/[rdesktop]/sourceforge.net/trunk/rdesktop/mppc.c
This is repository of my old source code which isn't updated any more. Go to git.rot13.org for current projects!
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revision 684 by n-ki, Tue Apr 27 13:05:32 2004 UTC revision 712 by jsorg71, Wed Jun 16 00:56:36 2004 UTC
# Line 1  Line 1 
1    /* -*- c-basic-offset: 8 -*-
2       rdesktop: A Remote Desktop Protocol client.
3       Protocol services - RDP decompression
4       Copyright (C) Matthew Chapman 1999-2004
5    
6       This program is free software; you can redistribute it and/or modify
7       it under the terms of the GNU General Public License as published by
8       the Free Software Foundation; either version 2 of the License, or
9       (at your option) any later version.
10    
11       This program is distributed in the hope that it will be useful,
12       but WITHOUT ANY WARRANTY; without even the implied warranty of
13       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14       GNU General Public License for more details.
15    
16       You should have received a copy of the GNU General Public License
17       along with this program; if not, write to the Free Software
18       Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
19    */
20    
21  #include <stdio.h>  #include <stdio.h>
22  #include <string.h>  #include <string.h>
23    
24  #include "rdesktop.h"  #include "rdesktop.h"
25    
26  /* mppc-like??? decompression               */  /* mppc decompression                       */
27  /* http://www.faqs.org/rfcs/rfc2118.html    */  /* http://www.faqs.org/rfcs/rfc2118.html    */
28    
29  /* TODO: research the below statements      */  /* Contacts:                                */
30    
31    /* hifn contact mentioned in the faq is     */
32    /* Robert Friend rfriend at hifn dot com    */
33    
34    /* if you have questions regarding MPPC     */
35    /* our contact is                           */
36    /* Guus Dhaeze  GDhaeze at hifn dot com     */
37    
38    /* Licensing:                               */
39    
40    /* decompression is alright as long as we   */
41    /* don't compress data                      */
42    
43  /* there exists one or more patents         */  /* Algorithm: */
 /* related to compression algorithms        */  
44    
45  /* since we are only decompressing I        */  /* as the rfc states the algorithm seems to */
46  /* think the end-user is safe.              */  /* be LZ77 with a sliding buffer            */
47    /* that is empty at init.                   */
48    
49  /* even if that isn't true, aren't you      */  /* the algorithm is called LZS and is       */
50  /* already paying royalties                 */  /* patented for another couple of years.    */
 /* through the CAL licenses?                */  
51    
52  /* the dictionary is empty when init. like  */  /* more information is available in         */
53  /* LZ78,  which is not patented             */  /* http://www.ietf.org/ietf/IPR/hifn-ipr-draft-friend-tls-lzs-compression.txt */
54    
55    
56  RDPCOMP mppc_dict;  RDPCOMP g_mppc_dict;
57    
58  int  int
59  mppc_expand(uint8 * data, uint32 clen, uint8 ctype, uint32 * roff, uint32 * rlen)  mppc_expand(uint8 * data, uint32 clen, uint8 ctype, uint32 * roff, uint32 * rlen)
60  {  {
61          int k, walker_len = 0, walker;          int k, walker_len = 0, walker;
62          int i = 0;          uint32 i = 0;
63          int next_offset, match_off;          int next_offset, match_off;
64          int match_len;          int match_len;
65          int old_offset, match_bits;          int old_offset, match_bits;
66    
67          signed char *dict = &(mppc_dict.hist);          uint8 *dict = g_mppc_dict.hist;
68    
69          if ((ctype & RDP_MPPC_COMPRESSED) == 0)          if ((ctype & RDP_MPPC_COMPRESSED) == 0)
70          {          {
# Line 44  mppc_expand(uint8 * data, uint32 clen, u Line 75  mppc_expand(uint8 * data, uint32 clen, u
75    
76          if ((ctype & RDP_MPPC_RESET) != 0)          if ((ctype & RDP_MPPC_RESET) != 0)
77          {          {
78                  mppc_dict.roff = 0;                  g_mppc_dict.roff = 0;
79          }          }
80    
81          if ((ctype & RDP_MPPC_FLUSH) != 0)          if ((ctype & RDP_MPPC_FLUSH) != 0)
82          {          {
83                  memset(dict, 0, RDP_MPPC_DICT_SIZE);                  memset(dict, 0, RDP_MPPC_DICT_SIZE);
84                  mppc_dict.roff = 0;                  g_mppc_dict.roff = 0;
85          }          }
86    
87          *roff = 0;          *roff = 0;
88          *rlen = 0;          *rlen = 0;
89    
90          walker = mppc_dict.roff;          walker = g_mppc_dict.roff;
91    
92          next_offset = walker;          next_offset = walker;
93          old_offset = next_offset;          old_offset = next_offset;
# Line 248  mppc_expand(uint8 * data, uint32 clen, u Line 279  mppc_expand(uint8 * data, uint32 clen, u
279    
280                          match_bits = match_len;                          match_bits = match_len;
281                          match_len =                          match_len =
282                                  walker >> 32 - match_bits & ~(-1 << match_bits) | 1 << match_bits;                                  ((walker >> (32 - match_bits)) & (~(-1 << match_bits))) | (1 << match_bits);
283                          walker <<= match_bits;                          walker <<= match_bits;
284                          walker_len -= match_bits;                          walker_len -= match_bits;
285                  }                  }
# Line 257  mppc_expand(uint8 * data, uint32 clen, u Line 288  mppc_expand(uint8 * data, uint32 clen, u
288                          return -1;                          return -1;
289                  }                  }
290                  /* memory areas can overlap - meaning we can't use memXXX functions */                  /* memory areas can overlap - meaning we can't use memXXX functions */
291                  k = next_offset - match_off & (RDP_MPPC_DICT_SIZE - 1);                  k = (next_offset - match_off) & (RDP_MPPC_DICT_SIZE - 1);
292                  do                  do
293                  {                  {
294                          dict[next_offset++] = dict[k++];                          dict[next_offset++] = dict[k++];
# Line 267  mppc_expand(uint8 * data, uint32 clen, u Line 298  mppc_expand(uint8 * data, uint32 clen, u
298          while (1);          while (1);
299    
300          /* store history offset */          /* store history offset */
301          mppc_dict.roff = next_offset;          g_mppc_dict.roff = next_offset;
302    
303          *roff = old_offset;          *roff = old_offset;
304          *rlen = next_offset - old_offset;          *rlen = next_offset - old_offset;
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