allow qemu_iovec_from_buffer() to specify offset from which to start copying

Similar to
 qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
                   int c, size_t bytes);
the new prototype is:
 qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
                     const void *buf, size_t bytes);

The processing starts at offset bytes within qiov.

This way, we may copy a bounce buffer directly to
a middle of qiov.

This is exactly the same function as iov_from_buf() from
iov.c, so use the existing implementation and rename it
to qemu_iovec_from_buf() to be shorter and to match the
utility function.

As with utility implementation, we now assert that the
offset is inside actual iovec.  Nothing changed for
current callers, because `offset' parameter is new.

While at it, stop using "bounce-qiov" in block/qcow2.c
and copy decrypted data directly from cluster_data
instead of recreating a temp qiov for doing that.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

1 files changed, 2 insertions, 1 deletions

diff --git a/qemu-common.h b/qemu-common.h
index e752d2b6c1..430ec15a44 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -346,7 +346,8 @@ void qemu_iovec_concat(QEMUIOVector *dst, QEMUIOVector *src, size_t size);
 void qemu_iovec_destroy(QEMUIOVector *qiov);
 void qemu_iovec_reset(QEMUIOVector *qiov);
 void qemu_iovec_to_buffer(QEMUIOVector *qiov, void *buf);
-void qemu_iovec_from_buffer(QEMUIOVector *qiov, const void *buf, size_t count);
+size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
+                           const void *buf, size_t bytes);
 size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
                          int fillc, size_t bytes);