win32: add readv/writev emulation

Commit e9d8fbf (qemu-file: do not use stdio for qemu_fdopen, 2013-03-27)
introduced a usage of writev, which mingw32 does not have.  Even though
qemu_fdopen itself is not used on mingw32, the future-proof solution is
to add an implementation of it.  This is simple and similar to how we
emulate sendmsg/recvmsg in util/iov.c.

Some files include osdep.h without qemu-common.h, so move the definition
of iovec to osdep.h too, and include osdep.h from qemu-common.h
unconditionally (protection against including files when NEED_CPU_H is
defined is not needed since the removal of AREG0).

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 43 insertions, 0 deletions

diff --git a/util/osdep.c b/util/osdep.c
index 6ae5aaf781..685c8ae889 100644
--- a/util/osdep.c
+++ b/util/osdep.c
@@ -429,3 +429,46 @@ int socket_init(void)
 #endif
     return 0;
 }
+
+#ifndef CONFIG_IOVEC
+/* helper function for iov_send_recv() */
+static ssize_t
+readv_writev(int fd, const struct iovec *iov, int iov_cnt, bool do_write)
+{
+    unsigned i = 0;
+    ssize_t ret = 0;
+    while (i < iov_cnt) {
+        ssize_t r = do_write
+            ? write(fd, iov[i].iov_base, iov[i].iov_len)
+            : read(fd, iov[i].iov_base, iov[i].iov_len);
+        if (r > 0) {
+            ret += r;
+        } else if (!r) {
+            break;
+        } else if (errno == EINTR) {
+            continue;
+        } else {
+            /* else it is some "other" error,
+             * only return if there was no data processed. */
+            if (ret == 0) {
+                ret = -1;
+            }
+            break;
+        }
+        i++;
+    }
+    return ret;
+}
+
+ssize_t
+readv(int fd, const struct iovec *iov, int iov_cnt)
+{
+    return readv_writev(fd, iov, iov_cnt, false);
+}
+
+ssize_t
+writev(int fd, const struct iovec *iov, int iov_cnt)
+{
+    return readv_writev(fd, iov, iov_cnt, true);
+}
+#endif