vx32

trees.c (44070B)

---

 /* trees.c -- output deflated data using Huffman coding
  * Copyright (C) 1995-2005 Jean-loup Gailly
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
 /*
  *  ALGORITHM
  *
  *      The "deflation" process uses several Huffman trees. The more
  *      common source values are represented by shorter bit sequences.
  *
  *      Each code tree is stored 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 inflate process, as described
  * in the deflate specification.
  *
  *  REFERENCES
  *
  *      Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
  *      Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
  *
  *      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.
  */
 
 /* @(#) $Id: trees.c 1925 2005-10-06 19:32:02Z baford $ */
 
 /* #define GEN_TREES_H */
 
 #include "deflate.h"
 
 #ifdef DEBUG
 #  include <ctype.h>
 #endif
 
 /* ===========================================================================
  * Constants
  */
 
 #define MAX_BL_BITS 7
 /* Bit length codes must not exceed MAX_BL_BITS bits */
 
 #define END_BLOCK 256
 /* end of block literal code */
 
 #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 const int 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 const int 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 const int 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};
 
 local const uch 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.
  */
 
 #define Buf_size (8 * 2*sizeof(char))
 /* Number of bits used within bi_buf. (bi_buf might be implemented on
  * more than 16 bits on some systems.)
  */
 
 /* ===========================================================================
  * Local data. These are initialized only once.
  */
 
 #define DIST_CODE_LEN  512 /* see definition of array dist_code below */
 
 #if defined(GEN_TREES_H) || !defined(STDC)
 /* non ANSI compilers may not accept trees.h */
 
 local ct_data 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 _tr_init
  * below).
  */
 
 local ct_data static_dtree[D_CODES];
 /* The static distance tree. (Actually a trivial tree since all codes use
  * 5 bits.)
  */
 
 uch _dist_code[DIST_CODE_LEN];
 /* 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.
  */
 
 uch _length_code[MAX_MATCH-MIN_MATCH+1];
 /* length code for each normalized match length (0 == MIN_MATCH) */
 
 local int base_length[LENGTH_CODES];
 /* First normalized length for each code (0 = MIN_MATCH) */
 
 local int base_dist[D_CODES];
 /* First normalized distance for each code (0 = distance of 1) */
 
 #else
 #  include "trees.h"
 #endif /* GEN_TREES_H */
 
 struct static_tree_desc_s {
     const ct_data *static_tree;  /* static tree or NULL */
     const intf *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 */
 };
 
 local static_tree_desc  static_l_desc =
 {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
 
 local static_tree_desc  static_d_desc =
 {static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};
 
 local static_tree_desc  static_bl_desc =
 {(const ct_data *)0, extra_blbits, 0,   BL_CODES, MAX_BL_BITS};
 
 /* ===========================================================================
  * Local (static) routines in this file.
  */
 
 local void tr_static_init OF((void));
 local void init_block     OF((deflate_state *s));
 local void pqdownheap     OF((deflate_state *s, ct_data *tree, int k));
 local void gen_bitlen     OF((deflate_state *s, tree_desc *desc));
 local void gen_codes      OF((ct_data *tree, int max_code, ushf *bl_count));
 local void build_tree     OF((deflate_state *s, tree_desc *desc));
 local void scan_tree      OF((deflate_state *s, ct_data *tree, int max_code));
 local void send_tree      OF((deflate_state *s, ct_data *tree, int max_code));
 local int  build_bl_tree  OF((deflate_state *s));
 local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes,
                               int blcodes));
 local void compress_block OF((deflate_state *s, ct_data *ltree,
                               ct_data *dtree));
 local void set_data_type  OF((deflate_state *s));
 local unsigned bi_reverse OF((unsigned value, int length));
 local void bi_windup      OF((deflate_state *s));
 local void bi_flush       OF((deflate_state *s));
 local void copy_block     OF((deflate_state *s, charf *buf, unsigned len,
                               int header));
 
