spaces.c

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

int f1(char *data, int count)
{
	int len = 0;

	/* OK, append the spaces */
	while (--count >= 0)
		data[len++] = ' ';
	data[len] = '\0';
	return len;
}

int f2(char *data, int count)
{
	memset(data, ' ', count);
	data[count] = '\0';
	return count;
}

#define NLOOPS 100000000
int main(void)
{
	char buffer[8];
	clock_t start, end;
	unsigned long long x = 0;

	start = clock();
	for (int i = 0; i < NLOOPS; i++)
	{
		x += f1(buffer, sizeof(buffer) - 1);
	}
	end = clock();

	printf("while %g seconds\n", (double) (end - start) / CLOCKS_PER_SEC);

	start = clock();
	for (int i = 0; i < NLOOPS; i++)
	{
		x += f2(buffer, sizeof(buffer) - 1);
	}
	end = clock();

	printf("memset %g seconds\n", (double) (end - start) / CLOCKS_PER_SEC);
	printf("%lld\n", x);
	return 0;
}