0,0 → 1,468 |
/* inftrees.c -- generate Huffman trees for efficient decoding |
* Copyright (C) 1995-2002 Mark Adler |
* For conditions of distribution and use, see copyright notice in zlib.h |
*/ |
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#include "zutil.h" |
#include "inftrees.h" |
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#if !defined(BUILDFIXED) && !defined(STDC) |
# define BUILDFIXED /* non ANSI compilers may not accept inffixed.h */ |
#endif |
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|
#if 0 |
local const char inflate_copyright[] = |
" inflate 1.1.4 Copyright 1995-2002 Mark Adler "; |
#endif |
/* |
If you use the zlib library in a product, an acknowledgment is welcome |
in the documentation of your product. If for some reason you cannot |
include such an acknowledgment, I would appreciate that you keep this |
copyright string in the executable of your product. |
*/ |
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/* simplify the use of the inflate_huft type with some defines */ |
#define exop word.what.Exop |
#define bits word.what.Bits |
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local int huft_build OF(( |
uIntf *, /* code lengths in bits */ |
uInt, /* number of codes */ |
uInt, /* number of "simple" codes */ |
const uIntf *, /* list of base values for non-simple codes */ |
const uIntf *, /* list of extra bits for non-simple codes */ |
inflate_huft * FAR*,/* result: starting table */ |
uIntf *, /* maximum lookup bits (returns actual) */ |
inflate_huft *, /* space for trees */ |
uInt *, /* hufts used in space */ |
uIntf * )); /* space for values */ |
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/* Tables for deflate from PKZIP's appnote.txt. */ |
local const uInt cplens[31] = { /* Copy lengths for literal codes 257..285 */ |
3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, |
35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0}; |
/* see note #13 above about 258 */ |
local const uInt cplext[31] = { /* Extra bits for literal codes 257..285 */ |
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, 112, 112}; /* 112==invalid */ |
local const uInt cpdist[30] = { /* Copy offsets for distance codes 0..29 */ |
1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193, |
257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145, |
8193, 12289, 16385, 24577}; |
local const uInt cpdext[30] = { /* Extra bits for distance codes */ |
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}; |
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/* |
Huffman code decoding is performed using a multi-level table lookup. |
The fastest way to decode is to simply build a lookup table whose |
size is determined by the longest code. However, the time it takes |
to build this table can also be a factor if the data being decoded |
is not very long. The most common codes are necessarily the |
shortest codes, so those codes dominate the decoding time, and hence |
the speed. The idea is you can have a shorter table that decodes the |
shorter, more probable codes, and then point to subsidiary tables for |
the longer codes. The time it costs to decode the longer codes is |
then traded against the time it takes to make longer tables. |
|
This results of this trade are in the variables lbits and dbits |
below. lbits is the number of bits the first level table for literal/ |
length codes can decode in one step, and dbits is the same thing for |
the distance codes. Subsequent tables are also less than or equal to |
those sizes. These values may be adjusted either when all of the |
codes are shorter than that, in which case the longest code length in |
bits is used, or when the shortest code is *longer* than the requested |
table size, in which case the length of the shortest code in bits is |
used. |
|
There are two different values for the two tables, since they code a |
different number of possibilities each. The literal/length table |
codes 286 possible values, or in a flat code, a little over eight |
bits. The distance table codes 30 possible values, or a little less |
