Objects/listobject.c

   1 /***********************************************************
   2 Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam,
   3 The Netherlands.
   4
   5                         All Rights Reserved
   6
   7 Permission to use, copy, modify, and distribute this software and its
   8 documentation for any purpose and without fee is hereby granted,
   9 provided that the above copyright notice appear in all copies and that
  10 both that copyright notice and this permission notice appear in
  11 supporting documentation, and that the names of Stichting Mathematisch
  12 Centrum or CWI or Corporation for National Research Initiatives or
  13 CNRI not be used in advertising or publicity pertaining to
  14 distribution of the software without specific, written prior
  15 permission.
  16
  17 While CWI is the initial source for this software, a modified version
  18 is made available by the Corporation for National Research Initiatives
  19 (CNRI) at the Internet address ftp://ftp.python.org.
  20
  21 STICHTING MATHEMATISCH CENTRUM AND CNRI DISCLAIM ALL WARRANTIES WITH
  22 REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
  23 MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH
  24 CENTRUM OR CNRI BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
  25 DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  26 PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
  27 TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
  28 PERFORMANCE OF THIS SOFTWARE.
  29
  30 ******************************************************************/
  31
  32 /* List object implementation */
  33
  34 #include "Python.h"
  35
  36 #ifdef STDC_HEADERS
  37 #include <stddef.h>
  38 #else
  39 #include <sys/types.h>          /* For size_t */
  40 #endif
  41
  42 #define ROUNDUP(n, PyTryBlock) \
  43         ((((n)+(PyTryBlock)-1)/(PyTryBlock))*(PyTryBlock))
  44
  45 static int
  46 roundupsize(n)
  47         int n;
  48 {
  49         if (n < 500)
  50                 return ROUNDUP(n, 10);
  51         else
  52                 return ROUNDUP(n, 100);
  53 }
  54
  55 #define NRESIZE(var, type, nitems) PyMem_RESIZE(var, type, roundupsize(nitems))
  56
  57 PyObject *
  58 PyList_New(size)
  59         int size;
  60 {
  61         int i;
  62         PyListObject *op;
  63         size_t nbytes;
  64         if (size < 0) {
  65                 PyErr_BadInternalCall();
  66                 return NULL;
  67         }
  68         nbytes = size * sizeof(PyObject *);
  69         /* Check for overflow */
  70         if (nbytes / sizeof(PyObject *) != (size_t)size) {
  71                 return PyErr_NoMemory();
  72         }
  73         op = (PyListObject *) malloc(sizeof(PyListObject));
  74         if (op == NULL) {
  75                 return PyErr_NoMemory();
  76         }
  77         if (size <= 0) {
  78                 op->ob_item = NULL;
  79         }
  80         else {
  81                 op->ob_item = (PyObject **) malloc(nbytes);
  82                 if (op->ob_item == NULL) {
  83                         free((ANY *)op);
  84                         return PyErr_NoMemory();
  85                 }
  86         }
  87         op->ob_type = &PyList_Type;
  88         op->ob_size = size;
  89         for (i = 0; i < size; i++)
  90                 op->ob_item[i] = NULL;
  91         _Py_NewReference(op);
  92         return (PyObject *) op;
  93 }
  94
  95 int
  96 PyList_Size(op)
  97         PyObject *op;
  98 {
  99         if (!PyList_Check(op)) {
 100                 PyErr_BadInternalCall();
 101                 return -1;
 102         }
 103         else
 104                 return ((PyListObject *)op) -> ob_size;
 105 }
 106
 107 static PyObject *indexerr;
 108
 109 PyObject *
 110 PyList_GetItem(op, i)
 111         PyObject *op;
 112         int i;
 113 {
 114         if (!PyList_Check(op)) {
 115                 PyErr_BadInternalCall();
 116                 return NULL;
 117         }
 118         if (i < 0 || i >= ((PyListObject *)op) -> ob_size) {
 119                 if (indexerr == NULL)
 120                         indexerr = PyString_FromString(
 121                                 "list index out of range");
 122                 PyErr_SetObject(PyExc_IndexError, indexerr);
 123                 return NULL;
 124         }
 125         return ((PyListObject *)op) -> ob_item[i];
 126 }
 127
 128 int
 129 PyList_SetItem(op, i, newitem)
 130         register PyObject *op;
 131         register int i;
 132         register PyObject *newitem;
 133 {
 134         register PyObject *olditem;
 135         register PyObject **p;
 136         if (!PyList_Check(op)) {
 137                 Py_XDECREF(newitem);
 138                 PyErr_BadInternalCall();
 139                 return -1;
 140         }
 141         if (i < 0 || i >= ((PyListObject *)op) -> ob_size) {
 142                 Py_XDECREF(newitem);
 143                 PyErr_SetString(PyExc_IndexError,
 144                                 "list assignment index out of range");
 145                 return -1;
 146         }
 147         p = ((PyListObject *)op) -> ob_item + i;
 148         olditem = *p;
 149         *p = newitem;
 150         Py_XDECREF(olditem);
 151         return 0;
 152 }
 153
 154 static int
 155 ins1(self, where, v)
 156         PyListObject *self;
 157         int where;
 158         PyObject *v;
 159 {
 160         int i;
 161         PyObject **items;
 162         if (v == NULL) {
 163                 PyErr_BadInternalCall();
 164                 return -1;
 165         }
 166         items = self->ob_item;
 167         NRESIZE(items, PyObject *, self->ob_size+1);
 168         if (items == NULL) {
 169                 PyErr_NoMemory();
 170                 return -1;
 171         }
 172         if (where < 0)
 173                 where = 0;
 174         if (where > self->ob_size)
 175                 where = self->ob_size;
 176         for (i = self->ob_size; --i >= where; )
 177                 items[i+1] = items[i];
 178         Py_INCREF(v);
 179         items[where] = v;
 180         self->ob_item = items;
 181         self->ob_size++;
 182         return 0;
 183 }
 184
 185 int
 186 PyList_Insert(op, where, newitem)
 187         PyObject *op;
 188         int where;
 189         PyObject *newitem;
 190 {
 191         if (!PyList_Check(op)) {
 192                 PyErr_BadInternalCall();
 193                 return -1;
 194         }
