gen_crc32table.c

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    1 #include <stdio.h>
    2 #include "crc32defs.h"
    3 #include <sys/types.h>
    4 
    5 #define ENTRIES_PER_LINE 4
    6 
    7 #define LE_TABLE_SIZE (1 << CRC_LE_BITS)
    8 #define BE_TABLE_SIZE (1 << CRC_BE_BITS)
    9 
   10 static u_int32_t crc32table_le[LE_TABLE_SIZE];
   11 static u_int32_t crc32table_be[BE_TABLE_SIZE];
   12 
   13 /**
   14  * crc32init_le() - allocate and initialize LE table data
   15  *
   16  * crc is the crc of the byte i; other entries are filled in based on the
   17  * fact that crctable[i^j] = crctable[i] ^ crctable[j].
   18  *
   19  */
   20 static void crc32init_le(void)
   21 {
   22         unsigned i, j;
   23         u_int32_t crc = 1;
   24 
   25         crc32table_le[0] = 0;
   26 
   27         for (i = 1 << (CRC_LE_BITS - 1); i; i >>= 1) {
   28                 crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0);
   29                 for (j = 0; j < LE_TABLE_SIZE; j += 2 * i)
   30                         crc32table_le[i + j] = crc ^ crc32table_le[j];
   31         }
   32 }
   33 
   34 /**
   35  * crc32init_be() - allocate and initialize BE table data
   36  */
   37 static void crc32init_be(void)
   38 {
   39         unsigned i, j;
   40         u_int32_t crc = 0x80000000;
   41 
   42         crc32table_be[0] = 0;
   43 
   44         for (i = 1; i < BE_TABLE_SIZE; i <<= 1) {
   45                 crc = (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE : 0);
   46                 for (j = 0; j < i; j++)
   47                         crc32table_be[i + j] = crc ^ crc32table_be[j];
   48         }
   49 }
   50 
   51 static void output_table(u_int32_t table[], int len, char *trans)
   52 {
   53         int i;
   54 
   55         for (i = 0; i < len - 1; i++) {
   56                 if (i % ENTRIES_PER_LINE == 0)
   57                         printf("\n");
   58                 printf("%s(0x%8.8xL), ", trans, table[i]);
   59         }
   60         printf("%s(0x%8.8xL)\n", trans, table[len - 1]);
   61 }
   62 
   63 int main(int argc, char** argv)
   64 {
   65         printf("/* this file is generated - do not edit */\n\n");
   66 
   67         if (CRC_LE_BITS > 1) {
   68                 crc32init_le();
   69                 printf("static const u32 crc32table_le[] = {");
   70                 output_table(crc32table_le, LE_TABLE_SIZE, "tole");
   71                 printf("};\n");
   72         }
   73 
   74         if (CRC_BE_BITS > 1) {
   75                 crc32init_be();
   76                 printf("static const u32 crc32table_be[] = {");
   77                 output_table(crc32table_be, BE_TABLE_SIZE, "tobe");
   78                 printf("};\n");
   79         }
   80 
   81         return 0;
   82 }

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FreeBSD/Linux Kernel Cross Reference sys/lib/gen_crc32table.c

FreeBSD/Linux Kernel Cross Reference
sys/lib/gen_crc32table.c