Adding upstream version 2.0.13.upstream/2.0.13upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 759 insertions, 0 deletions

diff --git a/usr/gzip/deflate.c b/usr/gzip/deflate.c
new file mode 100644
index 0000000..1db44fd
--- /dev/null
+++ b/usr/gzip/deflate.c
@@ -0,0 +1,759 @@
+/* deflate.c -- compress data using the deflation algorithm
+ * Copyright (C) 1992-1993 Jean-loup Gailly
+ * This is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License, see the file COPYING.
+ */
+
+/*
+ *  PURPOSE
+ *
+ *      Identify new text as repetitions of old text within a fixed-
+ *      length sliding window trailing behind the new text.
+ *
+ *  DISCUSSION
+ *
+ *      The "deflation" process depends on being able to identify portions
+ *      of the input text which are identical to earlier input (within a
+ *      sliding window trailing behind the input currently being processed).
+ *
+ *      The most straightforward technique turns out to be the fastest for
+ *      most input files: try all possible matches and select the longest.
+ *      The key feature of this algorithm is that insertions into the string
+ *      dictionary are very simple and thus fast, and deletions are avoided
+ *      completely. Insertions are performed at each input character, whereas
+ *      string matches are performed only when the previous match ends. So it
+ *      is preferable to spend more time in matches to allow very fast string
+ *      insertions and avoid deletions. The matching algorithm for small
+ *      strings is inspired from that of Rabin & Karp. A brute force approach
+ *      is used to find longer strings when a small match has been found.
+ *      A similar algorithm is used in comic (by Jan-Mark Wams) and freeze
+ *      (by Leonid Broukhis).
+ *         A previous version of this file used a more sophisticated algorithm
+ *      (by Fiala and Greene) which is guaranteed to run in linear amortized
+ *      time, but has a larger average cost, uses more memory and is patented.
+ *      However the F&G algorithm may be faster for some highly redundant
+ *      files if the parameter max_chain_length (described below) is too large.
+ *
+ *  ACKNOWLEDGEMENTS
+ *
+ *      The idea of lazy evaluation of matches is due to Jan-Mark Wams, and
+ *      I found it in 'freeze' written by Leonid Broukhis.
+ *      Thanks to many info-zippers for bug reports and testing.
+ *
+ *  REFERENCES
+ *
+ *      APPNOTE.TXT documentation file in PKZIP 1.93a distribution.
+ *
+ *      A description of the Rabin and Karp algorithm is given in the book
+ *         "Algorithms" by R. Sedgewick, Addison-Wesley, p252.
+ *
+ *      Fiala,E.R., and Greene,D.H.
+ *         Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595
+ *
+ *  INTERFACE
+ *
+ *      void lm_init (int pack_level, ush *flags)
+ *          Initialize the "longest match" routines for a new file
+ *
+ *      ulg deflate (void)
+ *          Processes a new input file and return its compressed length. Sets
+ *          the compressed length, crc, deflate flags and internal file
+ *          attributes.
+ */
+
+#include <stdio.h>
+
+#include "tailor.h"
+#include "gzip.h"
+
+#ifdef RCSID
+static char rcsid[] = "$Id: deflate.c,v 1.1 2002/08/18 00:59:21 hpa Exp $";
+#endif
+
+/* ===========================================================================
+ * Configuration parameters
+ */
+
+/* Compile with MEDIUM_MEM to reduce the memory requirements or
+ * with SMALL_MEM to use as little memory as possible. Use BIG_MEM if the
+ * entire input file can be held in memory (not possible on 16 bit systems).
+ * Warning: defining these symbols affects HASH_BITS (see below) and thus
+ * affects the compression ratio. The compressed output
+ * is still correct, and might even be smaller in some cases.
