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trees.c
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00001 /* trees.c -- output deflated data using Huffman coding
00002  * Copyright (C) 1995-2002 Jean-loup Gailly
00003  * For conditions of distribution and use, see copyright notice in zlib.h 
00004  */
00005 
00006 /*
00007  *  ALGORITHM
00008  *
00009  *      The "deflation" process uses several Huffman trees. The more
00010  *      common source values are represented by shorter bit sequences.
00011  *
00012  *      Each code tree is stored in a compressed form which is itself
00013  * a Huffman encoding of the lengths of all the code strings (in
00014  * ascending order by source values).  The actual code strings are
00015  * reconstructed from the lengths in the inflate process, as described
00016  * in the deflate specification.
00017  *
00018  *  REFERENCES
00019  *
00020  *      Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
00021  *      Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
00022  *
00023  *      Storer, James A.
00024  *          Data Compression:  Methods and Theory, pp. 49-50.
00025  *          Computer Science Press, 1988.  ISBN 0-7167-8156-5.
00026  *
00027  *      Sedgewick, R.
00028  *          Algorithms, p290.
00029  *          Addison-Wesley, 1983. ISBN 0-201-06672-6.
00030  */
00031 
00032 /* @(#) $Id: trees.c,v 1.2 2002/12/03 18:50:27 mszeredi Exp $ */
00033 
00034 /* #define GEN_TREES_H */
00035 
00036 #include "deflate.h"
00037 
00038 #ifdef DEBUG
00039 #  include <ctype.h>
00040 #endif
00041 
00042 /* ===========================================================================
00043  * Constants
00044  */
00045 
00046 #define MAX_BL_BITS 7
00047 /* Bit length codes must not exceed MAX_BL_BITS bits */
00048 
00049 #define END_BLOCK 256
00050 /* end of block literal code */
00051 
00052 #define REP_3_6      16
00053 /* repeat previous bit length 3-6 times (2 bits of repeat count) */
00054 
00055 #define REPZ_3_10    17
00056 /* repeat a zero length 3-10 times  (3 bits of repeat count) */
00057 
00058 #define REPZ_11_138  18
00059 /* repeat a zero length 11-138 times  (7 bits of repeat count) */
00060 
00061 local const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */
00062    = {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};
00063 
00064 local const int extra_dbits[D_CODES] /* extra bits for each distance code */
00065    = {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};
00066 
00067 local const int extra_blbits[BL_CODES]/* extra bits for each bit length code */
00068    = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
00069 
00070 local const uch bl_order[BL_CODES]
00071    = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
00072 /* The lengths of the bit length codes are sent in order of decreasing
00073  * probability, to avoid transmitting the lengths for unused bit length codes.
00074  */
00075 
00076 #define Buf_size (8 * 2*sizeof(char))
00077 /* Number of bits used within bi_buf. (bi_buf might be implemented on
00078  * more than 16 bits on some systems.)
00079  */
00080 
00081 /* ===========================================================================
00082  * Local data. These are initialized only once.
00083  */
00084 
00085 #define DIST_CODE_LEN  512 /* see definition of array dist_code below */
00086 
00087 #if defined(GEN_TREES_H) || !defined(STDC)
00088 /* non ANSI compilers may not accept trees.h */
00089 
00090 local ct_data static_ltree[L_CODES+2];
00091 /* The static literal tree. Since the bit lengths are imposed, there is no
00092  * need for the L_CODES extra codes used during heap construction. However
00093  * The codes 286 and 287 are needed to build a canonical tree (see _tr_init
00094  * below).
00095  */
00096 
00097 local ct_data static_dtree[D_CODES];
00098 /* The static distance tree. (Actually a trivial tree since all codes use
00099  * 5 bits.)
00100  */
00101 
00102 uch _dist_code[DIST_CODE_LEN];
00103 /* Distance codes. The first 256 values correspond to the distances
00104  * 3 .. 258, the last 256 values correspond to the top 8 bits of
00105  * the 15 bit distances.
00106  */
00107 
00108 uch _length_code[MAX_MATCH-MIN_MATCH+1];
00109 /* length code for each normalized match length (0 == MIN_MATCH) */
00110 
00111 local int base_length[LENGTH_CODES];
00112 /* First normalized length for each code (0 = MIN_MATCH) */
00113 
00114 local int base_dist[D_CODES];
00115 /* First normalized distance for each code (0 = distance of 1) */
00116 
00117 #else
00118 #  include "trees.h"
00119 #endif /* GEN_TREES_H */
00120 
00121 struct static_tree_desc_s {
00122     const ct_data *static_tree;  /* static tree or NULL */
00123     const intf *extra_bits;      /* extra bits for each code or NULL */
00124     int     extra_base;          /* base index for extra_bits */
00125     int     elems;               /* max number of elements in the tree */
00126     int     max_length;          /* max bit length for the codes */
00127 };
00128 
00129 local static_tree_desc  static_l_desc =
00130 {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
00131 
00132 local static_tree_desc  static_d_desc =
00133 {static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};
00134 
00135 local static_tree_desc  static_bl_desc =
00136 {(const ct_data *)0, extra_blbits, 0,   BL_CODES, MAX_BL_BITS};
00137 
00138 /* ===========================================================================
00139  * Local (static) routines in this file.
