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  1. /* trees.c -- output deflated data using Huffman coding
  2.  * Copyright (C) 1995-2010 Jean-loup Gailly
  3.  * detect_data_type() function provided freely by Cosmin Truta, 2006
  4.  * For conditions of distribution and use, see copyright notice in zlib.h
  5.  */
  6.  
  7. /*
  8.  *  ALGORITHM
  9.  *
  10.  *      The "deflation" process uses several Huffman trees. The more
  11.  *      common source values are represented by shorter bit sequences.
  12.  *
  13.  *      Each code tree is stored in a compressed form which is itself
  14.  * a Huffman encoding of the lengths of all the code strings (in
  15.  * ascending order by source values).  The actual code strings are
  16.  * reconstructed from the lengths in the inflate process, as described
  17.  * in the deflate specification.
  18.  *
  19.  *  REFERENCES
  20.  *
  21.  *      Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
  22.  *      Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
  23.  *
  24.  *      Storer, James A.
  25.  *          Data Compression:  Methods and Theory, pp. 49-50.
  26.  *          Computer Science Press, 1988.  ISBN 0-7167-8156-5.
  27.  *
  28.  *      Sedgewick, R.
  29.  *          Algorithms, p290.
  30.  *          Addison-Wesley, 1983. ISBN 0-201-06672-6.
  31.  */
  32.  
  33. /* @(#) $Id$ */
  34.  
  35. /* #define GEN_TREES_H */
  36.  
  37. #include "deflate.h"
  38.  
  39. #ifdef DEBUG
  40. #  include <ctype.h>
  41. #endif
  42.  
  43. /* ===========================================================================
  44.  * Constants
  45.  */
  46.  
  47. #define MAX_BL_BITS 7
  48. /* Bit length codes must not exceed MAX_BL_BITS bits */
  49.  
  50. #define END_BLOCK 256
  51. /* end of block literal code */
  52.  
  53. #define REP_3_6      16
  54. /* repeat previous bit length 3-6 times (2 bits of repeat count) */
  55.  
  56. #define REPZ_3_10    17
  57. /* repeat a zero length 3-10 times  (3 bits of repeat count) */
  58.  
  59. #define REPZ_11_138  18
  60. /* repeat a zero length 11-138 times  (7 bits of repeat count) */
  61.  
  62. local const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */
  63.    = {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};
  64.  
  65. local const int extra_dbits[D_CODES] /* extra bits for each distance code */
  66.    = {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};
  67.  
  68. local const int extra_blbits[BL_CODES]/* extra bits for each bit length code */
  69.    = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
  70.  
  71. local const uch bl_order[BL_CODES]
  72.    = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
  73. /* The lengths of the bit length codes are sent in order of decreasing
  74.  * probability, to avoid transmitting the lengths for unused bit length codes.
  75.  */
  76.  
  77. #define Buf_size (8 * 2*sizeof(char))
  78. /* Number of bits used within bi_buf. (bi_buf might be implemented on
  79.  * more than 16 bits on some systems.)
  80.  */
  81.  
  82. /* ===========================================================================
  83.  * Local data. These are initialized only once.
  84.  */
  85.  
  86. #define DIST_CODE_LEN  512 /* see definition of array dist_code below */
  87.  
  88. #if defined(GEN_TREES_H) || !defined(STDC)
  89. /* non ANSI compilers may not accept trees.h */
  90.  
  91. local ct_data static_ltree[L_CODES+2];
  92. /* The static literal tree. Since the bit lengths are imposed, there is no
  93.  * need for the L_CODES extra codes used during heap construction. However
  94.  * The codes 286 and 287 are needed to build a canonical tree (see _tr_init
  95.  * below).
  96.  */
  97.  
  98. local ct_data static_dtree[D_CODES];
  99. /* The static distance tree. (Actually a trivial tree since all codes use
  100.  * 5 bits.)
  101.  */
  102.  
  103. uch _dist_code[DIST_CODE_LEN];
  104. /* Distance codes. The first 256 values correspond to the distances
  105.  * 3 .. 258, the last 256 values correspond to the top 8 bits of
  106.  * the 15 bit distances.
  107.  */
  108.  
  109. uch _length_code[MAX_MATCH-MIN_MATCH+1];
  110. /* length code for each normalized match length (0 == MIN_MATCH) */
  111.  
  112. local int base_length[LENGTH_CODES];
  113. /* First normalized length for each code (0 = MIN_MATCH) */
  114.  
  115. local int base_dist[D_CODES];
  116. /* First normalized distance for each code (0 = distance of 1) */
  117.  
  118. #else
  119. #  include "trees.h"
  120. #endif /* GEN_TREES_H */
  121.  
  122. struct static_tree_desc_s {
  123.     const ct_data *static_tree;  /* static tree or NULL */
  124.     const intf *extra_bits;      /* extra bits for each code or NULL */
  125.     int     extra_base;          /* base index for extra_bits */
  126.     int     elems;               /* max number of elements in the tree */
  127.     int     max_length;          /* max bit length for the codes */
  128. };
  129.  
  130. local static_tree_desc  static_l_desc =
  131. {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
  132.  
  133. local static_tree_desc  static_d_desc =
  134. {static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};
  135.  
  136. local static_tree_desc  static_bl_desc =
  137. {(const ct_data *)0, extra_blbits, 0,   BL_CODES, MAX_BL_BITS};
  138.  
  139. /* ===========================================================================
  140.  * Local (static) routines in this file.
  141.  */
  142.  
  143. local void tr_static_init OF((void));
  144. local void init_block     OF((deflate_state *s));
  145. local void pqdownheap     OF((deflate_state *s, ct_data *tree, int k));
  146. local void gen_bitlen     OF((deflate_state *s, tree_desc *desc));
  147. local void gen_codes      OF((ct_data *tree, int max_code, ushf *bl_count));
  148. local void build_tree     OF((deflate_state *s, tree_desc *desc));
  149. local void scan_tree      OF((deflate_state *s, ct_data *tree, int max_code));
  150. local void send_tree      OF((deflate_state *s, ct_data *tree, int max_code));
  151. local int  build_bl_tree  OF((deflate_state *s));
  152. local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes,
  153.                               int blcodes));
  154. local void compress_block OF((deflate_state *s, ct_data *ltree,
  155.                               ct_data *dtree));
  156. local int  detect_data_type OF((deflate_state *s));
  157. local unsigned bi_reverse OF((unsigned value, int length));
  158. local void bi_windup      OF((deflate_state *s));
  159. local void bi_flush       OF((deflate_state *s));
  160. local void copy_block     OF((deflate_state *s, charf *buf, unsigned len,
  161.                               int header));
  162.  