+ */
+
+#ifdef SMALL_MEM
+#   define HASH_BITS  13  /* Number of bits used to hash strings */
+#endif
+#ifdef MEDIUM_MEM
+#   define HASH_BITS  14
+#endif
+#ifndef HASH_BITS
+#   define HASH_BITS  15
+   /* For portability to 16 bit machines, do not use values above 15. */
+#endif
+
+/* To save space (see unlzw.c), we overlay prev+head with tab_prefix and
+ * window with tab_suffix. Check that we can do this:
+ */
+#if (WSIZE<<1) > (1<<BITS)
+   error: cannot overlay window with tab_suffix and prev with tab_prefix0
+#endif
+#if HASH_BITS > BITS-1
+   error: cannot overlay head with tab_prefix1
+#endif
+
+#define HASH_SIZE (unsigned)(1<<HASH_BITS)
+#define HASH_MASK (HASH_SIZE-1)
+#define WMASK     (WSIZE-1)
+/* HASH_SIZE and WSIZE must be powers of two */
+
+#define NIL 0
+/* Tail of hash chains */
+
+#define FAST 4
+#define SLOW 2
+/* speed options for the general purpose bit flag */
+
+#ifndef TOO_FAR
+#  define TOO_FAR 4096
+#endif
+/* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
+
+/* ===========================================================================
+ * Local data used by the "longest match" routines.
+ */
+
+typedef ush Pos;
+typedef unsigned IPos;
+/* A Pos is an index in the character window. We use short instead of int to
+ * save space in the various tables. IPos is used only for parameter passing.
+ */
+
+/* DECLARE(uch, window, 2L*WSIZE); */
+/* Sliding window. Input bytes are read into the second half of the window,
+ * and move to the first half later to keep a dictionary of at least WSIZE
+ * bytes. With this organization, matches are limited to a distance of
+ * WSIZE-MAX_MATCH bytes, but this ensures that IO is always
+ * performed with a length multiple of the block size. Also, it limits
+ * the window size to 64K, which is quite useful on MSDOS.
+ * To do: limit the window size to WSIZE+BSZ if SMALL_MEM (the code would
+ * be less efficient).
+ */
+
+/* DECLARE(Pos, prev, WSIZE); */
+/* Link to older string with same hash index. To limit the size of this
+ * array to 64K, this link is maintained only for the last 32K strings.
+ * An index in this array is thus a window index modulo 32K.
+ */
+
+/* DECLARE(Pos, head, 1<<HASH_BITS); */
+/* Heads of the hash chains or NIL. */
+
+ulg window_size = (ulg)2*WSIZE;
+/* window size, 2*WSIZE except for MMAP or BIG_MEM, where it is the
+ * input file length plus MIN_LOOKAHEAD.
+ */
+
+long block_start;
+/* window position at the beginning of the current output block. Gets
+ * negative when the window is moved backwards.
+ */
+
+local unsigned ins_h;  /* hash index of string to be inserted */
+
+#define H_SHIFT  ((HASH_BITS+MIN_MATCH-1)/MIN_MATCH)
+/* Number of bits by which ins_h and del_h must be shifted at each
+ * input step. It must be such that after MIN_MATCH steps, the oldest
+ * byte no longer takes part in the hash key, that is:
+ *   H_SHIFT * MIN_MATCH >= HASH_BITS
+ */
+
+unsigned int prev_length;
+/* Length of the best match at previous step. Matches not greater than this
+ * are discarded. This is used in the lazy match evaluation.
+ */
+
+      unsigned      strstart;      /* start of string to insert */
+      unsigned      match_start;   /* start of matching string */
+local int           eofile;        /* flag set at end of input file */
+local unsigned      lookahead;     /* number of valid bytes ahead in window */
+
+unsigned max_chain_length;
+/* To speed up deflation, hash chains are never searched beyond this length.
+ * A higher limit improves compression ratio but degrades the speed.
+ */
+
+local unsigned int max_lazy_match;
+/* Attempt to find a better match only when the current match is strictly
+ * smaller than this value. This mechanism is used only for compression
+ * levels >= 4.
+ */
+#define max_insert_length  max_lazy_match
+/* Insert new strings in the hash table only if the match length
+ * is not greater than this length. This saves time but degrades compression.
+ * max_insert_length is used only for compression levels <= 3.
+ */
+
+local int compr_level;
+/* compression level (1..9) */
+
+unsigned good_match;
+/* Use a faster search when the previous match is longer than this */
+
+
+/* Values for max_lazy_match, good_match and max_chain_length, depending on
+ * the desired pack level (0..9). The values given below have been tuned to
+ * exclude worst case performance for pathological files. Better values may be
+ * found for specific files.
