1060 lines · c
1/* +++ trees.c */2/* trees.c -- output deflated data using Huffman coding3 * Copyright (C) 1995-1996 Jean-loup Gailly4 * For conditions of distribution and use, see copyright notice in zlib.h 5 */6 7/*8 * ALGORITHM9 *10 * The "deflation" process uses several Huffman trees. The more11 * common source values are represented by shorter bit sequences.12 *13 * Each code tree is stored in a compressed form which is itself14 * a Huffman encoding of the lengths of all the code strings (in15 * ascending order by source values). The actual code strings are16 * reconstructed from the lengths in the inflate process, as described17 * in the deflate specification.18 *19 * REFERENCES20 *21 * Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".22 * Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc23 *24 * Storer, James A.25 * Data Compression: Methods and Theory, pp. 49-50.26 * Computer Science Press, 1988. ISBN 0-7167-8156-5.27 *28 * Sedgewick, R.29 * Algorithms, p290.30 * Addison-Wesley, 1983. ISBN 0-201-06672-6.31 */32 33/* From: trees.c,v 1.11 1996/07/24 13:41:06 me Exp $ */34 35/* #include "deflate.h" */36 37#include <linux/zutil.h>38#include <linux/bitrev.h>39#include "defutil.h"40 41#ifdef DEBUG_ZLIB42# include <ctype.h>43#endif44 45/* ===========================================================================46 * Constants47 */48 49#define MAX_BL_BITS 750/* Bit length codes must not exceed MAX_BL_BITS bits */51 52#define END_BLOCK 25653/* end of block literal code */54 55#define REP_3_6 1656/* repeat previous bit length 3-6 times (2 bits of repeat count) */57 58#define REPZ_3_10 1759/* repeat a zero length 3-10 times (3 bits of repeat count) */60 61#define REPZ_11_138 1862/* repeat a zero length 11-138 times (7 bits of repeat count) */63 64static const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */65 = {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};66 67static const int extra_dbits[D_CODES] /* extra bits for each distance code */68 = {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};69 70static const int extra_blbits[BL_CODES]/* extra bits for each bit length code */71 = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};72 73static const uch bl_order[BL_CODES]74 = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};75/* The lengths of the bit length codes are sent in order of decreasing76 * probability, to avoid transmitting the lengths for unused bit length codes.77 */78 79/* ===========================================================================80 * Local data. These are initialized only once.81 */82 83static ct_data static_ltree[L_CODES+2];84/* The static literal tree. Since the bit lengths are imposed, there is no85 * need for the L_CODES extra codes used during heap construction. However86 * The codes 286 and 287 are needed to build a canonical tree (see zlib_tr_init87 * below).88 */89 90static ct_data static_dtree[D_CODES];91/* The static distance tree. (Actually a trivial tree since all codes use92 * 5 bits.)93 */94 95static uch dist_code[512];96/* distance codes. The first 256 values correspond to the distances97 * 3 .. 258, the last 256 values correspond to the top 8 bits of98 * the 15 bit distances.99 */100 101static uch length_code[MAX_MATCH-MIN_MATCH+1];102/* length code for each normalized match length (0 == MIN_MATCH) */103 104static int base_length[LENGTH_CODES];105/* First normalized length for each code (0 = MIN_MATCH) */106 107static int base_dist[D_CODES];108/* First normalized distance for each code (0 = distance of 1) */109 110struct static_tree_desc_s {111 const ct_data *static_tree; /* static tree or NULL */112 const int *extra_bits; /* extra bits for each code or NULL */113 int extra_base; /* base index for extra_bits */114 int elems; /* max number of elements in the tree */115 int max_length; /* max bit length for the codes */116};117 118static static_tree_desc static_l_desc =119{static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};120 121static static_tree_desc static_d_desc =122{static_dtree, extra_dbits, 0, D_CODES, MAX_BITS};123 124static static_tree_desc static_bl_desc =125{(const ct_data *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS};126 127/* ===========================================================================128 * Local (static) routines in this file.129 */130 131static void tr_static_init (void);132static void init_block (deflate_state *s);133static void