Silly unrolled print function

print_nine_digit_positive.c

#include <assert.h>
#include <stdint.h>
#include <unistd.h>

/* print nine digit positive */
char *p9dp(uint32_t n, char *p)
{
    uint32_t a = n % 10;
    n /= 10;
    if (n) {
        uint32_t b = n % 10;
        n /= 10;
        if (n) {
            uint32_t c = n % 10;
            n /= 10;
            if (n) {
                uint32_t d = n % 10;
                n /= 10;
                if (n) {
                    uint32_t e = n % 10;
                    n /= 10;
                    if (n) {
                        uint32_t f = n % 10;
                        n /= 10;
                        if (n) {
                            uint32_t g = n % 10;
                            n /= 10;
                            if (n) {
                                uint32_t h = n % 10;
                                n /= 10;
                                if (n) {
                                    uint32_t i = n;
                                    *p++ = '0' + i;
                                }
                                *p++ = '0' + h;
                            }
                            *p++ = '0' + g;
                        }
                        *p++ = '0' + f;
                    }
                    *p++ = '0' + e;
                }
                *p++ = '0' + d;
            }
            *p++ = '0' + c;
        }
        *p++ = '0' + b;
    }
    *p++ = '0' + a;
    return p;
}

#define N 15000000
char buffer[10 * (size_t)N];

int main()
{
    char *p = buffer;
    for (uint32_t i = 1; i <= N; i++) {
        p = p9dp(i, p);
        *p++ = '\n';
    }
    write(1, buffer, p - buffer);
    return 0;
}