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Diffstat (limited to 'isys/gzlib/trees.c')
| -rw-r--r-- | isys/gzlib/trees.c | 1069 |
1 files changed, 0 insertions, 1069 deletions
diff --git a/isys/gzlib/trees.c b/isys/gzlib/trees.c deleted file mode 100644 index 704c3ab6d..000000000 --- a/isys/gzlib/trees.c +++ /dev/null @@ -1,1069 +0,0 @@ -/* 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. - * - * off_t 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 <config.h> -#include <ctype.h> - -#include "tailor.h" -#include "gzip.h" - -#ifdef RCSID -static char rcsid[] = "$Id$"; -#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 near 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 near 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 near 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 near dyn_ltree[HEAP_SIZE]; /* literal and length tree */ -local ct_data near dyn_dtree[2*D_CODES+1]; /* distance tree */ - -local ct_data near 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 near static_dtree[D_CODES]; -/* The static distance tree. (Actually a trivial tree since all codes use - * 5 bits.) - */ - -local ct_data near bl_tree[2*BL_CODES+1]; -/* Huffman tree for the bit lengths */ - -typedef struct tree_desc { - ct_data near *dyn_tree; /* the dynamic tree */ - ct_data near *static_tree; /* corresponding static tree or NULL */ - int near *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 near l_desc = -{dyn_ltree, static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS, 0}; - -local tree_desc near d_desc = -{dyn_dtree, static_dtree, extra_dbits, 0, D_CODES, MAX_BITS, 0}; - -local tree_desc near bl_desc = -{bl_tree, (ct_data near *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS, 0}; - - -local ush near bl_count[MAX_BITS+1]; -/* number of codes at each bit length for an optimal tree */ - -local uch near 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 near 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 near 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 near base_length[LENGTH_CODES]; -/* First normalized length for each code (0 = MIN_MATCH) */ - -local int near 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 near 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 off_t compressed_len; /* total bit length of compressed file */ - -local off_t 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 off_t bits_sent; /* bit length of the compressed data */ -#endif - -extern long block_start; /* window offset of current block */ -extern unsigned near strstart; /* window offset of current string */ - -/* =========================================================================== - * Local (static) routines in this file. - */ - -local void init_block OF((void)); -local void pqdownheap OF((ct_data near *tree, int k)); -local void gen_bitlen OF((tree_desc near *desc)); -local void gen_codes OF((ct_data near *tree, int max_code)); -local void build_tree OF((tree_desc near *desc)); -local void scan_tree OF((ct_data near *tree, int max_code)); -local void send_tree OF((ct_data near *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 near *ltree, ct_data near *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) \ - { 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 near *)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 near *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 near *desc; /* the tree descriptor */ -{ - ct_data near *tree = desc->dyn_tree; - int near *extra = desc->extra_bits; - int base = desc->extra_base; - int max_code = desc->max_code; - int max_length = desc->max_length; - ct_data near *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 near *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 near *desc; /* the tree descriptor */ -{ - ct_data near *tree = desc->dyn_tree; - ct_data near *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 near *)desc); - - /* The field len is now set, we can generate the bit codes */ - gen_codes ((ct_data near *)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 near *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 near *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 near *)dyn_ltree, l_desc.max_code); - scan_tree((ct_data near *)dyn_dtree, d_desc.max_code); - - /* Build the bit length tree: */ - build_tree((tree_desc near *)(&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 %lu, stat %lu", 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); - } - - send_tree((ct_data near *)dyn_ltree, lcodes-1); /* send the literal tree */ - - send_tree((ct_data near *)dyn_dtree, dcodes-1); /* send the distance tree */ -} - -/* =========================================================================== - * 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. - */ -off_t 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 near *)(&l_desc)); - Tracev((stderr, "\nlit data: dyn %lu, stat %lu", opt_len, static_len)); - - build_tree((tree_desc near *)(&d_desc)); - Tracev((stderr, "\ndist data: dyn %lu, stat %lu", 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) gzerror ("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 near *)static_ltree, (ct_data near *)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 near *)dyn_ltree, (ct_data near *)dyn_dtree); - compressed_len += 3 + opt_len; - } - Assert (compressed_len == bits_sent, "bad compressed size"); - init_block(); - - if (eof) { - Assert (input_len == bytes_in, "bad input size"); - bi_windup(); - compressed_len += 7; /* align on byte boundary */ - } - - 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 near *ltree; /* literal tree */ - ct_data near *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) { - warning ("-l used on binary file"); - } -} |