/Modules/_collectionsmodule.c

   1#include "Python.h"
   2#include "structmember.h"
   3
   4/* collections module implementation of a deque() datatype
   5   Written and maintained by Raymond D. Hettinger <python@rcn.com>
   6   Copyright (c) 2004 Python Software Foundation.
   7   All rights reserved.
   8*/
   9
  10/* The block length may be set to any number over 1.  Larger numbers
  11 * reduce the number of calls to the memory allocator but take more
  12 * memory.  Ideally, BLOCKLEN should be set with an eye to the
  13 * length of a cache line.
  14 */
  15
  16#define BLOCKLEN 62
  17#define CENTER ((BLOCKLEN - 1) / 2)
  18
  19/* A `dequeobject` is composed of a doubly-linked list of `block` nodes.
  20 * This list is not circular (the leftmost block has leftlink==NULL,
  21 * and the rightmost block has rightlink==NULL).  A deque d's first
  22 * element is at d.leftblock[leftindex] and its last element is at
  23 * d.rightblock[rightindex]; note that, unlike as for Python slice
  24 * indices, these indices are inclusive on both ends.  By being inclusive
  25 * on both ends, algorithms for left and right operations become
  26 * symmetrical which simplifies the design.
  27 *
  28 * The list of blocks is never empty, so d.leftblock and d.rightblock
  29 * are never equal to NULL.
  30 *
  31 * The indices, d.leftindex and d.rightindex are always in the range
  32 *     0 <= index < BLOCKLEN.
  33 * Their exact relationship is:
  34 *     (d.leftindex + d.len - 1) % BLOCKLEN == d.rightindex.
  35 *
  36 * Empty deques have d.len == 0; d.leftblock==d.rightblock;
  37 * d.leftindex == CENTER+1; and d.rightindex == CENTER.
  38 * Checking for d.len == 0 is the intended way to see whether d is empty.
  39 *
  40 * Whenever d.leftblock == d.rightblock,
  41 *     d.leftindex + d.len - 1 == d.rightindex.
  42 *
  43 * However, when d.leftblock != d.rightblock, d.leftindex and d.rightindex
  44 * become indices into distinct blocks and either may be larger than the
  45 * other.
  46 */
  47
  48typedef struct BLOCK {
  49	struct BLOCK *leftlink;
  50	struct BLOCK *rightlink;
  51	PyObject *data[BLOCKLEN];
  52} block;
  53
  54#define MAXFREEBLOCKS 10
  55static Py_ssize_t numfreeblocks = 0;
  56static block *freeblocks[MAXFREEBLOCKS];
  57
  58static block *
  59newblock(block *leftlink, block *rightlink, Py_ssize_t len) {
  60	block *b;
  61	/* To prevent len from overflowing PY_SSIZE_T_MAX on 64-bit machines, we
  62	 * refuse to allocate new blocks if the current len is dangerously
  63	 * close.  There is some extra margin to prevent spurious arithmetic
  64	 * overflows at various places.  The following check ensures that
  65	 * the blocks allocated to the deque, in the worst case, can only
  66	 * have PY_SSIZE_T_MAX-2 entries in total.
  67	 */
  68	if (len >= PY_SSIZE_T_MAX - 2*BLOCKLEN) {
  69		PyErr_SetString(PyExc_OverflowError,
  70				"cannot add more blocks to the deque");
  71		return NULL;
  72	}
  73	if (numfreeblocks) {
  74		numfreeblocks -= 1;
  75		b = freeblocks[numfreeblocks];
  76	} else {
  77		b = PyMem_Malloc(sizeof(block));
  78		if (b == NULL) {
  79			PyErr_NoMemory();
  80			return NULL;
  81		}
  82	}
  83	b->leftlink = leftlink;
  84	b->rightlink = rightlink;
  85	return b;
  86}
  87
  88static void
  89freeblock(block *b)
  90{
  91	if (numfreeblocks < MAXFREEBLOCKS) {
  92		freeblocks[numfreeblocks] = b;
  93		numfreeblocks++;
  94	} else {
  95		PyMem_Free(b);
  96	}
  97}
  98
  99typedef struct {
 100	PyObject_HEAD
 101	block *leftblock;
 102	block *rightblock;
 103	Py_ssize_t leftindex;	/* in range(BLOCKLEN) */
 104	Py_ssize_t rightindex;	/* in range(BLOCKLEN) */
 105	Py_ssize_t len;
 106	Py_ssize_t maxlen;
 107	long state;	/* incremented whenever the indices move */
 108	PyObject *weakreflist; /* List of weak references */
 109} dequeobject;
 110
 111/* The deque's size limit is d.maxlen.  The limit can be zero or positive.
 112 * If there is no limit, then d.maxlen == -1.
 113 * 
 114 * After an item is added to a deque, we check to see if the size has grown past
 115 * the limit. If it has, we get the size back down to the limit by popping an
 116 * item off of the opposite end.  The methods that can trigger this are append(),
 117 * appendleft(), extend(), and extendleft().
