| /* trees.c -- output deflated data using Huffman coding |
| * Copyright (C) 1992-1993 Jean-loup Gailly |
| * This is free software; you can redistribute it and/or modify it under the |
| * terms of the GNU General Public License, see the file COPYING. |
| */ |
| |
| /* |
| * PURPOSE |
| * |
| * Encode various sets of source values using variable-length |
| * binary code trees. |
| * |
| * DISCUSSION |
| * |
| * The PKZIP "deflation" process uses several Huffman trees. The more |
| * common source values are represented by shorter bit sequences. |
| * |
| * Each code tree is stored in the ZIP file in a compressed form |
| * which is itself a Huffman encoding of the lengths of |
| * all the code strings (in ascending order by source values). |
| * The actual code strings are reconstructed from the lengths in |
| * the UNZIP process, as described in the "application note" |
| * (APPNOTE.TXT) distributed as part of PKWARE's PKZIP program. |
| * |
| * REFERENCES |
| * |
| * Lynch, Thomas J. |
| * Data Compression: Techniques and Applications, pp. 53-55. |
| * Lifetime Learning Publications, 1985. ISBN 0-534-03418-7. |
| * |
| * Storer, James A. |
| * Data Compression: Methods and Theory, pp. 49-50. |
| * Computer Science Press, 1988. ISBN 0-7167-8156-5. |
| * |
| * Sedgewick, R. |
| * Algorithms, p290. |
| * Addison-Wesley, 1983. ISBN 0-201-06672-6. |
| * |
| * INTERFACE |
| * |
| * void ct_init (ush *attr, int *methodp) |
| * Allocate the match buffer, initialize the various tables and save |
| * the location of the internal file attribute (ascii/binary) and |
| * method (DEFLATE/STORE) |
| * |
| * void ct_tally (int dist, int lc); |
| * Save the match info and tally the frequency counts. |
| * |
| * long flush_block (char *buf, ulg stored_len, int eof) |
| * Determine the best encoding for the current block: dynamic trees, |
| * static trees or store, and output the encoded block to the zip |
| * file. Returns the total compressed length for the file so far. |
| * |
| */ |
| |
| #include <ctype.h> |
| |
| #include "tailor.h" |
| #include "gzip.h" |
| |
| #ifdef RCSID |
| static char rcsid[] = "$Id: trees.c,v 1.1 2002/08/18 00:59:21 hpa Exp $"; |
| #endif |
| |
| /* =========================================================================== |
| * Constants |
| */ |
| |
| #define MAX_BITS 15 |
| /* All codes must not exceed MAX_BITS bits */ |
| |
| #define MAX_BL_BITS 7 |
| /* Bit length codes must not exceed MAX_BL_BITS bits */ |
| |
| #define LENGTH_CODES 29 |
| /* number of length codes, not counting the special END_BLOCK code */ |
| |
| #define LITERALS 256 |
| /* number of literal bytes 0..255 */ |
| |
| #define END_BLOCK 256 |
| /* end of block literal code */ |
| |
| #define L_CODES (LITERALS+1+LENGTH_CODES) |
| /* number of Literal or Length codes, including the END_BLOCK code */ |
| |
| #define D_CODES 30 |
| /* number of distance codes */ |
| |
| #define BL_CODES 19 |
| /* number of codes used to transfer the bit lengths */ |
| |
| |
| local int extra_lbits[LENGTH_CODES] /* extra bits for each length code */ |
| = {0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,0}; |
| |
| local int extra_dbits[D_CODES] /* extra bits for each distance code */ |
| = {0,0,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13}; |
| |
| local int extra_blbits[BL_CODES]/* extra bits for each bit length code */ |
| = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7}; |
| |
| #define STORED_BLOCK 0 |
| #define STATIC_TREES 1 |
| #define DYN_TREES 2 |
| /* The three kinds of block type */ |
| |
| #ifndef LIT_BUFSIZE |
| # ifdef SMALL_MEM |
| # define LIT_BUFSIZE 0x2000 |
| # else |
| # ifdef MEDIUM_MEM |
| # define LIT_BUFSIZE 0x4000 |
| # else |
| # define LIT_BUFSIZE 0x8000 |
| # endif |
| # endif |
| #endif |
| #ifndef DIST_BUFSIZE |
| # define DIST_BUFSIZE LIT_BUFSIZE |
| #endif |
| /* Sizes of match buffers for literals/lengths and distances. There are |
| * 4 reasons for limiting LIT_BUFSIZE to 64K: |
| * - frequencies can be kept in 16 bit counters |
| * - if compression is not successful for the first block, all input data is |
| * still in the window so we can still emit a stored block even when input |
| * comes from standard input. (This can also be done for all blocks if |
| * LIT_BUFSIZE is not greater than 32K.) |
| * - if compression is not successful for a file smaller than 64K, we can |
| * even emit a stored file instead of a stored block (saving 5 bytes). |
| * - creating new Huffman trees less frequently may not provide fast |
| * adaptation to changes in the input data statistics. (Take for |
| * example a binary file with poorly compressible code followed by |
| * a highly compressible string table.) Smaller buffer sizes give |
| * fast adaptation but have of course the overhead of transmitting trees |
| * more frequently. |
| * - I can't count above 4 |
| * The current code is general and allows DIST_BUFSIZE < LIT_BUFSIZE (to save |
