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comparison zlib/trees.c @ 3:5a977ccbc7a9 default tip

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author	darius
date	Sat, 06 Dec 1997 05:41:29 +0000
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+:5a977ccbc7a9
+/* trees.c -- output deflated data using Huffman coding
+* Copyright (C) 1995 Jean-loup Gailly
+* For conditions of distribution and use, see copyright notice in zlib.h
+*/
+/*
+*  ALGORITHM
+*
+*      The "deflation" process uses several Huffman trees. The more
+*      common source values are represented by shorter bit sequences.
+*
+*      Each code tree is stored 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 inflate process, as described
+* in the deflate specification.
+*
+*  REFERENCES
+*
+*      Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
+*      Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
+*
+*      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.
+*/
+/* $Id: trees.c,v 1.1.1.1 1997/12/06 05:41:38 darius Exp $ */
+#include "deflate.h"
+#ifdef DEBUG
+#  include <ctype.h>
+#endif
+/* ===========================================================================
+* Constants
+*/
+#define MAX_BL_BITS 7
+/* Bit length codes must not exceed MAX_BL_BITS bits */
+#define END_BLOCK 256
+/* end of block literal code */
+#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 int extra_lbits[LENGTH_CODES] /* extra bits for each length code */
+= {0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,0};
+local int extra_dbits[D_CODES] /* extra bits for each distance code */
+= {0,0,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13};
+local int extra_blbits[BL_CODES]/* extra bits for each bit length code */
+= {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
+local uch bl_order[BL_CODES]
+= {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
+/* The lengths of the bit length codes are sent in order of decreasing
+* probability, to avoid transmitting the lengths for unused bit length codes.
+*/
+#define Buf_size (8 * 2*sizeof(char))
+/* Number of bits used within bi_buf. (bi_buf might be implemented on
+* more than 16 bits on some systems.)
+*/
+/* ===========================================================================
+* Local data. These are initialized only once.
+* To do: initialize at compile time to be completely reentrant. ???
+*/
+local ct_data static_ltree[L_CODES+2];
+/* The static literal tree. Since the bit lengths are imposed, there is no
+* need for the L_CODES extra codes used during heap construction. However
+* The codes 286 and 287 are needed to build a canonical tree (see ct_init
+* below).
+*/
+local ct_data static_dtree[D_CODES];
+/* The static distance tree. (Actually a trivial tree since all codes use
+* 5 bits.)
+*/
+local 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 uch length_code[MAX_MATCH-MIN_MATCH+1];
+/* length code for each normalized match length (0 == MIN_MATCH) */
+local int base_length[LENGTH_CODES];
+/* First normalized length for each code (0 = MIN_MATCH) */
+local int base_dist[D_CODES];
+/* First normalized distance for each code (0 = distance of 1) */
+struct static_tree_desc_s {
+ct_data *static_tree;        /* static tree or NULL */
+int     *extra_bits;         /* extra bits for each code or NULL */
+int     extra_base;          /* base index for extra_bits */
+int     elems;               /* max number of elements in the tree */
+int     max_length;          /* max bit length for the codes */
+};
+local static_tree_desc  static_l_desc =
+{static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
+local static_tree_desc  static_d_desc =
+{static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};
+local static_tree_desc  static_bl_desc =
+{(ct_data *)0, extra_blbits, 0,      BL_CODES, MAX_BL_BITS};
+/* ===========================================================================
+* Local (static) routines in this file.
