1 /* 2 * Copied from Linux kernel crypto/crc32c.c 3 * Copyright (c) 2004 Cisco Systems, Inc. 4 * Copyright (c) 2008 Herbert Xu <herbert (at) gondor.apana.org.au> 5 * 6 * This program is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License as published by the Free 8 * Software Foundation; either version 2 of the License, or (at your option) 9 * any later version. 10 * 11 */ 12 13 /* 14 * This is the CRC-32C table 15 * Generated with: 16 * width = 32 bits 17 * poly = 0x1EDC6F41 18 * reflect input bytes = true 19 * reflect output bytes = true 20 */ 21 22 static u32 crc32c_table[256]; 23 24 /* 25 * Steps through buffer one byte at at time, calculates reflected 26 * crc using table. 27 */ 28 29 static inline u32 crc32c_le(u32 crc, const char *data, size_t length) 30 { 31 while (length--) 32 crc = crc32c_table[(u8)(crc ^ *data++)] ^ (crc >> 8); 33 34 return crc; 35 } 36 37 static inline void btrfs_init_crc32c(void) 38 { 39 int i, j; 40 u32 v; 41 const u32 poly = 0x82F63B78; /* Bit-reflected CRC32C polynomial */ 42 43 for (i = 0; i < 256; i++) { 44 v = i; 45 for (j = 0; j < 8; j++) { 46 v = (v >> 1) ^ ((v & 1) ? poly : 0); 47 } 48 crc32c_table[i] = v; 49 } 50 } 51
