Objects/abstract.c

/* Abstract Object Interface (many thanks to Jim Fulton) */

#include "Python.h"
#include <ctype.h>

/* Shorthands to return certain errors */

static PyObject *
type_error(const char *msg)
{
	PyErr_SetString(PyExc_TypeError, msg);
	return NULL;
}

static PyObject *
null_error(void)
{
	if (!PyErr_Occurred())
		PyErr_SetString(PyExc_SystemError,
				"null argument to internal routine");
	return NULL;
}

/* Operations on any object */

int
PyObject_Cmp(PyObject *o1, PyObject *o2, int *result)
{
	int r;

	if (o1 == NULL || o2 == NULL) {
		null_error();
		return -1;
	}
	r = PyObject_Compare(o1, o2);
	if (PyErr_Occurred())
		return -1;
	*result = r;
	return 0;
}

PyObject *
PyObject_Type(PyObject *o)
{
	PyObject *v;

	if (o == NULL)
		return null_error();
	v = (PyObject *)o->ob_type;
	Py_INCREF(v);
	return v;
}

int
PyObject_Size(PyObject *o)
{
	PySequenceMethods *m;

	if (o == NULL) {
		null_error();
		return -1;
	}

	m = o->ob_type->tp_as_sequence;
	if (m && m->sq_length)
		return m->sq_length(o);

	return PyMapping_Size(o);
}

#undef PyObject_Length
int
PyObject_Length(PyObject *o)
{
	return PyObject_Size(o);
}
#define PyObject_Length PyObject_Size

PyObject *
PyObject_GetItem(PyObject *o, PyObject *key)
{
	PyMappingMethods *m;

	if (o == NULL || key == NULL)
		return null_error();

	m = o->ob_type->tp_as_mapping;
	if (m && m->mp_subscript)
		return m->mp_subscript(o, key);

	if (o->ob_type->tp_as_sequence) {
		if (PyInt_Check(key))
			return PySequence_GetItem(o, PyInt_AsLong(key));
		else if (PyLong_Check(key)) {
			long key_value = PyLong_AsLong(key);
			if (key_value == -1 && PyErr_Occurred())
				return NULL;
			return PySequence_GetItem(o, key_value);
		}
		return type_error("sequence index must be integer");
	}

	return type_error("unsubscriptable object");
}

int
PyObject_SetItem(PyObject *o, PyObject *key, PyObject *value)
{
	PyMappingMethods *m;

	if (o == NULL || key == NULL || value == NULL) {
		null_error();
		return -1;
	}
	m = o->ob_type->tp_as_mapping;
	if (m && m->mp_ass_subscript)
		return m->mp_ass_subscript(o, key, value);

	if (o->ob_type->tp_as_sequence) {
		if (PyInt_Check(key))
			return PySequence_SetItem(o, PyInt_AsLong(key), value);
		else if (PyLong_Check(key)) {
			long key_value = PyLong_AsLong(key);
			if (key_value == -1 && PyErr_Occurred())
				return -1;
			return PySequence_SetItem(o, key_value, value);
		}
		type_error("sequence index must be integer");
		return -1;
	}

	type_error("object does not support item assignment");
	return -1;
}

int
PyObject_DelItem(PyObject *o, PyObject *key)
{
	PyMappingMethods *m;

	if (o == NULL || key == NULL) {
		null_error();
		return -1;
	}
	m = o->ob_type->tp_as_mapping;
	if (m && m->mp_ass_subscript)
		return m->mp_ass_subscript(o, key, (PyObject*)NULL);

	if (o->ob_type->tp_as_sequence) {
		if (PyInt_Check(key))
			return PySequence_DelItem(o, PyInt_AsLong(key));
		else if (PyLong_Check(key)) {
			long key_value = PyLong_AsLong(key);
			if (key_value == -1 && PyErr_Occurred())
				return -1;
			return PySequence_DelItem(o, key_value);
		}
		type_error("sequence index must be integer");
		return -1;
	}

	type_error("object does not support item deletion");
	return -1;
}

int PyObject_AsCharBuffer(PyObject *obj,
			  const char **buffer,
			  int *buffer_len)
{
	PyBufferProcs *pb;
	const char *pp;
	int len;

	if (obj == NULL || buffer == NULL || buffer_len == NULL) {
		null_error();
		return -1;
	}
	pb = obj->ob_type->tp_as_buffer;
	if ( pb == NULL ||
	     pb->bf_getcharbuffer == NULL ||
	     pb->bf_getsegcount == NULL ) {
		PyErr_SetString(PyExc_TypeError,
				"expected a character buffer object");
		goto onError;
	}
	if ( (*pb->bf_getsegcount)(obj,NULL) != 1 ) {
		PyErr_SetString(PyExc_TypeError,
				"expected a single-segment buffer object");
		goto onError;
	}
	len = (*pb->bf_getcharbuffer)(obj,0,&pp);
	if (len < 0)
		goto onError;
	*buffer = pp;
	*buffer_len = len;
	return 0;

