+++ /dev/null
-/* decomp16: decompress 16bit compressed files on a 16bit Intel processor
- *
- * Version 1.3 of 25 Mar 92.
- *
- * This was written by John N. White on 6/30/91 and is Public Domain.
- * Patched to run under news by Will Rose, Feb 92.
- * J N White's (earlier) patches added by Will Rose, 20 Feb 92.
- * Unsigned int increment/wrap bug fixed by Will Rose, 24 Mar 92.
- * Argument bug fixed, stdio generalised by Will Rose, 25 Mar 92.
- *
- * decomp16 can use as as little as 512 bytes of stack; since it forks
- * four additional copies, it's probably worth using minimum stack rather
- * than the 8192 byte Minix default. To reduce memory still further,
- * change BUFSZ below to 256; it is currently set to 1024 for speed. The
- * minimal decomp16 needs about 280k to run in pipe mode (56k per copy).
- *
- * This program acts as a filter:
- * decomp16 < compressed_file > decompressed_file
- * The arguments -0 to -4 run only the corresponding pass.
- * Thus:
- * decomp16 -4 < compressed_file > 3;
- * decomp16 -3 < 3 > 2;
- * decomp16 -2 < 2 > 1;
- * decomp16 -1 < 1 > 0;
- * decomp16 -0 < 0 > decompressed_file
- * will also work, as will connecting the passes by explicit pipes if
- * there is enough memory to do so. File name arguments can also be
- * given directly on the command line.
- *
- * Compress uses a modified LZW compression algorithm. A compressed file
- * is a set of indices into a dictionary of strings. The number of bits
- * used to store each index depends on the number of entries currently
- * in the dictionary. If there are between 257 and 512 entries, 9 bits
- * are used. With 513 entries, 10 bits are used, etc. The initial dictionary
- * consists of 0-255 (which are the corresponding chars) and 256 (which
- * is a special CLEAR code). As each index in the compressed file is read,
- * a new entry is added to the dictionary consisting of the current string
- * with the first char of the next string appended. When the dictionary
- * is full, no further entries are added. If a CLEAR code is received,
- * the dictionary will be completely reset. The first two bytes of the
- * compressed file are a magic number, and the third byte indicates the
- * maximum number of bits, and whether the CLEAR code is used (older versions
- * of compress didn't have CLEAR).
- *
- * This program works by forking four more copies of itself. The five
- * programs form a pipeline. Copy 0 writes to stdout, and forks copy 1
- * to supply its input, which in turn forks and reads from copy 2, etc.
- * This sequence is used so that when the program exits, all writes
- * are completed and a program that has exec'd uncompress (such as news)
- * can immediately use the uncompressed data when the wait() call returns.
- *
- * If given a switch -#, where # is a digit from 0 to 4 (example: -2), the
- * program will run as that copy, reading from stdin and writing to stdout.
- * This allows decompressing with very limited RAM because only one of the
- * five passes is in memory at a time.
- *
- * The compressed data is a series of string indices (and a header at
- * the beginning and an occasional CLEAR code). As these indices flow
- * through the pipes, each program decodes the ones it can. The result
- * of each decoding will be indices that the following programs can handle.
- *
- * Each of the 65536 strings in the dictionary is an earlier string with
- * some character added to the end (except for the the 256 predefined
- * single char strings). When new entries are made to the dictionary,
- * the string index part will just be the last index to pass through.
- * But the char part is the first char of the next string, which isn't
- * known yet. So the string can be stored as a pair of indices. When
- * this string is specified, it is converted to this pair of indices,
- * which are flagged so that the first will be decoded in full while
- * the second will be decoded to its first char. The dictionary takes
- * 256k to store (64k strings of 2 indices of 2 bytes each). This is
- * too big for a 64k data segment, so it is divided into 5 equal parts.
- * Copy 4 of the program maintains the high part and copy 0 holds the
- * low part.
- */
-
-#include <sys/types.h>
-#include <fcntl.h>
-#include <stdlib.h>
-#include <unistd.h>
-
-#define BUFSZ 1024 /* size of i/o buffers */
-#define BUFSZ_2 (BUFSZ/2) /* # of unsigned shorts in i/o bufs */
-#define DICTSZ (unsigned)13056 /* # of local dictionary entries */
-#define EOF_INDEX (unsigned short)0xFFFF /* EOF flag for pipeline */
-#define FALSE 0
-#define TRUE ~FALSE
-
-int fdin, fdout, fderr; /* input, output, and error file descriptors */
-int ibufstart, obufind, ibufend;/* i/o buffer indices */
-int ipbufind = BUFSZ_2; /* pipe buffer indices */
-int opbufind = 0;
-int pnum = -1; /* ID of this copy */
-unsigned short ipbuf[BUFSZ_2]; /* for buffering input */
-unsigned short opbuf[BUFSZ_2]; /* for buffering output */
-unsigned char *ibuf = (unsigned char *) ipbuf;
-unsigned char *obuf = (unsigned char *) opbuf;
-
-unsigned short dindex[DICTSZ]; /* dictionary: index to substring */
-unsigned short dchar[DICTSZ]; /* dictionary: last char of string */
-unsigned iindex, tindex, tindex2; /* holds index being processed */
-unsigned base; /* where in global dict local dict starts */
-unsigned tbase;
-unsigned locend; /* where in global dict local dict ends */
-unsigned curend = 256; /* current end of global dict */
-unsigned maxend; /* max end of global dict */
-int dcharp; /* ptr to dchar that needs next index entry */
-int curbits; /* number of bits for getbits() to read */
-int maxbits; /* limit on number of bits */
-int clearflg; /* if set, allow CLEAR */
-int inmod; /* mod 8 for getbits() */
-
-int main(int argc, char **argv);
-void ffork(void);
-void die(char *s);
-void myputc(unsigned c);
-unsigned mygetc(void);
-void getbits(void);
-void getpipe(void);
-void putpipe(unsigned u, int flag);
-
-int main(int argc, char **argv)
-{
- char c, *cp;
- int j, k, fdtmp;
- unsigned int len;
-
- /* Find the program name */
- j = 0;
- while (argv[0][j] != '\0') j++;
- len = (unsigned int) j;
- while (j--)
- if (argv[0][j] == '/') break;
- if (argv[0][j] == '/') j++;
- cp = argv[0] + j;
- len -= j;
-
- /* Sort out the flags */
- for (k = 1; k < argc; k++) {
- if (argv[k][0] == '-') {
- c = argv[k][1];
- switch (c) {
- case '0': /* pass numbers */
- case '1':
- case '2':
- case '3':
- case '4': pnum = c - '0'; break;
- case 'd': /* used by news */
- break;
- default:
- (void) write(1, "Usage: ", 7);
- (void) write(1, cp, len);
- (void) write(1, " [-#] [in] [out]\n", 17);
- exit(0);
- break;
- }
-
- /* Once it's checked, lose it anyway */
- for (j = k; j < argc; j++) argv[j] = argv[j + 1];
- argc--;
- k--;
- }
- }
-
- /* Default i/o settings */
- fdin = 0;
- fdout = 1;
- fderr = 2;
-
- /* Try to open specific files and connect them to stdin/stdout */
- if (argc > 1) {
- if ((fdtmp = open(argv[1], 0)) == -1) die("input open failed");
- (void) close(0);
- if ((fdin = dup(fdtmp)) == -1) die("input dup failed\n");
- (void) close(fdtmp);
- }
- if (argc > 2) {
- (void) unlink(argv[2]);
- if ((fdtmp = creat(argv[2], 0666)) == -1) die("output creat failed");
- (void) close(1);
- if ((fdout = dup(fdtmp)) == -1) die("output dup failed\n");
- (void) close(fdtmp);
- }
-
- /* Sort out type of compression */
- if (pnum == -1 || pnum == 4) {/* if this is pass 4 */
- /* Check header of compressed file */
- if (mygetc() != 0x1F || mygetc() != 0x9D) /* check magic number */
- die("not a compressed file\n");
- iindex = mygetc(); /* get compression style */
- } else
- getpipe(); /* get compression style */
-
