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"



/* 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 */

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

int
_PyObject_HasLen(PyObject *o) {
    return (Py_TYPE(o)->tp_as_sequence && Py_TYPE(o)->tp_as_sequence->sq_length) ||
        (Py_TYPE(o)->tp_as_mapping && Py_TYPE(o)->tp_as_mapping->mp_length);
}

/* The length hint function returns a non-negative value from o.__len__()
   or o.__length_hint__(). If those methods aren't found the defaultvalue is
   returned.  If one of the calls fails with an exception other than TypeError
   this function returns -1.
*/

Py_ssize_t
PyObject_LengthHint(PyObject *o, Py_ssize_t defaultvalue)
{
    PyObject *hint, *result;
    Py_ssize_t res;
    _Py_IDENTIFIER(__length_hint__);
    if (_PyObject_HasLen(o)) {
        res = PyObject_Length(o);
        if (res < 0 && PyErr_Occurred()) {
            if (!PyErr_ExceptionMatches(PyExc_TypeError)) {
                return -1;
            }
            PyErr_Clear();
        }
        else {
            return res;
        }
    }
    hint = _PyObject_LookupSpecial(o, &PyId___length_hint__);
    if (hint == NULL) {
        if (PyErr_Occurred()) {
            return -1;
        }
        return defaultvalue;
    }
    result = PyObject_CallFunctionObjArgs(hint, NULL);
    Py_DECREF(hint);
    if (result == NULL) {
        if (PyErr_ExceptionMatches(PyExc_TypeError)) {
            PyErr_Clear();
            return defaultvalue;
        }
        return -1;
    }
    else if (result == Py_NotImplemented) {
        Py_DECREF(result);
        return defaultvalue;
    }
    if (!PyLong_Check(result)) {
        PyErr_Format(PyExc_TypeError, "__length_hint__ must be an integer, not %.100s",
            Py_TYPE(result)->tp_name);
        Py_DECREF(result);
        return -1;
    }
    res = PyLong_AsSsize_t(result);
    Py_DECREF(result);
    if (res < 0 && PyErr_Occurred()) {
        return -1;
    }
    if (res < 0) {
        PyErr_Format(PyExc_ValueError, "__length_hint__() should return >= 0");
        return -1;
    }
    return res;
}

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 is not subscriptable", 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, const char *key)
{
    PyObject *okey;
    int ret;

    if (o == NULL || key == NULL) {
        null_error();
        return -1;
    }
    okey = PyUnicode_FromString(key);
    if (okey == NULL)
        return -1;
    ret = PyObject_DelItem(o, okey);
    Py_DECREF(okey);
    return ret;
}

/* We release the buffer right after use of this function which could
   cause issues later on.  Don't use these functions in new code.
 */
int
PyObject_AsCharBuffer(PyObject *obj,
                      const char **buffer,
                      Py_ssize_t *buffer_len)
{
    return PyObject_AsReadBuffer(obj, (const void **)buffer, buffer_len);
}

int
PyObject_CheckReadBuffer(PyObject *obj)
{
    PyBufferProcs *pb = obj->ob_type->tp_as_buffer;
    Py_buffer view;

    if (pb == NULL ||
        pb->bf_getbuffer == NULL)
        return 0;
    if ((*pb->bf_getbuffer)(obj, &view, PyBUF_SIMPLE) == -1) {
        PyErr_Clear();
        return 0;
    }
    PyBuffer_Release(&view);
    return 1;
}

int PyObject_AsReadBuffer(PyObject *obj,
                          const void **buffer,
                          Py_ssize_t *buffer_len)
{
    Py_buffer view;

    if (obj == NULL || buffer == NULL || buffer_len == NULL) {
        null_error();
        return -1;
    }
    if (PyObject_GetBuffer(obj, &view, PyBUF_SIMPLE) != 0)
        return -1;

    *buffer = view.buf;
    *buffer_len = view.len;
    PyBuffer_Release(&view);
    return 0;
}

int PyObject_AsWriteBuffer(PyObject *obj,
                           void **buffer,
                           Py_ssize_t *buffer_len)
{
    PyBufferProcs *pb;
    Py_buffer view;

    if (obj == NULL || buffer == NULL || buffer_len == NULL) {
        null_error();
        return -1;
    }
    pb = obj->ob_type->tp_as_buffer;
    if (pb == NULL ||
        pb->bf_getbuffer == NULL ||
        ((*pb->bf_getbuffer)(obj, &view, PyBUF_WRITABLE) != 0)) {
        PyErr_SetString(PyExc_TypeError,
                        "expected a writable bytes-like object");
        return -1;
    }

