_functoolsmodule.c

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

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

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

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

static PyTypeObject partial_type;

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

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

    pargs = pkw = NULL;
    func = PyTuple_GET_ITEM(args, 0);
    if (Py_TYPE(func) == &partial_type && type == &partial_type) {
        partialobject *part = (partialobject *)func;
        if (part->dict == NULL) {
            pargs = part->args;
            pkw = part->kw;
            func = part->fn;
            assert(PyTuple_Check(pargs));
            assert(PyDict_Check(pkw));
        }
    }
    if (!PyCallable_Check(func)) {
        PyErr_SetString(PyExc_TypeError,
                        "the first argument must be callable");
        return NULL;
    }

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

    pto->fn = func;
    Py_INCREF(func);

    nargs = PyTuple_GetSlice(args, 1, PY_SSIZE_T_MAX);
    if (nargs == NULL) {
        Py_DECREF(pto);
        return NULL;
    }
    if (pargs == NULL || PyTuple_GET_SIZE(pargs) == 0) {
        pto->args = nargs;
        Py_INCREF(nargs);
    }
    else if (PyTuple_GET_SIZE(nargs) == 0) {
        pto->args = pargs;
        Py_INCREF(pargs);
    }
    else {
        pto->args = PySequence_Concat(pargs, nargs);
        if (pto->args == NULL) {
            Py_DECREF(nargs);
            Py_DECREF(pto);
            return NULL;
        }
        assert(PyTuple_Check(pto->args));
    }
    Py_DECREF(nargs);

    if (pkw == NULL || PyDict_Size(pkw) == 0) {
        if (kw == NULL) {
            pto->kw = PyDict_New();
        }
        else if (Py_REFCNT(kw) == 1) {
            Py_INCREF(kw);
            pto->kw = kw;
        }
        else {
            pto->kw = PyDict_Copy(kw);
        }
    }
    else {
        pto->kw = PyDict_Copy(pkw);
        if (kw != NULL && pto->kw != NULL) {
            if (PyDict_Merge(pto->kw, kw, 1) != 0) {
                Py_DECREF(pto);
                return NULL;
            }
        }
    }
    if (pto->kw == NULL) {
        Py_DECREF(pto);
        return NULL;
    }

    return (PyObject *)pto;
}

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

static PyObject *
partial_call(partialobject *pto, PyObject *args, PyObject *kw)
{
    PyObject *ret;
    PyObject *argappl, *kwappl;
    PyObject **stack;
    Py_ssize_t nargs;

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

    if (PyTuple_GET_SIZE(pto->args) == 0) {
        stack = &PyTuple_GET_ITEM(args, 0);
        nargs = PyTuple_GET_SIZE(args);
        argappl = NULL;
    }
    else if (PyTuple_GET_SIZE(args) == 0) {
        stack = &PyTuple_GET_ITEM(pto->args, 0);
        nargs = PyTuple_GET_SIZE(pto->args);
        argappl = NULL;
    }
    else {
        stack = NULL;
        argappl = PySequence_Concat(pto->args, args);
        if (argappl == NULL) {
            return NULL;
        }

        assert(PyTuple_Check(argappl));
    }

    if (PyDict_Size(pto->kw) == 0) {
        kwappl = kw;
        Py_XINCREF(kwappl);
    }
    else {
        kwappl = PyDict_Copy(pto->kw);
        if (kwappl == NULL) {
            Py_XDECREF(argappl);
            return NULL;
        }

        if (kw != NULL) {
            if (PyDict_Merge(kwappl, kw, 1) != 0) {
                Py_XDECREF(argappl);
                Py_DECREF(kwappl);
                return NULL;
            }
        }
    }

    if (stack) {
        ret = _PyObject_FastCallDict(pto->fn, stack, nargs, kwappl);
    }
    else {
        ret = PyObject_Call(pto->fn, argappl, kwappl);
        Py_DECREF(argappl);
    }
    Py_XDECREF(kwappl);
    return ret;
}

