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diff --git a/isys/gzlib/trees.c b/isys/gzlib/trees.c
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+/* trees.c -- output deflated data using Huffman coding
+ * 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
+ *
+ *      Encode various sets of source values using variable-length
+ *      binary code trees.
+ *
+ *  DISCUSSION
+ *
+ *      The PKZIP "deflation" process uses several Huffman trees. The more
+ *      common source values are represented by shorter bit sequences.
+ *
+ *      Each code tree is stored in the ZIP file in a compressed form
+ *      which is itself a Huffman encoding of the lengths of
+ *      all the code strings (in ascending order by source values).
+ *      The actual code strings are reconstructed from the lengths in
+ *      the UNZIP process, as described in the "application note"
+ *      (APPNOTE.TXT) distributed as part of PKWARE's PKZIP program.
+ *
+ *  REFERENCES
+ *
+ *      Lynch, Thomas J.
+ *          Data Compression:  Techniques and Applications, pp. 53-55.
+ *          Lifetime Learning Publications, 1985.  ISBN 0-534-03418-7.
+ *
+ *      Storer, James A.
+ *          Data Compression:  Methods and Theory, pp. 49-50.
+ *          Computer Science Press, 1988.  ISBN 0-7167-8156-5.
+ *
+ *      Sedgewick, R.
+ *          Algorithms, p290.
+ *          Addison-Wesley, 1983. ISBN 0-201-06672-6.
+ *
+ *  INTERFACE
+ *
+ *      void ct_init (ush *attr, int *methodp)
+ *          Allocate the match buffer, initialize the various tables and save
+ *          the location of the internal file attribute (ascii/binary) and
+ *          method (DEFLATE/STORE)
+ *
+ *      void ct_tally (int dist, int lc);
+ *          Save the match info and tally the frequency counts.
+ *
+ *      off_t flush_block (char *buf, ulg stored_len, int eof)
+ *          Determine the best encoding for the current block: dynamic trees,
+ *          static trees or store, and output the encoded block to the zip
+ *          file. Returns the total compressed length for the file so far.
+ *
+ */
+
+#include <config.h>
+#include <ctype.h>
+
+#include "tailor.h"
+#include "gzip.h"
+
+#ifdef RCSID
+static char rcsid[] = "$Id$";
+#endif
+
+/* ===========================================================================
+ * Constants
+ */
+
+#define MAX_BITS 15
+/* All codes must not exceed MAX_BITS bits */
+
+#define MAX_BL_BITS 7
+/* Bit length codes must not exceed MAX_BL_BITS bits */
+
+#define LENGTH_CODES 29
+/* number of length codes, not counting the special END_BLOCK code */
+
+#define LITERALS  256
+/* number of literal bytes 0..255 */
+
+#define END_BLOCK 256
+/* end of block literal code */
+
+#define L_CODES (LITERALS+1+LENGTH_CODES)
+/* number of Literal or Length codes, including the END_BLOCK code */
+
+#define D_CODES   30
+/* number of distance codes */
+
+#define BL_CODES  19
+/* number of codes used to transfer the bit lengths */
+
+
+local int near extra_lbits[LENGTH_CODES] /* extra bits for each length code */
+   = {0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,0};
+
+local int near extra_dbits[D_CODES] /* extra bits for each distance code */
+   = {0,0,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13};
+
+local int near extra_blbits[BL_CODES]/* extra bits for each bit length code */
+   = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
+
+#define STORED_BLOCK 0
+#define STATIC_TREES 1
+#define DYN_TREES    2
+/* The three kinds of block type */
+
+#ifndef LIT_BUFSIZE
+#  ifdef SMALL_MEM
+#    define LIT_BUFSIZE  0x2000
+#  else
+#  ifdef MEDIUM_MEM
+#    define LIT_BUFSIZE  0x4000
+#  else
+#    define LIT_BUFSIZE  0x8000
+#  endif
+#  endif
+#endif
+#ifndef DIST_BUFSIZE
+#  define DIST_BUFSIZE  LIT_BUFSIZE
+#endif
+/* Sizes of match buffers for literals/lengths and distances.  There are
+ * 4 reasons for limiting LIT_BUFSIZE to 64K:
+ *   - frequencies can be kept in 16 bit counters
+ *   - if compression is not successful for the first block, all input data is
+ *     still in the window so we can still emit a stored block even when input
+ *     comes from standard input.  (This can also be done for all blocks if
+ *     LIT_BUFSIZE is not greater than 32K.)
+ *   - if compression is not successful for a file smaller than 64K, we can
+ *     even emit a stored file instead of a stored block (saving 5 bytes).
+ *   - creating new Huffman trees less frequently may not provide fast
+ *     adaptation to changes in the input data statistics. (Take for
+ *     example a binary file with poorly compressible code followed by
+ *     a highly compressible string table.) Smaller buffer sizes give
+ *     fast adaptation but have of course the overhead of transmitting trees
+ *     more frequently.
+ *   - I can't count above 4
+ * The current code is general and allows DIST_BUFSIZE < LIT_BUFSIZE (to save
+ * memory at the expense of compression). Some optimizations would be possible
+ * if we rely on DIST_BUFSIZE == LIT_BUFSIZE.