  163. #ifdef GEN_TREES_H
  164. local void gen_trees_header OF((void));
  165. #endif
  166.  
  167. #ifndef DEBUG
  168. #  define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
  169.    /* Send a code of the given tree. c and tree must not have side effects */
  170.  
  171. #else /* DEBUG */
  172. #  define send_code(s, c, tree) \
  173.      { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
  174.        send_bits(s, tree[c].Code, tree[c].Len); }
  175. #endif
  176.  
  177. /* ===========================================================================
  178.  * Output a short LSB first on the stream.
  179.  * IN assertion: there is enough room in pendingBuf.
  180.  */
  181. #define put_short(s, w) { \
  182.     put_byte(s, (uch)((w) & 0xff)); \
  183.     put_byte(s, (uch)((ush)(w) >> 8)); \
  184. }
  185.  
  186. /* ===========================================================================
  187.  * Send a value on a given number of bits.
  188.  * IN assertion: length <= 16 and value fits in length bits.
  189.  */
  190. #ifdef DEBUG
  191. local void send_bits      OF((deflate_state *s, int value, int length));
  192.  
  193. local void send_bits(s, value, length)
  194.     deflate_state *s;
  195.     int value;  /* value to send */
  196.     int length; /* number of bits */
  197. {
  198.     Tracevv((stderr," l %2d v %4x ", length, value));
  199.     Assert(length > 0 && length <= 15, "invalid length");
  200.     s->bits_sent += (ulg)length;
  201.  
  202.     /* If not enough room in bi_buf, use (valid) bits from bi_buf and
  203.      * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
  204.      * unused bits in value.
  205.      */
  206.     if (s->bi_valid > (int)Buf_size - length) {
  207.         s->bi_buf |= (ush)value << s->bi_valid;
  208.         put_short(s, s->bi_buf);
  209.         s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
  210.         s->bi_valid += length - Buf_size;
  211.     } else {
  212.         s->bi_buf |= (ush)value << s->bi_valid;
  213.         s->bi_valid += length;
  214.     }
  215. }
  216. #else /* !DEBUG */
  217.  
  218. #define send_bits(s, value, length) \
  219. { int len = length;\
  220.   if (s->bi_valid > (int)Buf_size - len) {\
  221.     int val = value;\
  222.     s->bi_buf |= (ush)val << s->bi_valid;\
  223.     put_short(s, s->bi_buf);\
  224.     s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
  225.     s->bi_valid += len - Buf_size;\
  226.   } else {\
  227.     s->bi_buf |= (ush)(value) << s->bi_valid;\
  228.     s->bi_valid += len;\
  229.   }\
  230. }
  231. #endif /* DEBUG */
  232.  
  233.  
  234. /* the arguments must not have side effects */
  235.  
  236. /* ===========================================================================
  237.  * Initialize the various 'constant' tables.
  238.  */
  239. local void tr_static_init()
  240. {
  241. #if defined(GEN_TREES_H) || !defined(STDC)
  242.     static int static_init_done = 0;
  243.     int n;        /* iterates over tree elements */
  244.     int bits;     /* bit counter */
  245.     int length;   /* length value */
  246.     int code;     /* code value */
  247.     int dist;     /* distance index */
  248.     ush bl_count[MAX_BITS+1];
  249.     /* number of codes at each bit length for an optimal tree */
  250.  
  251.     if (static_init_done) return;
  252.  
  253.     /* For some embedded targets, global variables are not initialized: */
  254. #ifdef NO_INIT_GLOBAL_POINTERS
  255.     static_l_desc.static_tree = static_ltree;
  256.     static_l_desc.extra_bits = extra_lbits;
  257.     static_d_desc.static_tree = static_dtree;
  258.     static_d_desc.extra_bits = extra_dbits;
  259.     static_bl_desc.extra_bits = extra_blbits;
  260. #endif
  261.  
  262.     /* Initialize the mapping length (0..255) -> length code (0..28) */
  263.     length = 0;
  264.     for (code = 0; code < LENGTH_CODES-1; code++) {
  265.         base_length[code] = length;
  266.         for (n = 0; n < (1<<extra_lbits[code]); n++) {
  267.             _length_code[length++] = (uch)code;
  268.         }
  269.     }
  270.     Assert (length == 256, "tr_static_init: length != 256");
  271.     /* Note that the length 255 (match length 258) can be represented
  272.      * in two different ways: code 284 + 5 bits or code 285, so we
  273.      * overwrite length_code[255] to use the best encoding:
  274.      */
  275.     _length_code[length-1] = (uch)code;
  276.  
  277.     /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
  278.     dist = 0;
  279.     for (code = 0 ; code < 16; code++) {
  280.         base_dist[code] = dist;
  281.         for (n = 0; n < (1<<extra_dbits[code]); n++) {
  282.             _dist_code[dist++] = (uch)code;
  283.         }
  284.     }
  285.     Assert (dist == 256, "tr_static_init: dist != 256");
  286.     dist >>= 7; /* from now on, all distances are divided by 128 */
  287.     for ( ; code < D_CODES; code++) {
  288.         base_dist[code] = dist << 7;
  289.         for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
  290.             _dist_code[256 + dist++] = (uch)code;
  291.         }
  292.     }
  293.     Assert (dist == 256, "tr_static_init: 256+dist != 512");
  294.  
  295.     /* Construct the codes of the static literal tree */
  296.     for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
  297.     n = 0;
  298.     while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
  299.     while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
  300.     while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
  301.     while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
  302.     /* Codes 286 and 287 do not exist, but we must include them in the
  303.      * tree construction to get a canonical Huffman tree (longest code
  304.      * all ones)
  305.      */
  306.     gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
  307.  
  308.     /* The static distance tree is trivial: */
  309.     for (n = 0; n < D_CODES; n++) {
  310.         static_dtree[n].Len = 5;
  311.         static_dtree[n].Code = bi_reverse((unsigned)n, 5);
  312.     }
  313.     static_init_done = 1;
  314.  
