libc: add memrchr
This function scans a string backwards from the end for the first
instance of a character.
Change-Id: I46b21573ed25a0ff222eac340e1e1fb93b040763
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>
diff --git a/lib/libc/memrchr.c b/lib/libc/memrchr.c
new file mode 100644
index 0000000..01caef3
--- /dev/null
+++ b/lib/libc/memrchr.c
@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2019, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <string.h>
+
+#undef memrchr
+
+void *memrchr(const void *src, int c, size_t len)
+{
+ const unsigned char *s = src + (len - 1);
+
+ while (len--) {
+ if (*s == (unsigned char)c) {
+ return (void*) s;
+ }
+
+ s--;
+ }
+
+ return NULL;
+}