than five bits, flat. The optimum values for speed end up being |
about one bit more than those, so lbits is 8+1 and dbits is 5+1. |
The optimum values may differ though from machine to machine, and |
possibly even between compilers. Your mileage may vary. |
*/ |
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/* If BMAX needs to be larger than 16, then h and x[] should be uLong. */ |
#define BMAX 15 /* maximum bit length of any code */ |
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local int huft_build( /* b, n, s, d, e, t, m, hp, hn, v) */ |
uIntf *b, /* code lengths in bits (all assumed <= BMAX) */ |
uInt n, /* number of codes (assumed <= 288) */ |
uInt s, /* number of simple-valued codes (0..s-1) */ |
const uIntf *d, /* list of base values for non-simple codes */ |
const uIntf *e, /* list of extra bits for non-simple codes */ |
inflate_huft * FAR *t, /* result: starting table */ |
uIntf *m, /* maximum lookup bits, returns actual */ |
inflate_huft *hp, /* space for trees */ |
uInt *hn, /* hufts used in space */ |
uIntf *v /* working area: values in order of bit length */ |
/* Given a list of code lengths and a maximum table size, make a set of |
tables to decode that set of codes. Return Z_OK on success, Z_BUF_ERROR |
if the given code set is incomplete (the tables are still built in this |
case), or Z_DATA_ERROR if the input is invalid. */ |
) |
{ |
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uInt a; /* counter for codes of length k */ |
uInt c[BMAX+1]; /* bit length count table */ |
uInt f; /* i repeats in table every f entries */ |
int g; /* maximum code length */ |
int h; /* table level */ |
register uInt i; /* counter, current code */ |
register uInt j; /* counter */ |
register int k; /* number of bits in current code */ |
int l; /* bits per table (returned in m) */ |
uInt mask; /* (1 << w) - 1, to avoid cc -O bug on HP */ |
register uIntf *p; /* pointer into c[], b[], or v[] */ |
inflate_huft *q; /* points to current table */ |
struct inflate_huft_s r; /* table entry for structure assignment */ |
inflate_huft *u[BMAX]; /* table stack */ |
register int w; /* bits before this table == (l * h) */ |
uInt x[BMAX+1]; /* bit offsets, then code stack */ |
uIntf *xp; /* pointer into x */ |
int y; /* number of dummy codes added */ |
uInt z; /* number of entries in current table */ |
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/* Make compiler happy */ |
r.base = 0; |
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/* Generate counts for each bit length */ |
p = c; |
#define C0 *p++ = 0; |
#define C2 C0 C0 C0 C0 |
#define C4 C2 C2 C2 C2 |
C4 /* clear c[]--assume BMAX+1 is 16 */ |
p = b; i = n; |
do { |
c[*p++]++; /* assume all entries <= BMAX */ |
} while (--i); |
if (c[0] == n) /* null input--all zero length codes */ |
{ |
*t = (inflate_huft *)Z_NULL; |
*m = 0; |
return Z_OK; |
} |
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/* Find minimum and maximum length, bound *m by those */ |
l = *m; |
for (j = 1; j <= BMAX; j++) |
if (c[j]) |
break; |
k = j; /* minimum code length */ |
if ((uInt)l < j) |
l = j; |
for (i = BMAX; i; i--) |
if (c[i]) |
break; |
g = i; /* maximum code length */ |
if ((uInt)l > i) |
l = i; |
*m = l; |
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/* Adjust last length count to fill out codes, if needed */ |
for (y = 1 << j; j < i; j++, y <<= 1) |
if ((y -= c[j]) < 0) |
return Z_DATA_ERROR; |
if ((y -= c[i]) < 0) |
return Z_DATA_ERROR; |
c[i] += y; |
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/* Generate starting offsets into the value table for each length */ |
x[1] = j = 0; |
p = c + 1; xp = x + 2; |
while (--i) { /* note that i == g from above */ |
*xp++ = (j += *p++); |
} |
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/* Make a table of values in order of bit lengths */ |
p = b; i = 0; |
do { |
if ((j = *p++) != 0) |
v[x[j]++] = i; |
} while (++i < n); |
n = x[g]; /* set n to length of v */ |
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/* Generate the Huffman codes and for each, make the table entries */ |
