1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License, Version 1.0 only 6 * (the "License"). You may not use this file except in compliance 7 * with the License. 8 * 9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 10 * or http://www.opensolaris.org/os/licensing. 11 * See the License for the specific language governing permissions 12 * and limitations under the License. 13 * 14 * When distributing Covered Code, include this CDDL HEADER in each 15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 16 * If applicable, add the following below this CDDL HEADER, with the 17 * fields enclosed by brackets "[]" replaced with your own identifying 18 * information: Portions Copyright [yyyy] [name of copyright owner] 19 * 20 * CDDL HEADER END 21 */ 22 /* 23 * Copyright 2002 Sun Microsystems, Inc. All rights reserved. 24 * Use is subject to license terms. 25 */ 26 27 #ifndef _SYS_CRC32_H 28 #define _SYS_CRC32_H 29 30 /* 31 * CRC32, the 32-bit Cyclic Redundancy Check, is a well-known way to 32 * generate checksums or hashes. Extensive literature on the theory 33 * behind CRC is available on the web; we won't recapitulate it here. 34 * We must, however, cover a few basics to explain the services we're 35 * providing. 36 * 37 * A CRC function is defined by two parameters: an initial value and a 38 * 32-bit integer that encodes its generating polynomial (explained later). 39 * Given these values, the CRC of any bitstream is defined as follows: 40 * 41 * crc = CRC32_INITIAL; 42 * foreach (bit of data) 43 * if (bit == (crc & 1)) 44 * crc = (crc >> 1); 45 * else 46 * crc = (crc >> 1) ^ CRC32_POLY; 47 * 48 * That's it. The algorithm is both simple and surprisingly powerful: 49 * CRC32 has been proven to detect all single-bit errors, all double-bit 50 * errors, and all burst errors up to 32 bits long. 51 * 52 * The most common values for the CRC parameters are: 53 * 54 * CRC32_INITIAL: 0 or -1 55 * CRC32_POLY 0xEDB88320 56 * 57 * There is no particular constraint on the initial value; any will yield a 58 * valid CRC. (OK, then why not always use zero? Because CRC was originally 59 * designed for serial transmission, in which one common form of error 60 * was a burst of zeroes. Note that if crc == 0, and we fold in a zero bit, 61 * we still have crc == 0. Therefore, if the CRC's initial value is zero, 62 * an arbitrarily long run of zeroes can be prepended to a packet without 63 * being detected.) 64 * 65 * The constraint on the polynomial is that it must be of degree 32 66 * and must be primitive in the Galois field of polynomials modulo 2. 67 * Any such polynomial will yield a valid CRC. There's no particular 68 * advantage to one such polynomial over another, so the world has 69 * largely standardized on a particular one, 0xEDB88320. [The nth bit 70 * of this integer is the coefficient of x^n; the coefficient of x^32 71 * is implicitly 1.] 