00140  */
00141 
00142 local void tr_static_init OF((void));
00143 local void init_block     OF((deflate_state *s));
00144 local void pqdownheap     OF((deflate_state *s, ct_data *tree, int k));
00145 local void gen_bitlen     OF((deflate_state *s, tree_desc *desc));
00146 local void gen_codes      OF((ct_data *tree, int max_code, ushf *bl_count));
00147 local void build_tree     OF((deflate_state *s, tree_desc *desc));
00148 local void scan_tree      OF((deflate_state *s, ct_data *tree, int max_code));
00149 local void send_tree      OF((deflate_state *s, ct_data *tree, int max_code));
00150 local int  build_bl_tree  OF((deflate_state *s));
00151 local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes,
00152                               int blcodes));
00153 local void compress_block OF((deflate_state *s, ct_data *ltree,
00154                               ct_data *dtree));
00155 local void set_data_type  OF((deflate_state *s));
00156 local unsigned bi_reverse OF((unsigned value, int length));
00157 local void bi_windup      OF((deflate_state *s));
00158 local void bi_flush       OF((deflate_state *s));
00159 local void copy_block     OF((deflate_state *s, charf *buf, unsigned len,
00160                               int header));
00161 
00162 #ifdef GEN_TREES_H
00163 local void gen_trees_header OF((void));
00164 #endif
00165 
00166 #ifndef DEBUG
00167 #  define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
00168    /* Send a code of the given tree. c and tree must not have side effects */
00169 
00170 #else /* DEBUG */
00171 #  define send_code(s, c, tree) \
00172      { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
00173        send_bits(s, tree[c].Code, tree[c].Len); }
00174 #endif
00175 
00176 /* ===========================================================================
00177  * Output a short LSB first on the stream.
00178  * IN assertion: there is enough room in pendingBuf.
00179  */
00180 #define put_short(s, w) { \
00181     put_byte(s, (uch)((w) & 0xff)); \
00182     put_byte(s, (uch)((ush)(w) >> 8)); \
00183 }
00184 
00185 /* ===========================================================================
00186  * Send a value on a given number of bits.
00187  * IN assertion: length <= 16 and value fits in length bits.
00188  */
00189 #ifdef DEBUG
00190 local void send_bits      OF((deflate_state *s, int value, int length));
00191 
00192 local void send_bits(s, value, length)
00193     deflate_state *s;
00194     int value;  /* value to send */
00195     int length; /* number of bits */
00196 {
00197     Tracevv((stderr," l %2d v %4x ", length, value));
00198     Assert(length > 0 && length <= 15, "invalid length");
00199     s->bits_sent += (ulg)length;
00200 
00201     /* If not enough room in bi_buf, use (valid) bits from bi_buf and
00202      * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
00203      * unused bits in value.
00204      */
00205     if (s->bi_valid > (int)Buf_size - length) {
00206         s->bi_buf |= (value << s->bi_valid);
00207         put_short(s, s->bi_buf);
00208         s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
00209         s->bi_valid += length - Buf_size;
00210     } else {
00211         s->bi_buf |= value << s->bi_valid;
00212         s->bi_valid += length;
00213     }
00214 }
00215 #else /* !DEBUG */
00216 
00217 #define send_bits(s, value, length) \
00218 { int len = length;\
00219   if (s->bi_valid > (int)Buf_size - len) {\
00220     int val = value;\
00221     s->bi_buf |= (val << s->bi_valid);\
00222     put_short(s, s->bi_buf);\
00223     s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
00224     s->bi_valid += len - Buf_size;\
00225   } else {\
00226     s->bi_buf |= (value) << s->bi_valid;\
00227     s->bi_valid += len;\
00228   }\
00229 }
00230 #endif /* DEBUG */
00231 
00232 
00233 #define MAX(a,b) (a >= b ? a : b)
00234 /* the arguments must not have side effects */
00235 
00236 /* ===========================================================================
00237  * Initialize the various 'constant' tables.
00238  */
00239 local void tr_static_init()
00240 {
00241 #if defined(GEN_TREES_H) || !defined(STDC)
00242     static int static_init_done = 0;
00243     int n;        /* iterates over tree elements */
00244     int bits;     /* bit counter */
00245     int length;   /* length value */
00246     int code;     /* code value */
00247     int dist;     /* distance index */
00248     ush bl_count[MAX_BITS+1];
00249     /* number of codes at each bit length for an optimal tree */
00250 
00251     if (static_init_done) return;
00252 
00253     /* For some embedded targets, global variables are not initialized: */
00254     static_l_desc.static_tree = static_ltree;
00255     static_l_desc.extra_bits = extra_lbits;
00256     static_d_desc.static_tree = static_dtree;
00257     static_d_desc.extra_bits = extra_dbits;
00258     static_bl_desc.extra_bits = extra_blbits;
00259 
00260     /* Initialize the mapping length (0..255) -> length code (0..28) */
00261     length = 0;
00262     for (code = 0; code < LENGTH_CODES-1; code++) {
00263         base_length[code] = length;
00264         for (n = 0; n < (1<<extra_lbits[code]); n++) {
00265             _length_code[length++] = (uch)code;
00266         }
00267     }
00268     Assert (length == 256, "tr_static_init: length != 256");
00269     /* Note that the length 255 (match length 258) can be represented
00270      * in two different ways: code 284 + 5 bits or code 285, so we
00271      * overwrite length_code[255] to use the best encoding:
00272      */
00273     _length_code[length-1] = (uch)code;
00274 
00275     /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
00276     dist = 0;
00277     for (code = 0 ; code < 16; code++) {
00278         base_dist[code] = dist;
00279         for (n = 0; n < (1<<extra_dbits[code]); n++) {
00280             _dist_code[dist++] = (uch)code;
00281         }
00282     }
00283     Assert (dist == 256, "tr_static_init: dist != 256");
00284     dist >>= 7; /* from now on, all distances are divided by 128 */
00285     for ( ; code < D_CODES; code++) {
00286         base_dist[code] = dist << 7;
00287         for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
00288             _dist_code[256 + dist++] = (uch)code;
00289         }
00290     }
00291     Assert (dist == 256, "tr_static_init: 256+dist != 512");
00292 
00293     /* Construct the codes of the static literal tree */
00294     for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
00295     n = 0;
00296     while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
00297     while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
00298     while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
00299     while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
00300     /* Codes 286 and 287 do not exist, but we must include them in the
00301      * tree construction to get a canonical Huffman tree (longest code
00302      * all ones)
00303      */
00304     gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
00305 
00306     /* The static distance tree is trivial: */
00307     for (n = 0; n < D_CODES; n++) {
00308         static_dtree[n].Len = 5;
00309         static_dtree[n].Code = bi_reverse((unsigned)n, 5);
00310     }
00311     static_init_done = 1;
00312 
00313 #  ifdef GEN_TREES_H
00314     gen_trees_header();
00315 #  endif
00316 #endif /* defined(GEN_TREES_H) || !defined(STDC) */
00317 }
00318 
00319 /* ===========================================================================
00320  * Genererate the file trees.h describing the static trees.
