utils: Add memrchr(3) replacement for platforms that don't support it

For instance, on Mac OS X memrchr(3) is not provided by the C library.

configure.ac

@@ -533,7 +533,7 @@ AC_CHECK_FUNC(
 )
 
 AC_CHECK_FUNCS(prctl mallinfo getpass closefrom getpwnam_r getgrnam_r getpwuid_r)
-AC_CHECK_FUNCS(fmemopen funopen mmap)
+AC_CHECK_FUNCS(fmemopen funopen mmap memrchr)
 
 AC_CHECK_HEADERS(sys/sockio.h glob.h net/if_tun.h linux/fib_rules.h)
 AC_CHECK_HEADERS(net/pfkeyv2.h netipsec/ipsec.h netinet6/ipsec.h linux/udp.h)

src/libstrongswan/tests/suites/test_utils.c

@@ -345,6 +345,46 @@ START_TEST(test_memstr)
 }
 END_TEST
 
+/*******************************************************************************
+ * utils_memrchr
+ */
+
+static struct {
+	char *s;
+	int c;
+	size_t n;
+	int offset;
+} memrchr_data[] = {
+	{NULL, 'f', 0, -1},
+	{NULL, 'f', 3, -1},
+	{"", 'f', 0, -1},
+	{"", '\0', 1, 0},
+	{"foo", '\0', 3, -1},
+	{"foo", '\0', 4, 3},
+	{"foo", 'f', 3, 0},
+	{"foo", 'o', 3, 2},
+	{"foo", 'o', 2, 1},
+	{"foo", 'o', 1, -1},
+	{"foo", 'o', 0, -1},
+	{"foo", 'x', 3, -1},
+};
+
+START_TEST(test_utils_memrchr)
+{
+	void *ret;
+
+	ret = utils_memrchr(memrchr_data[_i].s, memrchr_data[_i].c, memrchr_data[_i].n);
+	if (memrchr_data[_i].offset >= 0)
+	{
+		ck_assert(ret == memrchr_data[_i].s + memrchr_data[_i].offset);
+	}
+	else
+	{
+		ck_assert(ret == NULL);
+	}
+}
+END_TEST
+
 /*******************************************************************************
  * translate
  */
@@ -673,6 +713,10 @@ Suite *utils_suite_create()
 	tcase_add_loop_test(tc, test_memstr, 0, countof(memstr_data));
 	suite_add_tcase(s, tc);
 
+	tc = tcase_create("utils_memrchr");
+	tcase_add_loop_test(tc, test_utils_memrchr, 0, countof(memrchr_data));
+	suite_add_tcase(s, tc);
+
 	tc = tcase_create("translate");
 	tcase_add_loop_test(tc, test_translate, 0, countof(translate_data));
 	suite_add_tcase(s, tc);

src/libstrongswan/utils/utils.c

@@ -103,7 +103,7 @@ void memwipe_noinline(void *ptr, size_t n)
  */
 void *memstr(const void *haystack, const char *needle, size_t n)
 {
-	unsigned const char *pos = haystack;
+	const u_char *pos = haystack;
 	size_t l;
 
 	if (!haystack || !needle || (l = strlen(needle)) == 0)
@@ -120,6 +120,28 @@ void *memstr(const void *haystack, const char *needle, size_t n)
 	return NULL;
 }
 
+/**
+ * Described in header.
+ */
+void *utils_memrchr(const void *s, int c, size_t n)
+{
+	const u_char *pos;
+
+	if (!s || !n)
+	{
+		return NULL;
+	}
+
+	for (pos = s + n - 1; pos >= (u_char*)s; pos--)
+	{
+		if (*pos == (u_char)c)
+		{
+			return (void*)pos;
+		}
+	}
+	return NULL;
+}
+
 /**
  * Described in header.
  */

src/libstrongswan/utils/utils.h

@@ -464,6 +464,20 @@ static inline void memwipe(void *ptr, size_t n)
  */
 void *memstr(const void *haystack, const char *needle, size_t n);
 
+/**
+ * Replacement for memrchr(3) if it is not provided by the C library.
+ *
+ * @param s		start of the memory area to search
+ * @param c		character to search
+ * @param n		length of memory area to search
+ * @return		pointer to the found character or NULL
+ */
+void *utils_memrchr(const void *s, int c, size_t n);
+
+#ifndef HAVE_MEMRCHR
+#define memrchr(s,c,n) utils_memrchr(s,c,n)
+#endif
+
 /**
  * Translates the characters in the given string, searching for characters
  * in 'from' and mapping them to characters in 'to'.