From mboxrd@z Thu Jan 1 00:00:00 1970 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 From: Stefan Hajnoczi 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> Subject: [Qemu-devel] [PATCH 07/18] iov: add iov_discard_front/back() to remove data List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Anthony Liguori , Stefan Hajnoczi 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; +} -- 1.8.0.2