72 * 73 * Of course, we rarely process data bitwise in software. When processing 74 * data bytewise, the following calculation is equivalent to the bitwise one: 75 * 76 * crc = CRC32_INITIAL; 77 * foreach (byte of data) 78 * for (crc ^= byte, i = 8; i > 0; i--) 79 * crc = (crc >> 1) ^ (-(crc & 1) & CRC32_POLY); 80 * 81 * Note that we still have a bitwise loop in there. We can avoid this 82 * by precomputing the CRC of each possible byte [i.e. 0-255] using the 83 * algorithm above and storing the results in a lookup table. Given 84 * such a table, the CRC can be computed quite efficiently as follows: 85 * 86 * crc = CRC32_INITIAL; 87 * foreach (byte of data) 88 * crc = (crc >> 8) ^ crc32_table[(crc ^ byte) & 0xFF]; 89 * 90 * The macros below support this form of CRC computation. 91 * 92 * We also define a pre-computed crc32_table[] for the polynomial 0xEDB88320. 93 * This is the only CRC polynomial we actually use in Solaris. 94 */ 95 96 #ifdef __cplusplus 97 extern "C" { 98 #endif 99 100 #include <sys/types.h> 101 102 /* 103 * Initialize a CRC table [256 uint32_t's] with the given polynomial. 104 */ 105 #define CRC32_INIT(table, poly) \ 106 { \ 107 uint32_t Xi, Xj, *Xt; \ 108 for (Xi = 0; Xi < 256; Xi++) \ 109 for (Xt = (table) + Xi, *Xt = Xi, Xj = 8; Xj > 0; Xj--) \ 110 *Xt = (*Xt >> 1) ^ (-(*Xt & 1) & (poly)); \ 111 } 112 113 /* 114 * Compute a 32-bit CRC using the specified starting value and table. 115 * Typical usage: CRC32(crc, buf, size, -1U, crc32_table). 116 */ 117 #define CRC32(crc, buf, size, start, table) \ 118 { \ 119 uint32_t Xcrc = start; \ 120 const uint8_t *Xcp = (const uint8_t *)(buf); \ 121 const uint8_t *Xcpend = Xcp + (size); \ 122 while (Xcp < Xcpend) \ 123 Xcrc = (Xcrc >> 8) ^ (table)[(Xcrc ^ *Xcp++) & 0xFF]; \ 124 crc = Xcrc; \ 125 } 126 127 /* 128 * As above, but operate on a null-terminated string instead of an 129 * array of known size. Computes both the crc and the string length. 130 * Typical usage: CRC32_STRING(crc, len, str, -1U, crc32_table). 131 */ 132 #define CRC32_STRING(crc, len, str, start, table) \ 133 { \ 134 uint32_t Xcrc = start; \ 135 const uint8_t *Xcp; \ 136 uint8_t Xc; \ 137 for (Xcp = (const uint8_t *)(str); (Xc = *Xcp) != 0; Xcp++) \ 138 Xcrc = (Xcrc >> 8) ^ (table)[(Xcrc ^ Xc) & 0xFF]; \ 139 (crc) = Xcrc; \ 140 (len) = Xcp - (const uint8_t *)(str); \ 141 } 142 143 /* 144 * The polynomial we generally use in Solaris. 145 */ 146 #define CRC32_POLY 0xEDB88320U 147 148 /* 149 * The pre-computed table values for CRC32_POLY. 150 */ 151 #define CRC32_TABLE \ 152 0x00000000U, 0x77073096U, 0xEE0E612CU, 0x990951BAU, \ 153 0x076DC419U, 0x706AF48FU, 0xE963A535U, 0x9E6495A3U, \ 154 0x0EDB8832U, 0x79DCB8A4U, 0xE0D5E91EU, 0x97D2D988U, \ 155 0x09B64C2BU, 0x7EB17CBDU, 0xE7B82D07U, 0x90BF1D91U, \ 156 0x1DB71064U, 0x6AB020F2U, 0xF3B97148U, 0x84BE41DEU, \ 157 0x1ADAD47DU, 0x6DDDE4EBU, 0xF4D4B551U, 0x83D385C7U, \ 158 0x136C9856U, 0x646BA8C0U, 0xFD62F97AU, 0x8A65C9ECU, \ 159 0x14015C4FU, 0x63066CD9U, 0xFA0F3D63U, 0x8D080DF5U, \ 160 0x3B6E20C8U, 0x4C69105EU, 0xD56041E4U, 0xA2677172U, \ 161 0x3C03E4D1U, 0x4B04D447U, 0xD20D85FDU, 0xA50AB56BU, \ 162 0x35B5A8FAU, 0x42B2986CU, 0xDBBBC9D6U, 0xACBCF940U, \ 163 0x32D86CE3U, 0x45DF5C75U, 0xDCD60DCFU, 0xABD13D59U, \ 164 0x26D930ACU, 0x51DE003AU, 0xC8D75180U, 0xBFD06116U, \ 165 0x21B4F4B5U, 0x56B3C423U, 0xCFBA9599U, 0xB8BDA50FU, \ 166 0x2802B89EU, 