+ */
+#if LIT_BUFSIZE > INBUFSIZ
+    error cannot overlay l_buf and inbuf
+#endif
+
+#define REP_3_6      16
+/* repeat previous bit length 3-6 times (2 bits of repeat count) */
+
+#define REPZ_3_10    17
+/* repeat a zero length 3-10 times  (3 bits of repeat count) */
+
+#define REPZ_11_138  18
+/* repeat a zero length 11-138 times  (7 bits of repeat count) */
+
+/* ===========================================================================
+ * Local data
+ */
+
+/* Data structure describing a single value and its code string. */
+typedef struct ct_data {
+    union {
+        ush  freq;       /* frequency count */
+        ush  code;       /* bit string */
+    } fc;
+    union {
+        ush  dad;        /* father node in Huffman tree */
+        ush  len;        /* length of bit string */
+    } dl;
+} ct_data;
+
+#define Freq fc.freq
+#define Code fc.code
+#define Dad  dl.dad
+#define Len  dl.len
+
+#define HEAP_SIZE (2*L_CODES+1)
+/* maximum heap size */
+
+local ct_data near dyn_ltree[HEAP_SIZE];   /* literal and length tree */
+local ct_data near dyn_dtree[2*D_CODES+1]; /* distance tree */
+
+local ct_data near static_ltree[L_CODES+2];
+/* The static literal tree. Since the bit lengths are imposed, there is no
+ * need for the L_CODES extra codes used during heap construction. However
+ * The codes 286 and 287 are needed to build a canonical tree (see ct_init
+ * below).
+ */
+
+local ct_data near static_dtree[D_CODES];
+/* The static distance tree. (Actually a trivial tree since all codes use
+ * 5 bits.)
+ */
+
+local ct_data near bl_tree[2*BL_CODES+1];
+/* Huffman tree for the bit lengths */
+
+typedef struct tree_desc {
+    ct_data near *dyn_tree;      /* the dynamic tree */
+    ct_data near *static_tree;   /* corresponding static tree or NULL */
+    int     near *extra_bits;    /* extra bits for each code or NULL */
+    int     extra_base;          /* base index for extra_bits */
+    int     elems;               /* max number of elements in the tree */
+    int     max_length;          /* max bit length for the codes */
+    int     max_code;            /* largest code with non zero frequency */
+} tree_desc;
+
+local tree_desc near l_desc =
+{dyn_ltree, static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS, 0};
+
+local tree_desc near d_desc =
+{dyn_dtree, static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS, 0};
+
+local tree_desc near bl_desc =
+{bl_tree, (ct_data near *)0, extra_blbits, 0,      BL_CODES, MAX_BL_BITS, 0};
+
+
+local ush near bl_count[MAX_BITS+1];
+/* number of codes at each bit length for an optimal tree */
+
+local uch near bl_order[BL_CODES]
+   = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
+/* The lengths of the bit length codes are sent in order of decreasing
+ * probability, to avoid transmitting the lengths for unused bit length codes.
+ */
+
+local int near heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
+local int heap_len;               /* number of elements in the heap */
+local int heap_max;               /* element of largest frequency */
+/* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
+ * The same heap array is used to build all trees.
+ */
+
+local uch near depth[2*L_CODES+1];
+/* Depth of each subtree used as tie breaker for trees of equal frequency */
+
+local uch length_code[MAX_MATCH-MIN_MATCH+1];
+/* length code for each normalized match length (0 == MIN_MATCH) */
+
+local uch dist_code[512];
+/* distance codes. The first 256 values correspond to the distances
+ * 3 .. 258, the last 256 values correspond to the top 8 bits of
+ * the 15 bit distances.
+ */
+
+local int near base_length[LENGTH_CODES];
+/* First normalized length for each code (0 = MIN_MATCH) */
+
+local int near base_dist[D_CODES];
+/* First normalized distance for each code (0 = distance of 1) */
+
+#define l_buf inbuf
+/* DECLARE(uch, l_buf, LIT_BUFSIZE);  buffer for literals or lengths */
+
+/* DECLARE(ush, d_buf, DIST_BUFSIZE); buffer for distances */
+
+local uch near flag_buf[(LIT_BUFSIZE/8)];
+/* flag_buf is a bit array distinguishing literals from lengths in
+ * l_buf, thus indicating the presence or absence of a distance.
+ */
+
+local unsigned last_lit;    /* running index in l_buf */
+local unsigned last_dist;   /* running index in d_buf */
+local unsigned last_flags;  /* running index in flag_buf */
+local uch flags;            /* current flags not yet saved in flag_buf */
+local uch flag_bit;         /* current bit used in flags */
+/* bits are filled in flags starting at bit 0 (least significant).
+ * Note: these flags are overkill in the current code since we don't
+ * take advantage of DIST_BUFSIZE == LIT_BUFSIZE.