 onError:
	return -1;
}

int PyObject_AsReadBuffer(PyObject *obj,
			  const void **buffer,
			  int *buffer_len)
{
	PyBufferProcs *pb;
	void *pp;
	int len;

	if (obj == NULL || buffer == NULL || buffer_len == NULL) {
		null_error();
		return -1;
	}
	pb = obj->ob_type->tp_as_buffer;
	if ( pb == NULL ||
	     pb->bf_getreadbuffer == NULL ||
	     pb->bf_getsegcount == NULL ) {
		PyErr_SetString(PyExc_TypeError,
				"expected a readable buffer object");
		goto onError;
	}
	if ( (*pb->bf_getsegcount)(obj,NULL) != 1 ) {
		PyErr_SetString(PyExc_TypeError,
				"expected a single-segment buffer object");
		goto onError;
	}
	len = (*pb->bf_getreadbuffer)(obj,0,&pp);
	if (len < 0)
		goto onError;
	*buffer = pp;
	*buffer_len = len;
	return 0;

 onError:
	return -1;
}

int PyObject_AsWriteBuffer(PyObject *obj,
			   void **buffer,
			   int *buffer_len)
{
	PyBufferProcs *pb;
	void*pp;
	int len;

	if (obj == NULL || buffer == NULL || buffer_len == NULL) {
		null_error();
		return -1;
	}
	pb = obj->ob_type->tp_as_buffer;
	if ( pb == NULL ||
	     pb->bf_getwritebuffer == NULL ||
	     pb->bf_getsegcount == NULL ) {
		PyErr_SetString(PyExc_TypeError,
				"expected a writeable buffer object");
		goto onError;
	}
	if ( (*pb->bf_getsegcount)(obj,NULL) != 1 ) {
		PyErr_SetString(PyExc_TypeError,
				"expected a single-segment buffer object");
		goto onError;
	}
	len = (*pb->bf_getwritebuffer)(obj,0,&pp);
	if (len < 0)
		goto onError;
	*buffer = pp;
	*buffer_len = len;
	return 0;

 onError:
	return -1;
}

/* Operations on numbers */

int
PyNumber_Check(PyObject *o)
{
	return o && o->ob_type->tp_as_number;
}

/* Binary operators */

#define BINOP(v, w, opname, ropname, thisfunc) \
	if (PyInstance_Check(v) || PyInstance_Check(w)) \
		return PyInstance_DoBinOp(v, w, opname, ropname, thisfunc)

PyObject *
PyNumber_Or(PyObject *v, PyObject *w)
{
	BINOP(v, w, "__or__", "__ror__", PyNumber_Or);
	if (v->ob_type->tp_as_number != NULL) {
		PyObject *x = NULL;
		PyObject * (*f)(PyObject *, PyObject *);
		if (PyNumber_Coerce(&v, &w) != 0)
			return NULL;
		if ((f = v->ob_type->tp_as_number->nb_or) != NULL)
			x = (*f)(v, w);
		Py_DECREF(v);
		Py_DECREF(w);
		if (f != NULL)
			return x;
	}
	return type_error("bad operand type(s) for |");
}

PyObject *
PyNumber_Xor(PyObject *v, PyObject *w)
{
	BINOP(v, w, "__xor__", "__rxor__", PyNumber_Xor);
	if (v->ob_type->tp_as_number != NULL) {
		PyObject *x = NULL;
		PyObject * (*f)(PyObject *, PyObject *);
		if (PyNumber_Coerce(&v, &w) != 0)
			return NULL;
		if ((f = v->ob_type->tp_as_number->nb_xor) != NULL)
			x = (*f)(v, w);
		Py_DECREF(v);
		Py_DECREF(w);
		if (f != NULL)
			return x;
	}
	return type_error("bad operand type(s) for ^");
}

PyObject *
PyNumber_And(PyObject *v, PyObject *w)
{
	BINOP(v, w, "__and__", "__rand__", PyNumber_And);
	if (v->ob_type->tp_as_number != NULL) {
		PyObject *x = NULL;
		PyObject * (*f)(PyObject *, PyObject *);
		if (PyNumber_Coerce(&v, &w) != 0)
			return NULL;
		if ((f = v->ob_type->tp_as_number->nb_and) != NULL)
			x = (*f)(v, w);
		Py_DECREF(v);
		Py_DECREF(w);
		if (f != NULL)
			return x;
	}
	return type_error("bad operand type(s) for &");
}

PyObject *
PyNumber_Lshift(PyObject *v, PyObject *w)
{
	BINOP(v, w, "__lshift__", "__rlshift__", PyNumber_Lshift);
	if (v->ob_type->tp_as_number != NULL) {
		PyObject *x = NULL;
		PyObject * (*f)(PyObject *, PyObject *);
		if (PyNumber_Coerce(&v, &w) != 0)
			return NULL;
		if ((f = v->ob_type->tp_as_number->nb_lshift) != NULL)
			x = (*f)(v, w);
		Py_DECREF(v);
		Py_DECREF(w);
		if (f != NULL)
			return x;
	}
	return type_error("bad operand type(s) for <<");
}