  315. #  ifdef GEN_TREES_H
  316.     gen_trees_header();
  317. #  endif
  318. #endif /* defined(GEN_TREES_H) || !defined(STDC) */
  319. }
  320.  
  321. /* ===========================================================================
  322.  * Genererate the file trees.h describing the static trees.
  323.  */
  324. #ifdef GEN_TREES_H
  325. #  ifndef DEBUG
  326. #    include <stdio.h>
  327. #  endif
  328.  
  329. #  define SEPARATOR(i, last, width) \
  330.       ((i) == (last)? "\n};\n\n" :    \
  331.        ((i) % (width) == (width)-1 ? ",\n" : ", "))
  332.  
  333. void gen_trees_header()
  334. {
  335.     FILE *header = fopen("trees.h", "w");
  336.     int i;
  337.  
  338.     Assert (header != NULL, "Can't open trees.h");
  339.     fprintf(header,
  340.             "/* header created automatically with -DGEN_TREES_H */\n\n");
  341.  
  342.     fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n");
  343.     for (i = 0; i < L_CODES+2; i++) {
  344.         fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code,
  345.                 static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5));
  346.     }
  347.  
  348.     fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n");
  349.     for (i = 0; i < D_CODES; i++) {
  350.         fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code,
  351.                 static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5));
  352.     }
  353.  
  354.     fprintf(header, "const uch ZLIB_INTERNAL _dist_code[DIST_CODE_LEN] = {\n");
  355.     for (i = 0; i < DIST_CODE_LEN; i++) {
  356.         fprintf(header, "%2u%s", _dist_code[i],
  357.                 SEPARATOR(i, DIST_CODE_LEN-1, 20));
  358.     }
  359.  
  360.     fprintf(header,
  361.         "const uch ZLIB_INTERNAL _length_code[MAX_MATCH-MIN_MATCH+1]= {\n");
  362.     for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) {
  363.         fprintf(header, "%2u%s", _length_code[i],
  364.                 SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20));
  365.     }
  366.  
  367.     fprintf(header, "local const int base_length[LENGTH_CODES] = {\n");
  368.     for (i = 0; i < LENGTH_CODES; i++) {
  369.         fprintf(header, "%1u%s", base_length[i],
  370.                 SEPARATOR(i, LENGTH_CODES-1, 20));
  371.     }
  372.  
  373.     fprintf(header, "local const int base_dist[D_CODES] = {\n");
  374.     for (i = 0; i < D_CODES; i++) {
  375.         fprintf(header, "%5u%s", base_dist[i],
  376.                 SEPARATOR(i, D_CODES-1, 10));
  377.     }
  378.  
  379.     fclose(header);
  380. }
  381. #endif /* GEN_TREES_H */
  382.  
  383. /* ===========================================================================
  384.  * Initialize the tree data structures for a new zlib stream.
  385.  */
  386. void ZLIB_INTERNAL _tr_init(s)
  387.     deflate_state *s;
  388. {
  389.     tr_static_init();
  390.  
  391.     s->l_desc.dyn_tree = s->dyn_ltree;
  392.     s->l_desc.stat_desc = &static_l_desc;
  393.  
  394.     s->d_desc.dyn_tree = s->dyn_dtree;
  395.     s->d_desc.stat_desc = &static_d_desc;
  396.  
  397.     s->bl_desc.dyn_tree = s->bl_tree;
  398.     s->bl_desc.stat_desc = &static_bl_desc;
  399.  
  400.     s->bi_buf = 0;
  401.     s->bi_valid = 0;
  402.     s->last_eob_len = 8; /* enough lookahead for inflate */
  403. #ifdef DEBUG
  404.     s->compressed_len = 0L;
  405.     s->bits_sent = 0L;
  406. #endif
  407.  
  408.     /* Initialize the first block of the first file: */
  409.     init_block(s);
  410. }
  411.  
  412. /* ===========================================================================
  413.  * Initialize a new block.
  414.  */
  415. local void init_block(s)
  416.     deflate_state *s;
  417. {
  418.     int n; /* iterates over tree elements */
  419.  
  420.     /* Initialize the trees. */
  421.     for (n = 0; n < L_CODES;  n++) s->dyn_ltree[n].Freq = 0;
  422.     for (n = 0; n < D_CODES;  n++) s->dyn_dtree[n].Freq = 0;
  423.     for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
  424.  
  425.     s->dyn_ltree[END_BLOCK].Freq = 1;
  426.     s->opt_len = s->static_len = 0L;
  427.     s->last_lit = s->matches = 0;
  428. }
  429.  
  430. #define SMALLEST 1
  431. /* Index within the heap array of least frequent node in the Huffman tree */
  432.  
  433.  
  434. /* ===========================================================================
  435.  * Remove the smallest element from the heap and recreate the heap with
  436.  * one less element. Updates heap and heap_len.
  437.  */
  438. #define pqremove(s, tree, top) \
  439. {\
  440.     top = s->heap[SMALLEST]; \
  441.     s->heap[SMALLEST] = s->heap[s->heap_len--]; \
  442.     pqdownheap(s, tree, SMALLEST); \
  443. }
  444.  
  445. /* ===========================================================================
  446.  * Compares to subtrees, using the tree depth as tie breaker when
  447.  * the subtrees have equal frequency. This minimizes the worst case length.
  448.  */
  449. #define smaller(tree, n, m, depth) \
  450.    (tree[n].Freq < tree[m].Freq || \
  451.    (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
  452.  
  453. /* ===========================================================================
  454.  * Restore the heap property by moving down the tree starting at node k,
  455.  * exchanging a node with the smallest of its two sons if necessary, stopping
  456.  * when the heap property is re-established (each father smaller than its
  457.  * two sons).
  458.  */
  459. local void pqdownheap(s, tree, k)
  460.     deflate_state *s;
  461.     ct_data *tree;  /* the tree to restore */
  462.     int k;               /* node to move down */
  463. {
  464.     int v = s->heap[k];
  465.     int j = k << 1;  /* left son of k */
  466.     while (j <= s->heap_len) {
  467.         /* Set j to the smallest of the two sons: */
  468.         if (j < s->heap_len &&
  469.             smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
  470.             j++;
  471.         }
  472.         /* Exit if v is smaller than both sons */
  473.         if (smaller(tree, v, s->heap[j], s->depth)) break;
  474.  
  475.         /* Exchange v with the smallest son */
  476.         s->heap[k] = s->heap[j];  k = j;
  477.  