 195         return ins1((PyListObject *)op, where, newitem);
 196 }
 197
 198 int
 199 PyList_Append(op, newitem)
 200         PyObject *op;
 201         PyObject *newitem;
 202 {
 203         if (!PyList_Check(op)) {
 204                 PyErr_BadInternalCall();
 205                 return -1;
 206         }
 207         return ins1((PyListObject *)op,
 208                 (int) ((PyListObject *)op)->ob_size, newitem);
 209 }
 210
 211 /* Methods */
 212
 213 static void
 214 list_dealloc(op)
 215         PyListObject *op;
 216 {
 217         int i;
 218         if (op->ob_item != NULL) {
 219                 for (i = 0; i < op->ob_size; i++) {
 220                         Py_XDECREF(op->ob_item[i]);
 221                 }
 222                 free((ANY *)op->ob_item);
 223         }
 224         free((ANY *)op);
 225 }
 226
 227 static int
 228 list_print(op, fp, flags)
 229         PyListObject *op;
 230         FILE *fp;
 231         int flags;
 232 {
 233         int i;
 234
 235         i = Py_ReprEnter((PyObject*)op);
 236         if (i != 0) {
 237                 if (i < 0)
 238                         return i;
 239                 fprintf(fp, "[...]");
 240                 return 0;
 241         }
 242         fprintf(fp, "[");
 243         for (i = 0; i < op->ob_size; i++) {
 244                 if (i > 0)
 245                         fprintf(fp, ", ");
 246                 if (PyObject_Print(op->ob_item[i], fp, 0) != 0) {
 247                         Py_ReprLeave((PyObject *)op);
 248                         return -1;
 249                 }
 250         }
 251         fprintf(fp, "]");
 252         Py_ReprLeave((PyObject *)op);
 253         return 0;
 254 }
 255
 256 static PyObject *
 257 list_repr(v)
 258         PyListObject *v;
 259 {
 260         PyObject *s, *comma;
 261         int i;
 262
 263         i = Py_ReprEnter((PyObject*)v);
 264         if (i != 0) {
 265                 if (i > 0)
 266                         return PyString_FromString("[...]");
 267                 return NULL;
 268         }
 269         s = PyString_FromString("[");
 270         comma = PyString_FromString(", ");
 271         for (i = 0; i < v->ob_size && s != NULL; i++) {
 272                 if (i > 0)
 273                         PyString_Concat(&s, comma);
 274                 PyString_ConcatAndDel(&s, PyObject_Repr(v->ob_item[i]));
 275         }
 276         Py_XDECREF(comma);
 277         PyString_ConcatAndDel(&s, PyString_FromString("]"));
 278         Py_ReprLeave((PyObject *)v);
 279         return s;
 280 }
 281
 282 static int
 283 list_compare(v, w)
 284         PyListObject *v, *w;
 285 {
 286         int i;
 287         for (i = 0; i < v->ob_size && i < w->ob_size; i++) {
 288                 int cmp = PyObject_Compare(v->ob_item[i], w->ob_item[i]);
 289                 if (cmp != 0)
 290                         return cmp;
 291         }
 292         return v->ob_size - w->ob_size;
 293 }
 294
 295 static int
 296 list_length(a)
 297         PyListObject *a;
 298 {
 299         return a->ob_size;
 300 }
 301
 302 static PyObject *
 303 list_item(a, i)
 304         PyListObject *a;
 305         int i;
 306 {
 307         if (i < 0 || i >= a->ob_size) {
 308                 if (indexerr == NULL)
 309                         indexerr = PyString_FromString(
 310                                 "list index out of range");
 311                 PyErr_SetObject(PyExc_IndexError, indexerr);
 312                 return NULL;
 313         }
 314         Py_INCREF(a->ob_item[i]);
 315         return a->ob_item[i];
 316 }
 317
 318 static PyObject *
 319 list_slice(a, ilow, ihigh)
 320         PyListObject *a;
 321         int ilow, ihigh;
 322 {
 323         PyListObject *np;
 324         int i;
 325         if (ilow < 0)
 326                 ilow = 0;
 327         else if (ilow > a->ob_size)
 328                 ilow = a->ob_size;
 329         if (ihigh < ilow)
 330                 ihigh = ilow;
 331         else if (ihigh > a->ob_size)
 332                 ihigh = a->ob_size;
 333         np = (PyListObject *) PyList_New(ihigh - ilow);
 334         if (np == NULL)
 335                 return NULL;
 336         for (i = ilow; i < ihigh; i++) {
 337                 PyObject *v = a->ob_item[i];
 338                 Py_INCREF(v);
 339                 np->ob_item[i - ilow] = v;
 340         }
 341         return (PyObject *)np;
 342 }
 343
 344 PyObject *
 345 PyList_GetSlice(a, ilow, ihigh)
 346         PyObject *a;
 347         int ilow, ihigh;
 348 {
 349         if (!PyList_Check(a)) {
 350                 PyErr_BadInternalCall();
 351                 return NULL;
 352         }
 353         return list_slice((PyListObject *)a, ilow, ihigh);
 354 }
 355
 356 static PyObject *
 357 list_concat(a, bb)
 358         PyListObject *a;
 359         PyObject *bb;
 360 {
 361         int size;
 362         int i;
 363         PyListObject *np;
 364         if (!PyList_Check(bb)) {
 365                 PyErr_BadArgument();
 366                 return NULL;
 367         }
 368 #define b ((PyListObject *)bb)
 369         size = a->ob_size + b->ob_size;
 370         np = (PyListObject *) PyList_New(size);
 371         if (np == NULL) {
 372                 return NULL;
 373         }
 374         for (i = 0; i < a->ob_size; i++) {
 375                 PyObject *v = a->ob_item[i];
 376                 Py_INCREF(v);
 377                 np->ob_item[i] = v;
 378         }
 379         for (i = 0; i < b->ob_size; i++) {
 380                 PyObject *v = b->ob_item[i];
 381                 Py_INCREF(v);
 382                 np->ob_item[i + a->ob_size] = v;
 383         }
 384         return (PyObject *)np;
 385 #undef b
 386 }
 387
 388 static PyObject *
 389 list_repeat(a, n)
 390         PyListObject *a;
 391         int n;
 392 {
 393         int i, j;
 394         int size;
 395         PyListObject *np;
 396         PyObject **p;
 397         if (n < 0)
 398                 n = 0;
 399         size = a->ob_size * n;
 400         np = (PyListObject *) PyList_New(size);
 401         if (np == NULL)
 402                 return NULL;
 403         p = np->ob_item;
 404         for (i = 0; i < n; i++) {
 405                 for (j = 0; j < a->ob_size; j++) {
 406                         *p = a->ob_item[j];
 407                         Py_INCREF(*p);
 408                         p++;
 409                 }
 410         }
 411         return (PyObject *) np;
 412 }
 413
 414 static int
 415 list_ass_slice(a, ilow, ihigh, v)
