add abstract.c and sliceobject.c from cpython

from_cpython/Objects/abstract.c

+/* Abstract Object Interface (many thanks to Jim Fulton) */
+
+#include "Python.h"
+#include <ctype.h>
+#include "structmember.h" /* we need the offsetof() macro from there */
+#include "longintrepr.h"
+
+#define NEW_STYLE_NUMBER(o) PyType_HasFeature((o)->ob_type, \
+                Py_TPFLAGS_CHECKTYPES)
+
+
+/* Shorthands to return certain errors */
+
+static PyObject *
+type_error(const char *msg, PyObject *obj)
+{
+    PyErr_Format(PyExc_TypeError, msg, obj->ob_type->tp_name);
+    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;
+}
+
+Py_ssize_t
+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
+Py_ssize_t
+PyObject_Length(PyObject *o)
+{
+    return PyObject_Size(o);
+}
+#define PyObject_Length PyObject_Size
+
+
+/* The length hint function returns a non-negative value from o.__len__()
+   or o.__length_hint__().  If those methods aren't found or return a negative
+   value, then the defaultvalue is returned.  If one of the calls fails,
+   this function returns -1.
+*/
+
+Py_ssize_t
+_PyObject_LengthHint(PyObject *o, Py_ssize_t defaultvalue)
+{
+    static PyObject *hintstrobj = NULL;
+    PyObject *ro, *hintmeth;
+    Py_ssize_t rv;
+
+    /* try o.__len__() */
+    rv = PyObject_Size(o);
+    if (rv >= 0)
+        return rv;
+    if (PyErr_Occurred()) {
+        if (!PyErr_ExceptionMatches(PyExc_TypeError) &&
+            !PyErr_ExceptionMatches(PyExc_AttributeError))
+                return -1;
+        PyErr_Clear();
+    }
+
+    if (PyInstance_Check(o))
+        return defaultvalue;
+    /* try o.__length_hint__() */
+    hintmeth = _PyObject_LookupSpecial(o, "__length_hint__", &hintstrobj);
+    if (hintmeth == NULL) {
+        if (PyErr_Occurred())
+            return -1;
+        else
+            return defaultvalue;
+    }
+    ro = PyObject_CallFunctionObjArgs(hintmeth, NULL);
+    Py_DECREF(hintmeth);
+    if (ro == NULL) {
+        if (!PyErr_ExceptionMatches(PyExc_TypeError) &&
+            !PyErr_ExceptionMatches(PyExc_AttributeError))
+            return -1;
+        PyErr_Clear();
+        return defaultvalue;
+    }
+    rv = PyNumber_Check(ro) ? PyInt_AsSsize_t(ro) : defaultvalue;
+    Py_DECREF(ro);
+    return rv;
+}
+
+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 (PyIndex_Check(key)) {
+            Py_ssize_t key_value;
+            key_value = PyNumber_AsSsize_t(key, PyExc_IndexError);
+            if (key_value == -1 && PyErr_Occurred())
+                return NULL;
+            return PySequence_GetItem(o, key_value);
+        }
+        else if (o->ob_type->tp_as_sequence->sq_item)
+            return type_error("sequence index must "
+                              "be integer, not '%.200s'", key);
+    }
+
+    return type_error("'%.200s' object has no attribute '__getitem__'", o);
+}
+
+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 (PyIndex_Check(key)) {
+            Py_ssize_t key_value;
+            key_value = PyNumber_AsSsize_t(key, PyExc_IndexError);
+            if (key_value == -1 && PyErr_Occurred())
+                return -1;
+            return PySequence_SetItem(o, key_value, value);
+        }
+        else if (o->ob_type->tp_as_sequence->sq_ass_item) {
+            type_error("sequence index must be "
+                       "integer, not '%.200s'", key);
+            return -1;
+        }
+    }
+
+    type_error("'%.200s' object does not support item assignment", o);
+    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 (PyIndex_Check(key)) {
+            Py_ssize_t key_value;
+            key_value = PyNumber_AsSsize_t(key, PyExc_IndexError);
+            if (key_value == -1 && PyErr_Occurred())
+                return -1;
+            return PySequence_DelItem(o, key_value);
+        }
+        else if (o->ob_type->tp_as_sequence->sq_ass_item) {
+            type_error("sequence index must be "
+                       "integer, not '%.200s'", key);
+            return -1;
+        }
+    }
+
+    type_error("'%.200s' object does not support item deletion", o);
+    return -1;
+}
+
+int
+PyObject_DelItemString(PyObject *o, char *key)
+{
+    PyObject *okey;
+    int ret;
+
+    if (o == NULL || key == NULL) {
+        null_error();
+        return -1;
+    }
+    okey = PyString_FromString(key);
+    if (okey == NULL)
+        return -1;
+    ret = PyObject_DelItem(o, okey);
+    Py_DECREF(okey);
+    return ret;
+}
+
+int
+PyObject_AsCharBuffer(PyObject *obj,
+                          const char **buffer,
+                          Py_ssize_t *buffer_len)
+{
+    PyBufferProcs *pb;
+    char *pp;
+    Py_ssize_t 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");
+        return -1;
+    }
+    if ((*pb->bf_getsegcount)(obj,NULL) != 1) {
+        PyErr_SetString(PyExc_TypeError,
+                        "expected a single-segment buffer object");
+        return -1;
+    }
+    len = (*pb->bf_getcharbuffer)(obj, 0, &pp);
+    if (len < 0)
+        return -1;
+    *buffer = pp;
+    *buffer_len = len;
+    return 0;
+}
+
+int
+PyObject_CheckReadBuffer(PyObject *obj)
+{
+    PyBufferProcs *pb = obj->ob_type->tp_as_buffer;
+
+    if (pb == NULL ||
+        pb->bf_getreadbuffer == NULL ||
+        pb->bf_getsegcount == NULL ||
+        (*pb->bf_getsegcount)(obj, NULL) != 1)
+        return 0;
+    return 1;
+}
+
+int PyObject_AsReadBuffer(PyObject *obj,
+                          const void **buffer,
+                          Py_ssize_t *buffer_len)
+{
+    PyBufferProcs *pb;
+    void *pp;
+    Py_ssize_t 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");
+        return -1;
+    }
+    if ((*pb->bf_getsegcount)(obj, NULL) != 1) {
+        PyErr_SetString(PyExc_TypeError,
+                        "expected a single-segment buffer object");
+        return -1;
+    }
+    len = (*pb->bf_getreadbuffer)(obj, 0, &pp);
+    if (len < 0)
+        return -1;
+    *buffer = pp;
+    *buffer_len = len;
+    return 0;
+}
+
+int PyObject_AsWriteBuffer(PyObject *obj,
+                           void **buffer,
+                           Py_ssize_t *buffer_len)
+{
+    PyBufferProcs *pb;
+    void*pp;
+    Py_ssize_t 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");
+        return -1;
+    }
+    if ((*pb->bf_getsegcount)(obj, NULL) != 1) {
+        PyErr_SetString(PyExc_TypeError,
+                        "expected a single-segment buffer object");
+        return -1;
+    }
+    len = (*pb->bf_getwritebuffer)(obj,0,&pp);
+    if (len < 0)
+        return -1;
+    *buffer = pp;
+    *buffer_len = len;
+    return 0;
+}
+
+/* Buffer C-API for Python 3.0 */
+
+int
+PyObject_GetBuffer(PyObject *obj, Py_buffer *view, int flags)
+{
+    if (!PyObject_CheckBuffer(obj)) {
+        PyErr_Format(PyExc_TypeError,
+                     "'%100s' does not have the buffer interface",
+                     Py_TYPE(obj)->tp_name);
+        return -1;
+    }
+    return (*(obj->ob_type->tp_as_buffer->bf_getbuffer))(obj, view, flags);
+}
+
+static int
+_IsFortranContiguous(Py_buffer *view)
+{
+    Py_ssize_t sd, dim;
+    int i;
+
+    if (view->ndim == 0) return 1;
+    if (view->strides == NULL) return (view->ndim == 1);
+
+    sd = view->itemsize;
+    if (view->ndim == 1) return (view->shape[0] == 1 ||
+                               sd == view->strides[0]);
+    for (i=0; i<view->ndim; i++) {
+        dim = view->shape[i];
+        if (dim == 0) return 1;
+        if (view->strides[i] != sd) return 0;
+        sd *= dim;
+    }
+    return 1;
+}
+
+static int
+_IsCContiguous(Py_buffer *view)
+{
+    Py_ssize_t sd, dim;
+    int i;
+
+    if (view->ndim == 0) return 1;
+    if (view->strides == NULL) return 1;
+
+    sd = view->itemsize;
+    if (view->ndim == 1) return (view->shape[0] == 1 ||
+                               sd == view->strides[0]);
+    for (i=view->ndim-1; i>=0; i--) {
+        dim = view->shape[i];
+        if (dim == 0) return 1;
+        if (view->strides[i] != sd) return 0;
+        sd *= dim;
+    }
+    return 1;
+}
+
+int
+PyBuffer_IsContiguous(Py_buffer *view, char fort)
+{
+
+    if (view->suboffsets != NULL) return 0;
+
+    if (fort == 'C')
+        return _IsCContiguous(view);
+    else if (fort == 'F')
+        return _IsFortranContiguous(view);
+    else if (fort == 'A')
+        return (_IsCContiguous(view) || _IsFortranContiguous(view));
+    return 0;
+}
+
+
+void*
+PyBuffer_GetPointer(Py_buffer *view, Py_ssize_t *indices)
+{
+    char* pointer;
+    int i;
+    pointer = (char *)view->buf;
+    for (i = 0; i < view->ndim; i++) {
+        pointer += view->strides[i]*indices[i];
+        if ((view->suboffsets != NULL) && (view->suboffsets[i] >= 0)) {
+            pointer = *((char**)pointer) + view->suboffsets[i];
+        }
+    }
+    return (void*)pointer;
+}
+
+
+void
+_Py_add_one_to_index_F(int nd, Py_ssize_t *index, const Py_ssize_t *shape)
+{
+    int k;
+
+    for (k=0; k<nd; k++) {
+        if (index[k] < shape[k]-1) {
+            index[k]++;
+            break;
+        }
+        else {
+            index[k] = 0;
+        }
+    }
+}
+
+void
+_Py_add_one_to_index_C(int nd, Py_ssize_t *index, const Py_ssize_t *shape)
+{
+    int k;
+
+    for (k=nd-1; k>=0; k--) {
+        if (index[k] < shape[k]-1) {
+            index[k]++;
+            break;
+        }
+        else {
+            index[k] = 0;
+        }
+    }
+}
+
+  /* view is not checked for consistency in either of these.  It is
+     assumed that the size of the buffer is view->len in
+     view->len / view->itemsize elements.
+  */
+
+int
+PyBuffer_ToContiguous(void *buf, Py_buffer *view, Py_ssize_t len, char fort)
+{
+    int k;
+    void (*addone)(int, Py_ssize_t *, const Py_ssize_t *);
+    Py_ssize_t *indices, elements;
+    char *dest, *ptr;
+
+    if (len > view->len) {
+        len = view->len;
+    }
+
+    if (PyBuffer_IsContiguous(view, fort)) {
+        /* simplest copy is all that is needed */
+        memcpy(buf, view->buf, len);
+        return 0;
+    }
+
+    /* Otherwise a more elaborate scheme is needed */
+
+    /* XXX(nnorwitz): need to check for overflow! */
+    indices = (Py_ssize_t *)PyMem_Malloc(sizeof(Py_ssize_t)*(view->ndim));
+    if (indices == NULL) {
+        PyErr_NoMemory();
+        return -1;
+    }
+    for (k=0; k<view->ndim;k++) {
+        indices[k] = 0;
+    }
+
+    if (fort == 'F') {
+        addone = _Py_add_one_to_index_F;
+    }
+    else {
+        addone = _Py_add_one_to_index_C;
+    }
+    dest = buf;
+    /* XXX : This is not going to be the fastest code in the world
+             several optimizations are possible.