00321  */
00322 #ifdef GEN_TREES_H
00323 #  ifndef DEBUG
00324 #    include <stdio.h>
00325 #  endif
00326 
00327 #  define SEPARATOR(i, last, width) \
00328       ((i) == (last)? "\n};\n\n" :    \
00329        ((i) % (width) == (width)-1 ? ",\n" : ", "))
00330 
00331 void gen_trees_header()
00332 {
00333     FILE *header = fopen("trees.h", "w");
00334     int i;
00335 
00336     Assert (header != NULL, "Can't open trees.h");
00337     fprintf(header,
00338            "/* header created automatically with -DGEN_TREES_H */\n\n");
00339 
00340     fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n");
00341     for (i = 0; i < L_CODES+2; i++) {
00342        fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code,
00343               static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5));
00344     }
00345 
00346     fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n");
00347     for (i = 0; i < D_CODES; i++) {
00348        fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code,
00349               static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5));
00350     }
00351 
00352     fprintf(header, "const uch _dist_code[DIST_CODE_LEN] = {\n");
00353     for (i = 0; i < DIST_CODE_LEN; i++) {
00354        fprintf(header, "%2u%s", _dist_code[i],
00355               SEPARATOR(i, DIST_CODE_LEN-1, 20));
00356     }
00357 
00358     fprintf(header, "const uch _length_code[MAX_MATCH-MIN_MATCH+1]= {\n");
00359     for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) {
00360        fprintf(header, "%2u%s", _length_code[i],
00361               SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20));
00362     }
00363 
00364     fprintf(header, "local const int base_length[LENGTH_CODES] = {\n");
00365     for (i = 0; i < LENGTH_CODES; i++) {
00366        fprintf(header, "%1u%s", base_length[i],
00367               SEPARATOR(i, LENGTH_CODES-1, 20));
00368     }
00369 
00370     fprintf(header, "local const int base_dist[D_CODES] = {\n");
00371     for (i = 0; i < D_CODES; i++) {
00372        fprintf(header, "%5u%s", base_dist[i],
00373               SEPARATOR(i, D_CODES-1, 10));
00374     }
00375 
00376     fclose(header);
00377 }
00378 #endif /* GEN_TREES_H */
00379 
00380 /* ===========================================================================
00381  * Initialize the tree data structures for a new zlib stream.
00382  */
00383 void _tr_init(s)
00384     deflate_state *s;
00385 {
00386     tr_static_init();
00387 
00388     s->l_desc.dyn_tree = s->dyn_ltree;
00389     s->l_desc.stat_desc = &static_l_desc;
00390 
00391     s->d_desc.dyn_tree = s->dyn_dtree;
00392     s->d_desc.stat_desc = &static_d_desc;
00393 
00394     s->bl_desc.dyn_tree = s->bl_tree;
00395     s->bl_desc.stat_desc = &static_bl_desc;
00396 
00397     s->bi_buf = 0;
00398     s->bi_valid = 0;
00399     s->last_eob_len = 8; /* enough lookahead for inflate */
00400 #ifdef DEBUG
00401     s->compressed_len = 0L;
00402     s->bits_sent = 0L;
00403 #endif
00404 
00405     /* Initialize the first block of the first file: */
00406     init_block(s);
00407 }
00408 
00409 /* ===========================================================================
00410  * Initialize a new block.
00411  */
00412 local void init_block(s)
00413     deflate_state *s;
00414 {
00415     int n; /* iterates over tree elements */
00416 
00417     /* Initialize the trees. */
00418     for (n = 0; n < L_CODES;  n++) s->dyn_ltree[n].Freq = 0;
00419     for (n = 0; n < D_CODES;  n++) s->dyn_dtree[n].Freq = 0;
00420     for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
00421 
00422     s->dyn_ltree[END_BLOCK].Freq = 1;
00423     s->opt_len = s->static_len = 0L;
00424     s->last_lit = s->matches = 0;
00425 }
00426 
00427 #define SMALLEST 1
00428 /* Index within the heap array of least frequent node in the Huffman tree */
00429 
00430 
00431 /* ===========================================================================
00432  * Remove the smallest element from the heap and recreate the heap with
00433  * one less element. Updates heap and heap_len.
00434  */
00435 #define pqremove(s, tree, top) \
00436 {\
00437     top = s->heap[SMALLEST]; \
00438     s->heap[SMALLEST] = s->heap[s->heap_len--]; \
00439     pqdownheap(s, tree, SMALLEST); \
00440 }
00441 
00442 /* ===========================================================================
00443  * Compares to subtrees, using the tree depth as tie breaker when
00444  * the subtrees have equal frequency. This minimizes the worst case length.
00445  */
00446 #define smaller(tree, n, m, depth) \
00447    (tree[n].Freq < tree[m].Freq || \
00448    (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
00449 
00450 /* ===========================================================================
00451  * Restore the heap property by moving down the tree starting at node k,
00452  * exchanging a node with the smallest of its two sons if necessary, stopping
00453  * when the heap property is re-established (each father smaller than its
00454  * two sons).