+ */
+
+local ulg opt_len;        /* bit length of current block with optimal trees */
+local ulg static_len;     /* bit length of current block with static trees */
+
+local off_t compressed_len; /* total bit length of compressed file */
+
+local off_t input_len;      /* total byte length of input file */
+/* input_len is for debugging only since we can get it by other means. */
+
+ush *file_type;        /* pointer to UNKNOWN, BINARY or ASCII */
+int *file_method;      /* pointer to DEFLATE or STORE */
+
+#ifdef DEBUG
+extern off_t bits_sent;  /* bit length of the compressed data */
+#endif
+
+extern long block_start;       /* window offset of current block */
+extern unsigned near strstart; /* window offset of current string */
+
+/* ===========================================================================
+ * Local (static) routines in this file.
+ */
+
+local void init_block     OF((void));
+local void pqdownheap     OF((ct_data near *tree, int k));
+local void gen_bitlen     OF((tree_desc near *desc));
+local void gen_codes      OF((ct_data near *tree, int max_code));
+local void build_tree     OF((tree_desc near *desc));
+local void scan_tree      OF((ct_data near *tree, int max_code));
+local void send_tree      OF((ct_data near *tree, int max_code));
+local int  build_bl_tree  OF((void));
+local void send_all_trees OF((int lcodes, int dcodes, int blcodes));
+local void compress_block OF((ct_data near *ltree, ct_data near *dtree));
+local void set_file_type  OF((void));
+
+
+#ifndef DEBUG
+#  define send_code(c, tree) send_bits(tree[c].Code, tree[c].Len)
+   /* Send a code of the given tree. c and tree must not have side effects */
+
+#else /* DEBUG */
+#  define send_code(c, tree) \
+     { send_bits(tree[c].Code, tree[c].Len); }
+#endif
+
+#define d_code(dist) \
+   ((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)])
+/* Mapping from a distance to a distance code. dist is the distance - 1 and
+ * must not have side effects. dist_code[256] and dist_code[257] are never
+ * used.
+ */
+
+#define MAX(a,b) (a >= b ? a : b)
+/* the arguments must not have side effects */
+
+/* ===========================================================================
+ * Allocate the match buffer, initialize the various tables and save the
+ * location of the internal file attribute (ascii/binary) and method
+ * (DEFLATE/STORE).
+ */
+void ct_init(attr, methodp)
+    ush  *attr;   /* pointer to internal file attribute */
+    int  *methodp; /* pointer to compression method */
+{
+    int n;        /* iterates over tree elements */
+    int bits;     /* bit counter */
+    int length;   /* length value */
+    int code;     /* code value */
+    int dist;     /* distance index */
+
+    file_type = attr;
+    file_method = methodp;
+    compressed_len = input_len = 0L;
+        
+    if (static_dtree[0].Len != 0) return; /* ct_init already called */
+
+    /* Initialize the mapping length (0..255) -> length code (0..28) */
+    length = 0;
+    for (code = 0; code < LENGTH_CODES-1; code++) {
+        base_length[code] = length;
+        for (n = 0; n < (1<<extra_lbits[code]); n++) {
+            length_code[length++] = (uch)code;
+        }
+    }
+    Assert (length == 256, "ct_init: length != 256");
+    /* Note that the length 255 (match length 258) can be represented
+     * in two different ways: code 284 + 5 bits or code 285, so we
+     * overwrite length_code[255] to use the best encoding:
+     */
+    length_code[length-1] = (uch)code;
+
+    /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
+    dist = 0;
+    for (code = 0 ; code < 16; code++) {
+        base_dist[code] = dist;
+        for (n = 0; n < (1<<extra_dbits[code]); n++) {
+            dist_code[dist++] = (uch)code;
+        }
+    }
+    Assert (dist == 256, "ct_init: dist != 256");
+    dist >>= 7; /* from now on, all distances are divided by 128 */
+    for ( ; code < D_CODES; code++) {
+        base_dist[code] = dist << 7;
+        for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
+            dist_code[256 + dist++] = (uch)code;
+        }
+    }
+    Assert (dist == 256, "ct_init: 256+dist != 512");
+
+    /* Construct the codes of the static literal tree */
+    for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
+    n = 0;
+    while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
+    while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
+    while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
+    while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
+    /* Codes 286 and 287 do not exist, but we must include them in the
+     * tree construction to get a canonical Huffman tree (longest code
+     * all ones)
+     */
+    gen_codes((ct_data near *)static_ltree, L_CODES+1);
+
+    /* The static distance tree is trivial: */
+    for (n = 0; n < D_CODES; n++) {
+        static_dtree[n].Len = 5;
+        static_dtree[n].Code = bi_reverse(n, 5);
+    }
+
+    /* Initialize the first block of the first file: */
+    init_block();
+}
+
+/* ===========================================================================
+ * Initialize a new block.
