[pygobject/wip/gio-async-awaitable-return: 1/4] async: Add a new async type that is an awaitable for a _finnish call

[Benjamin Berg <bberg src gnome org>]

commit a2fa286ffbb35edd3e4fb6861227d07892fc066e
Author: Benjamin Berg <bberg redhat com>
Date:   Fri Nov 13 00:19:47 2020 +0100

    async: Add a new async type that is an awaitable for a _finnish call

 gi/gimodule.c   |   3 +
 gi/meson.build  |   1 +
 gi/pygi-async.c | 225 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 gi/pygi-async.h |  60 +++++++++++++++
 4 files changed, 289 insertions(+)
---
diff --git a/gi/gimodule.c b/gi/gimodule.c
index 0901e738..8eb5cc35 100644
--- a/gi/gimodule.c
+++ b/gi/gimodule.c
@@ -34,6 +34,7 @@
 #include "pygi-error.h"
 #include "pygi-foreign.h"
 #include "pygi-resulttuple.h"
+#include "pygi-async.h"
 #include "pygi-source.h"
 #include "pygi-ccallback.h"
 #include "pygi-closure.h"
@@ -2557,6 +2558,8 @@ PYGI_MODINIT_FUNC PyInit__gi(void) {
         return NULL;
     if (pygi_resulttuple_register_types (module) < 0)
         return NULL;
+    if (pygi_async_register_types (module) < 0)
+        return NULL;
 