    *buffer = view.buf;
    *buffer_len = view.len;
    PyBuffer_Release(&view);
    return 0;
}

/* Buffer C-API for Python 3.0 */

int
PyObject_GetBuffer(PyObject *obj, Py_buffer *view, int flags)
{
    PyBufferProcs *pb = obj->ob_type->tp_as_buffer;

    if (pb == NULL || pb->bf_getbuffer == NULL) {
        PyErr_Format(PyExc_TypeError,
                     "a bytes-like object is required, not '%.100s'",
                     Py_TYPE(obj)->tp_name);
        return -1;
    }
    return (*pb->bf_getbuffer)(obj, view, flags);
}

static int
_IsFortranContiguous(const Py_buffer *view)
{
    Py_ssize_t sd, dim;
    int i;

    /* 1) len = product(shape) * itemsize
       2) itemsize > 0
       3) len = 0 <==> exists i: shape[i] = 0 */
    if (view->len == 0) return 1;
    if (view->strides == NULL) {  /* C-contiguous by definition */
        /* Trivially F-contiguous */
        if (view->ndim <= 1) return 1;

        /* ndim > 1 implies shape != NULL */
        assert(view->shape != NULL);

        /* Effectively 1-d */
        sd = 0;
        for (i=0; i<view->ndim; i++) {
            if (view->shape[i] > 1) sd += 1;
        }
        return sd <= 1;
    }

    /* strides != NULL implies both of these */
    assert(view->ndim > 0);
    assert(view->shape != NULL);

    sd = view->itemsize;
    for (i=0; i<view->ndim; i++) {
        dim = view->shape[i];
        if (dim > 1 && view->strides[i] != sd) {
            return 0;
        }
        sd *= dim;
    }
    return 1;
}

static int
_IsCContiguous(const Py_buffer *view)
{
    Py_ssize_t sd, dim;
    int i;

    /* 1) len = product(shape) * itemsize
       2) itemsize > 0
       3) len = 0 <==> exists i: shape[i] = 0 */
    if (view->len == 0) return 1;
    if (view->strides == NULL) return 1; /* C-contiguous by definition */

    /* strides != NULL implies both of these */
    assert(view->ndim > 0);
    assert(view->shape != NULL);

    sd = view->itemsize;
    for (i=view->ndim-1; i>=0; i--) {
        dim = view->shape[i];
        if (dim > 1 && view->strides[i] != sd) {
            return 0;
        }
        sd *= dim;
    }
    return 1;
}

int
PyBuffer_IsContiguous(const Py_buffer *view, char order)
{

    if (view->suboffsets != NULL) return 0;

    if (order == 'C')
        return _IsCContiguous(view);
    else if (order == 'F')
        return _IsFortranContiguous(view);
    else if (order == '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;
        }
    }
}

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 */

    /* view->ndim <= 64 */
    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--) {
        ptr = PyBuffer_GetPointer(view, indices);
        memcpy(ptr, src, view->itemsize);
        src += view->itemsize;
        addone(view->ndim, indices, view->shape);
    }

    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 be "\
                        "bytes-like objects");
        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) {
        PyErr_SetString(PyExc_BufferError,
            "PyBuffer_FillInfo: view==NULL argument is obsolete");
        return -1;
    }

    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;
    PyBufferProcs *pb;
    if (obj == NULL)
        return;
    pb = Py_TYPE(obj)->tp_as_buffer;
    if (pb && pb->bf_releasebuffer)
        pb->bf_releasebuffer(obj, view);
    view->obj = NULL;
    Py_DECREF(obj);
}

PyObject *
PyObject_Format(PyObject *obj, PyObject *format_spec)
{
    PyObject *meth;
    PyObject *empty = NULL;
    PyObject *result = NULL;
    _Py_IDENTIFIER(__format__);

    /* If no format_spec is provided, use an empty string */
    if (format_spec == NULL) {
        empty = PyUnicode_New(0, 0);
        format_spec = empty;
    }

