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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 5131 | clevermous | 1 | /* |
| 2 | Copyright (C) 1996-1997 Id Software, Inc. |
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| 3 | |||
| 4 | This program is free software; you can redistribute it and/or |
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| 5 | modify it under the terms of the GNU General Public License |
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| 6 | as published by the Free Software Foundation; either version 2 |
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| 7 | of the License, or (at your option) any later version. |
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| 8 | |||
| 9 | This program is distributed in the hope that it will be useful, |
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| 10 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. |
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| 12 | |||
| 13 | See the GNU General Public License for more details. |
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| 14 | |||
| 15 | You should have received a copy of the GNU General Public License |
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| 16 | along with this program; if not, write to the Free Software |
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| 17 | Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
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| 18 | |||
| 19 | */ |
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| 20 | /* crc.c */ |
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| 21 | |||
| 22 | #include "quakedef.h" |
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| 23 | #include "crc.h" |
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| 24 | |||
| 25 | // this is a 16 bit, non-reflected CRC using the polynomial 0x1021 |
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| 26 | // and the initial and final xor values shown below... in other words, the |
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| 27 | // CCITT standard CRC used by XMODEM |
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| 28 | |||
| 29 | #define CRC_INIT_VALUE 0xffff |
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| 30 | #define CRC_XOR_VALUE 0x0000 |
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| 31 | |||
| 32 | static unsigned short crctable[256] = |
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| 33 | { |
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| 34 | 0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7, |
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| 35 | 0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef, |
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| 36 | 0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6, |
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| 37 | 0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de, |
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| 38 | 0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485, |
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| 39 | 0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d, |
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| 40 | 0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4, |
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| 41 | 0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc, |
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| 42 | 0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823, |
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| 43 | 0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b, |
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| 44 | 0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12, |
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| 45 | 0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a, |
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| 46 | 0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41, |
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| 47 | 0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49, |
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| 48 | 0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70, |
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| 49 | 0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78, |
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| 50 | 0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f, |
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| 51 | 0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067, |
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| 52 | 0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e, |
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| 53 | 0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256, |
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| 54 | 0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d, |
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| 55 | 0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405, |
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| 56 | 0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c, |
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| 57 | 0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634, |
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| 58 | 0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab, |
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| 59 | 0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3, |
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| 60 | 0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a, |
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| 61 | 0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92, |
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| 62 | 0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9, |
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| 63 | 0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1, |
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| 64 | 0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8, |
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| 65 | 0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0 |
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| 66 | }; |
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| 67 | |||
| 68 | void CRC_Init(unsigned short *crcvalue) |
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| 69 | { |
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| 70 | *crcvalue = CRC_INIT_VALUE; |
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| 71 | } |
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| 72 | |||
| 73 | void CRC_ProcessByte(unsigned short *crcvalue, byte data) |
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| 74 | { |
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| 75 | *crcvalue = (*crcvalue << 8) ^ crctable[(*crcvalue >> 8) ^ data]; |
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| 76 | } |
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| 77 | |||
| 78 | unsigned short CRC_Value(unsigned short crcvalue) |
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| 79 | { |
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| 80 | return crcvalue ^ CRC_XOR_VALUE; |
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| 81 | } |