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

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

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

static PyGetSetDef partial_getsetlist[] = {
    {"__dict__", PyObject_GenericGetDict, PyObject_GenericSetDict},
    {NULL} /* Sentinel */
};

static PyObject *
partial_repr(partialobject *pto)
{
    PyObject *result = NULL;
    PyObject *arglist;
    Py_ssize_t i, n;
    PyObject *key, *value;
    int status;

    status = Py_ReprEnter((PyObject *)pto);
    if (status != 0) {
        if (status < 0)
            return NULL;
        return PyUnicode_FromString("...");
    }

    arglist = PyUnicode_FromString("");
    if (arglist == NULL)
        goto done;
    /* Pack positional arguments */
    assert (PyTuple_Check(pto->args));
    n = PyTuple_GET_SIZE(pto->args);
    for (i = 0; i < n; i++) {
        Py_SETREF(arglist, PyUnicode_FromFormat("%U, %R", arglist,
                                        PyTuple_GET_ITEM(pto->args, i)));
        if (arglist == NULL)
            goto done;
    }
    /* Pack keyword arguments */
    assert (PyDict_Check(pto->kw));
    for (i = 0; PyDict_Next(pto->kw, &i, &key, &value);) {
        /* Prevent key.__str__ from deleting the value. */
        Py_INCREF(value);
        Py_SETREF(arglist, PyUnicode_FromFormat("%U, %S=%R", arglist,
                                                key, value));
        Py_DECREF(value);
        if (arglist == NULL)
            goto done;
    }
    result = PyUnicode_FromFormat("%s(%R%U)", Py_TYPE(pto)->tp_name,
                                  pto->fn, arglist);
    Py_DECREF(arglist);

 done:
    Py_ReprLeave((PyObject *)pto);
    return result;
}

/* Pickle strategy:
   __reduce__ by itself doesn't support getting kwargs in the unpickle
   operation so we define a __setstate__ that replaces all the information
   about the partial.  If we only replaced part of it someone would use
   it as a hook to do strange things.
 */

static PyObject *
partial_reduce(partialobject *pto, PyObject *unused)
{
    return Py_BuildValue("O(O)(OOOO)", Py_TYPE(pto), pto->fn, pto->fn,
                         pto->args, pto->kw,
                         pto->dict ? pto->dict : Py_None);
}

static PyObject *
partial_setstate(partialobject *pto, PyObject *state)
{
    PyObject *fn, *fnargs, *kw, *dict;

    if (!PyTuple_Check(state) ||
        !PyArg_ParseTuple(state, "OOOO", &fn, &fnargs, &kw, &dict) ||
        !PyCallable_Check(fn) ||
        !PyTuple_Check(fnargs) ||
        (kw != Py_None && !PyDict_Check(kw)))
    {
        PyErr_SetString(PyExc_TypeError, "invalid partial state");
        return NULL;
    }

    if(!PyTuple_CheckExact(fnargs))
        fnargs = PySequence_Tuple(fnargs);
    else
        Py_INCREF(fnargs);
    if (fnargs == NULL)
        return NULL;

    if (kw == Py_None)
        kw = PyDict_New();
    else if(!PyDict_CheckExact(kw))
        kw = PyDict_Copy(kw);
    else
        Py_INCREF(kw);
    if (kw == NULL) {
        Py_DECREF(fnargs);
        return NULL;
    }

    Py_INCREF(fn);
    if (dict == Py_None)
        dict = NULL;
    else
        Py_INCREF(dict);

    Py_SETREF(pto->fn, fn);
    Py_SETREF(pto->args, fnargs);
    Py_SETREF(pto->kw, kw);
    Py_XSETREF(pto->dict, dict);
    Py_RETURN_NONE;
}

static PyMethodDef partial_methods[] = {
    {"__reduce__", (PyCFunction)partial_reduce, METH_NOARGS},
    {"__setstate__", (PyCFunction)partial_setstate, METH_O},
    {NULL,              NULL}           /* sentinel */
};