PyObject *
PyNumber_Rshift(PyObject *v, PyObject *w)
{
	BINOP(v, w, "__rshift__", "__rrshift__", PyNumber_Rshift);
	if (v->ob_type->tp_as_number != NULL) {
		PyObject *x = NULL;
		PyObject * (*f)(PyObject *, PyObject *);
		if (PyNumber_Coerce(&v, &w) != 0)
			return NULL;
		if ((f = v->ob_type->tp_as_number->nb_rshift) != NULL)
			x = (*f)(v, w);
		Py_DECREF(v);
		Py_DECREF(w);
		if (f != NULL)
			return x;
	}
	return type_error("bad operand type(s) for >>");
}

PyObject *
PyNumber_Add(PyObject *v, PyObject *w)
{
	PySequenceMethods *m;

	BINOP(v, w, "__add__", "__radd__", PyNumber_Add);
	m = v->ob_type->tp_as_sequence;
	if (m && m->sq_concat)
		return (*m->sq_concat)(v, w);
	else if (v->ob_type->tp_as_number != NULL) {
		PyObject *x = NULL;
		PyObject * (*f)(PyObject *, PyObject *);
		if (PyNumber_Coerce(&v, &w) != 0)
			return NULL;
		if ((f = v->ob_type->tp_as_number->nb_add) != NULL)
			x = (*f)(v, w);
		Py_DECREF(v);
		Py_DECREF(w);
		if (f != NULL)
			return x;
	}
	return type_error("bad operand type(s) for +");
}

PyObject *
PyNumber_Subtract(PyObject *v, PyObject *w)
{
	BINOP(v, w, "__sub__", "__rsub__", PyNumber_Subtract);
	if (v->ob_type->tp_as_number != NULL) {
		PyObject *x = NULL;
		PyObject * (*f)(PyObject *, PyObject *);
		if (PyNumber_Coerce(&v, &w) != 0)
			return NULL;
		if ((f = v->ob_type->tp_as_number->nb_subtract) != NULL)
			x = (*f)(v, w);
		Py_DECREF(v);
		Py_DECREF(w);
		if (f != NULL)
			return x;
	}
	return type_error("bad operand type(s) for -");
}

PyObject *
PyNumber_Multiply(PyObject *v, PyObject *w)
{
	PyTypeObject *tp = v->ob_type;
	PySequenceMethods *m;

	BINOP(v, w, "__mul__", "__rmul__", PyNumber_Multiply);
	if (tp->tp_as_number != NULL &&
	    w->ob_type->tp_as_sequence != NULL &&
	    !PyInstance_Check(v)) {
		/* number*sequence -- swap v and w */
		PyObject *tmp = v;
		v = w;
		w = tmp;
		tp = v->ob_type;
	}
	if (tp->tp_as_number != NULL) {
		PyObject *x = NULL;
		PyObject * (*f)(PyObject *, PyObject *);
		if (PyInstance_Check(v)) {
			/* Instances of user-defined classes get their
			   other argument uncoerced, so they may
			   implement sequence*number as well as
			   number*number. */
			Py_INCREF(v);
			Py_INCREF(w);
		}
		else if (PyNumber_Coerce(&v, &w) != 0)
			return NULL;
		if ((f = v->ob_type->tp_as_number->nb_multiply) != NULL)
			x = (*f)(v, w);
		Py_DECREF(v);
		Py_DECREF(w);
		if (f != NULL)
			return x;
	}
	m = tp->tp_as_sequence;
	if (m && m->sq_repeat) {
		long mul_value;

		if (PyInt_Check(w)) {
			mul_value = PyInt_AsLong(w);
		}
		else if (PyLong_Check(w)) {
			mul_value = PyLong_AsLong(w);
			if (mul_value == -1 && PyErr_Occurred())
                                return NULL; 
		}
		else {
			return type_error(
				"can't multiply sequence with non-int");
		}
		return (*m->sq_repeat)(v, (int)mul_value);
	}
	return type_error("bad operand type(s) for *");
}

PyObject *
PyNumber_Divide(PyObject *v, PyObject *w)
{
	BINOP(v, w, "__div__", "__rdiv__", PyNumber_Divide);
	if (v->ob_type->tp_as_number != NULL) {
		PyObject *x = NULL;
		PyObject * (*f)(PyObject *, PyObject *);
		if (PyNumber_Coerce(&v, &w) != 0)
			return NULL;
		if ((f = v->ob_type->tp_as_number->nb_divide) != NULL)
			x = (*f)(v, w);
		Py_DECREF(v);
		Py_DECREF(w);
		if (f != NULL)
			return x;
	}
	return type_error("bad operand type(s) for /");
}