 416         PyListObject *a;
 417         int ilow, ihigh;
 418         PyObject *v;
 419 {
 420         /* Because [X]DECREF can recursively invoke list operations on
 421            this list, we must postpone all [X]DECREF activity until
 422            after the list is back in its canonical shape.  Therefore
 423            we must allocate an additional array, 'recycle', into which
 424            we temporarily copy the items that are deleted from the
 425            list. :-( */
 426         PyObject **recycle, **p;
 427         PyObject **item;
 428         int n; /* Size of replacement list */
 429         int d; /* Change in size */
 430         int k; /* Loop index */
 431 #define b ((PyListObject *)v)
 432         if (v == NULL)
 433                 n = 0;
 434         else if (PyList_Check(v)) {
 435                 n = b->ob_size;
 436                 if (a == b) {
 437                         /* Special case "a[i:j] = a" -- copy b first */
 438                         int ret;
 439                         v = list_slice(b, 0, n);
 440                         ret = list_ass_slice(a, ilow, ihigh, v);
 441                         Py_DECREF(v);
 442                         return ret;
 443                 }
 444         }
 445         else {
 446                 PyErr_BadArgument();
 447                 return -1;
 448         }
 449         if (ilow < 0)
 450                 ilow = 0;
 451         else if (ilow > a->ob_size)
 452                 ilow = a->ob_size;
 453         if (ihigh < ilow)
 454                 ihigh = ilow;
 455         else if (ihigh > a->ob_size)
 456                 ihigh = a->ob_size;
 457         item = a->ob_item;
 458         d = n - (ihigh-ilow);
 459         if (ihigh > ilow)
 460                 p = recycle = PyMem_NEW(PyObject *, (ihigh-ilow));
 461         else
 462                 p = recycle = NULL;
 463         if (d <= 0) { /* Delete -d items; recycle ihigh-ilow items */
 464                 for (k = ilow; k < ihigh; k++)
 465                         *p++ = item[k];
 466                 if (d < 0) {
 467                         for (/*k = ihigh*/; k < a->ob_size; k++)
 468                                 item[k+d] = item[k];
 469                         a->ob_size += d;
 470                         NRESIZE(item, PyObject *, a->ob_size); /* Can't fail */
 471                         a->ob_item = item;
 472                 }
 473         }
 474         else { /* Insert d items; recycle ihigh-ilow items */
 475                 NRESIZE(item, PyObject *, a->ob_size + d);
 476                 if (item == NULL) {
 477                         PyMem_XDEL(recycle);
 478                         PyErr_NoMemory();
 479                         return -1;
 480                 }
 481                 for (k = a->ob_size; --k >= ihigh; )
 482                         item[k+d] = item[k];
 483                 for (/*k = ihigh-1*/; k >= ilow; --k)
 484                         *p++ = item[k];
 485                 a->ob_item = item;
 486                 a->ob_size += d;
 487         }
 488         for (k = 0; k < n; k++, ilow++) {
 489                 PyObject *w = b->ob_item[k];
 490                 Py_XINCREF(w);
 491                 item[ilow] = w;
 492         }
 493         if (recycle) {
 494                 while (--p >= recycle)
 495                         Py_XDECREF(*p);
 496                 PyMem_DEL(recycle);
 497         }
 498         return 0;
 499 #undef b
 500 }
 501
 502 int
 503 PyList_SetSlice(a, ilow, ihigh, v)
 504         PyObject *a;
 505         int ilow, ihigh;
 506         PyObject *v;
 507 {
 508         if (!PyList_Check(a)) {
 509                 PyErr_BadInternalCall();
 510                 return -1;
 511         }
 512         return list_ass_slice((PyListObject *)a, ilow, ihigh, v);
 513 }
 514
 515 static int
 516 list_ass_item(a, i, v)
 517         PyListObject *a;
 518         int i;
 519         PyObject *v;
 520 {
 521         PyObject *old_value;
 522         if (i < 0 || i >= a->ob_size) {
 523                 PyErr_SetString(PyExc_IndexError,
 524                                 "list assignment index out of range");
 525                 return -1;
 526         }
 527         if (v == NULL)
 528                 return list_ass_slice(a, i, i+1, v);
 529         Py_INCREF(v);
 530         old_value = a->ob_item[i];
 531         a->ob_item[i] = v;
 532         Py_DECREF(old_value);
 533         return 0;
 534 }
 535
 536 static PyObject *
 537 ins(self, where, v)
 538         PyListObject *self;
 539         int where;
 540         PyObject *v;
 541 {
 542         if (ins1(self, where, v) != 0)
 543                 return NULL;
 544         Py_INCREF(Py_None);
 545         return Py_None;
 546 }
 547
 548 static PyObject *
 549 listinsert(self, args)
 550         PyListObject *self;
 551         PyObject *args;
 552 {
 553         int i;
 554         PyObject *v;
 555         if (!PyArg_Parse(args, "(iO)", &i, &v))
 556                 return NULL;
 557         return ins(self, i, v);
 558 }
 559
 560 static PyObject *
 561 listappend(self, args)
 562         PyListObject *self;
 563         PyObject *args;
 564 {
 565         PyObject *v;
 566         if (!PyArg_Parse(args, "O", &v))
 567                 return NULL;
 568         return ins(self, (int) self->ob_size, v);
 569 }
 570
 571 static PyObject *
 572 listextend(self, args)
 573         PyListObject *self;
 574         PyObject *args;
 575 {
 576         PyObject *b = NULL, *res = NULL;
 577         PyObject **items;
 578         int selflen = PyList_GET_SIZE(self);
 579         int blen;
 580         register int i;
 581
 582         if (!PyArg_ParseTuple(args, "O", &b))
 583                 return NULL;
 584
 585         if (!PyList_Check(b)) {
 586                 PyErr_SetString(PyExc_TypeError,
 587                                 "list.extend() argument must be a list");
 588                 return NULL;
 589         }
 590         if (PyList_GET_SIZE(b) == 0) {
 591                 /* short circuit when b is empty */
 592                 Py_INCREF(Py_None);
 593                 return Py_None;
 594         }
 595         if (self == (PyListObject*)b) {
 596                 /* as in list_ass_slice() we must special case the
 597                  * situation: a.extend(a)
 598                  *
 599                  * XXX: I think this way ought to be faster than using
 600                  * list_slice() the way list_ass_slice() does.