 118 */
 119
 120#define TRIM(d, popfunction)                               	\
 121    if (d->maxlen != -1 && d->len > d->maxlen) {              	\
 122            PyObject *rv = popfunction(d, NULL);                \
 123            assert(rv != NULL  &&  d->len <= d->maxlen);        \
 124            Py_DECREF(rv);                                      \
 125    }
 126
 127static PyTypeObject deque_type;
 128
 129static PyObject *
 130deque_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 131{
 132	dequeobject *deque;
 133	block *b;
 134
 135	/* create dequeobject structure */
 136	deque = (dequeobject *)type->tp_alloc(type, 0);
 137	if (deque == NULL)
 138		return NULL;
 139
 140	b = newblock(NULL, NULL, 0);
 141	if (b == NULL) {
 142		Py_DECREF(deque);
 143		return NULL;
 144	}
 145
 146	assert(BLOCKLEN >= 2);
 147	deque->leftblock = b;
 148	deque->rightblock = b;
 149	deque->leftindex = CENTER + 1;
 150	deque->rightindex = CENTER;
 151	deque->len = 0;
 152	deque->state = 0;
 153	deque->weakreflist = NULL;
 154	deque->maxlen = -1;
 155
 156	return (PyObject *)deque;
 157}
 158
 159static PyObject *
 160deque_pop(dequeobject *deque, PyObject *unused)
 161{
 162	PyObject *item;
 163	block *prevblock;
 164
 165	if (deque->len == 0) {
 166		PyErr_SetString(PyExc_IndexError, "pop from an empty deque");
 167		return NULL;
 168	}
 169	item = deque->rightblock->data[deque->rightindex];
 170	deque->rightindex--;
 171	deque->len--;
 172	deque->state++;
 173
 174	if (deque->rightindex == -1) {
 175		if (deque->len == 0) {
 176			assert(deque->leftblock == deque->rightblock);
 177			assert(deque->leftindex == deque->rightindex+1);
 178			/* re-center instead of freeing a block */
 179			deque->leftindex = CENTER + 1;
 180			deque->rightindex = CENTER;
 181		} else {
 182			prevblock = deque->rightblock->leftlink;
 183			assert(deque->leftblock != deque->rightblock);
 184			freeblock(deque->rightblock);
 185			prevblock->rightlink = NULL;
 186			deque->rightblock = prevblock;
 187			deque->rightindex = BLOCKLEN - 1;
 188		}
 189	}
 190	return item;
 191}
 192
 193PyDoc_STRVAR(pop_doc, "Remove and return the rightmost element.");
 194
 195static PyObject *
 196deque_popleft(dequeobject *deque, PyObject *unused)
 197{
 198	PyObject *item;
 199	block *prevblock;
 200
 201	if (deque->len == 0) {
 202		PyErr_SetString(PyExc_IndexError, "pop from an empty deque");
 203		return NULL;
 204	}
 205	assert(deque->leftblock != NULL);
 206	item = deque->leftblock->data[deque->leftindex];
 207	deque->leftindex++;
 208	deque->len--;
 209	deque->state++;
 210
 211	if (deque->leftindex == BLOCKLEN) {
 212		if (deque->len == 0) {
 213			assert(deque->leftblock == deque->rightblock);
 214			assert(deque->leftindex == deque->rightindex+1);
 215			/* re-center instead of freeing a block */
 216			deque->leftindex = CENTER + 1;
 217			deque->rightindex = CENTER;
 218		} else {
 219			assert(deque->leftblock != deque->rightblock);
 220			prevblock = deque->leftblock->rightlink;
 221			freeblock(deque->leftblock);
 222			assert(prevblock != NULL);
 223			prevblock->leftlink = NULL;
 224			deque->leftblock = prevblock;
 225			deque->leftindex = 0;
 226		}
 227	}
 228	return item;
 229}
 230
 231PyDoc_STRVAR(popleft_doc, "Remove and return the leftmost element.");
 232
 233static PyObject *
 234deque_append(dequeobject *deque, PyObject *item)
 235{
 236	deque->state++;
 237	if (deque->rightindex == BLOCKLEN-1) {
 238		block *b = newblock(deque->rightblock, NULL, deque->len);
 239		if (b == NULL)
 240			return NULL;
 241		assert(deque->rightblock->rightlink == NULL);
 242		deque->rightblock->rightlink = b;
 243		deque->rightblock = b;
 244		deque->rightindex = -1;
 245	}
 246	Py_INCREF(item);
 247	deque->len++;
 248	deque->rightindex++;
 249	deque->rightblock->data[deque->rightindex] = item;
 250	TRIM(deque, deque_popleft);
 251	Py_RETURN_NONE;
 252}
 253
 254PyDoc_STRVAR(append_doc, "Add an element to the right side of the deque.");
 255
 256static PyObject *
 257deque_appendleft(dequeobject *deque, PyObject *item)
 258{
 259	deque->state++;
 260	if (deque->leftindex == 0) {
 261		block *b = newblock(NULL, deque->leftblock, deque->len);
 262		if (b == NULL)
 263			return NULL;
 264		assert(deque->leftblock->leftlink == NULL);
 265		deque->leftblock->leftlink = b;
 266		deque->leftblock = b;
 267		deque->leftindex = BLOCKLEN;
 268	}
 269	Py_INCREF(item);
 270	deque->len++;
 271	deque->leftindex--;
 272	deque->leftblock->data[deque->leftindex] = item;
 273	TRIM(deque, deque_pop);
 274	Py_RETURN_NONE;
 275}
 276
 277PyDoc_STRVAR(appendleft_doc, "Add an element to the left side of the deque.");
 278
 279static PyObject *
 280deque_extend(dequeobject *deque, PyObject *iterable)
 281{
 282	PyObject *it, *item;
 283
 284	it = PyObject_GetIter(iterable);
 285	if (it == NULL)
 286		return NULL;
 287
 288	while ((item = PyIter_Next(it)) != NULL) {
 289		deque->state++;
 290		if (deque->rightindex == BLOCKLEN-1) {
 291			block *b = newblock(deque->rightblock, NULL,
 292					    deque->len);
 293			if (b == NULL) {
 294				Py_DECREF(item);
 295				Py_DECREF(it);
 296				return NULL;
 297			}
 298			assert(deque->rightblock->rightlink == NULL);
 299			deque->rightblock->rightlink = b;
 300			deque->rightblock = b;
 301			deque->rightindex = -1;
 302		}
 303		deque->len++;
 304		deque->rightindex++;
 305		deque->rightblock->data[deque->rightindex] = item;
 306		TRIM(deque, deque_popleft);               
 307	}
 308	Py_DECREF(it);
 309	if (PyErr_Occurred())
 310		return NULL;
 311	Py_RETURN_NONE;
 312}
 313
 314PyDoc_STRVAR(extend_doc,
 315"Extend the right side of the deque with elements from the iterable");
 316
 317static PyObject *
 318deque_extendleft(dequeobject *deque, PyObject *iterable)
 319{
 320	PyObject *it, *item;
 321
 322	it = PyObject_GetIter(iterable);
 323	if (it == NULL)
 324		return NULL;
 325
 326	while ((item = PyIter_Next(it)) != NULL) {
 327		deque->state++;
 328		if (deque->leftindex == 0) {
 329			block *b = newblock(NULL, deque->leftblock,
 330					    deque->len);
 331			if (b == NULL) {
 332				Py_DECREF(item);
 333				Py_DECREF(it);
 334				return NULL;
 335			}
 336			assert(deque->leftblock->leftlink == NULL);
 337			deque->leftblock->leftlink = b;
 338			deque->leftblock = b;
 339			deque->leftindex = BLOCKLEN;
 340		}
 341		deque->len++;
 342		deque->leftindex--;