PyObject *
PyNumber_Remainder(PyObject *v, PyObject *w)
{
	if (PyString_Check(v))
		return PyString_Format(v, w);
	else if (PyUnicode_Check(v))
		return PyUnicode_Format(v, w);
	BINOP(v, w, "__mod__", "__rmod__", PyNumber_Remainder);
	if (v->ob_type->tp_as_number != NULL) {
		PyObject *x = NULL;
		PyObject * (*f)(PyObject *, PyObject *);
		if (PyNumber_Coerce(&v, &w) != 0)
			return NULL;
		if ((f = v->ob_type->tp_as_number->nb_remainder) != NULL)
			x = (*f)(v, w);
		Py_DECREF(v);
		Py_DECREF(w);
		if (f != NULL)
			return x;
	}
	return type_error("bad operand type(s) for %");
}

PyObject *
PyNumber_Divmod(PyObject *v, PyObject *w)
{
	BINOP(v, w, "__divmod__", "__rdivmod__", PyNumber_Divmod);
	if (v->ob_type->tp_as_number != NULL) {
		PyObject *x = NULL;
		PyObject * (*f)(PyObject *, PyObject *);
		if (PyNumber_Coerce(&v, &w) != 0)
			return NULL;
		if ((f = v->ob_type->tp_as_number->nb_divmod) != NULL)
			x = (*f)(v, w);
		Py_DECREF(v);
		Py_DECREF(w);
		if (f != NULL)
			return x;
	}
	return type_error("bad operand type(s) for divmod()");
}

/* Power (binary or ternary) */

static PyObject *
do_pow(PyObject *v, PyObject *w)
{
	PyObject *res;
	PyObject * (*f)(PyObject *, PyObject *, PyObject *);
	BINOP(v, w, "__pow__", "__rpow__", do_pow);
	if (v->ob_type->tp_as_number == NULL ||
	    w->ob_type->tp_as_number == NULL) {
		PyErr_SetString(PyExc_TypeError,
				"pow(x, y) requires numeric arguments");
		return NULL;
	}
	if (PyNumber_Coerce(&v, &w) != 0)
		return NULL;
	if ((f = v->ob_type->tp_as_number->nb_power) != NULL)
		res = (*f)(v, w, Py_None);
	else
		res = type_error("pow(x, y) not defined for these operands");
	Py_DECREF(v);
	Py_DECREF(w);
	return res;
}

PyObject *
PyNumber_Power(PyObject *v, PyObject *w, PyObject *z)
{
	PyObject *res;
	PyObject *v1, *z1, *w2, *z2;
	PyObject * (*f)(PyObject *, PyObject *, PyObject *);

	if (z == Py_None)
		return do_pow(v, w);
	/* XXX The ternary version doesn't do class instance coercions */
	if (PyInstance_Check(v))
		return v->ob_type->tp_as_number->nb_power(v, w, z);
	if (v->ob_type->tp_as_number == NULL ||
	    z->ob_type->tp_as_number == NULL ||
	    w->ob_type->tp_as_number == NULL) {
		return type_error("pow(x, y, z) requires numeric arguments");
	}
	if (PyNumber_Coerce(&v, &w) != 0)
		return NULL;
	res = NULL;
	v1 = v;
	z1 = z;
	if (PyNumber_Coerce(&v1, &z1) != 0)
		goto error2;
	w2 = w;
	z2 = z1;
 	if (PyNumber_Coerce(&w2, &z2) != 0)
		goto error1;
	if ((f = v1->ob_type->tp_as_number->nb_power) != NULL)
		res = (*f)(v1, w2, z2);
	else
		res = type_error(
			"pow(x, y, z) not defined for these operands");
	Py_DECREF(w2);
	Py_DECREF(z2);
  error1:
	Py_DECREF(v1);
	Py_DECREF(z1);
  error2:
	Py_DECREF(v);
	Py_DECREF(w);
	return res;
}

/* Unary operators and functions */

PyObject *
PyNumber_Negative(PyObject *o)
{
	PyNumberMethods *m;

	if (o == NULL)
		return null_error();
	m = o->ob_type->tp_as_number;
	if (m && m->nb_negative)
		return (*m->nb_negative)(o);

	return type_error("bad operand type for unary -");
}

PyObject *
PyNumber_Positive(PyObject *o)
{
	PyNumberMethods *m;

	if (o == NULL)
		return null_error();
	m = o->ob_type->tp_as_number;
	if (m && m->nb_positive)
		return (*m->nb_positive)(o);

	return type_error("bad operand type for unary +");
}

PyObject *
PyNumber_Invert(PyObject *o)
{
	PyNumberMethods *m;

	if (o == NULL)
		return null_error();
	m = o->ob_type->tp_as_number;
	if (m && m->nb_invert)
		return (*m->nb_invert)(o);

	return type_error("bad operand type for unary ~");
}

PyObject *
PyNumber_Absolute(PyObject *o)
{
	PyNumberMethods *m;

	if (o == NULL)
		return null_error();
	m = o->ob_type->tp_as_number;
	if (m && m->nb_absolute)
		return m->nb_absolute(o);

	return type_error("bad operand type for abs()");
}

/* Add a check for embedded NULL-bytes in the argument. */
static PyObject *
int_from_string(const char *s, int len)
{
	char *end;
	PyObject *x;

	x = PyInt_FromString((char*)s, &end, 10);
	if (x == NULL)
		return NULL;
	if (end != s + len) {
		PyErr_SetString(PyExc_ValueError,
				"null byte in argument for int()");
		Py_DECREF(x);
		return NULL;
	}
	return x;
}

