root/lib/gen_crc32table.c

DEFINITIONS

1. crc32init_le
2. crc32init_be
3. output_table
4. main

#include <stdio.h>
#include "crc32defs.h"
#include <inttypes.h>

#define ENTRIES_PER_LINE 4

#define LE_TABLE_SIZE (1 << CRC_LE_BITS)
#define BE_TABLE_SIZE (1 << CRC_BE_BITS)

static uint32_t crc32table_le[LE_TABLE_SIZE];
static uint32_t crc32table_be[BE_TABLE_SIZE];

/**
 * crc32init_le() - allocate and initialize LE table data
 *
 * crc is the crc of the byte i; other entries are filled in based on the
 * fact that crctable[i^j] = crctable[i] ^ crctable[j].
 *
 */
static void crc32init_le(void)
{
        unsigned i, j;
        uint32_t crc = 1;

        crc32table_le[0] = 0;

        for (i = 1 << (CRC_LE_BITS - 1); i; i >>= 1) {
                crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0);
                for (j = 0; j < LE_TABLE_SIZE; j += 2 * i)
                        crc32table_le[i + j] = crc ^ crc32table_le[j];
        }
}

/**
 * crc32init_be() - allocate and initialize BE table data
 */
static void crc32init_be(void)
{
        unsigned i, j;
        uint32_t crc = 0x80000000;

        crc32table_be[0] = 0;

        for (i = 1; i < BE_TABLE_SIZE; i <<= 1) {
                crc = (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE : 0);
                for (j = 0; j < i; j++)
                        crc32table_be[i + j] = crc ^ crc32table_be[j];
        }
}

static void output_table(uint32_t table[], int len, char *trans)
{
        int i;

        for (i = 0; i < len - 1; i++) {
                if (i % ENTRIES_PER_LINE == 0)
                        printf("\n");
                printf("%s(0x%8.8xL), ", trans, table[i]);
        }
        printf("%s(0x%8.8xL)\n", trans, table[len - 1]);
}

int main(int argc, char** argv)
{
        printf("/* this file is generated - do not edit */\n\n");

        if (CRC_LE_BITS > 1) {
                crc32init_le();
                printf("static const u32 crc32table_le[] = {");
                output_table(crc32table_le, LE_TABLE_SIZE, "tole");
                printf("};\n");
        }

        if (CRC_BE_BITS > 1) {
                crc32init_be();
                printf("static const u32 crc32table_be[] = {");
                output_table(crc32table_be, BE_TABLE_SIZE, "tobe");
                printf("};\n");
        }

        return 0;
}