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0001 /* +++ trees.c */
0002 /* trees.c -- output deflated data using Huffman coding
0003  * Copyright (C) 1995-1996 Jean-loup Gailly
0004  * For conditions of distribution and use, see copyright notice in zlib.h 
0005  */
0006 
0007 /*
0008  *  ALGORITHM
0009  *
0010  *      The "deflation" process uses several Huffman trees. The more
0011  *      common source values are represented by shorter bit sequences.
0012  *
0013  *      Each code tree is stored in a compressed form which is itself
0014  * a Huffman encoding of the lengths of all the code strings (in
0015  * ascending order by source values).  The actual code strings are
0016  * reconstructed from the lengths in the inflate process, as described
0017  * in the deflate specification.
0018  *
0019  *  REFERENCES
0020  *
0021  *      Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
0022  *      Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
0023  *
0024  *      Storer, James A.
0025  *          Data Compression:  Methods and Theory, pp. 49-50.
0026  *          Computer Science Press, 1988.  ISBN 0-7167-8156-5.
0027  *
0028  *      Sedgewick, R.
0029  *          Algorithms, p290.
0030  *          Addison-Wesley, 1983. ISBN 0-201-06672-6.
0031  */
0032 
0033 /* From: trees.c,v 1.11 1996/07/24 13:41:06 me Exp $ */
0034 
0035 /* #include "deflate.h" */
0036 
0037 #include <linux/zutil.h>
0038 #include <linux/bitrev.h>
0039 #include "defutil.h"
0040 
0041 #ifdef DEBUG_ZLIB
0042 #  include <ctype.h>
0043 #endif
0044 
0045 /* ===========================================================================
0046  * Constants
0047  */
0048 
0049 #define MAX_BL_BITS 7
0050 /* Bit length codes must not exceed MAX_BL_BITS bits */
0051 
0052 #define END_BLOCK 256
0053 /* end of block literal code */
0054 
0055 #define REP_3_6      16
0056 /* repeat previous bit length 3-6 times (2 bits of repeat count) */
0057 
0058 #define REPZ_3_10    17
0059 /* repeat a zero length 3-10 times  (3 bits of repeat count) */
0060 
0061 #define REPZ_11_138  18
0062 /* repeat a zero length 11-138 times  (7 bits of repeat count) */
0063 
0064 static const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */
0065    = {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};
0066 
0067 static const int extra_dbits[D_CODES] /* extra bits for each distance code */
0068    = {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};
0069 
0070 static const int extra_blbits[BL_CODES]/* extra bits for each bit length code */
0071    = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
0072 
0073 static const uch bl_order[BL_CODES]
0074    = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
0075 /* The lengths of the bit length codes are sent in order of decreasing
0076  * probability, to avoid transmitting the lengths for unused bit length codes.
0077  */
0078 
0079 /* ===========================================================================
0080  * Local data. These are initialized only once.
0081  */
0082 
0083 static ct_data static_ltree[L_CODES+2];
0084 /* The static literal tree. Since the bit lengths are imposed, there is no
0085  * need for the L_CODES extra codes used during heap construction. However
0086  * The codes 286 and 287 are needed to build a canonical tree (see zlib_tr_init
0087  * below).
0088  */
0089 
0090 static ct_data static_dtree[D_CODES];
0091 /* The static distance tree. (Actually a trivial tree since all codes use
0092  * 5 bits.)
0093  */
0094 
0095 static uch dist_code[512];
0096 /* distance codes. The first 256 values correspond to the distances
0097  * 3 .. 258, the last 256 values correspond to the top 8 bits of
0098  * the 15 bit distances.
0099  */
0100 
0101 static uch length_code[MAX_MATCH-MIN_MATCH+1];
0102 /* length code for each normalized match length (0 == MIN_MATCH) */
0103 
0104 static int base_length[LENGTH_CODES];
0105 /* First normalized length for each code (0 = MIN_MATCH) */
0106 
0107 static int base_dist[D_CODES];
0108 /* First normalized distance for each code (0 = distance of 1) */
0109 
0110 struct static_tree_desc_s {
0111     const ct_data *static_tree;  /* static tree or NULL */
0112     const int *extra_bits;       /* extra bits for each code or NULL */
0113     int     extra_base;          /* base index for extra_bits */
0114     int     elems;               /* max number of elements in the tree */
0115     int     max_length;          /* max bit length for the codes */
0116 };
0117 
0118 static static_tree_desc  static_l_desc =
0119 {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
0120 
0121 static static_tree_desc  static_d_desc =
0122 {static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};
0123 
0124 static static_tree_desc  static_bl_desc =
0125 {(const ct_data *)0, extra_blbits, 0,   BL_CODES, MAX_BL_BITS};
0126 
0127 /* ===========================================================================
0128  * Local (static) routines in this file.