PyObject *
PyNumber_Int(PyObject *o)
{
	PyNumberMethods *m;
	const char *buffer;
	int buffer_len;

	if (o == NULL)
		return null_error();
	if (PyInt_Check(o)) {
		Py_INCREF(o);
		return o;
	}
	if (PyString_Check(o))
		return int_from_string(PyString_AS_STRING(o), 
				       PyString_GET_SIZE(o));
	if (PyUnicode_Check(o))
		return PyInt_FromUnicode(PyUnicode_AS_UNICODE(o),
					 PyUnicode_GET_SIZE(o),
					 10);
	m = o->ob_type->tp_as_number;
	if (m && m->nb_int)
		return m->nb_int(o);
	if (!PyObject_AsCharBuffer(o, &buffer, &buffer_len))
		return int_from_string((char*)buffer, buffer_len);

	return type_error("object can't be converted to int");
}

/* Add a check for embedded NULL-bytes in the argument. */
static PyObject *
long_from_string(const char *s, int len)
{
	char *end;
	PyObject *x;

	x = PyLong_FromString((char*)s, &end, 10);
	if (x == NULL)
		return NULL;
	if (end != s + len) {
		PyErr_SetString(PyExc_ValueError,
				"null byte in argument for long()");
		Py_DECREF(x);
		return NULL;
	}
	return x;
}

PyObject *
PyNumber_Long(PyObject *o)
{
	PyNumberMethods *m;
	const char *buffer;
	int buffer_len;

	if (o == NULL)
		return null_error();
	if (PyLong_Check(o)) {
		Py_INCREF(o);
		return o;
	}
	if (PyString_Check(o))
		/* need to do extra error checking that PyLong_FromString() 
		 * doesn't do.  In particular long('9.5') must raise an
		 * exception, not truncate the float.
		 */
		return long_from_string(PyString_AS_STRING(o),
					PyString_GET_SIZE(o));
	if (PyUnicode_Check(o))
		/* The above check is done in PyLong_FromUnicode(). */
		return PyLong_FromUnicode(PyUnicode_AS_UNICODE(o),
					  PyUnicode_GET_SIZE(o),
					  10);
	m = o->ob_type->tp_as_number;
	if (m && m->nb_long)
		return m->nb_long(o);
	if (!PyObject_AsCharBuffer(o, &buffer, &buffer_len))
		return long_from_string(buffer, buffer_len);

	return type_error("object can't be converted to long");
}

PyObject *
PyNumber_Float(PyObject *o)
{
	PyNumberMethods *m;

	if (o == NULL)
		return null_error();
	if (PyFloat_Check(o)) {
		Py_INCREF(o);
		return o;
	}
	if (!PyString_Check(o)) {
		m = o->ob_type->tp_as_number;
		if (m && m->nb_float)
			return m->nb_float(o);
	}
	return PyFloat_FromString(o, NULL);
}

/* Operations on sequences */

int
PySequence_Check(PyObject *s)
{
	return s != NULL && s->ob_type->tp_as_sequence;
}

int
PySequence_Size(PyObject *s)
{
	PySequenceMethods *m;

	if (s == NULL) {
		null_error();
		return -1;
	}

	m = s->ob_type->tp_as_sequence;
	if (m && m->sq_length)
		return m->sq_length(s);

	type_error("len() of unsized object");
	return -1;
}

#undef PySequence_Length
int
PySequence_Length(PyObject *s)
{
	return PySequence_Size(s);
}
#define PySequence_Length PySequence_Size

