diff --git a/src/xdiff/xutils.c b/src/xdiff/xutils.c
index f13a854..a4370e6 100644
--- a/src/xdiff/xutils.c
+++ b/src/xdiff/xutils.c
@@ -122,7 +122,7 @@
 	long nl = 0, size, tsize = 0;
 	char const *data, *cur, *top;
 
-	if ((cur = data = xdl_mmfile_first(mf, &size)) != NULL) {
+	if ((cur = data = xdl_mmfile_first(mf, &size))) {
 		for (top = data + size; nl < sample && cur < top; ) {
 			nl++;
 			if (!(cur = memchr(cur, '\n', top - cur)))
@@ -432,3 +432,20 @@
 
 	return 0;
 }
+
+void* xdl_alloc_grow_helper(void *p, long nr, long *alloc, size_t size)
+{
+	void *tmp = NULL;
+	size_t n = ((LONG_MAX - 16) / 2 >= *alloc) ? 2 * *alloc + 16 : LONG_MAX;
+	if (nr > (long)n)
+		n = nr;
+	if (SIZE_MAX / size >= n)
+		tmp = xdl_realloc(p, n * size);
+	if (tmp) {
+		*alloc = n;
+	} else {
+		xdl_free(p);
+		*alloc = 0;
+	}
+	return tmp;
+}