Skip to main content

Browse the archive

Staging
v0.5.1
https://github.com/git/git
23 January 2022, 05:21:09 UTC
Revision 9de0834663f28bee9e6b2c4647ed6128241ed26f authored by Linus Torvalds on 17 October 2006, 02:58:54 UTC, committed by Junio C Hamano on 17 October 2006, 04:27:44 UTC 
Fix hash function in xdiff library
 
Jim Mayering noticed that xdiff library took insanely long time
when comparing files with many identical lines.

This was because the hash function used in the library is broken
on 64-bit architectures and caused too many collisions.

http://thread.gmane.org/gmane.comp.version-control.git/28962/focus=28994

Acked-by: Davide Libenzi <davidel@xmaliserver.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
1 parent 6fe5b7f
Raw File
Tip revision: 9de0834663f28bee9e6b2c4647ed6128241ed26f authored by Linus Torvalds on 17 October 2006, 02:58:54 UTC
Fix hash function in xdiff library
Tip revision: 9de0834
test-sha1.c 
#include "cache.h"

int main(int ac, char **av)
{
	SHA_CTX ctx;
	unsigned char sha1[20];
	unsigned bufsz = 8192;
	char *buffer;

	if (ac == 2)
		bufsz = strtoul(av[1], NULL, 10) * 1024 * 1024;

	if (!bufsz)
		bufsz = 8192;

	while ((buffer = malloc(bufsz)) == NULL) {
		fprintf(stderr, "bufsz %u is too big, halving...\n", bufsz);
		bufsz /= 2;
		if (bufsz < 1024)
			die("OOPS");
	}

	SHA1_Init(&ctx);

	while (1) {
		ssize_t sz, this_sz;
		char *cp = buffer;
		unsigned room = bufsz;
		this_sz = 0;
		while (room) {
			sz = xread(0, cp, room);
			if (sz == 0)
				break;
			if (sz < 0)
				die("test-sha1: %s", strerror(errno));
			this_sz += sz;
			cp += sz;
			room -= sz;
		}
		if (this_sz == 0)
			break;
		SHA1_Update(&ctx, buffer, this_sz);
	}
	SHA1_Final(sha1, &ctx);
	puts(sha1_to_hex(sha1));
	exit(0);
}
back to top