  478.         /* And continue down the tree, setting j to the left son of k */
  479.         j <<= 1;
  480.     }
  481.     s->heap[k] = v;
  482. }
  483.  
  484. /* ===========================================================================
  485.  * Compute the optimal bit lengths for a tree and update the total bit length
  486.  * for the current block.
  487.  * IN assertion: the fields freq and dad are set, heap[heap_max] and
  488.  *    above are the tree nodes sorted by increasing frequency.
  489.  * OUT assertions: the field len is set to the optimal bit length, the
  490.  *     array bl_count contains the frequencies for each bit length.
  491.  *     The length opt_len is updated; static_len is also updated if stree is
  492.  *     not null.
  493.  */
  494. local void gen_bitlen(s, desc)
  495.     deflate_state *s;
  496.     tree_desc *desc;    /* the tree descriptor */
  497. {
  498.     ct_data *tree        = desc->dyn_tree;
  499.     int max_code         = desc->max_code;
  500.     const ct_data *stree = desc->stat_desc->static_tree;
  501.     const intf *extra    = desc->stat_desc->extra_bits;
  502.     int base             = desc->stat_desc->extra_base;
  503.     int max_length       = desc->stat_desc->max_length;
  504.     int h;              /* heap index */
  505.     int n, m;           /* iterate over the tree elements */
  506.     int bits;           /* bit length */
  507.     int xbits;          /* extra bits */
  508.     ush f;              /* frequency */
  509.     int overflow = 0;   /* number of elements with bit length too large */
  510.  
  511.     for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
  512.  
  513.     /* In a first pass, compute the optimal bit lengths (which may
  514.      * overflow in the case of the bit length tree).
  515.      */
  516.     tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
  517.  
  518.     for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
  519.         n = s->heap[h];
  520.         bits = tree[tree[n].Dad].Len + 1;
  521.         if (bits > max_length) bits = max_length, overflow++;
  522.         tree[n].Len = (ush)bits;
  523.         /* We overwrite tree[n].Dad which is no longer needed */
  524.  
  525.         if (n > max_code) continue; /* not a leaf node */
  526.  
  527.         s->bl_count[bits]++;
  528.         xbits = 0;
  529.         if (n >= base) xbits = extra[n-base];
  530.         f = tree[n].Freq;
  531.         s->opt_len += (ulg)f * (bits + xbits);
  532.         if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
  533.     }
  534.     if (overflow == 0) return;
  535.  
  536.     Trace((stderr,"\nbit length overflow\n"));
  537.     /* This happens for example on obj2 and pic of the Calgary corpus */
  538.  
  539.     /* Find the first bit length which could increase: */
  540.     do {
  541.         bits = max_length-1;
  542.         while (s->bl_count[bits] == 0) bits--;
  543.         s->bl_count[bits]--;      /* move one leaf down the tree */
  544.         s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
  545.         s->bl_count[max_length]--;
  546.         /* The brother of the overflow item also moves one step up,
  547.          * but this does not affect bl_count[max_length]
  548.          */
  549.         overflow -= 2;
  550.     } while (overflow > 0);
  551.  
  552.     /* Now recompute all bit lengths, scanning in increasing frequency.
  553.      * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
  554.      * lengths instead of fixing only the wrong ones. This idea is taken
  555.      * from 'ar' written by Haruhiko Okumura.)
  556.      */
  557.     for (bits = max_length; bits != 0; bits--) {
  558.         n = s->bl_count[bits];
  559.         while (n != 0) {
  560.             m = s->heap[--h];
  561.             if (m > max_code) continue;
  562.             if ((unsigned) tree[m].Len != (unsigned) bits) {
  563.                 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
  564.                 s->opt_len += ((long)bits - (long)tree[m].Len)
  565.                               *(long)tree[m].Freq;
  566.                 tree[m].Len = (ush)bits;
  567.             }
  568.             n--;
  569.         }
  570.     }
  571. }
  572.  
  573. /* ===========================================================================
  574.  * Generate the codes for a given tree and bit counts (which need not be
  575.  * optimal).
  576.  * IN assertion: the array bl_count contains the bit length statistics for
  577.  * the given tree and the field len is set for all tree elements.
  578.  * OUT assertion: the field code is set for all tree elements of non
  579.  *     zero code length.
  580.  */
  581. local void gen_codes (tree, max_code, bl_count)
  582.     ct_data *tree;             /* the tree to decorate */
  583.     int max_code;              /* largest code with non zero frequency */
  584.     ushf *bl_count;            /* number of codes at each bit length */
  585. {
  586.     ush next_code[MAX_BITS+1]; /* next code value for each bit length */
  587.     ush code = 0;              /* running code value */
  588.     int bits;                  /* bit index */
  589.     int n;                     /* code index */
  590.  
  591.     /* The distribution counts are first used to generate the code values
  592.      * without bit reversal.
  593.      */
  594.     for (bits = 1; bits <= MAX_BITS; bits++) {
  595.         next_code[bits] = code = (code + bl_count[bits-1]) << 1;
  596.     }
  597.     /* Check that the bit counts in bl_count are consistent. The last code
  598.      * must be all ones.
  599.      */
  600.     Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
  601.             "inconsistent bit counts");
  602.     Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
  603.  
  604.     for (n = 0;  n <= max_code; n++) {
  605.         int len = tree[n].Len;
  606.         if (len == 0) continue;
  607.         /* Now reverse the bits */
  608.         tree[n].Code = bi_reverse(next_code[len]++, len);
  609.  
  610.         Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
  611.              n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
  612.     }
  613. }
  614.  
  615. /* ===========================================================================
  616.  * Construct one Huffman tree and assigns the code bit strings and lengths.
  617.  * Update the total bit length for the current block.
  618.  * IN assertion: the field freq is set for all tree elements.
  619.  * OUT assertions: the fields len and code are set to the optimal bit length
  620.  *     and corresponding code. The length opt_len is updated; static_len is
  621.  *     also updated if stree is not null. The field max_code is set.
  622.  */
  623. local void build_tree(s, desc)
  624.     deflate_state *s;
  625.     tree_desc *desc; /* the tree descriptor */
  626. {
  627.     ct_data *tree         = desc->dyn_tree;
  628.     const ct_data *stree  = desc->stat_desc->static_tree;
  629.     int elems             = desc->stat_desc->elems;
  630.     int n, m;          /* iterate over heap elements */
  631.     int max_code = -1; /* largest code with non zero frequency */
  632.     int node;          /* new node being created */
  633.  
