mojo: Add a runloop utility in python

This is necessary to be able to use async operation on handles.

This is a reland of https://codereview.chromium.org/552783004 after the
build dependency issue has been fixed.

R=sdefresne@chromium.org
BUG=415485

Review URL: https://codereview.chromium.org/577193002

Cr-Commit-Position: refs/heads/master@{#295451}

mojo/mojo.gyp

@@ -566,10 +566,15 @@
           },
           'sources': [
             'public/python/mojo/c_core.pxd',
+            'public/python/mojo/c_environment.pxd',
             'public/python/mojo/system.pyx',
+            'public/python/src/python_system_helper.cc',
+            'public/python/src/python_system_helper.h',
           ],
           'dependencies': [
+            'mojo_base.gyp:mojo_environment_standalone',
             'mojo_base.gyp:mojo_system',
+            'mojo_base.gyp:mojo_utility',
           ],
           'includes': [ '../third_party/cython/cython_compiler.gypi' ],
         },

mojo/public/python/BUILD.gn

@@ -17,10 +17,17 @@ python_binary_module("system") {
   python_base_module = "mojo"
   sources = [
     "mojo/c_core.pxd",
+    "mojo/c_environment.pxd",
     "mojo/system.pyx",
   ]
+  additional_sources = [
+    "src/python_system_helper.cc",
+    "src/python_system_helper.h",
+  ]
   deps = [
     "//mojo/public/c/system",
+    "//mojo/public/cpp/environment:standalone",
+    "//mojo/public/cpp/utility",
     ":base",
   ]
 }

mojo/public/python/mojo/c_environment.pxd

+# Copyright 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# distutils: language = c++
+
+from libc.stdint cimport int64_t
+
+
+cdef extern from "mojo/public/cpp/bindings/callback.h" nogil:
+  cdef cppclass CClosure "mojo::Callback<void()>":
+    CClosure()
+
+
+cdef extern from "mojo/public/python/src/python_system_helper.h" \
+    namespace "mojo" nogil:
+  cdef CClosure BuildClosure(object)
+
+
+cdef extern from "mojo/public/cpp/utility/run_loop.h" nogil:
+  cdef cppclass CRunLoop "mojo::RunLoop":
+    CRunLoop()
+    void Run() except *
+    void RunUntilIdle() except *
+    void Quit()
+    void PostDelayedTask(CClosure& task, int64_t delay)
+
+cdef extern from "mojo/public/cpp/environment/environment.h" nogil:
+  cdef cppclass CEnvironment "mojo::Environment":
+    CEnvironment()

mojo/public/python/mojo/system.pyx

@@ -5,6 +5,8 @@
 # distutils language = c++
 
 cimport c_core
+cimport c_environment
+
 
 from cpython.buffer cimport PyBUF_CONTIG
 from cpython.buffer cimport PyBUF_CONTIG_RO
@@ -694,3 +696,32 @@ class DuplicateSharedBufferOptions(object):
 
   def __init__(self):
     self.flags = DuplicateSharedBufferOptions.FLAG_NONE
+
+
+cdef class RunLoop(object):
+  """RunLoop to use when using asynchronous operations on handles."""
+
+  cdef c_environment.CRunLoop c_run_loop
+
+  def Run(self):
+    """Run the runloop until Quit is called."""
+    self.c_run_loop.Run()
+
+  def RunUntilIdle(self):
+    """Run the runloop until Quit is called or no operation is waiting."""
+    self.c_run_loop.RunUntilIdle()
+
+  def Quit(self):
+    """Quit the runloop."""
+    self.c_run_loop.Quit()
+
+  def PostDelayedTask(self, runnable, delay=0):
+    """
+    Post a task on the runloop. This must be called from the thread owning the
+    runloop.
+    """
+    cdef c_environment.CClosure closure = c_environment.BuildClosure(runnable)
+    self.c_run_loop.PostDelayedTask(closure, delay)
+
+
+cdef c_environment.CEnvironment* _ENVIRONMENT = new c_environment.CEnvironment()

