#include <assert.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <time.h>

#define NOF_ELEM 1000000
#define STR_LEN 256

typedef char fixed_string[STR_LEN+1];

const char * gen_str() {
    static fixed_string s;
    for (size_t i = 0; i < sizeof(fixed_string)-1; ++i) {
        s[i] = rand() % 25 + 65;
    }
    s[sizeof(s)-1] = '\0';
    return s;
}

int
my_memcmp(const char* s1, const char* s2, size_t n)
{
    if (!n) return 0;
    while (--n && *s1 == *s2) {
        ++s1;
        ++s2;
    }
    return *s1 - *s2;
}


int main()
{
    clock_t begin, end;

    fixed_string * arr = malloc(sizeof(fixed_string) * NOF_ELEM);
    int * r1 = malloc(NOF_ELEM * sizeof(*r1));
    int * r2 = malloc(NOF_ELEM * sizeof(*r2));

    for (size_t i = 0; i < NOF_ELEM; ++i) {
        strncpy(arr[i], gen_str(), sizeof(*arr)-1);
    }

    /* memcmp */
    begin = clock();
    for (size_t i = 0; i < NOF_ELEM-1; ++i) {
        r1[i] = memcmp(arr[i], arr[i+1], sizeof(*arr));
    }
    end = clock();
    printf("   memcmp: %d\n", (end-begin) * CLOCKS_PER_SEC);

    /* my_memcmp */
    begin = clock();
    for (size_t i = 0; i < NOF_ELEM-1; ++i) {
        r2[i] = my_memcmp(arr[i], arr[i+1], sizeof(*arr));
    }
    end = clock();
    printf("my_memcmp: %d\n", (end-begin) * CLOCKS_PER_SEC);

    for (size_t i = 0; i < NOF_ELEM-1; ++i) {
        assert(r1[i] == r2[i]);
    }
}