+     */
+    elements = len / view->itemsize;
+    while (elements--) {
+        addone(view->ndim, indices, view->shape);
+        ptr = PyBuffer_GetPointer(view, indices);
+        memcpy(dest, ptr, view->itemsize);
+        dest += view->itemsize;
+    }
+    PyMem_Free(indices);
+    return 0;
+}
+
+int
+PyBuffer_FromContiguous(Py_buffer *view, void *buf, Py_ssize_t len, char fort)
+{
+    int k;
+    void (*addone)(int, Py_ssize_t *, const Py_ssize_t *);
+    Py_ssize_t *indices, elements;
+    char *src, *ptr;
+
+    if (len > view->len) {
+        len = view->len;
+    }
+
+    if (PyBuffer_IsContiguous(view, fort)) {
+        /* simplest copy is all that is needed */
+        memcpy(view->buf, buf, len);
+        return 0;
+    }
+
+    /* Otherwise a more elaborate scheme is needed */
+
+    /* XXX(nnorwitz): need to check for overflow! */
+    indices = (Py_ssize_t *)PyMem_Malloc(sizeof(Py_ssize_t)*(view->ndim));
+    if (indices == NULL) {
+        PyErr_NoMemory();
+        return -1;
+    }
+    for (k=0; k<view->ndim;k++) {
+        indices[k] = 0;
+    }
+
+    if (fort == 'F') {
+        addone = _Py_add_one_to_index_F;
+    }
+    else {
+        addone = _Py_add_one_to_index_C;
+    }
+    src = buf;
+    /* XXX : This is not going to be the fastest code in the world
+             several optimizations are possible.
+     */
+    elements = len / view->itemsize;
+    while (elements--) {
+        addone(view->ndim, indices, view->shape);
+        ptr = PyBuffer_GetPointer(view, indices);
+        memcpy(ptr, src, view->itemsize);
+        src += view->itemsize;
+    }
+
+    PyMem_Free(indices);
+    return 0;
+}
+
+int PyObject_CopyData(PyObject *dest, PyObject *src)
+{
+    Py_buffer view_dest, view_src;
+    int k;
+    Py_ssize_t *indices, elements;
+    char *dptr, *sptr;
+
+    if (!PyObject_CheckBuffer(dest) ||
+        !PyObject_CheckBuffer(src)) {
+        PyErr_SetString(PyExc_TypeError,
+                        "both destination and source must have the "\
+                        "buffer interface");
+        return -1;
+    }
+
+    if (PyObject_GetBuffer(dest, &view_dest, PyBUF_FULL) != 0) return -1;
+    if (PyObject_GetBuffer(src, &view_src, PyBUF_FULL_RO) != 0) {
+        PyBuffer_Release(&view_dest);
+        return -1;
+    }
+
+    if (view_dest.len < view_src.len) {
+        PyErr_SetString(PyExc_BufferError,
+                        "destination is too small to receive data from source");
+        PyBuffer_Release(&view_dest);
+        PyBuffer_Release(&view_src);
+        return -1;
+    }
+
+    if ((PyBuffer_IsContiguous(&view_dest, 'C') &&
+         PyBuffer_IsContiguous(&view_src, 'C')) ||
+        (PyBuffer_IsContiguous(&view_dest, 'F') &&
+         PyBuffer_IsContiguous(&view_src, 'F'))) {
+        /* simplest copy is all that is needed */
+        memcpy(view_dest.buf, view_src.buf, view_src.len);
+        PyBuffer_Release(&view_dest);
+        PyBuffer_Release(&view_src);
+        return 0;
+    }
+
+    /* Otherwise a more elaborate copy scheme is needed */
+
+    /* XXX(nnorwitz): need to check for overflow! */
+    indices = (Py_ssize_t *)PyMem_Malloc(sizeof(Py_ssize_t)*view_src.ndim);
+    if (indices == NULL) {
+        PyErr_NoMemory();
+        PyBuffer_Release(&view_dest);
+        PyBuffer_Release(&view_src);
+        return -1;
+    }
+    for (k=0; k<view_src.ndim;k++) {
+        indices[k] = 0;
+    }
+    elements = 1;
+    for (k=0; k<view_src.ndim; k++) {
+        /* XXX(nnorwitz): can this overflow? */
+        elements *= view_src.shape[k];
+    }
+    while (elements--) {
+        _Py_add_one_to_index_C(view_src.ndim, indices, view_src.shape);
+        dptr = PyBuffer_GetPointer(&view_dest, indices);
+        sptr = PyBuffer_GetPointer(&view_src, indices);
+        memcpy(dptr, sptr, view_src.itemsize);
+    }
+    PyMem_Free(indices);
+    PyBuffer_Release(&view_dest);
+    PyBuffer_Release(&view_src);
+    return 0;
+}
+
+void
+PyBuffer_FillContiguousStrides(int nd, Py_ssize_t *shape,
+                               Py_ssize_t *strides, int itemsize,
+                               char fort)
+{
+    int k;
+    Py_ssize_t sd;
+
+    sd = itemsize;
+    if (fort == 'F') {
+        for (k=0; k<nd; k++) {
+            strides[k] = sd;
+            sd *= shape[k];
+        }
+    }
+    else {
+        for (k=nd-1; k>=0; k--) {
+            strides[k] = sd;
+            sd *= shape[k];
+        }
+    }
+    return;
+}
+
+int
+PyBuffer_FillInfo(Py_buffer *view, PyObject *obj, void *buf, Py_ssize_t len,
+              int readonly, int flags)
+{
+    if (view == NULL) return 0;
+    if (((flags & PyBUF_WRITABLE) == PyBUF_WRITABLE) &&
+        (readonly == 1)) {
+        PyErr_SetString(PyExc_BufferError,
+                        "Object is not writable.");
+        return -1;
+    }
+
+    view->obj = obj;
+    if (obj)
+        Py_INCREF(obj);
+    view->buf = buf;
+    view->len = len;
+    view->readonly = readonly;
+    view->itemsize = 1;
+    view->format = NULL;
+    if ((flags & PyBUF_FORMAT) == PyBUF_FORMAT)
+        view->format = "B";
+    view->ndim = 1;
+    view->shape = NULL;
+    if ((flags & PyBUF_ND) == PyBUF_ND)
+        view->shape = &(view->len);
+    view->strides = NULL;
+    if ((flags & PyBUF_STRIDES) == PyBUF_STRIDES)
+        view->strides = &(view->itemsize);
+    view->suboffsets = NULL;
+    view->internal = NULL;
+    return 0;
+}
+
+void
+PyBuffer_Release(Py_buffer *view)
+{
+    PyObject *obj = view->obj;
+    if (obj && Py_TYPE(obj)->tp_as_buffer && Py_TYPE(obj)->tp_as_buffer->bf_releasebuffer)
+        Py_TYPE(obj)->tp_as_buffer->bf_releasebuffer(obj, view);
+    Py_XDECREF(obj);
+    view->obj = NULL;
+}
+
+PyObject *
+PyObject_Format(PyObject* obj, PyObject *format_spec)
+{
+    PyObject *empty = NULL;
+    PyObject *result = NULL;
+#ifdef Py_USING_UNICODE
+    int spec_is_unicode;
+    int result_is_unicode;
+#endif
+
+    /* If no format_spec is provided, use an empty string */
+    if (format_spec == NULL) {
+        empty = PyString_FromStringAndSize(NULL, 0);
+        format_spec = empty;
+    }
+
+    /* Check the format_spec type, and make sure it's str or unicode */
+#ifdef Py_USING_UNICODE
+    if (PyUnicode_Check(format_spec))
+        spec_is_unicode = 1;
+    else if (PyString_Check(format_spec))
+        spec_is_unicode = 0;
+    else {
+#else
+    if (!PyString_Check(format_spec)) {
+#endif
+        PyErr_Format(PyExc_TypeError,
+                     "format expects arg 2 to be string "
+                     "or unicode, not %.100s", Py_TYPE(format_spec)->tp_name);
+        goto done;
+    }
+
+    /* Check for a __format__ method and call it. */
+    if (PyInstance_Check(obj)) {
+        /* We're an instance of a classic class */
+        PyObject *bound_method = PyObject_GetAttrString(obj, "__format__");
+        if (bound_method != NULL) {
+            result = PyObject_CallFunctionObjArgs(bound_method,
+                                                  format_spec,
+                                                  NULL);
+            Py_DECREF(bound_method);
+        } else {
+            PyObject *self_as_str = NULL;
+            PyObject *format_method = NULL;
+            Py_ssize_t format_len;
+
+            PyErr_Clear();
+            /* Per the PEP, convert to str (or unicode,
+               depending on the type of the format
+               specifier).  For new-style classes, this
+               logic is done by object.__format__(). */
+#ifdef Py_USING_UNICODE
+            if (spec_is_unicode) {
+                format_len = PyUnicode_GET_SIZE(format_spec);
+                self_as_str = PyObject_Unicode(obj);
+            } else
+#endif
+            {
+                format_len = PyString_GET_SIZE(format_spec);
+                self_as_str = PyObject_Str(obj);
+            }
+            if (self_as_str == NULL)
+                goto done1;
+
+            if (format_len > 0) {
+                /* See the almost identical code in
+                   typeobject.c for new-style
+                   classes. */
+                if (PyErr_WarnEx(
+                    PyExc_PendingDeprecationWarning,
+                    "object.__format__ with a non-empty "
+                    "format string is deprecated", 1)
+                     < 0) {
+                    goto done1;
+                }
+                /* Eventually this will become an
+                   error:
+                PyErr_Format(PyExc_TypeError,
+                   "non-empty format string passed to "
+                   "object.__format__");
+                goto done1;
+                */
+            }
+
+            /* Then call str.__format__ on that result */
+            format_method = PyObject_GetAttrString(self_as_str, "__format__");
+            if (format_method == NULL) {
+                goto done1;
+            }
+            result = PyObject_CallFunctionObjArgs(format_method,
+                                                  format_spec,
+                                                  NULL);
+done1:
+            Py_XDECREF(self_as_str);
+            Py_XDECREF(format_method);
+            if (result == NULL)
+                goto done;
+        }
+    } else {
+        /* Not an instance of a classic class, use the code
+           from py3k */
+        static PyObject *format_cache = NULL;
+
+        /* Find the (unbound!) __format__ method (a borrowed
+           reference) */
+        PyObject *method = _PyObject_LookupSpecial(obj, "__format__",
+                                                   &format_cache);
+        if (method == NULL) {
+            if (!PyErr_Occurred())
+                PyErr_Format(PyExc_TypeError,
+                             "Type %.100s doesn't define __format__",
+                             Py_TYPE(obj)->tp_name);
+            goto done;
+        }
+        /* And call it. */
+        result = PyObject_CallFunctionObjArgs(method, format_spec, NULL);
+        Py_DECREF(method);
+    }
+
+    if (result == NULL)
+        goto done;
+
+    /* Check the result type, and make sure it's str or unicode */
+#ifdef Py_USING_UNICODE
+    if (PyUnicode_Check(result))
+        result_is_unicode = 1;
+    else if (PyString_Check(result))
+        result_is_unicode = 0;
+    else {
+#else
+    if (!PyString_Check(result)) {
+#endif
+        PyErr_Format(PyExc_TypeError,
+                     "%.100s.__format__ must return string or "
+                     "unicode, not %.100s", Py_TYPE(obj)->tp_name,
+                     Py_TYPE(result)->tp_name);
+        Py_DECREF(result);
+        result = NULL;
+        goto done;
+    }
+
+    /* Convert to unicode, if needed.  Required if spec is unicode
+       and result is str */
+#ifdef Py_USING_UNICODE
+    if (spec_is_unicode && !result_is_unicode) {
+        PyObject *tmp = PyObject_Unicode(result);
+        /* This logic works whether or not tmp is NULL */
+        Py_DECREF(result);
+        result = tmp;
+    }
+#endif
+
+done:
+    Py_XDECREF(empty);
+    return result;
+}
+
+/* Operations on numbers */
+
+int
+PyNumber_Check(PyObject *o)
+{
+    return o && o->ob_type->tp_as_number &&
+           (o->ob_type->tp_as_number->nb_int ||
+        o->ob_type->tp_as_number->nb_float);
+}
+
+/* Binary operators */
+
+/* New style number protocol support */
+
+#define NB_SLOT(x) offsetof(PyNumberMethods, x)
+#define NB_BINOP(nb_methods, slot) \
+        (*(binaryfunc*)(& ((char*)nb_methods)[slot]))
+#define NB_TERNOP(nb_methods, slot) \
+        (*(ternaryfunc*)(& ((char*)nb_methods)[slot]))
+
+/*
+  Calling scheme used for binary operations:
+
+  v     w       Action
+  -------------------------------------------------------------------
+  new   new     w.op(v,w)[*], v.op(v,w), w.op(v,w)
+  new   old     v.op(v,w), coerce(v,w), v.op(v,w)
+  old   new     w.op(v,w), coerce(v,w), v.op(v,w)
+  old   old     coerce(v,w), v.op(v,w)
+
+  [*] only when v->ob_type != w->ob_type && w->ob_type is a subclass of
+      v->ob_type
+
+  Legend:
+  -------
+  * new == new style number
+  * old == old style number
+  * Action indicates the order in which operations are tried until either
+    a valid result is produced or an error occurs.
+
+ */
+
+static PyObject *
+binary_op1(PyObject *v, PyObject *w, const int op_slot)
+{
+    PyObject *x;
+    binaryfunc slotv = NULL;
+    binaryfunc slotw = NULL;
+
+    if (v->ob_type->tp_as_number != NULL && NEW_STYLE_NUMBER(v))
+        slotv = NB_BINOP(v->ob_type->tp_as_number, op_slot);
+    if (w->ob_type != v->ob_type &&
+        w->ob_type->tp_as_number != NULL && NEW_STYLE_NUMBER(w)) {
+        slotw = NB_BINOP(w->ob_type->tp_as_number, op_slot);
+        if (slotw == slotv)
+            slotw = NULL;
+    }
+    if (slotv) {
+        if (slotw && PyType_IsSubtype(w->ob_type, v->ob_type)) {
+            x = slotw(v, w);
+            if (x != Py_NotImplemented)
+                return x;
+            Py_DECREF(x); /* can't do it */
+            slotw = NULL;
+        }
+        x = slotv(v, w);
+        if (x != Py_NotImplemented)
+            return x;
+        Py_DECREF(x); /* can't do it */
+    }
+    if (slotw) {
+        x = slotw(v, w);
+        if (x != Py_NotImplemented)
+            return x;
+        Py_DECREF(x); /* can't do it */
+    }
+    if (!NEW_STYLE_NUMBER(v) || !NEW_STYLE_NUMBER(w)) {
+        int err = PyNumber_CoerceEx(&v, &w);
+        if (err < 0) {
+            return NULL;
+        }
+        if (err == 0) {
+            PyNumberMethods *mv = v->ob_type->tp_as_number;
+            if (mv) {
+                binaryfunc slot;
+                slot = NB_BINOP(mv, op_slot);
+                if (slot) {
+                    x = slot(v, w);
+                    Py_DECREF(v);
+                    Py_DECREF(w);
+                    return x;
+                }
+            }
+            /* CoerceEx incremented the reference counts */
+            Py_DECREF(v);
+            Py_DECREF(w);
+        }
+    }
+    Py_INCREF(Py_NotImplemented);
+    return Py_NotImplemented;
+}
+
+static PyObject *
+binop_type_error(PyObject *v, PyObject *w, const char *op_name)
+{
+    PyErr_Format(PyExc_TypeError,
+                 "unsupported operand type(s) for %.100s: "
+                 "'%.100s' and '%.100s'",
+                 op_name,
+                 v->ob_type->tp_name,
+                 w->ob_type->tp_name);
+    return NULL;
+}
+
+static PyObject *
+binary_op(PyObject *v, PyObject *w, const int op_slot, const char *op_name)
+{
+    PyObject *result = binary_op1(v, w, op_slot);
+    if (result == Py_NotImplemented) {
+        Py_DECREF(result);
+        return binop_type_error(v, w, op_name);
+    }
+    return result;
+}
+
+
+/*
+  Calling scheme used for ternary operations:
+
+  *** In some cases, w.op is called before v.op; see binary_op1. ***
+
+  v     w       z       Action
+  -------------------------------------------------------------------
+  new   new     new     v.op(v,w,z), w.op(v,w,z), z.op(v,w,z)
+  new   old     new     v.op(v,w,z), z.op(v,w,z), coerce(v,w,z), v.op(v,w,z)
+  old   new     new     w.op(v,w,z), z.op(v,w,z), coerce(v,w,z), v.op(v,w,z)
+  old   old     new     z.op(v,w,z), coerce(v,w,z), v.op(v,w,z)
+  new   new     old     v.op(v,w,z), w.op(v,w,z), coerce(v,w,z), v.op(v,w,z)
+  new   old     old     v.op(v,w,z), coerce(v,w,z), v.op(v,w,z)
+  old   new     old     w.op(v,w,z), coerce(v,w,z), v.op(v,w,z)
+  old   old     old     coerce(v,w,z), v.op(v,w,z)
+
+  Legend:
+  -------
+  * new == new style number
+  * old == old style number
+  * Action indicates the order in which operations are tried until either
+    a valid result is produced or an error occurs.
+  * coerce(v,w,z) actually does: coerce(v,w), coerce(v,z), coerce(w,z) and
+    only if z != Py_None; if z == Py_None, then it is treated as absent
+    variable and only coerce(v,w) is tried.
+
+ */
+
+static PyObject *
+ternary_op(PyObject *v,
+           PyObject *w,
+           PyObject *z,
+           const int op_slot,
+           const char *op_name)
+{
+    PyNumberMethods *mv, *mw, *mz;
+    PyObject *x = NULL;
+    ternaryfunc slotv = NULL;
+    ternaryfunc slotw = NULL;
+    ternaryfunc slotz = NULL;
+
+    mv = v->ob_type->tp_as_number;
+    mw = w->ob_type->tp_as_number;
+    if (mv != NULL && NEW_STYLE_NUMBER(v))
+        slotv = NB_TERNOP(mv, op_slot);
+    if (w->ob_type != v->ob_type &&
+        mw != NULL && NEW_STYLE_NUMBER(w)) {
+        slotw = NB_TERNOP(mw, op_slot);
+        if (slotw == slotv)
+            slotw = NULL;
+    }
+    if (slotv) {
+        if (slotw && PyType_IsSubtype(w->ob_type, v->ob_type)) {
+            x = slotw(v, w, z);
+            if (x != Py_NotImplemented)
+                return x;
+            Py_DECREF(x); /* can't do it */
+            slotw = NULL;
+        }
+        x = slotv(v, w, z);
+        if (x != Py_NotImplemented)
+            return x;
+        Py_DECREF(x); /* can't do it */
+    }
+    if (slotw) {
+        x = slotw(v, w, z);
+        if (x != Py_NotImplemented)
+            return x;
+        Py_DECREF(x); /* can't do it */
+    }
+    mz = z->ob_type->tp_as_number;
+    if (mz != NULL && NEW_STYLE_NUMBER(z)) {
+        slotz = NB_TERNOP(mz, op_slot);
+        if (slotz == slotv || slotz == slotw)
+            slotz = NULL;
+        if (slotz) {
+            x = slotz(v, w, z);
+            if (x != Py_NotImplemented)
+                return x;
+            Py_DECREF(x); /* can't do it */
+        }
+    }
+
+    if (!NEW_STYLE_NUMBER(v) || !NEW_STYLE_NUMBER(w) ||
+                    (z != Py_None && !NEW_STYLE_NUMBER(z))) {
+        /* we have an old style operand, coerce */
+        PyObject *v1, *z1, *w2, *z2;
+        int c;
+
+        c = PyNumber_Coerce(&v, &w);
+        if (c != 0)
+            goto error3;
+
+        /* Special case: if the third argument is None, it is
+           treated as absent argument and not coerced. */
+        if (z == Py_None) {
+            if (v->ob_type->tp_as_number) {
+                slotz = NB_TERNOP(v->ob_type->tp_as_number,
+                                  op_slot);
+                if (slotz)
+                    x = slotz(v, w, z);
+                else
+                    c = -1;
+            }
+            else
+                c = -1;
+            goto error2;
+        }
+        v1 = v;
+        z1 = z;
+        c = PyNumber_Coerce(&v1, &z1);
+        if (c != 0)
+            goto error2;
+        w2 = w;
+        z2 = z1;
+        c = PyNumber_Coerce(&w2, &z2);
+        if (c != 0)
+            goto error1;
+
+        if (v1->ob_type->tp_as_number != NULL) {
+            slotv = NB_TERNOP(v1->ob_type->tp_as_number,
+                              op_slot);
+            if (slotv)
+                x = slotv(v1, w2, z2);
+            else
+                c = -1;
+        }
+        else
+            c = -1;
+
+        Py_DECREF(w2);
+        Py_DECREF(z2);
+    error1:
+        Py_DECREF(v1);
+        Py_DECREF(z1);
+    error2:
+        Py_DECREF(v);
+        Py_DECREF(w);
+    error3:
+        if (c >= 0)
+            return x;
+    }
+
+    if (z == Py_None)
+        PyErr_Format(
+            PyExc_TypeError,
+            "unsupported operand type(s) for ** or pow(): "
+            "'%.100s' and '%.100s'",
+            v->ob_type->tp_name,
+            w->ob_type->tp_name);
+    else
+        PyErr_Format(
+            PyExc_TypeError,
+            "unsupported operand type(s) for pow(): "
+            "'%.100s', '%.100s', '%.100s'",
+            v->ob_type->tp_name,
+            w->ob_type->tp_name,
+            z->ob_type->tp_name);
+    return NULL;
+}
+
+#define BINARY_FUNC(func, op, op_name) \
+    PyObject * \
+    func(PyObject *v, PyObject *w) { \
+        return binary_op(v, w, NB_SLOT(op), op_name); \
+    }
+
+BINARY_FUNC(PyNumber_Or, nb_or, "|")
+BINARY_FUNC(PyNumber_Xor, nb_xor, "^")
+BINARY_FUNC(PyNumber_And, nb_and, "&")
+BINARY_FUNC(PyNumber_Lshift, nb_lshift, "<<")
+BINARY_FUNC(PyNumber_Rshift, nb_rshift, ">>")
+BINARY_FUNC(PyNumber_Subtract, nb_subtract, "-")
+BINARY_FUNC(PyNumber_Divide, nb_divide, "/")
+BINARY_FUNC(PyNumber_Divmod, nb_divmod, "divmod()")
+
+PyObject *
+PyNumber_Add(PyObject *v, PyObject *w)
+{
+    PyObject *result = binary_op1(v, w, NB_SLOT(nb_add));
+    if (result == Py_NotImplemented) {
+        PySequenceMethods *m = v->ob_type->tp_as_sequence;
+        Py_DECREF(result);
+        if (m && m->sq_concat) {
+            return (*m->sq_concat)(v, w);
+        }
+        result = binop_type_error(v, w, "+");
+    }
+    return result;
+}
+
+static PyObject *
+sequence_repeat(ssizeargfunc repeatfunc, PyObject *seq, PyObject *n)
+{
+    Py_ssize_t count;
+    if (PyIndex_Check(n)) {
+        count = PyNumber_AsSsize_t(n, PyExc_OverflowError);
+        if (count == -1 && PyErr_Occurred())
+            return NULL;
+    }
+    else {
+        return type_error("can't multiply sequence by "
+                          "non-int of type '%.200s'", n);
+    }
+    return (*repeatfunc)(seq, count);
+}
+
+PyObject *
+PyNumber_Multiply(PyObject *v, PyObject *w)
+{
+    PyObject *result = binary_op1(v, w, NB_SLOT(nb_multiply));
+    if (result == Py_NotImplemented) {
+        PySequenceMethods *mv = v->ob_type->tp_as_sequence;
+        PySequenceMethods *mw = w->ob_type->tp_as_sequence;
+        Py_DECREF(result);
+        if  (mv && mv->sq_repeat) {
+            return sequence_repeat(mv->sq_repeat, v, w);
+        }
+        else if (mw && mw->sq_repeat) {
+            return sequence_repeat(mw->sq_repeat, w, v);
+        }
+        result = binop_type_error(v, w, "*");
+    }
+    return result;
+}
+
+PyObject *
+PyNumber_FloorDivide(PyObject *v, PyObject *w)
+{
+    /* XXX tp_flags test */
+    return binary_op(v, w, NB_SLOT(nb_floor_divide), "//");
+}
+
+PyObject *
+PyNumber_TrueDivide(PyObject *v, PyObject *w)
+{
+    /* XXX tp_flags test */
+    return binary_op(v, w, NB_SLOT(nb_true_divide), "/");
+}
+
+PyObject *
+PyNumber_Remainder(PyObject *v, PyObject *w)
+{
+    return binary_op(v, w, NB_SLOT(nb_remainder), "%");
+}
+
+PyObject *
+PyNumber_Power(PyObject *v, PyObject *w, PyObject *z)
+{
+    return ternary_op(v, w, z, NB_SLOT(nb_power), "** or pow()");
+}
+
+/* Binary in-place operators */
+
+/* The in-place operators are defined to fall back to the 'normal',
+   non in-place operations, if the in-place methods are not in place.
