From patchwork Thu Nov 22 15:16:48 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 201068 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 F41132C00A6 for ; Fri, 23 Nov 2012 02:24:38 +1100 (EST) Received: from localhost ([::1]:35881 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TbYXD-0007UT-2H for incoming@patchwork.ozlabs.org; Thu, 22 Nov 2012 10:17:47 -0500 Received: from eggs.gnu.org ([208.118.235.92]:48525) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TbYWs-0006kl-Ua for qemu-devel@nongnu.org; Thu, 22 Nov 2012 10:17:32 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TbYWi-0007JS-Pv for qemu-devel@nongnu.org; Thu, 22 Nov 2012 10:17:22 -0500 Received: from mx1.redhat.com ([209.132.183.28]:50535) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TbYWi-0007JE-It for qemu-devel@nongnu.org; Thu, 22 Nov 2012 10:17:16 -0500 Received: from int-mx12.intmail.prod.int.phx2.redhat.com (int-mx12.intmail.prod.int.phx2.redhat.com [10.5.11.25]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id qAMFHFvc006604 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Thu, 22 Nov 2012 10:17:15 -0500 Received: from localhost (ovpn-112-32.ams2.redhat.com [10.36.112.32]) by int-mx12.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id qAMFHDcB004211; Thu, 22 Nov 2012 10:17:13 -0500 From: Stefan Hajnoczi To: Date: Thu, 22 Nov 2012 16:16:48 +0100 Message-Id: <1353597412-12232-8-git-send-email-stefanha@redhat.com> In-Reply-To: <1353597412-12232-1-git-send-email-stefanha@redhat.com> References: <1353597412-12232-1-git-send-email-stefanha@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.25 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: Kevin Wolf , Anthony Liguori , "Michael S. Tsirkin" , Blue Swirl , khoa@us.ibm.com, Stefan Hajnoczi , Paolo Bonzini , Asias He Subject: [Qemu-devel] [PATCH v4 07/11] iov: add iov_discard() 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() function removes data from the front or back of the vector. This is useful when peeling off header/footer structs. Signed-off-by: Stefan Hajnoczi --- iov.c | 41 +++++++++++++++++++++++++++++++++++++++++ iov.h | 13 +++++++++++++ 2 files changed, 54 insertions(+) diff --git a/iov.c b/iov.c index a81eedc..6eed089 100644 --- a/iov.c +++ b/iov.c @@ -354,3 +354,44 @@ size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset, { return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes); } + +size_t iov_discard(struct iovec **iov, unsigned int *iov_cnt, ssize_t bytes) +{ + size_t total = 0; + struct iovec *cur; + int direction; + + if (*iov_cnt == 0) { + return 0; + } + + if (bytes < 0) { + bytes = -bytes; + direction = -1; + cur = *iov + (*iov_cnt - 1); + } else { + direction = 1; + cur = *iov; + } + + while (*iov_cnt > 0) { + if (cur->iov_len > bytes) { + if (direction > 0) { + cur->iov_base += bytes; + } + cur->iov_len -= bytes; + total += bytes; + break; + } + + bytes -= cur->iov_len; + total += cur->iov_len; + cur += direction; + *iov_cnt -= 1; + } + + if (direction > 0) { + *iov = cur; + } + return total; +} diff --git a/iov.h b/iov.h index 34c8ec9..d6d1fa6 100644 --- a/iov.h +++ b/iov.h @@ -95,3 +95,16 @@ void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt, 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. + * + * Data is discarded from the front of the vector if bytes is positive and + * from the back of the vector if bytes is negative. + * + * 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(struct iovec **iov, unsigned int *iov_cnt, ssize_t bytes);