util: virqemu: Introduce virQEMUBuildNetdevCommandlineFromJSON

In preparation for converting the generator of -netdev to generate JSON
which will be used to do the command line rather than the other way
around we need to introduce a convertor which properly configures
virQEMUBuildCommandLineJSON for the quirks of -netdev.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>

src/libvirt_private.syms

@@ -2915,6 +2915,7 @@ virQEMUBuildCommandLineJSON;
 virQEMUBuildCommandLineJSONArrayBitmap;
 virQEMUBuildCommandLineJSONArrayNumbered;
 virQEMUBuildDriveCommandlineFromJSON;
+virQEMUBuildNetdevCommandlineFromJSON;
 virQEMUBuildObjectCommandlineFromJSON;
 virQEMUBuildQemuImgKeySecretOpts;
 

src/util/virqemu.c

@@ -252,6 +252,28 @@ virQEMUBuildCommandLineJSON(virJSONValuePtr value,
 }
 
 
+/**
+ * virQEMUBuildNetdevCommandlineFromJSON:
+ * @props: JSON properties describing a netdev
+ *
+ * Converts @props into arguments for -netdev including all the quirks and
+ * differences between the monitor and command line syntax.
+ */
+char *
+virQEMUBuildNetdevCommandlineFromJSON(virJSONValuePtr props)
+{
+    const char *type = virJSONValueObjectGetString(props, "type");
+    g_auto(virBuffer) buf = VIR_BUFFER_INITIALIZER;
+
+    virBufferAsprintf(&buf, "%s,", type);
+
+    if (virQEMUBuildCommandLineJSON(props, &buf, "type", true, NULL) < 0)
+        return NULL;
+
+    return virBufferContentAndReset(&buf);
+}
+
+
 static int
 virQEMUBuildObjectCommandlineFromJSONInternal(virBufferPtr buf,
                                               const char *type,

src/util/virqemu.h

@@ -49,6 +49,9 @@ int virQEMUBuildCommandLineJSON(virJSONValuePtr value,
                                 bool onOff,
                                 virQEMUBuildCommandLineJSONArrayFormatFunc array);
 
+char *
+virQEMUBuildNetdevCommandlineFromJSON(virJSONValuePtr props);
+
 int virQEMUBuildObjectCommandlineFromJSON(virBufferPtr buf,
                                           virJSONValuePtr objprops);