x[0] = i = 0; /* first Huffman code is zero */ |
p = v; /* grab values in bit order */ |
h = -1; /* no tables yet--level -1 */ |
w = -l; /* bits decoded == (l * h) */ |
u[0] = (inflate_huft *)Z_NULL; /* just to keep compilers happy */ |
q = (inflate_huft *)Z_NULL; /* ditto */ |
z = 0; /* ditto */ |
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/* go through the bit lengths (k already is bits in shortest code) */ |
for (; k <= g; k++) |
{ |
a = c[k]; |
while (a--) |
{ |
/* here i is the Huffman code of length k bits for value *p */ |
/* make tables up to required level */ |
while (k > w + l) |
{ |
h++; |
w += l; /* previous table always l bits */ |
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/* compute minimum size table less than or equal to l bits */ |
z = g - w; |
z = z > (uInt)l ? (uInt)l : z; /* table size upper limit */ |
if ((f = 1 << (j = k - w)) > a + 1) /* try a k-w bit table */ |
{ /* too few codes for k-w bit table */ |
f -= a + 1; /* deduct codes from patterns left */ |
xp = c + k; |
if (j < z) |
while (++j < z) /* try smaller tables up to z bits */ |
{ |
if ((f <<= 1) <= *++xp) |
break; /* enough codes to use up j bits */ |
f -= *xp; /* else deduct codes from patterns */ |
} |
} |
z = 1 << j; /* table entries for j-bit table */ |
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/* allocate new table */ |
if (*hn + z > MANY) /* (note: doesn't matter for fixed) */ |
return Z_DATA_ERROR; /* overflow of MANY */ |
u[h] = q = hp + *hn; |
*hn += z; |
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/* connect to last table, if there is one */ |
if (h) |
{ |
x[h] = i; /* save pattern for backing up */ |
r.bits = (Byte)l; /* bits to dump before this table */ |
r.exop = (Byte)j; /* bits in this table */ |
j = i >> (w - l); |
r.base = (uInt)(q - u[h-1] - j); /* offset to this table */ |
u[h-1][j] = r; /* connect to last table */ |
} |
else |
*t = q; /* first table is returned result */ |
} |
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/* set up table entry in r */ |
r.bits = (Byte)(k - w); |
if (p >= v + n) |
r.exop = 128 + 64; /* out of values--invalid code */ |
else if (*p < s) |
{ |
r.exop = (Byte)(*p < 256 ? 0 : 32 + 64); /* 256 is end-of-block */ |
r.base = *p++; /* simple code is just the value */ |
} |
else |
{ |
r.exop = (Byte)(e[*p - s] + 16 + 64);/* non-simple--look up in lists */ |
r.base = d[*p++ - s]; |
} |
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/* fill code-like entries with r */ |
f = 1 << (k - w); |
for (j = i >> w; j < z; j += f) |
q[j] = r; |
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/* backwards increment the k-bit code i */ |
for (j = 1 << (k - 1); i & j; j >>= 1) |
i ^= j; |
i ^= j; |
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/* backup over finished tables */ |
mask = (1 << w) - 1; /* needed on HP, cc -O bug */ |
while ((i & mask) != x[h]) |
{ |
h--; /* don't need to update q */ |
w -= l; |
mask = (1 << w) - 1; |
} |
} |
} |
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/* Return Z_BUF_ERROR if we were given an incomplete table */ |
return y != 0 && g != 1 ? Z_BUF_ERROR : Z_OK; |
} |
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local int inflate_trees_bits( /* c, bb, tb, hp, z) */ |
uIntf *c, /* 19 code lengths */ |
uIntf *bb, /* bits tree desired/actual depth */ |
inflate_huft * FAR *tb, /* bits tree result */ |
inflate_huft *hp, /* space for trees */ |
z_streamp z /* for messages */ |
) |
{ |
int r; |
uInt hn = 0; /* hufts used in space */ |
uIntf *v; /* work area for huft_build */ |
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if ((v = (uIntf*)ZALLOC(z, 19, sizeof(uInt))) == Z_NULL) |
return Z_MEM_ERROR; |
r = huft_build(c, 19, 19, (uIntf*)Z_NULL, (uIntf*)Z_NULL, |
tb, bb, hp, &hn, v); |
if (r == Z_DATA_ERROR) |
z->msg = (char*)"oversubscribed dynamic bit lengths tree"; |
else if (r == Z_BUF_ERROR || *bb == 0) |
{ |
z->msg = (char*)"incomplete dynamic bit lengths tree"; |
r = Z_DATA_ERROR; |
} |
ZFREE(z, v); |
