#include "Python.h"

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

#include "pycore_dict.h" // _PyDict_GetItem_KnownHash()

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

#include "pycore_moduleobject.h" // _PyModule_GetState()

#include "pycore_typeobject.h" // _PyType_GetModuleState()

#include <stddef.h>

typedef struct {

PyTypeObject *deque_type;

PyTypeObject *defdict_type;

PyTypeObject *dequeiter_type;

PyTypeObject *dequereviter_type;

PyTypeObject *tuplegetter_type;

} collections_state;

static inline collections_state *

get_module_state(PyObject *mod)

{

void *state = _PyModule_GetState(mod);

assert(state != NULL);

return (collections_state *)state;

}

static inline collections_state *

get_module_state_by_cls(PyTypeObject *cls)

{

void *state = _PyType_GetModuleState(cls);

assert(state != NULL);

return (collections_state *)state;

}

static struct PyModuleDef _collectionsmodule;

static inline collections_state *

find_module_state_by_def(PyTypeObject *type)

{

PyObject *mod = PyType_GetModuleByDef(type, &_collectionsmodule);

assert(mod != NULL);

return get_module_state(mod);

}

/*[clinic input]

module _collections

class _tuplegetter "_tuplegetterobject *" "clinic_state()->tuplegetter_type"

class _collections.deque "dequeobject *" "clinic_state()->deque_type"

[clinic start generated code]*/

/*[clinic end generated code: output=da39a3ee5e6b4b0d input=a033cc2a8476b3f1]*/

typedef struct dequeobject dequeobject;

/* We can safely assume type to be the defining class,

* since tuplegetter is not a base type */

#define clinic_state() (get_module_state_by_cls(type))

#include "clinic/_collectionsmodule.c.h"

#undef clinic_state

/*[python input]

class dequeobject_converter(self_converter):

type = "dequeobject *"

[python start generated code]*/

/*[python end generated code: output=da39a3ee5e6b4b0d input=b6ae4a3ff852be2f]*/

/* collections module implementation of a deque() datatype

Written and maintained by Raymond D. Hettinger <python@rcn.com>

*/

/* The block length may be set to any number over 1. Larger numbers

* reduce the number of calls to the memory allocator, give faster

* indexing and rotation, and reduce the link to data overhead ratio.

* Making the block length a power of two speeds-up the modulo

* and division calculations in deque_item() and deque_ass_item().

*/

#define BLOCKLEN 64

#define CENTER ((BLOCKLEN - 1) / 2)

#define MAXFREEBLOCKS 16

/* Data for deque objects is stored in a doubly-linked list of fixed

* length blocks. This assures that appends or pops never move any

* other data elements besides the one being appended or popped.

*

* Another advantage is that it completely avoids use of realloc(),

* resulting in more predictable performance.

*

* Textbook implementations of doubly-linked lists store one datum

* per link, but that gives them a 200% memory overhead (a prev and

* next link for each datum) and it costs one malloc() call per data

* element. By using fixed-length blocks, the link to data ratio is

* significantly improved and there are proportionally fewer calls

* to malloc() and free(). The data blocks of consecutive pointers

* also improve cache locality.

*

* The list of blocks is never empty, so d.leftblock and d.rightblock

* are never equal to NULL. The list is not circular.

*

* A deque d's first element is at d.leftblock[leftindex]

* and its last element is at d.rightblock[rightindex].

*

* Unlike Python slice indices, these indices are inclusive on both

* ends. This makes the algorithms for left and right operations

* more symmetrical and it simplifies the design.

*

* The indices, d.leftindex and d.rightindex are always in the range:

* 0 <= index < BLOCKLEN

*

* And their exact relationship is:

* (d.leftindex + d.len - 1) % BLOCKLEN == d.rightindex

*

* Whenever d.leftblock == d.rightblock, then:

* d.leftindex + d.len - 1 == d.rightindex

*

* However, when d.leftblock != d.rightblock, the d.leftindex and

* d.rightindex become indices into distinct blocks and either may

* be larger than the other.

*

* Empty deques have:

* d.len == 0

* d.leftblock == d.rightblock

* d.leftindex == CENTER + 1

* d.rightindex == CENTER

*

* Checking for d.len == 0 is the intended way to see whether d is empty.