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


/* cmp_to_key ***************************************************************/

typedef struct {
    PyObject_HEAD
    PyObject *cmp;
    PyObject *object;
} keyobject;

static void
keyobject_dealloc(keyobject *ko)
{
    Py_DECREF(ko->cmp);
    Py_XDECREF(ko->object);
    PyObject_FREE(ko);
}

static int
keyobject_traverse(keyobject *ko, visitproc visit, void *arg)
{
    Py_VISIT(ko->cmp);
    if (ko->object)
        Py_VISIT(ko->object);
    return 0;
}

static int
keyobject_clear(keyobject *ko)
{
    Py_CLEAR(ko->cmp);
    if (ko->object)
        Py_CLEAR(ko->object);
    return 0;
}

static PyMemberDef keyobject_members[] = {
    {"obj", T_OBJECT,
     offsetof(keyobject, object), 0,
     PyDoc_STR("Value wrapped by a key function.")},
    {NULL}
};

static PyObject *
keyobject_call(keyobject *ko, PyObject *args, PyObject *kwds);

static PyObject *
keyobject_richcompare(PyObject *ko, PyObject *other, int op);

static PyTypeObject keyobject_type = {
    PyVarObject_HEAD_INIT(&PyType_Type, 0)
    "functools.KeyWrapper",             /* tp_name */
    sizeof(keyobject),                  /* tp_basicsize */
    0,                                  /* tp_itemsize */
    /* methods */
    (destructor)keyobject_dealloc,      /* tp_dealloc */
    0,                                  /* tp_print */
    0,                                  /* tp_getattr */
    0,                                  /* tp_setattr */
    0,                                  /* tp_reserved */
    0,                                  /* tp_repr */
    0,                                  /* tp_as_number */
    0,                                  /* tp_as_sequence */
    0,                                  /* tp_as_mapping */
    0,                                  /* tp_hash */
    (ternaryfunc)keyobject_call,        /* tp_call */
    0,                                  /* tp_str */
    PyObject_GenericGetAttr,            /* tp_getattro */
    0,                                  /* tp_setattro */
    0,                                  /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT,                 /* tp_flags */
    0,                                  /* tp_doc */
    (traverseproc)keyobject_traverse,   /* tp_traverse */
    (inquiry)keyobject_clear,           /* tp_clear */
    keyobject_richcompare,              /* tp_richcompare */
    0,                                  /* tp_weaklistoffset */
    0,                                  /* tp_iter */
    0,                                  /* tp_iternext */
    0,                                  /* tp_methods */
    keyobject_members,                  /* tp_members */
    0,                                  /* tp_getset */
};

static PyObject *
keyobject_call(keyobject *ko, PyObject *args, PyObject *kwds)
{
    PyObject *object;
    keyobject *result;
    static char *kwargs[] = {"obj", NULL};

    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O:K", kwargs, &object))
        return NULL;
    result = PyObject_New(keyobject, &keyobject_type);
    if (!result)
        return NULL;
    Py_INCREF(ko->cmp);
    result->cmp = ko->cmp;
    Py_INCREF(object);
    result->object = object;
    return (PyObject *)result;
}

static PyObject *
keyobject_richcompare(PyObject *ko, PyObject *other, int op)
{
    PyObject *res;
    PyObject *x;
    PyObject *y;
    PyObject *compare;
    PyObject *answer;
    static PyObject *zero;
    PyObject* stack[2];

    if (zero == NULL) {
        zero = PyLong_FromLong(0);
        if (!zero)
            return NULL;
    }

    if (Py_TYPE(other) != &keyobject_type){
        PyErr_Format(PyExc_TypeError, "other argument must be K instance");
        return NULL;
    }
    compare = ((keyobject *) ko)->cmp;
    assert(compare != NULL);
    x = ((keyobject *) ko)->object;
    y = ((keyobject *) other)->object;
    if (!x || !y){
        PyErr_Format(PyExc_AttributeError, "object");
        return NULL;
    }

    /* Call the user's comparison function and translate the 3-way
     * result into true or false (or error).
     */
    stack[0] = x;
    stack[1] = y;
    res = _PyObject_FastCall(compare, stack, 2);
    if (res == NULL) {
        return NULL;
    }

    answer = PyObject_RichCompare(res, zero, op);
    Py_DECREF(res);
    return answer;
}

static PyObject *
functools_cmp_to_key(PyObject *self, PyObject *args, PyObject *kwds)
{
    PyObject *cmp;
    static char *kwargs[] = {"mycmp", NULL};
    keyobject *object;

