xdiff/xutils.c(xdl_hash_record): factor out whitespace handling

Since in at least one use case, xdl_hash_record() takes over 15% of the
CPU time, it makes sense to even micro-optimize it. For many cases, no
whitespace special handling is needed, and in these cases we should not
even bother to check for whitespace in _every_ iteration of the loop.

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

xdiff/xutils.c

@@ -236,12 +236,13 @@ int xdl_recmatch(const char *l1, long s1, const char *l2, long s2, long flags)
 	return 0;
 }
 
-unsigned long xdl_hash_record(char const **data, char const *top, long flags) {
+static unsigned long xdl_hash_record_with_whitespace(char const **data,
+		char const *top, long flags) {
 	unsigned long ha = 5381;
 	char const *ptr = *data;
 
 	for (; ptr < top && *ptr != '\n'; ptr++) {
-		if (isspace(*ptr) && (flags & XDF_WHITESPACE_FLAGS)) {
+		if (isspace(*ptr)) {
 			const char *ptr2 = ptr;
 			while (ptr + 1 < top && isspace(ptr[1])
 					&& ptr[1] != '\n')
@@ -270,6 +271,23 @@ unsigned long xdl_hash_record(char const **data, char const *top, long flags) {
 }
 
 
+unsigned long xdl_hash_record(char const **data, char const *top, long flags) {
+	unsigned long ha = 5381;
+	char const *ptr = *data;
+
+	if (flags & XDF_WHITESPACE_FLAGS)
+		return xdl_hash_record_with_whitespace(data, top, flags);
+
+	for (; ptr < top && *ptr != '\n'; ptr++) {
+		ha += (ha << 5);
+		ha ^= (unsigned long) *ptr;
+	}
+	*data = ptr < top ? ptr + 1: ptr;
+
+	return ha;
+}
+
+
 unsigned int xdl_hashbits(unsigned int size) {
 	unsigned int val = 1, bits = 0;