#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <strings.h>
#include <stdlib.h>
#include <sys/endian.h>
#include <sys/time.h>

#define NOF_TESTS 1024*1024

#define STR_LEN 19
typedef char fixed_string[STR_LEN+1];

static 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;
}

//////////////////////////////////////////////////////////////////////////////
// BEGIN memcmp.c
//////////////////////////////////////////////////////////////////////////////

#define IS_ALIGNED(x) (((size_t)(x) & sizeof(size_t)-1) == 0)

/*
 * Compare memory regions.
 */
int
my_memcmp(const void *s1, const void *s2, size_t n)
{

	if (n == 0)
		return (0);

	/* If the two args are aligned, compare them one word at a time. */
	const size_t *p1 = s1, *p2 = s2;
	if (((size_t)s1 & (sizeof(size_t) - 1)) == 0 &&
	    ((size_t)s2 & (sizeof(size_t) - 1)) == 0) {
		while (n >= sizeof(size_t) && *p1 == *p2) {
			++p1;
			++p2;
			n -= sizeof(size_t);
		}
		if (n == 0)
			return (0);
	}

	/* Usual byte-by-byte comparison. */
	const char *c1 = (const char *)p1, *c2 = (const char *)p2;
	while (--n > 0 && *c1 == *c2) {
		++c1;
		++c2;
	}
	return (*c1 - *c2);
}

//////////////////////////////////////////////////////////////////////////////
// END memcmp.c
//////////////////////////////////////////////////////////////////////////////

int main()
{
    fixed_string * c1 = malloc(NOF_TESTS * sizeof(*c1));
    fixed_string * c2 = malloc(NOF_TESTS * sizeof(*c2));

    int * d1 = malloc(NOF_TESTS * sizeof(*d1));
    int * d2 = malloc(NOF_TESTS * sizeof(*d2));

    for (size_t i = 0; i < NOF_TESTS; ++i) {
        strcpy(c1[i], gen_str());
        strcpy(c2[i], gen_str());
    }

    struct timeval start, end;

    gettimeofday(&start, NULL);
    for (size_t i = 0; i < NOF_TESTS; ++i) {
        d1[i] = memcmp(c1[i], c2[i], STR_LEN);
    }
    gettimeofday(&end, NULL);
    printf("theirs: %lu\n", ((end.tv_sec - start.tv_sec)*1000000L + end.tv_usec) - start.tv_usec);

    gettimeofday(&start, NULL);
    for (size_t i = 0; i < NOF_TESTS; ++i) {
        d2[i] = my_memcmp(c1[i], c2[i], STR_LEN);
    }
    gettimeofday(&end, NULL);
    printf("mine  : %lu\n", ((end.tv_sec - start.tv_sec)*1000000L + end.tv_usec) - start.tv_usec);

    for (size_t i = 0; i < NOF_TESTS; ++i) {
        assert(d1[i] == d2[i]);
    }

    for (size_t t = 1; t < 64; ++t) {
	    size_t * x1 = malloc(t * 2);
	    size_t * x2 = malloc(t * 2);
	    size_t i = 0;
	    for (i = 0; i < t ; ++i) {
		    x1[i] = 'A';
		    x2[i] = 'A';
	    }
	    x1[i] = 'A'; x1[i+1] = '\0';
	    x2[i] = 'B'; x2[i+1] = '\0';
	    assert(my_memcmp(x1, x2, t) == 0);
	    free(x1);
	    free(x2);
    }

}