contains mppc decompression code
git-svn-id: svn://svn.code.sf.net/p/rdesktop/code/trunk/rdesktop@683 423420c4-83ab-492f-b58f-81f9feb106b5
This commit is contained in:
parent
5db5d38a46
commit
519d85c1cf
276
mppc.c
Normal file
276
mppc.c
Normal file
@ -0,0 +1,276 @@
|
||||
#include <stdio.h>
|
||||
#include <string.h>
|
||||
|
||||
#include "rdesktop.h"
|
||||
|
||||
/* mppc-like??? decompression */
|
||||
/* http://www.faqs.org/rfcs/rfc2118.html */
|
||||
|
||||
/* TODO: research the below statements */
|
||||
|
||||
/* there exists one or more patents */
|
||||
/* related to compression algorithms */
|
||||
|
||||
/* since we are only decompressing I */
|
||||
/* think the end-user is safe. */
|
||||
|
||||
/* even if that isn't true, aren't you */
|
||||
/* already paying royalties */
|
||||
/* through the CAL licenses? */
|
||||
|
||||
/* the dictionary is empty when init. like */
|
||||
/* LZ78, which is not patented */
|
||||
|
||||
|
||||
RDPCOMP mppc_dict;
|
||||
|
||||
int
|
||||
mppc_expand(uint8 * data, uint32 clen, uint8 ctype, uint32 * roff, uint32 * rlen)
|
||||
{
|
||||
int k, walker_len = 0, walker;
|
||||
int i = 0;
|
||||
int next_offset, match_off;
|
||||
int match_len;
|
||||
int old_offset, match_bits;
|
||||
|
||||
signed char *dict = &(mppc_dict.hist);
|
||||
|
||||
if ((ctype & RDP_MPPC_COMPRESSED) == 0)
|
||||
{
|
||||
*roff = 0;
|
||||
*rlen = clen;
|
||||
return 0;
|
||||
}
|
||||
|
||||
if ((ctype & RDP_MPPC_RESET) != 0)
|
||||
{
|
||||
mppc_dict.roff = 0;
|
||||
}
|
||||
|
||||
if ((ctype & RDP_MPPC_FLUSH) != 0)
|
||||
{
|
||||
memset(dict, 0, RDP_MPPC_DICT_SIZE);
|
||||
mppc_dict.roff = 0;
|
||||
}
|
||||
|
||||
*roff = 0;
|
||||
*rlen = 0;
|
||||
|
||||
walker = mppc_dict.roff;
|
||||
|
||||
next_offset = walker;
|
||||
old_offset = next_offset;
|
||||
*roff = old_offset;
|
||||
if (clen == 0)
|
||||
return 0;
|
||||
clen += i;
|
||||
|
||||
do
|
||||
{
|
||||
if (walker_len == 0)
|
||||
{
|
||||
if (i >= clen)
|
||||
break;
|
||||
walker = data[i++] << 24;
|
||||
walker_len = 8;
|
||||
}
|
||||
if (walker >= 0)
|
||||
{
|
||||
if (walker_len < 8)
|
||||
{
|
||||
if (i >= clen)
|
||||
{
|
||||
if (walker != 0)
|
||||
return -1;
|
||||
break;
|
||||
}
|
||||
walker |= (data[i++] & 0xff) << (24 - walker_len);
|
||||
walker_len += 8;
|
||||
}
|
||||
if (next_offset >= RDP_MPPC_DICT_SIZE)
|
||||
return -1;
|
||||
dict[next_offset++] = (((uint32) walker) >> ((uint32) 24));
|
||||
walker <<= 8;
|
||||
walker_len -= 8;
|
||||
continue;
|
||||
}
|
||||
walker <<= 1;
|
||||
/* fetch next 8-bits */
|
||||
if (--walker_len == 0)
|
||||
{
|
||||
if (i >= clen)
|
||||
return -1;
|
||||
walker = data[i++] << 24;
|
||||
walker_len = 8;
|
||||
}
|
||||
/* literal decoding */
|
||||
if (walker >= 0)
|
||||
{
|
||||
if (walker_len < 8)
|
||||
{
|
||||
if (i >= clen)
|
||||
return -1;
|
||||
walker |= (data[i++] & 0xff) << (24 - walker_len);
|
||||
walker_len += 8;
|
||||
}
|
||||
if (next_offset >= RDP_MPPC_DICT_SIZE)
|
||||
return -1;
|
||||
dict[next_offset++] = (uint8) (walker >> 24 | 0x80);
|
||||
walker <<= 8;
|
||||
walker_len -= 8;
|
||||
continue;
|
||||
}
|
||||
|
||||
/* decode offset */
|
||||
/* length pair */
|
||||
walker <<= 1;
|
||||
if (--walker_len < 2)
|
||||
{
|
||||
if (i >= clen)
|
||||
return -1;
|
||||
walker |= (data[i++] & 0xff) << (24 - walker_len);
|
||||
walker_len += 8;
|
||||
}
|
||||
/* offset decoding where offset len is:
|
||||
-63: 1111 followed by the lower 6 bits of the value
|
||||
