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>

Makefile

@@ -124,6 +124,8 @@ curses.o: curses.c keymaps.h curses_keys.h
 
 bt-host.o: QEMU_CFLAGS += $(BLUEZ_CFLAGS)
 
+iov.o: iov.c iov.h
+
 ######################################################################
 
 qemu-img.o: qemu-img-cmds.h

Makefile.objs

@@ -100,6 +100,7 @@ common-obj-y += keymaps.o
 common-obj-$(CONFIG_SDL) += sdl.o sdl_zoom.o x_keymap.o
 common-obj-$(CONFIG_CURSES) += curses.o
 common-obj-y += vnc.o acl.o d3des.o
+common-obj-y += iov.o
 common-obj-$(CONFIG_VNC_TLS) += vnc-tls.o vnc-auth-vencrypt.o
 common-obj-$(CONFIG_VNC_SASL) += vnc-auth-sasl.o
 common-obj-$(CONFIG_COCOA) += cocoa.o

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;
+}

hw/iov.h

@@ -0,0 +1,16 @@
+/*
+ * Helpers for getting linearized buffers from iov / filling buffers into iovs
+ *
+ * Copyright (C) 2010 Red Hat, Inc.
+ *
+ * Author(s):
+ *  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 "qemu-common.h"
+
+size_t iov_from_buf(struct iovec *iov, unsigned int iovcnt,
+                    const void *buf, size_t size);

hw/virtio-net.c

@@ -11,6 +11,7 @@
  *
  */
 
+#include "iov.h"
 #include "virtio.h"
 #include "net.h"
 #include "net/checksum.h"
@@ -445,21 +446,6 @@ static void work_around_broken_dhclient(struct virtio_net_hdr *hdr,
     }
 }
 
-static int iov_fill(struct iovec *iov, int iovcnt, const void *buf, int count)
-{
-    int offset, i;
-
-    offset = i = 0;
-    while (offset < count && i < iovcnt) {
-        int len = MIN(iov[i].iov_len, count - offset);
-        memcpy(iov[i].iov_base, buf + offset, len);
-        offset += len;
-        i++;
-    }
-
-    return offset;
-}
-
 static int receive_header(VirtIONet *n, struct iovec *iov, int iovcnt,
                           const void *buf, size_t size, size_t hdr_len)
 {
@@ -595,8 +581,8 @@ static ssize_t virtio_net_receive(VLANClientState *nc, const uint8_t *buf, size_
         }
 
         /* copy in packet.  ugh */
-        len = iov_fill(sg, elem.in_num,
-                       buf + offset, size - offset);
+        len = iov_from_buf(sg, elem.in_num,
+                           buf + offset, size - offset);
         total += len;
 
         /* signal other side */

hw/virtio-serial-bus.c

@@ -15,6 +15,7 @@
  * the COPYING file in the top-level directory.
  */
 
+#include "iov.h"
 #include "monitor.h"
 #include "qemu-queue.h"
 #include "sysbus.h"
@@ -84,27 +85,25 @@ static size_t write_to_port(VirtIOSerialPort *port,
 {
     VirtQueueElement elem;
     VirtQueue *vq;
-    size_t offset = 0;
-    size_t len = 0;
+    size_t offset;
 
     vq = port->ivq;
     if (!virtio_queue_ready(vq)) {
         return 0;
     }
 
+    offset = 0;
     while (offset < size) {
-        int i;
+        size_t len;
 
         if (!virtqueue_pop(vq, &elem)) {
             break;
         }
 
-        for (i = 0; offset < size && i < elem.in_num; i++) {
-            len = MIN(elem.in_sg[i].iov_len, size - offset);
+        len = iov_from_buf(elem.in_sg, elem.in_num,
+                           buf + offset, size - offset);
+        offset += len;
 
-            memcpy(elem.in_sg[i].iov_base, buf + offset, len);
-            offset += len;
-        }
         virtqueue_push(vq, &elem, len);
     }