1 /* 2 * gen_crc32table.c --- Generate CRC32 tables. 3 * 4 * Copyright (C) 2008 Theodore Ts'o. 5 * 6 * %Begin-Header% 7 * This file may be redistributed under the terms of the GNU Public 8 * License. 9 * %End-Header% 10 */ 11 12 #include <stdio.h> 13 #include "crc32defs.h" 14 #include <inttypes.h> 15 16 #define ENTRIES_PER_LINE 4 17 18 #define LE_TABLE_SIZE (1 << CRC_LE_BITS) 19 #define BE_TABLE_SIZE (1 << CRC_BE_BITS) 20 21 static uint32_t crc32table_le[LE_TABLE_SIZE]; 22 static uint32_t crc32table_be[BE_TABLE_SIZE]; 23 24 /** 25 * crc32init_le() - allocate and initialize LE table data 26 * 27 * crc is the crc of the byte i; other entries are filled in based on the 28 * fact that crctable[i^j] = crctable[i] ^ crctable[j]. 29 * 30 */ 31 static void crc32init_le(void) 32 { 33 unsigned i, j; 34 uint32_t crc = 1; 35 36 crc32table_le[0] = 0; 37 38 for (i = 1 << (CRC_LE_BITS - 1); i; i >>= 1) { 39 crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0); 40 for (j = 0; j < LE_TABLE_SIZE; j += 2 * i) 41 crc32table_le[i + j] = crc ^ crc32table_le[j]; 42 } 43 } 44 45 /** 46 * crc32init_be() - allocate and initialize BE table data 47 */ 48 static void crc32init_be(void) 49 { 50 unsigned i, j; 51 uint32_t crc = 0x80000000; 52 53 crc32table_be[0] = 0; 54 55 for (i = 1; i < BE_TABLE_SIZE; i <<= 1) { 56 crc = (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE : 0); 57 for (j = 0; j < i; j++) 58 crc32table_be[i + j] = crc ^ crc32table_be[j]; 59 } 60 } 61 62 static void output_table(uint32_t table[], int len, const char *trans) 63 { 64 int i; 65 66 for (i = 0; i < len - 1; i++) { 67 if (i % ENTRIES_PER_LINE == 0) 68 printf("\n"); 69 printf("%s(0x%8.8xL), ", trans, table[i]); 70 } 71 printf("%s(0x%8.8xL)\n", trans, table[len - 1]); 72 } 73 74 #ifdef __GNUC__ 75 #define ATTR(x) __attribute__(x) 76 #else 77 #define ATTR(x) 78 #endif 79 80 int main(int argc ATTR((unused)), char** argv ATTR((unused))) 81 { 82 printf("/* this file is generated - do not edit */\n\n"); 83 84 printf("#ifdef UNITTEST\n"); 85 if (CRC_LE_BITS > 1) { 86 crc32init_le(); 87 printf("static const __u32 crc32table_le[] = {"); 88 output_table(crc32table_le, LE_TABLE_SIZE, "tole"); 89 printf("};\n"); 90 } 91 printf("#endif /* UNITTEST */\n"); 92 93 if (CRC_BE_BITS > 1) { 94 crc32init_be(); 95 printf("static const __u32 crc32table_be[] = {"); 96 output_table(crc32table_be, BE_TABLE_SIZE, "tobe"); 97 printf("};\n"); 98 } 99 100 return 0; 101 } 102