+ */
+local void init_block()
+{
+    int n; /* iterates over tree elements */
+
+    /* Initialize the trees. */
+    for (n = 0; n < L_CODES;  n++) dyn_ltree[n].Freq = 0;
+    for (n = 0; n < D_CODES;  n++) dyn_dtree[n].Freq = 0;
+    for (n = 0; n < BL_CODES; n++) bl_tree[n].Freq = 0;
+
+    dyn_ltree[END_BLOCK].Freq = 1;
+    opt_len = static_len = 0L;
+    last_lit = last_dist = last_flags = 0;
+    flags = 0; flag_bit = 1;
+}
+
+#define SMALLEST 1
+/* Index within the heap array of least frequent node in the Huffman tree */
+
+
+/* ===========================================================================
+ * Remove the smallest element from the heap and recreate the heap with
+ * one less element. Updates heap and heap_len.
+ */
+#define pqremove(tree, top) \
+{\
+    top = heap[SMALLEST]; \
+    heap[SMALLEST] = heap[heap_len--]; \
+    pqdownheap(tree, SMALLEST); \
+}
+
+/* ===========================================================================
+ * Compares to subtrees, using the tree depth as tie breaker when
+ * the subtrees have equal frequency. This minimizes the worst case length.
+ */
+#define smaller(tree, n, m) \
+   (tree[n].Freq < tree[m].Freq || \
+   (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
+
+/* ===========================================================================
+ * Restore the heap property by moving down the tree starting at node k,
+ * exchanging a node with the smallest of its two sons if necessary, stopping
+ * when the heap property is re-established (each father smaller than its
+ * two sons).
+ */
+local void pqdownheap(tree, k)
+    ct_data near *tree;  /* the tree to restore */
+    int k;               /* node to move down */
+{
+    int v = heap[k];
+    int j = k << 1;  /* left son of k */
+    while (j <= heap_len) {
+        /* Set j to the smallest of the two sons: */
+        if (j < heap_len && smaller(tree, heap[j+1], heap[j])) j++;
+
+        /* Exit if v is smaller than both sons */
+        if (smaller(tree, v, heap[j])) break;
+
+        /* Exchange v with the smallest son */
+        heap[k] = heap[j];  k = j;
+
+        /* And continue down the tree, setting j to the left son of k */
+        j <<= 1;
+    }
+    heap[k] = v;
+}
+
+/* ===========================================================================
+ * Compute the optimal bit lengths for a tree and update the total bit length
+ * for the current block.
+ * IN assertion: the fields freq and dad are set, heap[heap_max] and
+ *    above are the tree nodes sorted by increasing frequency.
+ * OUT assertions: the field len is set to the optimal bit length, the
+ *     array bl_count contains the frequencies for each bit length.
+ *     The length opt_len is updated; static_len is also updated if stree is
+ *     not null.
+ */
+local void gen_bitlen(desc)
+    tree_desc near *desc; /* the tree descriptor */
+{
+    ct_data near *tree  = desc->dyn_tree;
+    int near *extra     = desc->extra_bits;
+    int base            = desc->extra_base;
+    int max_code        = desc->max_code;
+    int max_length      = desc->max_length;
+    ct_data near *stree = desc->static_tree;
+    int h;              /* heap index */
+    int n, m;           /* iterate over the tree elements */
+    int bits;           /* bit length */
+    int xbits;          /* extra bits */
+    ush f;              /* frequency */
+    int overflow = 0;   /* number of elements with bit length too large */
+
+    for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
+
+    /* In a first pass, compute the optimal bit lengths (which may
+     * overflow in the case of the bit length tree).
+     */
+    tree[heap[heap_max]].Len = 0; /* root of the heap */
+
+    for (h = heap_max+1; h < HEAP_SIZE; h++) {
+        n = heap[h];
+        bits = tree[tree[n].Dad].Len + 1;
+        if (bits > max_length) bits = max_length, overflow++;
+        tree[n].Len = (ush)bits;
+        /* We overwrite tree[n].Dad which is no longer needed */
+
+        if (n > max_code) continue; /* not a leaf node */
+
+        bl_count[bits]++;
+        xbits = 0;
+        if (n >= base) xbits = extra[n-base];
+        f = tree[n].Freq;
+        opt_len += (ulg)f * (bits + xbits);
+        if (stree) static_len += (ulg)f * (stree[n].Len + xbits);
+    }
+    if (overflow == 0) return;
+
+    Trace((stderr,"\nbit length overflow\n"));
+    /* This happens for example on obj2 and pic of the Calgary corpus */
+
+    /* Find the first bit length which could increase: */
+    do {
+        bits = max_length-1;
+        while (bl_count[bits] == 0) bits--;
+        bl_count[bits]--;      /* move one leaf down the tree */
+        bl_count[bits+1] += 2; /* move one overflow item as its brother */
+        bl_count[max_length]--;
+        /* The brother of the overflow item also moves one step up,
+         * but this does not affect bl_count[max_length]
+         */
+        overflow -= 2;
+    } while (overflow > 0);
+
+    /* Now recompute all bit lengths, scanning in increasing frequency.
+     * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
+     * lengths instead of fixing only the wrong ones. This idea is taken
+     * from 'ar' written by Haruhiko Okumura.)