00455  */
00456 local void pqdownheap(s, tree, k)
00457     deflate_state *s;
00458     ct_data *tree;  /* the tree to restore */
00459     int k;               /* node to move down */
00460 {
00461     int v = s->heap[k];
00462     int j = k << 1;  /* left son of k */
00463     while (j <= s->heap_len) {
00464         /* Set j to the smallest of the two sons: */
00465         if (j < s->heap_len &&
00466             smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
00467             j++;
00468         }
00469         /* Exit if v is smaller than both sons */
00470         if (smaller(tree, v, s->heap[j], s->depth)) break;
00471 
00472         /* Exchange v with the smallest son */
00473         s->heap[k] = s->heap[j];  k = j;
00474 
00475         /* And continue down the tree, setting j to the left son of k */
00476         j <<= 1;
00477     }
00478     s->heap[k] = v;
00479 }
00480 
00481 /* ===========================================================================
00482  * Compute the optimal bit lengths for a tree and update the total bit length
00483  * for the current block.
00484  * IN assertion: the fields freq and dad are set, heap[heap_max] and
00485  *    above are the tree nodes sorted by increasing frequency.
00486  * OUT assertions: the field len is set to the optimal bit length, the
00487  *     array bl_count contains the frequencies for each bit length.
00488  *     The length opt_len is updated; static_len is also updated if stree is
00489  *     not null.
00490  */
00491 local void gen_bitlen(s, desc)
00492     deflate_state *s;
00493     tree_desc *desc;    /* the tree descriptor */
00494 {
00495     ct_data *tree        = desc->dyn_tree;
00496     int max_code         = desc->max_code;
00497     const ct_data *stree = desc->stat_desc->static_tree;
00498     const intf *extra    = desc->stat_desc->extra_bits;
00499     int base             = desc->stat_desc->extra_base;
00500     int max_length       = desc->stat_desc->max_length;
00501     int h;              /* heap index */
00502     int n, m;           /* iterate over the tree elements */
00503     int bits;           /* bit length */
00504     int xbits;          /* extra bits */
00505     ush f;              /* frequency */
00506     int overflow = 0;   /* number of elements with bit length too large */
00507 
00508     for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
00509 
00510     /* In a first pass, compute the optimal bit lengths (which may
00511      * overflow in the case of the bit length tree).
00512      */
00513     tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
00514 
00515     for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
00516         n = s->heap[h];
00517         bits = tree[tree[n].Dad].Len + 1;
00518         if (bits > max_length) bits = max_length, overflow++;
00519         tree[n].Len = (ush)bits;
00520         /* We overwrite tree[n].Dad which is no longer needed */
00521 
00522         if (n > max_code) continue; /* not a leaf node */
00523 
00524         s->bl_count[bits]++;
00525         xbits = 0;
00526         if (n >= base) xbits = extra[n-base];
00527         f = tree[n].Freq;
00528         s->opt_len += (ulg)f * (bits + xbits);
00529         if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
00530     }
00531     if (overflow == 0) return;
00532 
00533     Trace((stderr,"\nbit length overflow\n"));
00534     /* This happens for example on obj2 and pic of the Calgary corpus */
00535 
00536     /* Find the first bit length which could increase: */
00537     do {
00538         bits = max_length-1;
00539         while (s->bl_count[bits] == 0) bits--;
00540         s->bl_count[bits]--;      /* move one leaf down the tree */
00541         s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
00542         s->bl_count[max_length]--;
00543         /* The brother of the overflow item also moves one step up,
00544          * but this does not affect bl_count[max_length]
00545          */
00546         overflow -= 2;
00547     } while (overflow > 0);
00548 
00549     /* Now recompute all bit lengths, scanning in increasing frequency.
00550      * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
00551      * lengths instead of fixing only the wrong ones. This idea is taken
00552      * from 'ar' written by Haruhiko Okumura.)
00553      */
00554     for (bits = max_length; bits != 0; bits--) {
00555         n = s->bl_count[bits];
00556         while (n != 0) {
00557             m = s->heap[--h];
00558             if (m > max_code) continue;
00559             if (tree[m].Len != (unsigned) bits) {
00560                 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
00561                 s->opt_len += ((long)bits - (long)tree[m].Len)
00562                               *(long)tree[m].Freq;
00563                 tree[m].Len = (ush)bits;
00564             }
00565             n--;
00566         }
00567     }
00568 }
00569 
00570 /* ===========================================================================
00571  * Generate the codes for a given tree and bit counts (which need not be
00572  * optimal).
00573  * IN assertion: the array bl_count contains the bit length statistics for
00574  * the given tree and the field len is set for all tree elements.
00575  * OUT assertion: the field code is set for all tree elements of non
00576  *     zero code length.
00577  */
00578 local void gen_codes (tree, max_code, bl_count)
00579     ct_data *tree;             /* the tree to decorate */
00580     int max_code;              /* largest code with non zero frequency */
00581     ushf *bl_count;            /* number of codes at each bit length */
00582 {
00583     ush next_code[MAX_BITS+1]; /* next code value for each bit length */
00584     ush code = 0;              /* running code value */
00585     int bits;                  /* bit index */
00586     int n;                     /* code index */
00587 
00588     /* The distribution counts are first used to generate the code values
00589      * without bit reversal.
00590      */
00591     for (bits = 1; bits <= MAX_BITS; bits++) {
00592         next_code[bits] = code = (code + bl_count[bits-1]) << 1;
00593     }
00594     /* Check that the bit counts in bl_count are consistent. The last code
00595      * must be all ones.