 343		deque->leftblock->data[deque->leftindex] = item;
 344		TRIM(deque, deque_pop);               
 345	}
 346	Py_DECREF(it);
 347	if (PyErr_Occurred())
 348		return NULL;
 349	Py_RETURN_NONE;
 350}
 351
 352PyDoc_STRVAR(extendleft_doc,
 353"Extend the left side of the deque with elements from the iterable");
 354
 355static int
 356_deque_rotate(dequeobject *deque, Py_ssize_t n)
 357{
 358	Py_ssize_t i, len=deque->len, halflen=(len+1)>>1;
 359	PyObject *item, *rv;
 360
 361	if (len == 0)
 362		return 0;
 363	if (n > halflen || n < -halflen) {
 364		n %= len;
 365		if (n > halflen)
 366			n -= len;
 367		else if (n < -halflen)
 368			n += len;
 369	}
 370
 371	for (i=0 ; i<n ; i++) {
 372		item = deque_pop(deque, NULL);
 373		assert (item != NULL);
 374		rv = deque_appendleft(deque, item);
 375		Py_DECREF(item);
 376		if (rv == NULL)
 377			return -1;
 378		Py_DECREF(rv);
 379	}
 380	for (i=0 ; i>n ; i--) {
 381		item = deque_popleft(deque, NULL);
 382		assert (item != NULL);
 383		rv = deque_append(deque, item);
 384		Py_DECREF(item);
 385		if (rv == NULL)
 386			return -1;
 387		Py_DECREF(rv);
 388	}
 389	return 0;
 390}
 391
 392static PyObject *
 393deque_rotate(dequeobject *deque, PyObject *args)
 394{
 395	Py_ssize_t n=1;
 396
 397	if (!PyArg_ParseTuple(args, "|n:rotate", &n))
 398		return NULL;
 399	if (_deque_rotate(deque, n) == 0)
 400		Py_RETURN_NONE;
 401	return NULL;
 402}
 403
 404PyDoc_STRVAR(rotate_doc,
 405"Rotate the deque n steps to the right (default n=1).  If n is negative, rotates left.");
 406
 407static Py_ssize_t
 408deque_len(dequeobject *deque)
 409{
 410	return deque->len;
 411}
 412
 413static PyObject *
 414deque_remove(dequeobject *deque, PyObject *value)
 415{
 416	Py_ssize_t i, n=deque->len;
 417
 418	for (i=0 ; i<n ; i++) {
 419		PyObject *item = deque->leftblock->data[deque->leftindex];
 420		int cmp = PyObject_RichCompareBool(item, value, Py_EQ);
 421
 422		if (deque->len != n) {
 423			PyErr_SetString(PyExc_IndexError,
 424				"deque mutated during remove().");
 425			return NULL;
 426		}
 427		if (cmp > 0) {
 428			PyObject *tgt = deque_popleft(deque, NULL);
 429			assert (tgt != NULL);
 430			Py_DECREF(tgt);
 431			if (_deque_rotate(deque, i) == -1)
 432				return NULL;
 433			Py_RETURN_NONE;
 434		}
 435		else if (cmp < 0) {
 436			_deque_rotate(deque, i);
 437			return NULL;
 438		}
 439		_deque_rotate(deque, -1);
 440	}
 441	PyErr_SetString(PyExc_ValueError, "deque.remove(x): x not in deque");
 442	return NULL;
 443}
 444
 445PyDoc_STRVAR(remove_doc,
 446"D.remove(value) -- remove first occurrence of value.");
 447
 448static int
 449deque_clear(dequeobject *deque)
 450{
 451	PyObject *item;
 452
 453	while (deque->len) {
 454		item = deque_pop(deque, NULL);
 455		assert (item != NULL);
 456		Py_DECREF(item);
 457	}
 458	assert(deque->leftblock == deque->rightblock &&
 459	       deque->leftindex - 1 == deque->rightindex &&
 460	       deque->len == 0);
 461	return 0;
 462}
 463
 464static PyObject *
 465deque_item(dequeobject *deque, Py_ssize_t i)
 466{
 467	block *b;
 468	PyObject *item;
 469	Py_ssize_t n, index=i;
 470
 471	if (i < 0 || i >= deque->len) {
 472		PyErr_SetString(PyExc_IndexError,
 473				"deque index out of range");
 474		return NULL;
 475	}
 476
 477	if (i == 0) {
 478		i = deque->leftindex;
 479		b = deque->leftblock;
 480	} else if (i == deque->len - 1) {
 481		i = deque->rightindex;
 482		b = deque->rightblock;
 483	} else {
 484		i += deque->leftindex;
 485		n = i / BLOCKLEN;
 486		i %= BLOCKLEN;
 487		if (index < (deque->len >> 1)) {
 488			b = deque->leftblock;
 489			while (n--)
 490				b = b->rightlink;
 491		} else {
 492			n = (deque->leftindex + deque->len - 1) / BLOCKLEN - n;
 493			b = deque->rightblock;
 494			while (n--)
 495				b = b->leftlink;
 496		}
 497	}
 498	item = b->data[i];
 499	Py_INCREF(item);
 500	return item;
 501}
 502
 503/* delitem() implemented in terms of rotate for simplicity and reasonable
 504   performance near the end points.  If for some reason this method becomes
 505   popular, it is not hard to re-implement this using direct data movement
 506   (similar to code in list slice assignment) and achieve a two or threefold
 507   performance boost.
 508*/
 509
 510static int
 511deque_del_item(dequeobject *deque, Py_ssize_t i)
 512{
 513	PyObject *item;
 514
 515	assert (i >= 0 && i < deque->len);
 516	if (_deque_rotate(deque, -i) == -1)
 517		return -1;
 518
 519	item = deque_popleft(deque, NULL);
 520	assert (item != NULL);
 521	Py_DECREF(item);
 522
 523	return _deque_rotate(deque, i);
 524}
 525
 526static int
 527deque_ass_item(dequeobject *deque, Py_ssize_t i, PyObject *v)
 528{
 529	PyObject *old_value;
 530	block *b;
 531	Py_ssize_t n, len=deque->len, halflen=(len+1)>>1, index=i;
 532
 533	if (i < 0 || i >= len) {
 534		PyErr_SetString(PyExc_IndexError,
 535				"deque index out of range");
 536		return -1;
 537	}
 538	if (v == NULL)
 539		return deque_del_item(deque, i);
 540
 541	i += deque->leftindex;
 542	n = i / BLOCKLEN;
 543	i %= BLOCKLEN;
 544	if (index <= halflen) {
 545		b = deque->leftblock;
 546		while (n--)
 547			b = b->rightlink;
 548	} else {
 549		n = (deque->leftindex + len - 1) / BLOCKLEN - n;
 550		b = deque->rightblock;
 551		while (n--)
 552			b = b->leftlink;
 553	}
 554	Py_INCREF(v);
 555	old_value = b->data[i];
 556	b->data[i] = v;
 557	Py_DECREF(old_value);
 558	return 0;
 559}
 560
 561static PyObject *
 562deque_clearmethod(dequeobject *deque)
 563{
 564	int rv;
 565
 566	rv = deque_clear(deque);
 567	assert (rv != -1);
 568	Py_RETURN_NONE;
 569}
 570
 571PyDoc_STRVAR(clear_doc, "Remove all elements from the deque.");
 572
 573static void
 574deque_dealloc(dequeobject *deque)
 575{
 576	PyObject_GC_UnTrack(deque);
 577	if (deque->weakreflist != NULL)
 578		PyObject_ClearWeakRefs((PyObject *) deque);
 579	if (deque->leftblock != NULL) {
 580		deque_clear(deque);
 581		assert(deque->leftblock != NULL);
 582		freeblock(deque->leftblock);
 583	}
 584	deque->leftblock = NULL;
 585	deque->rightblock = NULL;
 586	Py_TYPE(deque)->tp_free(deque);
 587}
 588
 589static int
 590deque_traverse(dequeobject *deque, visitproc visit, void *arg)
 591{
 592	block *b;
 593	PyObject *item;
 594	Py_ssize_t index;
 595	Py_ssize_t indexlo = deque->leftindex;
 596
 597	for (b = deque->leftblock; b != NULL; b = b->rightlink) {
 598		const Py_ssize_t indexhi = b == deque->rightblock ?
