kevin/linux
1
Fork 0
Code
ac6295c289
linux/lib/zlib_inflate/inftrees.c
Linus Torvalds c231c7db30 Revert unnecessary zlib_inflate/inftrees.c fix 
It turns out that empty distance code tables are not an error, and that
a compressed block with only literals can validly have an empty table
and should not be flagged as a data error.

Some old versions of gzip had problems with this case, but it does not
affect the zlib code in the kernel.

Analysis and explanations thanks to Sergey Vlasov <vsu@altlinux.ru>

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-08-17 13:07:28 -07:00

413 lines
15 KiB
C
Raw Blame History

/* 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 <linux/zutil.h>
#include "inftrees.h"
#include "infutil.h"
static const char inflate_copyright[] __attribute_used__ =
" 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;
/* 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 (
uInt *, /* code lengths in bits */
uInt, /* number of codes */
uInt, /* number of "simple" codes */
const uInt *, /* list of base values for non-simple codes */
const uInt *, /* list of extra bits for non-simple codes */
inflate_huft **, /* result: starting table */
uInt *, /* maximum lookup bits (returns actual) */
inflate_huft *, /* space for trees */
uInt *, /* hufts used in space */
uInt * ); /* space for values */
/* Tables for deflate from PKZIP's appnote.txt. */
static 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 */
static 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 */
static 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};
static 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};
/*
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.
*/
/* If BMAX needs to be larger than 16, then h and x[] should be uLong. */
#define BMAX 15 /* maximum bit length of any code */
static int huft_build(
uInt *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 uInt *d, /* list of base values for non-simple codes */
const uInt *e, /* list of extra bits for non-simple codes */
inflate_huft **t, /* result: starting table */
uInt *m, /* maximum lookup bits, returns actual */
inflate_huft *hp, /* space for trees */
uInt *hn, /* hufts used in space */
uInt *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. */
{
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 uInt *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 */
uInt *xp; /* pointer into x */
int y; /* number of dummy codes added */
uInt 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 = 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 ((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;
/* 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] = NULL; /* just to keep compilers happy */
q = 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 > (uInt)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_DATA_ERROR; /* overflow of MANY */
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 = (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 */
}
/* 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 zlib_inflate_trees_bits(
uInt *c, /* 19 code lengths */
uInt *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;
uInt hn = 0; /* hufts used in space */
uInt *v; /* work area for huft_build */
v = WS(z)->tree_work_area_1;
r = huft_build(c, 19, 19, NULL, 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;
}
return r;
}
int zlib_inflate_trees_dynamic(
uInt nl, /* number of literal/length codes */
uInt nd, /* number of distance codes */
uInt *c, /* that many (total) code lengths */
uInt *bl, /* literal desired/actual bit depth */
uInt *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;
uInt hn = 0; /* hufts used in space */
uInt *v; /* work area for huft_build */
/* allocate work area */
v = WS(z)->tree_work_area_2;
/* 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;
}
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;
}
return r;
#endif
}
/* done */
return Z_OK;
}
int zlib_inflate_trees_fixed(
uInt *bl, /* literal desired/actual bit depth */
uInt *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 memory allocation */
)
{
int i; /* temporary variable */
unsigned l[288]; /* length list for huft_build */
uInt *v; /* work area for huft_build */
/* set up literal table */
for (i = 0; i < 144; i++)
l[i] = 8;
for (; i < 256; i++)
l[i] = 9;
for (; i < 280; i++)
l[i] = 7;
for (; i < 288; i++) /* make a complete, but wrong code set */
l[i] = 8;
*bl = 9;
v = WS(z)->tree_work_area_1;
if ((i = huft_build(l, 288, 257, cplens, cplext, tl, bl, hp, &i, v)) != 0)
return i;
/* set up distance table */
for (i = 0; i < 30; i++) /* make an incomplete code set */
l[i] = 5;
*bd = 5;
if ((i = huft_build(l, 30, 0, cpdist, cpdext, td, bd, hp, &i, v)) > 1)
return i;
return Z_OK;
}
View Git Blame Copy Permalink