PyObject *
PySequence_Concat(PyObject *s, PyObject *o)
{
	PySequenceMethods *m;

	if (s == NULL || o == NULL)
		return null_error();

	m = s->ob_type->tp_as_sequence;
	if (m && m->sq_concat)
		return m->sq_concat(s, o);

	return type_error("object can't be concatenated");
}

PyObject *
PySequence_Repeat(PyObject *o, int count)
{
	PySequenceMethods *m;

	if (o == NULL)
		return null_error();

	m = o->ob_type->tp_as_sequence;
	if (m && m->sq_repeat)
		return m->sq_repeat(o, count);

	return type_error("object can't be repeated");
}

PyObject *
PySequence_GetItem(PyObject *s, int i)
{
	PySequenceMethods *m;

	if (s == NULL)
		return null_error();

	m = s->ob_type->tp_as_sequence;
	if (m && m->sq_item) {
		if (i < 0) {
			if (m->sq_length) {
				int l = (*m->sq_length)(s);
				if (l < 0)
					return NULL;
				i += l;
			}
		}
		return m->sq_item(s, i);
	}

	return type_error("unindexable object");
}

static PyObject *
sliceobj_from_intint(int i, int j)
{
	PyObject *start, *end, *slice;
	start = PyInt_FromLong((long)i);
	if (!start)
		return NULL;
	end = PyInt_FromLong((long)j);
	if (!end) {
		Py_DECREF(start);
		return NULL;
	}
	slice = PySlice_New(start, end, NULL);
	Py_DECREF(start);
	Py_DECREF(end);
	return slice;
}

PyObject *
PySequence_GetSlice(PyObject *s, int i1, int i2)
{
	PySequenceMethods *m;
	PyMappingMethods *mp;

	if (!s) return null_error();

	m = s->ob_type->tp_as_sequence;
	if (m && m->sq_slice) {
		if (i1 < 0 || i2 < 0) {
			if (m->sq_length) {
				int l = (*m->sq_length)(s);
				if (l < 0)
					return NULL;
				if (i1 < 0)
					i1 += l;
				if (i2 < 0)
					i2 += l;
			}
		}
		return m->sq_slice(s, i1, i2);
	} else if ((mp = s->ob_type->tp_as_mapping) && mp->mp_subscript) {
		PyObject *res;
		PyObject *slice = sliceobj_from_intint(i1, i2);
		if (!slice)
			return NULL;
		res = mp->mp_subscript(s, slice);
		Py_DECREF(slice);
		return res;
	}

	return type_error("unsliceable object");
}

int
PySequence_SetItem(PyObject *s, int i, PyObject *o)
{
	PySequenceMethods *m;

	if (s == NULL) {
		null_error();
		return -1;
	}

	m = s->ob_type->tp_as_sequence;
	if (m && m->sq_ass_item) {
		if (i < 0) {
			if (m->sq_length) {
				int l = (*m->sq_length)(s);
				if (l < 0)
					return -1;
				i += l;
			}
		}
		return m->sq_ass_item(s, i, o);
	}

	type_error("object doesn't support item assignment");
	return -1;
}

int
PySequence_DelItem(PyObject *s, int i)
{
	PySequenceMethods *m;

	if (s == NULL) {
		null_error();
		return -1;
	}

	m = s->ob_type->tp_as_sequence;
	if (m && m->sq_ass_item) {
		if (i < 0) {
			if (m->sq_length) {
				int l = (*m->sq_length)(s);
				if (l < 0)
					return -1;
				i += l;
			}
		}
		return m->sq_ass_item(s, i, (PyObject *)NULL);
	}

	type_error("object doesn't support item deletion");
	return -1;
}

int
PySequence_SetSlice(PyObject *s, int i1, int i2, PyObject *o)
{
	PySequenceMethods *m;
	PyMappingMethods *mp;

	if (s == NULL) {
		null_error();
		return -1;
	}

	m = s->ob_type->tp_as_sequence;
	if (m && m->sq_ass_slice) {
		if (i1 < 0 || i2 < 0) {
			if (m->sq_length) {
				int l = (*m->sq_length)(s);
				if (l < 0)
					return -1;
				if (i1 < 0)
					i1 += l;
				if (i2 < 0)
					i2 += l;
			}
		}
		return m->sq_ass_slice(s, i1, i2, o);
	} else if ((mp = s->ob_type->tp_as_mapping) && mp->mp_ass_subscript) {
		int res;
		PyObject *slice = sliceobj_from_intint(i1, i2);
		if (!slice)
			return -1;
		res = mp->mp_ass_subscript(s, slice, o);
		Py_DECREF(slice);
		return res;
	}

	type_error("object doesn't support slice assignment");
	return -1;
}

int
PySequence_DelSlice(PyObject *s, int i1, int i2)
{
	PySequenceMethods *m;

	if (s == NULL) {
		null_error();
		return -1;
	}

	m = s->ob_type->tp_as_sequence;
	if (m && m->sq_ass_slice) {
		if (i1 < 0 || i2 < 0) {
			if (m->sq_length) {
				int l = (*m->sq_length)(s);
				if (l < 0)
					return -1;
				if (i1 < 0)
					i1 += l;
				if (i2 < 0)
					i2 += l;
			}
		}
		return m->sq_ass_slice(s, i1, i2, (PyObject *)NULL);
	}
	type_error("object doesn't support slice deletion");
	return -1;
}

PyObject *
PySequence_Tuple(PyObject *v)
{
	PySequenceMethods *m;

	if (v == NULL)
		return null_error();

	if (PyTuple_Check(v)) {
		Py_INCREF(v);
		return v;
	}

	if (PyList_Check(v))
		return PyList_AsTuple(v);

