python/lock.cc: Introduce apt_pkg.SystemLock context manager.

This is the new alternative to pkgsystem_lock() and pkgsystem_unlock(),
and is the recommended one.

4 files changed, 126 insertions, 1 deletions

diff --git a/python/apt_pkgmodule.cc b/python/apt_pkgmodule.cc
index cbf88294..d4c23d2f 100644
--- a/python/apt_pkgmodule.cc
+++ b/python/apt_pkgmodule.cc
@@ -651,6 +651,7 @@ extern "C" void initapt_pkg()
    ADDTYPE(Module,"AcquireProgress",&PyAcquireProgress_Type);
    ADDTYPE(Module,"AcquireItemDesc",&PyAcquireItemDesc_Type);
    ADDTYPE(Module,"CdromProgress",&PyCdromProgress_Type);
+   ADDTYPE(Module,"SystemLock",&PySystemLock_Type);
    // Tag file constants
    PyModule_AddObject(Module,"REWRITE_PACKAGE_ORDER",
                       CharCharToList(TFRewritePackageOrder));
diff --git a/python/apt_pkgmodule.h b/python/apt_pkgmodule.h
index 1277ab60..de70c056 100644
--- a/python/apt_pkgmodule.h
+++ b/python/apt_pkgmodule.h
@@ -117,6 +117,7 @@ extern PyTypeObject PyAcquireProgress_Type;
 extern PyTypeObject PyCdromProgress_Type;
 extern PyTypeObject PyAcquireItemDesc_Type;
 extern PyTypeObject PyAcquireWorker_Type;
+extern PyTypeObject PySystemLock_Type;
 #include "python-apt.h"
 #endif
 
diff --git a/python/lock.cc b/python/lock.cc
new file mode 100644
index 00000000..aac2d25a
--- /dev/null
+++ b/python/lock.cc
@@ -0,0 +1,123 @@
+/*
+ * lock.cc - Context managers for implementing locking.
+ *
+ * Copyright 2009 Julian Andres Klode <jak@debian.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301, USA.
+ */
+#include <apt-pkg/init.h>
+#include <apt-pkg/error.h>
+#include <Python.h>
+#include "generic.h"
+
+static PyObject *systemlock_exit(PyObject *self, PyObject *args)
+{
+
+    PyObject *exc_type = 0;
+    PyObject *exc_value = 0;
+    PyObject *traceback = 0;
+    if (!PyArg_UnpackTuple(args, "__exit__", 3, 3, &exc_type, &exc_value,
+                           &traceback)) {
+        return 0;
+    }
+    if ((! exc_type || exc_type == Py_None) && _system->UnLock() == 0) {
+        return HandleErrors();
+    }
+    Py_RETURN_FALSE;
+}
+
+static PyObject *systemlock_enter(PyObject *self, PyObject *args)
+{
+    if (!PyArg_ParseTuple(args, ""))
+        return NULL;
+    if (!_system->Lock())
+        return HandleErrors();
+    return self;
+}
+
+static PyObject *systemlock_new(PyTypeObject *type, PyObject *args,
+                                PyObject *kwds)
+{
+    if (_system == 0) {
+        PyErr_SetString(PyExc_ValueError,"_system not initialized");
+        return 0;
+    }
+    return PyType_GenericNew(type,args,kwds);
+}
+
+static PyMethodDef systemlock_methods[] = {
+    {"__enter__",systemlock_enter,METH_VARARGS,"Lock the system."},
+    {"__exit__",systemlock_exit,METH_VARARGS,"Unlock the system."},
+    {NULL}
+};
+
+static char *systemlock_doc = "SystemLock()\n\n"
+    "Context manager for locking the package system. The lock is established\n"
+    "as soon as the method __enter__() is called. It is released when\n"
+    "__exit__() is called.\n\n"
+    "This should be used via the 'with' statement, e.g.::\n\n"
+    "   with apt_pkg.SystemLock():\n"
+    "       ...\n\n"
+    "Once the block is left, the lock is released automatically. The object\n"
+    "can be used multiple times::\n\n"
+    "   lock = apt_pkg.SystemLock()\n"
+    "   with lock:\n"
+    "       ...\n"
+    "   with lock:\n"
+    "       ...\n\n";
+
+PyTypeObject PySystemLock_Type = {
+    PyVarObject_HEAD_INIT(&PyType_Type, 0)
+    "apt_pkg.SystemLock",                // tp_name
+    0,                                   // tp_basicsize
+    0,                                   // tp_itemsize
+    // Methods
+    0,                                   // tp_dealloc
+    0,                                   // tp_print
+    0,                                   // tp_getattr
+    0,                                   // tp_setattr
+    0,                                   // tp_compare
+    0,                                   // tp_repr
+    0,                                   // tp_as_number
+    0,                                   // tp_as_sequence
+    0,                                   // tp_as_mapping
+    0,                                   // tp_hash
+    0,                                   // tp_call
+    0,                                   // tp_str
+    0,                                   // tp_getattro
+    0,                                   // tp_setattro
+    0,                                   // tp_as_buffer
+    (Py_TPFLAGS_DEFAULT |                // tp_flags
+     Py_TPFLAGS_BASETYPE),
+    systemlock_doc,                      // tp_doc
+    0,                                   // tp_traverse
+    0,                                   // tp_clear
+    0,                                   // tp_richcompare
+    0,                                   // tp_weaklistoffset
+    0,                                   // tp_iter
+    0,                                   // tp_iternext
+    systemlock_methods,                  // tp_methods
+    0,                                   // tp_members
+    0,                                   // tp_getset
+    0,                                   // tp_base
+    0,                                   // tp_dict
+    0,                                   // tp_descr_get
+    0,                                   // tp_descr_set
+    0,                                   // tp_dictoffset
+    0,                                   // tp_init
+    0,                                   // tp_alloc
+    systemlock_new,                      // tp_new
+};
diff --git a/setup.py b/setup.py
index 5cfe3bdc..e07bd83b 100644
--- a/setup.py
+++ b/setup.py
@@ -35,7 +35,7 @@ files = ['apt_pkgmodule.cc', 'acquire.cc', 'cache.cc', 'cdrom.cc',
          'hashstring.cc', 'indexfile.cc', 'indexrecords.cc', 'metaindex.cc',
          'pkgmanager.cc', 'pkgrecords.cc', 'pkgsrcrecords.cc', 'policy.cc',
          'progress.cc', 'sourcelist.cc', 'string.cc', 'tag.cc',
-         'opprogress.cc', 'acquireprogress.cc', 'cdromprogress.cc']
+         'opprogress.cc', 'acquireprogress.cc', 'cdromprogress.cc', 'lock.cc']
 files = sorted(['python/' + fname for fname in files])
 apt_pkg = Extension("apt_pkg", files, libraries=["apt-pkg"])