+*/
+local void ct_static_init __P((void));
+local void init_block     __P((deflate_state *s));
+local void pqdownheap     __P((deflate_state *s, ct_data *tree, int k));
+local void gen_bitlen     __P((deflate_state *s, tree_desc *desc));
+local void gen_codes      __P((ct_data *tree, int max_code, ush bl_count[]));
+local void build_tree     __P((deflate_state *s, tree_desc *desc));
+local void scan_tree      __P((deflate_state *s, ct_data *tree, int max_code));
+local void send_tree      __P((deflate_state *s, ct_data *tree, int max_code));
+local int  build_bl_tree  __P((deflate_state *s));
+local void send_all_trees __P((deflate_state *s, int lcodes, int dcodes,
+int blcodes));
+local void compress_block __P((deflate_state *s, ct_data *ltree,
+ct_data *dtree));
+local void set_data_type  __P((deflate_state *s));
+local void send_bits      __P((deflate_state *s, int value, int length));
+local unsigned bi_reverse __P((unsigned value, int length));
+local void bi_windup      __P((deflate_state *s));
+local void copy_block     __P((deflate_state *s, char *buf, unsigned len,
+int header));
+#ifndef DEBUG
+#  define send_code(s, c, tree) send_bits(s, 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(s, c, tree) \
+{ if (verbose>1) fprintf(stderr,"\ncd %3d ",(c)); \
+send_bits(s, 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 */
+/* ===========================================================================
+* Initialize the various 'constant' tables.
+* To do: do this at compile time.
+*/
+local void ct_static_init()
+{
+int n;        /* iterates over tree elements */
+int bits;     /* bit counter */
+int length;   /* length value */
+int code;     /* code value */
+int dist;     /* distance index */
+ush bl_count[MAX_BITS+1];
+/* number of codes at each bit length for an optimal tree */
+/* 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_static_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_static_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_static_init: 256+dist != 512");
+/* Construct the codes of the static literal tree */
+for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
+n = 0;
+while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
+while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
+while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
+while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
+/* Codes 286 and 287 do not exist, but we must include them in the
+* tree construction to get a canonical Huffman tree (longest code
+* all ones)
+*/
+gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
+/* 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 tree data structures for a new zlib stream.
+*/
+void ct_init(s)
+deflate_state *s;
+{
+if (static_dtree[0].Len == 0) {
+ct_static_init();              /* To do: at compile time */
+}
+s->compressed_len = 0L;
+s->l_desc.dyn_tree = s->dyn_ltree;
+s->l_desc.stat_desc = &static_l_desc;
+s->d_desc.dyn_tree = s->dyn_dtree;
+s->d_desc.stat_desc = &static_d_desc;
+s->bl_desc.dyn_tree = s->bl_tree;
+s->bl_desc.stat_desc = &static_bl_desc;
+s->bi_buf = 0;
+s->bi_valid = 0;
+#ifdef DEBUG
+s->bits_sent = 0L;
+#endif
+/* Initialize the first block of the first file: */
+init_block(s);
+}
+/* ===========================================================================
+* Initialize a new block.
+*/
+local void init_block(s)
+deflate_state *s;
+{
+int n; /* iterates over tree elements */
+/* Initialize the trees. */
+for (n = 0; n < L_CODES;  n++) s->dyn_ltree[n].Freq = 0;
+for (n = 0; n < D_CODES;  n++) s->dyn_dtree[n].Freq = 0;
+for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
+s->dyn_ltree[END_BLOCK].Freq = 1;
+s->opt_len = s->static_len = 0L;
+s->last_lit = s->matches = 0;
+}
+#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(s, tree, top) \
+{\
+top = s->heap[SMALLEST]; \
+s->heap[SMALLEST] = s->heap[s->heap_len--]; \
+pqdownheap(s, 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, depth) \
+(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(s, tree, k)
+deflate_state *s;
