / 10000L);
1138 	else
1139 		q = 10000L * num / den;	/* Long calculations, though */
1140 	if (q < 0) {
1141 		putc('-', stream);
1142 		q = -q;
1143 	}
1144 	fprintf(stream, "%d.%02d%%", q / 100, q % 100);
1145 }
1146 
1147 void
1148 version(void)
1149 {
1150 	fprintf(stderr, "%s\n", rcs_ident);
1151 	fprintf(stderr, "Options: ");
1152 #ifdef DEBUG
1153 	fprintf(stderr, "DEBUG, ");
1154 #endif
1155 #ifdef BSD4_2
1156 	fprintf(stderr, "BSD4_2, ");
1157 #endif
1158 	fprintf(stderr, "BITS = %d\n", BITS);
1159 }
1160 
1161 /*
1162  * The revision-history novel:
1163  *
1164  * $Header: compress.c,v 4.0 85/07/30 12:50:00 joe Release $
1165  * $Log:	compress.c,v $
1166  * Revision 4.0  85/07/30  12:50:00  joe
1167  * Removed ferror() calls in output routine on every output except first.
1168  * Prepared for release to the world.
1169  *
1170  * Revision 3.6  85/07/04  01:22:21  joe
1171  * Remove much wasted storage by overlaying hash table with the tables
1172  * used by decompress: tab_suffix[1<<BITS], stack[8000].  Updated USERMEM
1173  * computations.  Fixed dump_tab() DEBUG routine.
1174  *
1175  * Revision 3.5  85/06/30  20:47:21  jaw
1176  * Change hash function to use exclusive-or.  Rip out hash cache.  These
1177  * speedups render the megamemory version defunct, for now.  Make decoder
1178  * stack global.  Parts of the RCS trunks 2.7, 2.6, and 2.1 no longer apply.
1179  *
1180  * Revision 3.4  85/06/27  12:00:00  ken
1181  * Get rid of all floating-point calculations by doing all compression ratio
1182  * calculations in fixed point.
1183  *
1184  * Revision 3.3  85/06/24  21:53:24  joe
1185  * Incorporate portability suggestion for M_XENIX.  Got rid of text on #else
1186  * and #endif lines.  Cleaned up #ifdefs for vax and interdata.
1187  *
1188  * Revision 3.2  85/06/06  21:53:24  jaw
1189  * Incorporate portability suggestions for Z8000, IBM PC/XT from mailing list.
1190  * Default to "quiet" output (no compression statistics).
1191  *
1192  * Revision 3.1  85/05/12  18:56:13  jaw
1193  * Integrate decompress() stack speedups (from early pointer mods by McKie).
1194  * Repair multi-file USERMEM gaffe.  Unify 'force' flags to mimic semantics
1195  * of SVR2 'pack'.  Streamline block-compress table clear logic.  Increase
1196  * output byte count by magic number size.
1197  *
1198  * Revision 3.0	84/11/27  11:50:00  petsd!joe
1199  * Set HSIZE depending on BITS.  Set BITS depending on USERMEM.  Unrolled
1200  * loops in clear routines.  Added "-C" flag for 2.0 compatibility.  Used
1201  * unsigned compares on Perkin-Elmer.  Fixed foreground check.
1202  *
1203  * Revision 2.7	84/11/16  19:35:39  ames!jaw
1204  * Cache common hash codes based on input statistics; this improves
1205  * performance for low-density raster images.  Pass on #ifdef bundle
1206  * from Turkowski.
1207  *
1208  * Revision 2.6	84/11/05  19:18:21  ames!jaw
1209  * Vary size of hash tables to reduce time for small files.
1210  * Tune PDP-11 hash function.
1211  *
1212  * Revision 2.5	84/10/30  20:15:14  ames!jaw
1213  * Junk chaining; replace with the simpler (and, on the VAX, faster)
1214  * double hashing, discussed within.  Make block compression standard.
1215  *
1216  * Revision 2.4	84/10/16  11:11:11  ames!jaw
1217  * Introduce adaptive reset for block compression, to boost the rate
1218  * another several percent.  (See mailing list notes.)
1219  *
1220  * Revision 2.3	84/09/22  22:00:00  petsd!joe
1221  * Implemented "-B" block compress.  Implemented REVERSE sorting of tab_next.
1222  * Bug fix for last bits.  Changed fwrite to putchar loop everywhere.
1223  *
1224  * Revision 2.2	84/09/18  14:12:21  ames!jaw
1225  * Fold in news changes, small machine typedef from thomas,
1226  * #ifdef interdata from joe.
1227  *
1228  * Revision 2.1	84/09/10  12:34:56  ames!jaw
1229  * Configured fast table lookup for 32-bit machines.
1230  * This cuts user time in half for b <= FBITS, and is useful for news batching
1231  * from VAX to PDP sites.  Also sped up decompress() [fwrite->putc] and
1232  * added signal catcher [plus beef in writeerr()] to delete effluvia.
1233  *
1234  * Revision 2.0	84/08/28  22:00:00  petsd!joe
1235  * Add check for foreground before prompting user.  Insert maxbits into
1236  * compressed file.  Force file being uncompressed to end with ".Z".
1237  * Added "-c" flag and "zcat".  Prepared for release.
1238  *
1239  * Revision 1.10  84/08/24  18:28:00  turtlevax!ken
1240  * Will only compress regular files (no directories), added a magic number
1241  * header (plus an undocumented -n flag to handle old files without headers),
1242  * added -f flag to force overwriting of possibly existing destination file,
1243  * otherwise the user is prompted for a response.  Will tack on a .Z to a
1244  * filename if it doesn't have one when decompressing.  Will only replace
1245  * file if it was compressed.
1246  *
1247  * Revision 1.9  84/08/16  17:28:00  turtlevax!ken
1248  * Removed scanargs(), getopt(), added .Z extension and unlimited number of
1249  * filenames to compress.  Flags may be clustered (-Ddvb12) or separated
1250  * (-D -d -v -b 12), or combination thereof.  Modes and other status is
1251  * copied with copystat().  -O bug for 4.2 seems to have disappeared with
1252  * 1.8.
1253  *
1254  * Revision 1.8  84/08/09  23:15:00  joe
1255  * Made it compatible with vax version, installed jim's fixes/enhancements
1256  *
1257  * Revision 1.6  84/08/01  22:08:00  joe
1258  * Sped up algorithm significantly by sorting the compress chain.
1259  *
1260  * Revision 1.5  84/07/13  13:11:00  srd
1261  * Added C version of vax asm routines.  Changed structure to arrays to
1262  * save much memory.  Do unsigned compares where possible (faster on
1263  * Perkin-Elmer)
1264  *
1265  * Revision 1.4  84/07/05  03:11:11  thomas
1266  * Clean up the code a little and lint it.  (Lint complains about all
1267  * the regs used in the asm, but I'm not going to "fix" this.)
1268  *
1269  * Revision 1.3  84/07/05  02:06:54  thomas
1270  * Minor fixes.
1271  *
1272  * Revision 1.2  84/07/05  00:27:27  thomas
1273  * Add variable bit length output.
1274  */