 #ifdef GEN_TREES_H
 local void gen_trees_header OF((void));
 #endif
 
 #ifndef DEBUG
 #  define send_code(s, c, tree) send_bits(s, 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(s, c, tree) \
      { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
        send_bits(s, tree[c].Code, tree[c].Len); }
 #endif
 
 /* ===========================================================================
  * Output a short LSB first on the stream.
  * IN assertion: there is enough room in pendingBuf.
  */
 #define put_short(s, w) { \
     put_byte(s, (uch)((w) & 0xff)); \
     put_byte(s, (uch)((ush)(w) >> 8)); \
 }
 
 /* ===========================================================================
  * Send a value on a given number of bits.
  * IN assertion: length <= 16 and value fits in length bits.
  */
 #ifdef DEBUG
 local void send_bits      OF((deflate_state *s, int value, int length));
 
 local void send_bits(s, value, length)
     deflate_state *s;
     int value;  /* value to send */
     int length; /* number of bits */
 {
     Tracevv((stderr," l %2d v %4x ", length, value));
     Assert(length > 0 && length <= 15, "invalid length");
     s->bits_sent += (ulg)length;
 
     /* If not enough room in bi_buf, use (valid) bits from bi_buf and
      * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
      * unused bits in value.
      */
     if (s->bi_valid > (int)Buf_size - length) {
         s->bi_buf |= (value << s->bi_valid);
         put_short(s, s->bi_buf);
         s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
         s->bi_valid += length - Buf_size;
     } else {
         s->bi_buf |= value << s->bi_valid;
         s->bi_valid += length;
     }
 }
 #else /* !DEBUG */
 
 #define send_bits(s, value, length) \
 { int len = length;\
   if (s->bi_valid > (int)Buf_size - len) {\
     int val = value;\
     s->bi_buf |= (val << s->bi_valid);\
     put_short(s, s->bi_buf);\
     s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
     s->bi_valid += len - Buf_size;\
   } else {\
     s->bi_buf |= (value) << s->bi_valid;\
     s->bi_valid += len;\
   }\
 }
 #endif /* DEBUG */
 
 
 /* the arguments must not have side effects */
 
 /* ===========================================================================
  * Initialize the various 'constant' tables.
  */
 local void tr_static_init()
 {
 #if defined(GEN_TREES_H) || !defined(STDC)
     static int static_init_done = 0;
     int n;        /* iterates over tree elements */
     int bits;     /* bit counter */
     int length;   /* length value */
     int code;     /* code value */
     int dist;     /* distance index */
     ush bl_count[MAX_BITS+1];
     /* number of codes at each bit length for an optimal tree */
 
     if (static_init_done) return;
 
     /* For some embedded targets, global variables are not initialized: */
     static_l_desc.static_tree = static_ltree;
     static_l_desc.extra_bits = extra_lbits;
     static_d_desc.static_tree = static_dtree;
     static_d_desc.extra_bits = extra_dbits;
     static_bl_desc.extra_bits = extra_blbits;
 
     /* 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, "tr_static_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, "tr_static_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, "tr_static_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 *)static_ltree, L_CODES+1, bl_count);
 
     /* The static distance tree is trivial: */
     for (n = 0; n < D_CODES; n++) {
         static_dtree[n].Len = 5;
         static_dtree[n].Code = bi_reverse((unsigned)n, 5);
     }
     static_init_done = 1;
 
 #  ifdef GEN_TREES_H
     gen_trees_header();
 #  endif
 #endif /* defined(GEN_TREES_H) || !defined(STDC) */
 }
 
 /* ===========================================================================
  * Genererate the file trees.h describing the static trees.
  */
 #ifdef GEN_TREES_H
 #  ifndef DEBUG
 #    include <stdio.h>
 #  endif
 
 #  define SEPARATOR(i, last, width) \
       ((i) == (last)? "\n};\n\n" :    \
        ((i) % (width) == (width)-1 ? ",\n" : ", "))
 
 void gen_trees_header()
 {
     FILE *header = fopen("trees.h", "w");
     int i;
 