    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O:cmp_to_key", kwargs, &cmp))
        return NULL;
    object = PyObject_New(keyobject, &keyobject_type);
    if (!object)
        return NULL;
    Py_INCREF(cmp);
    object->cmp = cmp;
    object->object = NULL;
    return (PyObject *)object;
}

PyDoc_STRVAR(functools_cmp_to_key_doc,
"Convert a cmp= function into a key= function.");

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

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

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

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

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

    for (;;) {
        PyObject *op2;

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

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

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

    Py_DECREF(args);

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

    Py_DECREF(it);
    return result;

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

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

/* lru_cache object **********************************************************/

/* this object is used delimit args and keywords in the cache keys */
static PyObject *kwd_mark = NULL;

struct lru_list_elem;
struct lru_cache_object;

typedef struct lru_list_elem {
    PyObject_HEAD
    struct lru_list_elem *prev, *next;  /* borrowed links */
    Py_hash_t hash;
    PyObject *key, *result;
} lru_list_elem;

static void
lru_list_elem_dealloc(lru_list_elem *link)
{
    _PyObject_GC_UNTRACK(link);
    Py_XDECREF(link->key);
    Py_XDECREF(link->result);
    PyObject_GC_Del(link);
}

static int
lru_list_elem_traverse(lru_list_elem *link, visitproc visit, void *arg)
{
    Py_VISIT(link->key);
    Py_VISIT(link->result);
    return 0;
}

static int
lru_list_elem_clear(lru_list_elem *link)
{
    Py_CLEAR(link->key);
    Py_CLEAR(link->result);
    return 0;
}

static PyTypeObject lru_list_elem_type = {
    PyVarObject_HEAD_INIT(&PyType_Type, 0)
    "functools._lru_list_elem",         /* tp_name */
    sizeof(lru_list_elem),              /* tp_basicsize */
    0,                                  /* tp_itemsize */
    /* methods */
    (destructor)lru_list_elem_dealloc,  /* tp_dealloc */
    0,                                  /* tp_print */
    0,                                  /* tp_getattr */
    0,                                  /* tp_setattr */
    0,                                  /* tp_reserved */
    0,                                  /* tp_repr */
    0,                                  /* tp_as_number */
    0,                                  /* tp_as_sequence */
    0,                                  /* tp_as_mapping */
    0,                                  /* tp_hash */
    0,                                  /* tp_call */
    0,                                  /* tp_str */
    0,                                  /* tp_getattro */
    0,                                  /* tp_setattro */
    0,                                  /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,  /* tp_flags */
    0,                                  /* tp_doc */
    (traverseproc)lru_list_elem_traverse,  /* tp_traverse */
    (inquiry)lru_list_elem_clear,       /* tp_clear */
};


typedef PyObject *(*lru_cache_ternaryfunc)(struct lru_cache_object *, PyObject *, PyObject *);

typedef struct lru_cache_object {
    lru_list_elem root;  /* includes PyObject_HEAD */
    Py_ssize_t maxsize;
    PyObject *maxsize_O;
    PyObject *func;
    lru_cache_ternaryfunc wrapper;
    PyObject *cache;
    PyObject *cache_info_type;
    Py_ssize_t misses, hits;
    int typed;
    PyObject *dict;
    int full;
} lru_cache_object;

static PyTypeObject lru_cache_type;

static PyObject *
lru_cache_make_key(PyObject *args, PyObject *kwds, int typed)
{
    PyObject *key, *keyword, *value;
    Py_ssize_t key_size, pos, key_pos, kwds_size;

    /* short path, key will match args anyway, which is a tuple */
    if (!typed && !kwds) {
        Py_INCREF(args);
        return args;
    }

    kwds_size = kwds ? PyDict_Size(kwds) : 0;
    assert(kwds_size >= 0);

    key_size = PyTuple_GET_SIZE(args);
    if (kwds_size)
        key_size += kwds_size * 2 + 1;
    if (typed)
        key_size += PyTuple_GET_SIZE(args) + kwds_size;

    key = PyTuple_New(key_size);
    if (key == NULL)
        return NULL;