 601                  */
 602                 b = PyList_New(selflen);
 603                 if (!b)
 604                         return NULL;
 605                 for (i = 0; i < selflen; i++) {
 606                         PyObject *o = PyList_GET_ITEM(self, i);
 607                         Py_INCREF(o);
 608                         PyList_SET_ITEM(b, i, o);
 609                 }
 610         }
 611         else
 612                 /* we want b to have the same refcount semantics for the
 613                  * Py_XDECREF() in the finally clause regardless of which
 614                  * branch in the above conditional we took.
 615                  */
 616                 Py_INCREF(b);
 617
 618         blen = PyList_GET_SIZE(b);
 619         /* resize a using idiom */
 620         items = self->ob_item;
 621         NRESIZE(items, PyObject*, selflen + blen);
 622         if (items == NULL ) {
 623                 PyErr_NoMemory();
 624                 goto finally;
 625         }
 626         self->ob_item = items;
 627
 628         /* populate the end self with b's items */
 629         for (i = 0; i < blen; i++) {
 630                 PyObject *o = PyList_GET_ITEM(b, i);
 631                 Py_INCREF(o);
 632                 PyList_SET_ITEM(self, self->ob_size++, o);
 633         }
 634         res = Py_None;
 635         Py_INCREF(res);
 636   finally:
 637         Py_XDECREF(b);
 638         return res;
 639 }
 640
 641
 642 static PyObject *
 643 listpop(self, args)
 644         PyListObject *self;
 645         PyObject *args;
 646 {
 647         int i = -1;
 648         PyObject *v;
 649         if (!PyArg_ParseTuple(args, "|i", &i))
 650                 return NULL;
 651         if (self->ob_size == 0) {
 652                 /* Special-case most common failure cause */
 653                 PyErr_SetString(PyExc_IndexError, "pop from empty list");
 654                 return NULL;
 655         }
 656         if (i < 0)
 657                 i += self->ob_size;
 658         if (i < 0 || i >= self->ob_size) {
 659                 PyErr_SetString(PyExc_IndexError, "pop index out of range");
 660                 return NULL;
 661         }
 662         v = self->ob_item[i];
 663         Py_INCREF(v);
 664         if (list_ass_slice(self, i, i+1, (PyObject *)NULL) != 0) {
 665                 Py_DECREF(v);
 666                 return NULL;
 667         }
 668         return v;
 669 }
 670
 671 /* New quicksort implementation for arrays of object pointers.
 672    Thanks to discussions with Tim Peters. */
 673
 674 /* CMPERROR is returned by our comparison function when an error
 675    occurred.  This is the largest negative integer (0x80000000 on a
 676    32-bit system). */
 677 #define CMPERROR ( (int) ((unsigned int)1 << (8*sizeof(int) - 1)) )
 678
 679 /* Comparison function.  Takes care of calling a user-supplied
 680    comparison function (any callable Python object).  Calls the
 681    standard comparison function, PyObject_Compare(), if the user-
 682    supplied function is NULL. */
 683
 684 static int
 685 docompare(x, y, compare)
 686         PyObject *x;
 687         PyObject *y;
 688         PyObject *compare;
 689 {
 690         PyObject *args, *res;
 691         int i;
 692
 693         if (compare == NULL) {
 694                 i = PyObject_Compare(x, y);
 695                 if (i && PyErr_Occurred())
 696                         i = CMPERROR;
 697                 return i;
 698         }
 699
 700         args = Py_BuildValue("(OO)", x, y);
 701         if (args == NULL)
 702                 return CMPERROR;
 703         res = PyEval_CallObject(compare, args);
 704         Py_DECREF(args);
 705         if (res == NULL)
 706                 return CMPERROR;
 707         if (!PyInt_Check(res)) {
 708                 Py_DECREF(res);
 709                 PyErr_SetString(PyExc_TypeError,
 710                                 "comparison function should return int");
 711                 return CMPERROR;
 712         }
 713         i = PyInt_AsLong(res);
 714         Py_DECREF(res);
 715         if (i < 0)
 716                 return -1;
 717         if (i > 0)
 718                 return 1;
 719         return 0;
 720 }
 721
 722 /* MINSIZE is the smallest array that will get a full-blown samplesort
 723    treatment; smaller arrays are sorted using binary insertion.  It must
 724    be at least 7 for the samplesort implementation to work.  Binary
 725    insertion does fewer compares, but can suffer O(N**2) data movement.
 726    The more expensive compares, the larger MINSIZE should be. */
 727 #define MINSIZE 100
 728
 729 /* MINPARTITIONSIZE is the smallest array slice samplesort will bother to
 730    partition; smaller slices are passed to binarysort.  It must be at
 731    least 2, and no larger than MINSIZE.  Setting it higher reduces the #
 732    of compares slowly, but increases the amount of data movement quickly.
 733    The value here was chosen assuming a compare costs ~25x more than
 734    swapping a pair of memory-resident pointers -- but under that assumption,
 735    changing the value by a few dozen more or less has aggregate effect
 736    under 1%.  So the value is crucial, but not touchy <wink>. */
 737 #define MINPARTITIONSIZE 40
 738
 739 /* MAXMERGE is the largest number of elements we'll always merge into
 740    a known-to-be sorted chunk via binary insertion, regardless of the
 741    size of that chunk.  Given a chunk of N sorted elements, and a group
 742    of K unknowns, the largest K for which it's better to do insertion
 743    (than a full-blown sort) is a complicated function of N and K mostly
 744    involving the expected number of compares and data moves under each
 745    approach, and the relative cost of those operations on a specific
 746    architecure.  The fixed value here is conservative, and should be a
 747    clear win regardless of architecture or N. */
 748 #define MAXMERGE 15
 749
 750 /* STACKSIZE is the size of our work stack.  A rough estimate is that
 751    this allows us to sort arrays of size N where
 752    N / ln(N) = MINPARTITIONSIZE * 2**STACKSIZE, so 60 is more than enough
 753    for arrays of size 2**64.  Because we push the biggest partition
 754    first, the worst case occurs when all subarrays are always partitioned
 755    exactly in two. */
 756 #define STACKSIZE 60
 757
 758
 759 #define SETK(X,Y) if ((k = docompare(X,Y,compare))==CMPERROR) goto fail
 760
 761 /* binarysort is the best method for sorting small arrays: it does
 762    few compares, but can do data movement quadratic in the number of
 763    elements.