pqdownheap (deflate_state *s, ct_data *tree, int k);134static void gen_bitlen (deflate_state *s, tree_desc *desc);135static void gen_codes (ct_data *tree, int max_code, ush *bl_count);136static void build_tree (deflate_state *s, tree_desc *desc);137static void scan_tree (deflate_state *s, ct_data *tree, int max_code);138static void send_tree (deflate_state *s, ct_data *tree, int max_code);139static int build_bl_tree (deflate_state *s);140static void send_all_trees (deflate_state *s, int lcodes, int dcodes,141 int blcodes);142static void compress_block (deflate_state *s, ct_data *ltree,143 ct_data *dtree);144static void set_data_type (deflate_state *s);145static void bi_flush (deflate_state *s);146static void copy_block (deflate_state *s, char *buf, unsigned len,147 int header);148 149#ifndef DEBUG_ZLIB150# define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)151 /* Send a code of the given tree. c and tree must not have side effects */152 153#else /* DEBUG_ZLIB */154# define send_code(s, c, tree) \155 { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \156 send_bits(s, tree[c].Code, tree[c].Len); }157#endif158 159#define d_code(dist) \160 ((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)])161/* Mapping from a distance to a distance code. dist is the distance - 1 and162 * must not have side effects. dist_code[256] and dist_code[257] are never163 * used.164 */165 166/* ===========================================================================167 * Initialize the various 'constant' tables. In a multi-threaded environment,168 * this function may be called by two threads concurrently, but this is169 * harmless since both invocations do exactly the same thing.170 */171static void tr_static_init(void)172{173 static int static_init_done;174 int n; /* iterates over tree elements */175 int bits; /* bit counter */176 int length; /* length value */177 int code; /* code value */178 int dist; /* distance index */179 ush bl_count[MAX_BITS+1];180 /* number of codes at each bit length for an optimal tree */181 182 if (static_init_done) return;183 184 /* Initialize the mapping length (0..255) -> length code (0..28) */185 length = 0;186 for (code = 0; code < LENGTH_CODES-1; code++) {187 base_length[code] = length;188 for (n = 0; n < (1<<extra_lbits[code]); n++) {189 length_code[length++] = (uch)code;190 }191 }192 Assert (length == 256, "tr_static_init: length != 256");193 /* Note that the length 255 (match length 258) can be represented194 * in two different ways: code 284 + 5 bits or code 285, so we195 * overwrite length_code[255] to use the best encoding:196 */197 length_code[length-1] = (uch)code;198 199 /* Initialize the mapping dist (0..32K) -> dist code (0..29) */200 dist = 0;201 for (code = 0 ; code < 16; code++) {202 base_dist[code] = dist;203 for (n = 0; n < (1<<extra_dbits[code]); n++) {204 dist_code[dist++] = (uch)code;205 }206 }207 Assert (dist == 256, "tr_static_init: dist != 256");208 dist >>= 7; /* from now on, all distances are divided by 128 */209 for ( ; code < D_CODES; code++) {210 base_dist[code] = dist << 7;211 for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {212 dist_code[256 + dist++] = (uch)code;213 }214 }215 Assert (dist == 256, "tr_static_init: 256+dist != 512");216 217 /* Construct the codes of the static literal tree */218 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;219 n = 0;220 while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;221 while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;222 while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;223 while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;224 /* Codes 286 and 287 do not exist, but we must include them in the225 * tree construction to get a canonical Huffman tree (longest code226 * all ones)227 */228 gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);229 230 /* The static distance tree is trivial: */231 for (n = 0; n < D_CODES; n++) {232 static_dtree[n].Len = 5;233 static_dtree[n].Code = bitrev32((u32)n) >> (32 - 5);234 }235 static_init_done = 1;236}237 238/* ===========================================================================239 * Initialize the tree data structures for a new zlib stream.240 */241void zlib_tr_init(242 deflate_state *s243)244{245 tr_static_init();246 247 s->compressed_len = 0L;248 249 s->l_desc.dyn_tree = s->dyn_ltree;250 s->l_desc.stat_desc = &static_l_desc;251 252 s->d_desc.dyn_tree = s->dyn_dtree;253 