On Thu, 12 Jul 2012, Alex Elder wrote:
> This adds a new utility routine which will return a dynamically-
> allocated buffer containing a string that has been decoded from ceph
> over-the-wire format. It also returns the length of the string
> if the address of a size variable is supplied to receive it.
>
> Signed-off-by: Alex Elder <[email protected]>
> ---
> v3: Final version. Sage convinced me that there was no need for
> ceph_decode_string() other than its use in this function, so
> now this implements what that function had been doing directly.
>
> include/linux/ceph/decode.h | 44
> ++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 44 insertions(+)
>
> Index: b/include/linux/ceph/decode.h
> ===================================================================
> --- a/include/linux/ceph/decode.h
> +++ b/include/linux/ceph/decode.h
> @@ -85,6 +85,50 @@ static inline int ceph_has_room(void **p
> } while (0)
>
> /*
> + * Allocate a buffer big enough to hold the wire-encoded string, and
> + * decode the string into it. The resulting string will always be
> + * terminated with '\0'. If successful, *p will be advanced
> + * past the decoded data. Also, if lenp is not a null pointer, the
> + * length (not including the terminating '\0') will be recorded in
> + * *lenp. Note that a zero-length string is a valid return value.
> + *
> + * Returns a pointer to the newly-allocated string buffer, or a null
> + * pointer if an error occurs. Neither *p nor *lenp will have been
> + * updated if NULL is returned.
> + *
> + * There are two possible failures:
> + * - converting the string would require accessing memory at or
> + * beyond the "end" pointer provided
> + * - memory could not be allocated for the result
I think the caller should be able to distinguish between these two cases
in the return value. What about:
> + */
> +static inline char *ceph_extract_encoded_string(void **p, void *end,
> + size_t *lenp, gfp_t gfp)
int ceph_extract_encoded_string(void **p, void *end, char **str, gfp_t gfp)
and return the length, or an error code? That avoids futzing with ERR_PTR
and gives you the len a bit less awkwardly...
sage
> +{
> + u32 len;
> + void *sp = *p;
> + char *buf = NULL;
> +
> + ceph_decode_32_safe(&sp, end, len, out);
> + if (!ceph_has_room(&sp, end, len))
> + return NULL;
> +
> + buf = kmalloc(len + 1, gfp);
> + if (!buf)
> + return NULL;
> +
> + if (len)
> + memcpy(buf, sp, len);
> + buf[len] = '\0';
> +
> + *p = (char *) *p + sizeof (u32) + len;
> +
> + if (lenp)
> + *lenp = (size_t) len;
> +out:
> + return buf;
> +}
> +
> +/*
> * struct ceph_timespec <-> struct timespec
> */
> static inline void ceph_decode_timespec(struct timespec *ts,
> --
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>
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