+
+   - If the left hand object has the appropriate struct members, and
+     they are filled, call the appropriate function and return the
+     result.  No coercion is done on the arguments; the left-hand object
+     is the one the operation is performed on, and it's up to the
+     function to deal with the right-hand object.
+
+   - Otherwise, in-place modification is not supported. Handle it exactly as
+     a non in-place operation of the same kind.
+
+   */
+
+#define HASINPLACE(t) \
+    PyType_HasFeature((t)->ob_type, Py_TPFLAGS_HAVE_INPLACEOPS)
+
+static PyObject *
+binary_iop1(PyObject *v, PyObject *w, const int iop_slot, const int op_slot)
+{
+    PyNumberMethods *mv = v->ob_type->tp_as_number;
+    if (mv != NULL && HASINPLACE(v)) {
+        binaryfunc slot = NB_BINOP(mv, iop_slot);
+        if (slot) {
+            PyObject *x = (slot)(v, w);
+            if (x != Py_NotImplemented) {
+                return x;
+            }
+            Py_DECREF(x);
+        }
+    }
+    return binary_op1(v, w, op_slot);
+}
+
+static PyObject *
+binary_iop(PyObject *v, PyObject *w, const int iop_slot, const int op_slot,
+                const char *op_name)
+{
+    PyObject *result = binary_iop1(v, w, iop_slot, op_slot);
+    if (result == Py_NotImplemented) {
+        Py_DECREF(result);
+        return binop_type_error(v, w, op_name);
+    }
+    return result;
+}
+
+#define INPLACE_BINOP(func, iop, op, op_name) \
+    PyObject * \
+    func(PyObject *v, PyObject *w) { \
+        return binary_iop(v, w, NB_SLOT(iop), NB_SLOT(op), op_name); \
+    }
+
+INPLACE_BINOP(PyNumber_InPlaceOr, nb_inplace_or, nb_or, "|=")
+INPLACE_BINOP(PyNumber_InPlaceXor, nb_inplace_xor, nb_xor, "^=")
+INPLACE_BINOP(PyNumber_InPlaceAnd, nb_inplace_and, nb_and, "&=")
+INPLACE_BINOP(PyNumber_InPlaceLshift, nb_inplace_lshift, nb_lshift, "<<=")
+INPLACE_BINOP(PyNumber_InPlaceRshift, nb_inplace_rshift, nb_rshift, ">>=")
+INPLACE_BINOP(PyNumber_InPlaceSubtract, nb_inplace_subtract, nb_subtract, "-=")
+INPLACE_BINOP(PyNumber_InPlaceDivide, nb_inplace_divide, nb_divide, "/=")
+
+PyObject *
+PyNumber_InPlaceFloorDivide(PyObject *v, PyObject *w)
+{
+    /* XXX tp_flags test */
+    return binary_iop(v, w, NB_SLOT(nb_inplace_floor_divide),
+                      NB_SLOT(nb_floor_divide), "//=");
+}
+
+PyObject *
+PyNumber_InPlaceTrueDivide(PyObject *v, PyObject *w)
+{
+    /* XXX tp_flags test */
+    return binary_iop(v, w, NB_SLOT(nb_inplace_true_divide),
+                      NB_SLOT(nb_true_divide), "/=");
+}
+
+PyObject *
+PyNumber_InPlaceAdd(PyObject *v, PyObject *w)
+{
+    PyObject *result = binary_iop1(v, w, NB_SLOT(nb_inplace_add),
+                                   NB_SLOT(nb_add));
+    if (result == Py_NotImplemented) {
+        PySequenceMethods *m = v->ob_type->tp_as_sequence;
+        Py_DECREF(result);
+        if (m != NULL) {
+            binaryfunc f = NULL;
+            if (HASINPLACE(v))
+                f = m->sq_inplace_concat;
+            if (f == NULL)
+                f = m->sq_concat;
+            if (f != NULL)
+                return (*f)(v, w);
+        }
+        result = binop_type_error(v, w, "+=");
+    }
+    return result;
+}
+
+PyObject *
+PyNumber_InPlaceMultiply(PyObject *v, PyObject *w)
+{
+    PyObject *result = binary_iop1(v, w, NB_SLOT(nb_inplace_multiply),
+                                   NB_SLOT(nb_multiply));
+    if (result == Py_NotImplemented) {
+        ssizeargfunc f = NULL;
+        PySequenceMethods *mv = v->ob_type->tp_as_sequence;
+        PySequenceMethods *mw = w->ob_type->tp_as_sequence;
+        Py_DECREF(result);
+        if (mv != NULL) {
+            if (HASINPLACE(v))
+                f = mv->sq_inplace_repeat;
+            if (f == NULL)
+                f = mv->sq_repeat;
+            if (f != NULL)
+                return sequence_repeat(f, v, w);
+        }
+        else if (mw != NULL) {
+            /* Note that the right hand operand should not be
+             * mutated in this case so sq_inplace_repeat is not
+             * used. */
+            if (mw->sq_repeat)
+                return sequence_repeat(mw->sq_repeat, w, v);
+        }
+        result = binop_type_error(v, w, "*=");
+    }
+    return result;
+}
+
+PyObject *
+PyNumber_InPlaceRemainder(PyObject *v, PyObject *w)
+{
+    return binary_iop(v, w, NB_SLOT(nb_inplace_remainder),
+                            NB_SLOT(nb_remainder), "%=");
+}
+
+PyObject *
+PyNumber_InPlacePower(PyObject *v, PyObject *w, PyObject *z)
+{
+    if (HASINPLACE(v) && v->ob_type->tp_as_number &&
+        v->ob_type->tp_as_number->nb_inplace_power != NULL) {
+        return ternary_op(v, w, z, NB_SLOT(nb_inplace_power), "**=");
+    }
+    else {
+        return ternary_op(v, w, z, NB_SLOT(nb_power), "**=");
+    }
+}
+
+
+/* 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 -: '%.200s'", o);
+}
+
+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 +: '%.200s'", o);
+}
+
+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 ~: '%.200s'", o);
+}
+
+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(): '%.200s'", o);
+}
+
+/* Add a check for embedded NULL-bytes in the argument. */
+static PyObject *
+int_from_string(const char *s, Py_ssize_t 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;
+}
+
+/* Return a Python Int or Long from the object item
+   Raise TypeError if the result is not an int-or-long
+   or if the object cannot be interpreted as an index.
+*/
+PyObject *
+PyNumber_Index(PyObject *item)
+{
+    PyObject *result = NULL;
+    if (item == NULL)
+        return null_error();
+    if (PyInt_Check(item) || PyLong_Check(item)) {
+        Py_INCREF(item);
+        return item;
+    }
+    if (PyIndex_Check(item)) {
+        result = item->ob_type->tp_as_number->nb_index(item);
+        if (result &&
+            !PyInt_Check(result) && !PyLong_Check(result)) {
+            PyErr_Format(PyExc_TypeError,
+                         "__index__ returned non-(int,long) " \
+                         "(type %.200s)",
+                         result->ob_type->tp_name);
+            Py_DECREF(result);
+            return NULL;
+        }
+    }
+    else {
+        PyErr_Format(PyExc_TypeError,
+                     "'%.200s' object cannot be interpreted "
+                     "as an index", item->ob_type->tp_name);
+    }
+    return result;
+}
+
+/* Return an error on Overflow only if err is not NULL*/
+
+Py_ssize_t
+PyNumber_AsSsize_t(PyObject *item, PyObject *err)
+{
+    Py_ssize_t result;
+    PyObject *runerr;
+    PyObject *value = PyNumber_Index(item);
+    if (value == NULL)
+        return -1;
+
+    /* We're done if PyInt_AsSsize_t() returns without error. */
+    result = PyInt_AsSsize_t(value);
+    if (result != -1 || !(runerr = PyErr_Occurred()))
+        goto finish;
+
+    /* Error handling code -- only manage OverflowError differently */
+    if (!PyErr_GivenExceptionMatches(runerr, PyExc_OverflowError))
+        goto finish;
+
+    PyErr_Clear();
+    /* If no error-handling desired then the default clipping
+       is sufficient.