64-319: 1110 followed by the lower 8 bits of the value ( value - 64 )
|
||||
320-8191: 110 followed by the lower 13 bits of the value ( value - 320 )
|
||||
*/
|
||||
switch (((uint32) walker) >> ((uint32) 30))
|
||||
{
|
||||
case 3: /* - 63 */
|
||||
if (walker_len < 8)
|
||||
{
|
||||
if (i >= clen)
|
||||
return -1;
|
||||
walker |= (data[i++] & 0xff) << (24 - walker_len);
|
||||
walker_len += 8;
|
||||
}
|
||||
walker <<= 2;
|
||||
match_off = ((uint32) walker) >> ((uint32) 26);
|
||||
walker <<= 6;
|
||||
walker_len -= 8;
|
||||
break;
|
||||
|
||||
case 2: /* 64 - 319 */
|
||||
for (; walker_len < 10; walker_len += 8)
|
||||
{
|
||||
if (i >= clen)
|
||||
return -1;
|
||||
walker |= (data[i++] & 0xff) << (24 - walker_len);
|
||||
}
|
||||
|
||||
walker <<= 2;
|
||||
match_off = (((uint32) walker) >> ((uint32) 24)) + 64;
|
||||
walker <<= 8;
|
||||
walker_len -= 10;
|
||||
break;
|
||||
|
||||
default: /* 320 - 8191 */
|
||||
for (; walker_len < 14; walker_len += 8)
|
||||
{
|
||||
if (i >= clen)
|
||||
return -1;
|
||||
walker |= (data[i++] & 0xff) << (24 - walker_len);
|
||||
}
|
||||
|
||||
match_off = (walker >> 18) + 320;
|
||||
walker <<= 14;
|
||||
walker_len -= 14;
|
||||
break;
|
||||
}
|
||||
if (walker_len == 0)
|
||||
{
|
||||
if (i >= clen)
|
||||
return -1;
|
||||
walker = data[i++] << 24;
|
||||
walker_len = 8;
|
||||
}
|
||||
|
||||
/* decode length of match */
|
||||
match_len = 0;
|
||||
if (walker >= 0)
|
||||
{ /* special case - length of 3 is in bit 0 */
|
||||
match_len = 3;
|
||||
walker <<= 1;
|
||||
walker_len--;
|
||||
}
|
||||
else
|
||||
{
|
||||
/* this is how it works len of:
|
||||
4-7: 10 followed by 2 bits of the value
|
||||
8-15: 110 followed by 3 bits of the value
|
||||
16-31: 1110 followed by 4 bits of the value
|
||||
32-63: .... and so forth
|
||||
64-127:
|
||||
128-255:
|
||||
256-511:
|
||||
512-1023:
|
||||
1024-2047:
|
||||
2048-4095:
|
||||
4096-8191:
|
||||
|
||||
i.e. 4097 is encoded as: 111111111110 000000000001
|
||||
meaning 4096 + 1...
|
||||
*/
|
||||
match_bits = 11; /* 11 bits of value at most */
|
||||
do
|
||||
{
|
||||
walker <<= 1;
|
||||
if (--walker_len == 0)
|
||||
{
|
||||
if (i >= clen)
|
||||
return -1;
|
||||
walker = data[i++] << 24;
|
||||
walker_len = 8;
|
||||
}
|
||||
if (walker >= 0)
|
||||
break;
|
||||
if (--match_bits == 0)
|
||||
{
|
||||
return -1;
|
||||
}
|
||||
}
|
||||
while (1);
|
||||
match_len = 13 - match_bits;
|
||||
walker <<= 1;
|
||||
if (--walker_len < match_len)
|
||||
{
|
||||
for (; walker_len < match_len; walker_len += 8)
|
||||
{
|
||||
if (i >= clen)
|
||||
{
|
||||
return -1;
|
||||
}
|
||||
walker |= (data[i++] & 0xff) << (24 - walker_len);
|
||||
}
|
||||
}
|
||||
|
||||
match_bits = match_len;
|
||||
match_len =
|
||||
walker >> 32 - match_bits & ~(-1 << match_bits) | 1 << match_bits;
|
||||
walker <<= match_bits;
|
||||
walker_len -= match_bits;
|
||||
}
|
||||
if (next_offset + match_len >= RDP_MPPC_DICT_SIZE)
|
||||
{
|
||||
return -1;
|
||||
}
|
||||
/* memory areas can overlap - meaning we can't use memXXX functions */
|
||||
k = next_offset - match_off & (RDP_MPPC_DICT_SIZE - 1);
|
||||
do
|
||||
{
|
||||
dict[next_offset++] = dict[k++];
|
||||
}
|
||||
while (--match_len != 0);
|
||||
}
|
||||
while (1);
|
||||
|
||||
/* store history offset */
|
||||
mppc_dict.roff = next_offset;
|
||||
|
||||
*roff = old_offset;
|
||||
*rlen = next_offset - old_offset;
|
||||
|
||||
return 0;
|
||||
}
|
Loading…
Reference in New Issue
Block a user