#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/time.h>

#define COUNT 1024
#define BUFSIZE (1024*1024)

char *buf;

void read_file(int fd)
{
	int i;

	if (ftruncate(fd, BUFSIZE*COUNT) < 0) {
		perror("truncate");
		exit(1);
	}
	for (i = 0; i < COUNT; i++) {
		if (read(fd, buf, BUFSIZE) != BUFSIZE) {
			perror("read");
			exit(1);
		}
	}
}

int main(int argc, char **argv)
{
	int fd;
	int fcount, i, stages;
	char fname[128];
	struct timeval start, end;

	if (argc != 4) {
		fprintf(stderr, "Usage: trunc-bench <file> <file-count> <stages>\n");
		return 1;
	}
	fcount = strtol(argv[2], NULL, 0);
	stages = strtol(argv[3], NULL, 0);
	buf = malloc(BUFSIZE);
	if (!buf) {
		fprintf(stderr, "Cannot allocate write buffer.\n");
		return 1;
	}
	memset(buf, 'a', BUFSIZE);
	
	if (stages & 1) {
		fprintf(stderr, "Creating files...\n");
		for (i = 0; i < fcount; i++ ) {
			sprintf(fname, "%s%d", argv[1], i);
			fd = open(fname, O_RDWR | O_TRUNC | O_CREAT, 0644);
			if (fd < 0) {
				perror("open");
				return 1;
			}
			read_file(fd);
			close(fd);
		}
	}
	if (stages & 2) {
		fprintf(stderr, "Removing files...\n");
		gettimeofday(&start, NULL);
		for (i = 0; i < fcount; i++ ) {
			sprintf(fname, "%s%d", argv[1], i);
			truncate(fname, 0);
		}
		gettimeofday(&end, NULL);
		printf("%lu us\n", (end.tv_sec - start.tv_sec) * 1000000UL + (end.tv_usec - start.tv_usec));
	}
	fprintf(stderr, "Done.\n");

	return 0;
}