     Assert (header != NULL, "Can't open trees.h");
     fprintf(header,
             "/* header created automatically with -DGEN_TREES_H */\n\n");
 
     fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n");
     for (i = 0; i < L_CODES+2; i++) {
         fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code,
                 static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5));
     }
 
     fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n");
     for (i = 0; i < D_CODES; i++) {
         fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code,
                 static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5));
     }
 
     fprintf(header, "const uch _dist_code[DIST_CODE_LEN] = {\n");
     for (i = 0; i < DIST_CODE_LEN; i++) {
         fprintf(header, "%2u%s", _dist_code[i],
                 SEPARATOR(i, DIST_CODE_LEN-1, 20));
     }
 
     fprintf(header, "const uch _length_code[MAX_MATCH-MIN_MATCH+1]= {\n");
     for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) {
         fprintf(header, "%2u%s", _length_code[i],
                 SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20));
     }
 
     fprintf(header, "local const int base_length[LENGTH_CODES] = {\n");
     for (i = 0; i < LENGTH_CODES; i++) {
         fprintf(header, "%1u%s", base_length[i],
                 SEPARATOR(i, LENGTH_CODES-1, 20));
     }
 
     fprintf(header, "local const int base_dist[D_CODES] = {\n");
     for (i = 0; i < D_CODES; i++) {
         fprintf(header, "%5u%s", base_dist[i],
                 SEPARATOR(i, D_CODES-1, 10));
     }
 
     fclose(header);
 }
 #endif /* GEN_TREES_H */
 
 /* ===========================================================================
  * Initialize the tree data structures for a new zlib stream.
  */
 void _tr_init(s)
     deflate_state *s;
 {
     tr_static_init();
 
     s->l_desc.dyn_tree = s->dyn_ltree;
     s->l_desc.stat_desc = &static_l_desc;
 
     s->d_desc.dyn_tree = s->dyn_dtree;
     s->d_desc.stat_desc = &static_d_desc;
 
     s->bl_desc.dyn_tree = s->bl_tree;
     s->bl_desc.stat_desc = &static_bl_desc;
 
     s->bi_buf = 0;
     s->bi_valid = 0;
     s->last_eob_len = 8; /* enough lookahead for inflate */
 #ifdef DEBUG
     s->compressed_len = 0L;
     s->bits_sent = 0L;
 #endif
 
     /* Initialize the first block of the first file: */
     init_block(s);
 }
 
 /* ===========================================================================
  * Initialize a new block.
  */
 local void init_block(s)
     deflate_state *s;
 {
     int n; /* iterates over tree elements */
 
     /* Initialize the trees. */
     for (n = 0; n < L_CODES;  n++) s->dyn_ltree[n].Freq = 0;
     for (n = 0; n < D_CODES;  n++) s->dyn_dtree[n].Freq = 0;
     for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
 
     s->dyn_ltree[END_BLOCK].Freq = 1;
     s->opt_len = s->static_len = 0L;
     s->last_lit = s->matches = 0;
 }
 
 #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(s, tree, top) \
 {\
     top = s->heap[SMALLEST]; \
     s->heap[SMALLEST] = s->heap[s->heap_len--]; \
     pqdownheap(s, 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, depth) \
    (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(s, tree, k)
     deflate_state *s;
     ct_data *tree;  /* the tree to restore */
     int k;               /* node to move down */
 {
     int v = s->heap[k];
     int j = k << 1;  /* left son of k */
     while (j <= s->heap_len) {
         /* Set j to the smallest of the two sons: */
         if (j < s->heap_len &&
             smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
             j++;
         }
         /* Exit if v is smaller than both sons */
         if (smaller(tree, v, s->heap[j], s->depth)) break;
 
         /* Exchange v with the smallest son */
         s->heap[k] = s->heap[j];  k = j;
 