  634.     /* Construct the initial heap, with least frequent element in
  635.      * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
  636.      * heap[0] is not used.
  637.      */
  638.     s->heap_len = 0, s->heap_max = HEAP_SIZE;
  639.  
  640.     for (n = 0; n < elems; n++) {
  641.         if (tree[n].Freq != 0) {
  642.             s->heap[++(s->heap_len)] = max_code = n;
  643.             s->depth[n] = 0;
  644.         } else {
  645.             tree[n].Len = 0;
  646.         }
  647.     }
  648.  
  649.     /* The pkzip format requires that at least one distance code exists,
  650.      * and that at least one bit should be sent even if there is only one
  651.      * possible code. So to avoid special checks later on we force at least
  652.      * two codes of non zero frequency.
  653.      */
  654.     while (s->heap_len < 2) {
  655.         node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
  656.         tree[node].Freq = 1;
  657.         s->depth[node] = 0;
  658.         s->opt_len--; if (stree) s->static_len -= stree[node].Len;
  659.         /* node is 0 or 1 so it does not have extra bits */
  660.     }
  661.     desc->max_code = max_code;
  662.  
  663.     /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
  664.      * establish sub-heaps of increasing lengths:
  665.      */
  666.     for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
  667.  
  668.     /* Construct the Huffman tree by repeatedly combining the least two
  669.      * frequent nodes.
  670.      */
  671.     node = elems;              /* next internal node of the tree */
  672.     do {
  673.         pqremove(s, tree, n);  /* n = node of least frequency */
  674.         m = s->heap[SMALLEST]; /* m = node of next least frequency */
  675.  
  676.         s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
  677.         s->heap[--(s->heap_max)] = m;
  678.  
  679.         /* Create a new node father of n and m */
  680.         tree[node].Freq = tree[n].Freq + tree[m].Freq;
  681.         s->depth[node] = (uch)((s->depth[n] >= s->depth[m] ?
  682.                                 s->depth[n] : s->depth[m]) + 1);
  683.         tree[n].Dad = tree[m].Dad = (ush)node;
  684. #ifdef DUMP_BL_TREE
  685.         if (tree == s->bl_tree) {
  686.             fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
  687.                     node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
  688.         }
  689. #endif
  690.         /* and insert the new node in the heap */
  691.         s->heap[SMALLEST] = node++;
  692.         pqdownheap(s, tree, SMALLEST);
  693.  
  694.     } while (s->heap_len >= 2);
  695.  
  696.     s->heap[--(s->heap_max)] = s->heap[SMALLEST];
  697.  
  698.     /* At this point, the fields freq and dad are set. We can now
  699.      * generate the bit lengths.
  700.      */
  701.     gen_bitlen(s, (tree_desc *)desc);
  702.  
  703.     /* The field len is now set, we can generate the bit codes */
  704.     gen_codes ((ct_data *)tree, max_code, s->bl_count);
  705. }
  706.  
  707. /* ===========================================================================
  708.  * Scan a literal or distance tree to determine the frequencies of the codes
  709.  * in the bit length tree.
  710.  */
  711. local void scan_tree (s, tree, max_code)
  712.     deflate_state *s;
  713.     ct_data *tree;   /* the tree to be scanned */
  714.     int max_code;    /* and its largest code of non zero frequency */
  715. {
  716.     int n;                     /* iterates over all tree elements */
  717.     int prevlen = -1;          /* last emitted length */
  718.     int curlen;                /* length of current code */
  719.     int nextlen = tree[0].Len; /* length of next code */
  720.     int count = 0;             /* repeat count of the current code */
  721.     int max_count = 7;         /* max repeat count */
  722.     int min_count = 4;         /* min repeat count */
  723.  
  724.     if (nextlen == 0) max_count = 138, min_count = 3;
  725.     tree[max_code+1].Len = (ush)0xffff; /* guard */
  726.  
  727.     for (n = 0; n <= max_code; n++) {
  728.         curlen = nextlen; nextlen = tree[n+1].Len;
  729.         if (++count < max_count && curlen == nextlen) {
  730.             continue;
  731.         } else if (count < min_count) {
  732.             s->bl_tree[curlen].Freq += count;
  733.         } else if (curlen != 0) {
  734.             if (curlen != prevlen) s->bl_tree[curlen].Freq++;
  735.             s->bl_tree[REP_3_6].Freq++;
  736.         } else if (count <= 10) {
  737.             s->bl_tree[REPZ_3_10].Freq++;
  738.         } else {
  739.             s->bl_tree[REPZ_11_138].Freq++;
  740.         }
  741.         count = 0; prevlen = curlen;
  742.         if (nextlen == 0) {
  743.             max_count = 138, min_count = 3;
  744.         } else if (curlen == nextlen) {
  745.             max_count = 6, min_count = 3;
  746.         } else {
  747.             max_count = 7, min_count = 4;
  748.         }
  749.     }
  750. }
  751.  
  752. /* ===========================================================================
  753.  * Send a literal or distance tree in compressed form, using the codes in
  754.  * bl_tree.
  755.  */
  756. local void send_tree (s, tree, max_code)
  757.     deflate_state *s;
  758.     ct_data *tree; /* the tree to be scanned */
  759.     int max_code;       /* and its largest code of non zero frequency */
  760. {
  761.     int n;                     /* iterates over all tree elements */
  762.     int prevlen = -1;          /* last emitted length */
  763.     int curlen;                /* length of current code */
  764.     int nextlen = tree[0].Len; /* length of next code */
  765.     int count = 0;             /* repeat count of the current code */
  766.     int max_count = 7;         /* max repeat count */
  767.     int min_count = 4;         /* min repeat count */
  768.  
  769.     /* tree[max_code+1].Len = -1; */  /* guard already set */
  770.     if (nextlen == 0) max_count = 138, min_count = 3;
  771.  
  772.     for (n = 0; n <= max_code; n++) {
  773.         curlen = nextlen; nextlen = tree[n+1].Len;
  774.         if (++count < max_count && curlen == nextlen) {
  775.             continue;
  776.         } else if (count < min_count) {
  777.             do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
  778.  
