cpython/Modules/_functoolsmodule.c

#include "Python.h"
#include "structmember.h"

/* _functools module written and maintained 
   by Hye-Shik Chang <perky@FreeBSD.org>
   with adaptations by Raymond Hettinger <python@rcn.com>
   Copyright (c) 2004, 2005, 2006 Python Software Foundation.
   All rights reserved.
*/

/* partial object **********************************************************/

typedef struct {
	PyObject_HEAD
	PyObject *fn;
	PyObject *args;
	PyObject *kw;
	PyObject *dict;
	PyObject *weakreflist; /* List of weak references */
} partialobject;

static PyTypeObject partial_type;

static PyObject *
partial_new(PyTypeObject *type, PyObject *args, PyObject *kw)
{
	PyObject *func;
	partialobject *pto;

	if (PyTuple_GET_SIZE(args) < 1) {
		PyErr_SetString(PyExc_TypeError,
				"type 'partial' takes at least one argument");
		return NULL;
	}

	func = PyTuple_GET_ITEM(args, 0);
	if (!PyCallable_Check(func)) {
		PyErr_SetString(PyExc_TypeError,
				"the first argument must be callable");
		return NULL;
	}

	/* create partialobject structure */
	pto = (partialobject *)type->tp_alloc(type, 0);
	if (pto == NULL)
		return NULL;

	pto->fn = func;
	Py_INCREF(func);
	pto->args = PyTuple_GetSlice(args, 1, PY_SSIZE_T_MAX);
	if (pto->args == NULL) {
		pto->kw = NULL;
		Py_DECREF(pto);
		return NULL;
	}
	if (kw != NULL) {
		pto->kw = PyDict_Copy(kw);
		if (pto->kw == NULL) {
			Py_DECREF(pto);
			return NULL;
		}
	} else {
		pto->kw = Py_None;
		Py_INCREF(Py_None);
	}

	pto->weakreflist = NULL;
	pto->dict = NULL;

	return (PyObject *)pto;
}

static void
partial_dealloc(partialobject *pto)
{
	PyObject_GC_UnTrack(pto);
	if (pto->weakreflist != NULL)
		PyObject_ClearWeakRefs((PyObject *) pto);
	Py_XDECREF(pto->fn);
	Py_XDECREF(pto->args);
	Py_XDECREF(pto->kw);
	Py_XDECREF(pto->dict);
	Py_TYPE(pto)->tp_free(pto);
}

static PyObject *
partial_call(partialobject *pto, PyObject *args, PyObject *kw)
{
	PyObject *ret;
	PyObject *argappl = NULL, *kwappl = NULL;

	assert (PyCallable_Check(pto->fn));
	assert (PyTuple_Check(pto->args));
	assert (pto->kw == Py_None  ||  PyDict_Check(pto->kw));

	if (PyTuple_GET_SIZE(pto->args) == 0) {
		argappl = args;
		Py_INCREF(args);
	} else if (PyTuple_GET_SIZE(args) == 0) {
		argappl = pto->args;
		Py_INCREF(pto->args);
	} else {
		argappl = PySequence_Concat(pto->args, args);
		if (argappl == NULL)
			return NULL;
	}

	if (pto->kw == Py_None) {
		kwappl = kw;
		Py_XINCREF(kw);
	} else {
		kwappl = PyDict_Copy(pto->kw);
		if (kwappl == NULL) {
			Py_DECREF(argappl);
			return NULL;
		}
		if (kw != NULL) {
			if (PyDict_Merge(kwappl, kw, 1) != 0) {
				Py_DECREF(argappl);
				Py_DECREF(kwappl);
				return NULL;
			}
		}
	}

	ret = PyObject_Call(pto->fn, argappl, kwappl);
	Py_DECREF(argappl);
	Py_XDECREF(kwappl);
	return ret;
}

static int
partial_traverse(partialobject *pto, visitproc visit, void *arg)
{
	Py_VISIT(pto->fn);
	Py_VISIT(pto->args);
	Py_VISIT(pto->kw);
	Py_VISIT(pto->dict);
	return 0;
}

PyDoc_STRVAR(partial_doc,
"partial(func, *args, **keywords) - new function with partial application\n\
	of the given arguments and keywords.\n");

#define OFF(x) offsetof(partialobject, x)
static PyMemberDef partial_memberlist[] = {
	{"func",	T_OBJECT,	OFF(fn),	READONLY,
	 "function object to use in future partial calls"},
	{"args",	T_OBJECT,	OFF(args),	READONLY,
	 "tuple of arguments to future partial calls"},
	{"keywords",	T_OBJECT,	OFF(kw),	READONLY,
	 "dictionary of keyword arguments to future partial calls"},
	{NULL}  /* Sentinel */
};

static PyObject *
partial_get_dict(partialobject *pto)
{
	if (pto->dict == NULL) {
		pto->dict = PyDict_New();
		if (pto->dict == NULL)
			return NULL;
	}
	Py_INCREF(pto->dict);
	return pto->dict;
}

static int
partial_set_dict(partialobject *pto, PyObject *value)
{
	PyObject *tmp;