+ */
+
+typedef struct config {
+   ush good_length; /* reduce lazy search above this match length */
+   ush max_lazy;    /* do not perform lazy search above this match length */
+   ush nice_length; /* quit search above this match length */
+   ush max_chain;
+} config;
+
+#ifdef  FULL_SEARCH
+# define nice_match MAX_MATCH
+#else
+  int nice_match; /* Stop searching when current match exceeds this */
+#endif
+
+local config configuration_table[10] = {
+/*      good lazy nice chain */
+/* 0 */ {0,    0,  0,    0},  /* store only */
+/* 1 */ {4,    4,  8,    4},  /* maximum speed, no lazy matches */
+/* 2 */ {4,    5, 16,    8},
+/* 3 */ {4,    6, 32,   32},
+
+/* 4 */ {4,    4, 16,   16},  /* lazy matches */
+/* 5 */ {8,   16, 32,   32},
+/* 6 */ {8,   16, 128, 128},
+/* 7 */ {8,   32, 128, 256},
+/* 8 */ {32, 128, 258, 1024},
+/* 9 */ {32, 258, 258, 4096}}; /* maximum compression */
+
+/* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
+ * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
+ * meaning.
+ */
+
+#define EQUAL 0
+/* result of memcmp for equal strings */
+
+/* ===========================================================================
+ *  Prototypes for local functions.
+ */
+local void fill_window   OF((void));
+local ulg deflate_fast   OF((void));
+
+      int  longest_match OF((IPos cur_match));
+#ifdef ASMV
+      void match_init OF((void)); /* asm code initialization */
+#endif
+
+#ifdef DEBUG
+local  void check_match OF((IPos start, IPos match, int length));
+#endif
+
+/* ===========================================================================
+ * Update a hash value with the given input byte
+ * IN  assertion: all calls to to UPDATE_HASH are made with consecutive
+ *    input characters, so that a running hash key can be computed from the
+ *    previous key instead of complete recalculation each time.
+ */
+#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
+ */
+void lm_init (pack_level, flags)
+    int pack_level; /* 0: store, 1: best speed, 9: best compression */
+    ush *flags;     /* general purpose bit flag */
+{
+    register unsigned j;
+
+    if (pack_level < 1 || pack_level > 9) error("bad pack level");
+    compr_level = pack_level;
+
+    /* Initialize the hash table. */
+    memzero((char*)head, HASH_SIZE*sizeof(*head));
+
+    /* prev will be initialized on the fly */
+
+    /* Set the default configuration parameters:
+     */
+    max_lazy_match   = configuration_table[pack_level].max_lazy;
+    good_match       = configuration_table[pack_level].good_length;
+#ifndef FULL_SEARCH
+    nice_match       = configuration_table[pack_level].nice_length;
+#endif
+    max_chain_length = configuration_table[pack_level].max_chain;
+    if (pack_level == 1) {
+       *flags |= FAST;
+    } else if (pack_level == 9) {
+       *flags |= SLOW;
+    }
+    /* ??? reduce max_chain_length for binary files */
+
+    strstart = 0;
+    block_start = 0L;
+#ifdef ASMV
+    match_init(); /* initialize the asm code */
+#endif
+
+    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
+ */
+#ifndef ASMV
+/* 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.
+ */
+int longest_match(cur_match)
+    IPos cur_match;                             /* current 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
+
+#ifdef UNALIGNED_OK
+    /* Compare two bytes at a time. Note: this is not always beneficial.
+     * Try with and without -DUNALIGNED_OK to check.
+     */
+    register uch *strend = window + strstart + MAX_MATCH - 1;
+    register ush scan_start = *(ush*)scan;
+    register ush scan_end   = *(ush*)(scan+best_len-1);
+#else
+    register uch *strend = window + strstart + MAX_MATCH;
+    register uch scan_end1  = scan[best_len-1];
+    register uch scan_end   = scan[best_len];
+#endif
+
+    /* 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 (defined(UNALIGNED_OK) && MAX_MATCH == 258)
+        /* This code assumes sizeof(unsigned short) == 2. Do not use
+         * UNALIGNED_OK if your compiler uses a different size.