mojo/public/python/src/python_system_helper.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "mojo/public/python/src/python_system_helper.h"
+
+#include "Python.h"
+
+#include "mojo/public/cpp/environment/logging.h"
+#include "mojo/public/cpp/system/macros.h"
+#include "mojo/public/cpp/utility/run_loop.h"
+
+namespace {
+
+class ScopedGIL {
+ public:
+  ScopedGIL() {
+    state_ = PyGILState_Ensure();
+  }
+
+  ~ScopedGIL() {
+    PyGILState_Release(state_);
+  }
+
+ private:
+  PyGILState_STATE state_;
+
+  MOJO_DISALLOW_COPY_AND_ASSIGN(ScopedGIL);
+};
+
+class PythonClosure : public mojo::Closure::Runnable {
+ public:
+  PythonClosure(PyObject* callable) : callable_(callable) {
+    MOJO_CHECK(callable);
+    Py_XINCREF(callable);
+  }
+
+  virtual ~PythonClosure() {
+    ScopedGIL acquire_gil;
+    Py_DECREF(callable_);
+  }
+
+  virtual void Run() const MOJO_OVERRIDE {
+    ScopedGIL acquire_gil;
+    PyObject* empty_tuple = PyTuple_New(0);
+    if (!empty_tuple) {
+      mojo::RunLoop::current()->Quit();
+      return;
+    }
+
+    PyObject* result = PyObject_CallObject(callable_, empty_tuple);
+    Py_DECREF(empty_tuple);
+    if (result) {
+      Py_DECREF(result);
+    } else {
+      mojo::RunLoop::current()->Quit();
+      return;
+    }
+  }
+
+ private:
+  PyObject* callable_;
+
+  MOJO_DISALLOW_COPY_AND_ASSIGN(PythonClosure);
+};
+
+}  // namespace
+
+namespace mojo {
+
+Closure BuildClosure(PyObject* callable) {
+  if (!PyCallable_Check(callable))
+    return Closure();
+
+  return Closure(
+      static_cast<mojo::Closure::Runnable*>(new PythonClosure(callable)));
+}
+
+}  // namespace mojo

mojo/public/python/src/python_system_helper.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MOJO_PUBLIC_PYTHON_SRC_PYTHON_SYSTEM_HELPER_H_
+#define MOJO_PUBLIC_PYTHON_SRC_PYTHON_SYSTEM_HELPER_H_
+
+#include "Python.h"
+
+#include "mojo/public/cpp/bindings/callback.h"
+
+namespace mojo {
+
+// Create a mojo::Closure from a callable python object.
+mojo::Closure BuildClosure(PyObject* callable);
+
+// Initalize mojo::RunLoop
+void InitRunLoop();
+
+}  // namespace mojo
+
+#endif  // MOJO_PUBLIC_PYTHON_SRC_PYTHON_SYSTEM_HELPER_H_

mojo/python/tests/runloop_unittest.py

+# Copyright 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import unittest
+
+# pylint: disable=F0401
+import mojo.embedder
+from mojo import system
+
+
+def _Increment(array):
+  def _Closure():
+    array.append(0)
+  return _Closure
+
+
+class RunLoopTest(unittest.TestCase):
+
+  def setUp(self):
+    mojo.embedder.Init()
+
+  def testRunLoop(self):
+    loop = system.RunLoop()
+    array = []
+    for _ in xrange(10):
+      loop.PostDelayedTask(_Increment(array))
+    loop.RunUntilIdle()
+    self.assertEquals(len(array), 10)
+
+  def testRunLoopWithException(self):
+    loop = system.RunLoop()
+    def Throw():
+      raise Exception("error")
+    array = []
+    loop.PostDelayedTask(Throw)
+    loop.PostDelayedTask(_Increment(array))
+    with self.assertRaisesRegexp(Exception, '^error$'):
+      loop.Run()
+    self.assertEquals(len(array), 0)
+    loop.RunUntilIdle()
+    self.assertEquals(len(array), 1)

third_party/cython/rules.gni

@@ -72,6 +72,9 @@ template("python_binary_module") {
       datadeps = invoker.datadeps
     }
     sources = [ cython_output ]
+    if (defined(invoker.additional_sources)) {
+      sources += invoker.additional_sources
+    }
     configs += [ ":$config_name" ]
   }