*/

typedef struct BLOCK {

struct BLOCK *leftlink;

PyObject *data[BLOCKLEN];

struct BLOCK *rightlink;

} block;

struct dequeobject {

PyObject_VAR_HEAD

block *leftblock;

block *rightblock;

Py_ssize_t leftindex; /* 0 <= leftindex < BLOCKLEN */

Py_ssize_t rightindex; /* 0 <= rightindex < BLOCKLEN */

size_t state; /* incremented whenever the indices move */

Py_ssize_t maxlen; /* maxlen is -1 for unbounded deques */

Py_ssize_t numfreeblocks;

block *freeblocks[MAXFREEBLOCKS];

PyObject *weakreflist;

};

/* For debug builds, add error checking to track the endpoints

* in the chain of links. The goal is to make sure that link

* assignments only take place at endpoints so that links already

* in use do not get overwritten.

*

* CHECK_END should happen before each assignment to a block's link field.

* MARK_END should happen whenever a link field becomes a new endpoint.

* This happens when new blocks are added or whenever an existing

* block is freed leaving another existing block as the new endpoint.

*/

#ifndef NDEBUG

#define MARK_END(link) link = NULL;

#define CHECK_END(link) assert(link == NULL);

#define CHECK_NOT_END(link) assert(link != NULL);

#else

#define MARK_END(link)

#define CHECK_END(link)

#define CHECK_NOT_END(link)

#endif

/* A simple freelisting scheme is used to minimize calls to the memory

allocator. It accommodates common use cases where new blocks are being

added at about the same rate as old blocks are being freed.

*/

static inline block *

newblock(dequeobject *deque) {

block *b;

if (deque->numfreeblocks) {

deque->numfreeblocks--;

return deque->freeblocks[deque->numfreeblocks];

}

b = PyMem_Malloc(sizeof(block));

if (b != NULL) {

return b;

}

PyErr_NoMemory();

return NULL;

}

static inline void

freeblock(dequeobject *deque, block *b)

{

if (deque->numfreeblocks < MAXFREEBLOCKS) {

deque->freeblocks[deque->numfreeblocks] = b;

deque->numfreeblocks++;

} else {

PyMem_Free(b);

}

}

static PyObject *

deque_new(PyTypeObject *type, PyObject *args, PyObject *kwds)

{

dequeobject *deque;

block *b;

/* create dequeobject structure */

deque = (dequeobject *)type->tp_alloc(type, 0);

if (deque == NULL)

return NULL;

b = newblock(deque);

if (b == NULL) {

Py_DECREF(deque);

return NULL;

}

MARK_END(b->leftlink);

MARK_END(b->rightlink);

assert(BLOCKLEN >= 2);

Py_SET_SIZE(deque, 0);

deque->leftblock = b;

deque->rightblock = b;

deque->leftindex = CENTER + 1;

deque->rightindex = CENTER;

deque->state = 0;

deque->maxlen = -1;

deque->numfreeblocks = 0;

deque->weakreflist = NULL;

return (PyObject *)deque;

}

/*[clinic input]

_collections.deque.pop as deque_pop

deque: dequeobject

Remove and return the rightmost element.

[clinic start generated code]*/

static PyObject *

deque_pop_impl(dequeobject *deque)

/*[clinic end generated code: output=2e5f7890c4251f07 input=eb6e6d020f877dec]*/

{

PyObject *item;

block *prevblock;

if (Py_SIZE(deque) == 0) {

PyErr_SetString(PyExc_IndexError, "pop from an empty deque");

return NULL;

}

item = deque->rightblock->data[deque->rightindex];

deque->rightindex--;

Py_SET_SIZE(deque, Py_SIZE(deque) - 1);

deque->state++;

if (deque->rightindex < 0) {

if (Py_SIZE(deque)) {

prevblock = deque->rightblock->leftlink;

assert(deque->leftblock != deque->rightblock);

freeblock(deque, deque->rightblock);

CHECK_NOT_END(prevblock);

MARK_END(prevblock->rightlink);

deque->rightblock = prevblock;

deque->rightindex = BLOCKLEN - 1;

} else {

assert(deque->leftblock == deque->rightblock);

assert(deque->leftindex == deque->rightindex+1);

/* re-center instead of freeing a block */

deque->leftindex = CENTER + 1;

deque->rightindex = CENTER;

}

}

return item;

}

/*[clinic input]

_collections.deque.popleft as deque_popleft

deque: dequeobject

Remove and return the leftmost element.

