Shitty PCRE benchmarking

benchpcre.c

/* Shitty PCRE regexp benchmarking!
 *  $ gcc -o benchpcre benchpcre.c -ltr -lpcre
 *  $ ./benchpcre "^f.o$" "foo"
 *  result: 0
 *  Without extras:
 *  0.060841s elapsed
 *  With extras:
 *  0.058072s elapsed
 */
 
#include <pcre.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

void die(const char *fmt, ...) {
	va_list va;
	va_start(va, fmt);
	vfprintf(stderr, fmt, va);
	exit(1);
}

long double diff(const struct timespec *start, const struct timespec *end) {
	int64_t s = end->tv_sec;
	int64_t n = end->tv_nsec;
	long double res;

	// "Carry the one"
	if (n < start->tv_nsec) {
		--s;
		n += 1000000000;
	}

	res = n - start->tv_nsec;
	res /= 1000000000;
	res += s - start->tv_sec;
	return res;
}

void bench(const pcre *re, const pcre_extra* extra, const char* string) {
	int x;
	int slen = strlen(string);
	struct timespec start, end;

	clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &start);
	for (x = 0; x < 1000000; x++) {
		pcre_exec(re, extra, string, slen, 0, 0, NULL, 0);
	}
	clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &end);

	printf("%0.6LFs elapsed\n", diff(&start, &end));	
}

int main(int argc, char **argv) {
	const char *err = NULL;
	int erroff = 0;
	pcre *re;
	pcre_extra *extra;
	int x;
	
	if (argc != 3) {
		die("Usage: benchpcre <pattern> <string>\n");
	}

	re = pcre_compile(argv[1], 0, &err, &erroff, NULL);
	if (erroff != 0 || err != NULL) {
		die("pcre_compile failed: %d %s\n", erroff, err);
	}
	extra = pcre_study(re, 0, &err);
	if (err != NULL) {
		die("pcre_study failed: %s\n", err);
	}
	printf("result: %d\n", pcre_exec(re, extra, argv[2], strlen(argv[2]), 0, 0, NULL, 0));

	printf("Without extras:\n");
	bench(re, NULL, argv[2]);
	printf("With extras:\n");
	bench(re, extra, argv[2]);

	return 0;
}