 599					 deque->rightindex :
 600				    	 BLOCKLEN - 1;
 601
 602		for (index = indexlo; index <= indexhi; ++index) {
 603			item = b->data[index];
 604			Py_VISIT(item);
 605		}
 606		indexlo = 0;
 607	}
 608	return 0;
 609}
 610
 611static PyObject *
 612deque_copy(PyObject *deque)
 613{
 614	if (((dequeobject *)deque)->maxlen == -1)
 615		return PyObject_CallFunction((PyObject *)(Py_TYPE(deque)), "O", deque, NULL);
 616	else
 617		return PyObject_CallFunction((PyObject *)(Py_TYPE(deque)), "Oi",
 618			deque, ((dequeobject *)deque)->maxlen, NULL);
 619}
 620
 621PyDoc_STRVAR(copy_doc, "Return a shallow copy of a deque.");
 622
 623static PyObject *
 624deque_reduce(dequeobject *deque)
 625{
 626	PyObject *dict, *result, *aslist;
 627
 628	dict = PyObject_GetAttrString((PyObject *)deque, "__dict__");
 629	if (dict == NULL)
 630		PyErr_Clear();
 631	aslist = PySequence_List((PyObject *)deque);
 632	if (aslist == NULL) {
 633		Py_XDECREF(dict);
 634		return NULL;
 635	}
 636	if (dict == NULL) {
 637		if (deque->maxlen == -1)
 638			result = Py_BuildValue("O(O)", Py_TYPE(deque), aslist);
 639		else
 640			result = Py_BuildValue("O(On)", Py_TYPE(deque), aslist, deque->maxlen);
 641	} else {
 642		if (deque->maxlen == -1)
 643			result = Py_BuildValue("O(OO)O", Py_TYPE(deque), aslist, Py_None, dict);
 644		else
 645			result = Py_BuildValue("O(On)O", Py_TYPE(deque), aslist, deque->maxlen, dict);
 646	}
 647	Py_XDECREF(dict);
 648	Py_DECREF(aslist);
 649	return result;
 650}
 651
 652PyDoc_STRVAR(reduce_doc, "Return state information for pickling.");
 653
 654static PyObject *
 655deque_repr(PyObject *deque)
 656{
 657	PyObject *aslist, *result, *fmt;
 658	int i;
 659
 660	i = Py_ReprEnter(deque);
 661	if (i != 0) {
 662		if (i < 0)
 663			return NULL;
 664		return PyString_FromString("[...]");
 665	}
 666
 667	aslist = PySequence_List(deque);
 668	if (aslist == NULL) {
 669		Py_ReprLeave(deque);
 670		return NULL;
 671	}
 672	if (((dequeobject *)deque)->maxlen != -1)
 673		fmt = PyString_FromFormat("deque(%%r, maxlen=%zd)", 
 674					((dequeobject *)deque)->maxlen);
 675	else
 676		fmt = PyString_FromString("deque(%r)");  
 677	if (fmt == NULL) {
 678		Py_DECREF(aslist);
 679		Py_ReprLeave(deque);
 680		return NULL;
 681	}
 682	result = PyString_Format(fmt, aslist);
 683	Py_DECREF(fmt);
 684	Py_DECREF(aslist);
 685	Py_ReprLeave(deque);
 686	return result;
 687}
 688
 689static int
 690deque_tp_print(PyObject *deque, FILE *fp, int flags)
 691{
 692	PyObject *it, *item;
 693	char *emit = "";	/* No separator emitted on first pass */
 694	char *separator = ", ";
 695	int i;
 696
 697	i = Py_ReprEnter(deque);
 698	if (i != 0) {
 699		if (i < 0)
 700			return i;
 701		Py_BEGIN_ALLOW_THREADS
 702		fputs("[...]", fp);
 703		Py_END_ALLOW_THREADS
 704		return 0;
 705	}
 706
 707	it = PyObject_GetIter(deque);
 708	if (it == NULL)
 709		return -1;
 710
 711	Py_BEGIN_ALLOW_THREADS
 712	fputs("deque([", fp);
 713	Py_END_ALLOW_THREADS
 714	while ((item = PyIter_Next(it)) != NULL) {
 715		Py_BEGIN_ALLOW_THREADS
 716		fputs(emit, fp);
 717		Py_END_ALLOW_THREADS
 718		emit = separator;
 719		if (PyObject_Print(item, fp, 0) != 0) {
 720			Py_DECREF(item);
 721			Py_DECREF(it);
 722			Py_ReprLeave(deque);
 723			return -1;
 724		}
 725		Py_DECREF(item);
 726	}
 727	Py_ReprLeave(deque);
 728	Py_DECREF(it);
 729	if (PyErr_Occurred())
 730		return -1;
 731
 732	Py_BEGIN_ALLOW_THREADS
 733	if (((dequeobject *)deque)->maxlen == -1)
 734		fputs("])", fp);
 735	else
 736		fprintf(fp, "], maxlen=%" PY_FORMAT_SIZE_T "d)", ((dequeobject *)deque)->maxlen);
 737	Py_END_ALLOW_THREADS
 738	return 0;
 739}
 740
 741static PyObject *
 742deque_richcompare(PyObject *v, PyObject *w, int op)
 743{
 744	PyObject *it1=NULL, *it2=NULL, *x, *y;
 745	Py_ssize_t vs, ws;
 746	int b, cmp=-1;
 747
 748	if (!PyObject_TypeCheck(v, &deque_type) ||
 749	    !PyObject_TypeCheck(w, &deque_type)) {
 750		Py_INCREF(Py_NotImplemented);
 751		return Py_NotImplemented;
 752	}
 753
 754	/* Shortcuts */
 755	vs = ((dequeobject *)v)->len;
 756	ws = ((dequeobject *)w)->len;
 757	if (op == Py_EQ) {
 758		if (v == w)
 759			Py_RETURN_TRUE;
 760		if (vs != ws)
 761			Py_RETURN_FALSE;
 762	}
 763	if (op == Py_NE) {
 764		if (v == w)
 765			Py_RETURN_FALSE;
 766		if (vs != ws)
 767			Py_RETURN_TRUE;
 768	}
 769
 770	/* Search for the first index where items are different */
 771	it1 = PyObject_GetIter(v);
 772	if (it1 == NULL)
 773		goto done;
 774	it2 = PyObject_GetIter(w);
 775	if (it2 == NULL)
 776		goto done;
 777	for (;;) {
 778		x = PyIter_Next(it1);
 779		if (x == NULL && PyErr_Occurred())
 780			goto done;
 781		y = PyIter_Next(it2);
 782		if (x == NULL || y == NULL)
 783			break;
 784		b = PyObject_RichCompareBool(x, y, Py_EQ);
 785		if (b == 0) {
 786			cmp = PyObject_RichCompareBool(x, y, op);
 787			Py_DECREF(x);
 788			Py_DECREF(y);
 789			goto done;
 790		}
 791		Py_DECREF(x);
 792		Py_DECREF(y);
 793		if (b == -1)
 794			goto done;
 795	}
 796	/* We reached the end of one deque or both */
 797	Py_XDECREF(x);
 798	Py_XDECREF(y);
 799	if (PyErr_Occurred())
 800		goto done;