[clinic start generated code]*/

static PyObject *

deque_popleft_impl(dequeobject *deque)

/*[clinic end generated code: output=62b154897097ff68 input=acb41b9af50a9d9b]*/

{

PyObject *item;

block *prevblock;

if (Py_SIZE(deque) == 0) {

PyErr_SetString(PyExc_IndexError, "pop from an empty deque");

return NULL;

}

assert(deque->leftblock != NULL);

item = deque->leftblock->data[deque->leftindex];

deque->leftindex++;

Py_SET_SIZE(deque, Py_SIZE(deque) - 1);

deque->state++;

if (deque->leftindex == BLOCKLEN) {

if (Py_SIZE(deque)) {

assert(deque->leftblock != deque->rightblock);

prevblock = deque->leftblock->rightlink;

freeblock(deque, deque->leftblock);

CHECK_NOT_END(prevblock);

MARK_END(prevblock->leftlink);

deque->leftblock = prevblock;

deque->leftindex = 0;

} else {

assert(deque->leftblock == deque->rightblock);

assert(deque->leftindex == deque->rightindex+1);

/* re-center instead of freeing a block */

deque->leftindex = CENTER + 1;

deque->rightindex = CENTER;

}

}

return item;

}

/* The deque's size limit is d.maxlen. The limit can be zero or positive.

* If there is no limit, then d.maxlen == -1.

*

* After an item is added to a deque, we check to see if the size has

* grown past the limit. If it has, we get the size back down to the limit

* by popping an item off of the opposite end. The methods that can

* trigger this are append(), appendleft(), extend(), and extendleft().

*

* The macro to check whether a deque needs to be trimmed uses a single

* unsigned test that returns true whenever 0 <= maxlen < Py_SIZE(deque).

*/

#define NEEDS_TRIM(deque, maxlen) ((size_t)(maxlen) < (size_t)(Py_SIZE(deque)))

static inline int

deque_append_internal(dequeobject *deque, PyObject *item, Py_ssize_t maxlen)

{

if (deque->rightindex == BLOCKLEN - 1) {

block *b = newblock(deque);

if (b == NULL)

return -1;

b->leftlink = deque->rightblock;

CHECK_END(deque->rightblock->rightlink);

deque->rightblock->rightlink = b;

deque->rightblock = b;

MARK_END(b->rightlink);

deque->rightindex = -1;

}

Py_SET_SIZE(deque, Py_SIZE(deque) + 1);

deque->rightindex++;

deque->rightblock->data[deque->rightindex] = item;

if (NEEDS_TRIM(deque, maxlen)) {

PyObject *olditem = deque_popleft_impl(deque);

Py_DECREF(olditem);

} else {

deque->state++;

}

return 0;

}

/*[clinic input]

_collections.deque.append as deque_append

deque: dequeobject

item: object

/

Add an element to the right side of the deque.

[clinic start generated code]*/

static PyObject *

deque_append(dequeobject *deque, PyObject *item)

/*[clinic end generated code: output=507b13efc4853ecc input=f112b83c380528e3]*/

{

if (deque_append_internal(deque, Py_NewRef(item), deque->maxlen) < 0)

return NULL;

Py_RETURN_NONE;

}

static inline int

deque_appendleft_internal(dequeobject *deque, PyObject *item, Py_ssize_t maxlen)

{

if (deque->leftindex == 0) {

block *b = newblock(deque);

if (b == NULL)

return -1;

b->rightlink = deque->leftblock;

CHECK_END(deque->leftblock->leftlink);

deque->leftblock->leftlink = b;

deque->leftblock = b;

MARK_END(b->leftlink);

deque->leftindex = BLOCKLEN;

}

Py_SET_SIZE(deque, Py_SIZE(deque) + 1);

deque->leftindex--;

deque->leftblock->data[deque->leftindex] = item;

if (NEEDS_TRIM(deque, deque->maxlen)) {

PyObject *olditem = deque_pop_impl(deque);

Py_DECREF(olditem);

} else {

deque->state++;

}

return 0;

}

/*[clinic input]

_collections.deque.appendleft as deque_appendleft

deque: dequeobject

item: object

/

Add an element to the left side of the deque.