+     */
+    if (!err) {
+        assert(PyLong_Check(value));
+        /* Whether or not it is less than or equal to
+           zero is determined by the sign of ob_size
+        */
+        if (_PyLong_Sign(value) < 0)
+            result = PY_SSIZE_T_MIN;
+        else
+            result = PY_SSIZE_T_MAX;
+    }
+    else {
+        /* Otherwise replace the error with caller's error object. */
+        PyErr_Format(err,
+                     "cannot fit '%.200s' into an index-sized integer",
+                     item->ob_type->tp_name);
+    }
+
+ finish:
+    Py_DECREF(value);
+    return result;
+}
+
+
+PyObject *
+_PyNumber_ConvertIntegralToInt(PyObject *integral, const char* error_format)
+{
+    const char *type_name;
+    static PyObject *int_name = NULL;
+    if (int_name == NULL) {
+        int_name = PyString_InternFromString("__int__");
+        if (int_name == NULL)
+            return NULL;
+    }
+
+    if (integral && (!PyInt_Check(integral) &&
+                     !PyLong_Check(integral))) {
+        /* Don't go through tp_as_number->nb_int to avoid
+           hitting the classic class fallback to __trunc__. */
+        PyObject *int_func = PyObject_GetAttr(integral, int_name);
+        if (int_func == NULL) {
+            PyErr_Clear(); /* Raise a different error. */
+            goto non_integral_error;
+        }
+        Py_DECREF(integral);
+        integral = PyEval_CallObject(int_func, NULL);
+        Py_DECREF(int_func);
+        if (integral && (!PyInt_Check(integral) &&
+                          !PyLong_Check(integral))) {
+            goto non_integral_error;
+        }
+    }
+    return integral;
+
+non_integral_error:
+    if (PyInstance_Check(integral)) {
+        type_name = PyString_AS_STRING(((PyInstanceObject *)integral)
+                                       ->in_class->cl_name);
+    }
+    else {
+        type_name = integral->ob_type->tp_name;
+    }
+    PyErr_Format(PyExc_TypeError, error_format, type_name);
+    Py_DECREF(integral);
+    return NULL;
+}
+
+
+PyObject *
+PyNumber_Int(PyObject *o)
+{
+    PyNumberMethods *m;
+    static PyObject *trunc_name = NULL;
+    PyObject *trunc_func;
+    const char *buffer;
+    Py_ssize_t buffer_len;
+
+    if (trunc_name == NULL) {
+        trunc_name = PyString_InternFromString("__trunc__");
+        if (trunc_name == NULL)
+            return NULL;
+    }
+
+    if (o == NULL)
+        return null_error();
+    if (PyInt_CheckExact(o)) {
+        Py_INCREF(o);
+        return o;
+    }
+    m = o->ob_type->tp_as_number;
+    if (m && m->nb_int) { /* This should include subclasses of int */
+        /* Classic classes always take this branch. */
+        PyObject *res = m->nb_int(o);
+        if (res && (!PyInt_Check(res) && !PyLong_Check(res))) {
+            PyErr_Format(PyExc_TypeError,
+                         "__int__ returned non-int (type %.200s)",
+                         res->ob_type->tp_name);
+            Py_DECREF(res);
+            return NULL;
+        }
+        return res;
+    }
+    if (PyInt_Check(o)) { /* A int subclass without nb_int */
+        PyIntObject *io = (PyIntObject*)o;
+        return PyInt_FromLong(io->ob_ival);
+    }
+    trunc_func = PyObject_GetAttr(o, trunc_name);
+    if (trunc_func) {
+        PyObject *truncated = PyEval_CallObject(trunc_func, NULL);
+        Py_DECREF(trunc_func);
+        /* __trunc__ is specified to return an Integral type, but
+           int() needs to return an int. */
+        return _PyNumber_ConvertIntegralToInt(
+            truncated,
+            "__trunc__ returned non-Integral (type %.200s)");
+    }
+    PyErr_Clear();  /* It's not an error if  o.__trunc__ doesn't exist. */
+
+    if (PyString_Check(o))
+        return int_from_string(PyString_AS_STRING(o),
+                               PyString_GET_SIZE(o));
+#ifdef Py_USING_UNICODE
+    if (PyUnicode_Check(o))
+        return PyInt_FromUnicode(PyUnicode_AS_UNICODE(o),
+                                 PyUnicode_GET_SIZE(o),
+                                 10);
+#endif
+    if (!PyObject_AsCharBuffer(o, &buffer, &buffer_len))
+        return int_from_string((char*)buffer, buffer_len);
+
+    return type_error("int() argument must be a string or a "
+                      "number, not '%.200s'", o);
+}
+
+/* Add a check for embedded NULL-bytes in the argument. */
+static PyObject *
+long_from_string(const char *s, Py_ssize_t 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;
+    static PyObject *trunc_name = NULL;
+    PyObject *trunc_func;
+    const char *buffer;
+    Py_ssize_t buffer_len;
+
+    if (trunc_name == NULL) {
+        trunc_name = PyString_InternFromString("__trunc__");
+        if (trunc_name == NULL)
+            return NULL;
+    }
+
+    if (o == NULL)
+        return null_error();
+    m = o->ob_type->tp_as_number;
+    if (m && m->nb_long) { /* This should include subclasses of long */
+        /* Classic classes always take this branch. */
+        PyObject *res = m->nb_long(o);
+        if (res == NULL)
+            return NULL;
+        if (PyInt_Check(res)) {
+            long value = PyInt_AS_LONG(res);
+            Py_DECREF(res);
+            return PyLong_FromLong(value);
+        }
+        else if (!PyLong_Check(res)) {
+            PyErr_Format(PyExc_TypeError,
+                         "__long__ returned non-long (type %.200s)",
+                         res->ob_type->tp_name);
+            Py_DECREF(res);
+            return NULL;
+        }
+        return res;
+    }
+    if (PyLong_Check(o)) /* A long subclass without nb_long */
+        return _PyLong_Copy((PyLongObject *)o);
+    trunc_func = PyObject_GetAttr(o, trunc_name);
+    if (trunc_func) {
+        PyObject *truncated = PyEval_CallObject(trunc_func, NULL);
+        PyObject *int_instance;
+        Py_DECREF(trunc_func);
+        /* __trunc__ is specified to return an Integral type,
+           but long() needs to return a long. */
+        int_instance = _PyNumber_ConvertIntegralToInt(
+            truncated,
+            "__trunc__ returned non-Integral (type %.200s)");
+        if (int_instance && PyInt_Check(int_instance)) {
+            /* Make sure that long() returns a long instance. */
+            long value = PyInt_AS_LONG(int_instance);
+            Py_DECREF(int_instance);
+            return PyLong_FromLong(value);
+        }
+        return int_instance;
+    }
+    PyErr_Clear();  /* It's not an error if  o.__trunc__ doesn't exist. */
+
+    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));
+#ifdef Py_USING_UNICODE
+    if (PyUnicode_Check(o))
+        /* The above check is done in PyLong_FromUnicode(). */
+        return PyLong_FromUnicode(PyUnicode_AS_UNICODE(o),
+                                  PyUnicode_GET_SIZE(o),
+                                  10);
+#endif
+    if (!PyObject_AsCharBuffer(o, &buffer, &buffer_len))
+        return long_from_string(buffer, buffer_len);
+
+    return type_error("long() argument must be a string or a "
+                      "number, not '%.200s'", o);
+}
+
+PyObject *
+PyNumber_Float(PyObject *o)
+{
+    PyNumberMethods *m;
+
+    if (o == NULL)
+        return null_error();
+    m = o->ob_type->tp_as_number;
+    if (m && m->nb_float) { /* This should include subclasses of float */
+        PyObject *res = m->nb_float(o);
+        if (res && !PyFloat_Check(res)) {
+            PyErr_Format(PyExc_TypeError,
+              "__float__ returned non-float (type %.200s)",
+              res->ob_type->tp_name);
+            Py_DECREF(res);
+            return NULL;
+        }
+        return res;
+    }
+    if (PyFloat_Check(o)) { /* A float subclass with nb_float == NULL */
+        PyFloatObject *po = (PyFloatObject *)o;
+        return PyFloat_FromDouble(po->ob_fval);
+    }
+    return PyFloat_FromString(o, NULL);
+}
+
+PyObject *
+PyNumber_ToBase(PyObject *n, int base)
+{
+    PyObject *res = NULL;
+    PyObject *index = PyNumber_Index(n);
+
+    if (!index)
+        return NULL;
+    if (PyLong_Check(index))
+        res = _PyLong_Format(index, base, 0, 1);
+    else if (PyInt_Check(index))
+        res = _PyInt_Format((PyIntObject*)index, base, 1);
+    else
+        /* It should not be possible to get here, as
+           PyNumber_Index already has a check for the same
+           condition */
+        PyErr_SetString(PyExc_ValueError, "PyNumber_ToBase: index not "
+                        "int or long");
+    Py_DECREF(index);
+    return res;
+}
+
+
+/* Operations on sequences */
+
+int
+PySequence_Check(PyObject *s)
+{
+    if (s == NULL)
+        return 0;
+    if (PyInstance_Check(s))
+        return PyObject_HasAttrString(s, "__getitem__");
+    if (PyDict_Check(s))
+        return 0;
+    return  s->ob_type->tp_as_sequence &&
+        s->ob_type->tp_as_sequence->sq_item != NULL;
+}
+
+Py_ssize_t
+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("object of type '%.200s' has no len()", s);
+    return -1;
+}
+
+#undef PySequence_Length
+Py_ssize_t
+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);
+
+    /* Instances of user classes defining an __add__() method only
+       have an nb_add slot, not an sq_concat slot.  So we fall back
+       to nb_add if both arguments appear to be sequences. */
+    if (PySequence_Check(s) && PySequence_Check(o)) {
+        PyObject *result = binary_op1(s, o, NB_SLOT(nb_add));
+        if (result != Py_NotImplemented)
+            return result;
+        Py_DECREF(result);
+    }
+    return type_error("'%.200s' object can't be concatenated", s);
+}
+
+PyObject *
+PySequence_Repeat(PyObject *o, Py_ssize_t 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);
+
+    /* Instances of user classes defining a __mul__() method only
+       have an nb_multiply slot, not an sq_repeat slot. so we fall back
+       to nb_multiply if o appears to be a sequence. */
+    if (PySequence_Check(o)) {
+        PyObject *n, *result;
+        n = PyInt_FromSsize_t(count);
+        if (n == NULL)
+            return NULL;
+        result = binary_op1(o, n, NB_SLOT(nb_multiply));
+        Py_DECREF(n);
+        if (result != Py_NotImplemented)
+            return result;
+        Py_DECREF(result);
+    }
+    return type_error("'%.200s' object can't be repeated", o);
+}
+
+PyObject *
+PySequence_InPlaceConcat(PyObject *s, PyObject *o)
+{
+    PySequenceMethods *m;
+
+    if (s == NULL || o == NULL)
+        return null_error();
+
+    m = s->ob_type->tp_as_sequence;
+    if (m && HASINPLACE(s) && m->sq_inplace_concat)
+        return m->sq_inplace_concat(s, o);
+    if (m && m->sq_concat)
+        return m->sq_concat(s, o);
+
+    if (PySequence_Check(s) && PySequence_Check(o)) {
+        PyObject *result = binary_iop1(s, o, NB_SLOT(nb_inplace_add),
+                                       NB_SLOT(nb_add));
+        if (result != Py_NotImplemented)
+            return result;
+        Py_DECREF(result);
+    }
+    return type_error("'%.200s' object can't be concatenated", s);
+}
+
+PyObject *
+PySequence_InPlaceRepeat(PyObject *o, Py_ssize_t count)
+{
+    PySequenceMethods *m;
+
+    if (o == NULL)
+        return null_error();
+
+    m = o->ob_type->tp_as_sequence;
+    if (m && HASINPLACE(o) && m->sq_inplace_repeat)
+        return m->sq_inplace_repeat(o, count);
+    if (m && m->sq_repeat)
+        return m->sq_repeat(o, count);
+
+    if (PySequence_Check(o)) {
+        PyObject *n, *result;
+        n = PyInt_FromSsize_t(count);
+        if (n == NULL)
+            return NULL;
+        result = binary_iop1(o, n, NB_SLOT(nb_inplace_multiply),
+                             NB_SLOT(nb_multiply));
+        Py_DECREF(n);
+        if (result != Py_NotImplemented)
+            return result;
+        Py_DECREF(result);
+    }
+    return type_error("'%.200s' object can't be repeated", o);
+}
+
+PyObject *
+PySequence_GetItem(PyObject *s, Py_ssize_t 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) {
+                Py_ssize_t l = (*m->sq_length)(s);
+                if (l < 0)
+                    return NULL;
+                i += l;
+            }
+        }
+        return m->sq_item(s, i);
+    }
+
+    return type_error("'%.200s' object does not support indexing", s);
+}
+
+PyObject *
+PySequence_GetSlice(PyObject *s, Py_ssize_t i1, Py_ssize_t 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) {
+                Py_ssize_t 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 = _PySlice_FromIndices(i1, i2);
+        if (!slice)
+            return NULL;
+        res = mp->mp_subscript(s, slice);
+        Py_DECREF(slice);
+        return res;
+    }
+
+    return type_error("'%.200s' object is unsliceable", s);
+}
+
+int
+PySequence_SetItem(PyObject *s, Py_ssize_t 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) {
+                Py_ssize_t l = (*m->sq_length)(s);
+                if (l < 0)
+                    return -1;
+                i += l;
+            }
+        }
+        return m->sq_ass_item(s, i, o);
+    }
+
+    type_error("'%.200s' object does not support item assignment", s);
+    return -1;
+}
+
+int
+PySequence_DelItem(PyObject *s, Py_ssize_t 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) {
+                Py_ssize_t l = (*m->sq_length)(s);
+                if (l < 0)
+                    return -1;
+                i += l;
+            }
+        }
+        return m->sq_ass_item(s, i, (PyObject *)NULL);
+    }
+
+    type_error("'%.200s' object doesn't support item deletion", s);
+    return -1;
+}
+
+int
+PySequence_SetSlice(PyObject *s, Py_ssize_t i1, Py_ssize_t 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) {
+                Py_ssize_t 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 = _PySlice_FromIndices(i1, i2);
+        if (!slice)
+            return -1;
+        res = mp->mp_ass_subscript(s, slice, o);
+        Py_DECREF(slice);
+        return res;
+    }
+
+    type_error("'%.200s' object doesn't support slice assignment", s);
+    return -1;
+}
+
+int
+PySequence_DelSlice(PyObject *s, Py_ssize_t i1, Py_ssize_t 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) {
+                Py_ssize_t 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("'%.200s' object doesn't support slice deletion", s);
+    return -1;
+}
+
+PyObject *
+PySequence_Tuple(PyObject *v)
+{
+    PyObject *it;  /* iter(v) */
+    Py_ssize_t n;         /* guess for result tuple size */
+    PyObject *result = NULL;
+    Py_ssize_t j;
+
+    if (v == NULL)
+        return null_error();
+
+    /* Special-case the common tuple and list cases, for efficiency. */
+    if (PyTuple_CheckExact(v)) {
+        /* Note that we can't know whether it's safe to return
+           a tuple *subclass* instance as-is, hence the restriction
+           to exact tuples here.  In contrast, lists always make
+           a copy, so there's no need for exactness below. */
+        Py_INCREF(v);
+        return v;
+    }
+    if (PyList_Check(v))
+        return PyList_AsTuple(v);
+
+    /* Get iterator. */
+    it = PyObject_GetIter(v);
+    if (it == NULL)
+        return NULL;
+
+    /* Guess result size and allocate space. */
+    n = _PyObject_LengthHint(v, 10);
+    if (n == -1)
+        goto Fail;
+    result = PyTuple_New(n);
+    if (result == NULL)
+        goto Fail;
+
+    /* Fill the tuple. */
+    for (j = 0; ; ++j) {
+        PyObject *item = PyIter_Next(it);
+        if (item == NULL) {
+            if (PyErr_Occurred())
+                goto Fail;
+            break;
+        }
+        if (j >= n) {
+            Py_ssize_t oldn = n;
+            /* The over-allocation strategy can grow a bit faster
+               than for lists because unlike lists the
+               over-allocation isn't permanent -- we reclaim
+               the excess before the end of this routine.