 801	switch (op) {
 802	case Py_LT: cmp = y != NULL; break;  /* if w was longer */
 803	case Py_LE: cmp = x == NULL; break;  /* if v was not longer */
 804	case Py_EQ: cmp = x == y;    break;  /* if we reached the end of both */
 805	case Py_NE: cmp = x != y;    break;  /* if one deque continues */
 806	case Py_GT: cmp = x != NULL; break;  /* if v was longer */
 807	case Py_GE: cmp = y == NULL; break;  /* if w was not longer */
 808	}
 809
 810done:
 811	Py_XDECREF(it1);
 812	Py_XDECREF(it2);
 813	if (cmp == 1)
 814		Py_RETURN_TRUE;
 815	if (cmp == 0)
 816		Py_RETURN_FALSE;
 817	return NULL;
 818}
 819
 820static int
 821deque_init(dequeobject *deque, PyObject *args, PyObject *kwdargs)
 822{
 823	PyObject *iterable = NULL;
 824	PyObject *maxlenobj = NULL;
 825	Py_ssize_t maxlen = -1;
 826	char *kwlist[] = {"iterable", "maxlen", 0};
 827
 828	if (!PyArg_ParseTupleAndKeywords(args, kwdargs, "|OO:deque", kwlist, &iterable, &maxlenobj))
 829		return -1;
 830	if (maxlenobj != NULL && maxlenobj != Py_None) {
 831		maxlen = PyInt_AsSsize_t(maxlenobj);
 832		if (maxlen == -1 && PyErr_Occurred())
 833			return -1;
 834		if (maxlen < 0) {
 835			PyErr_SetString(PyExc_ValueError, "maxlen must be non-negative");
 836			return -1;
 837		}
 838	}
 839	deque->maxlen = maxlen;
 840	deque_clear(deque);
 841	if (iterable != NULL) {
 842		PyObject *rv = deque_extend(deque, iterable);
 843		if (rv == NULL)
 844			return -1;
 845		Py_DECREF(rv);
 846	}
 847	return 0;
 848}
 849
 850static PySequenceMethods deque_as_sequence = {
 851	(lenfunc)deque_len,		/* sq_length */
 852	0,				/* sq_concat */
 853	0,				/* sq_repeat */
 854	(ssizeargfunc)deque_item,	/* sq_item */
 855	0,				/* sq_slice */
 856	(ssizeobjargproc)deque_ass_item,	/* sq_ass_item */
 857};
 858
 859/* deque object ********************************************************/
 860
 861static PyObject *deque_iter(dequeobject *deque);
 862static PyObject *deque_reviter(dequeobject *deque);
 863PyDoc_STRVAR(reversed_doc,
 864	"D.__reversed__() -- return a reverse iterator over the deque");
 865
 866static PyMethodDef deque_methods[] = {
 867	{"append",		(PyCFunction)deque_append,
 868		METH_O,		 append_doc},
 869	{"appendleft",		(PyCFunction)deque_appendleft,
 870		METH_O,		 appendleft_doc},
 871	{"clear",		(PyCFunction)deque_clearmethod,
 872		METH_NOARGS,	 clear_doc},
 873	{"__copy__",		(PyCFunction)deque_copy,
 874		METH_NOARGS,	 copy_doc},
 875	{"extend",		(PyCFunction)deque_extend,
 876		METH_O,		 extend_doc},
 877	{"extendleft",		(PyCFunction)deque_extendleft,
 878		METH_O,		 extendleft_doc},
 879	{"pop",			(PyCFunction)deque_pop,
 880		METH_NOARGS,	 pop_doc},
 881	{"popleft",		(PyCFunction)deque_popleft,
 882		METH_NOARGS,	 popleft_doc},
 883	{"__reduce__",	(PyCFunction)deque_reduce,
 884		METH_NOARGS,	 reduce_doc},
 885	{"remove",		(PyCFunction)deque_remove,
 886		METH_O,		 remove_doc},
 887	{"__reversed__",	(PyCFunction)deque_reviter,
 888		METH_NOARGS,	 reversed_doc},
 889	{"rotate",		(PyCFunction)deque_rotate,
 890		METH_VARARGS,	rotate_doc},
 891	{NULL,		NULL}	/* sentinel */
 892};
 893
 894PyDoc_STRVAR(deque_doc,
 895"deque(iterable[, maxlen]) --> deque object\n\
 896\n\
 897Build an ordered collection accessible from endpoints only.");
 898
 899static PyTypeObject deque_type = {
 900	PyVarObject_HEAD_INIT(NULL, 0)
 901	"collections.deque",		/* tp_name */
 902	sizeof(dequeobject),		/* tp_basicsize */
 903	0,				/* tp_itemsize */
 904	/* methods */
 905	(destructor)deque_dealloc,	/* tp_dealloc */
 906	deque_tp_print,			/* tp_print */
 907	0,				/* tp_getattr */
 908	0,				/* tp_setattr */
 909	0,				/* tp_compare */
 910	deque_repr,			/* tp_repr */
 911	0,				/* tp_as_number */
 912	&deque_as_sequence,		/* tp_as_sequence */
 913	0,				/* tp_as_mapping */
 914	(hashfunc)PyObject_HashNotImplemented,	/* tp_hash */
 915	0,				/* tp_call */
 916	0,				/* tp_str */
 917	PyObject_GenericGetAttr,	/* tp_getattro */
 918	0,				/* tp_setattro */
 919	0,				/* tp_as_buffer */
 920	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC |
 921		Py_TPFLAGS_HAVE_WEAKREFS,	/* tp_flags */
 922	deque_doc,			/* tp_doc */
 923	(traverseproc)deque_traverse,	/* tp_traverse */
 924	(inquiry)deque_clear,		/* tp_clear */
 925	(richcmpfunc)deque_richcompare,	/* tp_richcompare */
 926	offsetof(dequeobject, weakreflist),	/* tp_weaklistoffset*/
 927	(getiterfunc)deque_iter,	/* tp_iter */
 928	0,				/* tp_iternext */
 929	deque_methods,			/* tp_methods */
 930	0,				/* tp_members */
 931	0,				/* tp_getset */
 932	0,				/* tp_base */
 933	0,				/* tp_dict */
 934	0,				/* tp_descr_get */
 935	0,				/* tp_descr_set */
 936	0,				/* tp_dictoffset */
 937	(initproc)deque_init,		/* tp_init */
 938	PyType_GenericAlloc,		/* tp_alloc */
 939	deque_new,			/* tp_new */
 940	PyObject_GC_Del,		/* tp_free */
 941};
 942
 943/*********************** Deque Iterator **************************/
 944
 945typedef struct {
 946	PyObject_HEAD
 947	Py_ssize_t index;
 948	block *b;
 949	dequeobject *deque;
 950	long state;	/* state when the iterator is created */
 951	Py_ssize_t counter;    /* number of items remaining for iteration */