 764    [lo, hi) is a contiguous slice of a list, and is sorted via
 765    binary insertion.
 766    On entry, must have lo <= start <= hi, and that [lo, start) is already
 767    sorted (pass start == lo if you don't know!).
 768    If docompare complains (returns CMPERROR) return -1, else 0.
 769    Even in case of error, the output slice will be some permutation of
 770    the input (nothing is lost or duplicated).
 771 */
 772
 773 static int
 774 binarysort(lo, hi, start, compare)
 775         PyObject **lo;
 776         PyObject **hi;
 777         PyObject **start;
 778         PyObject *compare;/* Comparison function object, or NULL for default */
 779 {
 780         /* assert lo <= start <= hi
 781            assert [lo, start) is sorted */
 782         register int k;
 783         register PyObject **l, **p, **r;
 784         register PyObject *pivot;
 785
 786         if (lo == start)
 787                 ++start;
 788         for (; start < hi; ++start) {
 789                 /* set l to where *start belongs */
 790                 l = lo;
 791                 r = start;
 792                 pivot = *r;
 793                 do {
 794                         p = l + ((r - l) >> 1);
 795                         SETK(pivot, *p);
 796                         if (k < 0)
 797                                 r = p;
 798                         else
 799                                 l = p + 1;
 800                 } while (l < r);
 801                 /* Pivot should go at l -- slide over to make room.
 802                    Caution: using memmove is much slower under MSVC 5;
 803                    we're not usually moving many slots. */
 804                 for (p = start; p > l; --p)
 805                         *p = *(p-1);
 806                 *l = pivot;
 807         }
 808         return 0;
 809
 810  fail:
 811         return -1;
 812 }
 813
 814 /* samplesortslice is the sorting workhorse.
 815    [lo, hi) is a contiguous slice of a list, to be sorted in place.
 816    On entry, must have lo <= hi,
 817    If docompare complains (returns CMPERROR) return -1, else 0.
 818    Even in case of error, the output slice will be some permutation of
 819    the input (nothing is lost or duplicated).
 820
 821    samplesort is basically quicksort on steroids:  a power of 2 close
 822    to n/ln(n) is computed, and that many elements (less 1) are picked at
 823    random from the array and sorted.  These 2**k - 1 elements are then
 824    used as preselected pivots for an equal number of quicksort
 825    partitioning steps, partitioning the slice into 2**k chunks each of
 826    size about ln(n).  These small final chunks are then usually handled
 827    by binarysort.  Note that when k=1, this is roughly the same as an
 828    ordinary quicksort using a random pivot, and when k=2 this is roughly
 829    a median-of-3 quicksort.  From that view, using k ~= lg(n/ln(n)) makes
 830    this a "median of n/ln(n)" quicksort.  You can also view it as a kind
 831    of bucket sort, where 2**k-1 bucket boundaries are picked dynamically.
 832
 833    The large number of samples makes a quadratic-time case almost
 834    impossible, and asymptotically drives the average-case number of
 835    compares from quicksort's 2 N ln N (or 12/7 N ln N for the median-of-
 836    3 variant) down to N lg N.
 837
 838    We also play lots of low-level tricks to cut the number of compares.
 839
 840    Very obscure:  To avoid using extra memory, the PPs are stored in the
 841    array and shuffled around as partitioning proceeds.  At the start of a
 842    partitioning step, we'll have 2**m-1 (for some m) PPs in sorted order,
 843    adjacent (either on the left or the right!) to a chunk of X elements
 844    that are to be partitioned: P X or X P.  In either case we need to
 845    shuffle things *in place* so that the 2**(m-1) smaller PPs are on the
 846    left, followed by the PP to be used for this step (that's the middle
 847    of the PPs), followed by X, followed by the 2**(m-1) larger PPs:
 848        P X or X P -> Psmall pivot X Plarge
 849    and the order of the PPs must not be altered.  It can take a while
 850    to realize this isn't trivial!  It can take even longer <wink> to
 851    understand why the simple code below works, using only 2**(m-1) swaps.
 852    The key is that the order of the X elements isn't necessarily
 853    preserved:  X can end up as some cyclic permutation of its original
 854    order.  That's OK, because X is unsorted anyway.  If the order of X
 855    had to be preserved too, the simplest method I know of using O(1)
 856    scratch storage requires len(X) + 2**(m-1) swaps, spread over 2 passes.
 857    Since len(X) is typically several times larger than 2**(m-1), that
 858    would slow things down.
 859 */
 860
 861 struct SamplesortStackNode {
 862         /* Represents a slice of the array, from (& including) lo up
 863            to (but excluding) hi.  "extra" additional & adjacent elements
 864            are pre-selected pivots (PPs), spanning [lo-extra, lo) if
 865            extra > 0, or [hi, hi-extra) if extra < 0.  The PPs are
 866            already sorted, but nothing is known about the other elements
 867            in [lo, hi). |extra| is always one less than a power of 2.
 868            When extra is 0, we're out of PPs, and the slice must be
 869            sorted by some other means. */
 870         PyObject **lo;
 871         PyObject **hi;
 872         int extra;
 873 };
 874
 875 /* The number of PPs we want is 2**k - 1, where 2**k is as close to
 876    N / ln(N) as possible.  So k ~= lg(N / ln(N)).  Calling libm routines
 877    is undesirable, so cutoff values are canned in the "cutoff" table
 878    below:  cutoff[i] is the smallest N such that k == CUTOFFBASE + i. */
 879 #define CUTOFFBASE 4
 880 static int cutoff[] = {
 881         43,        /* smallest N such that k == 4 */
 882         106,       /* etc */
 883         250,
 884         576,
 885         1298,
 886         2885,
 887         6339,
 888         13805,
 889         29843,
 890         64116,
 891         137030,
 892         291554,
 893         617916,
 894         1305130,
 895         2748295,
 896         5771662,
 897         12091672,
 898         25276798,
 899         52734615,
 900         109820537,
 901         228324027,
 902         473977813,
 903         982548444,   /* smallest N such that k == 26 */
 904         2034159050   /* largest N that fits in signed 32-bit; k == 27 */
 905 };
 906
 907 static int
 908 samplesortslice(lo, hi, compare)
 909         PyObject **lo;
 910         PyObject **hi;
 911         PyObject *compare;/* Comparison function object, or NULL for default */
 912 {
 913         register PyObject **l, **r;
 914         register PyObject *tmp, *pivot;
 915         register int k;
 916         int n, extra, top, extraOnRight;
 917         struct SamplesortStackNode stack[STACKSIZE];
 918
 919         /* assert lo <= hi */
 920         n = hi - lo;
 921
 922         /* ----------------------------------------------------------
 923          * Special cases
 924          * --------------------------------------------------------*/
 925         if (n < 2)
 926                 return 0;
 927
 928         /* Set r to the largest value such that [lo,r) is sorted.