00596      */
00597     Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
00598             "inconsistent bit counts");
00599     Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
00600 
00601     for (n = 0;  n <= max_code; n++) {
00602         int len = tree[n].Len;
00603         if (len == 0) continue;
00604         /* Now reverse the bits */
00605         tree[n].Code = bi_reverse(next_code[len]++, len);
00606 
00607         Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
00608              n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
00609     }
00610 }
00611 
00612 /* ===========================================================================
00613  * Construct one Huffman tree and assigns the code bit strings and lengths.
00614  * Update the total bit length for the current block.
00615  * IN assertion: the field freq is set for all tree elements.
00616  * OUT assertions: the fields len and code are set to the optimal bit length
00617  *     and corresponding code. The length opt_len is updated; static_len is
00618  *     also updated if stree is not null. The field max_code is set.
00619  */
00620 local void build_tree(s, desc)
00621     deflate_state *s;
00622     tree_desc *desc; /* the tree descriptor */
00623 {
00624     ct_data *tree         = desc->dyn_tree;
00625     const ct_data *stree  = desc->stat_desc->static_tree;
00626     int elems             = desc->stat_desc->elems;
00627     int n, m;          /* iterate over heap elements */
00628     int max_code = -1; /* largest code with non zero frequency */
00629     int node;          /* new node being created */
00630 
00631     /* Construct the initial heap, with least frequent element in
00632      * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
00633      * heap[0] is not used.
00634      */
00635     s->heap_len = 0, s->heap_max = HEAP_SIZE;
00636 
00637     for (n = 0; n < elems; n++) {
00638         if (tree[n].Freq != 0) {
00639             s->heap[++(s->heap_len)] = max_code = n;
00640             s->depth[n] = 0;
00641         } else {
00642             tree[n].Len = 0;
00643         }
00644     }
00645 
00646     /* The pkzip format requires that at least one distance code exists,
00647      * and that at least one bit should be sent even if there is only one
00648      * possible code. So to avoid special checks later on we force at least
00649      * two codes of non zero frequency.
00650      */
00651     while (s->heap_len < 2) {
00652         node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
00653         tree[node].Freq = 1;
00654         s->depth[node] = 0;
00655         s->opt_len--; if (stree) s->static_len -= stree[node].Len;
00656         /* node is 0 or 1 so it does not have extra bits */
00657     }
00658     desc->max_code = max_code;
00659 
00660     /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
00661      * establish sub-heaps of increasing lengths:
00662      */
00663     for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
00664 
00665     /* Construct the Huffman tree by repeatedly combining the least two
00666      * frequent nodes.
00667      */
00668     node = elems;              /* next internal node of the tree */
00669     do {
00670         pqremove(s, tree, n);  /* n = node of least frequency */
00671         m = s->heap[SMALLEST]; /* m = node of next least frequency */
00672 
00673         s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
00674         s->heap[--(s->heap_max)] = m;
00675 
00676         /* Create a new node father of n and m */
00677         tree[node].Freq = tree[n].Freq + tree[m].Freq;
00678         s->depth[node] = (uch) (MAX(s->depth[n], s->depth[m]) + 1);
00679         tree[n].Dad = tree[m].Dad = (ush)node;
00680 #ifdef DUMP_BL_TREE
00681         if (tree == s->bl_tree) {
00682             fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
00683                     node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
00684         }
00685 #endif
00686         /* and insert the new node in the heap */
00687         s->heap[SMALLEST] = node++;
00688         pqdownheap(s, tree, SMALLEST);
00689 
00690     } while (s->heap_len >= 2);
00691 
00692     s->heap[--(s->heap_max)] = s->heap[SMALLEST];
00693 
00694     /* At this point, the fields freq and dad are set. We can now
00695      * generate the bit lengths.
00696      */
00697     gen_bitlen(s, (tree_desc *)desc);
00698 
00699     /* The field len is now set, we can generate the bit codes */
00700     gen_codes ((ct_data *)tree, max_code, s->bl_count);
00701 }
00702 
00703 /* ===========================================================================
00704  * Scan a literal or distance tree to determine the frequencies of the codes
00705  * in the bit length tree.
00706  */
00707 local void scan_tree (s, tree, max_code)
00708     deflate_state *s;
00709     ct_data *tree;   /* the tree to be scanned */
00710     int max_code;    /* and its largest code of non zero frequency */
00711 {
00712     int n;                     /* iterates over all tree elements */
00713     int prevlen = -1;          /* last emitted length */
00714     int curlen;                /* length of current code */
00715     int nextlen = tree[0].Len; /* length of next code */
00716     int count = 0;             /* repeat count of the current code */
00717     int max_count = 7;         /* max repeat count */
00718     int min_count = 4;         /* min repeat count */
00719 
00720     if (nextlen == 0) max_count = 138, min_count = 3;
00721     tree[max_code+1].Len = (ush)0xffff; /* guard */
00722 
00723     for (n = 0; n <= max_code; n++) {
00724         curlen = nextlen; nextlen = tree[n+1].Len;
00725         if (++count < max_count && curlen == nextlen) {
00726             continue;
00727         } else if (count < min_count) {
00728             s->bl_tree[curlen].Freq += count;
00729         } else if (curlen != 0) {
00730             if (curlen != prevlen) s->bl_tree[curlen].Freq++;
00731             s->bl_tree[REP_3_6].Freq++;
00732         } else if (count <= 10) {
00733             s->bl_tree[REPZ_3_10].Freq++;
00734         } else {
00735             s->bl_tree[REPZ_11_138].Freq++;
00736         }
00737         count = 0; prevlen = curlen;
00738         if (nextlen == 0) {
00739             max_count = 138, min_count = 3;
00740         } else if (curlen == nextlen) {
00741             max_count = 6, min_count = 3;
00742         } else {
00743             max_count = 7, min_count = 4;
00744         }
00745     }
00746 }
00747 
00748 /* ===========================================================================
00749  * Send a literal or distance tree in compressed form, using the codes in
00750  * bl_tree.