| * memory at the expense of compression). Some optimizations would be possible |
| * if we rely on DIST_BUFSIZE == LIT_BUFSIZE. |
| */ |
| #if LIT_BUFSIZE > INBUFSIZ |
| error cannot overlay l_buf and inbuf |
| #endif |
| |
| #define REP_3_6 16 |
| /* repeat previous bit length 3-6 times (2 bits of repeat count) */ |
| |
| #define REPZ_3_10 17 |
| /* repeat a zero length 3-10 times (3 bits of repeat count) */ |
| |
| #define REPZ_11_138 18 |
| /* repeat a zero length 11-138 times (7 bits of repeat count) */ |
| |
| /* =========================================================================== |
| * Local data |
| */ |
| |
| /* Data structure describing a single value and its code string. */ |
| typedef struct ct_data { |
| union { |
| ush freq; /* frequency count */ |
| ush code; /* bit string */ |
| } fc; |
| union { |
| ush dad; /* father node in Huffman tree */ |
| ush len; /* length of bit string */ |
| } dl; |
| } ct_data; |
| |
| #define Freq fc.freq |
| #define Code fc.code |
| #define Dad dl.dad |
| #define Len dl.len |
| |
| #define HEAP_SIZE (2*L_CODES+1) |
| /* maximum heap size */ |
| |
| local ct_data dyn_ltree[HEAP_SIZE]; /* literal and length tree */ |
| local ct_data dyn_dtree[2*D_CODES+1]; /* distance tree */ |
| |
| local ct_data static_ltree[L_CODES+2]; |
| /* The static literal tree. Since the bit lengths are imposed, there is no |
| * need for the L_CODES extra codes used during heap construction. However |
| * The codes 286 and 287 are needed to build a canonical tree (see ct_init |
| * below). |
| */ |
| |
| local ct_data static_dtree[D_CODES]; |
| /* The static distance tree. (Actually a trivial tree since all codes use |
| * 5 bits.) |
| */ |
| |
| local ct_data bl_tree[2*BL_CODES+1]; |
| /* Huffman tree for the bit lengths */ |
| |
| typedef struct tree_desc { |
| ct_data *dyn_tree; /* the dynamic tree */ |
| ct_data *static_tree; /* corresponding static tree or NULL */ |
| int *extra_bits; /* extra bits for each code or NULL */ |
| int extra_base; /* base index for extra_bits */ |
| int elems; /* max number of elements in the tree */ |
| int max_length; /* max bit length for the codes */ |
| int max_code; /* largest code with non zero frequency */ |
| } tree_desc; |
| |
| local tree_desc l_desc = |
| {dyn_ltree, static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS, 0}; |
| |
| local tree_desc d_desc = |
| {dyn_dtree, static_dtree, extra_dbits, 0, D_CODES, MAX_BITS, 0}; |
| |
| local tree_desc bl_desc = |
| {bl_tree, (ct_data *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS, 0}; |
| |
| |
| local ush bl_count[MAX_BITS+1]; |
| /* number of codes at each bit length for an optimal tree */ |
| |
| local uch bl_order[BL_CODES] |
| = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15}; |
| /* The lengths of the bit length codes are sent in order of decreasing |
| * probability, to avoid transmitting the lengths for unused bit length codes. |
| */ |
| |
| local int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */ |
| local int heap_len; /* number of elements in the heap */ |
| local int heap_max; /* element of largest frequency */ |
| /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used. |
| * The same heap array is used to build all trees. |
| */ |
| |
| local uch depth[2*L_CODES+1]; |
| /* Depth of each subtree used as tie breaker for trees of equal frequency */ |
| |
| local uch length_code[MAX_MATCH-MIN_MATCH+1]; |
| /* length code for each normalized match length (0 == MIN_MATCH) */ |
| |
| local uch dist_code[512]; |
| /* distance codes. The first 256 values correspond to the distances |
| * 3 .. 258, the last 256 values correspond to the top 8 bits of |
| * the 15 bit distances. |
| */ |
| |
| local int base_length[LENGTH_CODES]; |
| /* First normalized length for each code (0 = MIN_MATCH) */ |
| |
| local int base_dist[D_CODES]; |
| /* First normalized distance for each code (0 = distance of 1) */ |
| |
| #define l_buf inbuf |
| /* DECLARE(uch, l_buf, LIT_BUFSIZE); buffer for literals or lengths */ |
| |
| /* DECLARE(ush, d_buf, DIST_BUFSIZE); buffer for distances */ |
| |
| local uch flag_buf[(LIT_BUFSIZE/8)]; |
| /* flag_buf is a bit array distinguishing literals from lengths in |
| * l_buf, thus indicating the presence or absence of a distance. |
| */ |
| |
| local unsigned last_lit; /* running index in l_buf */ |
| local unsigned last_dist; /* running index in d_buf */ |
| local unsigned last_flags; /* running index in flag_buf */ |
| local uch flags; /* current flags not yet saved in flag_buf */ |
| local uch flag_bit; /* current bit used in flags */ |
| /* bits are filled in flags starting at bit 0 (least significant). |
| * Note: these flags are overkill in the current code since we don't |
| * take advantage of DIST_BUFSIZE == LIT_BUFSIZE. |
| */ |
| |
| local ulg opt_len; /* bit length of current block with optimal trees */ |
| local ulg static_len; /* bit length of current block with static trees */ |
| |