[clinic start generated code]*/

static PyObject *

deque_appendleft(dequeobject *deque, PyObject *item)

/*[clinic end generated code: output=de0335a64800ffd8 input=bbdaa60a3e956062]*/

{

if (deque_appendleft_internal(deque, Py_NewRef(item), deque->maxlen) < 0)

return NULL;

Py_RETURN_NONE;

}

static PyObject*

finalize_iterator(PyObject *it)

{

if (PyErr_Occurred()) {

if (PyErr_ExceptionMatches(PyExc_StopIteration))

PyErr_Clear();

else {

Py_DECREF(it);

return NULL;

}

}

Py_DECREF(it);

Py_RETURN_NONE;

}

/* Run an iterator to exhaustion. Shortcut for

the extend/extendleft methods when maxlen == 0. */

static PyObject*

consume_iterator(PyObject *it)

{

PyObject *(*iternext)(PyObject *);

PyObject *item;

iternext = *Py_TYPE(it)->tp_iternext;

while ((item = iternext(it)) != NULL) {

Py_DECREF(item);

}

return finalize_iterator(it);

}

/*[clinic input]

_collections.deque.extend as deque_extend

deque: dequeobject

iterable: object

/

Extend the right side of the deque with elements from the iterable.

[clinic start generated code]*/

static PyObject *

deque_extend(dequeobject *deque, PyObject *iterable)

/*[clinic end generated code: output=a3a6e74d17063f8d input=cfebfd34d5383339]*/

{

PyObject *it, *item;

PyObject *(*iternext)(PyObject *);

Py_ssize_t maxlen = deque->maxlen;

/* Handle case where id(deque) == id(iterable) */

if ((PyObject *)deque == iterable) {

PyObject *result;

PyObject *s = PySequence_List(iterable);

if (s == NULL)

return NULL;

result = deque_extend(deque, s);

Py_DECREF(s);

return result;

}

it = PyObject_GetIter(iterable);

if (it == NULL)

return NULL;

if (maxlen == 0)

return consume_iterator(it);

/* Space saving heuristic. Start filling from the left */

if (Py_SIZE(deque) == 0) {

assert(deque->leftblock == deque->rightblock);

assert(deque->leftindex == deque->rightindex+1);

deque->leftindex = 1;

deque->rightindex = 0;

}

iternext = *Py_TYPE(it)->tp_iternext;

while ((item = iternext(it)) != NULL) {

if (deque_append_internal(deque, item, maxlen) == -1) {

Py_DECREF(item);

Py_DECREF(it);

return NULL;

}

}

return finalize_iterator(it);

}

/*[clinic input]

_collections.deque.extendleft as deque_extendleft

deque: dequeobject

iterable: object

/

Extend the left side of the deque with elements from the iterable.

[clinic start generated code]*/

static PyObject *

deque_extendleft(dequeobject *deque, PyObject *iterable)

/*[clinic end generated code: output=2dba946c50498c67 input=f4820e695a6f9416]*/

{

PyObject *it, *item;

PyObject *(*iternext)(PyObject *);

Py_ssize_t maxlen = deque->maxlen;

/* Handle case where id(deque) == id(iterable) */

if ((PyObject *)deque == iterable) {

PyObject *result;

PyObject *s = PySequence_List(iterable);

if (s == NULL)

return NULL;

result = deque_extendleft(deque, s);

Py_DECREF(s);

return result;

}

it = PyObject_GetIter(iterable);

if (it == NULL)

return NULL;

if (maxlen == 0)

return consume_iterator(it);

/* Space saving heuristic. Start filling from the right */

if (Py_SIZE(deque) == 0) {

assert(deque->leftblock == deque->rightblock);

assert(deque->leftindex == deque->rightindex+1);

deque->leftindex = BLOCKLEN - 1;

deque->rightindex = BLOCKLEN - 2;

}

iternext = *Py_TYPE(it)->tp_iternext;

while ((item = iternext(it)) != NULL) {

if (deque_appendleft_internal(deque, item, maxlen) == -1) {

Py_DECREF(item);

Py_DECREF(it);

return NULL;

}

}

return finalize_iterator(it);

}

static PyObject *

deque_inplace_concat(dequeobject *deque, PyObject *other)

{

PyObject *result;

result = deque_extend(deque, other);

if (result == NULL)

return result;

Py_INCREF(deque);

Py_DECREF(result);

return (PyObject *)deque;

}

/*[clinic input]

_collections.deque.copy as deque_copy

deque: dequeobject

Return a shallow copy of a deque.