- maxbits = iindex & 0x1F;
- clearflg = ((iindex & 0x80) != 0) ? TRUE : FALSE;
- if (maxbits < 9 || maxbits > 16) /* check for valid maxbits */
- die("can't decompress\n");
- if (pnum != -1 && pnum != 0)
- putpipe(iindex, 0); /* pass style to next copy */
-
- /* Fork off an ancestor if necessary - ffork() increments pnum */
- if (pnum == -1) {
- pnum = 0;
- if (pnum == 0) ffork();
- if (pnum == 1) ffork();
- if (pnum == 2) ffork();
- if (pnum == 3) ffork();
- }
-
- /* Preliminary inits. Note: end/maxend/curend are highest, not
- * highest + 1 */
- base = DICTSZ * pnum + 256;
- locend = base + DICTSZ - 1;
- maxend = (1 << maxbits) - 1;
- if (maxend > locend) maxend = locend;
-
- while (TRUE) {
- curend = 255 + (clearflg ? 1 : 0); /* init dictionary */
- dcharp = DICTSZ; /* flag for none needed */
- curbits = 9; /* init curbits (for copy 0) */
- while (TRUE) { /* for each index in input */
- if (pnum == 4) {/* get index using getbits() */
- if (curbits < maxbits && (1 << curbits) <= curend) {
- /* Curbits needs to be increased */
- /* Due to uglyness in compress, these
- * indices in the compressed file are
- * wasted */
- while (inmod) getbits();
- curbits++;
- }
- getbits();
- } else
- getpipe(); /* get next index */
-
- if (iindex == 256 && clearflg) {
- if (pnum > 0) putpipe(iindex, 0);
- /* Due to uglyness in compress, these indices
- * in the compressed file are wasted */
- while (inmod) getbits();
- break;
- }
- tindex = iindex;
- /* Convert the index part, ignoring spawned chars */
- while (tindex >= base) tindex = dindex[tindex - base];
- /* Pass on the index */
- putpipe(tindex, 0);
- /* Save the char of the last added entry, if any */
- if (dcharp < DICTSZ) dchar[dcharp++] = tindex;
- if (curend < maxend && ++curend > (base - 1))
- dindex[dcharp = (curend - base)] = iindex;
-
- /* Do spawned chars. They are naturally produced in
- * the wrong order. To get them in the right order
- * without using memory, a series of passes,
- * progressively less deep, are used */
- tbase = base;
- while ((tindex = iindex) >= tbase) {/* for each char to spawn*/
- while ((tindex2 = dindex[tindex - base]) >= tbase)
- tindex = tindex2; /* scan to desired char */
- putpipe(dchar[tindex-base], 1); /* put it to the pipe*/
- tbase = tindex + 1;
- if (tbase == 0) break; /* it's a wrap */
- }
- }
- }
-}
-
-
-/* F f o r k
- *
- * Fork off the previous pass - the parent reads from the child.
- */
-void ffork()
-{
- int j, pfd[2];
-
- if (pipe(pfd) == -1) die("pipe() error\n");
- if ((j = fork()) == -1) die("fork() error\n");
- if (j == 0) { /* this is the child */
- if (close(1) == -1) die("close(1) error\n");
- if (dup(pfd[1]) != 1) die("dup(1) error\n");
- (void) close(pfd[0]);
- pnum++;
- } else { /* this is the parent */
- if (close(0) == -1) die("close(0) error\n");
- if (dup(pfd[0]) != 0) die("dup(0) error\n");
- (void) close(pfd[1]);
- }
-}
-
-
-/* D i e
- *
- * If s is a message, write it to stderr. Flush buffers if needed. Then exit.
- */
-void die(char *s)
-{
- /* Flush stdout buffer if needed */
- if (obufind != 0) {
- if (write(fdout, (char *) obuf, (unsigned) obufind) != obufind)
- s = "bad stdout write\n";
- obufind = 0;
- }
-
- /* Flush pipe if needed */
- do
- putpipe(EOF_INDEX, 0);
- while (opbufind);
- /* Write any error message */
- if (s != (char *) NULL) {
- while (*s) (void) write(fderr, s++, 1);
- }
- exit((s == (char *) NULL) ? 0 : 1);
-}
-
-
-/* M p u t c
- *
- * Put a char to stdout.
