gzip.c

这是一个SIGMA方案的PMP播放器的UCLINUX程序,可播放DVD,VCD,CD MP3...有很好的参考价值.

#define UPDATE_HASH(h,c) (h = (((h)<<H_SHIFT) ^ (c)) & HASH_MASK)

/* ===========================================================================
 * Insert string s in the dictionary and set match_head to the previous head
 * of the hash chain (the most recent string with same hash key). Return
 * the previous length of the hash chain.
 * IN  assertion: all calls to to INSERT_STRING are made with consecutive
 *    input characters and the first MIN_MATCH bytes of s are valid
 *    (except for the last MIN_MATCH-1 bytes of the input file).
 */
#define INSERT_STRING(s, match_head) \
   (UPDATE_HASH(ins_h, window[(s) + MIN_MATCH-1]), \
    prev[(s) & WMASK] = match_head = head[ins_h], \
    head[ins_h] = (s))

/* ===========================================================================
 * Initialize the "longest match" routines for a new file
 */
static void lm_init(ush *flags)
{
	register unsigned j;

	/* Initialize the hash table. */
	memzero((char *) head, HASH_SIZE * sizeof(*head));
	/* prev will be initialized on the fly */

	*flags |= SLOW;
	/* ??? reduce max_chain_length for binary files */

	strstart = 0;
	block_start = 0L;

	lookahead = read_buf((char *) window,
						 sizeof(int) <= 2 ? (unsigned) WSIZE : 2 * WSIZE);

	if (lookahead == 0 || lookahead == (unsigned) EOF) {
		eofile = 1, lookahead = 0;
		return;
	}
	eofile = 0;
	/* Make sure that we always have enough lookahead. This is important
	 * if input comes from a device such as a tty.
	 */
	while (lookahead < MIN_LOOKAHEAD && !eofile)
		fill_window();

	ins_h = 0;
	for (j = 0; j < MIN_MATCH - 1; j++)
		UPDATE_HASH(ins_h, window[j]);
	/* If lookahead < MIN_MATCH, ins_h is garbage, but this is
	 * not important since only literal bytes will be emitted.
	 */
}

/* ===========================================================================
 * Set match_start to the longest match starting at the given string and
 * return its length. Matches shorter or equal to prev_length are discarded,
 * in which case the result is equal to prev_length and match_start is
 * garbage.
 * IN assertions: cur_match is the head of the hash chain for the current
 *   string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
 */

/* For MSDOS, OS/2 and 386 Unix, an optimized version is in match.asm or
 * match.s. The code is functionally equivalent, so you can use the C version
 * if desired.
 */
static int longest_match(IPos cur_match)
{
	unsigned chain_length = max_chain_length;	/* max hash chain length */
	register uch *scan = window + strstart;	/* current string */
	register uch *match;		/* matched string */
	register int len;			/* length of current match */
	int best_len = prev_length;	/* best match length so far */
	IPos limit =

		strstart > (IPos) MAX_DIST ? strstart - (IPos) MAX_DIST : NIL;
	/* Stop when cur_match becomes <= limit. To simplify the code,
	 * we prevent matches with the string of window index 0.
	 */

/* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
 * It is easy to get rid of this optimization if necessary.
 */
#if HASH_BITS < 8 || MAX_MATCH != 258
#  error Code too clever
#endif
	register uch *strend = window + strstart + MAX_MATCH;
	register uch scan_end1 = scan[best_len - 1];
	register uch scan_end = scan[best_len];

	/* Do not waste too much time if we already have a good match: */
	if (prev_length >= good_match) {
		chain_length >>= 2;
	}
	Assert(strstart <= window_size - MIN_LOOKAHEAD,
		   "insufficient lookahead");

	do {
		Assert(cur_match < strstart, "no future");
		match = window + cur_match;

		/* Skip to next match if the match length cannot increase
		 * or if the match length is less than 2:
		 */
		if (match[best_len] != scan_end ||
			match[best_len - 1] != scan_end1 ||
			*match != *scan || *++match != scan[1])
			continue;

		/* The check at best_len-1 can be removed because it will be made
		 * again later. (This heuristic is not always a win.)
		 * It is not necessary to compare scan[2] and match[2] since they
		 * are always equal when the other bytes match, given that
		 * the hash keys are equal and that HASH_BITS >= 8.
		 */
		scan += 2, match++;