         /* And continue down the tree, setting j to the left son of k */
         j <<= 1;
     }
     s->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(s, desc)
     deflate_state *s;
     tree_desc *desc;    /* the tree descriptor */
 {
     ct_data *tree        = desc->dyn_tree;
     int max_code         = desc->max_code;
     const ct_data *stree = desc->stat_desc->static_tree;
     const intf *extra    = desc->stat_desc->extra_bits;
     int base             = desc->stat_desc->extra_base;
     int max_length       = desc->stat_desc->max_length;
     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++) s->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[s->heap[s->heap_max]].Len = 0; /* root of the heap */
 
     for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
         n = s->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 */
 
         s->bl_count[bits]++;
         xbits = 0;
         if (n >= base) xbits = extra[n-base];
         f = tree[n].Freq;
         s->opt_len += (ulg)f * (bits + xbits);
         if (stree) s->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 (s->bl_count[bits] == 0) bits--;
         s->bl_count[bits]--;      /* move one leaf down the tree */
         s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
         s->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 = s->bl_count[bits];
         while (n != 0) {
             m = s->heap[--h];
             if (m > max_code) continue;
             if ((unsigned) tree[m].Len != (unsigned) bits) {
                 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
                 s->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, bl_count)
     ct_data *tree;             /* the tree to decorate */
     int max_code;              /* largest code with non zero frequency */
     ushf *bl_count;            /* number of codes at each bit length */
 {
     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);
 
         Tracecv(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(s, desc)
     deflate_state *s;
     tree_desc *desc; /* the tree descriptor */
 {
     ct_data *tree         = desc->dyn_tree;
     const ct_data *stree  = desc->stat_desc->static_tree;
     int elems             = desc->stat_desc->elems;
     int n, m;          /* iterate over heap elements */
     int max_code = -1; /* largest code with non zero frequency */
     int node;          /* new node being created */
 
     /* 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.
      */
     s->heap_len = 0, s->heap_max = HEAP_SIZE;
 
     for (n = 0; n < elems; n++) {
         if (tree[n].Freq != 0) {
             s->heap[++(s->heap_len)] = max_code = n;
             s->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 (s->heap_len < 2) {
         node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
         tree[node].Freq = 1;
         s->depth[node] = 0;
         s->opt_len--; if (stree) s->static_len -= stree[node].Len;
         /* node 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 = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
 
     /* Construct the Huffman tree by repeatedly combining the least two
      * frequent nodes.
      */
     node = elems;              /* next internal node of the tree */
     do {
         pqremove(s, tree, n);  /* n = node of least frequency */
         m = s->heap[SMALLEST]; /* m = node of next least frequency */
 
         s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
         s->heap[--(s->heap_max)] = m;
 
         /* Create a new node father of n and m */
         tree[node].Freq = tree[n].Freq + tree[m].Freq;
         s->depth[node] = (uch)((s->depth[n] >= s->depth[m] ?
                                 s->depth[n] : s->depth[m]) + 1);
         tree[n].Dad = tree[m].Dad = (ush)node;
 #ifdef DUMP_BL_TREE
         if (tree == s->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 */
         s->heap[SMALLEST] = node++;
         pqdownheap(s, tree, SMALLEST);
 
     } while (s->heap_len >= 2);
 
     s->heap[--(s->heap_max)] = s->heap[SMALLEST];
 
     /* At this point, the fields freq and dad are set. We can now
      * generate the bit lengths.
      */
     gen_bitlen(s, (tree_desc *)desc);
 
     /* The field len is now set, we can generate the bit codes */
     gen_codes ((ct_data *)tree, max_code, s->bl_count);
 }
 
