From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Elder Subject: [PATCH 03/16] libceph: define ceph_decode_string() Date: Wed, 11 Jul 2012 09:00:59 -0500 Message-ID: <4FFD871B.6020704@inktank.com> References: <4FFD847C.7070205@inktank.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-vb0-f46.google.com ([209.85.212.46]:57930 "EHLO mail-vb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757701Ab2GKOBC (ORCPT ); Wed, 11 Jul 2012 10:01:02 -0400 Received: by vbbff1 with SMTP id ff1so759843vbb.19 for ; Wed, 11 Jul 2012 07:01:01 -0700 (PDT) In-Reply-To: <4FFD847C.7070205@inktank.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: ceph-devel@vger.kernel.org There is no string decoding function defined in , 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 --- 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) -- 1.7.5.4