    key_pos = 0;
    for (pos = 0; pos < PyTuple_GET_SIZE(args); ++pos) {
        PyObject *item = PyTuple_GET_ITEM(args, pos);
        Py_INCREF(item);
        PyTuple_SET_ITEM(key, key_pos++, item);
    }
    if (kwds_size) {
        Py_INCREF(kwd_mark);
        PyTuple_SET_ITEM(key, key_pos++, kwd_mark);
        for (pos = 0; PyDict_Next(kwds, &pos, &keyword, &value);) {
            Py_INCREF(keyword);
            PyTuple_SET_ITEM(key, key_pos++, keyword);
            Py_INCREF(value);
            PyTuple_SET_ITEM(key, key_pos++, value);
        }
        assert(key_pos == PyTuple_GET_SIZE(args) + kwds_size * 2 + 1);
    }
    if (typed) {
        for (pos = 0; pos < PyTuple_GET_SIZE(args); ++pos) {
            PyObject *item = (PyObject *)Py_TYPE(PyTuple_GET_ITEM(args, pos));
            Py_INCREF(item);
            PyTuple_SET_ITEM(key, key_pos++, item);
        }
        if (kwds_size) {
            for (pos = 0; PyDict_Next(kwds, &pos, &keyword, &value);) {
                PyObject *item = (PyObject *)Py_TYPE(value);
                Py_INCREF(item);
                PyTuple_SET_ITEM(key, key_pos++, item);
            }
        }
    }
    assert(key_pos == key_size);
    return key;
}

static PyObject *
uncached_lru_cache_wrapper(lru_cache_object *self, PyObject *args, PyObject *kwds)
{
    PyObject *result = PyObject_Call(self->func, args, kwds);
    if (!result)
        return NULL;
    self->misses++;
    return result;
}

static PyObject *
infinite_lru_cache_wrapper(lru_cache_object *self, PyObject *args, PyObject *kwds)
{
    PyObject *result;
    Py_hash_t hash;
    PyObject *key = lru_cache_make_key(args, kwds, self->typed);
    if (!key)
        return NULL;
    hash = PyObject_Hash(key);
    if (hash == -1) {
        Py_DECREF(key);
        return NULL;
    }
    result = _PyDict_GetItem_KnownHash(self->cache, key, hash);
    if (result) {
        Py_INCREF(result);
        self->hits++;
        Py_DECREF(key);
        return result;
    }
    if (PyErr_Occurred()) {
        Py_DECREF(key);
        return NULL;
    }
    result = PyObject_Call(self->func, args, kwds);
    if (!result) {
        Py_DECREF(key);
        return NULL;
    }
    if (_PyDict_SetItem_KnownHash(self->cache, key, result, hash) < 0) {
        Py_DECREF(result);
        Py_DECREF(key);
        return NULL;
    }
    Py_DECREF(key);
    self->misses++;
    return result;
}

static void
lru_cache_extricate_link(lru_list_elem *link)
{
    link->prev->next = link->next;
    link->next->prev = link->prev;
}

static void
lru_cache_append_link(lru_cache_object *self, lru_list_elem *link)
{
    lru_list_elem *root = &self->root;
    lru_list_elem *last = root->prev;
    last->next = root->prev = link;
    link->prev = last;
    link->next = root;
}

static PyObject *
bounded_lru_cache_wrapper(lru_cache_object *self, PyObject *args, PyObject *kwds)
{
    lru_list_elem *link;
    PyObject *key, *result;
    Py_hash_t hash;

