lib/strutils: move *swith() functions to private library

Avoid code dublication in libmount and time-util.

Proposed-by: Karel Zak <kzak@redhat.com>
Reference: http://markmail.org/message/h7zexvqsieqngtmx
Signed-off-by: Sami Kerola <kerolasa@iki.fi>

lib/strutils.c

@@ -10,6 +10,7 @@
 #include <errno.h>
 #include <sys/stat.h>
 #include <string.h>
+#include <assert.h>
 
 #include "c.h"
 #include "nls.h"
@@ -685,6 +686,72 @@ int streq_except_trailing_slash(const char *s1, const char *s2)
 	return equal;
 }
 
+/*
+ * Match string beginning.
+ */
+char *startswith(const char *s, const char *prefix)
+{
+	const char *a, *b;
+
+	assert(s);
+	assert(prefix);
+
+	a = s, b = prefix;
+	for (;;) {
+		if (*b == 0)
+			return (char *)a;
+		if (*a != *b)
+			return NULL;
+
+		a++, b++;
+	}
+}
+
+/*
+ * Case insensitive match string beginning.
+ */
+char *startswith_no_case(const char *s, const char *prefix)
+{
+	const char *a, *b;
+
+	assert(s);
+	assert(prefix);
+
+	a = s, b = prefix;
+	for (;;) {
+		if (*b == 0)
+			return (char *)a;
+		if (tolower(*a) != tolower(*b))
+			return NULL;
+
+		a++, b++;
+	}
+}
+
+/*
+ * Match string ending.
+ */
+char *endswith(const char *s, const char *postfix)
+{
+	size_t sl, pl;
+
+	assert(s);
+	assert(postfix);
+
+	sl = strlen(s);
+	pl = strlen(postfix);
+
+	if (pl == 0)
+		return (char *)s + sl;
+
+	if (sl < pl)
+		return NULL;
+
+	if (memcmp(s + sl - pl, postfix, pl) != 0)
+		return NULL;
+
+	return (char *)s + sl - pl;
+}
 
 #ifdef TEST_PROGRAM