| local ulg compressed_len; /* total bit length of compressed file */ |
| |
| local ulg input_len; /* total byte length of input file */ |
| /* input_len is for debugging only since we can get it by other means. */ |
| |
| ush *file_type; /* pointer to UNKNOWN, BINARY or ASCII */ |
| int *file_method; /* pointer to DEFLATE or STORE */ |
| |
| #ifdef DEBUG |
| extern ulg bits_sent; /* bit length of the compressed data */ |
| extern long isize; /* byte length of input file */ |
| #endif |
| |
| extern long block_start; /* window offset of current block */ |
| extern unsigned strstart; /* window offset of current string */ |
| |
| /* =========================================================================== |
| * Local (static) routines in this file. |
| */ |
| |
| local void init_block OF((void)); |
| local void pqdownheap OF((ct_data *tree, int k)); |
| local void gen_bitlen OF((tree_desc *desc)); |
| local void gen_codes OF((ct_data *tree, int max_code)); |
| local void build_tree OF((tree_desc *desc)); |
| local void scan_tree OF((ct_data *tree, int max_code)); |
| local void send_tree OF((ct_data *tree, int max_code)); |
| local int build_bl_tree OF((void)); |
| local void send_all_trees OF((int lcodes, int dcodes, int blcodes)); |
| local void compress_block OF((ct_data *ltree, ct_data *dtree)); |
| local void set_file_type OF((void)); |
| |
| |
| #ifndef DEBUG |
| # define send_code(c, tree) send_bits(tree[c].Code, tree[c].Len) |
| /* Send a code of the given tree. c and tree must not have side effects */ |
| |
| #else /* DEBUG */ |
| # define send_code(c, tree) \ |
| { if (verbose>1) fprintf(stderr,"\ncd %3d ",(c)); \ |
| send_bits(tree[c].Code, tree[c].Len); } |
| #endif |
| |
| #define d_code(dist) \ |
| ((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)]) |
| /* Mapping from a distance to a distance code. dist is the distance - 1 and |
| * must not have side effects. dist_code[256] and dist_code[257] are never |
| * used. |
| */ |
| |
| #define MAX(a,b) (a >= b ? a : b) |
| /* the arguments must not have side effects */ |
| |
| /* =========================================================================== |
| * Allocate the match buffer, initialize the various tables and save the |
| * location of the internal file attribute (ascii/binary) and method |
| * (DEFLATE/STORE). |
| */ |
| void ct_init(attr, methodp) |
| ush *attr; /* pointer to internal file attribute */ |
| int *methodp; /* pointer to compression method */ |
| { |
| int n; /* iterates over tree elements */ |
| int bits; /* bit counter */ |
| int length; /* length value */ |
| int code; /* code value */ |
| int dist; /* distance index */ |
| |
| file_type = attr; |
| file_method = methodp; |
| compressed_len = input_len = 0L; |
| |
| if (static_dtree[0].Len != 0) return; /* ct_init already called */ |
| |
| /* Initialize the mapping length (0..255) -> length code (0..28) */ |
| length = 0; |
| for (code = 0; code < LENGTH_CODES-1; code++) { |
| base_length[code] = length; |
| for (n = 0; n < (1<<extra_lbits[code]); n++) { |
| length_code[length++] = (uch)code; |
| } |
| } |
| Assert (length == 256, "ct_init: length != 256"); |
| /* Note that the length 255 (match length 258) can be represented |
| * in two different ways: code 284 + 5 bits or code 285, so we |
| * overwrite length_code[255] to use the best encoding: |
| */ |
| length_code[length-1] = (uch)code; |
| |
| /* Initialize the mapping dist (0..32K) -> dist code (0..29) */ |
| dist = 0; |
| for (code = 0 ; code < 16; code++) { |
| base_dist[code] = dist; |
| for (n = 0; n < (1<<extra_dbits[code]); n++) { |
| dist_code[dist++] = (uch)code; |
| } |
| } |
| Assert (dist == 256, "ct_init: dist != 256"); |
| dist >>= 7; /* from now on, all distances are divided by 128 */ |
| for ( ; code < D_CODES; code++) { |
| base_dist[code] = dist << 7; |
| for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) { |
| dist_code[256 + dist++] = (uch)code; |
| } |
| } |
| Assert (dist == 256, "ct_init: 256+dist != 512"); |
| |
| /* Construct the codes of the static literal tree */ |
| for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0; |
| n = 0; |
| while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++; |
| while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++; |
| while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++; |
| while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++; |
| /* Codes 286 and 287 do not exist, but we must include them in the |
| * tree construction to get a canonical Huffman tree (longest code |
| * all ones) |
| */ |
| gen_codes((ct_data *)static_ltree, L_CODES+1); |
| |
| /* The static distance tree is trivial: */ |
| for (n = 0; n < D_CODES; n++) { |
| static_dtree[n].Len = 5; |
| static_dtree[n].Code = bi_reverse(n, 5); |
| } |
| |
| /* Initialize the first block of the first file: */ |
| init_block(); |
| } |
| |
| /* =========================================================================== |
| * Initialize a new block. |