  779.         } else if (curlen != 0) {
  780.             if (curlen != prevlen) {
  781.                 send_code(s, curlen, s->bl_tree); count--;
  782.             }
  783.             Assert(count >= 3 && count <= 6, " 3_6?");
  784.             send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
  785.  
  786.         } else if (count <= 10) {
  787.             send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
  788.  
  789.         } else {
  790.             send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
  791.         }
  792.         count = 0; prevlen = curlen;
  793.         if (nextlen == 0) {
  794.             max_count = 138, min_count = 3;
  795.         } else if (curlen == nextlen) {
  796.             max_count = 6, min_count = 3;
  797.         } else {
  798.             max_count = 7, min_count = 4;
  799.         }
  800.     }
  801. }
  802.  
  803. /* ===========================================================================
  804.  * Construct the Huffman tree for the bit lengths and return the index in
  805.  * bl_order of the last bit length code to send.
  806.  */
  807. local int build_bl_tree(s)
  808.     deflate_state *s;
  809. {
  810.     int max_blindex;  /* index of last bit length code of non zero freq */
  811.  
  812.     /* Determine the bit length frequencies for literal and distance trees */
  813.     scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
  814.     scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
  815.  
  816.     /* Build the bit length tree: */
  817.     build_tree(s, (tree_desc *)(&(s->bl_desc)));
  818.     /* opt_len now includes the length of the tree representations, except
  819.      * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
  820.      */
  821.  
  822.     /* Determine the number of bit length codes to send. The pkzip format
  823.      * requires that at least 4 bit length codes be sent. (appnote.txt says
  824.      * 3 but the actual value used is 4.)
  825.      */
  826.     for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
  827.         if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
  828.     }
  829.     /* Update opt_len to include the bit length tree and counts */
  830.     s->opt_len += 3*(max_blindex+1) + 5+5+4;
  831.     Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
  832.             s->opt_len, s->static_len));
  833.  
  834.     return max_blindex;
  835. }
  836.  
  837. /* ===========================================================================
  838.  * Send the header for a block using dynamic Huffman trees: the counts, the
  839.  * lengths of the bit length codes, the literal tree and the distance tree.
  840.  * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
  841.  */
  842. local void send_all_trees(s, lcodes, dcodes, blcodes)
  843.     deflate_state *s;
  844.     int lcodes, dcodes, blcodes; /* number of codes for each tree */
  845. {
  846.     int rank;                    /* index in bl_order */
  847.  
  848.     Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
  849.     Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
  850.             "too many codes");
  851.     Tracev((stderr, "\nbl counts: "));
  852.     send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
  853.     send_bits(s, dcodes-1,   5);
  854.     send_bits(s, blcodes-4,  4); /* not -3 as stated in appnote.txt */
  855.     for (rank = 0; rank < blcodes; rank++) {
  856.         Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
  857.         send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
  858.     }
  859.     Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
  860.  
  861.     send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
  862.     Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
  863.  
  864.     send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
  865.     Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
  866. }
  867.  
  868. /* ===========================================================================
  869.  * Send a stored block
  870.  */
  871. void ZLIB_INTERNAL _tr_stored_block(s, buf, stored_len, last)
  872.     deflate_state *s;
  873.     charf *buf;       /* input block */
  874.     ulg stored_len;   /* length of input block */
  875.     int last;         /* one if this is the last block for a file */
  876. {
  877.     send_bits(s, (STORED_BLOCK<<1)+last, 3);    /* send block type */
  878. #ifdef DEBUG
  879.     s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
  880.     s->compressed_len += (stored_len + 4) << 3;
  881. #endif
  882.     copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
  883. }
  884.  
  885. /* ===========================================================================
  886.  * Send one empty static block to give enough lookahead for inflate.
  887.  * This takes 10 bits, of which 7 may remain in the bit buffer.
  888.  * The current inflate code requires 9 bits of lookahead. If the
  889.  * last two codes for the previous block (real code plus EOB) were coded
  890.  * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode
  891.  * the last real code. In this case we send two empty static blocks instead
  892.  * of one. (There are no problems if the previous block is stored or fixed.)
  893.  * To simplify the code, we assume the worst case of last real code encoded
  894.  * on one bit only.
  895.  */
  896. void ZLIB_INTERNAL _tr_align(s)
  897.     deflate_state *s;
  898. {
  899.     send_bits(s, STATIC_TREES<<1, 3);
  900.     send_code(s, END_BLOCK, static_ltree);
  901. #ifdef DEBUG
  902.     s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
  903. #endif
  904.     bi_flush(s);
  905.     /* Of the 10 bits for the empty block, we have already sent
  906.      * (10 - bi_valid) bits. The lookahead for the last real code (before
  907.      * the EOB of the previous block) was thus at least one plus the length
  908.      * of the EOB plus what we have just sent of the empty static block.
  909.      */
  910.     if (1 + s->last_eob_len + 10 - s->bi_valid < 9) {
  911.         send_bits(s, STATIC_TREES<<1, 3);
  912.         send_code(s, END_BLOCK, static_ltree);
  913. #ifdef DEBUG
  914.         s->compressed_len += 10L;
  915. #endif
  916.         bi_flush(s);
  917.     }
  918.     s->last_eob_len = 7;
  919. }
  920.  
  921. /* ===========================================================================
  922.  * Determine the best encoding for the current block: dynamic trees, static
  923.  * trees or store, and output the encoded block to the zip file.
  924.  */
  925. void ZLIB_INTERNAL _tr_flush_block(s, buf, stored_len, last)
  926.     deflate_state *s;
  927.     charf *buf;       /* input block, or NULL if too old */
  928.     ulg stored_len;   /* length of input block */
  929.     int last;         /* one if this is the last block for a file */
  930. {
  931.     ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
  932.     int max_blindex = 0;  /* index of last bit length code of non zero freq */
  933.  
  934.     /* Build the Huffman trees unless a stored block is forced */
  935.     if (s->level > 0) {
  936.  
  937.         /* Check if the file is binary or text */
  938.         if (s->strm->data_type == Z_UNKNOWN)
  939.             s->strm->data_type = detect_data_type(s);
  940.  
  941.         /* Construct the literal and distance trees */
  942.         build_tree(s, (tree_desc *)(&(s->l_desc)));
  943.         Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
  944.                 s->static_len));
  945.  
  946.         build_tree(s, (tree_desc *)(&(s->d_desc)));
  947.         Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
  948.                 s->static_len));
  949.         /* At this point, opt_len and static_len are the total bit lengths of
  950.          * the compressed block data, excluding the tree representations.