return r; |
} |
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local int inflate_trees_dynamic( /* nl, nd, c, bl, bd, tl, td, hp, z) */ |
uInt nl, /* number of literal/length codes */ |
uInt nd, /* number of distance codes */ |
uIntf *c, /* that many (total) code lengths */ |
uIntf *bl, /* literal desired/actual bit depth */ |
uIntf *bd, /* distance desired/actual bit depth */ |
inflate_huft * FAR *tl, /* literal/length tree result */ |
inflate_huft * FAR *td, /* distance tree result */ |
inflate_huft *hp, /* space for trees */ |
z_streamp z /* for messages */ |
) |
{ |
int r; |
uInt hn = 0; /* hufts used in space */ |
uIntf *v; /* work area for huft_build */ |
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/* allocate work area */ |
if ((v = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL) |
return Z_MEM_ERROR; |
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/* build literal/length tree */ |
r = huft_build(c, nl, 257, cplens, cplext, tl, bl, hp, &hn, v); |
if (r != Z_OK || *bl == 0) |
{ |
if (r == Z_DATA_ERROR) |
z->msg = (char*)"oversubscribed literal/length tree"; |
else if (r != Z_MEM_ERROR) |
{ |
z->msg = (char*)"incomplete literal/length tree"; |
r = Z_DATA_ERROR; |
} |
ZFREE(z, v); |
return r; |
} |
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/* build distance tree */ |
r = huft_build(c + nl, nd, 0, cpdist, cpdext, td, bd, hp, &hn, v); |
if (r != Z_OK || (*bd == 0 && nl > 257)) |
{ |
if (r == Z_DATA_ERROR) |
z->msg = (char*)"oversubscribed distance tree"; |
else if (r == Z_BUF_ERROR) { |
#if 0 |
{ |
#endif |
#ifdef PKZIP_BUG_WORKAROUND |
r = Z_OK; |
} |
#else |
z->msg = (char*)"incomplete distance tree"; |
r = Z_DATA_ERROR; |
} |
else if (r != Z_MEM_ERROR) |
{ |
z->msg = (char*)"empty distance tree with lengths"; |
r = Z_DATA_ERROR; |
} |
ZFREE(z, v); |
return r; |
#endif |
} |
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/* done */ |
ZFREE(z, v); |
return Z_OK; |
} |
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/* build fixed tables only once--keep them here */ |
#ifdef BUILDFIXED |
local int fixed_built = 0; |
#define FIXEDH 544 /* number of hufts used by fixed tables */ |
local inflate_huft fixed_mem[FIXEDH]; |
local uInt fixed_bl; |
local uInt fixed_bd; |
local inflate_huft *fixed_tl; |
local inflate_huft *fixed_td; |
#else |
#include "inffixed.h" |
#endif |
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local int inflate_trees_fixed( /* bl, bd, tl, td, z) */ |
uIntf *bl, /* literal desired/actual bit depth */ |
uIntf *bd, /* distance desired/actual bit depth */ |
const inflate_huft * FAR *tl, /* literal/length tree result */ |
const inflate_huft * FAR *td, /* distance tree result */ |
z_streamp z /* for memory allocation */ |
) |
{ |
#ifdef BUILDFIXED |
/* build fixed tables if not already */ |
if (!fixed_built) |
{ |
int k; /* temporary variable */ |
uInt f = 0; /* number of hufts used in fixed_mem */ |
uIntf *c; /* length list for huft_build */ |
uIntf *v; /* work area for huft_build */ |
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/* allocate memory */ |
if ((c = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL) |
return Z_MEM_ERROR; |
if ((v = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL) |
{ |
ZFREE(z, c); |
return Z_MEM_ERROR; |
} |
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/* literal table */ |
for (k = 0; k < 144; k++) |
c[k] = 8; |
for (; k < 256; k++) |
c[k] = 9; |
for (; k < 280; k++) |
c[k] = 7; |
for (; k < 288; k++) |
c[k] = 8; |
fixed_bl = 9; |
huft_build(c, 288, 257, cplens, cplext, &fixed_tl, &fixed_bl, |
fixed_mem, &f, v); |
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/* distance table */ |
for (k = 0; k < 30; k++) |
c[k] = 5; |
fixed_bd = 5; |
huft_build(c, 30, 0, cpdist, cpdext, &fixed_td, &fixed_bd, |
fixed_mem, &f, v); |
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/* done */ |
ZFREE(z, v); |
ZFREE(z, c); |
fixed_built = 1; |
} |
#else |
FT_UNUSED(z); |
#endif |
*bl = fixed_bl; |
*bd = fixed_bd; |
*tl = fixed_tl; |
*td = fixed_td; |
return Z_OK; |
} |