| */ |
| local void init_block() |
| { |
| int n; /* iterates over tree elements */ |
| |
| /* Initialize the trees. */ |
| for (n = 0; n < L_CODES; n++) dyn_ltree[n].Freq = 0; |
| for (n = 0; n < D_CODES; n++) dyn_dtree[n].Freq = 0; |
| for (n = 0; n < BL_CODES; n++) bl_tree[n].Freq = 0; |
| |
| dyn_ltree[END_BLOCK].Freq = 1; |
| opt_len = static_len = 0L; |
| last_lit = last_dist = last_flags = 0; |
| flags = 0; flag_bit = 1; |
| } |
| |
| #define SMALLEST 1 |
| /* Index within the heap array of least frequent node in the Huffman tree */ |
| |
| |
| /* =========================================================================== |
| * Remove the smallest element from the heap and recreate the heap with |
| * one less element. Updates heap and heap_len. |
| */ |
| #define pqremove(tree, top) \ |
| {\ |
| top = heap[SMALLEST]; \ |
| heap[SMALLEST] = heap[heap_len--]; \ |
| pqdownheap(tree, SMALLEST); \ |
| } |
| |
| /* =========================================================================== |
| * Compares to subtrees, using the tree depth as tie breaker when |
| * the subtrees have equal frequency. This minimizes the worst case length. |
| */ |
| #define smaller(tree, n, m) \ |
| (tree[n].Freq < tree[m].Freq || \ |
| (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m])) |
| |
| /* =========================================================================== |
| * Restore the heap property by moving down the tree starting at node k, |
| * exchanging a node with the smallest of its two sons if necessary, stopping |
| * when the heap property is re-established (each father smaller than its |
| * two sons). |
| */ |
| local void pqdownheap(tree, k) |
| ct_data *tree; /* the tree to restore */ |
| int k; /* node to move down */ |
| { |
| int v = heap[k]; |
| int j = k << 1; /* left son of k */ |
| while (j <= heap_len) { |
| /* Set j to the smallest of the two sons: */ |
| if (j < heap_len && smaller(tree, heap[j+1], heap[j])) j++; |
| |
| /* Exit if v is smaller than both sons */ |
| if (smaller(tree, v, heap[j])) break; |
| |
| /* Exchange v with the smallest son */ |
| heap[k] = heap[j]; k = j; |
| |
| /* And continue down the tree, setting j to the left son of k */ |
| j <<= 1; |
| } |
| heap[k] = v; |
| } |
| |
| /* =========================================================================== |
| * Compute the optimal bit lengths for a tree and update the total bit length |
| * for the current block. |
| * IN assertion: the fields freq and dad are set, heap[heap_max] and |
| * above are the tree nodes sorted by increasing frequency. |
| * OUT assertions: the field len is set to the optimal bit length, the |
| * array bl_count contains the frequencies for each bit length. |
| * The length opt_len is updated; static_len is also updated if stree is |
| * not null. |
| */ |
| local void gen_bitlen(desc) |
| tree_desc *desc; /* the tree descriptor */ |
| { |
| ct_data *tree = desc->dyn_tree; |
| int *extra = desc->extra_bits; |
| int base = desc->extra_base; |
| int max_code = desc->max_code; |
| int max_length = desc->max_length; |
| ct_data *stree = desc->static_tree; |
| int h; /* heap index */ |
| int n, m; /* iterate over the tree elements */ |
| int bits; /* bit length */ |
| int xbits; /* extra bits */ |
| ush f; /* frequency */ |
| int overflow = 0; /* number of elements with bit length too large */ |
| |
| for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0; |
| |
| /* In a first pass, compute the optimal bit lengths (which may |
| * overflow in the case of the bit length tree). |
| */ |
| tree[heap[heap_max]].Len = 0; /* root of the heap */ |
| |
| for (h = heap_max+1; h < HEAP_SIZE; h++) { |
| n = heap[h]; |
| bits = tree[tree[n].Dad].Len + 1; |
| if (bits > max_length) bits = max_length, overflow++; |
| tree[n].Len = (ush)bits; |
| /* We overwrite tree[n].Dad which is no longer needed */ |
| |
| if (n > max_code) continue; /* not a leaf node */ |
| |
| bl_count[bits]++; |
| xbits = 0; |
| if (n >= base) xbits = extra[n-base]; |
| f = tree[n].Freq; |
| opt_len += (ulg)f * (bits + xbits); |
| if (stree) static_len += (ulg)f * (stree[n].Len + xbits); |
| } |
| if (overflow == 0) return; |
| |
| Trace((stderr,"\nbit length overflow\n")); |
| /* This happens for example on obj2 and pic of the Calgary corpus */ |
| |
| /* Find the first bit length which could increase: */ |
| do { |
| bits = max_length-1; |
| while (bl_count[bits] == 0) bits--; |
| bl_count[bits]--; /* move one leaf down the tree */ |
| bl_count[bits+1] += 2; /* move one overflow item as its brother */ |
| bl_count[max_length]--; |
| /* The brother of the overflow item also moves one step up, |
| * but this does not affect bl_count[max_length] |
| */ |
| overflow -= 2; |
| } while (overflow > 0); |
| |
| /* Now recompute all bit lengths, scanning in increasing frequency. |
| * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all |
| * lengths instead of fixing only the wrong ones. This idea is taken |