00751  */
00752 local void send_tree (s, tree, max_code)
00753     deflate_state *s;
00754     ct_data *tree; /* the tree to be scanned */
00755     int max_code;       /* and its largest code of non zero frequency */
00756 {
00757     int n;                     /* iterates over all tree elements */
00758     int prevlen = -1;          /* last emitted length */
00759     int curlen;                /* length of current code */
00760     int nextlen = tree[0].Len; /* length of next code */
00761     int count = 0;             /* repeat count of the current code */
00762     int max_count = 7;         /* max repeat count */
00763     int min_count = 4;         /* min repeat count */
00764 
00765     /* tree[max_code+1].Len = -1; */  /* guard already set */
00766     if (nextlen == 0) max_count = 138, min_count = 3;
00767 
00768     for (n = 0; n <= max_code; n++) {
00769         curlen = nextlen; nextlen = tree[n+1].Len;
00770         if (++count < max_count && curlen == nextlen) {
00771             continue;
00772         } else if (count < min_count) {
00773             do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
00774 
00775         } else if (curlen != 0) {
00776             if (curlen != prevlen) {
00777                 send_code(s, curlen, s->bl_tree); count--;
00778             }
00779             Assert(count >= 3 && count <= 6, " 3_6?");
00780             send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
00781 
00782         } else if (count <= 10) {
00783             send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
00784 
00785         } else {
00786             send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
00787         }
00788         count = 0; prevlen = curlen;
00789         if (nextlen == 0) {
00790             max_count = 138, min_count = 3;
00791         } else if (curlen == nextlen) {
00792             max_count = 6, min_count = 3;
00793         } else {
00794             max_count = 7, min_count = 4;
00795         }
00796     }
00797 }
00798 
00799 /* ===========================================================================
00800  * Construct the Huffman tree for the bit lengths and return the index in
00801  * bl_order of the last bit length code to send.
00802  */
00803 local int build_bl_tree(s)
00804     deflate_state *s;
00805 {
00806     int max_blindex;  /* index of last bit length code of non zero freq */
00807 
00808     /* Determine the bit length frequencies for literal and distance trees */
00809     scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
00810     scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
00811 
00812     /* Build the bit length tree: */
00813     build_tree(s, (tree_desc *)(&(s->bl_desc)));
00814     /* opt_len now includes the length of the tree representations, except
00815      * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
00816      */
00817 
00818     /* Determine the number of bit length codes to send. The pkzip format
00819      * requires that at least 4 bit length codes be sent. (appnote.txt says
00820      * 3 but the actual value used is 4.)
00821      */
00822     for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
00823         if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
00824     }
00825     /* Update opt_len to include the bit length tree and counts */
00826     s->opt_len += 3*(max_blindex+1) + 5+5+4;
00827     Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
00828             s->opt_len, s->static_len));
00829 
00830     return max_blindex;
00831 }
00832 
00833 /* ===========================================================================
00834  * Send the header for a block using dynamic Huffman trees: the counts, the
00835  * lengths of the bit length codes, the literal tree and the distance tree.
00836  * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
00837  */
00838 local void send_all_trees(s, lcodes, dcodes, blcodes)
00839     deflate_state *s;
00840     int lcodes, dcodes, blcodes; /* number of codes for each tree */
00841 {
00842     int rank;                    /* index in bl_order */
00843 
00844     Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
00845     Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
00846             "too many codes");
00847     Tracev((stderr, "\nbl counts: "));
00848     send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
00849     send_bits(s, dcodes-1,   5);
00850     send_bits(s, blcodes-4,  4); /* not -3 as stated in appnote.txt */
00851     for (rank = 0; rank < blcodes; rank++) {
00852         Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
00853         send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
00854     }
00855     Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
00856 
00857     send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
00858     Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
00859 
00860     send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
00861     Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
00862 }
00863 
00864 /* ===========================================================================
00865  * Send a stored block
00866  */
00867 void _tr_stored_block(s, buf, stored_len, eof)
00868     deflate_state *s;
00869     charf *buf;       /* input block */
00870     ulg stored_len;   /* length of input block */
00871     int eof;          /* true if this is the last block for a file */
00872 {
00873     send_bits(s, (STORED_BLOCK<<1)+eof, 3);  /* send block type */
00874 #ifdef DEBUG
00875     s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
00876     s->compressed_len += (stored_len + 4) << 3;
00877 #endif
00878     copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
00879 }
00880 
00881 /* ===========================================================================
00882  * Send one empty static block to give enough lookahead for inflate.
00883  * This takes 10 bits, of which 7 may remain in the bit buffer.
00884  * The current inflate code requires 9 bits of lookahead. If the
00885  * last two codes for the previous block (real code plus EOB) were coded
00886  * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode
00887  * the last real code. In this case we send two empty static blocks instead
00888  * of one. (There are no problems if the previous block is stored or fixed.)
00889  * To simplify the code, we assume the worst case of last real code encoded
00890  * on one bit only.
00891  */
00892 void _tr_align(s)
00893     deflate_state *s;
00894 {
00895     send_bits(s, STATIC_TREES<<1, 3);
00896     send_code(s, END_BLOCK, static_ltree);
00897 #ifdef DEBUG
00898     s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
00899 #endif
00900     bi_flush(s);
00901     /* Of the 10 bits for the empty block, we have already sent
00902      * (10 - bi_valid) bits. The lookahead for the last real code (before
00903      * the EOB of the previous block) was thus at least one plus the length
00904      * of the EOB plus what we have just sent of the empty static block.