	/* There used to be code for strings here, but tuplifying strings is
	   not a common activity, so I nuked it.  Down with code bloat! */

	/* Generic sequence object */
	m = v->ob_type->tp_as_sequence;
	if (m && m->sq_item) {
		int i;
		PyObject *t;
		int n = PySequence_Size(v);
		if (n < 0)
			return NULL;
		t = PyTuple_New(n);
		if (t == NULL)
			return NULL;
		for (i = 0; ; i++) {
			PyObject *item = (*m->sq_item)(v, i);
			if (item == NULL) {
				if (PyErr_ExceptionMatches(PyExc_IndexError))
					PyErr_Clear();
				else {
					Py_DECREF(t);
					t = NULL;
				}
				break;
			}
			if (i >= n) {
				if (n < 500)
					n += 10;
				else
					n += 100;
				if (_PyTuple_Resize(&t, n, 0) != 0)
					break;
			}
			PyTuple_SET_ITEM(t, i, item);
		}
		if (i < n && t != NULL)
			_PyTuple_Resize(&t, i, 0);
		return t;
	}

	/* None of the above */
	return type_error("tuple() argument must be a sequence");
}

PyObject *
PySequence_List(PyObject *v)
{
	PySequenceMethods *m;

	if (v == NULL)
		return null_error();

	if (PyList_Check(v))
		return PyList_GetSlice(v, 0, PyList_GET_SIZE(v));

	m = v->ob_type->tp_as_sequence;
	if (m && m->sq_item) {
		int i;
		PyObject *l;
		int n = PySequence_Size(v);
		if (n < 0)
			return NULL;
		l = PyList_New(n);
		if (l == NULL)
			return NULL;
		for (i = 0; ; i++) {
			PyObject *item = (*m->sq_item)(v, i);
			if (item == NULL) {
				if (PyErr_ExceptionMatches(PyExc_IndexError))
					PyErr_Clear();
				else {
					Py_DECREF(l);
					l = NULL;
				}
				break;
			}
			if (i < n)
				PyList_SET_ITEM(l, i, item);
			else if (PyList_Append(l, item) < 0) {
				Py_DECREF(l);
				l = NULL;
				break;
			}
		}
		if (i < n && l != NULL) {
			if (PyList_SetSlice(l, i, n, (PyObject *)NULL) != 0) {
				Py_DECREF(l);
				l = NULL;
			}
		}
		return l;
	}
	return type_error("list() argument must be a sequence");
}

PyObject *
PySequence_Fast(PyObject *v, const char *m)
{
	if (v == NULL)
		return null_error();

	if (PyList_Check(v) || PyTuple_Check(v)) {
		Py_INCREF(v);
		return v;
	}

	v = PySequence_Tuple(v);
	if (v == NULL && PyErr_ExceptionMatches(PyExc_TypeError))
		return type_error(m);

	return v;
}

int
PySequence_Count(PyObject *s, PyObject *o)
{
	int l, i, n, cmp, err;
	PyObject *item;

	if (s == NULL || o == NULL) {
		null_error();
		return -1;
	}
	
	l = PySequence_Size(s);
	if (l < 0)
		return -1;

	n = 0;
	for (i = 0; i < l; i++) {
		item = PySequence_GetItem(s, i);
		if (item == NULL)
			return -1;
		err = PyObject_Cmp(item, o, &cmp);
		Py_DECREF(item);
		if (err < 0)
			return err;
		if (cmp == 0)
			n++;
	}
	return n;
}

int
PySequence_Contains(PyObject *w, PyObject *v) /* v in w */
{
	int i, cmp;
	PyObject *x;
	PySequenceMethods *sq;

	if(PyType_HasFeature(w->ob_type, Py_TPFLAGS_HAVE_SEQUENCE_IN)) {
		sq = w->ob_type->tp_as_sequence;
	        if(sq != NULL && sq->sq_contains != NULL)
			return (*sq->sq_contains)(w, v);
	}
	
	/* If there is no better way to check whether an item is is contained,
	   do it the hard way */
	sq = w->ob_type->tp_as_sequence;
	if (sq == NULL || sq->sq_item == NULL) {
		PyErr_SetString(PyExc_TypeError,
			"'in' or 'not in' needs sequence right argument");
		return -1;
	}

	for (i = 0; ; i++) {
		x = (*sq->sq_item)(w, i);
		if (x == NULL) {
			if (PyErr_ExceptionMatches(PyExc_IndexError)) {
				PyErr_Clear();
				break;
			}
			return -1;
		}
		cmp = PyObject_Compare(v, x);
		Py_XDECREF(x);
		if (cmp == 0)
			return 1;
		if (PyErr_Occurred())
			return -1;
	}

	return 0;
}

/* Backwards compatibility */
#undef PySequence_In
int
PySequence_In(PyObject *w, PyObject *v)
{
	return PySequence_Contains(w, v);
}

int
PySequence_Index(PyObject *s, PyObject *o)
{
	int l, i, cmp, err;
	PyObject *item;

	if (s == NULL || o == NULL) {
		null_error();
		return -1;
	}
	
	l = PySequence_Size(s);
	if (l < 0)
		return -1;

	for (i = 0; i < l; i++) {
		item = PySequence_GetItem(s, i);
		if (item == NULL)
			return -1;
		err = PyObject_Cmp(item, o, &cmp);
		Py_DECREF(item);
		if (err < 0)
			return err;
		if (cmp == 0)
			return i;
	}