| * from 'ar' written by Haruhiko Okumura.) |
| */ |
| for (bits = max_length; bits != 0; bits--) { |
| n = bl_count[bits]; |
| while (n != 0) { |
| m = heap[--h]; |
| if (m > max_code) continue; |
| if (tree[m].Len != (unsigned) bits) { |
| Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits)); |
| opt_len += ((long)bits-(long)tree[m].Len)*(long)tree[m].Freq; |
| tree[m].Len = (ush)bits; |
| } |
| n--; |
| } |
| } |
| } |
| |
| /* =========================================================================== |
| * Generate the codes for a given tree and bit counts (which need not be |
| * optimal). |
| * IN assertion: the array bl_count contains the bit length statistics for |
| * the given tree and the field len is set for all tree elements. |
| * OUT assertion: the field code is set for all tree elements of non |
| * zero code length. |
| */ |
| local void gen_codes (tree, max_code) |
| ct_data *tree; /* the tree to decorate */ |
| int max_code; /* largest code with non zero frequency */ |
| { |
| ush next_code[MAX_BITS+1]; /* next code value for each bit length */ |
| ush code = 0; /* running code value */ |
| int bits; /* bit index */ |
| int n; /* code index */ |
| |
| /* The distribution counts are first used to generate the code values |
| * without bit reversal. |
| */ |
| for (bits = 1; bits <= MAX_BITS; bits++) { |
| next_code[bits] = code = (code + bl_count[bits-1]) << 1; |
| } |
| /* Check that the bit counts in bl_count are consistent. The last code |
| * must be all ones. |
| */ |
| Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1, |
| "inconsistent bit counts"); |
| Tracev((stderr,"\ngen_codes: max_code %d ", max_code)); |
| |
| for (n = 0; n <= max_code; n++) { |
| int len = tree[n].Len; |
| if (len == 0) continue; |
| /* Now reverse the bits */ |
| tree[n].Code = bi_reverse(next_code[len]++, len); |
| |
| Tracec(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ", |
| n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1)); |
| } |
| } |
| |
| /* =========================================================================== |
| * Construct one Huffman tree and assigns the code bit strings and lengths. |
| * Update the total bit length for the current block. |
| * IN assertion: the field freq is set for all tree elements. |
| * OUT assertions: the fields len and code are set to the optimal bit length |
| * and corresponding code. The length opt_len is updated; static_len is |
| * also updated if stree is not null. The field max_code is set. |
| */ |
| local void build_tree(desc) |
| tree_desc *desc; /* the tree descriptor */ |
| { |
| ct_data *tree = desc->dyn_tree; |
| ct_data *stree = desc->static_tree; |
| int elems = desc->elems; |
| int n, m; /* iterate over heap elements */ |
| int max_code = -1; /* largest code with non zero frequency */ |
| int node = elems; /* next internal node of the tree */ |
| |
| /* Construct the initial heap, with least frequent element in |
| * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1]. |
| * heap[0] is not used. |
| */ |
| heap_len = 0, heap_max = HEAP_SIZE; |
| |
| for (n = 0; n < elems; n++) { |
| if (tree[n].Freq != 0) { |
| heap[++heap_len] = max_code = n; |
| depth[n] = 0; |
| } else { |
| tree[n].Len = 0; |
| } |
| } |
| |
| /* The pkzip format requires that at least one distance code exists, |
| * and that at least one bit should be sent even if there is only one |
| * possible code. So to avoid special checks later on we force at least |
| * two codes of non zero frequency. |
| */ |
| while (heap_len < 2) { |
| int new = heap[++heap_len] = (max_code < 2 ? ++max_code : 0); |
| tree[new].Freq = 1; |
| depth[new] = 0; |
| opt_len--; if (stree) static_len -= stree[new].Len; |
| /* new is 0 or 1 so it does not have extra bits */ |
| } |
| desc->max_code = max_code; |
| |
| /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree, |
| * establish sub-heaps of increasing lengths: |
| */ |
| for (n = heap_len/2; n >= 1; n--) pqdownheap(tree, n); |
| |
| /* Construct the Huffman tree by repeatedly combining the least two |
| * frequent nodes. |
| */ |
| do { |
| pqremove(tree, n); /* n = node of least frequency */ |
| m = heap[SMALLEST]; /* m = node of next least frequency */ |
| |
| heap[--heap_max] = n; /* keep the nodes sorted by frequency */ |
| heap[--heap_max] = m; |
| |
| /* Create a new node father of n and m */ |
| tree[node].Freq = tree[n].Freq + tree[m].Freq; |
| depth[node] = (uch) (MAX(depth[n], depth[m]) + 1); |
| tree[n].Dad = tree[m].Dad = (ush)node; |
| #ifdef DUMP_BL_TREE |
| if (tree == bl_tree) { |
| fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)", |
| node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq); |
| } |
| #endif |
| /* and insert the new node in the heap */ |
| heap[SMALLEST] = node++; |
| pqdownheap(tree, SMALLEST); |
| |
| } while (heap_len >= 2); |
| |
| heap[--heap_max] = heap[SMALLEST]; |
| |
| /* At this point, the fields freq and dad are set. We can now |