+               So, grow by ten and then add 25%.
+            */
+            n += 10;
+            n += n >> 2;
+            if (n < oldn) {
+                /* Check for overflow */
+                PyErr_NoMemory();
+                Py_DECREF(item);
+                goto Fail;
+            }
+            if (_PyTuple_Resize(&result, n) != 0) {
+                Py_DECREF(item);
+                goto Fail;
+            }
+        }
+        PyTuple_SET_ITEM(result, j, item);
+    }
+
+    /* Cut tuple back if guess was too large. */
+    if (j < n &&
+        _PyTuple_Resize(&result, j) != 0)
+        goto Fail;
+
+    Py_DECREF(it);
+    return result;
+
+Fail:
+    Py_XDECREF(result);
+    Py_DECREF(it);
+    return NULL;
+}
+
+PyObject *
+PySequence_List(PyObject *v)
+{
+    PyObject *result;  /* result list */
+    PyObject *rv;      /* return value from PyList_Extend */
+
+    if (v == NULL)
+        return null_error();
+
+    result = PyList_New(0);
+    if (result == NULL)
+        return NULL;
+
+    rv = _PyList_Extend((PyListObject *)result, v);
+    if (rv == NULL) {
+        Py_DECREF(result);
+        return NULL;
+    }
+    Py_DECREF(rv);
+    return result;
+}
+
+PyObject *
+PySequence_Fast(PyObject *v, const char *m)
+{
+    PyObject *it;
+
+    if (v == NULL)
+        return null_error();
+
+    if (PyList_CheckExact(v) || PyTuple_CheckExact(v)) {
+        Py_INCREF(v);
+        return v;
+    }
+
+    it = PyObject_GetIter(v);
+    if (it == NULL) {
+        if (PyErr_ExceptionMatches(PyExc_TypeError))
+            PyErr_SetString(PyExc_TypeError, m);
+        return NULL;
+    }
+
+    v = PySequence_List(it);
+    Py_DECREF(it);
+
+    return v;
+}
+
+/* Iterate over seq.  Result depends on the operation:
+   PY_ITERSEARCH_COUNT:  -1 if error, else # of times obj appears in seq.
+   PY_ITERSEARCH_INDEX:  0-based index of first occurrence of obj in seq;
+    set ValueError and return -1 if none found; also return -1 on error.
+   Py_ITERSEARCH_CONTAINS:  return 1 if obj in seq, else 0; -1 on error.
+*/
+Py_ssize_t
+_PySequence_IterSearch(PyObject *seq, PyObject *obj, int operation)
+{
+    Py_ssize_t n;
+    int wrapped;  /* for PY_ITERSEARCH_INDEX, true iff n wrapped around */
+    PyObject *it;  /* iter(seq) */
+
+    if (seq == NULL || obj == NULL) {
+        null_error();
+        return -1;
+    }
+
+    it = PyObject_GetIter(seq);
+    if (it == NULL) {
+        type_error("argument of type '%.200s' is not iterable", seq);
+        return -1;
+    }
+
+    n = wrapped = 0;
+    for (;;) {
+        int cmp;
+        PyObject *item = PyIter_Next(it);
+        if (item == NULL) {
+            if (PyErr_Occurred())
+                goto Fail;
+            break;
+        }
+
+        cmp = PyObject_RichCompareBool(obj, item, Py_EQ);
+        Py_DECREF(item);
+        if (cmp < 0)
+            goto Fail;
+        if (cmp > 0) {
+            switch (operation) {
+            case PY_ITERSEARCH_COUNT:
+                if (n == PY_SSIZE_T_MAX) {
+                    PyErr_SetString(PyExc_OverflowError,
+                           "count exceeds C integer size");
+                    goto Fail;
+                }
+                ++n;
+                break;
+
+            case PY_ITERSEARCH_INDEX:
+                if (wrapped) {
+                    PyErr_SetString(PyExc_OverflowError,
+                           "index exceeds C integer size");
+                    goto Fail;
+                }
+                goto Done;
+
+            case PY_ITERSEARCH_CONTAINS:
+                n = 1;
+                goto Done;
+
+            default:
+                assert(!"unknown operation");
+            }
+        }
+
+        if (operation == PY_ITERSEARCH_INDEX) {
+            if (n == PY_SSIZE_T_MAX)
+                wrapped = 1;
+            ++n;
+        }
+    }
+
+    if (operation != PY_ITERSEARCH_INDEX)
+        goto Done;
+
+    PyErr_SetString(PyExc_ValueError,
+                    "sequence.index(x): x not in sequence");
+    /* fall into failure code */
+Fail:
+    n = -1;
+    /* fall through */
+Done:
+    Py_DECREF(it);
+    return n;
+
+}
+
+/* Return # of times o appears in s. */
+Py_ssize_t
+PySequence_Count(PyObject *s, PyObject *o)
+{
+    return _PySequence_IterSearch(s, o, PY_ITERSEARCH_COUNT);
+}
+
+/* Return -1 if error; 1 if ob in seq; 0 if ob not in seq.
+ * Use sq_contains if possible, else defer to _PySequence_IterSearch().
+ */
+int
+PySequence_Contains(PyObject *seq, PyObject *ob)
+{
+    Py_ssize_t result;
+    if (PyType_HasFeature(seq->ob_type, Py_TPFLAGS_HAVE_SEQUENCE_IN)) {
+        PySequenceMethods *sqm = seq->ob_type->tp_as_sequence;
+        if (sqm != NULL && sqm->sq_contains != NULL)
+            return (*sqm->sq_contains)(seq, ob);
+    }
+    result = _PySequence_IterSearch(seq, ob, PY_ITERSEARCH_CONTAINS);
+    return Py_SAFE_DOWNCAST(result, Py_ssize_t, int);
+}
+
+/* Backwards compatibility */
+#undef PySequence_In
+int
+PySequence_In(PyObject *w, PyObject *v)
+{
+    return PySequence_Contains(w, v);
+}
+
+Py_ssize_t
+PySequence_Index(PyObject *s, PyObject *o)
+{
+    return _PySequence_IterSearch(s, o, PY_ITERSEARCH_INDEX);
+}
+
+/* Operations on mappings */
+
+int
+PyMapping_Check(PyObject *o)
+{
+    if (o && PyInstance_Check(o))
+        return PyObject_HasAttrString(o, "__getitem__");
+
+    return  o && o->ob_type->tp_as_mapping &&
+        o->ob_type->tp_as_mapping->mp_subscript &&
+        !(o->ob_type->tp_as_sequence &&
+          o->ob_type->tp_as_sequence->sq_slice);
+}
+
+Py_ssize_t
+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("object of type '%.200s' has no len()", o);
+    return -1;
+}
+
+#undef PyMapping_Length
+Py_ssize_t
+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)
+{
+    return PyEval_CallObjectWithKeywords(o, a, NULL);
+}
+
+PyObject *
+PyObject_Call(PyObject *func, PyObject *arg, PyObject *kw)
+{
+    ternaryfunc call;
+
+    if ((call = func->ob_type->tp_call) != NULL) {
+        PyObject *result;
+        if (Py_EnterRecursiveCall(" while calling a Python object"))
+            return NULL;
+        result = (*call)(func, arg, kw);
+        Py_LeaveRecursiveCall();
+        if (result == NULL && !PyErr_Occurred())
+            PyErr_SetString(
+                PyExc_SystemError,
+                "NULL result without error in PyObject_Call");
+        return result;
+    }
+    PyErr_Format(PyExc_TypeError, "'%.200s' object is not callable",
+                 func->ob_type->tp_name);
+    return NULL;
+}
+
+static PyObject*
+call_function_tail(PyObject *callable, PyObject *args)
+{
+    PyObject *retval;
+
+    if (args == NULL)
+        return NULL;
+
+    if (!PyTuple_Check(args)) {
+        PyObject *a;
+
+        a = PyTuple_New(1);
+        if (a == NULL) {
+            Py_DECREF(args);
+            return NULL;
+        }
+        PyTuple_SET_ITEM(a, 0, args);
+        args = a;
+    }
+    retval = PyObject_Call(callable, args, NULL);
+
+    Py_DECREF(args);
+
+    return retval;
+}
+
+PyObject *
+PyObject_CallFunction(PyObject *callable, char *format, ...)
+{
+    va_list va;
+    PyObject *args;
+
+    if (callable == NULL)
+        return null_error();
+
+    if (format && *format) {
+        va_start(va, format);
+        args = Py_VaBuildValue(format, va);
+        va_end(va);
+    }
+    else
+        args = PyTuple_New(0);
+
+    return call_function_tail(callable, args);
+}
+
+PyObject *
+_PyObject_CallFunction_SizeT(PyObject *callable, char *format, ...)
+{
+    va_list va;
+    PyObject *args;
+
+    if (callable == NULL)
+        return null_error();
+
+    if (format && *format) {
+        va_start(va, format);
+        args = _Py_VaBuildValue_SizeT(format, va);
+        va_end(va);
+    }
+    else
+        args = PyTuple_New(0);
+
+    return call_function_tail(callable, args);
+}
+
+PyObject *
+PyObject_CallMethod(PyObject *o, char *name, char *format, ...)
+{
+    va_list va;
+    PyObject *args;
+    PyObject *func = NULL;
+    PyObject *retval = NULL;
+
+    if (o == NULL || name == NULL)
+        return null_error();
+
+    func = PyObject_GetAttrString(o, name);
+    if (func == NULL) {
+        PyErr_SetString(PyExc_AttributeError, name);
+        return 0;
+    }
+
+    if (!PyCallable_Check(func)) {
+        type_error("attribute of type '%.200s' is not callable", func);
+        goto exit;
+    }
+
+    if (format && *format) {
+        va_start(va, format);
+        args = Py_VaBuildValue(format, va);
+        va_end(va);
+    }
+    else
+        args = PyTuple_New(0);
+
+    retval = call_function_tail(func, args);
+
+  exit:
+    /* args gets consumed in call_function_tail */
+    Py_XDECREF(func);
+
+    return retval;
+}
+
+PyObject *
+_PyObject_CallMethod_SizeT(PyObject *o, char *name, char *format, ...)
+{
+    va_list va;
+    PyObject *args;
+    PyObject *func = NULL;
+    PyObject *retval = NULL;
+
+    if (o == NULL || name == NULL)
+        return null_error();
+
+    func = PyObject_GetAttrString(o, name);
+    if (func == NULL) {
+        PyErr_SetString(PyExc_AttributeError, name);
+        return 0;
+    }
+
+    if (!PyCallable_Check(func)) {
+        type_error("attribute of type '%.200s' is not callable", func);
+        goto exit;
+    }
+
+    if (format && *format) {
+        va_start(va, format);
+        args = _Py_VaBuildValue_SizeT(format, va);
+        va_end(va);
+    }
+    else
+        args = PyTuple_New(0);
+
+    retval = call_function_tail(func, args);
+
+  exit:
+    /* args gets consumed in call_function_tail */
+    Py_XDECREF(func);
+
+    return retval;
+}
+
+
+static PyObject *
+objargs_mktuple(va_list va)
+{
+    int i, n = 0;
+    va_list countva;
+    PyObject *result, *tmp;
+
+#ifdef VA_LIST_IS_ARRAY
+    memcpy(countva, va, sizeof(va_list));
+#else
+#ifdef __va_copy
+    __va_copy(countva, va);
+#else
+    countva = va;
+#endif
+#endif
+
+    while (((PyObject *)va_arg(countva, PyObject *)) != NULL)
+        ++n;
+    result = PyTuple_New(n);
+    if (result != NULL && n > 0) {
+        for (i = 0; i < n; ++i) {
+            tmp = (PyObject *)va_arg(va, PyObject *);
+            PyTuple_SET_ITEM(result, i, tmp);
+            Py_INCREF(tmp);
+        }
+    }
+    return result;
+}
+
+PyObject *
+PyObject_CallMethodObjArgs(PyObject *callable, PyObject *name, ...)
