471 lines
16 KiB
C
471 lines
16 KiB
C
/* inftrees.c -- generate Huffman trees for efficient decoding
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* Copyright (C) 1995 Mark Adler
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* For conditions of distribution and use, see copyright notice in zlib.h
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*/
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#include "zutil.h"
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#include "inftrees.h"
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struct internal_state {int dummy;}; /* for buggy compilers */
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/* simplify the use of the inflate_huft type with some defines */
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#define base more.Base
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#define next more.Next
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#define exop word.what.Exop
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#define bits word.what.Bits
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local int huft_build OF((
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uIntf *, /* code lengths in bits */
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uInt, /* number of codes */
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uInt, /* number of "simple" codes */
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uIntf *, /* list of base values for non-simple codes */
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uIntf *, /* list of extra bits for non-simple codes */
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inflate_huft * FAR*,/* result: starting table */
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uIntf *, /* maximum lookup bits (returns actual) */
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z_stream *)); /* for zalloc function */
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local voidp falloc OF((
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voidp, /* opaque pointer (not used) */
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uInt, /* number of items */
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uInt)); /* size of item */
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local void ffree OF((
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voidp q, /* opaque pointer (not used) */
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voidp p)); /* what to free (not used) */
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/* Tables for deflate from PKZIP's appnote.txt. */
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local uInt cplens[] = { /* Copy lengths for literal codes 257..285 */
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3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
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35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0};
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/* actually lengths - 2; also see note #13 above about 258 */
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local uInt cplext[] = { /* Extra bits for literal codes 257..285 */
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0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
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3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 192, 192}; /* 192==invalid */
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local uInt cpdist[] = { /* Copy offsets for distance codes 0..29 */
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1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
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257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
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8193, 12289, 16385, 24577};
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local uInt cpdext[] = { /* Extra bits for distance codes */
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0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
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7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
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12, 12, 13, 13};
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/*
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Huffman code decoding is performed using a multi-level table lookup.
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The fastest way to decode is to simply build a lookup table whose
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size is determined by the longest code. However, the time it takes
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to build this table can also be a factor if the data being decoded
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is not very long. The most common codes are necessarily the
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shortest codes, so those codes dominate the decoding time, and hence
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the speed. The idea is you can have a shorter table that decodes the
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shorter, more probable codes, and then point to subsidiary tables for
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the longer codes. The time it costs to decode the longer codes is
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then traded against the time it takes to make longer tables.
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This results of this trade are in the variables lbits and dbits
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below. lbits is the number of bits the first level table for literal/
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length codes can decode in one step, and dbits is the same thing for
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the distance codes. Subsequent tables are also less than or equal to
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those sizes. These values may be adjusted either when all of the
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codes are shorter than that, in which case the longest code length in
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bits is used, or when the shortest code is *longer* than the requested
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table size, in which case the length of the shortest code in bits is
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used.
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There are two different values for the two tables, since they code a
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different number of possibilities each. The literal/length table
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codes 286 possible values, or in a flat code, a little over eight
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bits. The distance table codes 30 possible values, or a little less
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than five bits, flat. The optimum values for speed end up being
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about one bit more than those, so lbits is 8+1 and dbits is 5+1.
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The optimum values may differ though from machine to machine, and
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possibly even between compilers. Your mileage may vary.
