lkml.org 
[lkml]   [2019]   [Feb]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[v2] lib/string: add memrchr function
Date
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@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
\
 
 \ /
  Last update: 2019-02-12 19:57    [W:0.053 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site