File: //home/arjun/python-apt/python/lock.cc
/*
* 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 <Python.h>
#include <apt-pkg/init.h>
#include <apt-pkg/error.h>
#include <apt-pkg/fileutl.h>
#include <apt-pkg/pkgsystem.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 (_system->UnLock() == 0) {
// The unlock failed. If no exception happened within the suite, we
// will raise an error here. Otherwise, we just display the error, so
// Python can handle the original exception instead.
HandleErrors();
if (exc_type == Py_None)
return NULL;
else
PyErr_WriteUnraisable(self);
}
// Return False, as required by the context manager protocol.
Py_RETURN_FALSE;
}
static PyObject *systemlock_enter(PyObject *self, PyObject *args)
{
if (!PyArg_ParseTuple(args, ""))
return NULL;
if (!_system->Lock())
return HandleErrors();
Py_INCREF(self);
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, for example:\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
};
/**
* File Based locking.
*
* The counter is increased by every call to filelock_enter() and decreased by
* every call to filelock_exit(). When the counter reaches 0, the underlying
* file descriptor is closed.
*
* Members:
* @member char* filename The name of the file
* @member int lock_count How many times we have locked it.
* @member int fd The filedescriptor returned by GetLock() or 0.
*/
struct filelock_object {
PyObject_HEAD
char *filename;
int lock_count;
int fd;
};
static PyObject *filelock_enter(filelock_object *self, PyObject *args)
{
self->lock_count++;
// If we have no lock yet, get a lock.
if (self->lock_count == 1) {
self->fd = GetLock(self->filename, true);
if (self->fd == -1) {
self->lock_count--;
return HandleErrors();
}
}
Py_INCREF(self);
return (PyObject *)self;
}
static PyObject *filelock_exit(filelock_object *self, PyObject *args)
{
// Count down the lock_count, if it is less than 0, reset it to 0.
self->lock_count--;
if (self->lock_count < 0)
self->lock_count = 0;
if (self->lock_count == 0 && self->fd != 0 && close(self->fd) == -1) {
return PyErr_SetFromErrno(PyExc_OSError);
}
Py_RETURN_FALSE;
}
static PyObject *filelock_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
PyApt_Filename filename;
char *kwlist[] = {"filename", NULL};
if (PyArg_ParseTupleAndKeywords(args, kwds, "O&:__init__", kwlist,
PyApt_Filename::Converter,
&filename) == 0) {
return NULL;
}
filelock_object *self = (filelock_object *)type->tp_alloc(type, 0);
// Copy the string into the object.
self->filename = new char[strlen(filename) + 1];
strcpy(self->filename, filename);
return (PyObject *)self;
}
static void filelock_dealloc(filelock_object *self)
{
delete[] self->filename;
((PyObject*)self)->ob_type->tp_free(self);
}
static PyMethodDef filelock_methods[] = {
{"__enter__",(PyCFunction)filelock_enter,METH_VARARGS,"Lock the system."},
{"__exit__",(PyCFunction)filelock_exit,METH_VARARGS,"Unlock the system."},
{NULL}
};
static char *filelock_doc = "FileLock(filename: str)\n\n"
"Context manager for locking using a file. 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, for example:\n\n"
" with apt_pkg.FileLock(filename):\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.FileLock(filename)\n"
" with lock:\n"
" ...\n"
" with lock:\n"
" ...\n\n";
PyTypeObject PyFileLock_Type = {
PyVarObject_HEAD_INIT(&PyType_Type, 0)
"apt_pkg.FileLock", // tp_name
sizeof(filelock_object), // tp_basicsize
0, // tp_itemsize
// Methods
destructor(filelock_dealloc), // 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),
filelock_doc, // tp_doc
0, // tp_traverse
0, // tp_clear
0, // tp_richcompare
0, // tp_weaklistoffset
0, // tp_iter
0, // tp_iternext
filelock_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
filelock_new, // tp_new
};