    key = lru_cache_make_key(args, kwds, self->typed);
    if (!key)
        return NULL;
    hash = PyObject_Hash(key);
    if (hash == -1) {
        Py_DECREF(key);
        return NULL;
    }
    link  = (lru_list_elem *)_PyDict_GetItem_KnownHash(self->cache, key, hash);
    if (link) {
        lru_cache_extricate_link(link);
        lru_cache_append_link(self, link);
        self->hits++;
        result = link->result;
        Py_INCREF(result);
        Py_DECREF(key);
        return result;
    }
    if (PyErr_Occurred()) {
        Py_DECREF(key);
        return NULL;
    }
    result = PyObject_Call(self->func, args, kwds);
    if (!result) {
        Py_DECREF(key);
        return NULL;
    }
    if (self->full && self->root.next != &self->root) {
        /* Use the oldest item to store the new key and result. */
        PyObject *oldkey, *oldresult, *popresult;
        /* Extricate the oldest item. */
        link = self->root.next;
        lru_cache_extricate_link(link);
        /* Remove it from the cache.
           The cache dict holds one reference to the link,
           and the linked list holds yet one reference to it. */
        popresult = _PyDict_Pop_KnownHash(self->cache,
                                          link->key, link->hash,
                                          Py_None);
        if (popresult == Py_None) {
            /* Getting here means that this same key was added to the
               cache while the lock was released.  Since the link
               update is already done, we need only return the
               computed result and update the count of misses. */
            Py_DECREF(popresult);
            Py_DECREF(link);
            Py_DECREF(key);
        }
        else if (popresult == NULL) {
            lru_cache_append_link(self, link);
            Py_DECREF(key);
            Py_DECREF(result);
            return NULL;
        }
        else {
            Py_DECREF(popresult);
            /* Keep a reference to the old key and old result to
               prevent their ref counts from going to zero during the
               update. That will prevent potentially arbitrary object
               clean-up code (i.e. __del__) from running while we're
               still adjusting the links. */
            oldkey = link->key;
            oldresult = link->result;

            link->hash = hash;
            link->key = key;
            link->result = result;
            if (_PyDict_SetItem_KnownHash(self->cache, key, (PyObject *)link,
                                          hash) < 0) {
                Py_DECREF(link);
                Py_DECREF(oldkey);
                Py_DECREF(oldresult);
                return NULL;
            }
            lru_cache_append_link(self, link);
            Py_INCREF(result); /* for return */
            Py_DECREF(oldkey);
            Py_DECREF(oldresult);
        }
    } else {
        /* Put result in a new link at the front of the queue. */
        link = (lru_list_elem *)PyObject_GC_New(lru_list_elem,
                                                &lru_list_elem_type);
        if (link == NULL) {
            Py_DECREF(key);
            Py_DECREF(result);
            return NULL;
        }

        link->hash = hash;
        link->key = key;
        link->result = result;
        _PyObject_GC_TRACK(link);
        if (_PyDict_SetItem_KnownHash(self->cache, key, (PyObject *)link,
                                      hash) < 0) {
            Py_DECREF(link);
            return NULL;
        }
        lru_cache_append_link(self, link);
        Py_INCREF(result); /* for return */
        self->full = (PyDict_Size(self->cache) >= self->maxsize);
    }
    self->misses++;
    return result;
}

static PyObject *
lru_cache_new(PyTypeObject *type, PyObject *args, PyObject *kw)
{
    PyObject *func, *maxsize_O, *cache_info_type, *cachedict;
    int typed;
    lru_cache_object *obj;
    Py_ssize_t maxsize;
    PyObject *(*wrapper)(lru_cache_object *, PyObject *, PyObject *);
    static char *keywords[] = {"user_function", "maxsize", "typed",
                               "cache_info_type", NULL};

    if (!PyArg_ParseTupleAndKeywords(args, kw, "OOpO:lru_cache", keywords,
                                     &func, &maxsize_O, &typed,
                                     &cache_info_type)) {
        return NULL;
    }

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

    /* select the caching function, and make/inc maxsize_O */
    if (maxsize_O == Py_None) {
        wrapper = infinite_lru_cache_wrapper;
        /* use this only to initialize lru_cache_object attribute maxsize */
        maxsize = -1;
    } else if (PyIndex_Check(maxsize_O)) {
        maxsize = PyNumber_AsSsize_t(maxsize_O, PyExc_OverflowError);
        if (maxsize == -1 && PyErr_Occurred())
            return NULL;
        if (maxsize == 0)
            wrapper = uncached_lru_cache_wrapper;
        else
            wrapper = bounded_lru_cache_wrapper;
    } else {
        PyErr_SetString(PyExc_TypeError, "maxsize should be integer or None");
        return NULL;
    }

    if (!(cachedict = PyDict_New()))
        return NULL;

    obj = (lru_cache_object *)type->tp_alloc(type, 0);
    if (obj == NULL) {
        Py_DECREF(cachedict);
        return NULL;
    }

    obj->cache = cachedict;
    obj->root.prev = &obj->root;