iov: Add helper to find skip over first n bytes of an io vector

Several of the IOV functions in iov.c, and also tap_send_frames_passt()
needs to determine which buffer element a byte offset into an IO vector
lies in.  Split this out into a helper function iov_skip_bytes().

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/iov.h b/iov.h
index ee35a75..e1becde 100644
--- a/iov.h
+++ b/iov.h
@@ -18,6 +18,8 @@
 #include <unistd.h>
 #include <string.h>
 
+size_t iov_skip_bytes(const struct iovec *iov, size_t n,
+		      size_t vec_offset, size_t *buf_offset);
 size_t iov_from_buf(const struct iovec *iov, size_t iov_cnt,
                     size_t offset, const void *buf, size_t bytes);
 size_t iov_to_buf(const struct iovec *iov, size_t iov_cnt,