00905      */
00906     if (1 + s->last_eob_len + 10 - s->bi_valid < 9) {
00907         send_bits(s, STATIC_TREES<<1, 3);
00908         send_code(s, END_BLOCK, static_ltree);
00909 #ifdef DEBUG
00910         s->compressed_len += 10L;
00911 #endif
00912         bi_flush(s);
00913     }
00914     s->last_eob_len = 7;
00915 }
00916 
00917 /* ===========================================================================
00918  * Determine the best encoding for the current block: dynamic trees, static
00919  * trees or store, and output the encoded block to the zip file.
00920  */
00921 void _tr_flush_block(s, buf, stored_len, eof)
00922     deflate_state *s;
00923     charf *buf;       /* input block, or NULL if too old */
00924     ulg stored_len;   /* length of input block */
00925     int eof;          /* true if this is the last block for a file */
00926 {
00927     ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
00928     int max_blindex = 0;  /* index of last bit length code of non zero freq */
00929 
00930     /* Build the Huffman trees unless a stored block is forced */
00931     if (s->level > 0) {
00932 
00933         /* Check if the file is ascii or binary */
00934        if (s->data_type == Z_UNKNOWN) set_data_type(s);
00935 
00936        /* Construct the literal and distance trees */
00937        build_tree(s, (tree_desc *)(&(s->l_desc)));
00938        Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
00939               s->static_len));
00940 
00941        build_tree(s, (tree_desc *)(&(s->d_desc)));
00942        Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
00943               s->static_len));
00944        /* At this point, opt_len and static_len are the total bit lengths of
00945         * the compressed block data, excluding the tree representations.
00946         */
00947 
00948        /* Build the bit length tree for the above two trees, and get the index
00949         * in bl_order of the last bit length code to send.
00950         */
00951        max_blindex = build_bl_tree(s);
00952 
00953        /* Determine the best encoding. Compute first the block length in bytes*/
00954        opt_lenb = (s->opt_len+3+7)>>3;
00955        static_lenb = (s->static_len+3+7)>>3;
00956 
00957        Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
00958               opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
00959               s->last_lit));
00960 
00961        if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
00962 
00963     } else {
00964         Assert(buf != (char*)0, "lost buf");
00965        opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
00966     }
00967 
00968 #ifdef FORCE_STORED
00969     if (buf != (char*)0) { /* force stored block */
00970 #else
00971     if (stored_len+4 <= opt_lenb && buf != (char*)0) {
00972                        /* 4: two words for the lengths */
00973 #endif
00974         /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
00975          * Otherwise we can't have processed more than WSIZE input bytes since
00976          * the last block flush, because compression would have been
00977          * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
00978          * transform a block into a stored block.
00979          */
00980         _tr_stored_block(s, buf, stored_len, eof);
00981 
00982 #ifdef FORCE_STATIC
00983     } else if (static_lenb >= 0) { /* force static trees */
00984 #else
00985     } else if (static_lenb == opt_lenb) {
00986 #endif
00987         send_bits(s, (STATIC_TREES<<1)+eof, 3);
00988         compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
00989 #ifdef DEBUG
00990         s->compressed_len += 3 + s->static_len;
00991 #endif
00992     } else {
00993         send_bits(s, (DYN_TREES<<1)+eof, 3);
00994         send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
00995                        max_blindex+1);
00996         compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
00997 #ifdef DEBUG
00998         s->compressed_len += 3 + s->opt_len;
00999 #endif
01000     }
01001     Assert (s->compressed_len == s->bits_sent, "bad compressed size");
01002     /* The above check is made mod 2^32, for files larger than 512 MB
01003      * and uLong implemented on 32 bits.
01004      */
01005     init_block(s);
01006 
01007     if (eof) {
01008         bi_windup(s);
01009 #ifdef DEBUG
01010         s->compressed_len += 7;  /* align on byte boundary */
01011 #endif
01012     }
01013     Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
01014            s->compressed_len-7*eof));
01015 }
01016 
01017 /* ===========================================================================
01018  * Save the match info and tally the frequency counts. Return true if
01019  * the current block must be flushed.
01020  */
01021 int _tr_tally (s, dist, lc)
01022     deflate_state *s;
01023     unsigned dist;  /* distance of matched string */
01024     unsigned lc;    /* match length-MIN_MATCH or unmatched char (if dist==0) */
01025 {
01026     s->d_buf[s->last_lit] = (ush)dist;
01027     s->l_buf[s->last_lit++] = (uch)lc;
01028     if (dist == 0) {
01029         /* lc is the unmatched char */
01030         s->dyn_ltree[lc].Freq++;
01031     } else {
01032         s->matches++;
01033         /* Here, lc is the match length - MIN_MATCH */
01034         dist--;             /* dist = match distance - 1 */
01035         Assert((ush)dist < (ush)MAX_DIST(s) &&
01036                (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
01037                (ush)d_code(dist) < (ush)D_CODES,  "_tr_tally: bad match");
01038 
01039         s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++;
01040         s->dyn_dtree[d_code(dist)].Freq++;
01041     }
01042 
01043 #ifdef TRUNCATE_BLOCK
01044     /* Try to guess if it is profitable to stop the current block here */
01045     if ((s->last_lit & 0x1fff) == 0 && s->level > 2) {
01046         /* Compute an upper bound for the compressed length */
01047         ulg out_length = (ulg)s->last_lit*8L;
01048         ulg in_length = (ulg)((long)s->strstart - s->block_start);
01049         int dcode;
01050         for (dcode = 0; dcode < D_CODES; dcode++) {
01051             out_length += (ulg)s->dyn_dtree[dcode].Freq *
01052                 (5L+extra_dbits[dcode]);
01053         }
01054         out_length >>= 3;
01055         Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
01056                s->last_lit, in_length, out_length,
01057                100L - out_length*100L/in_length));
01058         if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
01059     }
01060 #endif
01061     return (s->last_lit == s->lit_bufsize-1);
01062     /* We avoid equality with lit_bufsize because of wraparound at 64K
01063      * on 16 bit machines and because stored blocks are restricted to
01064      * 64K-1 bytes.