		/* We check for insufficient lookahead only every 8th comparison;
		 * the 256th check will be made at strstart+258.
		 */
		do {
		} while (*++scan == *++match && *++scan == *++match &&
				 *++scan == *++match && *++scan == *++match &&
				 *++scan == *++match && *++scan == *++match &&
				 *++scan == *++match && *++scan == *++match &&
				 scan < strend);

		len = MAX_MATCH - (int) (strend - scan);
		scan = strend - MAX_MATCH;

		if (len > best_len) {
			match_start = cur_match;
			best_len = len;
			if (len >= nice_match)
				break;
			scan_end1 = scan[best_len - 1];
			scan_end = scan[best_len];
		}
	} while ((cur_match = prev[cur_match & WMASK]) > limit
			 && --chain_length != 0);

	return best_len;
}

#ifdef DEBUG
/* ===========================================================================
 * Check that the match at match_start is indeed a match.
 */
static void check_match(IPos start, IPos match, int length)
{
	/* check that the match is indeed a match */
	if (memcmp((char *) window + match,
			   (char *) window + start, length) != EQUAL) {
		fprintf(stderr,
				" start %d, match %d, length %d\n", start, match, length);
		error_msg("invalid match");
	}
	if (verbose > 1) {
		fprintf(stderr, "\\[%d,%d]", start - match, length);
		do {
			putc(window[start++], stderr);
		} while (--length != 0);
	}
}
#else
#  define check_match(start, match, length)
#endif

/* ===========================================================================
 * Fill the window when the lookahead becomes insufficient.
 * Updates strstart and lookahead, and sets eofile if end of input file.
 * IN assertion: lookahead < MIN_LOOKAHEAD && strstart + lookahead > 0
 * OUT assertions: at least one byte has been read, or eofile is set;
 *    file reads are performed for at least two bytes (required for the
 *    translate_eol option).
 */
static void fill_window()
{
	register unsigned n, m;
	unsigned more =

		(unsigned) (window_size - (ulg) lookahead - (ulg) strstart);
	/* Amount of free space at the end of the window. */

	/* If the window is almost full and there is insufficient lookahead,
	 * move the upper half to the lower one to make room in the upper half.
	 */
	if (more == (unsigned) EOF) {
		/* Very unlikely, but possible on 16 bit machine if strstart == 0
		 * and lookahead == 1 (input done one byte at time)
		 */
		more--;
	} else if (strstart >= WSIZE + MAX_DIST) {
		/* By the IN assertion, the window is not empty so we can't confuse
		 * more == 0 with more == 64K on a 16 bit machine.
		 */
		Assert(window_size == (ulg) 2 * WSIZE, "no sliding with BIG_MEM");

		memcpy((char *) window, (char *) window + WSIZE, (unsigned) WSIZE);
		match_start -= WSIZE;
		strstart -= WSIZE;		/* we now have strstart >= MAX_DIST: */

		block_start -= (long) WSIZE;

		for (n = 0; n < HASH_SIZE; n++) {
			m = head[n];
			head[n] = (Pos) (m >= WSIZE ? m - WSIZE : NIL);
		}
		for (n = 0; n < WSIZE; n++) {
			m = prev[n];
			prev[n] = (Pos) (m >= WSIZE ? m - WSIZE : NIL);
			/* If n is not on any hash chain, prev[n] is garbage but
			 * its value will never be used.
			 */
		}
		more += WSIZE;
	}
	/* At this point, more >= 2 */
	if (!eofile) {
		n = read_buf((char *) window + strstart + lookahead, more);
		if (n == 0 || n == (unsigned) EOF) {
			eofile = 1;
		} else {
			lookahead += n;
		}
	}
}

/* ===========================================================================
 * Flush the current block, with given end-of-file flag.
 * IN assertion: strstart is set to the end of the current match.
 */
#define FLUSH_BLOCK(eof) \
   flush_block(block_start >= 0L ? (char*)&window[(unsigned)block_start] : \
                (char*)NULL, (long)strstart - block_start, (eof))

/* ===========================================================================
 * Same as above, but achieves better compression. We use a lazy
 * evaluation for matches: a match is finally adopted only if there is
 * no better match at the next window position.
 */
static ulg deflate()
{
	IPos hash_head;				/* head of hash chain */
	IPos prev_match;			/* previous match */
	int flush;					/* set if current block must be flushed */
	int match_available = 0;	/* set if previous match exists */
	register unsigned match_length = MIN_MATCH - 1;	/* length of best match */

	/* Process the input block. */
	while (lookahead != 0) {
		/* Insert the string window[strstart .. strstart+2] in the
		 * dictionary, and set hash_head to the head of the hash chain:
		 */
		INSERT_STRING(strstart, hash_head);

		/* Find the longest match, discarding those <= prev_length.
		 */
		prev_length = match_length, prev_match = match_start;
		match_length = MIN_MATCH - 1;

		if (hash_head != NIL && prev_length < max_lazy_match &&
			strstart - hash_head <= MAX_DIST) {
			/* To simplify the code, we prevent matches with the string
			 * of window index 0 (in particular we have to avoid a match
			 * of the string with itself at the start of the input file).
			 */
			match_length = longest_match(hash_head);
			/* longest_match() sets match_start */
			if (match_length > lookahead)
				match_length = lookahead;

