char: io_channel_send: don't lose written bytes

The g_io_channel_write_chars() documentation states,

  bytes_written: The number of bytes written. This can be nonzero even if
                 the return value is not G_IO_STATUS_NORMAL. [...]

io_channel_send() could lose such bytes before.

Furthermore, the (status == G_IO_STATUS_EOF) condition used to evaluate to
constant false whenever it was reached. When that condition actually held,
it always led to -1 / EINVAL. This patch (almost) distinguishes
G_IO_STATUS_EOF only when no bytes have been written, and then treats it
as an error.
Signed-off-by: NLaszlo Ersek <lersek@redhat.com>
Reviewed-by: NAmit Shah <amit.shah@redhat.com>
Reviewed-by: NAnthony Liguori <aliguori@us.ibm.com>
Message-id: 1373998781-29561-2-git-send-email-lersek@redhat.com
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

qemu-char.c

@@ -720,35 +720,32 @@ static GIOChannel *io_channel_from_socket(int fd)
 
 static int io_channel_send(GIOChannel *fd, const void *buf, size_t len)
 {
-    GIOStatus status;
-    size_t offset;
+    size_t offset = 0;
+    GIOStatus status = G_IO_STATUS_NORMAL;
 
-    offset = 0;
-    while (offset < len) {
-        gsize bytes_written;
+    while (offset < len && status == G_IO_STATUS_NORMAL) {
+        gsize bytes_written = 0;
 
         status = g_io_channel_write_chars(fd, buf + offset, len - offset,
                                           &bytes_written, NULL);
-        if (status != G_IO_STATUS_NORMAL) {
-            if (status == G_IO_STATUS_AGAIN) {
-                /* If we've written any data, return a partial write. */
-                if (offset) {
-                    break;
-                }
-                errno = EAGAIN;
-            } else {
-                errno = EINVAL;
-            }
-
-            return -1;
-        } else if (status == G_IO_STATUS_EOF) {
-            break;
-        }
-
         offset += bytes_written;
     }
 
-    return offset;
+    if (offset > 0) {
+        return offset;
+    }
+    switch (status) {
+    case G_IO_STATUS_NORMAL:
+        g_assert(len == 0);
+        return 0;
+    case G_IO_STATUS_AGAIN:
+        errno = EAGAIN;
+        return -1;
+    default:
+        break;
+    }
+    errno = EINVAL;
+    return -1;
 }
 
 #ifndef _WIN32