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*/
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/* If BMAX needs to be larger than 16, then h and x[] should be uLong. */
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#define BMAX 15 /* maximum bit length of any code */
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#define N_MAX 288 /* maximum number of codes in any set */
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#ifdef DEBUG
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uInt inflate_hufts;
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#endif
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local int huft_build(b, n, s, d, e, t, m, zs)
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uIntf *b; /* code lengths in bits (all assumed <= BMAX) */
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uInt n; /* number of codes (assumed <= N_MAX) */
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uInt s; /* number of simple-valued codes (0..s-1) */
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uIntf *d; /* list of base values for non-simple codes */
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uIntf *e; /* list of extra bits for non-simple codes */
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inflate_huft * FAR *t; /* result: starting table */
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uIntf *m; /* maximum lookup bits, returns actual */
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z_stream *zs; /* for zalloc function */
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/* Given a list of code lengths and a maximum table size, make a set of
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tables to decode that set of codes. Return Z_OK on success, Z_BUF_ERROR
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if the given code set is incomplete (the tables are still built in this
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case), Z_DATA_ERROR if the input is invalid (all zero length codes or an
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over-subscribed set of lengths), or Z_MEM_ERROR if not enough memory. */
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{
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uInt a; /* counter for codes of length k */
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uInt c[BMAX+1]; /* bit length count table */
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uInt f; /* i repeats in table every f entries */
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int g; /* maximum code length */
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int h; /* table level */
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register uInt i; /* counter, current code */
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register uInt j; /* counter */
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register int k; /* number of bits in current code */
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int l; /* bits per table (returned in m) */
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register uIntf *p; /* pointer into c[], b[], or v[] */
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inflate_huft *q; /* points to current table */
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struct inflate_huft_s r; /* table entry for structure assignment */
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inflate_huft *u[BMAX]; /* table stack */
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uInt v[N_MAX]; /* values in order of bit length */
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register int w; /* bits before this table == (l * h) */
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uInt x[BMAX+1]; /* bit offsets, then code stack */
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uIntf *xp; /* pointer into x */
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int y; /* number of dummy codes added */
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uInt z; /* number of entries in current table */
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/* Generate counts for each bit length */
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p = c;
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#define C0 *p++ = 0;
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#define C2 C0 C0 C0 C0
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#define C4 C2 C2 C2 C2
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C4 /* clear c[]--assume BMAX+1 is 16 */
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p = b; i = n;
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do {
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c[*p++]++; /* assume all entries <= BMAX */
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} while (--i);
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if (c[0] == n) /* null input--all zero length codes */
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{
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*t = (inflate_huft *)Z_NULL;
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*m = 0;
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return Z_OK;
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}
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/* Find minimum and maximum length, bound *m by those */
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l = *m;
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for (j = 1; j <= BMAX; j++)
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if (c[j])
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break;
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k = j; /* minimum code length */
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if ((uInt)l < j)
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l = j;
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for (i = BMAX; i; i--)
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if (c[i])
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break;
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g = i; /* maximum code length */
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if ((uInt)l > i)
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l = i;
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*m = l;
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/* Adjust last length count to fill out codes, if needed */
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for (y = 1 << j; j < i; j++, y <<= 1)
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if ((y -= c[j]) < 0)
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return Z_DATA_ERROR;
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if ((y -= c[i]) < 0)
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return Z_DATA_ERROR;
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c[i] += y;
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/* Generate starting offsets into the value table for each length */
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x[1] = j = 0;
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p = c + 1; xp = x + 2;
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while (--i) { /* note that i == g from above */
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*xp++ = (j += *p++);
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}
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/* Make a table of values in order of bit lengths */
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p = b; i = 0;
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do {
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if ((j = *p++) != 0)
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v[x[j]++] = i;
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} while (++i < n);
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/* Generate the Huffman codes and for each, make the table entries */
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x[0] = i = 0; /* first Huffman code is zero */
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p = v; /* grab values in bit order */
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h = -1; /* no tables yet--level -1 */
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w = -l; /* bits decoded == (l * h) */
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u[0] = (inflate_huft *)Z_NULL; /* just to keep compilers happy */
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q = (inflate_huft *)Z_NULL; /* ditto */
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z = 0; /* ditto */
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/* go through the bit lengths (k already is bits in shortest code) */
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for (; k <= g; k++)
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{
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a = c[k];
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while (a--)
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{
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/* here i is the Huffman code of length k bits for value *p */
