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 /* Table for CRC-7 (polynomial x^7 + x^3 + 1) */
  14 const u8 crc7_syndrome_table[256] = {
  15         0x00, 0x09, 0x12, 0x1b, 0x24, 0x2d, 0x36, 0x3f,
  16         0x48, 0x41, 0x5a, 0x53, 0x6c, 0x65, 0x7e, 0x77,
  17         0x19, 0x10, 0x0b, 0x02, 0x3d, 0x34, 0x2f, 0x26,
  18         0x51, 0x58, 0x43, 0x4a, 0x75, 0x7c, 0x67, 0x6e,
  19         0x32, 0x3b, 0x20, 0x29, 0x16, 0x1f, 0x04, 0x0d,
  20         0x7a, 0x73, 0x68, 0x61, 0x5e, 0x57, 0x4c, 0x45,
  21         0x2b, 0x22, 0x39, 0x30, 0x0f, 0x06, 0x1d, 0x14,
  22         0x63, 0x6a, 0x71, 0x78, 0x47, 0x4e, 0x55, 0x5c,
  23         0x64, 0x6d, 0x76, 0x7f, 0x40, 0x49, 0x52, 0x5b,
  24         0x2c, 0x25, 0x3e, 0x37, 0x08, 0x01, 0x1a, 0x13,
  25         0x7d, 0x74, 0x6f, 0x66, 0x59, 0x50, 0x4b, 0x42,
  26         0x35, 0x3c, 0x27, 0x2e, 0x11, 0x18, 0x03, 0x0a,
  27         0x56, 0x5f, 0x44, 0x4d, 0x72, 0x7b, 0x60, 0x69,
  28         0x1e, 0x17, 0x0c, 0x05, 0x3a, 0x33, 0x28, 0x21,
  29         0x4f, 0x46, 0x5d, 0x54, 0x6b, 0x62, 0x79, 0x70,
  30         0x07, 0x0e, 0x15, 0x1c, 0x23, 0x2a, 0x31, 0x38,
  31         0x41, 0x48, 0x53, 0x5a, 0x65, 0x6c, 0x77, 0x7e,
  32         0x09, 0x00, 0x1b, 0x12, 0x2d, 0x24, 0x3f, 0x36,
  33         0x58, 0x51, 0x4a, 0x43, 0x7c, 0x75, 0x6e, 0x67,
  34         0x10, 0x19, 0x02, 0x0b, 0x34, 0x3d, 0x26, 0x2f,
  35         0x73, 0x7a, 0x61, 0x68, 0x57, 0x5e, 0x45, 0x4c,
  36         0x3b, 0x32, 0x29, 0x20, 0x1f, 0x16, 0x0d, 0x04,
  37         0x6a, 0x63, 0x78, 0x71, 0x4e, 0x47, 0x5c, 0x55,
  38         0x22, 0x2b, 0x30, 0x39, 0x06, 0x0f, 0x14, 0x1d,
  39         0x25, 0x2c, 0x37, 0x3e, 0x01, 0x08, 0x13, 0x1a,
  40         0x6d, 0x64, 0x7f, 0x76, 0x49, 0x40, 0x5b, 0x52,
  41         0x3c, 0x35, 0x2e, 0x27, 0x18, 0x11, 0x0a, 0x03,
  42         0x74, 0x7d, 0x66, 0x6f, 0x50, 0x59, 0x42, 0x4b,
  43         0x17, 0x1e, 0x05, 0x0c, 0x33, 0x3a, 0x21, 0x28,
  44         0x5f, 0x56, 0x4d, 0x44, 0x7b, 0x72, 0x69, 0x60,
  45         0x0e, 0x07, 0x1c, 0x15, 0x2a, 0x23, 0x38, 0x31,
  46         0x46, 0x4f, 0x54, 0x5d, 0x62, 0x6b, 0x70, 0x79
  47 };
  48 EXPORT_SYMBOL(crc7_syndrome_table);
  49
  50 /**
  51  * crc7 - update the CRC7 for the data buffer
  52  * @crc:     previous CRC7 value
  53  * @buffer:  data pointer
  54  * @len:     number of bytes in the buffer
  55  * Context: any
  56  *
  57  * Returns the updated CRC7 value.
  58  */
  59 u8 crc7(u8 crc, const u8 *buffer, size_t len)
  60 {
  61         while (len--)
  62                 crc = crc7_byte(crc, *buffer++);
  63         return crc;
  64 }
  65 EXPORT_SYMBOL(crc7);
  66
  67 MODULE_DESCRIPTION("CRC7 calculations");
  68 MODULE_LICENSE("GPL");