	/* It is illegal to del p.__dict__ */
	if (value == NULL) {
		PyErr_SetString(PyExc_TypeError,
				"a partial object's dictionary may not be deleted");
		return -1;
	}
	/* Can only set __dict__ to a dictionary */
	if (!PyDict_Check(value)) {
		PyErr_SetString(PyExc_TypeError,
				"setting partial object's dictionary to a non-dict");
		return -1;
	}
	tmp = pto->dict;
	Py_INCREF(value);
	pto->dict = value;
	Py_XDECREF(tmp);
	return 0;
}

static PyGetSetDef partial_getsetlist[] = {
	{"__dict__", (getter)partial_get_dict, (setter)partial_set_dict},
	{NULL} /* Sentinel */
};

static PyTypeObject partial_type = {
	PyVarObject_HEAD_INIT(NULL, 0)
	"functools.partial",		/* tp_name */
	sizeof(partialobject),		/* tp_basicsize */
	0,				/* tp_itemsize */
	/* methods */
	(destructor)partial_dealloc,	/* tp_dealloc */
	0,				/* tp_print */
	0,				/* tp_getattr */
	0,				/* tp_setattr */
	0,				/* tp_reserved */
	0,				/* tp_repr */
	0,				/* tp_as_number */
	0,				/* tp_as_sequence */
	0,				/* tp_as_mapping */
	0,				/* tp_hash */
	(ternaryfunc)partial_call,	/* tp_call */
	0,				/* tp_str */
	PyObject_GenericGetAttr,	/* tp_getattro */
	PyObject_GenericSetAttr,	/* tp_setattro */
	0,				/* tp_as_buffer */
	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
		Py_TPFLAGS_BASETYPE,	/* tp_flags */
	partial_doc,			/* tp_doc */
	(traverseproc)partial_traverse,	/* tp_traverse */
	0,				/* tp_clear */
	0,				/* tp_richcompare */
	offsetof(partialobject, weakreflist),	/* tp_weaklistoffset */
	0,				/* tp_iter */
	0,				/* tp_iternext */
	0,				/* tp_methods */
	partial_memberlist,		/* tp_members */
	partial_getsetlist,		/* tp_getset */
	0,				/* tp_base */
	0,				/* tp_dict */
	0,				/* tp_descr_get */
	0,				/* tp_descr_set */
	offsetof(partialobject, dict),	/* tp_dictoffset */
	0,				/* tp_init */
	0,				/* tp_alloc */
	partial_new,			/* tp_new */
	PyObject_GC_Del,		/* tp_free */
};


/* reduce (used to be a builtin) ********************************************/

static PyObject *
functools_reduce(PyObject *self, PyObject *args)
{
	PyObject *seq, *func, *result = NULL, *it;

	if (!PyArg_UnpackTuple(args, "reduce", 2, 3, &func, &seq, &result))
		return NULL;
	if (result != NULL)
		Py_INCREF(result);

	it = PyObject_GetIter(seq);
	if (it == NULL) {
		PyErr_SetString(PyExc_TypeError,
		    "reduce() arg 2 must support iteration");
		Py_XDECREF(result);
		return NULL;
	}

	if ((args = PyTuple_New(2)) == NULL)
		goto Fail;

	for (;;) {
		PyObject *op2;

		if (args->ob_refcnt > 1) {
			Py_DECREF(args);
			if ((args = PyTuple_New(2)) == NULL)
				goto Fail;
		}

		op2 = PyIter_Next(it);
		if (op2 == NULL) {
			if (PyErr_Occurred())
				goto Fail;
 			break;
		}

		if (result == NULL)
			result = op2;
		else {
			PyTuple_SetItem(args, 0, result);
			PyTuple_SetItem(args, 1, op2);
			if ((result = PyEval_CallObject(func, args)) == NULL)
				goto Fail;
		}
	}

	Py_DECREF(args);

	if (result == NULL)
		PyErr_SetString(PyExc_TypeError,
			   "reduce() of empty sequence with no initial value");

	Py_DECREF(it);
	return result;

Fail:
	Py_XDECREF(args);
	Py_XDECREF(result);
	Py_DECREF(it);
	return NULL;
}

PyDoc_STRVAR(functools_reduce_doc,
"reduce(function, sequence[, initial]) -> value\n\
\n\
Apply a function of two arguments cumulatively to the items of a sequence,\n\
from left to right, so as to reduce the sequence to a single value.\n\
For example, reduce(lambda x, y: x+y, [1, 2, 3, 4, 5]) calculates\n\
((((1+2)+3)+4)+5).  If initial is present, it is placed before the items\n\
of the sequence in the calculation, and serves as a default when the\n\
sequence is empty.");

/* module level code ********************************************************/

PyDoc_STRVAR(module_doc,
"Tools that operate on functions.");

static PyMethodDef module_methods[] = {
 	{"reduce",	functools_reduce,     METH_VARARGS, functools_reduce_doc},
 	{NULL,		NULL}		/* sentinel */
};


static struct PyModuleDef _functoolsmodule = {
	PyModuleDef_HEAD_INIT,
	"_functools",
	module_doc,
	-1,
	module_methods,
	NULL,
	NULL,
	NULL,
	NULL
};

PyMODINIT_FUNC
PyInit__functools(void)
{
	int i;
	PyObject *m;
	char *name;
	PyTypeObject *typelist[] = {
		&partial_type,
		NULL
	};

	m = PyModule_Create(&_functoolsmodule);
	if (m == NULL)
		return NULL;

	for (i=0 ; typelist[i] != NULL ; i++) {
		if (PyType_Ready(typelist[i]) < 0) {
			Py_DECREF(m);
			return NULL;
		}
		name = strchr(typelist[i]->tp_name, '.');
		assert (name != NULL);
		Py_INCREF(typelist[i]);
		PyModule_AddObject(m, name+1, (PyObject *)typelist[i]);
	}
	return m;
}