 /* ===========================================================================
  * Scan a literal or distance tree to determine the frequencies of the codes
  * in the bit length tree.
  */
 local void scan_tree (s, tree, max_code)
     deflate_state *s;
     ct_data *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) {
             s->bl_tree[curlen].Freq += count;
         } else if (curlen != 0) {
             if (curlen != prevlen) s->bl_tree[curlen].Freq++;
             s->bl_tree[REP_3_6].Freq++;
         } else if (count <= 10) {
             s->bl_tree[REPZ_3_10].Freq++;
         } else {
             s->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 (s, tree, max_code)
     deflate_state *s;
     ct_data *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(s, curlen, s->bl_tree); } while (--count != 0);
 
         } else if (curlen != 0) {
             if (curlen != prevlen) {
                 send_code(s, curlen, s->bl_tree); count--;
             }
             Assert(count >= 3 && count <= 6, " 3_6?");
             send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
 
         } else if (count <= 10) {
             send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
 
         } else {
             send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, 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(s)
     deflate_state *s;
 {
     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(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
     scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
 
     /* Build the bit length tree: */
     build_tree(s, (tree_desc *)(&(s->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 (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
     }
     /* Update opt_len to include the bit length tree and counts */
     s->opt_len += 3*(max_blindex+1) + 5+5+4;
     Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
             s->opt_len, s->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(s, lcodes, dcodes, blcodes)
     deflate_state *s;
     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(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
     send_bits(s, dcodes-1,   5);
     send_bits(s, 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(s, s->bl_tree[bl_order[rank]].Len, 3);
     }
     Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
 
     send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
     Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
 
     send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
     Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
 }
 
 /* ===========================================================================
  * Send a stored block
  */
 void _tr_stored_block(s, buf, stored_len, eof)
     deflate_state *s;
     charf *buf;       /* input block */
     ulg stored_len;   /* length of input block */
     int eof;          /* true if this is the last block for a file */
 {
     send_bits(s, (STORED_BLOCK<<1)+eof, 3);  /* send block type */
 #ifdef DEBUG
     s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
     s->compressed_len += (stored_len + 4) << 3;
 #endif
     copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
 }
 
 /* ===========================================================================
  * Send one empty static block to give enough lookahead for inflate.
  * This takes 10 bits, of which 7 may remain in the bit buffer.
  * The current inflate code requires 9 bits of lookahead. If the
  * last two codes for the previous block (real code plus EOB) were coded
  * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode
  * the last real code. In this case we send two empty static blocks instead
  * of one. (There are no problems if the previous block is stored or fixed.)
  * To simplify the code, we assume the worst case of last real code encoded
  * on one bit only.
  */
 void _tr_align(s)
     deflate_state *s;
 {
     send_bits(s, STATIC_TREES<<1, 3);
     send_code(s, END_BLOCK, static_ltree);
 #ifdef DEBUG
     s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
 #endif
     bi_flush(s);
     /* Of the 10 bits for the empty block, we have already sent
      * (10 - bi_valid) bits. The lookahead for the last real code (before
      * the EOB of the previous block) was thus at least one plus the length
      * of the EOB plus what we have just sent of the empty static block.
      */
     if (1 + s->last_eob_len + 10 - s->bi_valid < 9) {
         send_bits(s, STATIC_TREES<<1, 3);
         send_code(s, END_BLOCK, static_ltree);
 #ifdef DEBUG
         s->compressed_len += 10L;
 #endif
         bi_flush(s);
     }
     s->last_eob_len = 7;
 }
 
 /* ===========================================================================
  * Determine the best encoding for the current block: dynamic trees, static
  * trees or store, and output the encoded block to the zip file.
  */
 void _tr_flush_block(s, buf, stored_len, eof)
     deflate_state *s;
     charf *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 = 0;  /* index of last bit length code of non zero freq */
 
     /* Build the Huffman trees unless a stored block is forced */
     if (s->level > 0) {
 
         /* Check if the file is binary or text */
         if (stored_len > 0 && s->strm->data_type == Z_UNKNOWN)
             set_data_type(s);
 
         /* Construct the literal and distance trees */
         build_tree(s, (tree_desc *)(&(s->l_desc)));
         Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
                 s->static_len));
 
         build_tree(s, (tree_desc *)(&(s->d_desc)));
         Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
                 s->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(s);
 
