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Subject[PATCH] lib/string: add memrchr function
Date
Here is the detailed description for memrchr:
https://linux.die.net/man/3/memrchr

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
---
include/linux/string.h | 1 +
lib/string.c | 21 +++++++++++++++++++++
2 files changed, 22 insertions(+)

diff --git a/include/linux/string.h b/include/linux/string.h
index 7927b87..f380f4b 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -167,6 +167,7 @@ static inline void memcpy_flushcache(void *dst, const void *src, size_t cnt)
memcpy(dst, src, cnt);
}
#endif
+void *memrchr(const void *s, int c, size_t n);
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..92914f6 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -964,6 +964,27 @@ void *memchr(const void *s, int c, size_t n)
EXPORT_SYMBOL(memchr);
#endif

+/**
+ * memrchr - Find a character in an area of memory.
+ * @s: The memory area
+ * @c: The byte to search for
+ * @n: The size of the area.
+ *
+ * returns 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);
+
static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
{
while (bytes) {
--
2.7.4
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