cpython/Modules/fcntlmodule.c

/* fcntl module */

#include "Python.h"

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#ifdef HAVE_SYS_FILE_H
#include <sys/file.h>
#endif

#include <sys/ioctl.h>
#include <fcntl.h>


/* fcntl(fd, opt, [arg]) */

static PyObject *
fcntl_fcntl(PyObject *self, PyObject *args)
{
	int fd;
	int code;
	int arg;
	int ret;
	char *str;
	int len;
	char buf[1024];

	if (PyArg_ParseTuple(args, "iis#:fcntl", &fd, &code, &str, &len)) {
		if (len > sizeof buf) {
			PyErr_SetString(PyExc_ValueError,
					"fcntl string arg too long");
			return NULL;
		}
		memcpy(buf, str, len);
		Py_BEGIN_ALLOW_THREADS
		ret = fcntl(fd, code, buf);
		Py_END_ALLOW_THREADS
		if (ret < 0) {
			PyErr_SetFromErrno(PyExc_IOError);
			return NULL;
		}
		return PyString_FromStringAndSize(buf, len);
	}

	PyErr_Clear();
	arg = 0;
	if (!PyArg_ParseTuple(args, "ii|i;fcntl requires 2 integers and optionally a third integer or a string", 
			      &fd, &code, &arg)) {
	  return NULL;
	}
	Py_BEGIN_ALLOW_THREADS
	ret = fcntl(fd, code, arg);
	Py_END_ALLOW_THREADS
	if (ret < 0) {
		PyErr_SetFromErrno(PyExc_IOError);
		return NULL;
	}
	return PyInt_FromLong((long)ret);
}

static char fcntl_doc [] =

"fcntl(fd, opt, [arg])\n\
\n\
Perform the requested operation on file descriptor fd.  The operation\n\
is defined by op and is operating system dependent.  Typically these\n\
codes can be retrieved from the library module FCNTL.  The argument arg\n\
is optional, and defaults to 0; it may be an int or a string. If arg is\n\
given as a string, the return value of fcntl is a string of that length,\n\
containing the resulting value put in the arg buffer by the operating system.\n\
The length of the arg string is not allowed to exceed 1024 bytes. If the arg\n\
given is an integer or if none is specified, the result value is an integer\n\
corresponding to the return value of the fcntl call in the C code.";


/* ioctl(fd, opt, [arg]) */

static PyObject *
fcntl_ioctl(PyObject *self, PyObject *args)
{
	int fd;
	int code;
	int arg;
	int ret;
	char *str;
	int len;
	char buf[1024];

	if (PyArg_ParseTuple(args, "iis#:ioctl", &fd, &code, &str, &len)) {
		if (len > sizeof buf) {
			PyErr_SetString(PyExc_ValueError,
					"ioctl string arg too long");
			return NULL;
		}
		memcpy(buf, str, len);
		Py_BEGIN_ALLOW_THREADS
		ret = ioctl(fd, code, buf);
		Py_END_ALLOW_THREADS
		if (ret < 0) {
			PyErr_SetFromErrno(PyExc_IOError);
			return NULL;
		}
		return PyString_FromStringAndSize(buf, len);
	}

	PyErr_Clear();
	arg = 0;
	if (!PyArg_ParseTuple(args, "ii|i;ioctl requires 2 integers and optionally a third integer or a string", 
			      &fd, &code, &arg)) {
	  return NULL;
	}
	Py_BEGIN_ALLOW_THREADS
	ret = ioctl(fd, code, arg);
	Py_END_ALLOW_THREADS
	if (ret < 0) {
		PyErr_SetFromErrno(PyExc_IOError);
		return NULL;
	}
	return PyInt_FromLong((long)ret);
}

static char ioctl_doc [] =
"ioctl(fd, opt, [arg])\n\
\n\
Perform the requested operation on file descriptor fd.  The operation\n\
is defined by op and is operating system dependent.  Typically these\n\
codes can be retrieved from the library module IOCTL.  The argument arg\n\
is optional, and defaults to 0; it may be an int or a string. If arg is\n\
given as a string, the return value of ioctl is a string of that length,\n\
containing the resulting value put in the arg buffer by the operating system.\n\
The length of the arg string is not allowed to exceed 1024 bytes. If the arg\n\
given is an integer or if none is specified, the result value is an integer\n\
corresponding to the return value of the ioctl call in the C code.";


/* flock(fd, operation) */

static PyObject *
fcntl_flock(PyObject *self, PyObject *args)
{
	int fd;
	int code;
	int ret;

	if (!PyArg_ParseTuple(args, "ii:flock", &fd, &code))
		return NULL;

#ifdef HAVE_FLOCK
	Py_BEGIN_ALLOW_THREADS
	ret = flock(fd, code);
	Py_END_ALLOW_THREADS
#else

#ifndef LOCK_SH
#define LOCK_SH		1	/* shared lock */
#define LOCK_EX		2	/* exclusive lock */
#define LOCK_NB		4	/* don't block when locking */
#define LOCK_UN		8	/* unlock */
#endif
	{
		struct flock l;
		if (code == LOCK_UN)
			l.l_type = F_UNLCK;
		else if (code & LOCK_SH)
			l.l_type = F_RDLCK;
		else if (code & LOCK_EX)
			l.l_type = F_WRLCK;
		else {
			PyErr_SetString(PyExc_ValueError,
					"unrecognized flock argument");
			return NULL;
		}
		l.l_whence = l.l_start = l.l_len = 0;
		Py_BEGIN_ALLOW_THREADS
		ret = fcntl(fd, (code & LOCK_NB) ? F_SETLK : F_SETLKW, &l);
		Py_END_ALLOW_THREADS
	}
#endif /* HAVE_FLOCK */
	if (ret < 0) {
		PyErr_SetFromErrno(PyExc_IOError);
		return NULL;
	}
	Py_INCREF(Py_None);
	return Py_None;
}

static char flock_doc [] =
"flock(fd, operation)\n\
\n\
Perform the lock operation op on file descriptor fd.  See the Unix \n\
manual flock(3) for details.  (On some systems, this function is\n\
emulated using fcntl().)";