+     */
+    for (bits = max_length; bits != 0; bits--) {
+        n = bl_count[bits];
+        while (n != 0) {
+            m = heap[--h];
+            if (m > max_code) continue;
+            if (tree[m].Len != (unsigned) bits) {
+                Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
+                opt_len += ((long)bits-(long)tree[m].Len)*(long)tree[m].Freq;
+                tree[m].Len = (ush)bits;
+            }
+            n--;
+        }
+    }
+}
+
+/* ===========================================================================
+ * Generate the codes for a given tree and bit counts (which need not be
+ * optimal).
+ * IN assertion: the array bl_count contains the bit length statistics for
+ * the given tree and the field len is set for all tree elements.
+ * OUT assertion: the field code is set for all tree elements of non
+ *     zero code length.
+ */
+local void gen_codes (tree, max_code)
+    ct_data near *tree;        /* the tree to decorate */
+    int max_code;              /* largest code with non zero frequency */
+{
+    ush next_code[MAX_BITS+1]; /* next code value for each bit length */
+    ush code = 0;              /* running code value */
+    int bits;                  /* bit index */
+    int n;                     /* code index */
+
+    /* The distribution counts are first used to generate the code values
+     * without bit reversal.
+     */
+    for (bits = 1; bits <= MAX_BITS; bits++) {
+        next_code[bits] = code = (code + bl_count[bits-1]) << 1;
+    }
+    /* Check that the bit counts in bl_count are consistent. The last code
+     * must be all ones.
+     */
+    Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
+            "inconsistent bit counts");
+    Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
+
+    for (n = 0;  n <= max_code; n++) {
+        int len = tree[n].Len;
+        if (len == 0) continue;
+        /* Now reverse the bits */
+        tree[n].Code = bi_reverse(next_code[len]++, len);
+
+        Tracec(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
+             n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
+    }
+}
+
+/* ===========================================================================
+ * Construct one Huffman tree and assigns the code bit strings and lengths.
+ * Update the total bit length for the current block.
+ * IN assertion: the field freq is set for all tree elements.
+ * OUT assertions: the fields len and code are set to the optimal bit length
+ *     and corresponding code. The length opt_len is updated; static_len is
+ *     also updated if stree is not null. The field max_code is set.
+ */
+local void build_tree(desc)
+    tree_desc near *desc; /* the tree descriptor */
+{
+    ct_data near *tree   = desc->dyn_tree;
+    ct_data near *stree  = desc->static_tree;
+    int elems            = desc->elems;
+    int n, m;          /* iterate over heap elements */
+    int max_code = -1; /* largest code with non zero frequency */
+    int node = elems;  /* next internal node of the tree */
+
+    /* Construct the initial heap, with least frequent element in
+     * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
+     * heap[0] is not used.
+     */
+    heap_len = 0, heap_max = HEAP_SIZE;
+
+    for (n = 0; n < elems; n++) {
+        if (tree[n].Freq != 0) {
+            heap[++heap_len] = max_code = n;
+            depth[n] = 0;
+        } else {
+            tree[n].Len = 0;
+        }
+    }
+
+    /* The pkzip format requires that at least one distance code exists,
+     * and that at least one bit should be sent even if there is only one
+     * possible code. So to avoid special checks later on we force at least
+     * two codes of non zero frequency.
+     */
+    while (heap_len < 2) {
+        int new = heap[++heap_len] = (max_code < 2 ? ++max_code : 0);
+        tree[new].Freq = 1;
+        depth[new] = 0;
+        opt_len--; if (stree) static_len -= stree[new].Len;
+        /* new is 0 or 1 so it does not have extra bits */
+    }
+    desc->max_code = max_code;
+
+    /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
+     * establish sub-heaps of increasing lengths:
+     */
+    for (n = heap_len/2; n >= 1; n--) pqdownheap(tree, n);
+
+    /* Construct the Huffman tree by repeatedly combining the least two
+     * frequent nodes.
+     */
+    do {
+        pqremove(tree, n);   /* n = node of least frequency */
+        m = heap[SMALLEST];  /* m = node of next least frequency */
+
+        heap[--heap_max] = n; /* keep the nodes sorted by frequency */
+        heap[--heap_max] = m;
+
+        /* Create a new node father of n and m */
+        tree[node].Freq = tree[n].Freq + tree[m].Freq;
+        depth[node] = (uch) (MAX(depth[n], depth[m]) + 1);
+        tree[n].Dad = tree[m].Dad = (ush)node;
+#ifdef DUMP_BL_TREE
+        if (tree == bl_tree) {
+            fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
+                    node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
+        }
+#endif
+        /* and insert the new node in the heap */
+        heap[SMALLEST] = node++;
+        pqdownheap(tree, SMALLEST);
+
+    } while (heap_len >= 2);
+
+    heap[--heap_max] = heap[SMALLEST];
+
+    /* At this point, the fields freq and dad are set. We can now
+     * generate the bit lengths.
+     */
+    gen_bitlen((tree_desc near *)desc);
+
+    /* The field len is now set, we can generate the bit codes */
+    gen_codes ((ct_data near *)tree, max_code);
+}
+
+/* ===========================================================================
+ * Scan a literal or distance tree to determine the frequencies of the codes
+ * in the bit length tree. Updates opt_len to take into account the repeat
+ * counts. (The contribution of the bit length codes will be added later
+ * during the construction of bl_tree.)
