io: add ability to associate an opaque "result" with with a task

Currently there is no data associated with a successful
task completion. This adds an opaque pointer to the task
to store an arbitrary result.
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

include/io/task.h

@@ -239,6 +239,33 @@ void qio_task_abort(QIOTask *task,
                     Error *err);
 
 
+/**
+ * qio_task_set_result_pointer:
+ * @task: the task struct
+ * @result: pointer to the result data
+ *
+ * Associate an opaque result with the task,
+ * which can later be retrieved with the
+ * qio_task_get_result_pointer() method
+ *
+ */
+void qio_task_set_result_pointer(QIOTask *task,
+                                 gpointer result,
+                                 GDestroyNotify notify);
+
+
+/**
+ * qio_task_get_result_pointer:
+ * @task: the task struct
+ *
+ * Retrieve the opaque result data associated
+ * with the task, if any.
+ *
+ * Returns: the task result, or NULL
+ */
+gpointer qio_task_get_result_pointer(QIOTask *task);
+
+
 /**
  * qio_task_get_source:
  * @task: the task struct

io/task.c

@@ -29,6 +29,8 @@ struct QIOTask {
     QIOTaskFunc func;
     gpointer opaque;
     GDestroyNotify destroy;
+    gpointer result;
+    GDestroyNotify destroyResult;
 };
 
 
@@ -57,6 +59,9 @@ static void qio_task_free(QIOTask *task)
     if (task->destroy) {
         task->destroy(task->opaque);
     }
+    if (task->destroyResult) {
+        task->destroyResult(task->result);
+    }
     object_unref(task->source);
 
     g_free(task);
@@ -154,6 +159,21 @@ void qio_task_abort(QIOTask *task,
 }
 
 
+void qio_task_set_result_pointer(QIOTask *task,
+                                 gpointer result,
+                                 GDestroyNotify destroy)
+{
+    task->result = result;
+    task->destroyResult = destroy;
+}
+
+
+gpointer qio_task_get_result_pointer(QIOTask *task)
+{
+    return task->result;
+}
+
+
 Object *qio_task_get_source(QIOTask *task)
 {
     return task->source;