| * generate the bit lengths. |
| */ |
| gen_bitlen((tree_desc *)desc); |
| |
| /* The field len is now set, we can generate the bit codes */ |
| gen_codes ((ct_data *)tree, max_code); |
| } |
| |
| /* =========================================================================== |
| * Scan a literal or distance tree to determine the frequencies of the codes |
| * in the bit length tree. Updates opt_len to take into account the repeat |
| * counts. (The contribution of the bit length codes will be added later |
| * during the construction of bl_tree.) |
| */ |
| local void scan_tree (tree, max_code) |
| ct_data *tree; /* the tree to be scanned */ |
| int max_code; /* and its largest code of non zero frequency */ |
| { |
| int n; /* iterates over all tree elements */ |
| int prevlen = -1; /* last emitted length */ |
| int curlen; /* length of current code */ |
| int nextlen = tree[0].Len; /* length of next code */ |
| int count = 0; /* repeat count of the current code */ |
| int max_count = 7; /* max repeat count */ |
| int min_count = 4; /* min repeat count */ |
| |
| if (nextlen == 0) max_count = 138, min_count = 3; |
| tree[max_code+1].Len = (ush)0xffff; /* guard */ |
| |
| for (n = 0; n <= max_code; n++) { |
| curlen = nextlen; nextlen = tree[n+1].Len; |
| if (++count < max_count && curlen == nextlen) { |
| continue; |
| } else if (count < min_count) { |
| bl_tree[curlen].Freq += count; |
| } else if (curlen != 0) { |
| if (curlen != prevlen) bl_tree[curlen].Freq++; |
| bl_tree[REP_3_6].Freq++; |
| } else if (count <= 10) { |
| bl_tree[REPZ_3_10].Freq++; |
| } else { |
| bl_tree[REPZ_11_138].Freq++; |
| } |
| count = 0; prevlen = curlen; |
| if (nextlen == 0) { |
| max_count = 138, min_count = 3; |
| } else if (curlen == nextlen) { |
| max_count = 6, min_count = 3; |
| } else { |
| max_count = 7, min_count = 4; |
| } |
| } |
| } |
| |
| /* =========================================================================== |
| * Send a literal or distance tree in compressed form, using the codes in |
| * bl_tree. |
| */ |
| local void send_tree (tree, max_code) |
| ct_data *tree; /* the tree to be scanned */ |
| int max_code; /* and its largest code of non zero frequency */ |
| { |
| int n; /* iterates over all tree elements */ |
| int prevlen = -1; /* last emitted length */ |
| int curlen; /* length of current code */ |
| int nextlen = tree[0].Len; /* length of next code */ |
| int count = 0; /* repeat count of the current code */ |
| int max_count = 7; /* max repeat count */ |
| int min_count = 4; /* min repeat count */ |
| |
| /* tree[max_code+1].Len = -1; */ /* guard already set */ |
| if (nextlen == 0) max_count = 138, min_count = 3; |
| |
| for (n = 0; n <= max_code; n++) { |
| curlen = nextlen; nextlen = tree[n+1].Len; |
| if (++count < max_count && curlen == nextlen) { |
| continue; |
| } else if (count < min_count) { |
| do { send_code(curlen, bl_tree); } while (--count != 0); |
| |
| } else if (curlen != 0) { |
| if (curlen != prevlen) { |
| send_code(curlen, bl_tree); count--; |
| } |
| Assert(count >= 3 && count <= 6, " 3_6?"); |
| send_code(REP_3_6, bl_tree); send_bits(count-3, 2); |
| |
| } else if (count <= 10) { |
| send_code(REPZ_3_10, bl_tree); send_bits(count-3, 3); |
| |
| } else { |
| send_code(REPZ_11_138, bl_tree); send_bits(count-11, 7); |
| } |
| count = 0; prevlen = curlen; |
| if (nextlen == 0) { |
| max_count = 138, min_count = 3; |
| } else if (curlen == nextlen) { |
| max_count = 6, min_count = 3; |
| } else { |
| max_count = 7, min_count = 4; |
| } |
| } |
| } |
| |
| /* =========================================================================== |
| * Construct the Huffman tree for the bit lengths and return the index in |
| * bl_order of the last bit length code to send. |
| */ |
| local int build_bl_tree() |
| { |
| int max_blindex; /* index of last bit length code of non zero freq */ |
| |
| /* Determine the bit length frequencies for literal and distance trees */ |
| scan_tree((ct_data *)dyn_ltree, l_desc.max_code); |
| scan_tree((ct_data *)dyn_dtree, d_desc.max_code); |
| |
| /* Build the bit length tree: */ |
| build_tree((tree_desc *)(&bl_desc)); |
| /* opt_len now includes the length of the tree representations, except |
| * the lengths of the bit lengths codes and the 5+5+4 bits for the counts. |
| */ |
| |
| /* Determine the number of bit length codes to send. The pkzip format |
| * requires that at least 4 bit length codes be sent. (appnote.txt says |
| * 3 but the actual value used is 4.) |
| */ |
| for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) { |
| if (bl_tree[bl_order[max_blindex]].Len != 0) break; |
| } |
| /* Update opt_len to include the bit length tree and counts */ |
| opt_len += 3*(max_blindex+1) + 5+5+4; |
| Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld", opt_len, static_len)); |
| |
| return max_blindex; |
| } |
| |
| /* =========================================================================== |