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/* make tables up to required level */
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while (k > w + l)
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{
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h++;
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w += l; /* previous table always l bits */
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/* compute minimum size table less than or equal to l bits */
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z = (z = g - w) > (uInt)l ? l : z; /* table size upper limit */
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if ((f = 1 << (j = k - w)) > a + 1) /* try a k-w bit table */
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{ /* too few codes for k-w bit table */
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f -= a + 1; /* deduct codes from patterns left */
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xp = c + k;
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if (j < z)
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while (++j < z) /* try smaller tables up to z bits */
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{
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if ((f <<= 1) <= *++xp)
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break; /* enough codes to use up j bits */
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f -= *xp; /* else deduct codes from patterns */
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}
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}
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z = 1 << j; /* table entries for j-bit table */
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/* allocate and link in new table */
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if ((q = (inflate_huft *)ZALLOC
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(zs,z + 1,sizeof(inflate_huft))) == Z_NULL)
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{
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if (h)
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inflate_trees_free(u[0], zs);
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return Z_MEM_ERROR; /* not enough memory */
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}
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#ifdef DEBUG
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inflate_hufts += z + 1;
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#endif
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*t = q + 1; /* link to list for huft_free() */
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*(t = &(q->next)) = Z_NULL;
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u[h] = ++q; /* table starts after link */
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/* connect to last table, if there is one */
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if (h)
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{
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x[h] = i; /* save pattern for backing up */
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r.bits = (Byte)l; /* bits to dump before this table */
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r.exop = (Byte)j; /* bits in this table */
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r.next = q; /* pointer to this table */
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j = i >> (w - l); /* (get around Turbo C bug) */
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u[h-1][j] = r; /* connect to last table */
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}
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}
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/* set up table entry in r */
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r.bits = (Byte)(k - w);
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if (p >= v + n)
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r.exop = 128 + 64; /* out of values--invalid code */
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else if (*p < s)
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{
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r.exop = (Byte)(*p < 256 ? 0 : 32 + 64); /* 256 is end-of-block */
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r.base = *p++; /* simple code is just the value */
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}
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else
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{
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r.exop = (Byte)e[*p - s] + 16 + 64; /* non-simple--look up in lists */
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r.base = d[*p++ - s];
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}
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/* fill code-like entries with r */
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f = 1 << (k - w);
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for (j = i >> w; j < z; j += f)
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q[j] = r;
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/* backwards increment the k-bit code i */
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for (j = 1 << (k - 1); i & j; j >>= 1)
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i ^= j;
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i ^= j;
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/* backup over finished tables */
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while ((i & ((1 << w) - 1)) != x[h])
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{
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h--; /* don't need to update q */
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w -= l;
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}
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}
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}
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/* Return Z_BUF_ERROR if we were given an incomplete table */
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return y != 0 && g != 1 ? Z_BUF_ERROR : Z_OK;
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}
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int inflate_trees_bits(c, bb, tb, z)
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uIntf *c; /* 19 code lengths */
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uIntf *bb; /* bits tree desired/actual depth */
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inflate_huft * FAR *tb; /* bits tree result */
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z_stream *z; /* for zfree function */
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{
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int r;
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r = huft_build(c, 19, 19, (uIntf*)Z_NULL, (uIntf*)Z_NULL, tb, bb, z);
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if (r == Z_DATA_ERROR)
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z->msg = "oversubscribed dynamic bit lengths tree";
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else if (r == Z_BUF_ERROR)
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{
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inflate_trees_free(*tb, z);
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z->msg = "incomplete dynamic bit lengths tree";
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r = Z_DATA_ERROR;
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}
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return r;
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}
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int inflate_trees_dynamic(nl, nd, c, bl, bd, tl, td, z)
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uInt nl; /* number of literal/length codes */
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uInt nd; /* number of distance codes */
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uIntf *c; /* that many (total) code lengths */
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uIntf *bl; /* literal desired/actual bit depth */
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uIntf *bd; /* distance desired/actual bit depth */
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inflate_huft * FAR *tl; /* literal/length tree result */
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inflate_huft * FAR *td; /* distance tree result */
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z_stream *z; /* for zfree function */
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{
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int r;
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/* build literal/length tree */
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if ((r = huft_build(c, nl, 257, cplens, cplext, tl, bl, z)) != Z_OK)
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{
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if (r == Z_DATA_ERROR)
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z->msg = "oversubscribed literal/length tree";
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else if (r == Z_BUF_ERROR)