 929            This catches the already-sorted case, the all-the-same
 930            case, and the appended-a-few-elements-to-a-sorted-list case.
 931            If the array is unsorted, we're very likely to get out of
 932            the loop fast, so the test is cheap if it doesn't pay off.
 933         */
 934         /* assert lo < hi */
 935         for (r = lo+1; r < hi; ++r) {
 936                 SETK(*r, *(r-1));
 937                 if (k < 0)
 938                         break;
 939         }
 940         /* [lo,r) is sorted, [r,hi) unknown.  Get out cheap if there are
 941            few unknowns, or few elements in total. */
 942         if (hi - r <= MAXMERGE || n < MINSIZE)
 943                 return binarysort(lo, hi, r, compare);
 944
 945         /* Check for the array already being reverse-sorted.  Typical
 946            benchmark-driven silliness <wink>. */
 947         /* assert lo < hi */
 948         for (r = lo+1; r < hi; ++r) {
 949                 SETK(*(r-1), *r);
 950                 if (k < 0)
 951                         break;
 952         }
 953         if (hi - r <= MAXMERGE) {
 954                 /* Reverse the reversed prefix, then insert the tail */
 955                 PyObject **originalr = r;
 956                 l = lo;
 957                 do {
 958                         --r;
 959                         tmp = *l; *l = *r; *r = tmp;
 960                         ++l;
 961                 } while (l < r);
 962                 return binarysort(lo, hi, originalr, compare);
 963         }
 964
 965         /* ----------------------------------------------------------
 966          * Normal case setup: a large array without obvious pattern.
 967          * --------------------------------------------------------*/
 968
 969         /* extra := a power of 2 ~= n/ln(n), less 1.
 970            First find the smallest extra s.t. n < cutoff[extra] */
 971         for (extra = 0;
 972              extra < sizeof(cutoff) / sizeof(cutoff[0]);
 973              ++extra) {
 974                 if (n < cutoff[extra])
 975                         break;
 976                 /* note that if we fall out of the loop, the value of
 977                    extra still makes *sense*, but may be smaller than
 978                    we would like (but the array has more than ~= 2**31
 979                    elements in this case!) */
 980         }
 981         /* Now k == extra - 1 + CUTOFFBASE.  The smallest value k can
 982            have is CUTOFFBASE-1, so
 983            assert MINSIZE >= 2**(CUTOFFBASE-1) - 1 */
 984         extra = (1 << (extra - 1 + CUTOFFBASE)) - 1;
 985         /* assert extra > 0 and n >= extra */
 986
 987         /* Swap that many values to the start of the array.  The
 988            selection of elements is pseudo-random, but the same on
 989            every run (this is intentional! timing algorithm changes is
 990            a pain if timing varies across runs).  */
 991         {
 992                 unsigned int seed = n / extra;  /* arbitrary */
 993                 unsigned int i;
 994                 for (i = 0; i < (unsigned)extra; ++i) {
 995                         /* j := random int in [i, n) */
 996                         unsigned int j;
 997                         seed = seed * 69069 + 7;
 998                         j = i + seed % (n - i);
 999                         tmp = lo[i]; lo[i] = lo[j]; lo[j] = tmp;
1000                 }
1001         }
1002
1003         /* Recursively sort the preselected pivots. */
1004         if (samplesortslice(lo, lo + extra, compare) < 0)
1005                 goto fail;
1006
1007         top = 0;          /* index of available stack slot */
1008         lo += extra;      /* point to first unknown */
1009         extraOnRight = 0; /* the PPs are at the left end */
1010
1011         /* ----------------------------------------------------------
1012          * Partition [lo, hi), and repeat until out of work.
1013          * --------------------------------------------------------*/
1014         for (;;) {
1015                 /* assert lo <= hi, so n >= 0 */
1016                 n = hi - lo;
1017
1018                 /* We may not want, or may not be able, to partition:
1019                    If n is small, it's quicker to insert.
1020                    If extra is 0, we're out of pivots, and *must* use
1021                    another method.
1022                 */
1023                 if (n < MINPARTITIONSIZE || extra == 0) {
1024                         if (n >= MINSIZE) {
1025                                 /* assert extra == 0
1026                                    This is rare, since the average size
1027                                    of a final block is only about
1028                                    ln(original n). */
1029                                 if (samplesortslice(lo, hi, compare) < 0)
1030                                         goto fail;
1031                         }
1032                         else {
1033                                 /* Binary insertion should be quicker,
1034                                    and we can take advantage of the PPs
1035                                    already being sorted. */
1036                                 if (extraOnRight && extra) {
1037                                         /* swap the PPs to the left end */
1038                                         k = extra;
1039                                         do {
1040                                                 tmp = *lo;
1041                                                 *lo = *hi;
1042                                                 *hi = tmp;
1043                                                 ++lo; ++hi;
1044                                         } while (--k);
1045                                 }
1046                                 if (binarysort(lo - extra, hi, lo,
1047                                                compare) < 0)
1048                                         goto fail;
1049                         }
1050
1051                         /* Find another slice to work on. */
1052                         if (--top < 0)
1053                                 break;   /* no more -- done! */
1054                         lo = stack[top].lo;
1055                         hi = stack[top].hi;
1056                         extra = stack[top].extra;
1057                         extraOnRight = 0;
1058                         if (extra < 0) {
1059                                 extraOnRight = 1;
1060                                 extra = -extra;
1061                         }
1062                         continue;
1063                 }
1064
1065                 /* Pretend the PPs are indexed 0, 1, ..., extra-1.
1066                    Then our preselected pivot is at (extra-1)/2, and we
1067                    want to move the PPs before that to the left end of
1068                    the slice, and the PPs after that to the right end.