0129  */
0130 
0131 static void tr_static_init (void);
0132 static void init_block     (deflate_state *s);
0133 static void pqdownheap     (deflate_state *s, ct_data *tree, int k);
0134 static void gen_bitlen     (deflate_state *s, tree_desc *desc);
0135 static void gen_codes      (ct_data *tree, int max_code, ush *bl_count);
0136 static void build_tree     (deflate_state *s, tree_desc *desc);
0137 static void scan_tree      (deflate_state *s, ct_data *tree, int max_code);
0138 static void send_tree      (deflate_state *s, ct_data *tree, int max_code);
0139 static int  build_bl_tree  (deflate_state *s);
0140 static void send_all_trees (deflate_state *s, int lcodes, int dcodes,
0141                            int blcodes);
0142 static void compress_block (deflate_state *s, ct_data *ltree,
0143                            ct_data *dtree);
0144 static void set_data_type  (deflate_state *s);
0145 static void bi_flush       (deflate_state *s);
0146 static void copy_block     (deflate_state *s, char *buf, unsigned len,
0147                            int header);
0148 
0149 #ifndef DEBUG_ZLIB
0150 #  define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
0151    /* Send a code of the given tree. c and tree must not have side effects */
0152 
0153 #else /* DEBUG_ZLIB */
0154 #  define send_code(s, c, tree) \
0155      { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
0156        send_bits(s, tree[c].Code, tree[c].Len); }
0157 #endif
0158 
0159 #define d_code(dist) \
0160    ((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)])
0161 /* Mapping from a distance to a distance code. dist is the distance - 1 and
0162  * must not have side effects. dist_code[256] and dist_code[257] are never
0163  * used.
0164  */
0165 
0166 /* ===========================================================================
0167  * Initialize the various 'constant' tables. In a multi-threaded environment,
0168  * this function may be called by two threads concurrently, but this is
0169  * harmless since both invocations do exactly the same thing.
0170  */
0171 static void tr_static_init(void)
0172 {
0173     static int static_init_done;
0174     int n;        /* iterates over tree elements */
0175     int bits;     /* bit counter */
0176     int length;   /* length value */
0177     int code;     /* code value */
0178     int dist;     /* distance index */
0179     ush bl_count[MAX_BITS+1];
0180     /* number of codes at each bit length for an optimal tree */
0181 
0182     if (static_init_done) return;
0183 
0184     /* Initialize the mapping length (0..255) -> length code (0..28) */
0185     length = 0;
0186     for (code = 0; code < LENGTH_CODES-1; code++) {
0187         base_length[code] = length;
0188         for (n = 0; n < (1<<extra_lbits[code]); n++) {
0189             length_code[length++] = (uch)code;
0190         }
0191     }
0192     Assert (length == 256, "tr_static_init: length != 256");
0193     /* Note that the length 255 (match length 258) can be represented
0194      * in two different ways: code 284 + 5 bits or code 285, so we
0195      * overwrite length_code[255] to use the best encoding:
0196      */
0197     length_code[length-1] = (uch)code;
0198 
0199     /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
0200     dist = 0;
0201     for (code = 0 ; code < 16; code++) {
0202         base_dist[code] = dist;
0203         for (n = 0; n < (1<<extra_dbits[code]); n++) {
0204             dist_code[dist++] = (uch)code;
0205         }
0206     }
0207     Assert (dist == 256, "tr_static_init: dist != 256");
0208     dist >>= 7; /* from now on, all distances are divided by 128 */
0209     for ( ; code < D_CODES; code++) {
0210         base_dist[code] = dist << 7;
0211         for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
0212             dist_code[256 + dist++] = (uch)code;
0213         }
0214     }
0215     Assert (dist == 256, "tr_static_init: 256+dist != 512");
0216 
0217     /* Construct the codes of the static literal tree */
0218     for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
0219     n = 0;
0220     while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
0221     while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
0222     while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
0223     while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
0224     /* Codes 286 and 287 do not exist, but we must include them in the
0225      * tree construction to get a canonical Huffman tree (longest code
0226      * all ones)
0227      */
0228     gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
0229 
0230     /* The static distance tree is trivial: */
0231     for (n = 0; n < D_CODES; n++) {
0232         static_dtree[n].Len = 5;
0233         static_dtree[n].Code = bitrev32((u32)n) >> (32 - 5);
0234     }
0235     static_init_done = 1;
0236 }
0237 
0238 /* ===========================================================================
0239  * Initialize the tree data structures for a new zlib stream.
0240  */
0241 void zlib_tr_init(
0242     deflate_state *s
0243 )
0244 {
0245     tr_static_init();
0246 
0247     s->compressed_len = 0L;
0248 
0249     s->l_desc.dyn_tree = s->dyn_ltree;
0250     s->l_desc.stat_desc = &static_l_desc;
0251 
0252     s->d_desc.dyn_tree = s->dyn_dtree;
0253     s->d_desc.stat_desc = &static_d_desc;
0254 
0255     s->bl_desc.dyn_tree = s->bl_tree;
0256     s->bl_desc.stat_desc = &static_bl_desc;
0257 
0258     s->bi_buf = 0;
0259     s->bi_valid = 0;
0260     s->last_eob_len = 8; /* enough lookahead for inflate */
0261 #ifdef DEBUG_ZLIB
0262     s->bits_sent = 0L;
0263 #endif
0264 
0265     /* Initialize the first block of the first file: */
0266     init_block(s);
0267 }
0268 
0269 /* ===========================================================================
0270  * Initialize a new block.
