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Diffstat (limited to 'trees.c')
| -rw-r--r-- | trees.c | 1085 |
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@@ -0,0 +1,1085 @@ +/* trees.c -- output deflated data using Huffman coding + + Copyright (C) 1997-1999, 2009-2016 Free Software Foundation, Inc. + Copyright (C) 1992-1993 Jean-loup Gailly + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3, or (at your option) + any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software Foundation, + Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ + +/* + * 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" + +/* =========================================================================== + * 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. */ + +static ush *file_type; /* pointer to UNKNOWN, BINARY or ASCII */ +static 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 (void); +local void pqdownheap (ct_data near *tree, int k); +local void gen_bitlen (tree_desc near *desc); +local void gen_codes (ct_data near *tree, int max_code); +local void build_tree (tree_desc near *desc); +local void scan_tree (ct_data near *tree, int max_code); +local void send_tree (ct_data near *tree, int max_code); +local int build_bl_tree (void); +local void send_all_trees (int lcodes, int dcodes, int blcodes); +local void compress_block (ct_data near *ltree, ct_data near *dtree); +local void set_file_type (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 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, pad, eof) + char *buf; /* input block, or NULL if too old */ + ulg stored_len; /* length of input block */ + int pad; /* pad output to byte boundary */ + 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) + gzip_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 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 */ + } else if (pad && (compressed_len % 8) != 0) { + send_bits((STORED_BLOCK<<1)+eof, 3); /* send block type */ + compressed_len = (compressed_len + 3 + 7) & ~7L; + copy_block(buf, 0, 1); /* with header */ + } + + 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"); + } +} |