[clinic start generated code]*/

static PyObject *

deque_copy_impl(dequeobject *deque)

/*[clinic end generated code: output=6409b3d1ad2898b5 input=0e22f138bc1fcbee]*/

{

PyObject *result;

dequeobject *old_deque = (dequeobject *)deque;

collections_state *state = find_module_state_by_def(Py_TYPE(deque));

if (Py_IS_TYPE(deque, state->deque_type)) {

dequeobject *new_deque;

PyObject *rv;

new_deque = (dequeobject *)deque_new(state->deque_type,

(PyObject *)NULL, (PyObject *)NULL);

if (new_deque == NULL)

return NULL;

new_deque->maxlen = old_deque->maxlen;

/* Fast path for the deque_repeat() common case where len(deque) == 1 */

if (Py_SIZE(deque) == 1) {

PyObject *item = old_deque->leftblock->data[old_deque->leftindex];

rv = deque_append(new_deque, item);

} else {

rv = deque_extend(new_deque, (PyObject *)deque);

}

if (rv != NULL) {

Py_DECREF(rv);

return (PyObject *)new_deque;

}

Py_DECREF(new_deque);

return NULL;

}

if (old_deque->maxlen < 0)

result = PyObject_CallOneArg((PyObject *)(Py_TYPE(deque)),

(PyObject *)deque);

else

result = PyObject_CallFunction((PyObject *)(Py_TYPE(deque)), "Oi",

deque, old_deque->maxlen, NULL);

if (result != NULL && !PyObject_TypeCheck(result, state->deque_type)) {

PyErr_Format(PyExc_TypeError,

"%.200s() must return a deque, not %.200s",

Py_TYPE(deque)->tp_name, Py_TYPE(result)->tp_name);

Py_DECREF(result);

return NULL;

}

return result;

}

/*[clinic input]

_collections.deque.__copy__ as deque___copy__ = _collections.deque.copy

Return a shallow copy of a deque.

[clinic start generated code]*/

static PyObject *

deque___copy___impl(dequeobject *deque)

/*[clinic end generated code: output=7c5821504342bf23 input=fce05df783e7912b]*/

{

return deque_copy_impl(deque);

}

static PyObject *

deque_concat(dequeobject *deque, PyObject *other)

{

PyObject *new_deque, *result;

int rv;

collections_state *state = find_module_state_by_def(Py_TYPE(deque));

rv = PyObject_IsInstance(other, (PyObject *)state->deque_type);

if (rv <= 0) {

if (rv == 0) {

PyErr_Format(PyExc_TypeError,

"can only concatenate deque (not \"%.200s\") to deque",

Py_TYPE(other)->tp_name);

}

return NULL;

}

new_deque = deque_copy_impl(deque);

if (new_deque == NULL)

return NULL;

result = deque_extend((dequeobject *)new_deque, other);

if (result == NULL) {

Py_DECREF(new_deque);

return NULL;

}

Py_DECREF(result);

return new_deque;

}

static int

deque_clear(dequeobject *deque)

{

block *b;

block *prevblock;

block *leftblock;

Py_ssize_t leftindex;

Py_ssize_t n, m;

PyObject *item;

PyObject **itemptr, **limit;

if (Py_SIZE(deque) == 0)

return 0;

/* During the process of clearing a deque, decrefs can cause the

deque to mutate. To avoid fatal confusion, we have to make the

deque empty before clearing the blocks and never refer to

anything via deque->ref while clearing. (This is the same

technique used for clearing lists, sets, and dicts.)

Making the deque empty requires allocating a new empty block. In

the unlikely event that memory is full, we fall back to an

alternate method that doesn't require a new block. Repeating

pops in a while-loop is slower, possibly re-entrant (and a clever

adversary could cause it to never terminate).