| * Send the header for a block using dynamic Huffman trees: the counts, the |
| * lengths of the bit length codes, the literal tree and the distance tree. |
| * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4. |
| */ |
| local void send_all_trees(lcodes, dcodes, blcodes) |
| int lcodes, dcodes, blcodes; /* number of codes for each tree */ |
| { |
| int rank; /* index in bl_order */ |
| |
| Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes"); |
| Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES, |
| "too many codes"); |
| Tracev((stderr, "\nbl counts: ")); |
| send_bits(lcodes-257, 5); /* not +255 as stated in appnote.txt */ |
| send_bits(dcodes-1, 5); |
| send_bits(blcodes-4, 4); /* not -3 as stated in appnote.txt */ |
| for (rank = 0; rank < blcodes; rank++) { |
| Tracev((stderr, "\nbl code %2d ", bl_order[rank])); |
| send_bits(bl_tree[bl_order[rank]].Len, 3); |
| } |
| Tracev((stderr, "\nbl tree: sent %ld", bits_sent)); |
| |
| send_tree((ct_data *)dyn_ltree, lcodes-1); /* send the literal tree */ |
| Tracev((stderr, "\nlit tree: sent %ld", bits_sent)); |
| |
| send_tree((ct_data *)dyn_dtree, dcodes-1); /* send the distance tree */ |
| Tracev((stderr, "\ndist tree: sent %ld", bits_sent)); |
| } |
| |
| /* =========================================================================== |
| * Determine the best encoding for the current block: dynamic trees, static |
| * trees or store, and output the encoded block to the zip file. This function |
| * returns the total compressed length for the file so far. |
| */ |
| ulg flush_block(buf, stored_len, eof) |
| char *buf; /* input block, or NULL if too old */ |
| ulg stored_len; /* length of input block */ |
| int eof; /* true if this is the last block for a file */ |
| { |
| ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */ |
| int max_blindex; /* index of last bit length code of non zero freq */ |
| |
| flag_buf[last_flags] = flags; /* Save the flags for the last 8 items */ |
| |
| /* Check if the file is ascii or binary */ |
| if (*file_type == (ush)UNKNOWN) set_file_type(); |
| |
| /* Construct the literal and distance trees */ |
| build_tree((tree_desc *)(&l_desc)); |
| Tracev((stderr, "\nlit data: dyn %ld, stat %ld", opt_len, static_len)); |
| |
| build_tree((tree_desc *)(&d_desc)); |
| Tracev((stderr, "\ndist data: dyn %ld, stat %ld", opt_len, static_len)); |
| /* At this point, opt_len and static_len are the total bit lengths of |
| * the compressed block data, excluding the tree representations. |
| */ |
| |
| /* Build the bit length tree for the above two trees, and get the index |
| * in bl_order of the last bit length code to send. |
| */ |
| max_blindex = build_bl_tree(); |
| |
| /* Determine the best encoding. Compute first the block length in bytes */ |
| opt_lenb = (opt_len+3+7)>>3; |
| static_lenb = (static_len+3+7)>>3; |
| input_len += stored_len; /* for debugging only */ |
| |
| Trace((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u dist %u ", |
| opt_lenb, opt_len, static_lenb, static_len, stored_len, |
| last_lit, last_dist)); |
| |
| if (static_lenb <= opt_lenb) opt_lenb = static_lenb; |
| |
| /* If compression failed and this is the first and last block, |
| * and if the zip file can be seeked (to rewrite the local header), |
| * the whole file is transformed into a stored file: |
| */ |
| #ifdef FORCE_METHOD |
| if (level == 1 && eof && compressed_len == 0L) { /* force stored file */ |
| #else |
| if (stored_len <= opt_lenb && eof && compressed_len == 0L && seekable()) { |
| #endif |
| /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */ |
| if (buf == (char*)0) error ("block vanished"); |
| |
| copy_block(buf, (unsigned)stored_len, 0); /* without header */ |
| compressed_len = stored_len << 3; |
| *file_method = STORED; |
| |
| #ifdef FORCE_METHOD |
| } else if (level == 2 && buf != (char*)0) { /* force stored block */ |
| #else |
| } else if (stored_len+4 <= opt_lenb && buf != (char*)0) { |
| /* 4: two words for the lengths */ |
| #endif |
| /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE. |
| * Otherwise we can't have processed more than WSIZE input bytes since |
| * the last block flush, because compression would have been |
| * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to |
| * transform a block into a stored block. |
| */ |
| send_bits((STORED_BLOCK<<1)+eof, 3); /* send block type */ |
| compressed_len = (compressed_len + 3 + 7) & ~7L; |
| compressed_len += (stored_len + 4) << 3; |
| |
| copy_block(buf, (unsigned)stored_len, 1); /* with header */ |
| |
| #ifdef FORCE_METHOD |
| } else if (level == 3) { /* force static trees */ |
| #else |
| } else if (static_lenb == opt_lenb) { |
| #endif |
| send_bits((STATIC_TREES<<1)+eof, 3); |
| compress_block((ct_data *)static_ltree, (ct_data *)static_dtree); |
| compressed_len += 3 + static_len; |
| } else { |
| send_bits((DYN_TREES<<1)+eof, 3); |
| send_all_trees(l_desc.max_code+1, d_desc.max_code+1, max_blindex+1); |
