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Linux/lib/crc7.c

  1 /*
  2  *      crc7.c
  3  *
  4  * This source code is licensed under the GNU General Public License,
  5  * Version 2. See the file COPYING for more details.
  6  */
  7 
  8 #include <linux/types.h>
  9 #include <linux/module.h>
 10 #include <linux/crc7.h>
 11 
 12 
 13 /*
 14  * Table for CRC-7 (polynomial x^7 + x^3 + 1).
 15  * This is a big-endian CRC (msbit is highest power of x),
 16  * aligned so the msbit of the byte is the x^6 coefficient
 17  * and the lsbit is not used.
 18  */
 19 const u8 crc7_be_syndrome_table[256] = {
 20         0x00, 0x12, 0x24, 0x36, 0x48, 0x5a, 0x6c, 0x7e,
 21         0x90, 0x82, 0xb4, 0xa6, 0xd8, 0xca, 0xfc, 0xee,
 22         0x32, 0x20, 0x16, 0x04, 0x7a, 0x68, 0x5e, 0x4c,
 23         0xa2, 0xb0, 0x86, 0x94, 0xea, 0xf8, 0xce, 0xdc,
 24         0x64, 0x76, 0x40, 0x52, 0x2c, 0x3e, 0x08, 0x1a,
 25         0xf4, 0xe6, 0xd0, 0xc2, 0xbc, 0xae, 0x98, 0x8a,
 26         0x56, 0x44, 0x72, 0x60, 0x1e, 0x0c, 0x3a, 0x28,
 27         0xc6, 0xd4, 0xe2, 0xf0, 0x8e, 0x9c, 0xaa, 0xb8,
 28         0xc8, 0xda, 0xec, 0xfe, 0x80, 0x92, 0xa4, 0xb6,
 29         0x58, 0x4a, 0x7c, 0x6e, 0x10, 0x02, 0x34, 0x26,
 30         0xfa, 0xe8, 0xde, 0xcc, 0xb2, 0xa0, 0x96, 0x84,
 31         0x6a, 0x78, 0x4e, 0x5c, 0x22, 0x30, 0x06, 0x14,
 32         0xac, 0xbe, 0x88, 0x9a, 0xe4, 0xf6, 0xc0, 0xd2,
 33         0x3c, 0x2e, 0x18, 0x0a, 0x74, 0x66, 0x50, 0x42,
 34         0x9e, 0x8c, 0xba, 0xa8, 0xd6, 0xc4, 0xf2, 0xe0,
 35         0x0e, 0x1c, 0x2a, 0x38, 0x46, 0x54, 0x62, 0x70,
 36         0x82, 0x90, 0xa6, 0xb4, 0xca, 0xd8, 0xee, 0xfc,
 37         0x12, 0x00, 0x36, 0x24, 0x5a, 0x48, 0x7e, 0x6c,
 38         0xb0, 0xa2, 0x94, 0x86, 0xf8, 0xea, 0xdc, 0xce,
 39         0x20, 0x32, 0x04, 0x16, 0x68, 0x7a, 0x4c, 0x5e,
 40         0xe6, 0xf4, 0xc2, 0xd0, 0xae, 0xbc, 0x8a, 0x98,
 41         0x76, 0x64, 0x52, 0x40, 0x3e, 0x2c, 0x1a, 0x08,
 42         0xd4, 0xc6, 0xf0, 0xe2, 0x9c, 0x8e, 0xb8, 0xaa,
 43         0x44, 0x56, 0x60, 0x72, 0x0c, 0x1e, 0x28, 0x3a,
 44         0x4a, 0x58, 0x6e, 0x7c, 0x02, 0x10, 0x26, 0x34,
 45         0xda, 0xc8, 0xfe, 0xec, 0x92, 0x80, 0xb6, 0xa4,
 46         0x78, 0x6a, 0x5c, 0x4e, 0x30, 0x22, 0x14, 0x06,
 47         0xe8, 0xfa, 0xcc, 0xde, 0xa0, 0xb2, 0x84, 0x96,
 48         0x2e, 0x3c, 0x0a, 0x18, 0x66, 0x74, 0x42, 0x50,
 49         0xbe, 0xac, 0x9a, 0x88, 0xf6, 0xe4, 0xd2, 0xc0,
 50         0x1c, 0x0e, 0x38, 0x2a, 0x54, 0x46, 0x70, 0x62,
 51         0x8c, 0x9e, 0xa8, 0xba, 0xc4, 0xd6, 0xe0, 0xf2
 52 };
 53 EXPORT_SYMBOL(crc7_be_syndrome_table);
 54 
 55 /**
 56  * crc7 - update the CRC7 for the data buffer
 57  * @crc:     previous CRC7 value
 58  * @buffer:  data pointer
 59  * @len:     number of bytes in the buffer
 60  * Context: any
 61  *
 62  * Returns the updated CRC7 value.
 63  * The CRC7 is left-aligned in the byte (the lsbit is always 0), as that
 64  * makes the computation easier, and all callers want it in that form.
 65  *
 66  */
 67 u8 crc7_be(u8 crc, const u8 *buffer, size_t len)
 68 {
 69         while (len--)
 70                 crc = crc7_be_byte(crc, *buffer++);
 71         return crc;
 72 }
 73 EXPORT_SYMBOL(crc7_be);
 74 
 75 MODULE_DESCRIPTION("CRC7 calculations");
 76 MODULE_LICENSE("GPL");
 77 

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