0271  */
0272 static void init_block(
0273     deflate_state *s
0274 )
0275 {
0276     int n; /* iterates over tree elements */
0277 
0278     /* Initialize the trees. */
0279     for (n = 0; n < L_CODES;  n++) s->dyn_ltree[n].Freq = 0;
0280     for (n = 0; n < D_CODES;  n++) s->dyn_dtree[n].Freq = 0;
0281     for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
0282 
0283     s->dyn_ltree[END_BLOCK].Freq = 1;
0284     s->opt_len = s->static_len = 0L;
0285     s->last_lit = s->matches = 0;
0286 }
0287 
0288 #define SMALLEST 1
0289 /* Index within the heap array of least frequent node in the Huffman tree */
0290 
0291 
0292 /* ===========================================================================
0293  * Remove the smallest element from the heap and recreate the heap with
0294  * one less element. Updates heap and heap_len.
0295  */
0296 #define pqremove(s, tree, top) \
0297 {\
0298     top = s->heap[SMALLEST]; \
0299     s->heap[SMALLEST] = s->heap[s->heap_len--]; \
0300     pqdownheap(s, tree, SMALLEST); \
0301 }
0302 
0303 /* ===========================================================================
0304  * Compares to subtrees, using the tree depth as tie breaker when
0305  * the subtrees have equal frequency. This minimizes the worst case length.
0306  */
0307 #define smaller(tree, n, m, depth) \
0308    (tree[n].Freq < tree[m].Freq || \
0309    (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
0310 
0311 /* ===========================================================================
0312  * Restore the heap property by moving down the tree starting at node k,
0313  * exchanging a node with the smallest of its two sons if necessary, stopping
0314  * when the heap property is re-established (each father smaller than its
0315  * two sons).
0316  */
0317 static void pqdownheap(
0318     deflate_state *s,
0319     ct_data *tree,  /* the tree to restore */
0320     int k       /* node to move down */
0321 )
0322 {
0323     int v = s->heap[k];
0324     int j = k << 1;  /* left son of k */
0325     while (j <= s->heap_len) {
0326         /* Set j to the smallest of the two sons: */
0327         if (j < s->heap_len &&
0328             smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
0329             j++;
0330         }
0331         /* Exit if v is smaller than both sons */
0332         if (smaller(tree, v, s->heap[j], s->depth)) break;
0333 
0334         /* Exchange v with the smallest son */
0335         s->heap[k] = s->heap[j];  k = j;
0336 
0337         /* And continue down the tree, setting j to the left son of k */
0338         j <<= 1;
0339     }
0340     s->heap[k] = v;
0341 }
0342 
0343 /* ===========================================================================
0344  * Compute the optimal bit lengths for a tree and update the total bit length
0345  * for the current block.
0346  * IN assertion: the fields freq and dad are set, heap[heap_max] and
0347  *    above are the tree nodes sorted by increasing frequency.
0348  * OUT assertions: the field len is set to the optimal bit length, the
0349  *     array bl_count contains the frequencies for each bit length.
0350  *     The length opt_len is updated; static_len is also updated if stree is
0351  *     not null.
0352  */
0353 static void gen_bitlen(
0354     deflate_state *s,
0355     tree_desc *desc    /* the tree descriptor */
0356 )
0357 {
0358     ct_data *tree        = desc->dyn_tree;
0359     int max_code         = desc->max_code;
0360     const ct_data *stree = desc->stat_desc->static_tree;
0361     const int *extra     = desc->stat_desc->extra_bits;
0362     int base             = desc->stat_desc->extra_base;
0363     int max_length       = desc->stat_desc->max_length;
0364     int h;              /* heap index */
0365     int n, m;           /* iterate over the tree elements */
0366     int bits;           /* bit length */
0367     int xbits;          /* extra bits */
0368     ush f;              /* frequency */
0369     int overflow = 0;   /* number of elements with bit length too large */
0370 
0371     for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
0372 
0373     /* In a first pass, compute the optimal bit lengths (which may
0374      * overflow in the case of the bit length tree).
