iov: Introduce a new file for helpers around iovs, add iov_from_buf()

The virtio-net code uses iov_fill() which fills an iov from a linear
buffer. The virtio-serial-bus code does something similar in an
open-coded function.

Create a new iov.c file that has iov_from_buf().

Convert virtio-net and virtio-serial-bus over to use this functionality.
virtio-net used ints to hold sizes, the new function is going to use
size_t types.

Later commits will add the opposite functionality -- going from an iov
to a linear buffer.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/hw/iov.c b/hw/iov.c
new file mode 100644
index 0000000..07bd499
--- /dev/null
+++ b/hw/iov.c
@@ -0,0 +1,33 @@
+/*
+ * Helpers for getting linearized buffers from iov / filling buffers into iovs
+ *
+ * Copyright IBM, Corp. 2007, 2008
+ * Copyright (C) 2010 Red Hat, Inc.
+ *
+ * Author(s):
+ *  Anthony Liguori <aliguori@us.ibm.com>
+ *  Amit Shah <amit.shah@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ */
+
+#include "iov.h"
+
+size_t iov_from_buf(struct iovec *iov, unsigned int iovcnt,
+                    const void *buf, size_t size)
+{
+    size_t offset;
+    unsigned int i;
+
+    offset = 0;
+    for (i = 0; offset < size && i < iovcnt; i++) {
+        size_t len;
+
+        len = MIN(iov[i].iov_len, size - offset);
+
+        memcpy(iov[i].iov_base, buf + offset, len);
+        offset += len;
+    }
+    return offset;
+}