 952} dequeiterobject;
 953
 954static PyTypeObject dequeiter_type;
 955
 956static PyObject *
 957deque_iter(dequeobject *deque)
 958{
 959	dequeiterobject *it;
 960
 961	it = PyObject_GC_New(dequeiterobject, &dequeiter_type);
 962	if (it == NULL)
 963		return NULL;
 964	it->b = deque->leftblock;
 965	it->index = deque->leftindex;
 966	Py_INCREF(deque);
 967	it->deque = deque;
 968	it->state = deque->state;
 969	it->counter = deque->len;
 970	PyObject_GC_Track(it);
 971	return (PyObject *)it;
 972}
 973
 974static int
 975dequeiter_traverse(dequeiterobject *dio, visitproc visit, void *arg)
 976{
 977	Py_VISIT(dio->deque);
 978	return 0;
 979}
 980
 981static void
 982dequeiter_dealloc(dequeiterobject *dio)
 983{
 984	Py_XDECREF(dio->deque);
 985	PyObject_GC_Del(dio);
 986}
 987
 988static PyObject *
 989dequeiter_next(dequeiterobject *it)
 990{
 991	PyObject *item;
 992
 993	if (it->deque->state != it->state) {
 994		it->counter = 0;
 995		PyErr_SetString(PyExc_RuntimeError,
 996				"deque mutated during iteration");
 997		return NULL;
 998	}
 999	if (it->counter == 0)
1000		return NULL;        
1001	assert (!(it->b == it->deque->rightblock &&
1002		  it->index > it->deque->rightindex));
1003
1004	item = it->b->data[it->index];
1005	it->index++;
1006	it->counter--;
1007	if (it->index == BLOCKLEN && it->counter > 0) {
1008		assert (it->b->rightlink != NULL);
1009		it->b = it->b->rightlink;
1010		it->index = 0;
1011	}
1012	Py_INCREF(item);
1013	return item;
1014}
1015
1016static PyObject *
1017dequeiter_len(dequeiterobject *it)
1018{
1019	return PyInt_FromLong(it->counter);
1020}
1021
1022PyDoc_STRVAR(length_hint_doc, "Private method returning an estimate of len(list(it)).");
1023
1024static PyMethodDef dequeiter_methods[] = {
1025	{"__length_hint__", (PyCFunction)dequeiter_len, METH_NOARGS, length_hint_doc},
1026 	{NULL,		NULL}		/* sentinel */
1027};
1028
1029static PyTypeObject dequeiter_type = {
1030	PyVarObject_HEAD_INIT(NULL, 0)
1031	"deque_iterator",			/* tp_name */
1032	sizeof(dequeiterobject),		/* tp_basicsize */
1033	0,					/* tp_itemsize */
1034	/* methods */
1035	(destructor)dequeiter_dealloc,		/* tp_dealloc */
1036	0,					/* tp_print */
1037	0,					/* tp_getattr */
1038	0,					/* tp_setattr */
1039	0,					/* tp_compare */
1040	0,					/* tp_repr */
1041	0,					/* tp_as_number */
1042	0,					/* tp_as_sequence */
1043	0,					/* tp_as_mapping */
1044	0,					/* tp_hash */
1045	0,					/* tp_call */
1046	0,					/* tp_str */
1047	PyObject_GenericGetAttr,		/* tp_getattro */
1048	0,					/* tp_setattro */
1049	0,					/* tp_as_buffer */
1050	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */
1051	0,					/* tp_doc */
1052	(traverseproc)dequeiter_traverse,	/* tp_traverse */
1053	0,					/* tp_clear */
1054	0,					/* tp_richcompare */
1055	0,					/* tp_weaklistoffset */
1056	PyObject_SelfIter,			/* tp_iter */
1057	(iternextfunc)dequeiter_next,		/* tp_iternext */
1058	dequeiter_methods,			/* tp_methods */
1059	0,
1060};
1061
1062/*********************** Deque Reverse Iterator **************************/
1063
1064static PyTypeObject dequereviter_type;
1065
1066static PyObject *
1067deque_reviter(dequeobject *deque)
1068{
1069	dequeiterobject *it;
1070
1071	it = PyObject_GC_New(dequeiterobject, &dequereviter_type);
1072	if (it == NULL)
1073		return NULL;
1074	it->b = deque->rightblock;
1075	it->index = deque->rightindex;
1076	Py_INCREF(deque);
1077	it->deque = deque;
1078	it->state = deque->state;
1079	it->counter = deque->len;
1080	PyObject_GC_Track(it);
1081	return (PyObject *)it;
1082}
1083
1084static PyObject *
1085dequereviter_next(dequeiterobject *it)
1086{
1087	PyObject *item;
1088	if (it->counter == 0)
1089		return NULL;
1090
1091	if (it->deque->state != it->state) {
1092		it->counter = 0;
1093		PyErr_SetString(PyExc_RuntimeError,
1094				"deque mutated during iteration");
1095		return NULL;
1096	}
1097	assert (!(it->b == it->deque->leftblock &&
1098		  it->index < it->deque->leftindex));
1099
1100	item = it->b->data[it->index];
1101	it->index--;
1102	it->counter--;
1103	if (it->index == -1 && it->counter > 0) {
1104		assert (it->b->leftlink != NULL);
1105		it->b = it->b->leftlink;
1106		it->index = BLOCKLEN - 1;
1107	}
1108	Py_INCREF(item);
1109	return item;
1110}
1111
1112static PyTypeObject dequereviter_type = {
1113	PyVarObject_HEAD_INIT(NULL, 0)
1114	"deque_reverse_iterator",		/* tp_name */
1115	sizeof(dequeiterobject),		/* tp_basicsize */
1116	0,					/* tp_itemsize */
1117	/* methods */
1118	(destructor)dequeiter_dealloc,		/* tp_dealloc */
1119	0,					/* tp_print */
1120	0,					/* tp_getattr */
1121	0,					/* tp_setattr */
1122	0,					/* tp_compare */
1123	0,					/* tp_repr */
1124	0,					/* tp_as_number */
1125	0,					/* tp_as_sequence */
1126	0,					/* tp_as_mapping */
1127	0,					/* tp_hash */
1128	0,					/* tp_call */
1129	0,					/* tp_str */
1130	PyObject_GenericGetAttr,		/* tp_getattro */
1131	0,					/* tp_setattro */
1132	0,					/* tp_as_buffer */
1133	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */
1134	0,					/* tp_doc */
1135	(traverseproc)dequeiter_traverse,	/* tp_traverse */
