/* enumerate object */

#include "Python.h"

#include "pycore_call.h"          // _PyObject_CallNoArgs()

#include "pycore_long.h"          // _PyLong_GetOne()

#include "pycore_modsupport.h"    // _PyArg_NoKwnames()

#include "pycore_object.h"        // _PyObject_GC_TRACK()

#include "pycore_unicodeobject.h" // _PyUnicode_EqualToASCIIString

#include "pycore_tuple.h"         // _PyTuple_Recycle()

#include "clinic/enumobject.c.h"

/*[clinic input]

class enumerate "enumobject *" "&PyEnum_Type"

class reversed "reversedobject *" "&PyReversed_Type"

[clinic start generated code]*/

/*[clinic end generated code: output=da39a3ee5e6b4b0d input=d2dfdf1a88c88975]*/

typedef struct {

    PyObject_HEAD

    Py_ssize_t en_index;           /* current index of enumeration */

    PyObject* en_sit;              /* secondary iterator of enumeration */

    PyObject* en_result;           /* result tuple  */

    PyObject* en_longindex;        /* index for sequences >= PY_SSIZE_T_MAX */

    PyObject* one;                 /* borrowed reference */

} enumobject;

#define _enumobject_CAST(op)    ((enumobject *)(op))

/*[clinic input]

@vectorcall

@classmethod

enumerate.__new__ as enum_new

    iterable: object

        an object supporting iteration

    start: object = 0

Return an enumerate object.

The enumerate object yields pairs containing a count (from start, which

defaults to zero) and a value yielded by the iterable argument.

enumerate is useful for obtaining an indexed list:

    (0, seq[0]), (1, seq[1]), (2, seq[2]), ...

[clinic start generated code]*/

static PyObject *

enum_new_impl(PyTypeObject *type, PyObject *iterable, PyObject *start)

/*[clinic end generated code: output=e95e6e439f812c10 input=a139e88889360e8f]*/

{

    enumobject *en;

    en = (enumobject *)type->tp_alloc(type, 0);

    if (en == NULL)

        return NULL;

    if (start != NULL) {

        start = PyNumber_Index(start);

        if (start == NULL) {

            Py_DECREF(en);

            return NULL;

        }

        assert(PyLong_Check(start));

        en->en_index = PyLong_AsSsize_t(start);

        if (en->en_index == -1 && PyErr_Occurred()) {

            PyErr_Clear();

            en->en_index = PY_SSIZE_T_MAX;

            en->en_longindex = start;

        } else {

            en->en_longindex = NULL;

            Py_DECREF(start);

        }

    } else {

        en->en_index = 0;

        en->en_longindex = NULL;

    }

    en->en_sit = PyObject_GetIter(iterable);

    if (en->en_sit == NULL) {

        Py_DECREF(en);

        return NULL;

    }

    en->en_result = _PyTuple_FromPairSteal(Py_None, Py_None);

    if (en->en_result == NULL) {

        Py_DECREF(en);

        return NULL;

    }

    en->one = _PyLong_GetOne();    /* borrowed reference */

    return (PyObject *)en;

}

static void

enum_dealloc(PyObject *op)

{

    enumobject *en = _enumobject_CAST(op);

    PyObject_GC_UnTrack(en);

    Py_XDECREF(en->en_sit);

    Py_XDECREF(en->en_result);

    Py_XDECREF(en->en_longindex);

    Py_TYPE(en)->tp_free(en);

}

static int

enum_traverse(PyObject *op, visitproc visit, void *arg)

{

    enumobject *en = _enumobject_CAST(op);

    Py_VISIT(en->en_sit);

    Py_VISIT(en->en_result);

    Py_VISIT(en->en_longindex);

    return 0;

}

// increment en_longindex with lock held, return the next index to be used

// or NULL on error

static inline PyObject *

increment_longindex_lock_held(enumobject *en)

{

    if (en->en_longindex == NULL) {

        en->en_longindex = PyLong_FromSsize_t(PY_SSIZE_T_MAX);

        if (en->en_longindex == NULL) {

            return NULL;

        }

    }

    assert(en->en_longindex != NULL);