1069                    The following section changes extra, lo, hi, and the
1070                    slice such that:
1071                    [lo-extra, lo) contains the smaller PPs.
1072                    *lo == our PP.
1073                    (lo, hi) contains the unknown elements.
1074                    [hi, hi+extra) contains the larger PPs.
1075                 */
1076                 k = extra >>= 1;  /* num PPs to move */
1077                 if (extraOnRight) {
1078                         /* Swap the smaller PPs to the left end.
1079                            Note that this loop actually moves k+1 items:
1080                            the last is our PP */
1081                         do {
1082                                 tmp = *lo; *lo = *hi; *hi = tmp;
1083                                 ++lo; ++hi;
1084                         } while (k--);
1085                 }
1086                 else {
1087                         /* Swap the larger PPs to the right end. */
1088                         while (k--) {
1089                                 --lo; --hi;
1090                                 tmp = *lo; *lo = *hi; *hi = tmp;
1091                         }
1092                 }
1093                 --lo;   /* *lo is now our PP */
1094                 pivot = *lo;
1095
1096                 /* Now an almost-ordinary quicksort partition step.
1097                    Note that most of the time is spent here!
1098                    Only odd thing is that we partition into < and >=,
1099                    instead of the usual <= and >=.  This helps when
1100                    there are lots of duplicates of different values,
1101                    because it eventually tends to make subfiles
1102                    "pure" (all duplicates), and we special-case for
1103                    duplicates later. */
1104                 l = lo + 1;
1105                 r = hi - 1;
1106                 /* assert lo < l < r < hi (small n weeded out above) */
1107
1108                 do {
1109                         /* slide l right, looking for key >= pivot */
1110                         do {
1111                                 SETK(*l, pivot);
1112                                 if (k < 0)
1113                                         ++l;
1114                                 else
1115                                         break;
1116                         } while (l < r);
1117
1118                         /* slide r left, looking for key < pivot */
1119                         while (l < r) {
1120                                 register PyObject *rval = *r--;
1121                                 SETK(rval, pivot);
1122                                 if (k < 0) {
1123                                         /* swap and advance */
1124                                         r[1] = *l;
1125                                         *l++ = rval;
1126                                         break;
1127                                 }
1128                         }
1129
1130                 } while (l < r);
1131
1132                 /* assert lo < r <= l < hi
1133                    assert r == l or r+1 == l
1134                    everything to the left of l is < pivot, and
1135                    everything to the right of r is >= pivot */
1136
1137                 if (l == r) {
1138                         SETK(*r, pivot);
1139                         if (k < 0)
1140                                 ++l;
1141                         else
1142                                 --r;
1143                 }
1144                 /* assert lo <= r and r+1 == l and l <= hi
1145                    assert r == lo or a[r] < pivot
1146                    assert a[lo] is pivot
1147                    assert l == hi or a[l] >= pivot
1148                    Swap the pivot into "the middle", so we can henceforth
1149                    ignore it.
1150                 */
1151                 *lo = *r;
1152                 *r = pivot;
1153
1154                 /* The following is true now, & will be preserved:
1155                    All in [lo,r) are < pivot
1156                    All in [r,l) == pivot (& so can be ignored)
1157                    All in [l,hi) are >= pivot */
1158
1159                 /* Check for duplicates of the pivot.  One compare is
1160                    wasted if there are no duplicates, but can win big
1161                    when there are.
1162                    Tricky: we're sticking to "<" compares, so deduce
1163                    equality indirectly.  We know pivot <= *l, so they're
1164                    equal iff not pivot < *l.
1165                 */
1166                 while (l < hi) {
1167                         /* pivot <= *l known */
1168                         SETK(pivot, *l);
1169                         if (k < 0)
1170                                 break;
1171                         else
1172                                 /* <= and not < implies == */
1173                                 ++l;
1174                 }
1175
1176                 /* assert lo <= r < l <= hi
1177                    Partitions are [lo, r) and [l, hi) */
1178
1179                 /* push fattest first; remember we still have extra PPs
1180                    to the left of the left chunk and to the right of
1181                    the right chunk! */
1182                 /* assert top < STACKSIZE */
1183                 if (r - lo <= hi - l) {
1184                         /* second is bigger */
1185                         stack[top].lo = l;
1186                         stack[top].hi = hi;
1187                         stack[top].extra = -extra;
1188                         hi = r;
1189                         extraOnRight = 0;
1190                 }
1191                 else {
1192                         /* first is bigger */
1193                         stack[top].lo = lo;
1194                         stack[top].hi = r;
1195                         stack[top].extra = extra;
1196                         lo = l;
1197                         extraOnRight = 1;
1198                 }
1199                 ++top;
1200
1201         }   /* end of partitioning loop */
1202
1203         return 0;
1204
1205  fail:
1206         return -1;
1207 }
1208
1209 #undef SETK
1210
1211 staticforward PyTypeObject immutable_list_type;
1212
1213 static PyObject *
1214 listsort(self, compare)
1215         PyListObject *self;
1216         PyObject *compare;
1217 {
1218         int err;
1219
1220         self->ob_type = &immutable_list_type;
1221         err = samplesortslice(self->ob_item,
1222                               self->ob_item + self->ob_size,
1223                               compare);
1224         self->ob_type = &PyList_Type;
1225         if (err < 0)
1226                 return NULL;
1227         Py_INCREF(Py_None);
1228         return Py_None;
1229 }
1230
1231 int
1232 PyList_Sort(v)
1233         PyObject *v;
1234 {
1235         if (v == NULL || !PyList_Check(v)) {