0x5F058808U, 0xC60CD9B2U, 0xB10BE924U, \ 167 0x2F6F7C87U, 0x58684C11U, 0xC1611DABU, 0xB6662D3DU, \ 168 0x76DC4190U, 0x01DB7106U, 0x98D220BCU, 0xEFD5102AU, \ 169 0x71B18589U, 0x06B6B51FU, 0x9FBFE4A5U, 0xE8B8D433U, \ 170 0x7807C9A2U, 0x0F00F934U, 0x9609A88EU, 0xE10E9818U, \ 171 0x7F6A0DBBU, 0x086D3D2DU, 0x91646C97U, 0xE6635C01U, \ 172 0x6B6B51F4U, 0x1C6C6162U, 0x856530D8U, 0xF262004EU, \ 173 0x6C0695EDU, 0x1B01A57BU, 0x8208F4C1U, 0xF50FC457U, \ 174 0x65B0D9C6U, 0x12B7E950U, 0x8BBEB8EAU, 0xFCB9887CU, \ 175 0x62DD1DDFU, 0x15DA2D49U, 0x8CD37CF3U, 0xFBD44C65U, \ 176 0x4DB26158U, 0x3AB551CEU, 0xA3BC0074U, 0xD4BB30E2U, \ 177 0x4ADFA541U, 0x3DD895D7U, 0xA4D1C46DU, 0xD3D6F4FBU, \ 178 0x4369E96AU, 0x346ED9FCU, 0xAD678846U, 0xDA60B8D0U, \ 179 0x44042D73U, 0x33031DE5U, 0xAA0A4C5FU, 0xDD0D7CC9U, \ 180 0x5005713CU, 0x270241AAU, 0xBE0B1010U, 0xC90C2086U, \ 181 0x5768B525U, 0x206F85B3U, 0xB966D409U, 0xCE61E49FU, \ 182 0x5EDEF90EU, 0x29D9C998U, 0xB0D09822U, 0xC7D7A8B4U, \ 183 0x59B33D17U, 0x2EB40D81U, 0xB7BD5C3BU, 0xC0BA6CADU, \ 184 0xEDB88320U, 0x9ABFB3B6U, 0x03B6E20CU, 0x74B1D29AU, \ 185 0xEAD54739U, 0x9DD277AFU, 0x04DB2615U, 0x73DC1683U, \ 186 0xE3630B12U, 0x94643B84U, 0x0D6D6A3EU, 0x7A6A5AA8U, \ 187 0xE40ECF0BU, 0x9309FF9DU, 0x0A00AE27U, 0x7D079EB1U, \ 188 0xF00F9344U, 0x8708A3D2U, 0x1E01F268U, 0x6906C2FEU, \ 189 0xF762575DU, 0x806567CBU, 0x196C3671U, 0x6E6B06E7U, \ 190 0xFED41B76U, 0x89D32BE0U, 0x10DA7A5AU, 0x67DD4ACCU, \ 191 0xF9B9DF6FU, 0x8EBEEFF9U, 0x17B7BE43U, 0x60B08ED5U, \ 192 0xD6D6A3E8U, 0xA1D1937EU, 0x38D8C2C4U, 0x4FDFF252U, \ 193 0xD1BB67F1U, 0xA6BC5767U, 0x3FB506DDU, 0x48B2364BU, \ 194 0xD80D2BDAU, 0xAF0A1B4CU, 0x36034AF6U, 0x41047A60U, \ 195 0xDF60EFC3U, 0xA867DF55U, 0x316E8EEFU, 0x4669BE79U, \ 196 0xCB61B38CU, 0xBC66831AU, 0x256FD2A0U, 0x5268E236U, \ 197 0xCC0C7795U, 0xBB0B4703U, 0x220216B9U, 0x5505262FU, \ 198 0xC5BA3BBEU, 0xB2BD0B28U, 0x2BB45A92U, 0x5CB36A04U, \ 199 0xC2D7FFA7U, 0xB5D0CF31U, 0x2CD99E8BU, 0x5BDEAE1DU, \ 200 0x9B64C2B0U, 0xEC63F226U, 0x756AA39CU, 0x026D930AU, \ 201 0x9C0906A9U, 0xEB0E363FU, 0x72076785U, 0x05005713U, \ 202 0x95BF4A82U, 0xE2B87A14U, 0x7BB12BAEU, 0x0CB61B38U, \ 203 0x92D28E9BU, 0xE5D5BE0DU, 0x7CDCEFB7U, 0x0BDBDF21U, \ 204 0x86D3D2D4U, 0xF1D4E242U, 0x68DDB3F8U, 0x1FDA836EU, \ 205 0x81BE16CDU, 0xF6B9265BU, 0x6FB077E1U, 0x18B74777U, \ 206 0x88085AE6U, 0xFF0F6A70U, 0x66063BCAU, 0x11010B5CU, \ 207 0x8F659EFFU, 0xF862AE69U, 0x616BFFD3U, 0x166CCF45U, \ 208 0xA00AE278U, 0xD70DD2EEU, 0x4E048354U, 0x3903B3C2U, \ 209 0xA7672661U, 0xD06016F7U, 0x4969474DU, 0x3E6E77DBU, \ 210 0xAED16A4AU, 0xD9D65ADCU, 0x40DF0B66U, 0x37D83BF0U, \ 211 0xA9BCAE53U, 0xDEBB9EC5U, 0x47B2CF7FU, 0x30B5FFE9U, \ 212 0xBDBDF21CU, 0xCABAC28AU, 0x53B39330U, 0x24B4A3A6U, \ 213 0xBAD03605U, 0xCDD70693U, 0x54DE5729U, 0x23D967BFU, \ 214 0xB3667A2EU, 0xC4614AB8U, 0x5D681B02U, 0x2A6F2B94U, \ 215 0xB40BBE37U, 0xC30C8EA1U, 0x5A05DF1BU, 0x2D02EF8DU 216 217 #ifdef _KERNEL 218 219 /* 220 * The kernel's pre-computed table for CRC32_POLY. 221 */ 222 extern const uint32_t crc32_table[256]; 223 224 #endif /* _KERNEL */ 225 226 #ifdef __cplusplus 227 } 228 #endif 229 230 #endif /* _SYS_CRC32_H */ 231