s->d_desc.stat_desc = &static_d_desc;254 255 s->bl_desc.dyn_tree = s->bl_tree;256 s->bl_desc.stat_desc = &static_bl_desc;257 258 s->bi_buf = 0;259 s->bi_valid = 0;260 s->last_eob_len = 8; /* enough lookahead for inflate */261#ifdef DEBUG_ZLIB262 s->bits_sent = 0L;263#endif264 265 /* Initialize the first block of the first file: */266 init_block(s);267}268 269/* ===========================================================================270 * Initialize a new block.271 */272static void init_block(273 deflate_state *s274)275{276 int n; /* iterates over tree elements */277 278 /* Initialize the trees. */279 for (n = 0; n < L_CODES; n++) s->dyn_ltree[n].Freq = 0;280 for (n = 0; n < D_CODES; n++) s->dyn_dtree[n].Freq = 0;281 for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;282 283 s->dyn_ltree[END_BLOCK].Freq = 1;284 s->opt_len = s->static_len = 0L;285 s->last_lit = s->matches = 0;286}287 288#define SMALLEST 1289/* Index within the heap array of least frequent node in the Huffman tree */290 291 292/* ===========================================================================293 * Remove the smallest element from the heap and recreate the heap with294 * one less element. Updates heap and heap_len.295 */296#define pqremove(s, tree, top) \297{\298 top = s->heap[SMALLEST]; \299 s->heap[SMALLEST] = s->heap[s->heap_len--]; \300 pqdownheap(s, tree, SMALLEST); \301}302 303/* ===========================================================================304 * Compares to subtrees, using the tree depth as tie breaker when305 * the subtrees have equal frequency. This minimizes the worst case length.306 */307#define smaller(tree, n, m, depth) \308 (tree[n].Freq < tree[m].Freq || \309 (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))310 311/* ===========================================================================312 * Restore the heap property by moving down the tree starting at node k,313 * exchanging a node with the smallest of its two sons if necessary, stopping314 * when the heap property is re-established (each father smaller than its315 * two sons).316 */317static void pqdownheap(318 deflate_state *s,319 ct_data *tree, /* the tree to restore */320 int k /* node to move down */321)322{323 int v = s->heap[k];324 int j = k << 1; /* left son of k */325 while (j <= s->heap_len) {326 /* Set j to the smallest of the two sons: */327 if (j < s->heap_len &&328 smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {329 j++;330 }331 /* Exit if v is smaller than both sons */332 if (smaller(tree, v, s->heap[j], s->depth)) break;333 334 /* Exchange v with the smallest son */335 s->heap[k] = s->heap[j]; k = j;336 337 /* And continue down the tree, setting j to the left son of k */338 j <<= 1;339 }340 s->heap[k] = v;341}342 343/* ===========================================================================344 * Compute the optimal bit lengths for a tree and update the total bit length345 * for the current block.346 * IN assertion: the fields freq and dad are set, heap[heap_max] and347 * above are the tree nodes sorted by increasing frequency.348 * OUT assertions: the field len is set to the optimal bit length, the349 * array bl_count contains the frequencies for each bit length.350 * The length opt_len is updated; static_len is also updated if stree is351 * not null.352 */353static void gen_bitlen(354 deflate_state *s,355 tree_desc *desc /* the tree descriptor */356)357{358 ct_data *tree = desc->dyn_tree;359 int max_code = desc->max_code;360 const ct_data *stree = desc->stat_desc->static_tree;361 const int *extra = desc->stat_desc->extra_bits;362 int base = desc->stat_desc->extra_base;363 int max_length = desc->stat_desc->max_length;364 int h; /* heap index */365 int n, m; /* iterate over the tree elements */366 int bits; /* bit length */367 int xbits; /* extra bits */368 ush f; /* frequency */369 int overflow = 0; /* number of elements with bit length too large */370 371 for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;372 373 /* In a first pass, compute the optimal bit lengths (which may374 * overflow in the case of the bit length tree).375 */376 tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */377 378 for (h = s->heap_max+1; h < HEAP_SIZE; h++) {379 n = s->heap[h];380 bits = tree[tree[n].Dad].Len + 1;381 if (bits > max_length) bits = max_length, overflow++;382 tree[n].Len = (ush)bits;383 /* We overwrite tree[n].Dad which is no longer needed */384 385 if (n > max_code) continue; /* not a leaf node */386 387 s->bl_count[bits]++;388 xbits = 0;389 if (n >= base) xbits = extra[n-base];390 f = tree[n].Freq;391 s->opt_len += (ulg)f * (bits + xbits);392 if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);393 }394 if (overflow == 0) return;395 396 Trace((stderr,"\nbit length overflow\n"));397 /* This happens for example on obj2 and pic of the Calgary corpus */398 399 /* Find the first bit length which could increase: */400 do {401 bits = max_length-1;402 while (s->bl_count[bits] == 0) bits--;403 s->bl_count[bits]--; /* move one leaf down the tree */404 s->bl_count[bits+1] += 2; /* move one overflow item as its brother */405 s->bl_count[max_length]--;406 /* The brother of the overflow item also moves one step up,407 * but this does not affect bl_count[max_length]408 */409 overflow -= 2;410 } while (overflow > 0);411 412 /* Now recompute all bit lengths, scanning in increasing frequency.413 * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all414 * lengths instead of fixing only the wrong ones. This idea is taken415 * from 'ar' written by Haruhiko Okumura.)416 */417 for (bits = max_length; bits != 0; bits--) {418 n = s->bl_count[bits];419 while (n != 0) {420 m = s->heap[--h];421 if (m > max_code) continue;422 if (tree[m].Len != (unsigned) bits) {423 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));424 s->opt_len += ((long)bits - (long)tree[m].Len)425 *(long)tree[m].Freq;426 tree[m].Len = (ush)bits;427 }428 n--;429 }430 }431}432 433/* ===========================================================================434 * Generate the codes for a given tree and bit counts (which need not be435 * optimal).436 * IN assertion: the array bl_count contains the bit length statistics for437 * the given tree and the field len is set for all tree elements.438 * OUT assertion: the field code is set for all tree elements of non439 * zero code length.440 */441static void gen_codes(442 ct_data *tree, /* the tree to decorate */443 int max_code, /* largest code with non zero frequency */444 ush *bl_count /* number of codes at each bit length */445)446{447 ush next_code[MAX_BITS+1]; /* next code value for each bit length */448 ush code = 0; /* running code value */449 int bits; /* bit index */450 int n; /* code index */451 452 /* The distribution counts are first used to generate the code values453 * without bit reversal.454 */455 for (bits = 1; bits <= MAX_BITS; bits++) {456 next_code[bits] = code = (code + bl_count[bits-1]) << 1;457 }458 /* Check that the bit counts in bl_count are consistent. The last code459 * must be all ones.460 */461 Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,462 "inconsistent bit counts");463 Tracev((stderr,"\ngen_codes: max_code %d ", max_code));464 465 for (n = 0; n <= max_code; n++) {466 int len = tree[n].Len;467 if (len == 0) continue;468 /* Now reverse the bits */469 tree[n].Code = bitrev32((u32)(next_code[len]++)) >> (32 - len);470 471 Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",472 n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));473 }474}475 476/* ===========================================================================477 * Construct one Huffman tree and assigns the code bit strings and lengths.478 * Update the total bit length for the current block.479 * IN assertion: the field freq is set for all tree elements.480 * OUT assertions: the fields len and code are set to the optimal bit length481 * and corresponding code. The length opt_len is updated; static_len is482 * also updated if stree is not null. The field max_code is set.483 */484static void build_tree(485 deflate_state *s,486 tree_desc *desc /* the tree descriptor */487)488{489 ct_data *tree = desc->dyn_tree;490 const ct_data *stree = desc->stat_desc->static_tree;491 int elems = desc->stat_desc->elems;492 int n, m; /* iterate over heap elements */493 int max_code = -1; /* largest code with non zero frequency */494 int node; /* new node being created */495 496 /* Construct the initial heap, with least frequent element in497 * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].498 * heap[0] is not used.499 */500 s->heap_len = 0, s->heap_max = HEAP_SIZE;501 502 for (n = 0; n < elems; n++) {503 if (tree[n].Freq != 0) {504 s->heap[++(s->heap_len)] = max_code = n;505 s->depth[n] = 0;506 } else {507 tree[n].Len = 0;508 }509 }510 511 /* The pkzip format requires that at least one distance code exists,512 * and that