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377 lines
8.5 KiB
C
377 lines
8.5 KiB
C
/* -*- c-basic-offset: 8 -*-
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rdesktop: A Remote Desktop Protocol client.
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Protocol services - RDP decompression
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Copyright (C) Matthew Chapman 1999-2005
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along
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with this program; if not, write to the Free Software Foundation, Inc.,
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51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include "precomp.h"
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/* mppc decompression */
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/* http://www.faqs.org/rfcs/rfc2118.html */
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/* Contacts: */
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/* hifn contact mentioned in the faq is */
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/* Robert Friend rfriend at hifn dot com */
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/* if you have questions regarding MPPC */
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/* our contact is */
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/* Guus Dhaeze GDhaeze at hifn dot com */
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/* Licensing: */
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/* decompression is alright as long as we */
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/* don't compress data */
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/* Algorithm: */
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/* as the rfc states the algorithm seems to */
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/* be LZ77 with a sliding buffer */
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/* that is empty at init. */
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/* the algorithm is called LZS and is */
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/* patented for another couple of years. */
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/* more information is available in */
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/* http://www.ietf.org/ietf/IPR/hifn-ipr-draft-friend-tls-lzs-compression.txt */
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RDPCOMP g_mppc_dict;
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int
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mppc_expand(uint8 * data, uint32 clen, uint8 ctype, uint32 * roff, uint32 * rlen)
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{
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int k, walker_len = 0, walker;
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uint32 i = 0;
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int next_offset, match_off;
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int match_len;
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int old_offset, match_bits;
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BOOL big = ctype & RDP_MPPC_BIG ? True : False;
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uint8 *dict = g_mppc_dict.hist;
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if ((ctype & RDP_MPPC_COMPRESSED) == 0)
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{
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*roff = 0;
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*rlen = clen;
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return 0;
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}
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if ((ctype & RDP_MPPC_RESET) != 0)
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{
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g_mppc_dict.roff = 0;
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}
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if ((ctype & RDP_MPPC_FLUSH) != 0)
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{
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memset(dict, 0, RDP_MPPC_DICT_SIZE);
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g_mppc_dict.roff = 0;
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}
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*roff = 0;
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*rlen = 0;
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walker = g_mppc_dict.roff;
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next_offset = walker;
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old_offset = next_offset;
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*roff = old_offset;
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if (clen == 0)
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return 0;
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clen += i;
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do
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{
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if (walker_len == 0)
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{
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if (i >= clen)
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break;
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walker = data[i++] << 24;
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walker_len = 8;
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}
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if (walker >= 0)
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{
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if (walker_len < 8)
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{
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if (i >= clen)
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{
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if (walker != 0)
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return -1;
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break;
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}
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walker |= (data[i++] & 0xff) << (24 - walker_len);
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walker_len += 8;
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}
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if (next_offset >= RDP_MPPC_DICT_SIZE)
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return -1;
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dict[next_offset++] = (((uint32) walker) >> ((uint32) 24));
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walker <<= 8;
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walker_len -= 8;
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continue;
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}
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walker <<= 1;
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/* fetch next 8-bits */
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if (--walker_len == 0)
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{
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if (i >= clen)
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return -1;
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walker = data[i++] << 24;
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walker_len = 8;
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}
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/* literal decoding */
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if (walker >= 0)
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{
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if (walker_len < 8)
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{
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if (i >= clen)
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return -1;
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walker |= (data[i++] & 0xff) << (24 - walker_len);
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walker_len += 8;
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}
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if (next_offset >= RDP_MPPC_DICT_SIZE)
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return -1;
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dict[next_offset++] = (uint8) (walker >> 24 | 0x80);
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walker <<= 8;
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walker_len -= 8;
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continue;
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}
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/* decode offset */
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/* length pair */
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walker <<= 1;
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if (--walker_len < (big ? 3 : 2))
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{
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if (i >= clen)
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return -1;
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walker |= (data[i++] & 0xff) << (24 - walker_len);
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walker_len += 8;
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}
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if (big)
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{
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/* offset decoding where offset len is:
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-63: 11111 followed by the lower 6 bits of the value
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64-319: 11110 followed by the lower 8 bits of the value ( value - 64 )
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320-2367: 1110 followed by lower 11 bits of the value ( value - 320 )
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2368-65535: 110 followed by lower 16 bits of the value ( value - 2368 )
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*/
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switch (((uint32) walker) >> ((uint32) 29))
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{
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case 7: /* - 63 */
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for (; walker_len < 9; walker_len += 8)
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{
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if (i >= clen)
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return -1;
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walker |= (data[i++] & 0xff) << (24 - walker_len);
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}
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walker <<= 3;
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match_off = ((uint32) walker) >> ((uint32) 26);
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walker <<= 6;
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walker_len -= 9;
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break;
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case 6: /* 64 - 319 */
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for (; walker_len < 11; walker_len += 8)
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{
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if (i >= clen)
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return -1;
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walker |= (data[i++] & 0xff) << (24 - walker_len);
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}
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walker <<= 3;
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match_off = (((uint32) walker) >> ((uint32) 24)) + 64;
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walker <<= 8;
