2004-04-27 15:05:32 +02:00
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#include <stdio.h>
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#include <string.h>
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#include "rdesktop.h"
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2004-04-30 08:18:08 +02:00
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/* mppc decompression */
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2004-04-27 15:05:32 +02:00
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/* http://www.faqs.org/rfcs/rfc2118.html */
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/* TODO: research the below statements */
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/* there exists one or more patents */
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/* related to compression algorithms */
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/* since we are only decompressing I */
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/* think the end-user is safe. */
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/* even if that isn't true, aren't you */
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/* already paying royalties */
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/* through the CAL licenses? */
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2004-04-30 08:18:08 +02:00
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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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2004-04-27 15:05:32 +02:00
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2004-04-30 08:18:08 +02:00
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/* as of my limited knowledge these patents */
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/* has expired. */
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2004-04-27 15:05:32 +02:00
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2004-04-30 08:18:08 +02:00
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RDPCOMP g_mppc_dict;
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2004-04-27 15:05:32 +02:00
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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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int 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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2004-04-30 08:18:08 +02:00
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signed char *dict = &(g_mppc_dict.hist);
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2004-04-27 15:05:32 +02:00
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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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2004-04-30 08:18:08 +02:00
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g_mppc_dict.roff = 0;
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2004-04-27 15:05:32 +02:00
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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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2004-04-30 08:18:08 +02:00
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g_mppc_dict.roff = 0;
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2004-04-27 15:05:32 +02:00
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}
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*roff = 0;
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*rlen = 0;
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2004-04-30 08:18:08 +02:00
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walker = g_mppc_dict.roff;
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2004-04-27 15:05:32 +02:00
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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 < 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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/* 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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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 = 11; /* 11 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 = 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 << 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 & (RDP_MPPC_DICT_SIZE - 1);
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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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2004-04-30 08:18:08 +02:00
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g_mppc_dict.roff = next_offset;
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2004-04-27 15:05:32 +02:00
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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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