    // We hold one reference to "next_index" (a.k.a. the old value of

    // en->en_longindex); we'll either return it or keep it in en->en_longindex

    PyObject *next_index = en->en_longindex;

    PyObject *stepped_up = PyNumber_Add(next_index, en->one);

    if (stepped_up == NULL) {

        return NULL;

    }

    en->en_longindex = stepped_up;

    return next_index;

}

static PyObject *

enum_next_long(enumobject *en, PyObject* next_item)

{

    PyObject *result = en->en_result;

    PyObject *next_index;

    PyObject *old_index;

    PyObject *old_item;

    Py_BEGIN_CRITICAL_SECTION(en);

    next_index = increment_longindex_lock_held(en);

    Py_END_CRITICAL_SECTION();

    if (next_index == NULL) {

        Py_DECREF(next_item);

        return NULL;

    }

    if (_PyObject_IsUniquelyReferenced(result)) {

        Py_INCREF(result);

        old_index = PyTuple_GET_ITEM(result, 0);

        old_item = PyTuple_GET_ITEM(result, 1);

        PyTuple_SET_ITEM(result, 0, next_index);

        PyTuple_SET_ITEM(result, 1, next_item);

        Py_DECREF(old_index);

        Py_DECREF(old_item);

        // bpo-42536: The GC may have untracked this result tuple. Since we're

        // recycling it, make sure it's tracked again:

        _PyTuple_Recycle(result);

        return result;

    }

    return _PyTuple_FromPairSteal(next_index, next_item);

}

static PyObject *

enum_next(PyObject *op)

{

    enumobject *en = _enumobject_CAST(op);

    PyObject *next_index;

    PyObject *next_item;

    PyObject *result = en->en_result;

    PyObject *it = en->en_sit;

    PyObject *old_index;

    PyObject *old_item;

    next_item = (*Py_TYPE(it)->tp_iternext)(it);

    if (next_item == NULL)

        return NULL;

    Py_ssize_t en_index = FT_ATOMIC_LOAD_SSIZE_RELAXED(en->en_index);

    if (en_index == PY_SSIZE_T_MAX)

        return enum_next_long(en, next_item);

    next_index = PyLong_FromSsize_t(en_index);

    if (next_index == NULL) {

        Py_DECREF(next_item);

        return NULL;

    }

    FT_ATOMIC_STORE_SSIZE_RELAXED(en->en_index, en_index + 1);

    if (_PyObject_IsUniquelyReferenced(result)) {

        Py_INCREF(result);

        old_index = PyTuple_GET_ITEM(result, 0);

        old_item = PyTuple_GET_ITEM(result, 1);

        PyTuple_SET_ITEM(result, 0, next_index);

        PyTuple_SET_ITEM(result, 1, next_item);

        Py_DECREF(old_index);

        Py_DECREF(old_item);

        // bpo-42536: The GC may have untracked this result tuple. Since we're

        // recycling it, make sure it's tracked again:

        _PyTuple_Recycle(result);

        return result;

    }

    return _PyTuple_FromPairSteal(next_index, next_item);

}

static PyObject *

enum_reduce(PyObject *op, PyObject *Py_UNUSED(ignored))

{

    enumobject *en = _enumobject_CAST(op);

    PyObject *result;

    Py_BEGIN_CRITICAL_SECTION(en);

    if (en->en_longindex != NULL) {

        result = Py_BuildValue("O(OO)", Py_TYPE(en), en->en_sit, en->en_longindex);

    }

    else {

        Py_ssize_t en_index = FT_ATOMIC_LOAD_SSIZE_RELAXED(en->en_index);

        result = Py_BuildValue("O(On)", Py_TYPE(en), en->en_sit, en_index);

    }

    Py_END_CRITICAL_SECTION();

    return result;

}

PyDoc_STRVAR(reduce_doc, "Return state information for pickling.");

static PyMethodDef enum_methods[] = {

    {"__reduce__", enum_reduce, METH_NOARGS, reduce_doc},

    {"__class_getitem__",    Py_GenericAlias,

    METH_O|METH_CLASS,       PyDoc_STR("'enumerate' objects are generic over the type of their values")},

    {NULL,              NULL}           /* sentinel */

};

