how to conventer unsigned long to BCD code faster？

#define DIM(a)  (sizeof(a) / sizeof(a[0]))

void bin2bcd(unsigned long bin, unsigned char *bcd)
{
    static const unsigned long pow_ten_tbl[] = {
        1000000000,
        100000000,
        10000000,
        1000000,
        100000,
        10000,
        1000,
        100,
        10,
        1
    };
    unsigned long pow_ten;
    unsigned char digit;
    unsigned char i;

    for (i = 0; i != DIM(pow_ten_tbl); i++) {
        digit = 0;
        pow_ten = pow_ten_tbl[i];

        while (bin >= pow_ten) {
            bin -= pow_ten;
            digit++;
        }
        *bcd++ = digit;
    }
}

#define DIM(a)  (sizeof(a) / sizeof(a[0]))

void bin2bcd(unsigned long bin, unsigned char *bcd)
{
    static const unsigned long pow_ten_tbl[] = {
        1000000000,
        100000000,
        10000000,
        1000000,
        100000,
        10000,
        1000,
        100,
        10,
        1
    };
    unsigned long pow_ten;
    unsigned char digit;
    unsigned char i;

    for (i = 0; i != DIM(pow_ten_tbl); i++) {
        digit = 0;
        pow_ten = pow_ten_tbl[i];

        while (bin >= pow_ten) {
            bin -= pow_ten;
            digit++;
        }
        *bcd++ = digit;
    }
}

i'am try you code，but it can't build success.
Build target 'Target 1'
compiling u32tobcd.c...
U32TOBCD.C(23): warning C206: 'DIM': missing function-prototype
U32TOBCD.C(23): error C267: 'DIM': requires ANSI-style prototype
Target not created

my test code:

#include <reg52.h>
#include <math.h>
unsigned char bcdt[10]={0,0,0,0,0,0,0,0,0,0};
unsigned char *bcd;
void bin2bcd(unsigned long bin, unsigned char *bcd)
{ static const unsigned long pow_ten_tbl[] = { 1000000000, 100000000, 10000000, 1000000, 100000, 10000, 1000, 100, 10, 1 }; unsigned long pow_ten; unsigned char digit; unsigned char i;

for (i = 0; i != DIM(pow_ten_tbl); i++) { digit = 0; pow_ten = pow_ten_tbl[i];

while (bin >= pow_ten) { bin -= pow_ten; digit++; } *bcd++ = digit; }
}

void main(void) { while(1) { bin2bcd(1234567,*bcd); } }

converter 4294967295 dec to BCD just cost 3770us @ 12MHz normal 8051 MCU.