1136	0,					/* tp_clear */
1137	0,					/* tp_richcompare */
1138	0,					/* tp_weaklistoffset */
1139	PyObject_SelfIter,			/* tp_iter */
1140	(iternextfunc)dequereviter_next,	/* tp_iternext */
1141	dequeiter_methods,			/* tp_methods */
1142	0,
1143};
1144
1145/* defaultdict type *********************************************************/
1146
1147typedef struct {
1148	PyDictObject dict;
1149	PyObject *default_factory;
1150} defdictobject;
1151
1152static PyTypeObject defdict_type; /* Forward */
1153
1154PyDoc_STRVAR(defdict_missing_doc,
1155"__missing__(key) # Called by __getitem__ for missing key; pseudo-code:\n\
1156  if self.default_factory is None: raise KeyError((key,))\n\
1157  self[key] = value = self.default_factory()\n\
1158  return value\n\
1159");
1160
1161static PyObject *
1162defdict_missing(defdictobject *dd, PyObject *key)
1163{
1164	PyObject *factory = dd->default_factory;
1165	PyObject *value;
1166	if (factory == NULL || factory == Py_None) {
1167		/* XXX Call dict.__missing__(key) */
1168		PyObject *tup;
1169		tup = PyTuple_Pack(1, key);
1170		if (!tup) return NULL;
1171		PyErr_SetObject(PyExc_KeyError, tup);
1172		Py_DECREF(tup);
1173		return NULL;
1174	}
1175	value = PyEval_CallObject(factory, NULL);
1176	if (value == NULL)
1177		return value;
1178	if (PyObject_SetItem((PyObject *)dd, key, value) < 0) {
1179		Py_DECREF(value);
1180		return NULL;
1181	}
1182	return value;
1183}
1184
1185PyDoc_STRVAR(defdict_copy_doc, "D.copy() -> a shallow copy of D.");
1186
1187static PyObject *
1188defdict_copy(defdictobject *dd)
1189{
1190	/* This calls the object's class.  That only works for subclasses
1191	   whose class constructor has the same signature.  Subclasses that
1192	   define a different constructor signature must override copy().
1193	*/
1194
1195	if (dd->default_factory == NULL)
1196		return PyObject_CallFunctionObjArgs((PyObject*)Py_TYPE(dd), Py_None, dd, NULL);
1197	return PyObject_CallFunctionObjArgs((PyObject*)Py_TYPE(dd),
1198					    dd->default_factory, dd, NULL);
1199}
1200
1201static PyObject *
1202defdict_reduce(defdictobject *dd)
1203{
1204	/* __reduce__ must return a 5-tuple as follows:
1205
1206	   - factory function
1207	   - tuple of args for the factory function
1208	   - additional state (here None)
1209	   - sequence iterator (here None)
1210	   - dictionary iterator (yielding successive (key, value) pairs
1211
1212	   This API is used by pickle.py and copy.py.
1213
1214	   For this to be useful with pickle.py, the default_factory
1215	   must be picklable; e.g., None, a built-in, or a global
1216	   function in a module or package.
1217
1218	   Both shallow and deep copying are supported, but for deep
1219	   copying, the default_factory must be deep-copyable; e.g. None,
1220	   or a built-in (functions are not copyable at this time).
1221
1222	   This only works for subclasses as long as their constructor
1223	   signature is compatible; the first argument must be the
1224	   optional default_factory, defaulting to None.
1225	*/
1226	PyObject *args;
1227	PyObject *items;
1228	PyObject *result;
1229	if (dd->default_factory == NULL || dd->default_factory == Py_None)
1230		args = PyTuple_New(0);
1231	else
1232		args = PyTuple_Pack(1, dd->default_factory);
1233	if (args == NULL)
1234		return NULL;
1235	items = PyObject_CallMethod((PyObject *)dd, "iteritems", "()");
1236	if (items == NULL) {
1237		Py_DECREF(args);
1238		return NULL;
1239	}
1240	result = PyTuple_Pack(5, Py_TYPE(dd), args,
1241			      Py_None, Py_None, items);
1242	Py_DECREF(items);
1243	Py_DECREF(args);
1244	return result;
1245}
1246
1247static PyMethodDef defdict_methods[] = {
1248	{"__missing__", (PyCFunction)defdict_missing, METH_O,
1249	 defdict_missing_doc},
1250	{"copy", (PyCFunction)defdict_copy, METH_NOARGS,
1251	 defdict_copy_doc},
1252	{"__copy__", (PyCFunction)defdict_copy, METH_NOARGS,
1253	 defdict_copy_doc},
1254	{"__reduce__", (PyCFunction)defdict_reduce, METH_NOARGS,
1255	 reduce_doc},
1256	{NULL}
1257};
1258
1259static PyMemberDef defdict_members[] = {
1260	{"default_factory", T_OBJECT,
1261	 offsetof(defdictobject, default_factory), 0,
1262	 PyDoc_STR("Factory for default value called by __missing__().")},
1263	{NULL}
1264};
1265
1266static void
1267defdict_dealloc(defdictobject *dd)
1268{
1269	Py_CLEAR(dd->default_factory);
1270	PyDict_Type.tp_dealloc((PyObject *)dd);
1271}
1272
1273static int
1274defdict_print(defdictobject *dd, FILE *fp, int flags)
1275{
1276	int sts;
1277	Py_BEGIN_ALLOW_THREADS
1278	fprintf(fp, "defaultdict(");
1279	Py_END_ALLOW_THREADS
1280	if (dd->default_factory == NULL) {
1281		Py_BEGIN_ALLOW_THREADS
1282		fprintf(fp, "None");
1283		Py_END_ALLOW_THREADS
1284	} else {
1285		PyObject_Print(dd->default_factory, fp, 0);
1286	}
1287	Py_BEGIN_ALLOW_THREADS
1288	fprintf(fp, ", ");
1289	Py_END_ALLOW_THREADS
1290	sts = PyDict_Type.tp_print((PyObject *)dd, fp, 0);
1291	Py_BEGIN_ALLOW_THREADS
1292	fprintf(fp, ")");
1293	Py_END_ALLOW_THREADS
1294	return sts;
1295}
1296
1297static PyObject *
1298defdict_repr(defdictobject *dd)
1299{
1300	PyObject *defrepr;