0375      */
0376     tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
0377 
0378     for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
0379         n = s->heap[h];
0380         bits = tree[tree[n].Dad].Len + 1;
0381         if (bits > max_length) bits = max_length, overflow++;
0382         tree[n].Len = (ush)bits;
0383         /* We overwrite tree[n].Dad which is no longer needed */
0384 
0385         if (n > max_code) continue; /* not a leaf node */
0386 
0387         s->bl_count[bits]++;
0388         xbits = 0;
0389         if (n >= base) xbits = extra[n-base];
0390         f = tree[n].Freq;
0391         s->opt_len += (ulg)f * (bits + xbits);
0392         if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
0393     }
0394     if (overflow == 0) return;
0395 
0396     Trace((stderr,"\nbit length overflow\n"));
0397     /* This happens for example on obj2 and pic of the Calgary corpus */
0398 
0399     /* Find the first bit length which could increase: */
0400     do {
0401         bits = max_length-1;
0402         while (s->bl_count[bits] == 0) bits--;
0403         s->bl_count[bits]--;      /* move one leaf down the tree */
0404         s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
0405         s->bl_count[max_length]--;
0406         /* The brother of the overflow item also moves one step up,
0407          * but this does not affect bl_count[max_length]
0408          */
0409         overflow -= 2;
0410     } while (overflow > 0);
0411 
0412     /* Now recompute all bit lengths, scanning in increasing frequency.
0413      * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
0414      * lengths instead of fixing only the wrong ones. This idea is taken
0415      * from 'ar' written by Haruhiko Okumura.)
0416      */
0417     for (bits = max_length; bits != 0; bits--) {
0418         n = s->bl_count[bits];
0419         while (n != 0) {
0420             m = s->heap[--h];
0421             if (m > max_code) continue;
0422             if (tree[m].Len != (unsigned) bits) {
0423                 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
0424                 s->opt_len += ((long)bits - (long)tree[m].Len)
0425                               *(long)tree[m].Freq;
0426                 tree[m].Len = (ush)bits;
0427             }
0428             n--;
0429         }
0430     }
0431 }
0432 
0433 /* ===========================================================================
0434  * Generate the codes for a given tree and bit counts (which need not be
0435  * optimal).
0436  * IN assertion: the array bl_count contains the bit length statistics for
0437  * the given tree and the field len is set for all tree elements.
0438  * OUT assertion: the field code is set for all tree elements of non
0439  *     zero code length.
0440  */
0441 static void gen_codes(
0442     ct_data *tree,             /* the tree to decorate */
0443     int max_code,              /* largest code with non zero frequency */
0444     ush *bl_count             /* number of codes at each bit length */
0445 )
0446 {
0447     ush next_code[MAX_BITS+1]; /* next code value for each bit length */
0448     ush code = 0;              /* running code value */
0449     int bits;                  /* bit index */
0450     int n;                     /* code index */
0451 
0452     /* The distribution counts are first used to generate the code values
0453      * without bit reversal.
0454      */
0455     for (bits = 1; bits <= MAX_BITS; bits++) {
0456         next_code[bits] = code = (code + bl_count[bits-1]) << 1;
0457     }
0458     /* Check that the bit counts in bl_count are consistent. The last code
0459      * must be all ones.
0460      */
0461     Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
0462             "inconsistent bit counts");
0463     Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
0464 
0465     for (n = 0;  n <= max_code; n++) {
0466         int len = tree[n].Len;
0467         if (len == 0) continue;
0468         /* Now reverse the bits */
0469         tree[n].Code = bitrev32((u32)(next_code[len]++)) >> (32 - len);
0470 
0471         Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
0472              n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
0473     }
0474 }
0475 
0476 /* ===========================================================================
0477  * Construct one Huffman tree and assigns the code bit strings and lengths.
0478  * Update the total bit length for the current block.
0479  * IN assertion: the field freq is set for all tree elements.
0480  * OUT assertions: the fields len and code are set to the optimal bit length
0481  *     and corresponding code. The length opt_len is updated; static_len is
0482  *     also updated if stree is not null. The field max_code is set.
0483  */
0484 static void build_tree(
0485     deflate_state *s,
0486     tree_desc *desc  /* the tree descriptor */
0487 )
0488 {
0489     ct_data *tree         = desc->dyn_tree;
0490     const ct_data *stree  = desc->stat_desc->static_tree;
0491     int elems             = desc->stat_desc->elems;
0492     int n, m;          /* iterate over heap elements */
0493     int max_code = -1; /* largest code with non zero frequency */
0494     int node;          /* new node being created */
0495 
0496     /* Construct the initial heap, with least frequent element in
0497      * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
0498      * heap[0] is not used.
0499      */
0500     s->heap_len = 0, s->heap_max = HEAP_SIZE;
0501 
0502     for (n = 0; n < elems; n++) {
0503         if (tree[n].Freq != 0) {
0504             s->heap[++(s->heap_len)] = max_code = n;
0505             s->depth[n] = 0;
0506         } else {
0507             tree[n].Len = 0;
0508         }
0509     }
0510 
0511     /* The pkzip format requires that at least one distance code exists,
0512      * and that at least one bit should be sent even if there is only one
0513      * possible code. So to avoid special checks later on we force at least
0514      * two codes of non zero frequency.
0515      */
0516     while (s->heap_len < 2) {
0517         node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
0518         tree[node].Freq = 1;
0519         s->depth[node] = 0;
0520         s->opt_len--; if (stree) s->static_len -= stree[node].Len;
0521         /* node is 0 or 1 so it does not have extra bits */
0522     }
0523     desc->max_code = max_code;
0524 
0525     /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
0526      * establish sub-heaps of increasing lengths:
0527      */
0528     for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
0529 
0530     /* Construct the Huffman tree by repeatedly combining the least two
0531      * frequent nodes.