*/

b = newblock(deque);

if (b == NULL) {

PyErr_Clear();

goto alternate_method;

}

/* Remember the old size, leftblock, and leftindex */

n = Py_SIZE(deque);

leftblock = deque->leftblock;

leftindex = deque->leftindex;

/* Set the deque to be empty using the newly allocated block */

MARK_END(b->leftlink);

MARK_END(b->rightlink);

Py_SET_SIZE(deque, 0);

deque->leftblock = b;

deque->rightblock = b;

deque->leftindex = CENTER + 1;

deque->rightindex = CENTER;

deque->state++;

/* Now the old size, leftblock, and leftindex are disconnected from

the empty deque and we can use them to decref the pointers.

*/

m = (BLOCKLEN - leftindex > n) ? n : BLOCKLEN - leftindex;

itemptr = &leftblock->data[leftindex];

limit = itemptr + m;

n -= m;

while (1) {

if (itemptr == limit) {

if (n == 0)

break;

CHECK_NOT_END(leftblock->rightlink);

prevblock = leftblock;

leftblock = leftblock->rightlink;

m = (n > BLOCKLEN) ? BLOCKLEN : n;

itemptr = leftblock->data;

limit = itemptr + m;

n -= m;

freeblock(deque, prevblock);

}

item = *(itemptr++);

Py_DECREF(item);

}

CHECK_END(leftblock->rightlink);

freeblock(deque, leftblock);

return 0;

alternate_method:

while (Py_SIZE(deque)) {

item = deque_pop_impl(deque);

assert (item != NULL);

Py_DECREF(item);

}

return 0;

}

/*[clinic input]

_collections.deque.clear as deque_clearmethod

deque: dequeobject

Remove all elements from the deque.

[clinic start generated code]*/

static PyObject *

deque_clearmethod_impl(dequeobject *deque)

/*[clinic end generated code: output=79b2513e097615c1 input=20488eb932f89f9e]*/

{

deque_clear(deque);

Py_RETURN_NONE;

}

static PyObject *

deque_inplace_repeat(dequeobject *deque, Py_ssize_t n)

{

Py_ssize_t i, m, size;

PyObject *seq;

PyObject *rv;

size = Py_SIZE(deque);

if (size == 0 || n == 1) {

return Py_NewRef(deque);

}

if (n <= 0) {

deque_clear(deque);

return Py_NewRef(deque);

}

if (size == 1) {

/* common case, repeating a single element */

PyObject *item = deque->leftblock->data[deque->leftindex];

if (deque->maxlen >= 0 && n > deque->maxlen)

n = deque->maxlen;

deque->state++;

for (i = 0 ; i < n-1 ; ) {

if (deque->rightindex == BLOCKLEN - 1) {

block *b = newblock(deque);

if (b == NULL) {

Py_SET_SIZE(deque, Py_SIZE(deque) + i);

return NULL;

}

b->leftlink = deque->rightblock;

CHECK_END(deque->rightblock->rightlink);

deque->rightblock->rightlink = b;

deque->rightblock = b;

MARK_END(b->rightlink);

deque->rightindex = -1;

}

m = n - 1 - i;

if (m > BLOCKLEN - 1 - deque->rightindex)

m = BLOCKLEN - 1 - deque->rightindex;

i += m;

while (m--) {

deque->rightindex++;

deque->rightblock->data[deque->rightindex] = Py_NewRef(item);

}

}

Py_SET_SIZE(deque, Py_SIZE(deque) + i);

return Py_NewRef(deque);

}

if ((size_t)size > PY_SSIZE_T_MAX / (size_t)n) {

return PyErr_NoMemory();

}

seq = PySequence_List((PyObject *)deque);

if (seq == NULL)

return seq;

/* Reduce the number of repetitions when maxlen would be exceeded */

if (deque->maxlen >= 0 && n * size > deque->maxlen)

n = (deque->maxlen + size - 1) / size;

for (i = 0 ; i < n-1 ; i++) {

rv = deque_extend(deque, seq);

if (rv == NULL) {

Py_DECREF(seq);

return NULL;

}

Py_DECREF(rv);

}

Py_INCREF(deque);

Py_DECREF(seq);

return (PyObject *)deque;

}

static PyObject *

deque_repeat(dequeobject *deque, Py_ssize_t n)

{

dequeobject *new_deque;

PyObject *rv;

new_deque = (dequeobject *)deque_copy_impl(deque);

if (new_deque == NULL)

return NULL;

rv = deque_inplace_repeat(new_deque, n);

Py_DECREF(new_deque);

return rv;

}

/* The rotate() method is part of the public API and is used internally

as a primitive for other methods.

