/* trees.c -- output deflated data using Huffman coding Copyright (C) 1997, 1998, 1999 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 2, 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" #ifdef RCSID static char rcsid[] = "$Id: trees.c,v 1.4 2006/11/20 08:40:33 eggert 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 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) \ { 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, 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) 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 */ } 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"); } }