libc: Implement strrchr()

This function will be used in one of the next patches to find the last
slash in a file name string.

Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

2 files changed, 29 insertions, 1 deletions

diff --git a/lib/libc/string/Makefile.inc b/lib/libc/string/Makefile.inc
index 7ccf3c4..0a77738 100644
--- a/lib/libc/string/Makefile.inc
+++ b/lib/libc/string/Makefile.inc
@@ -13,7 +13,7 @@
 
 STRING_SRC_C = strcat.c strchr.c strcmp.c strcpy.c strlen.c strncmp.c \
 		strncpy.c strstr.c memset.c memcpy.c memmove.c memchr.c \
-		memcmp.c strcasecmp.c strncasecmp.c strtok.c
+		memcmp.c strcasecmp.c strncasecmp.c strtok.c strrchr.c
 STRING_SRC_ASM = 
 STRING_SRCS = $(STRING_SRC_C:%=$(STRINGCMNDIR)/%) $(STRING_SRC_ASM:%=$(STRINGCMNDIR)/%)
 STRING_OBJS = $(STRING_SRC_C:%.c=%.o) $(STRING_SRC_ASM:%.S=%.o)
diff --git a/lib/libc/string/strrchr.c b/lib/libc/string/strrchr.c
new file mode 100644
index 0000000..ccfaa9f
--- /dev/null
+++ b/lib/libc/string/strrchr.c
@@ -0,0 +1,28 @@
+/******************************************************************************
+ * libc strrchr() implementation
+ *
+ * This program and the accompanying materials are made available under
+ * the terms of the BSD License which accompanies this distribution, and
+ * is available at http://www.opensource.org/licenses/bsd-license.php
+ *
+ * Contributors:
+ *     Thomas Huth - initial implementation
+ *****************************************************************************/
+
+#include <string.h>
+
+char *
+strrchr(const char *s, int c)
+{
+	char cb = c;
+	char *ptr = (char *)s + strlen(s) - 1;
+
+	while (ptr >= s) {
+		if (*ptr == cb) {
+			return ptr;
+		}
+		--ptr;
+	}
+
+	return NULL;
+}