/* lockf(fd, operation) */
static PyObject *
fcntl_lockf(PyObject *self, PyObject *args)
{
	int fd, code, ret, whence = 0;
	PyObject *lenobj = NULL, *startobj = NULL;

	if (!PyArg_ParseTuple(args, "ii|OOi:lockf", &fd, &code,
			      &lenobj, &startobj, &whence))
	    return NULL;

#ifndef LOCK_SH
#define LOCK_SH		1	/* shared lock */
#define LOCK_EX		2	/* exclusive lock */
#define LOCK_NB		4	/* don't block when locking */
#define LOCK_UN		8	/* unlock */
#endif
	{
		struct flock l;
		if (code == LOCK_UN)
			l.l_type = F_UNLCK;
		else if (code & LOCK_SH)
			l.l_type = F_RDLCK;
		else if (code & LOCK_EX)
			l.l_type = F_WRLCK;
		else {
			PyErr_SetString(PyExc_ValueError,
					"unrecognized flock argument");
			return NULL;
		}
		l.l_start = l.l_len = 0;
		if (startobj != NULL) {
#if !defined(HAVE_LARGEFILE_SUPPORT)
			l.l_start = PyInt_AsLong(startobj);
#else
			l.l_start = PyLong_Check(startobj) ?
					PyLong_AsLongLong(startobj) :
					PyInt_AsLong(startobj);
#endif
			if (PyErr_Occurred())
				return NULL;
		}
		if (lenobj != NULL) {
#if !defined(HAVE_LARGEFILE_SUPPORT)
			l.l_len = PyInt_AsLong(lenobj);
#else
			l.l_len = PyLong_Check(lenobj) ?
					PyLong_AsLongLong(lenobj) :
					PyInt_AsLong(lenobj);
#endif
			if (PyErr_Occurred())
				return NULL;
		}
		l.l_whence = whence;
		Py_BEGIN_ALLOW_THREADS
		ret = fcntl(fd, (code & LOCK_NB) ? F_SETLK : F_SETLKW, &l);
		Py_END_ALLOW_THREADS
	}
	if (ret < 0) {
		PyErr_SetFromErrno(PyExc_IOError);
		return NULL;
	}
	Py_INCREF(Py_None);
	return Py_None;
}

static char lockf_doc [] =
"lockf (fd, operation, length=0, start=0, whence=0)

This is essentially a wrapper around the fcntl() locking calls.  fd is the
file descriptor of the file to lock or unlock, and operation is one of the
following values:

    LOCK_UN - unlock
    LOCK_SH - acquire a shared lock
    LOCK_EX - acquire an exclusive lock

When operation is LOCK_SH or LOCK_EX, it can also be bit-wise OR'd with
LOCK_NB to avoid blocking on lock acquisition.  If LOCK_NB is used and the
lock cannot be acquired, an IOError will be raised and the exception will
have an errno attribute set to EACCES or EAGAIN (depending on the operating
system -- for portability, check for either value).

length is the number of bytes to lock, with the default meaning to lock to
EOF.  start is the byte offset, relative to whence, to that the lock
starts.  whence is as with fileobj.seek(), specifically:

    0 - relative to the start of the file (SEEK_SET)
    1 - relative to the current buffer position (SEEK_CUR)
    2 - relative to the end of the file (SEEK_END)";

/* List of functions */

static PyMethodDef fcntl_methods[] = {
	{"fcntl",	fcntl_fcntl, METH_VARARGS, fcntl_doc},
	{"ioctl",	fcntl_ioctl, METH_VARARGS, ioctl_doc},
	{"flock",	fcntl_flock, METH_VARARGS, flock_doc},
	{"lockf",       fcntl_lockf, METH_VARARGS, lockf_doc},
	{NULL,		NULL}		/* sentinel */
};


static char module_doc [] =

"This module performs file control and I/O control on file \n\
descriptors.  It is an interface to the fcntl() and ioctl() Unix\n\
routines.  File descriptors can be obtained with the fileno() method of\n\
a file or socket object.";

/* Module initialisation */

static int
ins(PyObject* d, char* symbol, long value)
{
        PyObject* v = PyInt_FromLong(value);
        if (!v || PyDict_SetItemString(d, symbol, v) < 0)
                return -1;

        Py_DECREF(v);
        return 0;
}

static int
all_ins(PyObject* d)
{
        if (ins(d, "LOCK_SH", (long)LOCK_SH)) return -1;
        if (ins(d, "LOCK_EX", (long)LOCK_EX)) return -1;
        if (ins(d, "LOCK_NB", (long)LOCK_NB)) return -1;
        if (ins(d, "LOCK_UN", (long)LOCK_UN)) return -1;
	return 0;
}

DL_EXPORT(void)
initfcntl(void)
{
	PyObject *m, *d;

	/* Create the module and add the functions and documentation */
	m = Py_InitModule3("fcntl", fcntl_methods, module_doc);

	/* Add some symbolic constants to the module */
	d = PyModule_GetDict(m);
	all_ins(d);
}