at least one bit should be sent even if there is only one513 * possible code. So to avoid special checks later on we force at least514 * two codes of non zero frequency.515 */516 while (s->heap_len < 2) {517 node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);518 tree[node].Freq = 1;519 s->depth[node] = 0;520 s->opt_len--; if (stree) s->static_len -= stree[node].Len;521 /* node is 0 or 1 so it does not have extra bits */522 }523 desc->max_code = max_code;524 525 /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,526 * establish sub-heaps of increasing lengths:527 */528 for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);529 530 /* Construct the Huffman tree by repeatedly combining the least two531 * frequent nodes.532 */533 node = elems; /* next internal node of the tree */534 do {535 pqremove(s, tree, n); /* n = node of least frequency */536 m = s->heap[SMALLEST]; /* m = node of next least frequency */537 538 s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */539 s->heap[--(s->heap_max)] = m;540 541 /* Create a new node father of n and m */542 tree[node].Freq = tree[n].Freq + tree[m].Freq;543 s->depth[node] = (uch) (max(s->depth[n], s->depth[m]) + 1);544 tree[n].Dad = tree[m].Dad = (ush)node;545#ifdef DUMP_BL_TREE546 if (tree == s->bl_tree) {547 fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",548 node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);549 }550#endif551 /* and insert the new node in the heap */552 s->heap[SMALLEST] = node++;553 pqdownheap(s, tree, SMALLEST);554 555 } while (s->heap_len >= 2);556 557 s->heap[--(s->heap_max)] = s->heap[SMALLEST];558 559 /* At this point, the fields freq and dad are set. We can now560 * generate the bit lengths.561 */562 gen_bitlen(s, (tree_desc *)desc);563 564 /* The field len is now set, we can generate the bit codes */565 gen_codes ((ct_data *)tree, max_code, s->bl_count);566}567 568/* ===========================================================================569 * Scan a literal or distance tree to determine the frequencies of the codes570 * in the bit length tree.571 */572static void scan_tree(573 deflate_state *s,574 ct_data *tree, /* the tree to be scanned */575 int max_code /* and its largest code of non zero frequency */576)577{578 int n; /* iterates over all tree elements */579 int prevlen = -1; /* last emitted length */580 int curlen; /* length of current code */581 int nextlen = tree[0].Len; /* length of next code */582 int count = 0; /* repeat count of the current code */583 int max_count = 7; /* max repeat count */584 int min_count = 4; /* min repeat count */585 586 if (nextlen == 0) max_count = 138, min_count = 3;587 tree[max_code+1].Len = (ush)0xffff; /* guard */588 589 for (n = 0; n <= max_code; n++) {590 curlen = nextlen; nextlen = tree[n+1].Len;591 if (++count < max_count && curlen == nextlen) {592 continue;593 } else if (count < min_count) {594 s->bl_tree[curlen].Freq += count;595 } else if (curlen != 0) {596 if (curlen != prevlen) s->bl_tree[curlen].Freq++;597 s->bl_tree[REP_3_6].Freq++;598 } else if (count <= 10) {599 s->bl_tree[REPZ_3_10].Freq++;600 } else {601 s->bl_tree[REPZ_11_138].Freq++;602 }603 count = 0; prevlen = curlen;604 if (nextlen == 0) {605 max_count = 138, min_count = 3;606 } else if (curlen == nextlen) {607 max_count = 6, min_count = 3;608 } else {609 max_count = 7, min_count = 4;610 }611 }612}613 614/* ===========================================================================615 * Send a literal or distance tree in compressed form, using the codes in616 * bl_tree.617 */618static void send_tree(619 deflate_state *s,620 ct_data *tree, /* the tree to be scanned */621 int max_code /* and its largest code of non zero frequency */622)623{624 int n; /* iterates over all tree elements */625 int prevlen = -1; /* last emitted length */626 int curlen; /* length of current code */627 int nextlen = tree[0].Len; /* length of next code */628 int count = 0; /* repeat count of the current code */629 int max_count = 7; /* max repeat count */630 int min_count = 4; /* min repeat count */631 632 /* tree[max_code+1].Len = -1; */ /* guard already set */633 if (nextlen == 0) max_count = 138, min_count = 3;634 635 for (n = 0; n <= max_code; n++) {636 curlen = nextlen; nextlen = tree[n+1].Len;637 if (++count < max_count && curlen == nextlen) {638 continue;639 } else if (count < min_count) {640 do { send_code(s, curlen, s->bl_tree); } while (--count != 0);641 642 } else if (curlen != 0) {643 if (curlen != prevlen) {644 send_code(s, curlen, s->bl_tree); count--;645 }646 Assert(count >= 3 && count <= 6, " 3_6?");647 send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);648 649 } else if (count <= 10) {650 send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);651 652 } else {653 send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);654 }655 count = 0; prevlen = curlen;656 if (nextlen == 0) {657 max_count = 138, min_count = 3;658 } else if (curlen == nextlen) {659 max_count = 6, min_count = 3;660 } else {661 max_count = 7, min_count = 4;662 }663 }664}665 666/* ===========================================================================667 * Construct the Huffman tree for the bit lengths and return the index in668 * bl_order of the last bit length code to send.669 */670static int build_bl_tree(671 deflate_state *s672)673{674 int max_blindex; /* index of last bit length code of non zero freq */675 676 /* Determine the bit length frequencies for literal and distance trees */677 scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);678 scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);679 680 /* Build the bit length tree: */681 build_tree(s, (tree_desc *)(&(s->bl_desc)));682 /* opt_len now includes the length of the tree representations, except683 * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.684 */685 686 /* Determine the number of bit length codes to send. The pkzip format687 * requires that at least 4 bit length codes be sent. (appnote.txt says688 * 3 but the actual value used is 4.)689 */690 for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {691 if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;692 }693 /* Update opt_len to include the bit length tree and counts */694 s->opt_len += 3*(max_blindex+1) + 5+5+4;695 Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",696 s->opt_len, s->static_len));697 698 return max_blindex;699}700 701/* ===========================================================================702 * Send the header for a block using dynamic Huffman trees: the counts, the703 * lengths of the bit length codes, the literal tree and the distance tree.704 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.705 */706static void send_all_trees(707 deflate_state *s,708 int lcodes, /* number of codes for each tree */709 int dcodes, /* number of codes for each tree */710 int blcodes /* number of codes for each tree */711)712{713 int rank; /* index in bl_order */714 715 Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");716 Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,717 "too many codes");718 Tracev((stderr, "\nbl counts: "));719 send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */720 send_bits(s, dcodes-1, 5);721 send_bits(s, blcodes-4, 4); /* not -3 as stated in appnote.txt */722 for (rank = 0; rank < blcodes; rank++) {723 Tracev((stderr, "\nbl code %2d ", bl_order[rank]));724 send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);725 }726 Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));727 728 send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */729 Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));730 731 send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */732 Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));733}734 735/* ===========================================================================736 * Send a stored block737 */738void zlib_tr_stored_block(739 deflate_state *s,740 char *buf, /* input block */741 ulg stored_len, /* length of input block */742 int eof /* true if this is the last block for a file */743)744{745 send_bits(s, (STORED_BLOCK<<1)+eof, 3); /* send block type */746 s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;747 s->compressed_len += (stored_len + 4) << 3;748 749 copy_block(s, buf, (unsigned)stored_len, 1); /* with header */750}751 752/* Send just the `stored block' type code without any length bytes or data.753 */754void zlib_tr_stored_type_only(755 deflate_state *s756)757{758 send_bits(s, (STORED_BLOCK << 1), 3);759 bi_windup(s);760 s->compressed_len = (s->compressed_len + 3) & ~7L;761}762 763 764/* ===========================================================================765 * Send one empty static block to give enough lookahead for inflate.766 * This takes 10 bits, of which 7 may remain in the bit buffer.767 * The current inflate code requires 9 bits of lookahead. If the768 * last two codes for the previous block (real code plus EOB) were coded769 * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode770 * the last real code. In this case we send two empty static blocks instead771 * of one. (There are no problems if the previous block is stored or fixed.)772 * To simplify the code, we assume the worst case of last real code encoded773 * on one bit only.774 */775void zlib_tr_align(776 deflate_state *s777)778{779 send_bits(s, STATIC_TREES<<1, 3);780 send_code(s, END_BLOCK, static_ltree);781 s->compressed_len += 10L; /* 3 for block type, 7 for EOB */782 bi_flush(s);783 /* Of the 10 bits for the empty block, we have already sent784 * (10 - bi_valid) bits. The lookahead for the last real code (before785 * the EOB of the previous block) was thus at least one plus the length786 * of the EOB plus what we have just sent of the empty static block.787 */788 if (1 + s->last_eob_len + 10 - s->bi_valid < 9) {789 send_bits(s, STATIC_TREES<<1, 3);790 send_code(s, END_BLOCK, static_ltree);791 s->compressed_len += 10L;792 bi_flush(s);793 }794 s->last_eob_len = 7;795}796 797/* ===========================================================================798 * Determine the best encoding for the current block: dynamic trees, static799 * trees or store, and output the encoded block to the zip file. This function800 * returns the total compressed length for the file so far.801 */802ulg zlib_tr_flush_block(803 deflate_state *s,804 char *buf, /* input block, or NULL if too old */805 ulg stored_len, /* length of input block */806 int eof /* true if this is the last block for a file */807)808{809 ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */810 int max_blindex = 0; /* index of last bit length code of non zero freq */811 812 /* Build the Huffman trees unless a stored block is forced */813 if (s->level > 0) {814 815 /* Check if the file is ascii or binary */816 if (s->data_type == Z_UNKNOWN) set_data_type(s);817 818 /* Construct the literal and distance trees */819 build_tree(s, (tree_desc *)(&(s->l_desc)));820 Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,821 s->static_len));822 823 build_tree(s, (tree_desc *)(&(s->d_desc)));824 Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,825 s->static_len));826 /* At this point, opt_len and static_len are the total bit lengths of827 * the compressed block data, excluding the tree representations.828 */829 830 /* Build the bit length tree for the above two trees, and get the index831 * in bl_order of the last bit length code to send.832 */833 max_blindex = build_bl_tree(s);834 835 /* Determine the best encoding. Compute first the block length in bytes*/836 opt_lenb = (s->opt_len+3+7)>>3;837 static_lenb = (s->static_len+3+7)>>3;838 839 Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",840 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,841 s->last_lit));842 843 if (static_lenb <= opt_lenb) opt_lenb = static_lenb;844 845 } else {846 Assert(buf != (char*)0, "lost buf");847 opt_lenb = static_lenb = stored_len + 5; /* force a stored block */848 }849 850 /* If compression failed and this is the first and last block,851 * and if the .zip file can be seeked (to rewrite the local header),852 * the whole file is transformed into a stored file:853 */854#ifdef STORED_FILE_OK855# ifdef FORCE_STORED_FILE856 if (eof && s->compressed_len == 0L) { /* force stored file */857# else858 if (stored_len <= opt_lenb && eof && s->compressed_len==0L && seekable()) {859# endif860 /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */861 if (buf == (char*)0) error ("block vanished");862 863 copy_block(s, buf, (unsigned)stored_len, 0); /* without header */864 s->compressed_len = stored_len << 3;865 s->method = STORED;866 } else867#endif /* STORED_FILE_OK */868 869#ifdef FORCE_STORED870 if (buf != (char*)0) { /* force stored block */871#else872 if (stored_len+4 <= opt_lenb && buf != (char*)0) {873 /* 4: two words for the lengths */874#endif875 /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.876 * Otherwise we can't have processed more than WSIZE input bytes since877 * the last block flush, because compression would have been878 * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to879 * transform a block into a stored block.880 */881 zlib_tr_stored_block(s, buf, stored_len, eof);882 883#ifdef FORCE_STATIC884 } else if (static_lenb >= 0) { /* force static trees */885#else886 } else if (static_lenb == opt_lenb) {887#endif888 send_bits(s, (STATIC_TREES<<1)+eof, 3);889 compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);890 s->compressed_len += 3 + s->static_len;891 } else {892 send_bits(s, (DYN_TREES<<1)+eof, 3);893 send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,894 max_blindex+1);895 compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);896 s->compressed_len += 3 + s->opt_len;897 }898 Assert (s->compressed_len == s->bits_sent, "bad compressed size");899 init_block(s);900 901 if (eof) {902 bi_windup(s);903 s->compressed_len += 7; /* align on byte boundary */904 }905 Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,906 s->compressed_len-7*eof));907 908 return s->compressed_len >> 3;909}910 911/* ===========================================================================912 * Save the match info and tally the frequency counts. Return true if913 * the current block must be flushed.914 */915int zlib_tr_tally(916 deflate_state *s,917 unsigned dist, /* distance of matched string */918 unsigned lc /* match length-MIN_MATCH or unmatched char (if dist==0) */919)920{921 s->d_buf[s->last_lit] = (ush)dist;922 s->l_buf[s->last_lit++] = (uch)lc;923 if (dist == 0) {924 /* lc is the unmatched char */925 s->dyn_ltree[lc].Freq++;926 } else {927 s->matches++;928 /* Here, lc is the match length - MIN_MATCH */929 dist--; /* dist = match distance - 1 */930 Assert((ush)dist < (ush)MAX_DIST(s) &&931 (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&932 (ush)d_code(dist) < (ush)D_CODES, "zlib_tr_tally: bad match");933 934 s->dyn_ltree[length_code[lc]+LITERALS+1].Freq++;935 s->dyn_dtree[d_code(dist)].Freq++;936 }937 938 /* Try to guess if it is profitable to stop the current block here */939 if ((s->last_lit & 0xfff) == 0 && s->level > 2) {940 /* Compute an upper bound for the compressed length */941 ulg out_length = (ulg)s->last_lit*8L;942 ulg in_length = (ulg)((long)s->strstart - s->block_start);943 int dcode;944 for (dcode = 0; dcode < D_CODES; dcode++) {945 out_length += (ulg)s->dyn_dtree[dcode].Freq *946 (5L+extra_dbits[dcode]);947 }948 out_length >>= 3;949 Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",950 s->last_lit, in_length, out_length,951 100L - out_length*100L/in_length));952 if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;953 }954 return (s->last_lit == s->lit_bufsize-1);955 /* We avoid equality with lit_bufsize because of wraparound at 64K956 * on 16 bit machines and because stored blocks are restricted to957 * 64K-1 bytes.958 */959}960 961/* ===========================================================================962 * Send the block data compressed using the given Huffman trees963 */964static void compress_block(965 deflate_state *s,966 ct_data *ltree, /* literal tree */967 ct_data *dtree /* distance tree */968)969{970 unsigned dist; /* distance of matched string */971 int lc; /* match length or unmatched char (if dist == 0) */972 unsigned lx = 0; /* running index in l_buf */973 unsigned code; /* the code to send */974 int extra; /* number of extra bits to send */975 976 if (s->last_lit != 0) do {977 dist = s->d_buf[lx];978 lc = s->l_buf[lx++];979 if (dist == 0) {980 send_code(s, lc, ltree); /* send a literal byte */981 Tracecv(isgraph(lc), (stderr," '%c' ", lc));982 } else {983 /* Here, lc is the match length - MIN_MATCH */984 code = length_code[lc];985 send_code(s, code+LITERALS+1, ltree); /* send the length code */986 extra = extra_lbits[code];987 if (extra != 0) {988 lc -= base_length[code];989 send_bits(s, lc, extra); /* send the extra length bits */990 }991 dist--; /* dist is now the match distance - 1 */992 code = d_code(dist);993 Assert (code < D_CODES, "bad d_code");994 995 send_code(s, code, dtree); /* send the distance code */996 extra = extra_dbits[code];997 if (extra != 0) {998 dist -= base_dist[code];999 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 all1016 * frequencies does not exceed 64K (to fit in an int on 16 bit machines).1017 */1018static void set_data_type(1019 deflate_state *s1020)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 its1033 * one's complement if requested.1034 */1035static 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_ZLIB1049 s->bits_sent += 2*16;1050#endif1051 }1052#ifdef DEBUG_ZLIB1053 s->bits_sent += (ulg)len<<3;1054#endif1055 /* bundle up the put_byte(s, *buf++) calls */1056 memcpy(&s->pending_buf[s->pending], buf, len);1057 s->pending += len;1058}1059 1060