  951.          */
  952.  
  953.         /* Build the bit length tree for the above two trees, and get the index
  954.          * in bl_order of the last bit length code to send.
  955.          */
  956.         max_blindex = build_bl_tree(s);
  957.  
  958.         /* Determine the best encoding. Compute the block lengths in bytes. */
  959.         opt_lenb = (s->opt_len+3+7)>>3;
  960.         static_lenb = (s->static_len+3+7)>>3;
  961.  
  962.         Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
  963.                 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
  964.                 s->last_lit));
  965.  
  966.         if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
  967.  
  968.     } else {
  969.         Assert(buf != (char*)0, "lost buf");
  970.         opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
  971.     }
  972.  
  973. #ifdef FORCE_STORED
  974.     if (buf != (char*)0) { /* force stored block */
  975. #else
  976.     if (stored_len+4 <= opt_lenb && buf != (char*)0) {
  977.                        /* 4: two words for the lengths */
  978. #endif
  979.         /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
  980.          * Otherwise we can't have processed more than WSIZE input bytes since
  981.          * the last block flush, because compression would have been
  982.          * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
  983.          * transform a block into a stored block.
  984.          */
  985.         _tr_stored_block(s, buf, stored_len, last);
  986.  
  987. #ifdef FORCE_STATIC
  988.     } else if (static_lenb >= 0) { /* force static trees */
  989. #else
  990.     } else if (s->strategy == Z_FIXED || static_lenb == opt_lenb) {
  991. #endif
  992.         send_bits(s, (STATIC_TREES<<1)+last, 3);
  993.         compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
  994. #ifdef DEBUG
  995.         s->compressed_len += 3 + s->static_len;
  996. #endif
  997.     } else {
  998.         send_bits(s, (DYN_TREES<<1)+last, 3);
  999.         send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
  1000.                        max_blindex+1);
  1001.         compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
  1002. #ifdef DEBUG
  1003.         s->compressed_len += 3 + s->opt_len;
  1004. #endif
  1005.     }
  1006.     Assert (s->compressed_len == s->bits_sent, "bad compressed size");
  1007.     /* The above check is made mod 2^32, for files larger than 512 MB
  1008.      * and uLong implemented on 32 bits.
  1009.      */
  1010.     init_block(s);
  1011.  
  1012.     if (last) {
  1013.         bi_windup(s);
  1014. #ifdef DEBUG
  1015.         s->compressed_len += 7;  /* align on byte boundary */
  1016. #endif
  1017.     }
  1018.     Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
  1019.            s->compressed_len-7*last));
  1020. }
  1021.  
  1022. /* ===========================================================================
  1023.  * Save the match info and tally the frequency counts. Return true if
  1024.  * the current block must be flushed.
  1025.  */
  1026. int ZLIB_INTERNAL _tr_tally (s, dist, lc)
  1027.     deflate_state *s;
  1028.     unsigned dist;  /* distance of matched string */
  1029.     unsigned lc;    /* match length-MIN_MATCH or unmatched char (if dist==0) */
  1030. {
  1031.     s->d_buf[s->last_lit] = (ush)dist;
  1032.     s->l_buf[s->last_lit++] = (uch)lc;
  1033.     if (dist == 0) {
  1034.         /* lc is the unmatched char */
  1035.         s->dyn_ltree[lc].Freq++;
  1036.     } else {
  1037.         s->matches++;
  1038.         /* Here, lc is the match length - MIN_MATCH */
  1039.         dist--;             /* dist = match distance - 1 */
  1040.         Assert((ush)dist < (ush)MAX_DIST(s) &&
  1041.                (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
  1042.                (ush)d_code(dist) < (ush)D_CODES,  "_tr_tally: bad match");
  1043.  
  1044.         s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++;
  1045.         s->dyn_dtree[d_code(dist)].Freq++;
  1046.     }
  1047.  
  1048. #ifdef TRUNCATE_BLOCK
  1049.     /* Try to guess if it is profitable to stop the current block here */
  1050.     if ((s->last_lit & 0x1fff) == 0 && s->level > 2) {
  1051.         /* Compute an upper bound for the compressed length */
  1052.         ulg out_length = (ulg)s->last_lit*8L;
  1053.         ulg in_length = (ulg)((long)s->strstart - s->block_start);
  1054.         int dcode;
  1055.         for (dcode = 0; dcode < D_CODES; dcode++) {
  1056.             out_length += (ulg)s->dyn_dtree[dcode].Freq *
  1057.                 (5L+extra_dbits[dcode]);
  1058.         }
  1059.         out_length >>= 3;
  1060.         Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
  1061.                s->last_lit, in_length, out_length,
  1062.                100L - out_length*100L/in_length));
  1063.         if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
  1064.     }
  1065. #endif
  1066.     return (s->last_lit == s->lit_bufsize-1);
  1067.     /* We avoid equality with lit_bufsize because of wraparound at 64K
  1068.      * on 16 bit machines and because stored blocks are restricted to
  1069.      * 64K-1 bytes.
  1070.      */
  1071. }
  1072.  
  1073. /* ===========================================================================
  1074.  * Send the block data compressed using the given Huffman trees
  1075.  */
  1076. local void compress_block(s, ltree, dtree)
  1077.     deflate_state *s;
  1078.     ct_data *ltree; /* literal tree */
  1079.     ct_data *dtree; /* distance tree */
  1080. {
  1081.     unsigned dist;      /* distance of matched string */
  1082.     int lc;             /* match length or unmatched char (if dist == 0) */
  1083.     unsigned lx = 0;    /* running index in l_buf */
  1084.     unsigned code;      /* the code to send */
  1085.     int extra;          /* number of extra bits to send */
  1086.  
  1087.     if (s->last_lit != 0) do {
  1088.         dist = s->d_buf[lx];
  1089.         lc = s->l_buf[lx++];
  1090.         if (dist == 0) {
  1091.             send_code(s, lc, ltree); /* send a literal byte */
  1092.             Tracecv(isgraph(lc), (stderr," '%c' ", lc));
  1093.         } else {
  1094.             /* Here, lc is the match length - MIN_MATCH */
  1095.             code = _length_code[lc];
  1096.             send_code(s, code+LITERALS+1, ltree); /* send the length code */
  1097.             extra = extra_lbits[code];
  1098.             if (extra != 0) {
  1099.                 lc -= base_length[code];
  1100.                 send_bits(s, lc, extra);       /* send the extra length bits */
  1101.             }
  1102.             dist--; /* dist is now the match distance - 1 */
  1103.             code = d_code(dist);
  1104.             Assert (code < D_CODES, "bad d_code");
  1105.  