    /* Find the (unbound!) __format__ method (a borrowed reference) */
    meth = _PyObject_LookupSpecial(obj, &PyId___format__);
    if (meth == 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(meth, format_spec, NULL);
    Py_DECREF(meth);

    if (result && !PyUnicode_Check(result)) {
        PyErr_Format(PyExc_TypeError,
             "__format__ must return a str, not %.200s",
             Py_TYPE(result)->tp_name);
        Py_DECREF(result);
        result = NULL;
        goto done;
    }

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 */

#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:

  Order operations are tried until either a valid result or error:
    w.op(v,w)[*], v.op(v,w), w.op(v,w)

  [*] only when v->ob_type != w->ob_type && w->ob_type is a subclass of
      v->ob_type
 */

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)
        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) {
        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 */
    }
    Py_RETURN_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:

  Order operations are tried until either a valid result or error:
    v.op(v,w,z), w.op(v,w,z), z.op(v,w,z)
 */

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)
        slotv = NB_TERNOP(mv, op_slot);
    if (w->ob_type != v->ob_type &&
        mw != NULL) {
        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) {
        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 (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_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_MatrixMultiply(PyObject *v, PyObject *w)
{
    return binary_op(v, w, NB_SLOT(nb_matrix_multiply), "@");
}

PyObject *
PyNumber_FloorDivide(PyObject *v, PyObject *w)
{
    return binary_op(v, w, NB_SLOT(nb_floor_divide), "//");
}

PyObject *
PyNumber_TrueDivide(PyObject *v, PyObject *w)
{
    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.

   */

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) {
        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_InMatrixMultiply, nb_inplace_matrix_multiply, nb_matrix_multiply, "@=")

PyObject *
PyNumber_InPlaceFloorDivide(PyObject *v, PyObject *w)
{
    return binary_iop(v, w, NB_SLOT(nb_inplace_floor_divide),
                      NB_SLOT(nb_floor_divide), "//=");
}

PyObject *
PyNumber_InPlaceTrueDivide(PyObject *v, PyObject *w)
{
    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;
            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) {
            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_InPlaceMatrixMultiply(PyObject *v, PyObject *w)
{
    return binary_iop(v, w, NB_SLOT(nb_inplace_matrix_multiply),
                      NB_SLOT(nb_matrix_multiply), "@=");
}

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 (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);
}

/* Return a Python int from the object item.
   Raise TypeError if the result is not an int
   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 (PyLong_Check(item)) {
        Py_INCREF(item);
        return item;
    }
    if (!PyIndex_Check(item)) {
        PyErr_Format(PyExc_TypeError,
                     "'%.200s' object cannot be interpreted "
                     "as an integer", item->ob_type->tp_name);
        return NULL;
    }
    result = item->ob_type->tp_as_number->nb_index(item);
    if (!result || PyLong_CheckExact(result))
        return result;
    if (!PyLong_Check(result)) {
        PyErr_Format(PyExc_TypeError,
                     "__index__ returned non-int (type %.200s)",
                     result->ob_type->tp_name);
        Py_DECREF(result);
        return NULL;
    }
    /* Issue #17576: warn if 'result' not of exact type int. */
    if (PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
            "__index__ returned non-int (type %.200s).  "
            "The ability to return an instance of a strict subclass of int "
            "is deprecated, and may be removed in a future version of Python.",
            result->ob_type->tp_name)) {
        Py_DECREF(result);
        return NULL;
    }
    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 PyLong_AsSsize_t() returns without error. */
    result = PyLong_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_Long(PyObject *o)
{
    PyNumberMethods *m;
    PyObject *trunc_func;
    Py_buffer view;
    _Py_IDENTIFIER(__trunc__);

    if (o == NULL)
        return null_error();
    if (PyLong_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 */
        return (PyObject *)_PyLong_FromNbInt(o);
    }
    trunc_func = _PyObject_LookupSpecial(o, &PyId___trunc__);
    if (trunc_func) {
        PyObject *truncated = PyEval_CallObject(trunc_func, NULL);
        PyObject *int_instance;
        Py_DECREF(trunc_func);
        if (truncated == NULL || PyLong_Check(truncated))
            return truncated;
        /* __trunc__ is specified to return an Integral type,
           but int() needs to return a int. */
        m = truncated->ob_type->tp_as_number;
        if (m == NULL || m->nb_int == NULL) {
            PyErr_Format(
                PyExc_TypeError,
                "__trunc__ returned non-Integral (type %.200s)",
                truncated->ob_type->tp_name);
            Py_DECREF(truncated);
            return NULL;
        }
        int_instance = (PyObject *)_PyLong_FromNbInt(truncated);
        Py_DECREF(truncated);
        return int_instance;
    }
    if (PyErr_Occurred())
        return NULL;