         /* Determine the best encoding. Compute the block lengths in bytes. */
         opt_lenb = (s->opt_len+3+7)>>3;
         static_lenb = (s->static_len+3+7)>>3;
 
         Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
                 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
                 s->last_lit));
 
         if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
 
     } else {
         Assert(buf != (char*)0, "lost buf");
         opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
     }
 
 #ifdef FORCE_STORED
     if (buf != (char*)0) { /* force stored block */
 #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.
          */
         _tr_stored_block(s, buf, stored_len, eof);
 
 #ifdef FORCE_STATIC
     } else if (static_lenb >= 0) { /* force static trees */
 #else
     } else if (s->strategy == Z_FIXED || static_lenb == opt_lenb) {
 #endif
         send_bits(s, (STATIC_TREES<<1)+eof, 3);
         compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
 #ifdef DEBUG
         s->compressed_len += 3 + s->static_len;
 #endif
     } else {
         send_bits(s, (DYN_TREES<<1)+eof, 3);
         send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
                        max_blindex+1);
         compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
 #ifdef DEBUG
         s->compressed_len += 3 + s->opt_len;
 #endif
     }
     Assert (s->compressed_len == s->bits_sent, "bad compressed size");
     /* The above check is made mod 2^32, for files larger than 512 MB
      * and uLong implemented on 32 bits.
      */
     init_block(s);
 
     if (eof) {
         bi_windup(s);
 #ifdef DEBUG
         s->compressed_len += 7;  /* align on byte boundary */
 #endif
     }
     Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
            s->compressed_len-7*eof));
 }
 
 /* ===========================================================================
  * Save the match info and tally the frequency counts. Return true if
  * the current block must be flushed.
  */
 int _tr_tally (s, dist, lc)
     deflate_state *s;
     unsigned dist;  /* distance of matched string */
     unsigned lc;    /* match length-MIN_MATCH or unmatched char (if dist==0) */
 {
     s->d_buf[s->last_lit] = (ush)dist;
     s->l_buf[s->last_lit++] = (uch)lc;
     if (dist == 0) {
         /* lc is the unmatched char */
         s->dyn_ltree[lc].Freq++;
     } else {
         s->matches++;
         /* Here, lc is the match length - MIN_MATCH */
         dist--;             /* dist = match distance - 1 */
         Assert((ush)dist < (ush)MAX_DIST(s) &&
                (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
                (ush)d_code(dist) < (ush)D_CODES,  "_tr_tally: bad match");
 
         s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++;
         s->dyn_dtree[d_code(dist)].Freq++;
     }
 
 #ifdef TRUNCATE_BLOCK
     /* Try to guess if it is profitable to stop the current block here */
     if ((s->last_lit & 0x1fff) == 0 && s->level > 2) {
         /* Compute an upper bound for the compressed length */
         ulg out_length = (ulg)s->last_lit*8L;
         ulg in_length = (ulg)((long)s->strstart - s->block_start);
         int dcode;
         for (dcode = 0; dcode < D_CODES; dcode++) {
             out_length += (ulg)s->dyn_dtree[dcode].Freq *
                 (5L+extra_dbits[dcode]);
         }
         out_length >>= 3;
         Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
                s->last_lit, in_length, out_length,
                100L - out_length*100L/in_length));
         if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
     }
 #endif
     return (s->last_lit == s->lit_bufsize-1);
     /* 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(s, ltree, dtree)
     deflate_state *s;
     ct_data *ltree; /* literal tree */
     ct_data *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 code;      /* the code to send */
     int extra;          /* number of extra bits to send */
 
     if (s->last_lit != 0) do {
         dist = s->d_buf[lx];
         lc = s->l_buf[lx++];
         if (dist == 0) {
             send_code(s, 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(s, code+LITERALS+1, ltree); /* send the length code */
             extra = extra_lbits[code];
             if (extra != 0) {
                 lc -= base_length[code];
                 send_bits(s, lc, extra);       /* send the extra length bits */
             }
             dist--; /* dist is now the match distance - 1 */
             code = d_code(dist);
             Assert (code < D_CODES, "bad d_code");
 
             send_code(s, code, dtree);       /* send the distance code */
             extra = extra_dbits[code];
             if (extra != 0) {
                 dist -= base_dist[code];
                 send_bits(s, dist, extra);   /* send the extra distance bits */
             }
         } /* literal or match pair ? */
 