0532      */
0533     node = elems;              /* next internal node of the tree */
0534     do {
0535         pqremove(s, tree, n);  /* n = node of least frequency */
0536         m = s->heap[SMALLEST]; /* m = node of next least frequency */
0537 
0538         s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
0539         s->heap[--(s->heap_max)] = m;
0540 
0541         /* Create a new node father of n and m */
0542         tree[node].Freq = tree[n].Freq + tree[m].Freq;
0543         s->depth[node] = (uch) (max(s->depth[n], s->depth[m]) + 1);
0544         tree[n].Dad = tree[m].Dad = (ush)node;
0545 #ifdef DUMP_BL_TREE
0546         if (tree == s->bl_tree) {
0547             fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
0548                     node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
0549         }
0550 #endif
0551         /* and insert the new node in the heap */
0552         s->heap[SMALLEST] = node++;
0553         pqdownheap(s, tree, SMALLEST);
0554 
0555     } while (s->heap_len >= 2);
0556 
0557     s->heap[--(s->heap_max)] = s->heap[SMALLEST];
0558 
0559     /* At this point, the fields freq and dad are set. We can now
0560      * generate the bit lengths.
0561      */
0562     gen_bitlen(s, (tree_desc *)desc);
0563 
0564     /* The field len is now set, we can generate the bit codes */
0565     gen_codes ((ct_data *)tree, max_code, s->bl_count);
0566 }
0567 
0568 /* ===========================================================================
0569  * Scan a literal or distance tree to determine the frequencies of the codes
0570  * in the bit length tree.
0571  */
0572 static void scan_tree(
0573     deflate_state *s,
0574     ct_data *tree,   /* the tree to be scanned */
0575     int max_code     /* and its largest code of non zero frequency */
0576 )
0577 {
0578     int n;                     /* iterates over all tree elements */
0579     int prevlen = -1;          /* last emitted length */
0580     int curlen;                /* length of current code */
0581     int nextlen = tree[0].Len; /* length of next code */
0582     int count = 0;             /* repeat count of the current code */
0583     int max_count = 7;         /* max repeat count */
0584     int min_count = 4;         /* min repeat count */
0585 
0586     if (nextlen == 0) max_count = 138, min_count = 3;
0587     tree[max_code+1].Len = (ush)0xffff; /* guard */
0588 
0589     for (n = 0; n <= max_code; n++) {
0590         curlen = nextlen; nextlen = tree[n+1].Len;
0591         if (++count < max_count && curlen == nextlen) {
0592             continue;
0593         } else if (count < min_count) {
0594             s->bl_tree[curlen].Freq += count;
0595         } else if (curlen != 0) {
0596             if (curlen != prevlen) s->bl_tree[curlen].Freq++;
0597             s->bl_tree[REP_3_6].Freq++;
0598         } else if (count <= 10) {
0599             s->bl_tree[REPZ_3_10].Freq++;
0600         } else {
0601             s->bl_tree[REPZ_11_138].Freq++;
0602         }
0603         count = 0; prevlen = curlen;
0604         if (nextlen == 0) {
0605             max_count = 138, min_count = 3;
0606         } else if (curlen == nextlen) {
0607             max_count = 6, min_count = 3;
0608         } else {
0609             max_count = 7, min_count = 4;
0610         }
0611     }
0612 }
0613 
0614 /* ===========================================================================
0615  * Send a literal or distance tree in compressed form, using the codes in
0616  * bl_tree.
0617  */
0618 static void send_tree(
0619     deflate_state *s,
0620     ct_data *tree, /* the tree to be scanned */
0621     int max_code   /* and its largest code of non zero frequency */
0622 )
0623 {
0624     int n;                     /* iterates over all tree elements */
0625     int prevlen = -1;          /* last emitted length */
0626     int curlen;                /* length of current code */
0627     int nextlen = tree[0].Len; /* length of next code */
0628     int count = 0;             /* repeat count of the current code */
0629     int max_count = 7;         /* max repeat count */
0630     int min_count = 4;         /* min repeat count */
0631 
0632     /* tree[max_code+1].Len = -1; */  /* guard already set */
0633     if (nextlen == 0) max_count = 138, min_count = 3;
0634 
0635     for (n = 0; n <= max_code; n++) {
0636         curlen = nextlen; nextlen = tree[n+1].Len;
0637         if (++count < max_count && curlen == nextlen) {
0638             continue;
0639         } else if (count < min_count) {
0640             do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
0641 
0642         } else if (curlen != 0) {
0643             if (curlen != prevlen) {
0644                 send_code(s, curlen, s->bl_tree); count--;
0645             }
0646             Assert(count >= 3 && count <= 6, " 3_6?");
0647             send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
0648 
0649         } else if (count <= 10) {
0650             send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
0651 
0652         } else {
0653             send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
0654         }
0655         count = 0; prevlen = curlen;
0656         if (nextlen == 0) {
0657             max_count = 138, min_count = 3;
0658         } else if (curlen == nextlen) {
0659             max_count = 6, min_count = 3;
0660         } else {
0661             max_count = 7, min_count = 4;
0662         }
0663     }
0664 }
0665 
0666 /* ===========================================================================
0667  * Construct the Huffman tree for the bit lengths and return the index in
0668  * bl_order of the last bit length code to send.