PyTypeObject PyEnum_Type = {

    PyVarObject_HEAD_INIT(&PyType_Type, 0)

    "enumerate",                    /* tp_name */

    sizeof(enumobject),             /* tp_basicsize */

    0,                              /* tp_itemsize */

    /* methods */

    enum_dealloc,                   /* tp_dealloc */

    0,                              /* tp_vectorcall_offset */

    0,                              /* tp_getattr */

    0,                              /* tp_setattr */

    0,                              /* tp_as_async */

    0,                              /* 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 | Py_TPFLAGS_HAVE_GC |

        Py_TPFLAGS_BASETYPE,        /* tp_flags */

    enum_new__doc__,                /* tp_doc */

    enum_traverse,                  /* tp_traverse */

    0,                              /* tp_clear */

    0,                              /* tp_richcompare */

    0,                              /* tp_weaklistoffset */

    PyObject_SelfIter,              /* tp_iter */

    enum_next,                      /* tp_iternext */

    enum_methods,                   /* tp_methods */

    0,                              /* 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 */

    PyType_GenericAlloc,            /* tp_alloc */

    enum_new,                       /* tp_new */

    PyObject_GC_Del,                /* tp_free */

    .tp_vectorcall = enum_vectorcall

};

/* Reversed Object ***************************************************************/

typedef struct {

    PyObject_HEAD

    Py_ssize_t      index;

    PyObject* seq;

} reversedobject;

#define _reversedobject_CAST(op)    ((reversedobject *)(op))

/*[clinic input]

@vectorcall

@classmethod

reversed.__new__ as reversed_new

    object as seq: object

    /

Return a reverse iterator over the values of the given sequence.

[clinic start generated code]*/

static PyObject *

reversed_new_impl(PyTypeObject *type, PyObject *seq)

/*[clinic end generated code: output=f7854cc1df26f570 input=7db568182ab28c59]*/

{

    Py_ssize_t n;

    PyObject *reversed_meth;

    reversedobject *ro;

    reversed_meth = _PyObject_LookupSpecial(seq, &_Py_ID(__reversed__));

    if (reversed_meth == Py_None) {

        Py_DECREF(reversed_meth);

        PyErr_Format(PyExc_TypeError,

                     "'%.200s' object is not reversible",

                     Py_TYPE(seq)->tp_name);

        return NULL;

    }

    if (reversed_meth != NULL) {

        PyObject *res = _PyObject_CallNoArgs(reversed_meth);

        Py_DECREF(reversed_meth);

        return res;

    }

    else if (PyErr_Occurred())

        return NULL;

    if (!PySequence_Check(seq)) {

        PyErr_Format(PyExc_TypeError,

                     "'%.200s' object is not reversible",

                     Py_TYPE(seq)->tp_name);

        return NULL;

    }

    n = PySequence_Size(seq);

    if (n == -1)

        return NULL;

    ro = (reversedobject *)type->tp_alloc(type, 0);

    if (ro == NULL)

        return NULL;

    ro->index = n-1;

    ro->seq = Py_NewRef(seq);

    return (PyObject *)ro;

}

static void

reversed_dealloc(PyObject *op)

{

    reversedobject *ro = _reversedobject_CAST(op);

    PyObject_GC_UnTrack(ro);

    Py_XDECREF(ro->seq);

    Py_TYPE(ro)->tp_free(ro);

}

static int

reversed_traverse(PyObject *op, visitproc visit, void *arg)

{

    reversedobject *ro = _reversedobject_CAST(op);

    Py_VISIT(ro->seq);

    return 0;

}

static PyObject *

reversed_next(PyObject *op)

{

    reversedobject *ro = _reversedobject_CAST(op);

    PyObject *item;

    Py_ssize_t index = FT_ATOMIC_LOAD_SSIZE_RELAXED(ro->index);

    if (index >= 0) {

        item = PySequence_GetItem(ro->seq, index);

        if (item != NULL) {

            FT_ATOMIC_STORE_SSIZE_RELAXED(ro->index, index - 1);

            return item;

        }

        if (PyErr_ExceptionMatches(PyExc_IndexError) ||

            PyErr_ExceptionMatches(PyExc_StopIteration))