+ct_data *tree;  /* the tree to restore */
+int k;               /* node to move down */
+{
+int v = s->heap[k];
+int j = k << 1;  /* left son of k */
+while (j <= s->heap_len) {
+/* Set j to the smallest of the two sons: */
+if (j < s->heap_len &&
+smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
+j++;
+}
+/* Exit if v is smaller than both sons */
+if (smaller(tree, v, s->heap[j], s->depth)) break;
+/* Exchange v with the smallest son */
+s->heap[k] = s->heap[j];  k = j;
+/* And continue down the tree, setting j to the left son of k */
+j <<= 1;
+}
+s->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(s, desc)
+deflate_state *s;
+tree_desc *desc;    /* the tree descriptor */
+{
+ct_data *tree  = desc->dyn_tree;
+int max_code   = desc->max_code;
+ct_data *stree = desc->stat_desc->static_tree;
+int *extra     = desc->stat_desc->extra_bits;
+int base       = desc->stat_desc->extra_base;
+int max_length = desc->stat_desc->max_length;
+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++) s->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[s->heap[s->heap_max]].Len = 0; /* root of the heap */
+for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
+n = s->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 */
+s->bl_count[bits]++;
+xbits = 0;
+if (n >= base) xbits = extra[n-base];
+f = tree[n].Freq;
+s->opt_len += (ulg)f * (bits + xbits);
+if (stree) s->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 (s->bl_count[bits] == 0) bits--;
+s->bl_count[bits]--;      /* move one leaf down the tree */
+s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
+s->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 = s->bl_count[bits];
+while (n != 0) {
+m = s->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));
+s->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, bl_count)
+ct_data *tree;             /* the tree to decorate */
+int max_code;              /* largest code with non zero frequency */
+ush bl_count[];            /* number of codes at each bit length */
+{
+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(s, desc)
+deflate_state *s;
+tree_desc *desc; /* the tree descriptor */
+{
+ct_data *tree   = desc->dyn_tree;
+ct_data *stree  = desc->stat_desc->static_tree;
+int elems       = desc->stat_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 */
+int new;           /* new node being created */
+/* 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.
+*/
+s->heap_len = 0, s->heap_max = HEAP_SIZE;
+for (n = 0; n < elems; n++) {
+if (tree[n].Freq != 0) {
+s->heap[++(s->heap_len)] = max_code = n;
+s->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 (s->heap_len < 2) {
+new = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
+tree[new].Freq = 1;
+s->depth[new] = 0;
+s->opt_len--; if (stree) s->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 = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
+/* Construct the Huffman tree by repeatedly combining the least two
+* frequent nodes.
+*/
+do {
+pqremove(s, tree, n);  /* n = node of least frequency */
+m = s->heap[SMALLEST]; /* m = node of next least frequency */
+s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
+s->heap[--(s->heap_max)] = m;
+/* Create a new node father of n and m */
+tree[node].Freq = tree[n].Freq + tree[m].Freq;
+s->depth[node] = (uch) (MAX(s->depth[n], s->depth[m]) + 1);
+tree[n].Dad = tree[m].Dad = (ush)node;
+#ifdef DUMP_BL_TREE
+if (tree == s->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 */
+s->heap[SMALLEST] = node++;
+pqdownheap(s, tree, SMALLEST);
+} while (s->heap_len >= 2);
+s->heap[--(s->heap_max)] = s->heap[SMALLEST];
+/* At this point, the fields freq and dad are set. We can now
+* generate the bit lengths.
+*/
+gen_bitlen(s, (tree_desc *)desc);
+/* The field len is now set, we can generate the bit codes */
+gen_codes ((ct_data *)tree, max_code, s->bl_count);
+}
+/* ===========================================================================
+* Scan a literal or distance tree to determine the frequencies of the codes
+* in the bit length tree.