0669  */
0670 static int build_bl_tree(
0671     deflate_state *s
0672 )
0673 {
0674     int max_blindex;  /* index of last bit length code of non zero freq */
0675 
0676     /* Determine the bit length frequencies for literal and distance trees */
0677     scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
0678     scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
0679 
0680     /* Build the bit length tree: */
0681     build_tree(s, (tree_desc *)(&(s->bl_desc)));
0682     /* opt_len now includes the length of the tree representations, except
0683      * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
0684      */
0685 
0686     /* Determine the number of bit length codes to send. The pkzip format
0687      * requires that at least 4 bit length codes be sent. (appnote.txt says
0688      * 3 but the actual value used is 4.)
0689      */
0690     for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
0691         if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
0692     }
0693     /* Update opt_len to include the bit length tree and counts */
0694     s->opt_len += 3*(max_blindex+1) + 5+5+4;
0695     Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
0696             s->opt_len, s->static_len));
0697 
0698     return max_blindex;
0699 }
0700 
0701 /* ===========================================================================
0702  * Send the header for a block using dynamic Huffman trees: the counts, the
0703  * lengths of the bit length codes, the literal tree and the distance tree.
0704  * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
0705  */
0706 static void send_all_trees(
0707     deflate_state *s,
0708     int lcodes,  /* number of codes for each tree */
0709     int dcodes,  /* number of codes for each tree */
0710     int blcodes  /* number of codes for each tree */
0711 )
0712 {
0713     int rank;                    /* index in bl_order */
0714 
0715     Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
0716     Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
0717             "too many codes");
0718     Tracev((stderr, "\nbl counts: "));
0719     send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
0720     send_bits(s, dcodes-1,   5);
0721     send_bits(s, blcodes-4,  4); /* not -3 as stated in appnote.txt */
0722     for (rank = 0; rank < blcodes; rank++) {
0723         Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
0724         send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
0725     }
0726     Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
0727 
0728     send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
0729     Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
0730 
0731     send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
0732     Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
0733 }
0734 
0735 /* ===========================================================================
0736  * Send a stored block
0737  */
0738 void zlib_tr_stored_block(
0739     deflate_state *s,
0740     char *buf,        /* input block */
0741     ulg stored_len,   /* length of input block */
0742     int eof           /* true if this is the last block for a file */
0743 )
0744 {
0745     send_bits(s, (STORED_BLOCK<<1)+eof, 3);  /* send block type */
0746     s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
0747     s->compressed_len += (stored_len + 4) << 3;
0748 
0749     copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
0750 }
0751 
0752 /* Send just the `stored block' type code without any length bytes or data.
0753  */
0754 void zlib_tr_stored_type_only(
0755     deflate_state *s
0756 )
0757 {
0758     send_bits(s, (STORED_BLOCK << 1), 3);
0759     bi_windup(s);
0760     s->compressed_len = (s->compressed_len + 3) & ~7L;
0761 }
0762 
0763 
0764 /* ===========================================================================
0765  * Send one empty static block to give enough lookahead for inflate.
0766  * This takes 10 bits, of which 7 may remain in the bit buffer.
0767  * The current inflate code requires 9 bits of lookahead. If the
0768  * last two codes for the previous block (real code plus EOB) were coded
0769  * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode
0770  * the last real code. In this case we send two empty static blocks instead
0771  * of one. (There are no problems if the previous block is stored or fixed.)
0772  * To simplify the code, we assume the worst case of last real code encoded
0773  * on one bit only.
0774  */
0775 void zlib_tr_align(
0776     deflate_state *s
0777 )
0778 {
0779     send_bits(s, STATIC_TREES<<1, 3);
0780     send_code(s, END_BLOCK, static_ltree);
0781     s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
0782     bi_flush(s);
0783     /* Of the 10 bits for the empty block, we have already sent
0784      * (10 - bi_valid) bits. The lookahead for the last real code (before
0785      * the EOB of the previous block) was thus at least one plus the length
0786      * of the EOB plus what we have just sent of the empty static block.
0787      */
0788     if (1 + s->last_eob_len + 10 - s->bi_valid < 9) {
0789         send_bits(s, STATIC_TREES<<1, 3);
0790         send_code(s, END_BLOCK, static_ltree);
0791         s->compressed_len += 10L;
0792         bi_flush(s);
0793     }
0794     s->last_eob_len = 7;
0795 }
0796 
0797 /* ===========================================================================
0798  * Determine the best encoding for the current block: dynamic trees, static
0799  * trees or store, and output the encoded block to the zip file. This function
0800  * returns the total compressed length for the file so far.