    if (PyUnicode_Check(o))
        /* The below check is done in PyLong_FromUnicode(). */
        return PyLong_FromUnicodeObject(o, 10);

    if (PyObject_GetBuffer(o, &view, PyBUF_SIMPLE) == 0) {
        /* need to do extra error checking that PyLong_FromString()
         * doesn't do.  In particular int('9\x005') must raise an
         * exception, not truncate at the null.
         */
        PyObject *result = _PyLong_FromBytes(view.buf, view.len, 10);
        PyBuffer_Release(&view);
        return result;
    }

    return type_error("int() argument must be a string, a bytes-like object "
                      "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);
}


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);
    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");
    Py_DECREF(index);
    return res;
}


/* Operations on sequences */

int
PySequence_Check(PyObject *s)
{
    if (PyDict_Check(s))
        return 0;
    return s != NULL && 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 = PyLong_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 && 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 && 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 = PyLong_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)
{
    PyMappingMethods *mp;

    if (!s) return null_error();

    mp = s->ob_type->tp_as_mapping;
    if (mp && 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)
{
    PyMappingMethods *mp;

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

    mp = s->ob_type->tp_as_mapping;
    if (mp && 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)
{
    PyMappingMethods *mp;

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

    mp = s->ob_type->tp_as_mapping;
    if (mp && mp->mp_ass_subscript) {
        int res;
        PyObject *slice = _PySlice_FromIndices(i1, i2);
        if (!slice)
            return -1;
        res = mp->mp_ass_subscript(s, slice, NULL);
        Py_DECREF(slice);
        return res;
    }
    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;
    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)
{
    return o && o->ob_type->tp_as_mapping &&
        o->ob_type->tp_as_mapping->mp_subscript;
}

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, const char *key)
{
    PyObject *okey, *r;

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

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

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

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

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

int
PyMapping_HasKeyString(PyObject *o, const 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;
}

PyObject *
PyMapping_Keys(PyObject *o)
{
    PyObject *keys;
    PyObject *fast;
    _Py_IDENTIFIER(keys);

    if (PyDict_CheckExact(o))
        return PyDict_Keys(o);
    keys = _PyObject_CallMethodId(o, &PyId_keys, NULL);
    if (keys == NULL)
        return NULL;
    fast = PySequence_Fast(keys, "o.keys() are not iterable");
    Py_DECREF(keys);
    return fast;
}

PyObject *
PyMapping_Items(PyObject *o)
{
    PyObject *items;
    PyObject *fast;
    _Py_IDENTIFIER(items);

    if (PyDict_CheckExact(o))
        return PyDict_Items(o);
    items = _PyObject_CallMethodId(o, &PyId_items, NULL);
    if (items == NULL)
        return NULL;
    fast = PySequence_Fast(items, "o.items() are not iterable");
    Py_DECREF(items);
    return fast;
}

PyObject *
PyMapping_Values(PyObject *o)
{
    PyObject *values;
    PyObject *fast;
    _Py_IDENTIFIER(values);

    if (PyDict_CheckExact(o))
        return PyDict_Values(o);
    values = _PyObject_CallMethodId(o, &PyId_values, NULL);
    if (values == NULL)
        return NULL;
    fast = PySequence_Fast(values, "o.values() are not iterable");
    Py_DECREF(values);
    return fast;
}

/* 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*
_Py_CheckFunctionResult(PyObject *result, const char *func_name)
{
    int err_occurred = (PyErr_Occurred() != NULL);

#ifdef NDEBUG
    /* In debug mode: abort() with an assertion error. Use two different
       assertions, so if an assertion fails, it's possible to know
       if result was set or not and if an exception was raised or not. */
    if (result != NULL)
        assert(!err_occurred);
    else
        assert(err_occurred);
#endif

    if (result == NULL) {
        if (!err_occurred) {
            PyErr_Format(PyExc_SystemError,
                         "NULL result without error in %s", func_name);
            return NULL;
        }
    }
    else {
        if (err_occurred) {
            PyObject *exc, *val, *tb;
            PyErr_Fetch(&exc, &val, &tb);