            PyErr_Clear();

    }

    FT_ATOMIC_STORE_SSIZE_RELAXED(ro->index, -1);

#ifndef Py_GIL_DISABLED

    Py_CLEAR(ro->seq);

#endif

    return NULL;

}

static PyObject *

reversed_len(PyObject *op, PyObject *Py_UNUSED(ignored))

{

    reversedobject *ro = _reversedobject_CAST(op);

    Py_ssize_t position, seqsize;

    Py_ssize_t index = FT_ATOMIC_LOAD_SSIZE_RELAXED(ro->index);

    if (index == -1)

        return PyLong_FromLong(0);

    assert(ro->seq != NULL);

    seqsize = PySequence_Size(ro->seq);

    if (seqsize == -1)

        return NULL;

    position = index + 1;

    return PyLong_FromSsize_t((seqsize < position)  ?  0  :  position);

}

PyDoc_STRVAR(length_hint_doc, "Private method returning an estimate of len(list(it)).");

static PyObject *

reversed_reduce(PyObject *op, PyObject *Py_UNUSED(ignored))

{

    reversedobject *ro = _reversedobject_CAST(op);

    Py_ssize_t index = FT_ATOMIC_LOAD_SSIZE_RELAXED(ro->index);

    if (index != -1) {

        return Py_BuildValue("O(O)n", Py_TYPE(ro), ro->seq, ro->index);

    }

    else {

        return Py_BuildValue("O(())", Py_TYPE(ro));

    }

}

static PyObject *

reversed_setstate(PyObject *op, PyObject *state)

{

    reversedobject *ro = _reversedobject_CAST(op);

    Py_ssize_t index = PyLong_AsSsize_t(state);

    if (index == -1 && PyErr_Occurred())

        return NULL;

    Py_ssize_t ro_index = FT_ATOMIC_LOAD_SSIZE_RELAXED(ro->index);

    // if the iterator is exhausted we do not set the state

    // this is for backwards compatibility reasons. in practice this situation

    // will not occur, see gh-120971

    if (ro_index != -1) {

        Py_ssize_t n = PySequence_Size(ro->seq);

        if (n < 0)

            return NULL;

        if (index < -1)

            index = -1;

        else if (index > n-1)

            index = n-1;

        FT_ATOMIC_STORE_SSIZE_RELAXED(ro->index, index);

    }

    Py_RETURN_NONE;

}

PyDoc_STRVAR(setstate_doc, "Set state information for unpickling.");

static PyMethodDef reversediter_methods[] = {

    {"__length_hint__", reversed_len, METH_NOARGS, length_hint_doc},

    {"__reduce__", reversed_reduce, METH_NOARGS, reduce_doc},

    {"__setstate__", reversed_setstate, METH_O, setstate_doc},

    {NULL,              NULL}           /* sentinel */

};

PyTypeObject PyReversed_Type = {

    PyVarObject_HEAD_INIT(&PyType_Type, 0)

    "reversed",                     /* tp_name */

    sizeof(reversedobject),         /* tp_basicsize */

    0,                              /* tp_itemsize */

    /* methods */

    reversed_dealloc,               /* tp_dealloc */

    0,                              /* tp_vectorcall_offset */

    0,                              /* tp_getattr */

    0,                              /* tp_setattr */

    0,                              /* tp_as_async */

    0,                              /* 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 | Py_TPFLAGS_HAVE_GC |

        Py_TPFLAGS_BASETYPE,        /* tp_flags */

    reversed_new__doc__,            /* tp_doc */

    reversed_traverse,              /* tp_traverse */

    0,                              /* tp_clear */

    0,                              /* tp_richcompare */

    0,                              /* tp_weaklistoffset */

    PyObject_SelfIter,              /* tp_iter */

    reversed_next,                  /* tp_iternext */

    reversediter_methods,           /* tp_methods */

    0,                              /* 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 */

    PyType_GenericAlloc,            /* tp_alloc */

    reversed_new,                   /* tp_new */

    PyObject_GC_Del,                /* tp_free */

    .tp_vectorcall = reversed_vectorcall,

};