			/* Ignore a length 3 match if it is too distant: */
			if (match_length == MIN_MATCH
				&& strstart - match_start > TOO_FAR) {
				/* If prev_match is also MIN_MATCH, match_start is garbage
				 * but we will ignore the current match anyway.
				 */
				match_length--;
			}
		}
		/* If there was a match at the previous step and the current
		 * match is not better, output the previous match:
		 */
		if (prev_length >= MIN_MATCH && match_length <= prev_length) {

			check_match(strstart - 1, prev_match, prev_length);

			flush =
				ct_tally(strstart - 1 - prev_match,
						 prev_length - MIN_MATCH);

			/* Insert in hash table all strings up to the end of the match.
			 * strstart-1 and strstart are already inserted.
			 */
			lookahead -= prev_length - 1;
			prev_length -= 2;
			do {
				strstart++;
				INSERT_STRING(strstart, hash_head);
				/* strstart never exceeds WSIZE-MAX_MATCH, so there are
				 * always MIN_MATCH bytes ahead. If lookahead < MIN_MATCH
				 * these bytes are garbage, but it does not matter since the
				 * next lookahead bytes will always be emitted as literals.
				 */
			} while (--prev_length != 0);
			match_available = 0;
			match_length = MIN_MATCH - 1;
			strstart++;
			if (flush)
				FLUSH_BLOCK(0), block_start = strstart;

		} else if (match_available) {
			/* If there was no match at the previous position, output a
			 * single literal. If there was a match but the current match
			 * is longer, truncate the previous match to a single literal.
			 */
			Tracevv((stderr, "%c", window[strstart - 1]));
			if (ct_tally(0, window[strstart - 1])) {
				FLUSH_BLOCK(0), block_start = strstart;
			}
			strstart++;
			lookahead--;
		} else {
			/* There is no previous match to compare with, wait for
			 * the next step to decide.
			 */
			match_available = 1;
			strstart++;
			lookahead--;
		}
		Assert(strstart <= isize && lookahead <= isize, "a bit too far");

		/* Make sure that we always have enough lookahead, except
		 * at the end of the input file. We need MAX_MATCH bytes
		 * for the next match, plus MIN_MATCH bytes to insert the
		 * string following the next match.
		 */
		while (lookahead < MIN_LOOKAHEAD && !eofile)
			fill_window();
	}
	if (match_available)
		ct_tally(0, window[strstart - 1]);

	return FLUSH_BLOCK(1);		/* eof */
}

/* gzip (GNU zip) -- compress files with zip algorithm and 'compress' interface
 * Copyright (C) 1992-1993 Jean-loup Gailly
 * The unzip code was written and put in the public domain by Mark Adler.
 * Portions of the lzw code are derived from the public domain 'compress'
 * written by Spencer Thomas, Joe Orost, James Woods, Jim McKie, Steve Davies,
 * Ken Turkowski, Dave Mack and Peter Jannesen.
 *
 * See the license_msg below and the file COPYING for the software license.
 * See the file algorithm.doc for the compression algorithms and file formats.
 */

/* Compress files with zip algorithm and 'compress' interface.
 * See usage() and help() functions below for all options.
 * Outputs:
 *        file.gz:   compressed file with same mode, owner, and utimes
 *     or stdout with -c option or if stdin used as input.
 * If the output file name had to be truncated, the original name is kept
 * in the compressed file.
 */

		/* configuration */

typedef struct dirent dir_type;

typedef RETSIGTYPE(*sig_type) (int);

/* ======================================================================== */
// int main (argc, argv)
//    int argc;
//    char **argv;
int gzip_main(int argc, char **argv)
{
	int result;
	int inFileNum;
	int outFileNum;
	struct stat statBuf;
	char *delFileName;
	int tostdout = 0;
	int force = 0;
	int opt;

	while ((opt = getopt(argc, argv, "cf123456789dq")) != -1) {
		switch (opt) {
		case 'c':
			tostdout = 1;
			break;
		case 'f':
			force = 1;
			break;
		/* Ignore 1-9 (compression level) options */
		case '1': case '2': case '3': case '4': case '5':
		case '6': case '7': case '8': case '9':
			break;
		case 'q':
			break;
#ifdef CONFIG_GUNZIP
		case 'd':
			optind = 1;
			return gunzip_main(argc, argv);
#endif
		default:
			show_usage();
		}
	}

	foreground = signal(SIGINT, SIG_IGN) != SIG_IGN;