Rotation by 1 or -1 is a common case, so any optimizations for high

volume rotations should take care not to penalize the common case.

Conceptually, a rotate by one is equivalent to a pop on one side and an

append on the other. However, a pop/append pair is unnecessarily slow

because it requires an incref/decref pair for an object located randomly

in memory. It is better to just move the object pointer from one block

to the next without changing the reference count.

When moving batches of pointers, it is tempting to use memcpy() but that

proved to be slower than a simple loop for a variety of reasons.

Memcpy() cannot know in advance that we're copying pointers instead of

bytes, that the source and destination are pointer aligned and

non-overlapping, that moving just one pointer is a common case, that we

never need to move more than BLOCKLEN pointers, and that at least one

pointer is always moved.

For high volume rotations, newblock() and freeblock() are never called

more than once. Previously emptied blocks are immediately reused as a

destination block. If a block is left-over at the end, it is freed.

*/

static int

_deque_rotate(dequeobject *deque, Py_ssize_t n)

{

block *b = NULL;

block *leftblock = deque->leftblock;

block *rightblock = deque->rightblock;

Py_ssize_t leftindex = deque->leftindex;

Py_ssize_t rightindex = deque->rightindex;

Py_ssize_t len=Py_SIZE(deque), halflen=len>>1;

int rv = -1;

if (len <= 1)

return 0;

if (n > halflen || n < -halflen) {

n %= len;

if (n > halflen)

n -= len;

else if (n < -halflen)

n += len;

}

assert(len > 1);

assert(-halflen <= n && n <= halflen);

deque->state++;

while (n > 0) {

if (leftindex == 0) {

if (b == NULL) {

b = newblock(deque);

if (b == NULL)

goto done;

}

b->rightlink = leftblock;

CHECK_END(leftblock->leftlink);

leftblock->leftlink = b;

leftblock = b;

MARK_END(b->leftlink);

leftindex = BLOCKLEN;

b = NULL;

}

assert(leftindex > 0);

{

PyObject **src, **dest;

Py_ssize_t m = n;

if (m > rightindex + 1)

m = rightindex + 1;

if (m > leftindex)

m = leftindex;

assert (m > 0 && m <= len);

rightindex -= m;

leftindex -= m;

src = &rightblock->data[rightindex + 1];

dest = &leftblock->data[leftindex];

n -= m;

do {

*(dest++) = *(src++);

} while (--m);

}

if (rightindex < 0) {

assert(leftblock != rightblock);

assert(b == NULL);

b = rightblock;

CHECK_NOT_END(rightblock->leftlink);

rightblock = rightblock->leftlink;

MARK_END(rightblock->rightlink);

rightindex = BLOCKLEN - 1;

}

}

while (n < 0) {

if (rightindex == BLOCKLEN - 1) {

if (b == NULL) {

b = newblock(deque);

if (b == NULL)

goto done;

}

b->leftlink = rightblock;

CHECK_END(rightblock->rightlink);

rightblock->rightlink = b;

rightblock = b;

MARK_END(b->rightlink);

rightindex = -1;

b = NULL;

}

assert (rightindex < BLOCKLEN - 1);

{

PyObject **src, **dest;

Py_ssize_t m = -n;

if (m > BLOCKLEN - leftindex)

m = BLOCKLEN - leftindex;

if (m > BLOCKLEN - 1 - rightindex)

m = BLOCKLEN - 1 - rightindex;

assert (m > 0 && m <= len);

src = &leftblock->data[leftindex];

dest = &rightblock->data[rightindex + 1];

leftindex += m;

rightindex += m;

n += m;

do {

*(dest++) = *(src++);

} while (--m);

}

if (leftindex == BLOCKLEN) {

assert(leftblock != rightblock);

assert(b == NULL);

b = leftblock;

CHECK_NOT_END(leftblock->rightlink);

leftblock = leftblock->rightlink;

MARK_END(leftblock->leftlink);

leftindex = 0;

}

}