- */
-void myputc(unsigned c)
-{
- obuf[obufind++] = c;
- if (obufind >= BUFSZ) { /* if stdout buffer full */
- if (write(fdout, (char *) obuf, BUFSZ) != BUFSZ) /* flush to stdout */
- die("bad stdout write\n");
- obufind = 0;
- }
-}
-
-
-/* M y g e t c
- *
- * Get a char from stdin. If EOF, then die() and exit.
- */
-unsigned mygetc()
-{
- if (ibufstart >= ibufend) { /* if stdin buffer empty */
- if ((ibufend = read(fdin, (char *) ibuf, BUFSZ)) <= 0)
- die((char *) NULL); /* if EOF, do normal exit */
- ibufstart = 0;
- }
- return(ibuf[ibufstart++] & 0xff);
-}
-
-
-/* G e t b i t s
- *
- * Put curbits bits into index from stdin. Note: only copy 4 uses this.
- * The bits within a byte are in the correct order. But when the bits
- * cross a byte boundry, the lowest bits will be in the higher part of
- * the current byte, and the higher bits will be in the lower part of
- * the next byte.
- */
-void getbits()
-{
- int have;
- static unsigned curbyte; /* byte having bits extracted from it */
- static int left; /* how many bits are left in curbyte */
-
- inmod = (inmod + 1) & 7; /* count input mod 8 */
- iindex = curbyte;
- have = left;
- if (curbits - have > 8) {
- iindex |= mygetc() << have;
- have += 8;
- }
- iindex |= ((curbyte = mygetc()) << have) & ~((unsigned) 0xFFFF << curbits);
- curbyte >>= curbits - have;
- left = 8 - (curbits - have);
-}
-
-
-/* G e t p i p e
- *
- * Get an index from the pipeline. If flagged firstonly, handle it here.
- */
-void getpipe()
-{
- static short flags;
- static int n = 0; /* number of flags in flags */
-
- while (TRUE) { /* while index with firstonly flag set */
- if (n <= 0) {
- if (ipbufind >= BUFSZ_2) { /* if pipe input buffer
- * empty */
- if (read(fdin, (char *) ipbuf, BUFSZ) != BUFSZ)
- die("bad pipe read\n");
- ipbufind = 0;
- }
- flags = ipbuf[ipbufind++];
- n = 15;
- }
- iindex = ipbuf[ipbufind++];
- if (iindex > curend)
- die((iindex == EOF_INDEX) ? (char *) NULL : "invalid data\n");
- flags <<= 1;
- n--;
- /* Assume flags < 0 if highest remaining flag is set */
- if (flags < 0) { /* if firstonly flag for index is not set */
- while (iindex >= base) iindex = dindex[iindex - base];
- putpipe(iindex, 1);
- } else
- return; /* return with valid non-firstonly index */
- }
-}
-
-
-/* P u t p i p e
- *
- * put an index into the pipeline.
- */
-void putpipe(unsigned u, int flag)
-{
- static unsigned short flags, *flagp;
- static int n = 0; /* number of flags in flags */
-
- if (pnum == 0) { /* if we should write to stdout */
- myputc(u); /* index will be the char value */
- return;
- }
- if (n == 0) { /* if we need to reserve a flag entry */
- flags = 0;
- flagp = opbuf + opbufind;
- opbufind++;
- }
- opbuf[opbufind++] = u; /* add index to buffer */
- flags = (flags << 1) | flag; /* add firstonly flag */
- if (++n >= 15) { /* if block of 15 indices */
- n = 0;
- *flagp = flags; /* insert flags entry */
- if (opbufind >= BUFSZ_2) { /* if pipe out buffer full */
- opbufind = 0;
- if (write(fdout, (char *) opbuf, BUFSZ) != BUFSZ)
- die("bad pipe write\n");
- }
- }
-}