     if (pygi_spawn_register_types (module_dict) < 0)
         return NULL;
diff --git a/gi/meson.build b/gi/meson.build
index 8edf8328..7eb3311e 100644
--- a/gi/meson.build
+++ b/gi/meson.build
@@ -17,6 +17,7 @@ sources = [
   'pygi-source.c',
   'pygi-argument.c',
   'pygi-resulttuple.c',
+  'pygi-async.c',
   'pygi-type.c',
   'pygi-boxed.c',
   'pygi-closure.c',
diff --git a/gi/pygi-async.c b/gi/pygi-async.c
new file mode 100644
index 00000000..432ca9c5
--- /dev/null
+++ b/gi/pygi-async.c
@@ -0,0 +1,225 @@
+/* -*- Mode: C; c-basic-offset: 4 -*-
+ * vim: tabstop=4 shiftwidth=4 expandtab
+ *
+ * Copyright (C) 2015 Christoph Reiter <reiter christoph gmail com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <Python.h>
+#include <structmember.h>
+#include <glib.h>
+#include "pygi-async.h"
+#include "pygi-util.h"
+#include "pygi-info.h"
+
+/* This is never instantiated. */
+PYGI_DEFINE_TYPE ("gi._gi.AsyncBase", PyGIAsyncBase_Type, PyObject)
+
+/**
+ * Async.__repr__() implementation.
+ * Takes the _Async.__repr_format format string and applies the finish function
+ * info to it.
+ */
+static PyObject*
+async_repr(PyObject *self) {
+    PyObject *string;
+
+    string =PyUnicode_FromString ("gi.Async(finish_func=blub)");
+
+    return string;
+}
+
+/**
+ * async_cancel:
+ *
+ * Cancel the asynchronous operation.
+ */
+static PyObject *
+async_cancel(PyGIAsync *self) {
+
+    //g_cancellable_cancel (self);
+
+    Py_INCREF (Py_None);
+    return Py_None;
+}
+
+static int
+async_init(PyGIAsync *self, PyObject *args, PyObject *kwargs)
+{
+    static char *kwlist[] = { NULL };
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "", kwlist, NULL))
+        return -1;
+
+    return 0;
+}
+
+static PyMethodDef async_methods[] = {
+    {"cancel", (PyCFunction)async_cancel, METH_NOARGS},
+    {NULL, NULL, 0},
+};
+
+static PyObject *
+async_await (PyObject *self)
+{
+    PyObject *res;
+    PyObject *selfseq = Py_BuildValue ("(O)", self);
+
+    res = PySeqIter_New (selfseq);
+
+    Py_DECREF (selfseq);
+
+    return res;
+}
+
+
+static PyAsyncMethods async_async_methods = {
+    .am_await = async_await,
+};
+
+static void
+async_dealloc(PyGIAsync *self)
+{
+    /* Deallocate the cancellable member? */
+    Py_CLEAR(self->cancellable);
+
+    PyObject_DEL(self);
+}
+
+
+void
+pygi_async_finish_cb (GObject *source_object, gpointer res, PyGIAsync *async)
+{
+    g_print ("async routine finished!\n");
+
+    Py_DECREF(async);
+}
+
+/**
+ * PyGIAsyncType_type.tp_getattro implementation.
+ * Exists solely to return the finish_func of the class.
+ */
+static PyObject*
+asynctype_getattro(PyObject *self, PyObject *name) {
+
+    if (PyUnicode_Check (name) && PyUnicode_CompareWithASCIIString (name, "finish_func") == 0) {
+        PyGIAsyncType *type = (PyGIAsyncType *) PyObject_Type(self);
+
+        Py_INCREF (type->async_finish);
+        return type->async_finish;
+    }
+
+    return PyGIAsyncBase_Type.tp_getattro (self, name);
+}
+
+/**
+ * pygi_async_new_type:
+ * @async_finish: A #GIFunctionInfo to wrap that is used to finish.
+ *
+ * Creates a result type for a pending asynchronous operation of a specific
+ * async function. This works by finding the corresponding finish function,
+ * and checking that it is compatible. If it is, a new type will be returned
+ * that can be cached for future use.
+ *
+ * Returns: A new PyGIAsyncType PyTypeObject of type PyGIAsyncType_Type
+ *    or %NULL in case of an error.
+ */
+PyTypeObject*
+pygi_async_new_type(GIFunctionInfo *async_finish) {
+    PyGIAsyncType *new_type;
+    struct PyMemberDef members[] = {
+        {
+            "cancellable",
+            T_OBJECT,
+            offsetof(PyGIAsync, cancellable),
+            READONLY,
+            "The cancellable."
+        },
+        {NULL, }
+    };
+    PyType_Slot slots[] = {
+        { Py_tp_members, members },
+        { Py_tp_getattro, asynctype_getattro },
+        { 0, NULL}
+    };
+    PyType_Spec typespec = {
+        .name = "gi._Async",
+        .basicsize = sizeof(PyGIAsyncType),
+        .itemsize = sizeof(PyGIAsync),
+        .flags = Py_TPFLAGS_DEFAULT, /* We don't allow subclassing */
+        .slots = slots,
+    };
+    PyObject *bases;
+
+    g_assert (async_finish != NULL);
+
+    bases = Py_BuildValue ("(O)", &PyGIAsyncBase_Type);
+    new_type = (PyGIAsyncType*) PyType_FromSpecWithBases (&typespec, bases);
+    Py_DECREF(bases);
+
+    if (!new_type)
+        return NULL;
+
+    new_type->async_finish = _pygi_info_new ((GIBaseInfo *) async_finish);
+
+
+    return (PyTypeObject *) new_type;
+}
+
+
+/**
+ * pygi_async_new:
+ * @subclass: A PyGIAsyncType_Type subclass which will be the type of the
+ *    returned instance.
+ *
+ * Return a new async instance.
+ *
+ * Returns: An instance of @subclass or %NULL on error.
+ */
+PyObject *
+pygi_async_new(PyTypeObject *subclass) {
+
+    return subclass->tp_alloc (subclass, 0);
+}
+
+/**
+ * pygi_async_register_types:
+ * @module: A Python modules to which Async gets added to.
+ *
+ * Initializes the Async class and adds it to the passed @module.
+ *
+ * Returns: -1 on error, 0 on success.
+ */
+int pygi_async_register_types(PyObject *module) {
+
+    PyGIAsyncBase_Type.tp_dealloc = (destructor)async_dealloc;
+    PyGIAsyncBase_Type.tp_repr = (reprfunc)async_repr;
+    PyGIAsyncBase_Type.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE;
+    PyGIAsyncBase_Type.tp_methods = async_methods;
+    PyGIAsyncBase_Type.tp_as_async = &async_async_methods;
+    PyGIAsyncBase_Type.tp_init = (initproc)async_init;
+
+    if (PyType_Ready (&PyGIAsyncBase_Type) < 0)
+        return -1;
+
+    Py_INCREF (&PyGIAsyncBase_Type);
+    if (PyModule_AddObject (module, "AsyncBase",
+                            (PyObject *)&PyGIAsyncBase_Type) < 0) {
+        Py_DECREF (&PyGIAsyncBase_Type);
+        return -1;
+    }
+
+    return 0;
+}
diff --git a/gi/pygi-async.h b/gi/pygi-async.h
new file mode 100644
index 00000000..d9b0e94e
--- /dev/null
+++ b/gi/pygi-async.h
@@ -0,0 +1,60 @@
+/* -*- Mode: C; c-basic-offset: 4 -*-
+ * vim: tabstop=4 shiftwidth=4 expandtab
+ *
+ * Copyright (C) 2015 Christoph Reiter <reiter christoph gmail com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __PYGI_ASYNC_H__
+#define __PYGI_ASYNC_H__
+
+#include "Python.h"
+
+#include "pygi-cache.h"
+
+typedef struct {
+    PyTypeObject type_object;
+
+    /* All we need to know is how we can call the finish function and
+     * how to cancel the operation.
+     * We keep the async_finish information around solely to provide it as
+     * a read only member.
+     */
+    PyObject *async_finish;
+    PyGIFunctionCache *async_finish_cache;
+} PyGIAsyncType;
+
+typedef struct {
+    PyTypeObject type_object;
+
+    /* Here we only need the cancellable, callbacks, etc.
+     */
+    PyObject *cancellable;
+} PyGIAsync;
+
+
+int
+pygi_async_register_types (PyObject *d);
+
+void
+pygi_async_finish_cb (GObject *source_object, gpointer res, PyGIAsync *async);
+
+PyTypeObject *
+pygi_async_new_type       (GIFunctionInfo *async_finish);
+
+PyObject*
+pygi_async_new            (PyTypeObject *subclass);
+
+#endif /* __PYGI_ASYNCRESULT_H__ */