1301	PyObject *baserepr;
1302	PyObject *result;
1303	baserepr = PyDict_Type.tp_repr((PyObject *)dd);
1304	if (baserepr == NULL)
1305		return NULL;
1306	if (dd->default_factory == NULL)
1307		defrepr = PyString_FromString("None");
1308	else
1309	{
1310		int status = Py_ReprEnter(dd->default_factory);
1311		if (status != 0) {
1312			if (status < 0)
1313				return NULL;
1314			defrepr = PyString_FromString("...");
1315		}
1316		else
1317			defrepr = PyObject_Repr(dd->default_factory);
1318		Py_ReprLeave(dd->default_factory);
1319	}
1320	if (defrepr == NULL) {
1321		Py_DECREF(baserepr);
1322		return NULL;
1323	}
1324	result = PyString_FromFormat("defaultdict(%s, %s)",
1325				     PyString_AS_STRING(defrepr),
1326				     PyString_AS_STRING(baserepr));
1327	Py_DECREF(defrepr);
1328	Py_DECREF(baserepr);
1329	return result;
1330}
1331
1332static int
1333defdict_traverse(PyObject *self, visitproc visit, void *arg)
1334{
1335	Py_VISIT(((defdictobject *)self)->default_factory);
1336	return PyDict_Type.tp_traverse(self, visit, arg);
1337}
1338
1339static int
1340defdict_tp_clear(defdictobject *dd)
1341{
1342	Py_CLEAR(dd->default_factory);
1343	return PyDict_Type.tp_clear((PyObject *)dd);
1344}
1345
1346static int
1347defdict_init(PyObject *self, PyObject *args, PyObject *kwds)
1348{
1349	defdictobject *dd = (defdictobject *)self;
1350	PyObject *olddefault = dd->default_factory;
1351	PyObject *newdefault = NULL;
1352	PyObject *newargs;
1353	int result;
1354	if (args == NULL || !PyTuple_Check(args))
1355		newargs = PyTuple_New(0);
1356	else {
1357		Py_ssize_t n = PyTuple_GET_SIZE(args);
1358		if (n > 0) {
1359			newdefault = PyTuple_GET_ITEM(args, 0);
1360			if (!PyCallable_Check(newdefault) && newdefault != Py_None) {
1361				PyErr_SetString(PyExc_TypeError,
1362					"first argument must be callable");                           
1363				return -1;
1364			}
1365		}
1366		newargs = PySequence_GetSlice(args, 1, n);
1367	}
1368	if (newargs == NULL)
1369		return -1;
1370	Py_XINCREF(newdefault);
1371	dd->default_factory = newdefault;
1372	result = PyDict_Type.tp_init(self, newargs, kwds);
1373	Py_DECREF(newargs);
1374	Py_XDECREF(olddefault);
1375	return result;
1376}
1377
1378PyDoc_STRVAR(defdict_doc,
1379"defaultdict(default_factory) --> dict with default factory\n\
1380\n\
1381The default factory is called without arguments to produce\n\
1382a new value when a key is not present, in __getitem__ only.\n\
1383A defaultdict compares equal to a dict with the same items.\n\
1384");
1385
1386/* See comment in xxsubtype.c */
1387#define DEFERRED_ADDRESS(ADDR) 0
1388
1389static PyTypeObject defdict_type = {
1390	PyVarObject_HEAD_INIT(DEFERRED_ADDRESS(&PyType_Type), 0)
1391	"collections.defaultdict",	/* tp_name */
1392	sizeof(defdictobject),		/* tp_basicsize */
1393	0,				/* tp_itemsize */
1394	/* methods */
1395	(destructor)defdict_dealloc,	/* tp_dealloc */
1396	(printfunc)defdict_print,	/* tp_print */
1397	0,				/* tp_getattr */
1398	0,				/* tp_setattr */
1399	0,				/* tp_compare */
1400	(reprfunc)defdict_repr,		/* tp_repr */
1401	0,				/* tp_as_number */
1402	0,				/* tp_as_sequence */
1403	0,				/* tp_as_mapping */
1404	0,	       			/* tp_hash */
1405	0,				/* tp_call */
1406	0,				/* tp_str */
1407	PyObject_GenericGetAttr,	/* tp_getattro */
1408	0,				/* tp_setattro */
1409	0,				/* tp_as_buffer */
1410	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC |
1411		Py_TPFLAGS_HAVE_WEAKREFS,	/* tp_flags */
1412	defdict_doc,			/* tp_doc */
1413	defdict_traverse,		/* tp_traverse */
1414	(inquiry)defdict_tp_clear,	/* tp_clear */
1415	0,				/* tp_richcompare */
1416	0,				/* tp_weaklistoffset*/
1417	0,				/* tp_iter */
1418	0,				/* tp_iternext */
1419	defdict_methods,		/* tp_methods */
1420	defdict_members,		/* tp_members */
1421	0,				/* tp_getset */
1422	DEFERRED_ADDRESS(&PyDict_Type),	/* tp_base */
1423	0,				/* tp_dict */
1424	0,				/* tp_descr_get */
1425	0,				/* tp_descr_set */
1426	0,				/* tp_dictoffset */
1427	defdict_init,			/* tp_init */
1428	PyType_GenericAlloc,		/* tp_alloc */
1429	0,				/* tp_new */
1430	PyObject_GC_Del,		/* tp_free */
1431};
1432
1433/* module level code ********************************************************/
1434
1435PyDoc_STRVAR(module_doc,
1436"High performance data structures.\n\
1437- deque:        ordered collection accessible from endpoints only\n\
1438- defaultdict:  dict subclass with a default value factory\n\
1439");
1440
1441PyMODINIT_FUNC
1442init_collections(void)
1443{
1444	PyObject *m;
1445
1446	m = Py_InitModule3("_collections", NULL, module_doc);
1447	if (m == NULL)
1448		return;
1449
1450	if (PyType_Ready(&deque_type) < 0)
1451		return;
1452	Py_INCREF(&deque_type);
1453	PyModule_AddObject(m, "deque", (PyObject *)&deque_type);
1454
1455	defdict_type.tp_base = &PyDict_Type;
1456	if (PyType_Ready(&defdict_type) < 0)
1457		return;
1458	Py_INCREF(&defdict_type);
1459	PyModule_AddObject(m, "defaultdict", (PyObject *)&defdict_type);
1460
1461	if (PyType_Ready(&dequeiter_type) < 0)
1462		return;
1463
1464	if (PyType_Ready(&dequereviter_type) < 0)
1465		return;
1466
1467	return;
1468}