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Adjust AC decode such that decode *always* stops before storing an unneeded coefficient. Remove extra lines from zag[] as it should not be possible to store a coefficient for k>63, even for corrupted files.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@21283 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Andrew Mahone 2009-06-14 01:19:16 +00:00
parent 02a53fd809
commit e40075e5b7
1 changed files with 11 additions and 16 deletions
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27
apps/recorder/jpeg_load.c
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@ -1496,8 +1496,6 @@ static const unsigned char zag[] =
29, 22, 15, 23, 30, 37, 44, 51,
58, 59, 52, 45, 38, 31, 39, 46,
53, 60, 61, 54, 47, 55, 62, 63,
0, 0, 0, 0, 0, 0, 0, 0, /* extra entries in case k>63 below */
0, 0, 0, 0, 0, 0, 0, 0
};
/* zig[i] is the the zig-zag order position of the i'th element of natural
@ -1949,34 +1947,29 @@ static struct img_part *store_row_jpeg(void *jpeg_args)
/* coefficient buffer must be cleared */
MEMSET(block+1, 0, p_jpeg->zero_need[!!ci] * sizeof(int));
/* Section F.2.2.2: decode the AC coefficients */
for (; k < p_jpeg->k_need[!!ci]; k++)
while(true)
{
huff_decode_ac(p_jpeg, actbl, s);
r = s >> 4;
s &= 15;
k += r;
if (s)
{
k += r;
check_bit_buffer(p_jpeg, s);
if (k >= p_jpeg->k_need[!!ci])
goto skip_rest;
r = get_bits(p_jpeg, s);
r = HUFF_EXTEND(r, s);
int a = zag[k];
if (a <= zag[p_jpeg->k_need[!!ci]] && (a & 7) <=
(zag[p_jpeg->k_need[!!ci]] & 7))
{
r = MULTIPLY16(r, p_jpeg->quanttable[!!ci][k]);
block[zag[k]] = r ;
}
r = MULTIPLY16(r, p_jpeg->quanttable[!!ci][k]);
block[zag[k]] = r ;
}
else
{
if (r != 15)
{
k = 64;
break;
}
k += r;
goto block_end;
}
if ((++k) & 64)
goto block_end;
} /* for k */
}
for (; k < 64; k++)
@ -1989,6 +1982,7 @@ static struct img_part *store_row_jpeg(void *jpeg_args)
{
k += r;
check_bit_buffer(p_jpeg, s);
skip_rest:
drop_bits(p_jpeg, s);
}
else
@ -1998,6 +1992,7 @@ static struct img_part *store_row_jpeg(void *jpeg_args)
k += r;
}
} /* for k */
block_end:
#ifndef HAVE_LCD_COLOR
if (!ci)
#endif