+ */
+local void scan_tree (tree, max_code)
+    ct_data near *tree; /* the tree to be scanned */
+    int max_code;       /* and its largest code of non zero frequency */
+{
+    int n;                     /* iterates over all tree elements */
+    int prevlen = -1;          /* last emitted length */
+    int curlen;                /* length of current code */
+    int nextlen = tree[0].Len; /* length of next code */
+    int count = 0;             /* repeat count of the current code */
+    int max_count = 7;         /* max repeat count */
+    int min_count = 4;         /* min repeat count */
+
+    if (nextlen == 0) max_count = 138, min_count = 3;
+    tree[max_code+1].Len = (ush)0xffff; /* guard */
+
+    for (n = 0; n <= max_code; n++) {
+        curlen = nextlen; nextlen = tree[n+1].Len;
+        if (++count < max_count && curlen == nextlen) {
+            continue;
+        } else if (count < min_count) {
+            bl_tree[curlen].Freq += count;
+        } else if (curlen != 0) {
+            if (curlen != prevlen) bl_tree[curlen].Freq++;
+            bl_tree[REP_3_6].Freq++;
+        } else if (count <= 10) {
+            bl_tree[REPZ_3_10].Freq++;
+        } else {
+            bl_tree[REPZ_11_138].Freq++;
+        }
+        count = 0; prevlen = curlen;
+        if (nextlen == 0) {
+            max_count = 138, min_count = 3;
+        } else if (curlen == nextlen) {
+            max_count = 6, min_count = 3;
+        } else {
+            max_count = 7, min_count = 4;
+        }
+    }
+}
+
+/* ===========================================================================
+ * Send a literal or distance tree in compressed form, using the codes in
+ * bl_tree.
+ */
+local void send_tree (tree, max_code)
+    ct_data near *tree; /* the tree to be scanned */
+    int max_code;       /* and its largest code of non zero frequency */
+{
+    int n;                     /* iterates over all tree elements */
+    int prevlen = -1;          /* last emitted length */
+    int curlen;                /* length of current code */
+    int nextlen = tree[0].Len; /* length of next code */
+    int count = 0;             /* repeat count of the current code */
+    int max_count = 7;         /* max repeat count */
+    int min_count = 4;         /* min repeat count */
+
+    /* tree[max_code+1].Len = -1; */  /* guard already set */
+    if (nextlen == 0) max_count = 138, min_count = 3;
+
+    for (n = 0; n <= max_code; n++) {
+        curlen = nextlen; nextlen = tree[n+1].Len;
+        if (++count < max_count && curlen == nextlen) {
+            continue;
+        } else if (count < min_count) {
+            do { send_code(curlen, bl_tree); } while (--count != 0);
+
+        } else if (curlen != 0) {
+            if (curlen != prevlen) {
+                send_code(curlen, bl_tree); count--;
+            }
+            Assert(count >= 3 && count <= 6, " 3_6?");
+            send_code(REP_3_6, bl_tree); send_bits(count-3, 2);
+
+        } else if (count <= 10) {
+            send_code(REPZ_3_10, bl_tree); send_bits(count-3, 3);
+
+        } else {
+            send_code(REPZ_11_138, bl_tree); send_bits(count-11, 7);
+        }
+        count = 0; prevlen = curlen;
+        if (nextlen == 0) {
+            max_count = 138, min_count = 3;
+        } else if (curlen == nextlen) {
+            max_count = 6, min_count = 3;
+        } else {
+            max_count = 7, min_count = 4;
+        }
+    }
+}
+
+/* ===========================================================================
+ * Construct the Huffman tree for the bit lengths and return the index in
+ * bl_order of the last bit length code to send.
+ */
+local int build_bl_tree()
+{
+    int max_blindex;  /* index of last bit length code of non zero freq */
+
+    /* Determine the bit length frequencies for literal and distance trees */
+    scan_tree((ct_data near *)dyn_ltree, l_desc.max_code);
+    scan_tree((ct_data near *)dyn_dtree, d_desc.max_code);
+
+    /* Build the bit length tree: */
+    build_tree((tree_desc near *)(&bl_desc));
+    /* opt_len now includes the length of the tree representations, except
+     * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
+     */
+
+    /* Determine the number of bit length codes to send. The pkzip format
+     * requires that at least 4 bit length codes be sent. (appnote.txt says
+     * 3 but the actual value used is 4.)
+     */
+    for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
+        if (bl_tree[bl_order[max_blindex]].Len != 0) break;
+    }
+    /* Update opt_len to include the bit length tree and counts */
+    opt_len += 3*(max_blindex+1) + 5+5+4;
+    Tracev((stderr, "\ndyn trees: dyn %lu, stat %lu", opt_len, static_len));
+
+    return max_blindex;
+}
+
+/* ===========================================================================
+ * Send the header for a block using dynamic Huffman trees: the counts, the
+ * lengths of the bit length codes, the literal tree and the distance tree.
+ * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
+ */
+local void send_all_trees(lcodes, dcodes, blcodes)
+    int lcodes, dcodes, blcodes; /* number of codes for each tree */
+{
+    int rank;                    /* index in bl_order */
+
+    Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
+    Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
+            "too many codes");
+    Tracev((stderr, "\nbl counts: "));
+    send_bits(lcodes-257, 5); /* not +255 as stated in appnote.txt */
+    send_bits(dcodes-1,   5);
+    send_bits(blcodes-4,  4); /* not -3 as stated in appnote.txt */
+    for (rank = 0; rank < blcodes; rank++) {
+        Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
+        send_bits(bl_tree[bl_order[rank]].Len, 3);
+    }
+
+    send_tree((ct_data near *)dyn_ltree, lcodes-1); /* send the literal tree */
+
+    send_tree((ct_data near *)dyn_dtree, dcodes-1); /* send the distance tree */
+}
+
+/* ===========================================================================
+ * Determine the best encoding for the current block: dynamic trees, static
+ * trees or store, and output the encoded block to the zip file. This function
+ * returns the total compressed length for the file so far.
+ */
+off_t flush_block(buf, stored_len, eof)
+    char *buf;        /* input block, or NULL if too old */
+    ulg stored_len;   /* length of input block */
+    int eof;          /* true if this is the last block for a file */
+{
+    ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
+    int max_blindex;  /* index of last bit length code of non zero freq */
+
+    flag_buf[last_flags] = flags; /* Save the flags for the last 8 items */
+
+     /* Check if the file is ascii or binary */
+    if (*file_type == (ush)UNKNOWN) set_file_type();
+
+    /* Construct the literal and distance trees */
+    build_tree((tree_desc near *)(&l_desc));
+    Tracev((stderr, "\nlit data: dyn %lu, stat %lu", opt_len, static_len));
+
+    build_tree((tree_desc near *)(&d_desc));
+    Tracev((stderr, "\ndist data: dyn %lu, stat %lu", opt_len, static_len));
+    /* At this point, opt_len and static_len are the total bit lengths of
+     * the compressed block data, excluding the tree representations.
+     */
+
+    /* Build the bit length tree for the above two trees, and get the index
+     * in bl_order of the last bit length code to send.
+     */
+    max_blindex = build_bl_tree();
+
+    /* Determine the best encoding. Compute first the block length in bytes */
+    opt_lenb = (opt_len+3+7)>>3;
+    static_lenb = (static_len+3+7)>>3;
+    input_len += stored_len; /* for debugging only */
+
+    Trace((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u dist %u ",
+            opt_lenb, opt_len, static_lenb, static_len, stored_len,
+            last_lit, last_dist));
+
+    if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
+
+    /* If compression failed and this is the first and last block,
+     * and if the zip file can be seeked (to rewrite the local header),
+     * the whole file is transformed into a stored file:
+     */
+#ifdef FORCE_METHOD
+    if (level == 1 && eof && compressed_len == 0L) { /* force stored file */
+#else
+    if (stored_len <= opt_lenb && eof && compressed_len == 0L && seekable()) {
+#endif
+        /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
+        if (buf == (char*)0) error ("block vanished");
+
+        copy_block(buf, (unsigned)stored_len, 0); /* without header */
+        compressed_len = stored_len << 3;
+        *file_method = STORED;
+
+#ifdef FORCE_METHOD
+    } else if (level == 2 && buf != (char*)0) { /* force stored block */
+#else
+    } else if (stored_len+4 <= opt_lenb && buf != (char*)0) {
+                       /* 4: two words for the lengths */
+#endif
+        /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
+         * Otherwise we can't have processed more than WSIZE input bytes since
+         * the last block flush, because compression would have been
+         * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
+         * transform a block into a stored block.
+         */
+        send_bits((STORED_BLOCK<<1)+eof, 3);  /* send block type */
+        compressed_len = (compressed_len + 3 + 7) & ~7L;
+        compressed_len += (stored_len + 4) << 3;
+
+        copy_block(buf, (unsigned)stored_len, 1); /* with header */
+
+#ifdef FORCE_METHOD
+    } else if (level == 3) { /* force static trees */
+#else
+    } else if (static_lenb == opt_lenb) {
+#endif
+        send_bits((STATIC_TREES<<1)+eof, 3);
+        compress_block((ct_data near *)static_ltree, (ct_data near *)static_dtree);
+        compressed_len += 3 + static_len;
+    } else {
+        send_bits((DYN_TREES<<1)+eof, 3);
+        send_all_trees(l_desc.max_code+1, d_desc.max_code+1, max_blindex+1);
+        compress_block((ct_data near *)dyn_ltree, (ct_data near *)dyn_dtree);
+        compressed_len += 3 + opt_len;
+    }
+    Assert (compressed_len == bits_sent, "bad compressed size");
+    init_block();
+
+    if (eof) {
+        Assert (input_len == bytes_in, "bad input size");
+        bi_windup();
+        compressed_len += 7;  /* align on byte boundary */
+    }
+
+    return compressed_len >> 3;
+}
+
+/* ===========================================================================
+ * Save the match info and tally the frequency counts. Return true if
+ * the current block must be flushed.