0801  */
0802 ulg zlib_tr_flush_block(
0803     deflate_state *s,
0804     char *buf,        /* input block, or NULL if too old */
0805     ulg stored_len,   /* length of input block */
0806     int eof           /* true if this is the last block for a file */
0807 )
0808 {
0809     ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
0810     int max_blindex = 0;  /* index of last bit length code of non zero freq */
0811 
0812     /* Build the Huffman trees unless a stored block is forced */
0813     if (s->level > 0) {
0814 
0815      /* Check if the file is ascii or binary */
0816     if (s->data_type == Z_UNKNOWN) set_data_type(s);
0817 
0818     /* Construct the literal and distance trees */
0819     build_tree(s, (tree_desc *)(&(s->l_desc)));
0820     Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
0821         s->static_len));
0822 
0823     build_tree(s, (tree_desc *)(&(s->d_desc)));
0824     Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
0825         s->static_len));
0826     /* At this point, opt_len and static_len are the total bit lengths of
0827      * the compressed block data, excluding the tree representations.
0828      */
0829 
0830     /* Build the bit length tree for the above two trees, and get the index
0831      * in bl_order of the last bit length code to send.
0832      */
0833     max_blindex = build_bl_tree(s);
0834 
0835     /* Determine the best encoding. Compute first the block length in bytes*/
0836     opt_lenb = (s->opt_len+3+7)>>3;
0837     static_lenb = (s->static_len+3+7)>>3;
0838 
0839     Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
0840         opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
0841         s->last_lit));
0842 
0843     if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
0844 
0845     } else {
0846         Assert(buf != (char*)0, "lost buf");
0847     opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
0848     }
0849 
0850     /* If compression failed and this is the first and last block,
0851      * and if the .zip file can be seeked (to rewrite the local header),
0852      * the whole file is transformed into a stored file:
0853      */
0854 #ifdef STORED_FILE_OK
0855 #  ifdef FORCE_STORED_FILE
0856     if (eof && s->compressed_len == 0L) { /* force stored file */
0857 #  else
0858     if (stored_len <= opt_lenb && eof && s->compressed_len==0L && seekable()) {
0859 #  endif
0860         /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
0861         if (buf == (char*)0) error ("block vanished");
0862 
0863         copy_block(s, buf, (unsigned)stored_len, 0); /* without header */
0864         s->compressed_len = stored_len << 3;
0865         s->method = STORED;
0866     } else
0867 #endif /* STORED_FILE_OK */
0868 
0869 #ifdef FORCE_STORED
0870     if (buf != (char*)0) { /* force stored block */
0871 #else
0872     if (stored_len+4 <= opt_lenb && buf != (char*)0) {
0873                        /* 4: two words for the lengths */
0874 #endif
0875         /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
0876          * Otherwise we can't have processed more than WSIZE input bytes since
0877          * the last block flush, because compression would have been
0878          * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
0879          * transform a block into a stored block.
0880          */
0881         zlib_tr_stored_block(s, buf, stored_len, eof);
0882 
0883 #ifdef FORCE_STATIC
0884     } else if (static_lenb >= 0) { /* force static trees */
0885 #else
0886     } else if (static_lenb == opt_lenb) {
0887 #endif
0888         send_bits(s, (STATIC_TREES<<1)+eof, 3);
0889         compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
0890         s->compressed_len += 3 + s->static_len;
0891     } else {
0892         send_bits(s, (DYN_TREES<<1)+eof, 3);
0893         send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
0894                        max_blindex+1);
0895         compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
0896         s->compressed_len += 3 + s->opt_len;
0897     }
0898     Assert (s->compressed_len == s->bits_sent, "bad compressed size");
0899     init_block(s);
0900 
0901     if (eof) {
0902         bi_windup(s);
0903         s->compressed_len += 7;  /* align on byte boundary */
0904     }
0905     Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
0906            s->compressed_len-7*eof));
0907 
0908     return s->compressed_len >> 3;
0909 }
0910 
0911 /* ===========================================================================
0912  * Save the match info and tally the frequency counts. Return true if
0913  * the current block must be flushed.