+*/
+local void scan_tree (s, tree, max_code)
+deflate_state *s;
+ct_data *tree;   /* the tree to be scanned */
+int max_code;    /* and its largest code of non zero frequency */
+{
+int n;                     /* iterates over all tree elements */
+int prevlen = -1;          /* last emitted length */
+int curlen;                /* length of current code */
+int nextlen = tree[0].Len; /* length of next code */
+int count = 0;             /* repeat count of the current code */
+int max_count = 7;         /* max repeat count */
+int min_count = 4;         /* min repeat count */
+if (nextlen == 0) max_count = 138, min_count = 3;
+tree[max_code+1].Len = (ush)0xffff; /* guard */
+for (n = 0; n <= max_code; n++) {
+curlen = nextlen; nextlen = tree[n+1].Len;
+if (++count < max_count && curlen == nextlen) {
+continue;
+} else if (count < min_count) {
+s->bl_tree[curlen].Freq += count;
+} else if (curlen != 0) {
+if (curlen != prevlen) s->bl_tree[curlen].Freq++;
+s->bl_tree[REP_3_6].Freq++;
+} else if (count <= 10) {
+s->bl_tree[REPZ_3_10].Freq++;
+} else {
+s->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 (s, tree, max_code)
+deflate_state *s;
+ct_data *tree; /* the tree to be scanned */
+int max_code;       /* and its largest code of non zero frequency */
+{
+int n;                     /* iterates over all tree elements */
+int prevlen = -1;          /* last emitted length */
+int curlen;                /* length of current code */
+int nextlen = tree[0].Len; /* length of next code */
+int count = 0;             /* repeat count of the current code */
+int max_count = 7;         /* max repeat count */
+int min_count = 4;         /* min repeat count */
+/* tree[max_code+1].Len = -1; */  /* guard already set */
+if (nextlen == 0) max_count = 138, min_count = 3;
+for (n = 0; n <= max_code; n++) {
+curlen = nextlen; nextlen = tree[n+1].Len;
+if (++count < max_count && curlen == nextlen) {
+continue;
+} else if (count < min_count) {
+do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
+} else if (curlen != 0) {
+if (curlen != prevlen) {
+send_code(s, curlen, s->bl_tree); count--;
+}
+Assert(count >= 3 && count <= 6, " 3_6?");
+send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
+} else if (count <= 10) {
+send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
+} else {
+send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, 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(s)
+deflate_state *s;
+{
+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(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
+scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
+/* Build the bit length tree: */
+build_tree(s, (tree_desc *)(&(s->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 (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
+}
+/* Update opt_len to include the bit length tree and counts */
+s->opt_len += 3*(max_blindex+1) + 5+5+4;
+Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
+s->opt_len, s->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(s, lcodes, dcodes, blcodes)
+deflate_state *s;
+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(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
+send_bits(s, dcodes-1,   5);
+send_bits(s, 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(s, s->bl_tree[bl_order[rank]].Len, 3);
+}
+Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
+send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
+Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
+send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
+Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
+}
+/* ===========================================================================
+* Send a stored block
+*/
+void ct_stored_block(s, buf, stored_len, eof)
+deflate_state *s;
+char *buf;        /* input block */
+ulg stored_len;   /* length of input block */
+int eof;          /* true if this is the last block for a file */
+{
+send_bits(s, (STORED_BLOCK<<1)+eof, 3);  /* send block type */
+s->compressed_len = (s->compressed_len + 3 + 7) & ~7L;
+s->compressed_len += (stored_len + 4) << 3;
+copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
+}
+/* ===========================================================================
+* Determine the best encoding for the current block: dynamic trees, static
+* trees or store, and output the encoded block to the zip file. This function
+* returns the total compressed length for the file so far.
+*/
+ulg ct_flush_block(s, buf, stored_len, eof)
+deflate_state *s;
+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 */
+/* Check if the file is ascii or binary */
+if (s->data_type == UNKNOWN) set_data_type(s);
+/* Construct the literal and distance trees */
+build_tree(s, (tree_desc *)(&(s->l_desc)));
+Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
+s->static_len));
+build_tree(s, (tree_desc *)(&(s->d_desc)));
+Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
+s->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(s);
+/* Determine the best encoding. Compute first the block length in bytes */
+opt_lenb = (s->opt_len+3+7)>>3;
+static_lenb = (s->static_len+3+7)>>3;
+Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
+opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
+s->last_lit));
+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 STORED_FILE_OK
+#  ifdef FORCE_STORED_FILE
+if (eof && compressed_len == 0L) { /* force stored file */
+#  else
+if (stored_len <= opt_lenb && eof && s->compressed_len==0L && seekable()) {
+#  endif
+/* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
+if (buf == (char*)0) error ("block vanished");
+copy_block(buf, (unsigned)stored_len, 0); /* without header */
+s->compressed_len = stored_len << 3;
+s->method = STORED;
+} else
+#endif /* STORED_FILE_OK */
+#ifdef FORCE_STORED
+if (buf != (char*)0) { /* force stored block */
+#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.