	PyErr_SetString(PyExc_ValueError, "sequence.index(x): x not in list");
	return -1;
}

/* Operations on mappings */

int
PyMapping_Check(PyObject *o)
{
	return o && o->ob_type->tp_as_mapping;
}

int
PyMapping_Size(PyObject *o)
{
	PyMappingMethods *m;

	if (o == NULL) {
		null_error();
		return -1;
	}

	m = o->ob_type->tp_as_mapping;
	if (m && m->mp_length)
		return m->mp_length(o);

	type_error("len() of unsized object");
	return -1;
}

#undef PyMapping_Length
int
PyMapping_Length(PyObject *o)
{
	return PyMapping_Size(o);
}
#define PyMapping_Length PyMapping_Size

PyObject *
PyMapping_GetItemString(PyObject *o, char *key)
{
	PyObject *okey, *r;

	if (key == NULL)
		return null_error();

	okey = PyString_FromString(key);
	if (okey == NULL)
		return NULL;
	r = PyObject_GetItem(o, okey);
	Py_DECREF(okey);
	return r;
}

int
PyMapping_SetItemString(PyObject *o, char *key, PyObject *value)
{
	PyObject *okey;
	int r;

	if (key == NULL) {
		null_error();
		return -1;
	}

	okey = PyString_FromString(key);
	if (okey == NULL)
		return -1;
	r = PyObject_SetItem(o, okey, value);
	Py_DECREF(okey);
	return r;
}

int
PyMapping_HasKeyString(PyObject *o, char *key)
{
	PyObject *v;

	v = PyMapping_GetItemString(o, key);
	if (v) {
		Py_DECREF(v);
		return 1;
	}
	PyErr_Clear();
	return 0;
}

int
PyMapping_HasKey(PyObject *o, PyObject *key)
{
	PyObject *v;

	v = PyObject_GetItem(o, key);
	if (v) {
		Py_DECREF(v);
		return 1;
	}
	PyErr_Clear();
	return 0;
}

/* Operations on callable objects */

/* XXX PyCallable_Check() is in object.c */

PyObject *
PyObject_CallObject(PyObject *o, PyObject *a)
{
	PyObject *r;
	PyObject *args = a;

	if (args == NULL) {
		args = PyTuple_New(0);
		if (args == NULL)
			return NULL;
	}

	r = PyEval_CallObject(o, args);

	if (args != a) {
		Py_DECREF(args);
	}

	return r;
}

PyObject *
PyObject_CallFunction(PyObject *callable, char *format, ...)
{
	va_list va;
	PyObject *args, *retval;
	va_start(va, format);

	if (callable == NULL) {
		va_end(va);
		return null_error();
	}

	if (format)
		args = Py_VaBuildValue(format, va);
	else
		args = PyTuple_New(0);

	va_end(va);
	
	if (args == NULL)
		return NULL;

	if (!PyTuple_Check(args)) {
		PyObject *a;

		a = PyTuple_New(1);
		if (a == NULL)
			return NULL;
		if (PyTuple_SetItem(a, 0, args) < 0)
			return NULL;
		args = a;
	}
	retval = PyObject_CallObject(callable, args);

	Py_DECREF(args);

	return retval;
}

PyObject *
PyObject_CallMethod(PyObject *o, char *name, char *format, ...)
{
	va_list va;
	PyObject *args, *func = 0, *retval;
	va_start(va, format);

	if (o == NULL || name == NULL) {
		va_end(va);
		return null_error();
	}

	func = PyObject_GetAttrString(o, name);
	if (func == NULL) {
		va_end(va);
		PyErr_SetString(PyExc_AttributeError, name);
		return 0;
	}

	if (!PyCallable_Check(func)) {
		va_end(va);
		return type_error("call of non-callable attribute");
	}

	if (format && *format)
		args = Py_VaBuildValue(format, va);
	else
		args = PyTuple_New(0);

	va_end(va);

	if (!args)
		return NULL;

	if (!PyTuple_Check(args)) {
		PyObject *a;

		a = PyTuple_New(1);
		if (a == NULL)
			return NULL;
		if (PyTuple_SetItem(a, 0, args) < 0)
			return NULL;
		args = a;
	}

	retval = PyObject_CallObject(func, args);

	Py_DECREF(args);
	Py_DECREF(func);

	return retval;
}