www.pudn.com > 200410111032011273DESMD5ZLIB算法源代码.rar > Inftrees.cpp
/* inftrees.c -- generate Huffman trees for efficient decoding
* Copyright (C) 1995-1998 Mark Adler
* For conditions of distribution and use, see copyright notice in zlib.h
*/
#include "stdafx.h"
#include "zutil.h"
#include "inftrees.h"
/*const char inflate_copyright[] =
" inflate 1.1.3 Copyright 1995-1998 Mark Adler ";
/*
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.
*/
struct internal_state {int dummy;}; /* for buggy compilers */
/* simplify the use of the inflate_huft type with some defines */
#define exop word.what.Exop
#define bits word.what.Bits
static int huft_build(
unsigned int *, /* code lengths in bits */
unsigned int, /* number of codes */
unsigned int, /* number of "simple" codes */
const unsigned int *, /* list of base values for non-simple codes */
const unsigned int *, /* list of extra bits for non-simple codes */
inflate_huft **,/* result: starting table */
unsigned int *, /* maximum lookup bits (returns actual) */
inflate_huft *, /* space for trees */
unsigned int *, /* hufts used in space */
unsigned int * ); /* space for values */
/* Tables for deflate from PKZIP's appnote.txt. */
static const unsigned int 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 */
static const unsigned int 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 */
static const unsigned int 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};
static const unsigned int 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};
/*
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.
*/
#define BMAX 15 /* maximum bit length of any code */
static int huft_build(
unsigned int *b, /* code lengths in bits (all assumed <= BMAX) */
unsigned int n, /* number of codes (assumed <= 288) */
unsigned int s, /* number of simple-valued codes (0..s-1) */
const unsigned int *d, /* list of base values for non-simple codes */
const unsigned int *e, /* list of extra bits for non-simple codes */
inflate_huft **t, /* result: starting table */
unsigned int *m, /* maximum lookup bits, returns actual */
inflate_huft *hp, /* space for trees */
unsigned int *hn, /* hufts used in space */
unsigned int *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), Z_DATA_ERROR if the input is invalid (an over-subscribed set of
lengths), or Z_MEM_ERROR if not enough memory. */
{
unsigned int a; /* counter for codes of length k */
unsigned int c[BMAX+1]; /* bit length count table */
unsigned int f; /* i repeats in table every f entries */
int g; /* maximum code length */
int h; /* table level */
register unsigned int i; /* counter, current code */
register unsigned int j; /* counter */
register int k; /* number of bits in current code */
int l; /* bits per table (returned in m) */
unsigned int mask; /* (1 << w) - 1, to avoid cc -O bug on HP */
register unsigned int *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) */
unsigned int x[BMAX+1]; /* bit offsets, then code stack */
unsigned int *xp; /* pointer into x */
int y; /* number of dummy codes added */
unsigned int z; /* number of entries in current table */
/* 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;
}
/* 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 ((unsigned int)l < j)
l = j;
for (i = BMAX; i; i--)
if (c[i])
break;
g = i; /* maximum code length */
if ((unsigned int)l > i)
l = i;
*m = l;
/* 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;
/* 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++);
}
/* 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 */
/* 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 */
/* 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 */
/* compute minimum size table less than or equal to l bits */
z = g - w;
z = z > (unsigned int)l ? 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 */
/* allocate new table */
if (*hn + z > MANY) /* (note: doesn't matter for fixed) */
return Z_MEM_ERROR; /* not enough memory */
u[h] = q = hp + *hn;
*hn += z;
/* 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 = (unsigned int)(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 */
}
/* 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];
}
/* fill code-like entries with r */
f = 1 << (k - w);
for (j = i >> w; j < z; j += f)
q[j] = r;
/* backwards increment the k-bit code i */
for (j = 1 << (k - 1); i & j; j >>= 1)
i ^= j;
i ^= j;
/* 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;
}
}
}
/* Return Z_BUF_ERROR if we were given an incomplete table */
return y != 0 && g != 1 ? Z_BUF_ERROR : Z_OK;
}
int inflate_trees_bits(
unsigned int *c, /* 19 code lengths */
unsigned int *bb, /* bits tree desired/actual depth */
inflate_huft **tb, /* bits tree result */
inflate_huft *hp, /* space for trees */
z_streamp z) /* for messages */
{
int r;
unsigned int hn = 0; /* hufts used in space */
unsigned int *v; /* work area for huft_build */
if ((v = (unsigned int*)ZALLOC(z, 19, sizeof(unsigned int))) == Z_NULL)
return Z_MEM_ERROR;
r = huft_build(c, 19, 19, (unsigned int*)Z_NULL, (unsigned int*)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;
}
int inflate_trees_dynamic(
unsigned int nl, /* number of literal/length codes */
unsigned int nd, /* number of distance codes */
unsigned int *c, /* that many (total) code lengths */
unsigned int *bl, /* literal desired/actual bit depth */
unsigned int *bd, /* distance desired/actual bit depth */
inflate_huft **tl, /* literal/length tree result */
inflate_huft **td, /* distance tree result */
inflate_huft *hp, /* space for trees */
z_streamp z) /* for messages */
{
int r;
unsigned int hn = 0; /* hufts used in space */
unsigned int *v; /* work area for huft_build */
/* allocate work area */
if ((v = (unsigned int*)ZALLOC(z, 288, sizeof(unsigned int))) == Z_NULL)
return Z_MEM_ERROR;
/* 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;
}
/* 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) {
#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
}
/* done */
ZFREE(z, v);
return Z_OK;
}
/* build fixed tables only once--keep them here */
#ifdef BUILDFIXED
static int fixed_built = 0;
#define FIXEDH 544 /* number of hufts used by fixed tables */
static inflate_huft fixed_mem[FIXEDH];
static unsigned int fixed_bl;
static unsigned int fixed_bd;
static inflate_huft *fixed_tl;
static inflate_huft *fixed_td;
#else
#include "inffixed.h"
#endif
int inflate_trees_fixed(
unsigned int *bl, /* literal desired/actual bit depth */
unsigned int *bd, /* distance desired/actual bit depth */
inflate_huft **tl, /* literal/length tree result */
inflate_huft **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 */
unsigned int f = 0; /* number of hufts used in fixed_mem */
unsigned int *c; /* length list for huft_build */
unsigned int *v; /* work area for huft_build */
/* allocate memory */
if ((c = (unsigned int*)ZALLOC(z, 288, sizeof(unsigned int))) == Z_NULL)
return Z_MEM_ERROR;
if ((v = (unsigned int*)ZALLOC(z, 288, sizeof(unsigned int))) == Z_NULL)
{
ZFREE(z, c);
return Z_MEM_ERROR;
}
/* 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);
/* 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);
/* done */
ZFREE(z, v);
ZFREE(z, c);
fixed_built = 1;
}
#endif
*bl = fixed_bl;
*bd = fixed_bd;
*tl = fixed_tl;
*td = fixed_td;
return Z_OK;
}