From patchwork Wed Jan 2 15:15:45 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 209071 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id D5DDE2C0087 for ; Thu, 3 Jan 2013 03:13:59 +1100 (EST) Received: from localhost ([::1]:44408 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TqQ41-0001kT-Bz for incoming@patchwork.ozlabs.org; Wed, 02 Jan 2013 10:17:05 -0500 Received: from eggs.gnu.org ([208.118.235.92]:42505) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TqQ3S-0000X5-3Z for qemu-devel@nongnu.org; Wed, 02 Jan 2013 10:16:32 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TqQ3M-0005b7-7F for qemu-devel@nongnu.org; Wed, 02 Jan 2013 10:16:29 -0500 Received: from mx1.redhat.com ([209.132.183.28]:30817) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TqQ3L-0005b2-KH for qemu-devel@nongnu.org; Wed, 02 Jan 2013 10:16:24 -0500 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r02FGNNS018621 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Wed, 2 Jan 2013 10:16:23 -0500 Received: from localhost (ovpn-112-16.ams2.redhat.com [10.36.112.16]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id r02FGLQD013108; Wed, 2 Jan 2013 10:16:22 -0500 From: Stefan Hajnoczi To: Date: Wed, 2 Jan 2013 16:15:45 +0100 Message-Id: <1357139756-11951-8-git-send-email-stefanha@redhat.com> In-Reply-To: <1357139756-11951-1-git-send-email-stefanha@redhat.com> References: <1357139756-11951-1-git-send-email-stefanha@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.22 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: Anthony Liguori , Stefan Hajnoczi Subject: [Qemu-devel] [PATCH 07/18] iov: add iov_discard_front/back() to remove data X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org The iov_discard_front/back() functions remove data from the front or back of the vector. This is useful when peeling off header/footer structs. Signed-off-by: Stefan Hajnoczi --- include/qemu/iov.h | 13 +++++++++++++ iov.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 64 insertions(+) diff --git a/include/qemu/iov.h b/include/qemu/iov.h index d06f8b9..68d25f2 100644 --- a/include/qemu/iov.h +++ b/include/qemu/iov.h @@ -99,4 +99,17 @@ unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt, const struct iovec *iov, unsigned int iov_cnt, size_t offset, size_t bytes); +/* + * Remove a given number of bytes from the front or back of a vector. + * This may update iov and/or iov_cnt to exclude iovec elements that are + * no longer required. + * + * The number of bytes actually discarded is returned. This number may be + * smaller than requested if the vector is too small. + */ +size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt, + size_t bytes); +size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt, + size_t bytes); + #endif diff --git a/iov.c b/iov.c index 419e419..92ad77b 100644 --- a/iov.c +++ b/iov.c @@ -354,3 +354,54 @@ size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset, { return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes); } + +size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt, + size_t bytes) +{ + size_t total = 0; + struct iovec *cur; + + for (cur = *iov; *iov_cnt > 0; cur++) { + if (cur->iov_len > bytes) { + cur->iov_base += bytes; + cur->iov_len -= bytes; + total += bytes; + break; + } + + bytes -= cur->iov_len; + total += cur->iov_len; + *iov_cnt -= 1; + } + + *iov = cur; + return total; +} + +size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt, + size_t bytes) +{ + size_t total = 0; + struct iovec *cur; + + if (*iov_cnt == 0) { + return 0; + } + + cur = iov + (*iov_cnt - 1); + + while (*iov_cnt > 0) { + if (cur->iov_len > bytes) { + cur->iov_len -= bytes; + total += bytes; + break; + } + + bytes -= cur->iov_len; + total += cur->iov_len; + cur--; + *iov_cnt -= 1; + } + + return total; +}