gistfile1.c

/* test.c */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#ifndef _WIN32
#include <sys/time.h>
#endif

static char hexbyte1(char hex){
    switch (hex){
        case '0': return 0x0;
        case '1': return 0x1;
        case '2': return 0x2;
        case '3': return 0x3;
        case '4': return 0x4;
        case '5': return 0x5;
        case '6': return 0x6;
        case '7': return 0x7;
        case '8': return 0x8;
        case '9': return 0x9;
        case 'a':
        case 'A': return 0xa;
        case 'b':
        case 'B': return 0xb;
        case 'c':
        case 'C': return 0xc;
        case 'd':
        case 'D': return 0xd;
        case 'e':
        case 'E': return 0xe;
        case 'f':
        case 'F': return 0xf;
        default: return 0x0; /* something smarter? */
    }
}

static char hexbyte2(char hex) {
    char rv = hex - '0';	// handles '0' .. '9'
    if (rv > 9) rv -= 7;	// handles 'A' .. 'F'
    return rv & 0xF;		// handles 'a' .. 'f'
}

volatile char x;

void test1(){
    int i = 100000000;
    while(i--)
        x = hexbyte1('A'+i%6);
}
void test2(){
    int i = 100000000;
    while(i--)
        x = hexbyte2('A'+i%6);
}

typedef void(*nullary)();
static void time_it(nullary func, const char* name){
    double timer;

#ifdef _WIN32
    int64_t start, end;

    start = GetTickCount64();
    func();
    end = GetTickCount64();

    timer = end - start;
#else
    struct timeval start, end;

    gettimeofday(&start, NULL);
    func();
    gettimeofday(&end, NULL);

    timer = end.tv_sec - start.tv_sec;
    timer *= 1000000;
    timer += end.tv_usec - start.tv_usec;
    timer /= 1000000;
#endif

    printf("%-45s\t%15f\n", name, timer);
}

#define TIME(func) (time_it(func, #func))

int main(){

    TIME(test1);
    TIME(test2);
    TIME(test1);
    TIME(test2);
    return 0;
}