+{
+    PyObject *args, *tmp;
+    va_list vargs;
+
+    if (callable == NULL || name == NULL)
+        return null_error();
+
+    callable = PyObject_GetAttr(callable, name);
+    if (callable == NULL)
+        return NULL;
+
+    /* count the args */
+    va_start(vargs, name);
+    args = objargs_mktuple(vargs);
+    va_end(vargs);
+    if (args == NULL) {
+        Py_DECREF(callable);
+        return NULL;
+    }
+    tmp = PyObject_Call(callable, args, NULL);
+    Py_DECREF(args);
+    Py_DECREF(callable);
+
+    return tmp;
+}
+
+PyObject *
+PyObject_CallFunctionObjArgs(PyObject *callable, ...)
+{
+    PyObject *args, *tmp;
+    va_list vargs;
+
+    if (callable == NULL)
+        return null_error();
+
+    /* count the args */
+    va_start(vargs, callable);
+    args = objargs_mktuple(vargs);
+    va_end(vargs);
+    if (args == NULL)
+        return NULL;
+    tmp = PyObject_Call(callable, args, NULL);
+    Py_DECREF(args);
+
+    return tmp;
+}
+
+
+/* isinstance(), issubclass() */
+
+/* abstract_get_bases() has logically 4 return states, with a sort of 0th
+ * state that will almost never happen.
+ *
+ * 0. creating the __bases__ static string could get a MemoryError
+ * 1. getattr(cls, '__bases__') could raise an AttributeError
+ * 2. getattr(cls, '__bases__') could raise some other exception
+ * 3. getattr(cls, '__bases__') could return a tuple
+ * 4. getattr(cls, '__bases__') could return something other than a tuple
+ *
+ * Only state #3 is a non-error state and only it returns a non-NULL object
+ * (it returns the retrieved tuple).
+ *
+ * Any raised AttributeErrors are masked by clearing the exception and
+ * returning NULL.  If an object other than a tuple comes out of __bases__,
+ * then again, the return value is NULL.  So yes, these two situations
+ * produce exactly the same results: NULL is returned and no error is set.
+ *
+ * If some exception other than AttributeError is raised, then NULL is also
+ * returned, but the exception is not cleared.  That's because we want the
+ * exception to be propagated along.
+ *
+ * Callers are expected to test for PyErr_Occurred() when the return value
+ * is NULL to decide whether a valid exception should be propagated or not.
+ * When there's no exception to propagate, it's customary for the caller to
+ * set a TypeError.
+ */
+static PyObject *
+abstract_get_bases(PyObject *cls)
+{
+    static PyObject *__bases__ = NULL;
+    PyObject *bases;
+
+    if (__bases__ == NULL) {
+        __bases__ = PyString_InternFromString("__bases__");
+        if (__bases__ == NULL)
+            return NULL;
+    }
+    bases = PyObject_GetAttr(cls, __bases__);
+    if (bases == NULL) {
+        if (PyErr_ExceptionMatches(PyExc_AttributeError))
+            PyErr_Clear();
+        return NULL;
+    }
+    if (!PyTuple_Check(bases)) {
+        Py_DECREF(bases);
+        return NULL;
+    }
+    return bases;
+}
+
+
+static int
+abstract_issubclass(PyObject *derived, PyObject *cls)
+{
+    PyObject *bases = NULL;
+    Py_ssize_t i, n;
+    int r = 0;
+
+    while (1) {
+        if (derived == cls)
+            return 1;
+        bases = abstract_get_bases(derived);
+        if (bases == NULL) {
+            if (PyErr_Occurred())
+                return -1;
+            return 0;
+        }
+        n = PyTuple_GET_SIZE(bases);
+        if (n == 0) {
+            Py_DECREF(bases);
+            return 0;
+        }
+        /* Avoid recursivity in the single inheritance case */
+        if (n == 1) {
+            derived = PyTuple_GET_ITEM(bases, 0);
+            Py_DECREF(bases);
+            continue;
+        }
+        for (i = 0; i < n; i++) {
+            r = abstract_issubclass(PyTuple_GET_ITEM(bases, i), cls);
+            if (r != 0)
+                break;
+        }
+        Py_DECREF(bases);
+        return r;
+    }
+}
+
+static int
+check_class(PyObject *cls, const char *error)
+{
+    PyObject *bases = abstract_get_bases(cls);
+    if (bases == NULL) {
+        /* Do not mask errors. */
+        if (!PyErr_Occurred())
+            PyErr_SetString(PyExc_TypeError, error);
+        return 0;
+    }
+    Py_DECREF(bases);
+    return -1;
+}
+
+static int
+recursive_isinstance(PyObject *inst, PyObject *cls)
+{
+    PyObject *icls;
+    static PyObject *__class__ = NULL;
+    int retval = 0;
+
+    if (__class__ == NULL) {
+        __class__ = PyString_InternFromString("__class__");
+        if (__class__ == NULL)
+            return -1;
+    }
+
+    if (PyClass_Check(cls) && PyInstance_Check(inst)) {
+        PyObject *inclass =
+            (PyObject*)((PyInstanceObject*)inst)->in_class;
+        retval = PyClass_IsSubclass(inclass, cls);
+    }
+    else if (PyType_Check(cls)) {
+        retval = PyObject_TypeCheck(inst, (PyTypeObject *)cls);
+        if (retval == 0) {
+            PyObject *c = PyObject_GetAttr(inst, __class__);
+            if (c == NULL) {
+                PyErr_Clear();
+            }
+            else {
+                if (c != (PyObject *)(inst->ob_type) &&
+                    PyType_Check(c))
+                    retval = PyType_IsSubtype(
+                        (PyTypeObject *)c,
+                        (PyTypeObject *)cls);
+                Py_DECREF(c);
+            }
+        }
+    }
+    else {
+        if (!check_class(cls,
+            "isinstance() arg 2 must be a class, type,"
+            " or tuple of classes and types"))
+            return -1;
+        icls = PyObject_GetAttr(inst, __class__);
+        if (icls == NULL) {
+            PyErr_Clear();
+            retval = 0;
+        }
+        else {
+            retval = abstract_issubclass(icls, cls);
+            Py_DECREF(icls);
+        }
+    }
+
+    return retval;
+}
+
+int
+PyObject_IsInstance(PyObject *inst, PyObject *cls)
+{
+    static PyObject *name = NULL;
+
+    /* Quick test for an exact match */
+    if (Py_TYPE(inst) == (PyTypeObject *)cls)
+        return 1;
+
+    if (PyTuple_Check(cls)) {
+        Py_ssize_t i;
+        Py_ssize_t n;
+        int r = 0;
+
+        if (Py_EnterRecursiveCall(" in __instancecheck__"))
+            return -1;
+        n = PyTuple_GET_SIZE(cls);
+        for (i = 0; i < n; ++i) {
+            PyObject *item = PyTuple_GET_ITEM(cls, i);
+            r = PyObject_IsInstance(inst, item);
+            if (r != 0)
+                /* either found it, or got an error */
+                break;
+        }
+        Py_LeaveRecursiveCall();
+        return r;
+    }
+
+    if (!(PyClass_Check(cls) || PyInstance_Check(cls))) {
+        PyObject *checker;
+        checker = _PyObject_LookupSpecial(cls, "__instancecheck__", &name);
+        if (checker != NULL) {
+            PyObject *res;
+            int ok = -1;
+            if (Py_EnterRecursiveCall(" in __instancecheck__")) {
+                Py_DECREF(checker);
+                return ok;
+            }
+            res = PyObject_CallFunctionObjArgs(checker, inst, NULL);
+            Py_LeaveRecursiveCall();
+            Py_DECREF(checker);
+            if (res != NULL) {
+                ok = PyObject_IsTrue(res);
+                Py_DECREF(res);
+            }
+            return ok;
+        }
+        else if (PyErr_Occurred())
+            return -1;
+    }
+    return recursive_isinstance(inst, cls);
+}
+
+static  int
+recursive_issubclass(PyObject *derived, PyObject *cls)
+{
+    int retval;
+
+    if (PyType_Check(cls) && PyType_Check(derived)) {
+        /* Fast path (non-recursive) */
+        return PyType_IsSubtype(
+            (PyTypeObject *)derived, (PyTypeObject *)cls);
+    }
+    if (!PyClass_Check(derived) || !PyClass_Check(cls)) {
+        if (!check_class(derived,
+                         "issubclass() arg 1 must be a class"))
+            return -1;
+
+        if (!check_class(cls,
+                        "issubclass() arg 2 must be a class"
+                        " or tuple of classes"))
+            return -1;
+        retval = abstract_issubclass(derived, cls);
+    }
+    else {
+        /* shortcut */
+        if (!(retval = (derived == cls)))
+            retval = PyClass_IsSubclass(derived, cls);
+    }
+
+    return retval;
+}
+
+int
+PyObject_IsSubclass(PyObject *derived, PyObject *cls)
+{
+    static PyObject *name = NULL;
+
+    if (PyTuple_Check(cls)) {
+        Py_ssize_t i;
+        Py_ssize_t n;
+        int r = 0;
+
+        if (Py_EnterRecursiveCall(" in __subclasscheck__"))
+            return -1;
+        n = PyTuple_GET_SIZE(cls);
+        for (i = 0; i < n; ++i) {
+            PyObject *item = PyTuple_GET_ITEM(cls, i);
+            r = PyObject_IsSubclass(derived, item);
+            if (r != 0)
+                /* either found it, or got an error */
+                break;
+        }
+        Py_LeaveRecursiveCall();
+        return r;
+    }
+    if (!(PyClass_Check(cls) || PyInstance_Check(cls))) {
+        PyObject *checker;
+        checker = _PyObject_LookupSpecial(cls, "__subclasscheck__", &name);
+        if (checker != NULL) {
+            PyObject *res;
+            int ok = -1;
+            if (Py_EnterRecursiveCall(" in __subclasscheck__")) {
+                Py_DECREF(checker);
+                return ok;
+            }
+            res = PyObject_CallFunctionObjArgs(checker, derived, NULL);
+            Py_LeaveRecursiveCall();
+            Py_DECREF(checker);
+            if (res != NULL) {
+                ok = PyObject_IsTrue(res);
+                Py_DECREF(res);
+            }
+            return ok;
+        }
+        else if (PyErr_Occurred()) {
+            return -1;
+        }
+    }
+    return recursive_issubclass(derived, cls);
+}
+
+int
+_PyObject_RealIsInstance(PyObject *inst, PyObject *cls)
+{
+    return recursive_isinstance(inst, cls);
+}
+
+int
+_PyObject_RealIsSubclass(PyObject *derived, PyObject *cls)
+{
+    return recursive_issubclass(derived, cls);
+}
+
+
+PyObject *
+PyObject_GetIter(PyObject *o)
+{
+    PyTypeObject *t = o->ob_type;
+    getiterfunc f = NULL;
+    if (PyType_HasFeature(t, Py_TPFLAGS_HAVE_ITER))
+        f = t->tp_iter;
+    if (f == NULL) {
+        if (PySequence_Check(o))
+            return PySeqIter_New(o);
+        return type_error("'%.200s' object is not iterable", o);
+    }
+    else {
+        PyObject *res = (*f)(o);
+        if (res != NULL && !PyIter_Check(res)) {
+            PyErr_Format(PyExc_TypeError,
+                         "iter() returned non-iterator "
+                         "of type '%.100s'",
+                         res->ob_type->tp_name);
+            Py_DECREF(res);
+            res = NULL;
+        }
+        return res;
+    }
+}
+
+/* Return next item.
+ * If an error occurs, return NULL.  PyErr_Occurred() will be true.
+ * If the iteration terminates normally, return NULL and clear the
+ * PyExc_StopIteration exception (if it was set).  PyErr_Occurred()
+ * will be false.