0914  */
0915 int zlib_tr_tally(
0916     deflate_state *s,
0917     unsigned dist,  /* distance of matched string */
0918     unsigned lc     /* match length-MIN_MATCH or unmatched char (if dist==0) */
0919 )
0920 {
0921     s->d_buf[s->last_lit] = (ush)dist;
0922     s->l_buf[s->last_lit++] = (uch)lc;
0923     if (dist == 0) {
0924         /* lc is the unmatched char */
0925         s->dyn_ltree[lc].Freq++;
0926     } else {
0927         s->matches++;
0928         /* Here, lc is the match length - MIN_MATCH */
0929         dist--;             /* dist = match distance - 1 */
0930         Assert((ush)dist < (ush)MAX_DIST(s) &&
0931                (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
0932                (ush)d_code(dist) < (ush)D_CODES,  "zlib_tr_tally: bad match");
0933 
0934         s->dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
0935         s->dyn_dtree[d_code(dist)].Freq++;
0936     }
0937 
0938     /* Try to guess if it is profitable to stop the current block here */
0939     if ((s->last_lit & 0xfff) == 0 && s->level > 2) {
0940         /* Compute an upper bound for the compressed length */
0941         ulg out_length = (ulg)s->last_lit*8L;
0942         ulg in_length = (ulg)((long)s->strstart - s->block_start);
0943         int dcode;
0944         for (dcode = 0; dcode < D_CODES; dcode++) {
0945             out_length += (ulg)s->dyn_dtree[dcode].Freq *
0946                 (5L+extra_dbits[dcode]);
0947         }
0948         out_length >>= 3;
0949         Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
0950                s->last_lit, in_length, out_length,
0951                100L - out_length*100L/in_length));
0952         if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
0953     }
0954     return (s->last_lit == s->lit_bufsize-1);
0955     /* We avoid equality with lit_bufsize because of wraparound at 64K
0956      * on 16 bit machines and because stored blocks are restricted to
0957      * 64K-1 bytes.
0958      */
0959 }
0960 
0961 /* ===========================================================================
0962  * Send the block data compressed using the given Huffman trees
0963  */
0964 static void compress_block(
0965     deflate_state *s,
0966     ct_data *ltree, /* literal tree */
0967     ct_data *dtree  /* distance tree */
0968 )
0969 {
0970     unsigned dist;      /* distance of matched string */
0971     int lc;             /* match length or unmatched char (if dist == 0) */
0972     unsigned lx = 0;    /* running index in l_buf */
0973     unsigned code;      /* the code to send */
0974     int extra;          /* number of extra bits to send */
0975 
0976     if (s->last_lit != 0) do {
0977         dist = s->d_buf[lx];
0978         lc = s->l_buf[lx++];
0979         if (dist == 0) {
0980             send_code(s, lc, ltree); /* send a literal byte */
0981             Tracecv(isgraph(lc), (stderr," '%c' ", lc));
0982         } else {
0983             /* Here, lc is the match length - MIN_MATCH */
0984             code = length_code[lc];
0985             send_code(s, code+LITERALS+1, ltree); /* send the length code */
0986             extra = extra_lbits[code];
0987             if (extra != 0) {
0988                 lc -= base_length[code];
0989                 send_bits(s, lc, extra);       /* send the extra length bits */
0990             }
0991             dist--; /* dist is now the match distance - 1 */
0992             code = d_code(dist);
0993             Assert (code < D_CODES, "bad d_code");
0994 
0995             send_code(s, code, dtree);       /* send the distance code */
0996             extra = extra_dbits[code];
0997             if (extra != 0) {
0998                 dist -= base_dist[code];
0999                 send_bits(s, dist, extra);   /* send the extra distance bits */
1000             }
1001         } /* literal or match pair ? */
1002 
1003         /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
1004         Assert(s->pending < s->lit_bufsize + 2*lx, "pendingBuf overflow");
1005 
1006     } while (lx < s->last_lit);
1007 
1008     send_code(s, END_BLOCK, ltree);
1009     s->last_eob_len = ltree[END_BLOCK].Len;
1010 }
1011 
1012 /* ===========================================================================
1013  * Set the data type to ASCII or BINARY, using a crude approximation:
1014  * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
1015  * IN assertion: the fields freq of dyn_ltree are set and the total of all
1016  * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
1017  */
1018 static void set_data_type(
1019     deflate_state *s
1020 )
1021 {
1022     int n = 0;
1023     unsigned ascii_freq = 0;
1024     unsigned bin_freq = 0;
1025     while (n < 7)        bin_freq += s->dyn_ltree[n++].Freq;
1026     while (n < 128)    ascii_freq += s->dyn_ltree[n++].Freq;
1027     while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq;
1028     s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? Z_BINARY : Z_ASCII);
1029 }
1030 
1031 /* ===========================================================================
1032  * Copy a stored block, storing first the length and its
1033  * one's complement if requested.
1034  */
1035 static void copy_block(
1036     deflate_state *s,
1037     char    *buf,     /* the input data */
1038     unsigned len,     /* its length */
1039     int      header   /* true if block header must be written */
1040 )
1041 {
1042     bi_windup(s);        /* align on byte boundary */
1043     s->last_eob_len = 8; /* enough lookahead for inflate */
1044 
1045     if (header) {
1046         put_short(s, (ush)len);   
1047         put_short(s, (ush)~len);
1048 #ifdef DEBUG_ZLIB
1049         s->bits_sent += 2*16;
1050 #endif
1051     }
1052 #ifdef DEBUG_ZLIB
1053     s->bits_sent += (ulg)len<<3;
1054 #endif
1055     /* bundle up the put_byte(s, *buf++) calls */
1056     memcpy(&s->pending_buf[s->pending], buf, len);
1057     s->pending += len;
1058 }
1059