Modules/_multiprocessing/multiprocessing.c

/*
 * Extension module used by multiprocessing package
 *
 * multiprocessing.c
 *
 * Copyright (c) 2006-2008, R Oudkerk --- see COPYING.txt
 */

#include "multiprocessing.h"

#ifdef SCM_RIGHTS
	#define HAVE_FD_TRANSFER 1
#else
	#define HAVE_FD_TRANSFER 0
#endif

PyObject *create_win32_namespace(void);

PyObject *pickle_dumps, *pickle_loads, *pickle_protocol;
PyObject *ProcessError, *BufferTooShort;

/*
 * Function which raises exceptions based on error codes
 */

PyObject *
mp_SetError(PyObject *Type, int num)
{
	switch (num) {
#ifdef MS_WINDOWS
	case MP_STANDARD_ERROR: 
		if (Type == NULL)
			Type = PyExc_WindowsError;
		PyErr_SetExcFromWindowsErr(Type, 0);
		break;
	case MP_SOCKET_ERROR:
		if (Type == NULL)
			Type = PyExc_WindowsError;
		PyErr_SetExcFromWindowsErr(Type, WSAGetLastError());
		break;
#else /* !MS_WINDOWS */
	case MP_STANDARD_ERROR:
	case MP_SOCKET_ERROR:
		if (Type == NULL)
			Type = PyExc_OSError;
		PyErr_SetFromErrno(Type);
		break;
#endif /* !MS_WINDOWS */
	case MP_MEMORY_ERROR:
		PyErr_NoMemory();
		break;
	case MP_END_OF_FILE:
		PyErr_SetNone(PyExc_EOFError);
		break;
	case MP_EARLY_END_OF_FILE:
		PyErr_SetString(PyExc_IOError,
				"got end of file during message");
		break;
	case MP_BAD_MESSAGE_LENGTH:
		PyErr_SetString(PyExc_IOError, "bad message length");
		break;
	case MP_EXCEPTION_HAS_BEEN_SET:
		break;
	default:
		PyErr_Format(PyExc_RuntimeError,
			     "unkown error number %d", num);
	}
	return NULL;
}


/*
 * Windows only
 */

#ifdef MS_WINDOWS

/* On Windows we set an event to signal Ctrl-C; compare with timemodule.c */

HANDLE sigint_event = NULL;

static BOOL WINAPI
ProcessingCtrlHandler(DWORD dwCtrlType)
{
	SetEvent(sigint_event);
	return FALSE;
}

/*
 * Unix only
 */

#else /* !MS_WINDOWS */

#if HAVE_FD_TRANSFER

/* Functions for transferring file descriptors between processes.
   Reimplements some of the functionality of the fdcred
   module at http://www.mca-ltd.com/resources/fdcred_1.tgz. */

static PyObject *
multiprocessing_sendfd(PyObject *self, PyObject *args)
{
	int conn, fd, res;
	char dummy_char;
	char buf[CMSG_SPACE(sizeof(int))];
	struct msghdr msg = {0};
	struct iovec dummy_iov;
	struct cmsghdr *cmsg;

	if (!PyArg_ParseTuple(args, "ii", &conn, &fd))
		return NULL;

	dummy_iov.iov_base = &dummy_char;
	dummy_iov.iov_len = 1;
	msg.msg_control = buf;
	msg.msg_controllen = sizeof(buf);
	msg.msg_iov = &dummy_iov;
	msg.msg_iovlen = 1;
	cmsg = CMSG_FIRSTHDR(&msg);
	cmsg->cmsg_level = SOL_SOCKET;
	cmsg->cmsg_type = SCM_RIGHTS;
	cmsg->cmsg_len = CMSG_LEN(sizeof(int));
	msg.msg_controllen = cmsg->cmsg_len;
	*(int*)CMSG_DATA(cmsg) = fd;

	Py_BEGIN_ALLOW_THREADS
	res = sendmsg(conn, &msg, 0);
	Py_END_ALLOW_THREADS

	if (res < 0)
		return PyErr_SetFromErrno(PyExc_OSError);
	Py_RETURN_NONE;
}

static PyObject *
multiprocessing_recvfd(PyObject *self, PyObject *args)
{
	int conn, fd, res;
	char dummy_char;
	char buf[CMSG_SPACE(sizeof(int))];
	struct msghdr msg = {0};
	struct iovec dummy_iov;
	struct cmsghdr *cmsg;

	if (!PyArg_ParseTuple(args, "i", &conn))
		return NULL;

	dummy_iov.iov_base = &dummy_char;
	dummy_iov.iov_len = 1;
	msg.msg_control = buf;
	msg.msg_controllen = sizeof(buf);
	msg.msg_iov = &dummy_iov;
	msg.msg_iovlen = 1;
	cmsg = CMSG_FIRSTHDR(&msg);
	cmsg->cmsg_level = SOL_SOCKET;
	cmsg->cmsg_type = SCM_RIGHTS;
	cmsg->cmsg_len = CMSG_LEN(sizeof(int));
	msg.msg_controllen = cmsg->cmsg_len;