+ */
+int ct_tally (dist, lc)
+    int dist;  /* distance of matched string */
+    int lc;    /* match length-MIN_MATCH or unmatched char (if dist==0) */
+{
+    l_buf[last_lit++] = (uch)lc;
+    if (dist == 0) {
+        /* lc is the unmatched char */
+        dyn_ltree[lc].Freq++;
+    } else {
+        /* Here, lc is the match length - MIN_MATCH */
+        dist--;             /* dist = match distance - 1 */
+        Assert((ush)dist < (ush)MAX_DIST &&
+               (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
+               (ush)d_code(dist) < (ush)D_CODES,  "ct_tally: bad match");
+
+        dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
+        dyn_dtree[d_code(dist)].Freq++;
+
+        d_buf[last_dist++] = (ush)dist;
+        flags |= flag_bit;
+    }
+    flag_bit <<= 1;
+
+    /* Output the flags if they fill a byte: */
+    if ((last_lit & 7) == 0) {
+        flag_buf[last_flags++] = flags;
+        flags = 0, flag_bit = 1;
+    }
+    /* Try to guess if it is profitable to stop the current block here */
+    if (level > 2 && (last_lit & 0xfff) == 0) {
+        /* Compute an upper bound for the compressed length */
+        ulg out_length = (ulg)last_lit*8L;
+        ulg in_length = (ulg)strstart-block_start;
+        int dcode;
+        for (dcode = 0; dcode < D_CODES; dcode++) {
+            out_length += (ulg)dyn_dtree[dcode].Freq*(5L+extra_dbits[dcode]);
+        }
+        out_length >>= 3;
+        Trace((stderr,"\nlast_lit %u, last_dist %u, in %ld, out ~%ld(%ld%%) ",
+               last_lit, last_dist, in_length, out_length,
+               100L - out_length*100L/in_length));
+        if (last_dist < last_lit/2 && out_length < in_length/2) return 1;
+    }
+    return (last_lit == LIT_BUFSIZE-1 || last_dist == DIST_BUFSIZE);
+    /* We avoid equality with LIT_BUFSIZE because of wraparound at 64K
+     * on 16 bit machines and because stored blocks are restricted to
+     * 64K-1 bytes.
+     */
+}
+
+/* ===========================================================================
+ * Send the block data compressed using the given Huffman trees
+ */
+local void compress_block(ltree, dtree)
+    ct_data near *ltree; /* literal tree */
+    ct_data near *dtree; /* distance tree */
+{
+    unsigned dist;      /* distance of matched string */
+    int lc;             /* match length or unmatched char (if dist == 0) */
+    unsigned lx = 0;    /* running index in l_buf */
+    unsigned dx = 0;    /* running index in d_buf */
+    unsigned fx = 0;    /* running index in flag_buf */
+    uch flag = 0;       /* current flags */
+    unsigned code;      /* the code to send */
+    int extra;          /* number of extra bits to send */
+
+    if (last_lit != 0) do {
+        if ((lx & 7) == 0) flag = flag_buf[fx++];
+        lc = l_buf[lx++];
+        if ((flag & 1) == 0) {
+            send_code(lc, ltree); /* send a literal byte */
+            Tracecv(isgraph(lc), (stderr," '%c' ", lc));
+        } else {
+            /* Here, lc is the match length - MIN_MATCH */
+            code = length_code[lc];
+            send_code(code+LITERALS+1, ltree); /* send the length code */
+            extra = extra_lbits[code];
+            if (extra != 0) {
+                lc -= base_length[code];
+                send_bits(lc, extra);        /* send the extra length bits */
+            }
+            dist = d_buf[dx++];
+            /* Here, dist is the match distance - 1 */
+            code = d_code(dist);
+            Assert (code < D_CODES, "bad d_code");
+
+            send_code(code, dtree);       /* send the distance code */
+            extra = extra_dbits[code];
+            if (extra != 0) {
+                dist -= base_dist[code];
+                send_bits(dist, extra);   /* send the extra distance bits */
+            }
+        } /* literal or match pair ? */
+        flag >>= 1;
+    } while (lx < last_lit);
+
+    send_code(END_BLOCK, ltree);
+}
+
+/* ===========================================================================
+ * Set the file type to ASCII or BINARY, using a crude approximation:
+ * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
+ * IN assertion: the fields freq of dyn_ltree are set and the total of all
+ * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
+ */
+local void set_file_type()
+{
+    int n = 0;
+    unsigned ascii_freq = 0;
+    unsigned bin_freq = 0;
+    while (n < 7)        bin_freq += dyn_ltree[n++].Freq;
+    while (n < 128)    ascii_freq += dyn_ltree[n++].Freq;
+    while (n < LITERALS) bin_freq += dyn_ltree[n++].Freq;
+    *file_type = bin_freq > (ascii_freq >> 2) ? BINARY : ASCII;
+    if (*file_type == BINARY && translate_eol) {
+        warning ("-l used on binary file");
+    }
+}