         /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
         Assert((uInt)(s->pending) < s->lit_bufsize + 2*lx,
                "pendingBuf overflow");
 
     } while (lx < s->last_lit);
 
     send_code(s, END_BLOCK, ltree);
     s->last_eob_len = ltree[END_BLOCK].Len;
 }
 
 /* ===========================================================================
  * Set the data type to BINARY or TEXT, using a crude approximation:
  * set it to Z_TEXT if all symbols are either printable characters (33 to 255)
  * or white spaces (9 to 13, or 32); or set it to Z_BINARY otherwise.
  * IN assertion: the fields Freq of dyn_ltree are set.
  */
 local void set_data_type(s)
     deflate_state *s;
 {
     int n;
 
     for (n = 0; n < 9; n++)
         if (s->dyn_ltree[n].Freq != 0)
             break;
     if (n == 9)
         for (n = 14; n < 32; n++)
             if (s->dyn_ltree[n].Freq != 0)
                 break;
     s->strm->data_type = (n == 32) ? Z_TEXT : Z_BINARY;
 }
 
 /* ===========================================================================
  * Reverse the first len bits of a code, using straightforward code (a faster
  * method would use a table)
  * IN assertion: 1 <= len <= 15
  */
 local unsigned bi_reverse(code, len)
     unsigned code; /* the value to invert */
     int len;       /* its bit length */
 {
     register unsigned res = 0;
     do {
         res |= code & 1;
         code >>= 1, res <<= 1;
     } while (--len > 0);
     return res >> 1;
 }
 
 /* ===========================================================================
  * Flush the bit buffer, keeping at most 7 bits in it.
  */
 local void bi_flush(s)
     deflate_state *s;
 {
     if (s->bi_valid == 16) {
         put_short(s, s->bi_buf);
         s->bi_buf = 0;
         s->bi_valid = 0;
     } else if (s->bi_valid >= 8) {
         put_byte(s, (Byte)s->bi_buf);
         s->bi_buf >>= 8;
         s->bi_valid -= 8;
     }
 }
 
 /* ===========================================================================
  * Flush the bit buffer and align the output on a byte boundary
  */
 local void bi_windup(s)
     deflate_state *s;
 {
     if (s->bi_valid > 8) {
         put_short(s, s->bi_buf);
     } else if (s->bi_valid > 0) {
         put_byte(s, (Byte)s->bi_buf);
     }
     s->bi_buf = 0;
     s->bi_valid = 0;
 #ifdef DEBUG
     s->bits_sent = (s->bits_sent+7) & ~7;
 #endif
 }
 
 /* ===========================================================================
  * Copy a stored block, storing first the length and its
  * one's complement if requested.
  */
 local void copy_block(s, buf, len, header)
     deflate_state *s;
     charf    *buf;    /* the input data */
     unsigned len;     /* its length */
     int      header;  /* true if block header must be written */
 {
     bi_windup(s);        /* align on byte boundary */
     s->last_eob_len = 8; /* enough lookahead for inflate */
 
     if (header) {
         put_short(s, (ush)len);
         put_short(s, (ush)~len);
 #ifdef DEBUG
         s->bits_sent += 2*16;
 #endif
     }
 #ifdef DEBUG
     s->bits_sent += (ulg)len<<3;
 #endif
     while (len--) {
         put_byte(s, *buf++);
     }
 }