	Py_BEGIN_ALLOW_THREADS
	res = recvmsg(conn, &msg, 0);
	Py_END_ALLOW_THREADS

	if (res < 0)
		return PyErr_SetFromErrno(PyExc_OSError);

	fd = *(int*)CMSG_DATA(cmsg);
	return Py_BuildValue("i", fd);
}

#endif /* HAVE_FD_TRANSFER */

#endif /* !MS_WINDOWS */


/*
 * All platforms
 */

static PyObject*
multiprocessing_address_of_buffer(PyObject *self, PyObject *obj)
{
	void *buffer;
	Py_ssize_t buffer_len;

	if (PyObject_AsWriteBuffer(obj, &buffer, &buffer_len) < 0)
		return NULL;

	return Py_BuildValue("N" F_PY_SSIZE_T, 
			     PyLong_FromVoidPtr(buffer), buffer_len);
}


/*
 * Function table
 */

static PyMethodDef module_methods[] = {
	{"address_of_buffer", multiprocessing_address_of_buffer, METH_O, 
	 "address_of_buffer(obj) -> int\n" 
	 "Return address of obj assuming obj supports buffer inteface"},
#if HAVE_FD_TRANSFER
	{"sendfd", multiprocessing_sendfd, METH_VARARGS, 
	 "sendfd(sockfd, fd) -> None\n"
	 "Send file descriptor given by fd over the unix domain socket\n"
	 "whose file decriptor is sockfd"},
	{"recvfd", multiprocessing_recvfd, METH_VARARGS,
	 "recvfd(sockfd) -> fd\n"
	 "Receive a file descriptor over a unix domain socket\n"
	 "whose file decriptor is sockfd"},
#endif
	{NULL}
};


/*
 * Initialize
 */

PyMODINIT_FUNC
init_multiprocessing(void)
{
	PyObject *module, *temp, *value;

	/* Initialize module */
	module = Py_InitModule("_multiprocessing", module_methods);
	if (!module)
		return;

	/* Get copy of objects from pickle */
	temp = PyImport_ImportModule(PICKLE_MODULE);
	if (!temp)
		return;
	pickle_dumps = PyObject_GetAttrString(temp, "dumps");
	pickle_loads = PyObject_GetAttrString(temp, "loads");
	pickle_protocol = PyObject_GetAttrString(temp, "HIGHEST_PROTOCOL");
	Py_XDECREF(temp);

	/* Get copy of BufferTooShort */
	temp = PyImport_ImportModule("multiprocessing");
	if (!temp)
		return;
	BufferTooShort = PyObject_GetAttrString(temp, "BufferTooShort");
	Py_XDECREF(temp);

	/* Add connection type to module */
	if (PyType_Ready(&ConnectionType) < 0)
		return;
	Py_INCREF(&ConnectionType);	
	PyModule_AddObject(module, "Connection", (PyObject*)&ConnectionType);

#if defined(MS_WINDOWS) ||						\
  (defined(HAVE_SEM_OPEN) && !defined(HAVE_BROKEN_POSIX_SEMAPHORES))
	/* Add SemLock type to module */
	if (PyType_Ready(&SemLockType) < 0)
		return;
	Py_INCREF(&SemLockType);
	PyDict_SetItemString(SemLockType.tp_dict, "SEM_VALUE_MAX", 
			     Py_BuildValue("i", SEM_VALUE_MAX));
	PyModule_AddObject(module, "SemLock", (PyObject*)&SemLockType);   
#endif

#ifdef MS_WINDOWS
	/* Add PipeConnection to module */
	if (PyType_Ready(&PipeConnectionType) < 0)
		return;
	Py_INCREF(&PipeConnectionType);
	PyModule_AddObject(module, "PipeConnection",
			   (PyObject*)&PipeConnectionType);

	/* Initialize win32 class and add to multiprocessing */
	temp = create_win32_namespace();
	if (!temp)
		return;
	PyModule_AddObject(module, "win32", temp);

	/* Initialize the event handle used to signal Ctrl-C */
	sigint_event = CreateEvent(NULL, TRUE, FALSE, NULL);
	if (!sigint_event) {
		PyErr_SetFromWindowsErr(0);
		return;
	}
	if (!SetConsoleCtrlHandler(ProcessingCtrlHandler, TRUE)) {
		PyErr_SetFromWindowsErr(0);
		return;
	}
#endif

	/* Add configuration macros */
	temp = PyDict_New();
	if (!temp)
		return;
#define ADD_FLAG(name)						  \
	value = Py_BuildValue("i", name);			  \
	if (value == NULL) { Py_DECREF(temp); return; }		  \
	if (PyDict_SetItemString(temp, #name, value) < 0) {	  \
		Py_DECREF(temp); Py_DECREF(value); return; }	  \
	Py_DECREF(value)
	
#if defined(HAVE_SEM_OPEN) && !defined(HAVE_BROKEN_POSIX_SEMAPHORES)
	ADD_FLAG(HAVE_SEM_OPEN);
#endif
#ifdef HAVE_SEM_TIMEDWAIT
	ADD_FLAG(HAVE_SEM_TIMEDWAIT);
#endif
#ifdef HAVE_FD_TRANSFER
	ADD_FLAG(HAVE_FD_TRANSFER);
#endif
#ifdef HAVE_BROKEN_SEM_GETVALUE
	ADD_FLAG(HAVE_BROKEN_SEM_GETVALUE);
#endif
#ifdef HAVE_BROKEN_SEM_UNLINK
	ADD_FLAG(HAVE_BROKEN_SEM_UNLINK);
#endif
	if (PyModule_AddObject(module, "flags", temp) < 0)
		return;
}