From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sage Weil Subject: Re: [PATCH v3 04/16] libceph: define ceph_extract_encoded_string() Date: Thu, 12 Jul 2012 11:20:21 -0700 (PDT) Message-ID: References: <4FFD847C.7070205@inktank.com> <4FFD8727.7050106@inktank.com> <4FFDF9B8.5040401@inktank.com> <4FFF05D4.9080006@inktank.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Return-path: Received: from cobra.newdream.net ([66.33.216.30]:47316 "EHLO cobra.newdream.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932690Ab2GLSUW (ORCPT ); Thu, 12 Jul 2012 14:20:22 -0400 In-Reply-To: <4FFF05D4.9080006@inktank.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Alex Elder Cc: ceph-devel@vger.kernel.org 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 > --- > 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, > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > >