From 530c0bbd73e1b658c9266582072847de1fbdff10 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Thu, 22 Nov 2012 16:06:06 +0100 Subject: [PATCH] iov: add qemu_iovec_concat_iov() The qemu_iovec_concat() function copies a subset of a QEMUIOVector. The new qemu_iovec_concat_iov() function does the same for a iov/cnt pair. It is easy to define qemu_iovec_concat() in terms of qemu_iovec_concat_iov(). The existing code is mostly unchanged, except for the assertion src->size >= soffset, which cannot be efficiently checked upfront on a iov/cnt pair. Instead we assert upon hitting the end of src with an unsatisfied soffset. Signed-off-by: Stefan Hajnoczi --- include/qemu-common.h | 3 +++ iov.c | 39 +++++++++++++++++++++++++++------------ 2 files changed, 30 insertions(+), 12 deletions(-) diff --git a/include/qemu-common.h b/include/qemu-common.h index 6871cab371..2b83de395c 100644 --- a/include/qemu-common.h +++ b/include/qemu-common.h @@ -329,6 +329,9 @@ void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov); void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len); void qemu_iovec_concat(QEMUIOVector *dst, QEMUIOVector *src, size_t soffset, size_t sbytes); +void qemu_iovec_concat_iov(QEMUIOVector *dst, + struct iovec *src_iov, unsigned int src_cnt, + size_t soffset, size_t sbytes); void qemu_iovec_destroy(QEMUIOVector *qiov); void qemu_iovec_reset(QEMUIOVector *qiov); size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset, diff --git a/iov.c b/iov.c index 92ad77b162..c0f5c56618 100644 --- a/iov.c +++ b/iov.c @@ -289,34 +289,49 @@ void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len) } /* - * Concatenates (partial) iovecs from src to the end of dst. + * Concatenates (partial) iovecs from src_iov to the end of dst. * It starts copying after skipping `soffset' bytes at the * beginning of src and adds individual vectors from src to * dst copies up to `sbytes' bytes total, or up to the end - * of src if it comes first. This way, it is okay to specify + * of src_iov if it comes first. This way, it is okay to specify * very large value for `sbytes' to indicate "up to the end * of src". * Only vector pointers are processed, not the actual data buffers. */ -void qemu_iovec_concat(QEMUIOVector *dst, - QEMUIOVector *src, size_t soffset, size_t sbytes) +void qemu_iovec_concat_iov(QEMUIOVector *dst, + struct iovec *src_iov, unsigned int src_cnt, + size_t soffset, size_t sbytes) { int i; size_t done; - struct iovec *siov = src->iov; assert(dst->nalloc != -1); - assert(src->size >= soffset); - for (i = 0, done = 0; done < sbytes && i < src->niov; i++) { - if (soffset < siov[i].iov_len) { - size_t len = MIN(siov[i].iov_len - soffset, sbytes - done); - qemu_iovec_add(dst, siov[i].iov_base + soffset, len); + for (i = 0, done = 0; done < sbytes && i < src_cnt; i++) { + if (soffset < src_iov[i].iov_len) { + size_t len = MIN(src_iov[i].iov_len - soffset, sbytes - done); + qemu_iovec_add(dst, src_iov[i].iov_base + soffset, len); done += len; soffset = 0; } else { - soffset -= siov[i].iov_len; + soffset -= src_iov[i].iov_len; } } - /* return done; */ + assert(soffset == 0); /* offset beyond end of src */ +} + +/* + * Concatenates (partial) iovecs from src to the end of dst. + * It starts copying after skipping `soffset' bytes at the + * beginning of src and adds individual vectors from src to + * dst copies up to `sbytes' bytes total, or up to the end + * of src if it comes first. This way, it is okay to specify + * very large value for `sbytes' to indicate "up to the end + * of src". + * Only vector pointers are processed, not the actual data buffers. + */ +void qemu_iovec_concat(QEMUIOVector *dst, + QEMUIOVector *src, size_t soffset, size_t sbytes) +{ + qemu_iovec_concat_iov(dst, src->iov, src->niov, soffset, sbytes); } void qemu_iovec_destroy(QEMUIOVector *qiov) -- 2.11.4.GIT