+ * Else return the next object.  PyErr_Occurred() will be false.
+ */
+PyObject *
+PyIter_Next(PyObject *iter)
+{
+    PyObject *result;
+    result = (*iter->ob_type->tp_iternext)(iter);
+    if (result == NULL &&
+        PyErr_Occurred() &&
+        PyErr_ExceptionMatches(PyExc_StopIteration))
+        PyErr_Clear();
+    return result;
+}

from_cpython/Objects/sliceobject.c

+/*
+Written by Jim Hugunin and Chris Chase.
+
+This includes both the singular ellipsis object and slice objects.
+
+Guido, feel free to do whatever you want in the way of copyrights
+for this file.
+*/
+
+/*
+Py_Ellipsis encodes the '...' rubber index token. It is similar to
+the Py_NoneStruct in that there is no way to create other objects of
+this type and there is exactly one in existence.
+*/
+
+#include "Python.h"
+#include "structmember.h"
+
+static PyObject *
+ellipsis_repr(PyObject *op)
+{
+    return PyString_FromString("Ellipsis");
+}
+
+PyTypeObject PyEllipsis_Type = {
+    PyVarObject_HEAD_INIT(&PyType_Type, 0)
+    "ellipsis",                         /* tp_name */
+    0,                                  /* tp_basicsize */
+    0,                                  /* tp_itemsize */
+    0, /*never called*/                 /* tp_dealloc */
+    0,                                  /* tp_print */
+    0,                                  /* tp_getattr */
+    0,                                  /* tp_setattr */
+    0,                                  /* tp_compare */
+    ellipsis_repr,                      /* tp_repr */
+    0,                                  /* tp_as_number */
+    0,                                  /* tp_as_sequence */
+    0,                                  /* tp_as_mapping */
+    0,                                  /* tp_hash */
+    0,                                  /* tp_call */
+    0,                                  /* tp_str */
+    PyObject_GenericGetAttr,            /* tp_getattro */
+    0,                                  /* tp_setattro */
+    0,                                  /* tp_as_buffer */
+    Py_TPFLAGS_DEFAULT,                 /* tp_flags */
+};
+
+PyObject _Py_EllipsisObject = {
+    _PyObject_EXTRA_INIT
+    1, &PyEllipsis_Type
+};
+
+
+/* Slice object implementation
+
+   start, stop, and step are python objects with None indicating no
+   index is present.
+*/
+
+PyObject *
+PySlice_New(PyObject *start, PyObject *stop, PyObject *step)
+{
+    PySliceObject *obj = PyObject_New(PySliceObject, &PySlice_Type);
+
+    if (obj == NULL)
+        return NULL;
+
+    if (step == NULL) step = Py_None;
+    Py_INCREF(step);
+    if (start == NULL) start = Py_None;
+    Py_INCREF(start);
+    if (stop == NULL) stop = Py_None;
+    Py_INCREF(stop);
+
+    obj->step = step;
+    obj->start = start;
+    obj->stop = stop;
+
+    return (PyObject *) obj;
+}
+
+PyObject *
+_PySlice_FromIndices(Py_ssize_t istart, Py_ssize_t istop)
+{
+    PyObject *start, *end, *slice;
+    start = PyInt_FromSsize_t(istart);
+    if (!start)
+        return NULL;
+    end = PyInt_FromSsize_t(istop);
+    if (!end) {
+        Py_DECREF(start);
+        return NULL;
+    }
+
+    slice = PySlice_New(start, end, NULL);
+    Py_DECREF(start);
+    Py_DECREF(end);
+    return slice;
+}
+
+int
+PySlice_GetIndices(PySliceObject *r, Py_ssize_t length,
+                   Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step)
+{
+    /* XXX support long ints */
+    if (r->step == Py_None) {
+        *step = 1;
+    } else {
+        if (!PyInt_Check(r->step) && !PyLong_Check(r->step)) return -1;
+        *step = PyInt_AsSsize_t(r->step);
+    }
+    if (r->start == Py_None) {
+        *start = *step < 0 ? length-1 : 0;
+    } else {
+        if (!PyInt_Check(r->start) && !PyLong_Check(r->step)) return -1;
+        *start = PyInt_AsSsize_t(r->start);
+        if (*start < 0) *start += length;
+    }
+    if (r->stop == Py_None) {
+        *stop = *step < 0 ? -1 : length;
+    } else {
+        if (!PyInt_Check(r->stop) && !PyLong_Check(r->step)) return -1;
+        *stop = PyInt_AsSsize_t(r->stop);
+        if (*stop < 0) *stop += length;
+    }
+    if (*stop > length) return -1;
+    if (*start >= length) return -1;
+    if (*step == 0) return -1;
+    return 0;
+}
+
+int
+PySlice_GetIndicesEx(PySliceObject *r, Py_ssize_t length,
+                     Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step, Py_ssize_t *slicelength)
+{
+    /* this is harder to get right than you might think */
+
+    Py_ssize_t defstart, defstop;
+
+    if (r->step == Py_None) {
+        *step = 1;
+    }
+    else {
+        if (!_PyEval_SliceIndex(r->step, step)) return -1;
+        if (*step == 0) {
+            PyErr_SetString(PyExc_ValueError,
+                            "slice step cannot be zero");
+            return -1;
+        }
+    }
+
+    defstart = *step < 0 ? length-1 : 0;
+    defstop = *step < 0 ? -1 : length;
+
+    if (r->start == Py_None) {
+        *start = defstart;
+    }
+    else {
+        if (!_PyEval_SliceIndex(r->start, start)) return -1;
+        if (*start < 0) *start += length;
+        if (*start < 0) *start = (*step < 0) ? -1 : 0;
+        if (*start >= length)
+            *start = (*step < 0) ? length - 1 : length;
+    }
+
+    if (r->stop == Py_None) {
+        *stop = defstop;
+    }
+    else {
+        if (!_PyEval_SliceIndex(r->stop, stop)) return -1;
+        if (*stop < 0) *stop += length;
+        if (*stop < 0) *stop = (*step < 0) ? -1 : 0;
+        if (*stop >= length)
+            *stop = (*step < 0) ? length - 1 : length;
+    }
+
+    if ((*step < 0 && *stop >= *start)
+        || (*step > 0 && *start >= *stop)) {
+        *slicelength = 0;
+    }
+    else if (*step < 0) {
+        *slicelength = (*stop-*start+1)/(*step)+1;
+    }
+    else {
+        *slicelength = (*stop-*start-1)/(*step)+1;
+    }
+
+    return 0;
+}
+
+static PyObject *
+slice_new(PyTypeObject *type, PyObject *args, PyObject *kw)
+{
+    PyObject *start, *stop, *step;
+
+    start = stop = step = NULL;
+
+    if (!_PyArg_NoKeywords("slice()", kw))
+        return NULL;
+
+    if (!PyArg_UnpackTuple(args, "slice", 1, 3, &start, &stop, &step))
+        return NULL;
+
+    /* This swapping of stop and start is to maintain similarity with
+       range(). */
+    if (stop == NULL) {
+        stop = start;
+        start = NULL;
+    }
+    return PySlice_New(start, stop, step);
+}
+
+PyDoc_STRVAR(slice_doc,
+"slice(stop)\n\
+slice(start, stop[, step])\n\
+\n\
+Create a slice object.  This is used for extended slicing (e.g. a[0:10:2]).");
+
+static void
+slice_dealloc(PySliceObject *r)
+{
+    Py_DECREF(r->step);
+    Py_DECREF(r->start);
+    Py_DECREF(r->stop);
+    PyObject_Del(r);
+}
+
+static PyObject *
+slice_repr(PySliceObject *r)
+{
+    PyObject *s, *comma;
+
+    s = PyString_FromString("slice(");
+    comma = PyString_FromString(", ");
+    PyString_ConcatAndDel(&s, PyObject_Repr(r->start));
+    PyString_Concat(&s, comma);
+    PyString_ConcatAndDel(&s, PyObject_Repr(r->stop));
+    PyString_Concat(&s, comma);
+    PyString_ConcatAndDel(&s, PyObject_Repr(r->step));
+    PyString_ConcatAndDel(&s, PyString_FromString(")"));
+    Py_DECREF(comma);
+    return s;
+}
+
+static PyMemberDef slice_members[] = {
+    {"start", T_OBJECT, offsetof(PySliceObject, start), READONLY},
+    {"stop", T_OBJECT, offsetof(PySliceObject, stop), READONLY},
+    {"step", T_OBJECT, offsetof(PySliceObject, step), READONLY},
+    {0}
+};
+
+static PyObject*
+slice_indices(PySliceObject* self, PyObject* len)
+{
+    Py_ssize_t ilen, start, stop, step, slicelength;
+
+    ilen = PyNumber_AsSsize_t(len, PyExc_OverflowError);
+
+    if (ilen == -1 && PyErr_Occurred()) {
+        return NULL;
+    }
+
+    if (PySlice_GetIndicesEx(self, ilen, &start, &stop,
+                             &step, &slicelength) < 0) {
+        return NULL;
+    }
+
+    return Py_BuildValue("(nnn)", start, stop, step);
+}
+
+PyDoc_STRVAR(slice_indices_doc,
+"S.indices(len) -> (start, stop, stride)\n\
+\n\
+Assuming a sequence of length len, calculate the start and stop\n\
+indices, and the stride length of the extended slice described by\n\
+S. Out of bounds indices are clipped in a manner consistent with the\n\
+handling of normal slices.");
+
+static PyObject *
+slice_reduce(PySliceObject* self)
+{
+    return Py_BuildValue("O(OOO)", Py_TYPE(self), self->start, self->stop, self->step);
+}
+
+PyDoc_STRVAR(reduce_doc, "Return state information for pickling.");
+
+static PyMethodDef slice_methods[] = {
+    {"indices",         (PyCFunction)slice_indices,
+     METH_O,            slice_indices_doc},
+    {"__reduce__",      (PyCFunction)slice_reduce,
+     METH_NOARGS,       reduce_doc},
+    {NULL, NULL}
+};
+
+static int
+slice_compare(PySliceObject *v, PySliceObject *w)
+{
+    int result = 0;
+
+    if (v == w)
+        return 0;
+
+    if (PyObject_Cmp(v->start, w->start, &result) < 0)
+        return -2;
+    if (result != 0)
+        return result;
+    if (PyObject_Cmp(v->stop, w->stop, &result) < 0)
+        return -2;
+    if (result != 0)
+        return result;
+    if (PyObject_Cmp(v->step, w->step, &result) < 0)
+        return -2;
+    return result;
+}
+
+static long
+slice_hash(PySliceObject *v)
+{
+    PyErr_SetString(PyExc_TypeError, "unhashable type");
+    return -1L;
+}
+
+PyTypeObject PySlice_Type = {
+    PyVarObject_HEAD_INIT(&PyType_Type, 0)
+    "slice",                    /* Name of this type */
+    sizeof(PySliceObject),      /* Basic object size */
+    0,                          /* Item size for varobject */
+    (destructor)slice_dealloc,                  /* tp_dealloc */
+    0,                                          /* tp_print */
+    0,                                          /* tp_getattr */
+    0,                                          /* tp_setattr */
+    (cmpfunc)slice_compare,                     /* tp_compare */
+    (reprfunc)slice_repr,                       /* tp_repr */
+    0,                                          /* tp_as_number */
+    0,                                          /* tp_as_sequence */
+    0,                                          /* tp_as_mapping */
+    (hashfunc)slice_hash,                       /* tp_hash */
+    0,                                          /* tp_call */
+    0,                                          /* tp_str */
+    PyObject_GenericGetAttr,                    /* tp_getattro */
+    0,                                          /* tp_setattro */
+    0,                                          /* tp_as_buffer */
+    Py_TPFLAGS_DEFAULT,                         /* tp_flags */
+    slice_doc,                                  /* tp_doc */
+    0,                                          /* tp_traverse */
+    0,                                          /* tp_clear */
+    0,                                          /* tp_richcompare */
+    0,                                          /* tp_weaklistoffset */
+    0,                                          /* tp_iter */
+    0,                                          /* tp_iternext */
+    slice_methods,                              /* tp_methods */
+    slice_members,                              /* 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 */
+    slice_new,                                  /* tp_new */
+};