  1106.             send_code(s, code, dtree);       /* send the distance code */
  1107.             extra = extra_dbits[code];
  1108.             if (extra != 0) {
  1109.                 dist -= base_dist[code];
  1110.                 send_bits(s, dist, extra);   /* send the extra distance bits */
  1111.             }
  1112.         } /* literal or match pair ? */
  1113.  
  1114.         /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
  1115.         Assert((uInt)(s->pending) < s->lit_bufsize + 2*lx,
  1116.                "pendingBuf overflow");
  1117.  
  1118.     } while (lx < s->last_lit);
  1119.  
  1120.     send_code(s, END_BLOCK, ltree);
  1121.     s->last_eob_len = ltree[END_BLOCK].Len;
  1122. }
  1123.  
  1124. /* ===========================================================================
  1125.  * Check if the data type is TEXT or BINARY, using the following algorithm:
  1126.  * - TEXT if the two conditions below are satisfied:
  1127.  *    a) There are no non-portable control characters belonging to the
  1128.  *       "black list" (0..6, 14..25, 28..31).
  1129.  *    b) There is at least one printable character belonging to the
  1130.  *       "white list" (9 {TAB}, 10 {LF}, 13 {CR}, 32..255).
  1131.  * - BINARY otherwise.
  1132.  * - The following partially-portable control characters form a
  1133.  *   "gray list" that is ignored in this detection algorithm:
  1134.  *   (7 {BEL}, 8 {BS}, 11 {VT}, 12 {FF}, 26 {SUB}, 27 {ESC}).
  1135.  * IN assertion: the fields Freq of dyn_ltree are set.
  1136.  */
  1137. local int detect_data_type(s)
  1138.     deflate_state *s;
  1139. {
  1140.     /* black_mask is the bit mask of black-listed bytes
  1141.      * set bits 0..6, 14..25, and 28..31
  1142.      * 0xf3ffc07f = binary 11110011111111111100000001111111
  1143.      */
  1144.     unsigned long black_mask = 0xf3ffc07fUL;
  1145.     int n;
  1146.  
  1147.     /* Check for non-textual ("black-listed") bytes. */
  1148.     for (n = 0; n <= 31; n++, black_mask >>= 1)
  1149.         if ((black_mask & 1) && (s->dyn_ltree[n].Freq != 0))
  1150.             return Z_BINARY;
  1151.  
  1152.     /* Check for textual ("white-listed") bytes. */
  1153.     if (s->dyn_ltree[9].Freq != 0 || s->dyn_ltree[10].Freq != 0
  1154.             || s->dyn_ltree[13].Freq != 0)
  1155.         return Z_TEXT;
  1156.     for (n = 32; n < LITERALS; n++)
  1157.         if (s->dyn_ltree[n].Freq != 0)
  1158.             return Z_TEXT;
  1159.  
  1160.     /* There are no "black-listed" or "white-listed" bytes:
  1161.      * this stream either is empty or has tolerated ("gray-listed") bytes only.
  1162.      */
  1163.     return Z_BINARY;
  1164. }
  1165.  
  1166. /* ===========================================================================
  1167.  * Reverse the first len bits of a code, using straightforward code (a faster
  1168.  * method would use a table)
  1169.  * IN assertion: 1 <= len <= 15
  1170.  */
  1171. local unsigned bi_reverse(code, len)
  1172.     unsigned code; /* the value to invert */
  1173.     int len;       /* its bit length */
  1174. {
  1175.     register unsigned res = 0;
  1176.     do {
  1177.         res |= code & 1;
  1178.         code >>= 1, res <<= 1;
  1179.     } while (--len > 0);
  1180.     return res >> 1;
  1181. }
  1182.  
  1183. /* ===========================================================================
  1184.  * Flush the bit buffer, keeping at most 7 bits in it.
  1185.  */
  1186. local void bi_flush(s)
  1187.     deflate_state *s;
  1188. {
  1189.     if (s->bi_valid == 16) {
  1190.         put_short(s, s->bi_buf);
  1191.         s->bi_buf = 0;
  1192.         s->bi_valid = 0;
  1193.     } else if (s->bi_valid >= 8) {
  1194.         put_byte(s, (Byte)s->bi_buf);
  1195.         s->bi_buf >>= 8;
  1196.         s->bi_valid -= 8;
  1197.     }
  1198. }
  1199.  
  1200. /* ===========================================================================
  1201.  * Flush the bit buffer and align the output on a byte boundary
  1202.  */
  1203. local void bi_windup(s)
  1204.     deflate_state *s;
  1205. {
  1206.     if (s->bi_valid > 8) {
  1207.         put_short(s, s->bi_buf);
  1208.     } else if (s->bi_valid > 0) {
  1209.         put_byte(s, (Byte)s->bi_buf);
  1210.     }
  1211.     s->bi_buf = 0;
  1212.     s->bi_valid = 0;
  1213. #ifdef DEBUG
  1214.     s->bits_sent = (s->bits_sent+7) & ~7;
  1215. #endif
  1216. }
  1217.  
  1218. /* ===========================================================================
  1219.  * Copy a stored block, storing first the length and its
  1220.  * one's complement if requested.
  1221.  */
  1222. local void copy_block(s, buf, len, header)
  1223.     deflate_state *s;
  1224.     charf    *buf;    /* the input data */
  1225.     unsigned len;     /* its length */
  1226.     int      header;  /* true if block header must be written */
  1227. {
  1228.     bi_windup(s);        /* align on byte boundary */
  1229.     s->last_eob_len = 8; /* enough lookahead for inflate */
  1230.  
  1231.     if (header) {
  1232.         put_short(s, (ush)len);
  1233.         put_short(s, (ush)~len);
  1234. #ifdef DEBUG
  1235.         s->bits_sent += 2*16;
  1236. #endif
  1237.     }
  1238. #ifdef DEBUG
  1239.     s->bits_sent += (ulg)len<<3;
  1240. #endif
  1241.     while (len--) {
  1242.         put_byte(s, *buf++);
  1243.     }
  1244. }
  1245.