+         */
+        if (*(ush*)(match+best_len-1) != scan_end ||
+            *(ush*)match != scan_start) continue;
+
+        /* 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. Compare 2 bytes at a time at
+         * strstart+3, +5, ... up to strstart+257. We check for insufficient
+         * lookahead only every 4th comparison; the 128th check will be made
+         * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
+         * necessary to put more guard bytes at the end of the window, or
+         * to check more often for insufficient lookahead.
+         */
+        scan++, match++;
+        do {
+        } while (*(ush*)(scan+=2) == *(ush*)(match+=2) &&
+                 *(ush*)(scan+=2) == *(ush*)(match+=2) &&
+                 *(ush*)(scan+=2) == *(ush*)(match+=2) &&
+                 *(ush*)(scan+=2) == *(ush*)(match+=2) &&
+                 scan < strend);
+        /* The funny "do {}" generates better code on most compilers */
+
+        /* Here, scan <= window+strstart+257 */
+        Assert(scan <= window+(unsigned)(window_size-1), "wild scan");
+        if (*scan == *match) scan++;
+
+        len = (MAX_MATCH - 1) - (int)(strend-scan);
+        scan = strend - (MAX_MATCH-1);
+
+#else /* UNALIGNED_OK */
+
+        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;
+
+#endif /* UNALIGNED_OK */
+
+        if (len > best_len) {
+            match_start = cur_match;
+            best_len = len;
+            if (len >= nice_match) break;
+#ifdef UNALIGNED_OK
+            scan_end = *(ush*)(scan+best_len-1);
+#else
+            scan_end1  = scan[best_len-1];
+            scan_end   = scan[best_len];
+#endif
+        }
+    } while ((cur_match = prev[cur_match & WMASK]) > limit
+	     && --chain_length != 0);
+
+    return best_len;
+}
+#endif /* ASMV */
+
+#ifdef DEBUG
+/* ===========================================================================
+ * Check that the match at match_start is indeed a match.
+ */
+local void check_match(start, match, length)
+    IPos start, 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("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).
+ */
+local 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))
+
+/* ===========================================================================
+ * Processes a new input file and return its compressed length. This
+ * function does not perform lazy evaluationof matches and inserts
+ * new strings in the dictionary only for unmatched strings or for short
+ * matches. It is used only for the fast compression options.
+ */
+local ulg deflate_fast()
+{
+    IPos hash_head; /* head of the hash chain */
+    int flush;      /* set if current block must be flushed */
+    unsigned match_length = 0;  /* length of best match */
+
+    prev_length = MIN_MATCH-1;
+    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.
+         * At this point we have always match_length < MIN_MATCH
+         */
+        if (hash_head != NIL && 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;
+        }
+        if (match_length >= MIN_MATCH) {
+            check_match(strstart, match_start, match_length);
+
+            flush = ct_tally(strstart-match_start, match_length - MIN_MATCH);
+
+            lookahead -= match_length;
+
+	    /* Insert new strings in the hash table only if the match length
+             * is not too large. This saves time but degrades compression.
+             */
+            if (match_length <= max_insert_length) {
+                match_length--; /* string at strstart already in hash table */
+                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 be emitted as literals.
+                     */
+                } while (--match_length != 0);
+	        strstart++;
+            } else {
+	        strstart += match_length;
+	        match_length = 0;
+	        ins_h = window[strstart];
+	        UPDATE_HASH(ins_h, window[strstart+1]);
+#if MIN_MATCH != 3
+                Call UPDATE_HASH() MIN_MATCH-3 more times
+#endif
+            }
+        } else {
+            /* No match, output a literal byte */
+            Tracevv((stderr,"%c",window[strstart]));
+            flush = ct_tally (0, window[strstart]);
+            lookahead--;
+	    strstart++;
+        }
+        if (flush) FLUSH_BLOCK(0), block_start = strstart;
+
+        /* 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();
+
+    }
+    return FLUSH_BLOCK(1); /* 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.
+ */
+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 */
+#ifdef DEBUG
+    extern long isize;        /* byte length of input file, for debug only */
+#endif
+
+    if (compr_level <= 3) return deflate_fast(); /* optimized for speed */
+
+    /* 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 */
+}