Here is the detailed description for memrchr:
void *memrchr(const void *s, int c, size_t n);
The memrchr() function is like the memchr() function, except
that it searches backward from the end of the n bytes pointed
to by s instead of forward from the beginning.
The memrchr() functions return a pointer to the matching byte
or NULL if the character does not occur in the given memory
area.
Signed-off-by: Xiang Xiao <xiaoxiang@xxxxxxxxxx>
---
include/linux/string.h | 3 +++
lib/string.c | 23 +++++++++++++++++++++++
2 files changed, 26 insertions(+)
diff --git a/include/linux/string.h b/include/linux/string.h
index 7927b87..915c617 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -167,6 +167,9 @@ static inline void memcpy_flushcache(void *dst, const void *src, size_t cnt)
memcpy(dst, src, cnt);
}
#endif
+#ifndef __HAVE_ARCH_MEMRCHR
+void *memrchr(const void *s, int c, size_t n);
+#endif
void *memchr_inv(const void *s, int c, size_t n);
char *strreplace(char *s, char old, char new);
diff --git a/lib/string.c b/lib/string.c
index 38e4ca0..595e0b3 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -964,6 +964,29 @@ void *memchr(const void *s, int c, size_t n)
EXPORT_SYMBOL(memchr);
#endif
+#ifndef __HAVE_ARCH_MEMRCHR
+/**
+ * memrchr - Find the last character in an area of memory.
+ * @s: The memory area
+ * @c: The byte to search for
+ * @n: The size of the area.
+ *
+ * Return: the address of the last occurrence of @c, or %NULL
+ * if @c is not found
+ */
+void *memrchr(const void *s, int c, size_t n)
+{
+ const unsigned char *p = s + n;
+
+ while (n-- != 0) {
+ if ((unsigned char)c == *--p)
+ return (void *)p;
+ }
+ return NULL;
+}
+EXPORT_SYMBOL(memrchr);
+#endif
+
static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
{
while (bytes) {
--
2.7.4
