generate pytask from string and string from pytask (#188)

* pytask creation from bytestring: saving work

* pytask now works

* documentation and tests

* linting

* Lint and fix test case

src/common/lib/python/common_extension.c

@@ -68,6 +68,55 @@ PyObject *PyObjectID_make(object_id object_id) {
   return (PyObject *) result;
 }
 
+/**
+ * Convert a string to a Ray task specification Python object.
+ *
+ * This is called from Python like
+ *
+ * task = photon.task_from_string("...")
+ *
+ * @param task_string String representation of the task specification.
+ * @return Python task specification object.
+ */
+PyObject *PyTask_from_string(PyObject *self, PyObject *args) {
+  const char *data;
+  int size;
+  if (!PyArg_ParseTuple(args, "s#", &data, &size)) {
+    return NULL;
+  }
+  PyTask *result = PyObject_New(PyTask, &PyTaskType);
+  result = (PyTask *) PyObject_Init((PyObject *) result, &PyTaskType);
+  result->spec = malloc(size);
+  memcpy(result->spec, data, size);
+  /* TODO(pcm): Better error checking once we use flatbuffers. */
+  if (size != task_spec_size(result->spec)) {
+    PyErr_SetString(CommonError,
+                    "task_from_string: task specification string malformed");
+    return NULL;
+  }
+  return (PyObject *) result;
+}
+
+/**
+ * Convert a Ray task specification Python object to a string.
+ *
+ * This is called from Python like
+ *
+ * s = photon.task_to_string(task)
+ *
+ * @param task Ray task specification Python object.
+ * @return String representing the task specification.
+ */
+PyObject *PyTask_to_string(PyObject *self, PyObject *args) {
+  PyObject *arg;
+  if (!PyArg_ParseTuple(args, "O", &arg)) {
+    return NULL;
+  }
+  PyTask *task = (PyTask *) arg;
+  return PyBytes_FromStringAndSize((char *) task->spec,
+                                   task_spec_size(task->spec));
+}
+
 static PyObject *PyObjectID_id(PyObject *self) {
   PyObjectID *s = (PyObjectID *) self;
   return PyBytes_FromStringAndSize((char *) &s->object_id.id[0],

src/common/lib/python/common_extension.h

@@ -39,6 +39,9 @@ PyObject *PyObjectID_make(object_id object_id);
 
 PyObject *check_simple_value(PyObject *self, PyObject *args);
 
+PyObject *PyTask_to_string(PyObject *, PyObject *args);
+PyObject *PyTask_from_string(PyObject *, PyObject *args);
+
 PyObject *compute_put_id(PyObject *self, PyObject *args);
 
 PyObject *PyTask_make(task_spec *task_spec);

src/common/lib/python/common_module.c

@@ -7,6 +7,11 @@ static PyMethodDef common_methods[] = {
      "Should the object be passed by value?"},
     {"compute_put_id", compute_put_id, METH_VARARGS,
      "Return the object ID for a put call within a task."},
+    {"task_from_string", PyTask_from_string, METH_VARARGS,
+     "Creates a Python PyTask object from a string representation of "
+     "task_spec."},
+    {"task_to_string", PyTask_to_string, METH_VARARGS,
+     "Translates a PyTask python object to a byte string."},
     {NULL} /* Sentinel */
 };
 

src/common/test/test.py

@@ -112,7 +112,18 @@ class TestObjectID(unittest.TestCase):
 
 class TestTask(unittest.TestCase):
 
-  def test_create_task(self):
+  def check_task(self, task, function_id, num_return_vals, args):
+    self.assertEqual(function_id.id(), task.function_id().id())
+    retrieved_args = task.arguments()
+    self.assertEqual(num_return_vals, len(task.returns()))
+    self.assertEqual(len(args), len(retrieved_args))
+    for i in range(len(retrieved_args)):
+      if isinstance(retrieved_args[i], common.ObjectID):
+        self.assertEqual(retrieved_args[i].id(), args[i].id())
+      else:
+        self.assertEqual(retrieved_args[i], args[i])
+
+  def test_create_and_serialize_task(self):
     # TODO(rkn): The function ID should be a FunctionID object, not an ObjectID.
     parent_id = random_task_id()
     function_id = random_function_id()
@@ -146,15 +157,10 @@ class TestTask(unittest.TestCase):
     for args in args_list:
       for num_return_vals in [0, 1, 2, 3, 5, 10, 100]:
         task = common.Task(function_id, args, num_return_vals, parent_id, 0)
-        self.assertEqual(function_id.id(), task.function_id().id())
-        retrieved_args = task.arguments()
-        self.assertEqual(num_return_vals, len(task.returns()))
-        self.assertEqual(len(args), len(retrieved_args))
-        for i in range(len(retrieved_args)):
-          if isinstance(retrieved_args[i], common.ObjectID):
-            self.assertEqual(retrieved_args[i].id(), args[i].id())
-          else:
-            self.assertEqual(retrieved_args[i], args[i])
+        self.check_task(task, function_id, num_return_vals, args)
+        data = common.task_to_string(task)
+        task2 = common.task_from_string(data)
+        self.check_task(task2, function_id, num_return_vals, args)
 
 if __name__ == "__main__":
   unittest.main(verbosity=2)

src/photon/photon_extension.c

@@ -135,6 +135,11 @@ static PyMethodDef photon_methods[] = {
      "Should the object be passed by value?"},
     {"compute_put_id", compute_put_id, METH_VARARGS,
      "Return the object ID for a put call within a task."},
+    {"task_from_string", PyTask_from_string, METH_VARARGS,
+     "Creates a Python PyTask object from a string representation of "
+     "task_spec."},
+    {"task_to_string", PyTask_to_string, METH_VARARGS,
+     "Translates a PyTask python object to a byte string."},
     {NULL} /* Sentinel */
 };