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{
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inflate_trees_free(*tl, z);
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z->msg = "incomplete literal/length tree";
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r = Z_DATA_ERROR;
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}
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return r;
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}
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/* build distance tree */
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if ((r = huft_build(c + nl, nd, 0, cpdist, cpdext, td, bd, z)) != Z_OK)
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{
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if (r == Z_DATA_ERROR)
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z->msg = "oversubscribed literal/length tree";
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else if (r == Z_BUF_ERROR) {
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#ifdef PKZIP_BUG_WORKAROUND
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r = Z_OK;
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}
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#else
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inflate_trees_free(*td, z);
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z->msg = "incomplete literal/length tree";
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r = Z_DATA_ERROR;
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}
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inflate_trees_free(*tl, z);
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return r;
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#endif
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}
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/* done */
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return Z_OK;
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}
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/* build fixed tables only once--keep them here */
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local int fixed_lock = 0;
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local int fixed_built = 0;
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#define FIXEDH 530 /* number of hufts used by fixed tables */
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local uInt fixed_left = FIXEDH;
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local inflate_huft fixed_mem[FIXEDH];
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local uInt fixed_bl;
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local uInt fixed_bd;
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local inflate_huft *fixed_tl;
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local inflate_huft *fixed_td;
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local voidp falloc(q, n, s)
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voidp q; /* opaque pointer (not used) */
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uInt n; /* number of items */
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uInt s; /* size of item */
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{
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Assert(s == sizeof(inflate_huft) && n <= fixed_left,
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"inflate_trees falloc overflow");
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if (q) s++; /* to make some compilers happy */
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fixed_left -= n;
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return (voidp)(fixed_mem + fixed_left);
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}
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local void ffree(q, p)
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voidp q;
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voidp p;
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{
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Assert(0, "inflate_trees ffree called!");
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if (q) q = p; /* to make some compilers happy */
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}
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int inflate_trees_fixed(bl, bd, tl, td)
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uIntf *bl; /* literal desired/actual bit depth */
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uIntf *bd; /* distance desired/actual bit depth */
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inflate_huft * FAR *tl; /* literal/length tree result */
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inflate_huft * FAR *td; /* distance tree result */
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{
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/* build fixed tables if not built already--lock out other instances */
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while (++fixed_lock > 1)
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fixed_lock--;
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if (!fixed_built)
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{
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int k; /* temporary variable */
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unsigned c[288]; /* length list for huft_build */
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z_stream z; /* for falloc function */
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/* set up fake z_stream for memory routines */
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z.zalloc = falloc;
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z.zfree = ffree;
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z.opaque = Z_NULL;
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/* literal table */
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for (k = 0; k < 144; k++)
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c[k] = 8;
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for (; k < 256; k++)
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c[k] = 9;
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for (; k < 280; k++)
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c[k] = 7;
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for (; k < 288; k++)
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c[k] = 8;
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fixed_bl = 7;
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huft_build(c, 288, 257, cplens, cplext, &fixed_tl, &fixed_bl, &z);
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/* distance table */
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for (k = 0; k < 30; k++)
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c[k] = 5;
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fixed_bd = 5;
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huft_build(c, 30, 0, cpdist, cpdext, &fixed_td, &fixed_bd, &z);
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/* done */
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fixed_built = 1;
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}
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fixed_lock--;
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*bl = fixed_bl;
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*bd = fixed_bd;
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*tl = fixed_tl;
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*td = fixed_td;
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return Z_OK;
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}
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int inflate_trees_free(t, z)
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inflate_huft *t; /* table to free */
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z_stream *z; /* for zfree function */
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/* Free the malloc'ed tables built by huft_build(), which makes a linked
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list of the tables it made, with the links in a dummy first entry of
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each table. */
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{
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register inflate_huft *p, *q;
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/* Go through linked list, freeing from the malloced (t[-1]) address. */
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p = t;
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while (p != Z_NULL)
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{
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q = (--p)->next;
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ZFREE(z,p);
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p = q;
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}
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return Z_OK;
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}
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