+*/
+ct_stored_block(s, buf, stored_len, eof);
+#ifdef FORCE_STATIC
+} else if (static_lenb >= 0) { /* force static trees */
+#else
+} else if (static_lenb == opt_lenb) {
+#endif
+send_bits(s, (STATIC_TREES<<1)+eof, 3);
+compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
+s->compressed_len += 3 + s->static_len;
+} else {
+send_bits(s, (DYN_TREES<<1)+eof, 3);
+send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
+max_blindex+1);
+compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
+s->compressed_len += 3 + s->opt_len;
+}
+Assert (s->compressed_len == s->bits_sent, "bad compressed size");
+init_block(s);
+if (eof) {
+bi_windup(s);
+s->compressed_len += 7;  /* align on byte boundary */
+}
+Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
+s->compressed_len-7*eof));
+return s->compressed_len >> 3;
+}
+/* ===========================================================================
+* Save the match info and tally the frequency counts. Return true if
+* the current block must be flushed.
+*/
+int ct_tally (s, dist, lc)
+deflate_state *s;
+int dist;  /* distance of matched string */
+int lc;    /* match length-MIN_MATCH or unmatched char (if dist==0) */
+{
+s->d_buf[s->last_lit] = (ush)dist;
+s->l_buf[s->last_lit++] = (uch)lc;
+if (dist == 0) {
+/* lc is the unmatched char */
+s->dyn_ltree[lc].Freq++;
+} else {
+s->matches++;
+/* Here, lc is the match length - MIN_MATCH */
+dist--;             /* dist = match distance - 1 */
+Assert((ush)dist < (ush)MAX_DIST(s) &&
+(ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
+(ush)d_code(dist) < (ush)D_CODES,  "ct_tally: bad match");
+s->dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
+s->dyn_dtree[d_code(dist)].Freq++;
+}
+/* Try to guess if it is profitable to stop the current block here */
+if (s->level > 2 && (s->last_lit & 0xfff) == 0) {
+/* Compute an upper bound for the compressed length */
+ulg out_length = (ulg)s->last_lit*8L;
+ulg in_length = (ulg)s->strstart - s->block_start;
+int dcode;
+for (dcode = 0; dcode < D_CODES; dcode++) {
+out_length += (ulg)s->dyn_dtree[dcode].Freq *
+(5L+extra_dbits[dcode]);
+}
+out_length >>= 3;
+Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
+s->last_lit, in_length, out_length,
+100L - out_length*100L/in_length));
+if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
+}
+return (s->last_lit == s->lit_bufsize-1);
+/* 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(s, ltree, dtree)
+deflate_state *s;
+ct_data *ltree; /* literal tree */
+ct_data *dtree; /* distance tree */
+{
+unsigned dist;      /* distance of matched string */
+int lc;             /* match length or unmatched char (if dist == 0) */
+unsigned lx = 0;    /* running index in l_buf */
+unsigned code;      /* the code to send */
+int extra;          /* number of extra bits to send */
+if (s->last_lit != 0) do {
+dist = s->d_buf[lx];
+lc = s->l_buf[lx++];
+if (dist == 0) {
+send_code(s, 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(s, code+LITERALS+1, ltree); /* send the length code */
+extra = extra_lbits[code];
+if (extra != 0) {
+lc -= base_length[code];
+send_bits(s, lc, extra);       /* send the extra length bits */
+}
+dist--; /* dist is now the match distance - 1 */
+code = d_code(dist);
+Assert (code < D_CODES, "bad d_code");
+send_code(s, code, dtree);       /* send the distance code */
+extra = extra_dbits[code];
+if (extra != 0) {
+dist -= base_dist[code];
+send_bits(s, dist, extra);   /* send the extra distance bits */
+}
+} /* literal or match pair ? */
+/* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
+Assert(s->pending < s->lit_bufsize + 2*lx, "pendingBuf overflow");
+} while (lx < s->last_lit);
+send_code(s, END_BLOCK, ltree);
+}
+/* ===========================================================================
+* Set the data 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_data_type(s)
+deflate_state *s;
+{
+int n = 0;
+unsigned ascii_freq = 0;
+unsigned bin_freq = 0;
+while (n < 7)        bin_freq += s->dyn_ltree[n++].Freq;
+while (n < 128)    ascii_freq += s->dyn_ltree[n++].Freq;
+while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq;
+s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? BINARY : ASCII);
+}
+/* ===========================================================================
+* Output a short LSB first on the stream.
