Re: [PATCH 03/16] libceph: define ceph_decode_string()

[Josh Durgin <josh.durgin@inktank.com>]

Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

On 07/11/2012 07:00 AM, Alex Elder wrote:
> There is no string decoding function defined in<decode.h>, so this
> defines one.
>
> This function is a little different from the others in that the
> length of the encoded string is not known a priori.  So the
> interface is defined a bit like snprintf(), where the value returned
> indicates the space required--even if it's more than the space
> allotted.
>
> Signed-off-by: Alex Elder<elder@inktank.com>
> ---
>   include/linux/ceph/decode.h |   36 ++++++++++++++++++++++++++++++++++++
>   1 files changed, 36 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/ceph/decode.h b/include/linux/ceph/decode.h
> index bcbd66c..7ead11fc 100644
> --- a/include/linux/ceph/decode.h
> +++ b/include/linux/ceph/decode.h
> @@ -44,6 +44,42 @@ static inline void ceph_decode_copy(void **p, void
> *pv, size_t n)
>   }
>
>   /*
> + * Decode the wire-encoded string at *p into the buffer "s"
> + * provided, whose size is indicated by "size".  Note that "s" can
> + * be a null pointer if size is 0.  If it fits, the resulting string
> + * will always be terminated with '\0'; otherwise the buffer will
> + * be unchanged.
> + *
> + * Returns the length of the encoded string (which may be greater
> + * than or equal to the buffer size).  The return value does not
> + * include the terminating '\0'.
> + *
> + * If the the return value is less than the size provided, *p will
> + * be advanced past the decoded data; otherwise it is unchanged.
> + * This allows for a two call sequence to be used to allocate
> + * sufficient space for the string.
> + *
> + * NB  It is assumed that *p refers to a block of valid memory
> + *     sufficient to hold the length field followed by the number
> + *     of bytes indicated by that field.
> + */
> +static inline size_t ceph_decode_string(void **p, char *s, size_t size)
> +{
> +	size_t len;
> +
> +	len = get_unaligned_le32(*p);
> +	if (size<  len + 1)
> +		return len;
> +
> +	if (len)
> +		memcpy(s, (char *) *p + sizeof (u32), len);
> +	*(s + len) = '\0';
> +	*p += sizeof (u32) + len;
> +
> +	return len;
> +}
> +
> +/*
>    * bounds check input.
>    */
>   static inline int ceph_has_room(void **p, void *end, size_t n)