            Py_DECREF(result);

            PyErr_Format(PyExc_SystemError,
                         "result with error in %s", func_name);
            _PyErr_ChainExceptions(exc, val, tb);
            return NULL;
        }
    }
    return result;
}

PyObject *
PyObject_Call(PyObject *func, PyObject *arg, PyObject *kw)
{
    ternaryfunc call;
    PyObject *result;

    /* PyObject_Call() must not be called with an exception set,
       because it may clear it (directly or indirectly) and so the
       caller looses its exception */
    assert(!PyErr_Occurred());

    call = func->ob_type->tp_call;
    if (call == NULL) {
        PyErr_Format(PyExc_TypeError, "'%.200s' object is not callable",
                     func->ob_type->tp_name);
        return NULL;
    }

    if (Py_EnterRecursiveCall(" while calling a Python object"))
        return NULL;

    result = (*call)(func, arg, kw);

    Py_LeaveRecursiveCall();

    return _Py_CheckFunctionResult(result, "PyObject_Call");
}

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, const 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);
    if (args == NULL)
        return NULL;

    return call_function_tail(callable, args);
}

PyObject *
_PyObject_CallFunction_SizeT(PyObject *callable, const 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);
}

static PyObject*
callmethod(PyObject* func, const char *format, va_list va, int is_size_t)
{
    PyObject *retval = NULL;
    PyObject *args;

    if (!PyCallable_Check(func)) {
        type_error("attribute of type '%.200s' is not callable", func);
        goto exit;
    }

    if (format && *format) {
        if (is_size_t)
            args = _Py_VaBuildValue_SizeT(format, va);
        else
            args = Py_VaBuildValue(format, 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(PyObject *o, const char *name, const char *format, ...)
{
    va_list va;
    PyObject *func = NULL;
    PyObject *retval = NULL;

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

    func = PyObject_GetAttrString(o, name);
    if (func == NULL)
        return NULL;

    va_start(va, format);
    retval = callmethod(func, format, va, 0);
    va_end(va);
    return retval;
}

PyObject *
_PyObject_CallMethodId(PyObject *o, _Py_Identifier *name,
                       const char *format, ...)
{
    va_list va;
    PyObject *func = NULL;
    PyObject *retval = NULL;

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

    func = _PyObject_GetAttrId(o, name);
    if (func == NULL)
        return NULL;

    va_start(va, format);
    retval = callmethod(func, format, va, 0);
    va_end(va);
    return retval;
}

PyObject *
_PyObject_CallMethod_SizeT(PyObject *o, const char *name,
                           const char *format, ...)
{
    va_list va;
    PyObject *func = NULL;
    PyObject *retval;

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

    func = PyObject_GetAttrString(o, name);
    if (func == NULL)
        return NULL;
    va_start(va, format);
    retval = callmethod(func, format, va, 1);
    va_end(va);
    return retval;
}

PyObject *
_PyObject_CallMethodId_SizeT(PyObject *o, _Py_Identifier *name,
                             const char *format, ...)
{
    va_list va;
    PyObject *func = NULL;
    PyObject *retval;

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

    func = _PyObject_GetAttrId(o, name);
    if (func == NULL) {
        return NULL;
    }
    va_start(va, format);
    retval = callmethod(func, format, va, 1);
    va_end(va);
    return retval;
}

static PyObject *
objargs_mktuple(va_list va)
{
    int i, n = 0;
    va_list countva;
    PyObject *result, *tmp;

        Py_VA_COPY(countva, va);

    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_CallMethodIdObjArgs(PyObject *callable,
        struct _Py_Identifier *name, ...)
{
    PyObject *args, *tmp;
    va_list vargs;

    if (callable == NULL || name == NULL)
        return null_error();

    callable = _PyObject_GetAttrId(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:
 *
 * 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)
{
    _Py_IDENTIFIER(__bases__);
    PyObject *bases;

