On 2/13/19 7:48 PM, Xiang Xiao wrote:
> 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 | 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.
This should say up front that this is a reverse search, from the end of
the memory area backwards.
> + * @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
* 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);
> +
> static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
> {
> while (bytes) {
>
--
~Randy