+* IN assertion: there is enough room in pendingBuf.
+*/
+#define put_short(s, w) { \
+put_byte(s, (uch)((w) & 0xff)); \
+put_byte(s, (uch)((ush)(w) >> 8)); \
+}
+/* ===========================================================================
+* Send a value on a given number of bits.
+* IN assertion: length <= 16 and value fits in length bits.
+*/
+local void send_bits(s, value, length)
+deflate_state *s;
+int value;  /* value to send */
+int length; /* number of bits */
+{
+#ifdef DEBUG
+Tracev((stderr," l %2d v %4x ", length, value));
+Assert(length > 0 && length <= 15, "invalid length");
+s->bits_sent += (ulg)length;
+#endif
+/* If not enough room in bi_buf, use (valid) bits from bi_buf and
+* (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
+* unused bits in value.
+*/
+if (s->bi_valid > (int)Buf_size - length) {
+s->bi_buf |= (value << s->bi_valid);
+put_short(s, s->bi_buf);
+s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
+s->bi_valid += length - Buf_size;
+} else {
+s->bi_buf |= value << s->bi_valid;
+s->bi_valid += length;
+}
+}
+/* ===========================================================================
+* Reverse the first len bits of a code, using straightforward code (a faster
+* method would use a table)
+* IN assertion: 1 <= len <= 15
+*/
+local unsigned bi_reverse(code, len)
+unsigned code; /* the value to invert */
+int len;       /* its bit length */
+{
+register unsigned res = 0;
+do {
+res |= code & 1;
+code >>= 1, res <<= 1;
+} while (--len > 0);
+return res >> 1;
+}
+/* ===========================================================================
+* Write out any remaining bits in an incomplete byte.
+*/
+local void bi_windup(s)
+deflate_state *s;
+{
+if (s->bi_valid > 8) {
+put_short(s, s->bi_buf);
+} else if (s->bi_valid > 0) {
+put_byte(s, (Byte)s->bi_buf);
+}
+s->bi_buf = 0;
+s->bi_valid = 0;
+#ifdef DEBUG
+s->bits_sent = (s->bits_sent+7) & ~7;
+#endif
+}
+/* ===========================================================================
+* Copy a stored block, storing first the length and its
+* one's complement if requested.
+*/
+local void copy_block(s, buf, len, header)
+deflate_state *s;
+char     *buf;    /* the input data */
+unsigned len;     /* its length */
+int      header;  /* true if block header must be written */
+{
+bi_windup(s);              /* align on byte boundary */
+if (header) {
+put_short(s, (ush)len);
+put_short(s, (ush)~len);
+#ifdef DEBUG
+s->bits_sent += 2*16;
+#endif
+}
+#ifdef DEBUG
+s->bits_sent += (ulg)len<<3;
+#endif
+while (len--) {
+put_byte(s, *buf++);
+}
+}

Mercurial > ~darius > hgwebdir.cgi > paradise_client

comparison zlib/trees.c @ 3:5a977ccbc7a9 default tip