01065      */
01066 }
01067 
01068 /* ===========================================================================
01069  * Send the block data compressed using the given Huffman trees
01070  */
01071 local void compress_block(s, ltree, dtree)
01072     deflate_state *s;
01073     ct_data *ltree; /* literal tree */
01074     ct_data *dtree; /* distance tree */
01075 {
01076     unsigned dist;      /* distance of matched string */
01077     int lc;             /* match length or unmatched char (if dist == 0) */
01078     unsigned lx = 0;    /* running index in l_buf */
01079     unsigned code;      /* the code to send */
01080     int extra;          /* number of extra bits to send */
01081 
01082     if (s->last_lit != 0) do {
01083         dist = s->d_buf[lx];
01084         lc = s->l_buf[lx++];
01085         if (dist == 0) {
01086             send_code(s, lc, ltree); /* send a literal byte */
01087             Tracecv(isgraph(lc), (stderr," '%c' ", lc));
01088         } else {
01089             /* Here, lc is the match length - MIN_MATCH */
01090             code = _length_code[lc];
01091             send_code(s, code+LITERALS+1, ltree); /* send the length code */
01092             extra = extra_lbits[code];
01093             if (extra != 0) {
01094                 lc -= base_length[code];
01095                 send_bits(s, lc, extra);       /* send the extra length bits */
01096             }
01097             dist--; /* dist is now the match distance - 1 */
01098             code = d_code(dist);
01099             Assert (code < D_CODES, "bad d_code");
01100 
01101             send_code(s, code, dtree);       /* send the distance code */
01102             extra = extra_dbits[code];
01103             if (extra != 0) {
01104                 dist -= base_dist[code];
01105                 send_bits(s, dist, extra);   /* send the extra distance bits */
01106             }
01107         } /* literal or match pair ? */
01108 
01109         /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
01110         Assert(s->pending < s->lit_bufsize + 2*lx, "pendingBuf overflow");
01111 
01112     } while (lx < s->last_lit);
01113 
01114     send_code(s, END_BLOCK, ltree);
01115     s->last_eob_len = ltree[END_BLOCK].Len;
01116 }
01117 
01118 /* ===========================================================================
01119  * Set the data type to ASCII or BINARY, using a crude approximation:
01120  * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
01121  * IN assertion: the fields freq of dyn_ltree are set and the total of all
01122  * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
01123  */
01124 local void set_data_type(s)
01125     deflate_state *s;
01126 {
01127     int n = 0;
01128     unsigned ascii_freq = 0;
01129     unsigned bin_freq = 0;
01130     while (n < 7)        bin_freq += s->dyn_ltree[n++].Freq;
01131     while (n < 128)    ascii_freq += s->dyn_ltree[n++].Freq;
01132     while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq;
01133     s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? Z_BINARY : Z_ASCII);
01134 }
01135 
01136 /* ===========================================================================
01137  * Reverse the first len bits of a code, using straightforward code (a faster
01138  * method would use a table)
01139  * IN assertion: 1 <= len <= 15
01140  */
01141 local unsigned bi_reverse(code, len)
01142     unsigned code; /* the value to invert */
01143     int len;       /* its bit length */
01144 {
01145     register unsigned res = 0;
01146     do {
01147         res |= code & 1;
01148         code >>= 1, res <<= 1;
01149     } while (--len > 0);
01150     return res >> 1;
01151 }
01152 
01153 /* ===========================================================================
01154  * Flush the bit buffer, keeping at most 7 bits in it.
01155  */
01156 local void bi_flush(s)
01157     deflate_state *s;
01158 {
01159     if (s->bi_valid == 16) {
01160         put_short(s, s->bi_buf);
01161         s->bi_buf = 0;
01162         s->bi_valid = 0;
01163     } else if (s->bi_valid >= 8) {
01164         put_byte(s, (Byte)s->bi_buf);
01165         s->bi_buf >>= 8;
01166         s->bi_valid -= 8;
01167     }
01168 }
01169 
01170 /* ===========================================================================
01171  * Flush the bit buffer and align the output on a byte boundary
01172  */
01173 local void bi_windup(s)
01174     deflate_state *s;
01175 {
01176     if (s->bi_valid > 8) {
01177         put_short(s, s->bi_buf);
01178     } else if (s->bi_valid > 0) {
01179         put_byte(s, (Byte)s->bi_buf);
01180     }
01181     s->bi_buf = 0;
01182     s->bi_valid = 0;
01183 #ifdef DEBUG
01184     s->bits_sent = (s->bits_sent+7) & ~7;
01185 #endif
01186 }
01187 
01188 /* ===========================================================================
01189  * Copy a stored block, storing first the length and its
01190  * one's complement if requested.
01191  */
01192 local void copy_block(s, buf, len, header)
01193     deflate_state *s;
01194     charf    *buf;    /* the input data */
01195     unsigned len;     /* its length */
01196     int      header;  /* true if block header must be written */
01197 {
01198     bi_windup(s);        /* align on byte boundary */
01199     s->last_eob_len = 8; /* enough lookahead for inflate */
01200 
01201     if (header) {
01202         put_short(s, (ush)len);   
01203         put_short(s, (ush)~len);
01204 #ifdef DEBUG
01205         s->bits_sent += 2*16;
01206 #endif
01207     }
01208 #ifdef DEBUG
01209     s->bits_sent += (ulg)len<<3;
01210 #endif
01211     while (len--) {
01212         put_byte(s, *buf++);
01213     }
01214 }