| compress_block((ct_data *)dyn_ltree, (ct_data *)dyn_dtree); |
| compressed_len += 3 + opt_len; |
| } |
| Assert (compressed_len == bits_sent, "bad compressed size"); |
| init_block(); |
| |
| if (eof) { |
| Assert (input_len == isize, "bad input size"); |
| bi_windup(); |
| compressed_len += 7; /* align on byte boundary */ |
| } |
| Tracev((stderr,"\ncomprlen %lu(%lu) ", compressed_len>>3, |
| compressed_len-7*eof)); |
| |
| return compressed_len >> 3; |
| } |
| |
| /* =========================================================================== |
| * Save the match info and tally the frequency counts. Return true if |
| * the current block must be flushed. |
| */ |
| int ct_tally (dist, lc) |
| int dist; /* distance of matched string */ |
| int lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */ |
| { |
| l_buf[last_lit++] = (uch)lc; |
| if (dist == 0) { |
| /* lc is the unmatched char */ |
| dyn_ltree[lc].Freq++; |
| } else { |
| /* Here, lc is the match length - MIN_MATCH */ |
| dist--; /* dist = match distance - 1 */ |
| Assert((ush)dist < (ush)MAX_DIST && |
| (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) && |
| (ush)d_code(dist) < (ush)D_CODES, "ct_tally: bad match"); |
| |
| dyn_ltree[length_code[lc]+LITERALS+1].Freq++; |
| dyn_dtree[d_code(dist)].Freq++; |
| |
| d_buf[last_dist++] = (ush)dist; |
| flags |= flag_bit; |
| } |
| flag_bit <<= 1; |
| |
| /* Output the flags if they fill a byte: */ |
| if ((last_lit & 7) == 0) { |
| flag_buf[last_flags++] = flags; |
| flags = 0, flag_bit = 1; |
| } |
| /* Try to guess if it is profitable to stop the current block here */ |
| if (level > 2 && (last_lit & 0xfff) == 0) { |
| /* Compute an upper bound for the compressed length */ |
| ulg out_length = (ulg)last_lit*8L; |
| ulg in_length = (ulg)strstart-block_start; |
| int dcode; |
| for (dcode = 0; dcode < D_CODES; dcode++) { |
| out_length += (ulg)dyn_dtree[dcode].Freq*(5L+extra_dbits[dcode]); |
| } |
| out_length >>= 3; |
| Trace((stderr,"\nlast_lit %u, last_dist %u, in %ld, out ~%ld(%ld%%) ", |
| last_lit, last_dist, in_length, out_length, |
| 100L - out_length*100L/in_length)); |
| if (last_dist < last_lit/2 && out_length < in_length/2) return 1; |
| } |
| return (last_lit == LIT_BUFSIZE-1 || last_dist == DIST_BUFSIZE); |
| /* We avoid equality with LIT_BUFSIZE because of wraparound at 64K |
| * on 16 bit machines and because stored blocks are restricted to |
| * 64K-1 bytes. |
| */ |
| } |
| |
| /* =========================================================================== |
| * Send the block data compressed using the given Huffman trees |
| */ |
| local void compress_block(ltree, dtree) |
| ct_data *ltree; /* literal tree */ |
| ct_data *dtree; /* distance tree */ |
| { |
| unsigned dist; /* distance of matched string */ |
| int lc; /* match length or unmatched char (if dist == 0) */ |
| unsigned lx = 0; /* running index in l_buf */ |
| unsigned dx = 0; /* running index in d_buf */ |
| unsigned fx = 0; /* running index in flag_buf */ |
| uch flag = 0; /* current flags */ |
| unsigned code; /* the code to send */ |
| int extra; /* number of extra bits to send */ |
| |
| if (last_lit != 0) do { |
| if ((lx & 7) == 0) flag = flag_buf[fx++]; |
| lc = l_buf[lx++]; |
| if ((flag & 1) == 0) { |
| send_code(lc, ltree); /* send a literal byte */ |
| Tracecv(isgraph(lc), (stderr," '%c' ", lc)); |
| } else { |
| /* Here, lc is the match length - MIN_MATCH */ |
| code = length_code[lc]; |
| send_code(code+LITERALS+1, ltree); /* send the length code */ |
| extra = extra_lbits[code]; |
| if (extra != 0) { |
| lc -= base_length[code]; |
| send_bits(lc, extra); /* send the extra length bits */ |
| } |
| dist = d_buf[dx++]; |
| /* Here, dist is the match distance - 1 */ |
| code = d_code(dist); |
| Assert (code < D_CODES, "bad d_code"); |
| |
| send_code(code, dtree); /* send the distance code */ |
| extra = extra_dbits[code]; |
| if (extra != 0) { |
| dist -= base_dist[code]; |
| send_bits(dist, extra); /* send the extra distance bits */ |
| } |
| } /* literal or match pair ? */ |
| flag >>= 1; |
| } while (lx < last_lit); |
| |
| send_code(END_BLOCK, ltree); |
| } |
| |
| /* =========================================================================== |
| * Set the file type to ASCII or BINARY, using a crude approximation: |
| * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise. |
| * IN assertion: the fields freq of dyn_ltree are set and the total of all |
| * frequencies does not exceed 64K (to fit in an int on 16 bit machines). |
| */ |
| local void set_file_type() |
| { |
| int n = 0; |
| unsigned ascii_freq = 0; |
| unsigned bin_freq = 0; |
| while (n < 7) bin_freq += dyn_ltree[n++].Freq; |
| while (n < 128) ascii_freq += dyn_ltree[n++].Freq; |
| while (n < LITERALS) bin_freq += dyn_ltree[n++].Freq; |
| *file_type = bin_freq > (ascii_freq >> 2) ? BINARY : ASCII; |
| if (*file_type == BINARY && translate_eol) { |
| warn("-l used on binary file", ""); |
| } |
| } |