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walker_len -= 11;
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break;
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case 5:
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case 4: /* 320 - 2367 */
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for (; walker_len < 13; walker_len += 8)
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{
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if (i >= clen)
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return -1;
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walker |= (data[i++] & 0xff) << (24 - walker_len);
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}
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walker <<= 2;
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match_off = (((uint32) walker) >> ((uint32) 21)) + 320;
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walker <<= 11;
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walker_len -= 13;
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break;
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default: /* 2368 - 65535 */
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for (; walker_len < 17; walker_len += 8)
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{
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if (i >= clen)
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return -1;
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walker |= (data[i++] & 0xff) << (24 - walker_len);
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}
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walker <<= 1;
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match_off = (((uint32) walker) >> ((uint32) 16)) + 2368;
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walker <<= 16;
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walker_len -= 17;
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break;
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}
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}
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else
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{
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/* offset decoding where offset len is:
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-63: 1111 followed by the lower 6 bits of the value
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64-319: 1110 followed by the lower 8 bits of the value ( value - 64 )
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320-8191: 110 followed by the lower 13 bits of the value ( value - 320 )
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*/
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switch (((uint32) walker) >> ((uint32) 30))
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{
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case 3: /* - 63 */
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if (walker_len < 8)
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{
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if (i >= clen)
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return -1;
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walker |= (data[i++] & 0xff) << (24 - walker_len);
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walker_len += 8;
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}
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walker <<= 2;
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match_off = ((uint32) walker) >> ((uint32) 26);
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walker <<= 6;
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walker_len -= 8;
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break;
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case 2: /* 64 - 319 */
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for (; walker_len < 10; walker_len += 8)
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{
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if (i >= clen)
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return -1;
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walker |= (data[i++] & 0xff) << (24 - walker_len);
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}
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walker <<= 2;
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match_off = (((uint32) walker) >> ((uint32) 24)) + 64;
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walker <<= 8;
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walker_len -= 10;
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break;
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default: /* 320 - 8191 */
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for (; walker_len < 14; walker_len += 8)
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{
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if (i >= clen)
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return -1;
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walker |= (data[i++] & 0xff) << (24 - walker_len);
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}
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match_off = (walker >> 18) + 320;
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walker <<= 14;
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walker_len -= 14;
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break;
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}
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}
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if (walker_len == 0)
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{
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if (i >= clen)
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return -1;
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walker = data[i++] << 24;
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walker_len = 8;
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}
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/* decode length of match */
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match_len = 0;
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if (walker >= 0)
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{ /* special case - length of 3 is in bit 0 */
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match_len = 3;
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walker <<= 1;
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walker_len--;
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}
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else
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{
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/* this is how it works len of:
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4-7: 10 followed by 2 bits of the value
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8-15: 110 followed by 3 bits of the value
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16-31: 1110 followed by 4 bits of the value
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32-63: .... and so forth
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64-127:
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128-255:
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256-511:
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512-1023:
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1024-2047:
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2048-4095:
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4096-8191:
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i.e. 4097 is encoded as: 111111111110 000000000001
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meaning 4096 + 1...
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*/
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match_bits = big ? 14 : 11; /* 11 or 14 bits of value at most */
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do
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{
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walker <<= 1;
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if (--walker_len == 0)
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{
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if (i >= clen)
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return -1;
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walker = data[i++] << 24;
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walker_len = 8;
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}
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if (walker >= 0)
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break;
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if (--match_bits == 0)
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{
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return -1;
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}
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}
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while (1);
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match_len = (big ? 16 : 13) - match_bits;
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walker <<= 1;
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if (--walker_len < match_len)
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{
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for (; walker_len < match_len; walker_len += 8)
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{
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if (i >= clen)
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{
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return -1;
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}
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walker |= (data[i++] & 0xff) << (24 - walker_len);
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}
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}
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match_bits = match_len;
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match_len =
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((walker >> (32 - match_bits)) & (~(-1 << match_bits))) | (1 <<
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match_bits);
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walker <<= match_bits;
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walker_len -= match_bits;
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}
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if (next_offset + match_len >= RDP_MPPC_DICT_SIZE)
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{
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return -1;
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}
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/* memory areas can overlap - meaning we can't use memXXX functions */
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k = (next_offset - match_off) & (big ? 65535 : 8191);
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do
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{
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dict[next_offset++] = dict[k++];
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}
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while (--match_len != 0);
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}
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while (1);
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/* store history offset */
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g_mppc_dict.roff = next_offset;
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*roff = old_offset;
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*rlen = next_offset - old_offset;
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return 0;
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}
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