    Py_ALLOW_RECURSION
    bases = _PyObject_GetAttrId(cls, &PyId___bases__);
    Py_END_ALLOW_RECURSION
    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;
    int retval = 0;
    _Py_IDENTIFIER(__class__);

    if (PyType_Check(cls)) {
        retval = PyObject_TypeCheck(inst, (PyTypeObject *)cls);
        if (retval == 0) {
            PyObject *c = _PyObject_GetAttrId(inst, &PyId___class__);
            if (c == NULL) {
                if (PyErr_ExceptionMatches(PyExc_AttributeError))
                    PyErr_Clear();
                else
                    retval = -1;
            }
            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 type or tuple of types"))
            return -1;
        icls = _PyObject_GetAttrId(inst, &PyId___class__);
        if (icls == NULL) {
            if (PyErr_ExceptionMatches(PyExc_AttributeError))
                PyErr_Clear();
            else
                retval = -1;
        }
        else {
            retval = abstract_issubclass(icls, cls);
            Py_DECREF(icls);
        }
    }

    return retval;
}

int
PyObject_IsInstance(PyObject *inst, PyObject *cls)
{
    _Py_IDENTIFIER(__instancecheck__);
    PyObject *checker;

    /* Quick test for an exact match */
    if (Py_TYPE(inst) == (PyTypeObject *)cls)
        return 1;

    /* We know what type's __instancecheck__ does. */
    if (PyType_CheckExact(cls)) {
        return recursive_isinstance(inst, cls);
    }

    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;
    }

    checker = _PyObject_LookupSpecial(cls, &PyId___instancecheck__);
    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;
    /* Probably never reached anymore. */
    return recursive_isinstance(inst, cls);
}

static  int
recursive_issubclass(PyObject *derived, PyObject *cls)
{
    if (PyType_Check(cls) && PyType_Check(derived)) {
        /* Fast path (non-recursive) */
        return PyType_IsSubtype((PyTypeObject *)derived, (PyTypeObject *)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;

    return abstract_issubclass(derived, cls);
}

int
PyObject_IsSubclass(PyObject *derived, PyObject *cls)
{
    _Py_IDENTIFIER(__subclasscheck__);
    PyObject *checker;

    /* We know what type's __subclasscheck__ does. */
    if (PyType_CheckExact(cls)) {
        /* Quick test for an exact match */
        if (derived == cls)
            return 1;
        return recursive_issubclass(derived, cls);
    }

    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;
    }

    checker = _PyObject_LookupSpecial(cls, &PyId___subclasscheck__);
    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;
    /* Probably never reached anymore. */
    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;
    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;
}


/*
 * Flatten a sequence of bytes() objects into a C array of
 * NULL terminated string pointers with a NULL char* terminating the array.
 * (ie: an argv or env list)
 *
 * Memory allocated for the returned list is allocated using PyMem_Malloc()
 * and MUST be freed by _Py_FreeCharPArray().
 */
char *const *
_PySequence_BytesToCharpArray(PyObject* self)
{
    char **array;
    Py_ssize_t i, argc;
    PyObject *item = NULL;
    Py_ssize_t size;

    argc = PySequence_Size(self);
    if (argc == -1)
        return NULL;

    assert(argc >= 0);

    if ((size_t)argc > (PY_SSIZE_T_MAX-sizeof(char *)) / sizeof(char *)) {
        PyErr_NoMemory();
        return NULL;
    }

    array = PyMem_Malloc((argc + 1) * sizeof(char *));
    if (array == NULL) {
        PyErr_NoMemory();
        return NULL;
    }
    for (i = 0; i < argc; ++i) {
        char *data;
        item = PySequence_GetItem(self, i);
        if (item == NULL) {
            /* NULL terminate before freeing. */
            array[i] = NULL;
            goto fail;
        }
        data = PyBytes_AsString(item);
        if (data == NULL) {
            /* NULL terminate before freeing. */
            array[i] = NULL;
            goto fail;
        }
        size = PyBytes_GET_SIZE(item) + 1;
        array[i] = PyMem_Malloc(size);
        if (!array[i]) {
            PyErr_NoMemory();
            goto fail;
        }
        memcpy(array[i], data, size);
        Py_DECREF(item);
    }
    array[argc] = NULL;

    return array;

fail:
    Py_XDECREF(item);
    _Py_FreeCharPArray(array);
    return NULL;
}


/* Free's a NULL terminated char** array of C strings. */
void
_Py_FreeCharPArray(char *const array[])
{
    Py_ssize_t i;
    for (i = 0; array[i] != NULL; ++i) {
        PyMem_Free(array[i]);
    }
    PyMem_Free((void*)array);
}