1236                 PyErr_BadInternalCall();
1237                 return -1;
1238         }
1239         v = listsort((PyListObject *)v, (PyObject *)NULL);
1240         if (v == NULL)
1241                 return -1;
1242         Py_DECREF(v);
1243         return 0;
1244 }
1245
1246 static PyObject *
1247 listreverse(self, args)
1248         PyListObject *self;
1249         PyObject *args;
1250 {
1251         register PyObject **p, **q;
1252         register PyObject *tmp;
1253
1254         if (args != NULL) {
1255                 PyErr_BadArgument();
1256                 return NULL;
1257         }
1258
1259         if (self->ob_size > 1) {
1260                 for (p = self->ob_item, q = self->ob_item + self->ob_size - 1;
1261                                                 p < q; p++, q--) {
1262                         tmp = *p;
1263                         *p = *q;
1264                         *q = tmp;
1265                 }
1266         }
1267
1268         Py_INCREF(Py_None);
1269         return Py_None;
1270 }
1271
1272 int
1273 PyList_Reverse(v)
1274         PyObject *v;
1275 {
1276         if (v == NULL || !PyList_Check(v)) {
1277                 PyErr_BadInternalCall();
1278                 return -1;
1279         }
1280         v = listreverse((PyListObject *)v, (PyObject *)NULL);
1281         if (v == NULL)
1282                 return -1;
1283         Py_DECREF(v);
1284         return 0;
1285 }
1286
1287 PyObject *
1288 PyList_AsTuple(v)
1289         PyObject *v;
1290 {
1291         PyObject *w;
1292         PyObject **p;
1293         int n;
1294         if (v == NULL || !PyList_Check(v)) {
1295                 PyErr_BadInternalCall();
1296                 return NULL;
1297         }
1298         n = ((PyListObject *)v)->ob_size;
1299         w = PyTuple_New(n);
1300         if (w == NULL)
1301                 return NULL;
1302         p = ((PyTupleObject *)w)->ob_item;
1303         memcpy((ANY *)p,
1304                (ANY *)((PyListObject *)v)->ob_item,
1305                n*sizeof(PyObject *));
1306         while (--n >= 0) {
1307                 Py_INCREF(*p);
1308                 p++;
1309         }
1310         return w;
1311 }
1312
1313 static PyObject *
1314 listindex(self, args)
1315         PyListObject *self;
1316         PyObject *args;
1317 {
1318         int i;
1319
1320         if (args == NULL) {
1321                 PyErr_BadArgument();
1322                 return NULL;
1323         }
1324         for (i = 0; i < self->ob_size; i++) {
1325                 if (PyObject_Compare(self->ob_item[i], args) == 0)
1326                         return PyInt_FromLong((long)i);
1327                 if (PyErr_Occurred())
1328                         return NULL;
1329         }
1330         PyErr_SetString(PyExc_ValueError, "list.index(x): x not in list");
1331         return NULL;
1332 }
1333
1334 static PyObject *
1335 listcount(self, args)
1336         PyListObject *self;
1337         PyObject *args;
1338 {
1339         int count = 0;
1340         int i;
1341
1342         if (args == NULL) {
1343                 PyErr_BadArgument();
1344                 return NULL;
1345         }
1346         for (i = 0; i < self->ob_size; i++) {
1347                 if (PyObject_Compare(self->ob_item[i], args) == 0)
1348                         count++;
1349                 if (PyErr_Occurred())
1350                         return NULL;
1351         }
1352         return PyInt_FromLong((long)count);
1353 }
1354
1355 static PyObject *
1356 listremove(self, args)
1357         PyListObject *self;
1358         PyObject *args;
1359 {
1360         int i;
1361
1362         if (args == NULL) {
1363                 PyErr_BadArgument();
1364                 return NULL;
1365         }
1366         for (i = 0; i < self->ob_size; i++) {
1367                 if (PyObject_Compare(self->ob_item[i], args) == 0) {
1368                         if (list_ass_slice(self, i, i+1,
1369                                            (PyObject *)NULL) != 0)
1370                                 return NULL;
1371                         Py_INCREF(Py_None);
1372                         return Py_None;
1373                 }
1374                 if (PyErr_Occurred())
1375                         return NULL;
1376         }
1377         PyErr_SetString(PyExc_ValueError, "list.remove(x): x not in list");
1378         return NULL;
1379 }
1380
1381 static char append_doc[] =
1382 "L.append(object) -- append object to end";
1383 static char extend_doc[] =
1384 "L.extend(list) -- extend list by appending list elements";
1385 static char insert_doc[] =
1386 "L.insert(index, object) -- insert object before index";
1387 static char pop_doc[] =
1388 "L.pop([index]) -> item -- remove and return item at index (default last)";
1389 static char remove_doc[] =
1390 "L.remove(value) -- remove first occurrence of value";
1391 static char index_doc[] =
1392 "L.index(value) -> integer -- return index of first occurrence of value";
1393 static char count_doc[] =
1394 "L.count(value) -> integer -- return number of occurrences of value";
1395 static char reverse_doc[] =
1396 "L.reverse() -- reverse *IN PLACE*";
1397 static char sort_doc[] =
1398 "L.sort([cmpfunc]) -- sort *IN PLACE*; if given, cmpfunc(x, y) -> -1, 0, 1";
1399
1400 static PyMethodDef list_methods[] = {
1401         {"append",      (PyCFunction)listappend, 0, append_doc},
1402         {"insert",      (PyCFunction)listinsert, 0, insert_doc},
1403         {"extend",      (PyCFunction)listextend, 1, extend_doc},
1404         {"pop",         (PyCFunction)listpop, 1, pop_doc},
1405         {"remove",      (PyCFunction)listremove, 0, remove_doc},
1406         {"index",       (PyCFunction)listindex, 0, index_doc},
1407         {"count",       (PyCFunction)listcount, 0, count_doc},
1408         {"reverse",     (PyCFunction)listreverse, 0, reverse_doc},
1409         {"sort",        (PyCFunction)listsort, 0, sort_doc},
1410         {NULL,          NULL}           /* sentinel */
1411 };
1412
1413 static PyObject *
1414 list_getattr(f, name)
1415         PyListObject *f;
1416         char *name;
1417 {
1418         return Py_FindMethod(list_methods, (PyObject *)f, name);
1419 }
1420
1421 static PySequenceMethods list_as_sequence = {
1422         (inquiry)list_length, /*sq_length*/
1423         (binaryfunc)list_concat, /*sq_concat*/
1424         (intargfunc)list_repeat, /*sq_repeat*/
1425         (intargfunc)list_item, /*sq_item*/
1426         (intintargfunc)list_slice, /*sq_slice*/
1427         (intobjargproc)list_ass_item, /*sq_ass_item*/
1428         (intintobjargproc)list_ass_slice, /*sq_ass_slice*/
1429 };
1430
1431 PyTypeObject PyList_Type = {
1432         PyObject_HEAD_INIT(&PyType_Type)
1433         0,
1434         "list",
1435         sizeof(PyListObject),
1436         0,
1437         (destructor)list_dealloc, /*tp_dealloc*/
1438         (printfunc)list_print, /*tp_print*/
1439         (getattrfunc)list_getattr, /*tp_getattr*/
1440         0,              /*tp_setattr*/
1441         (cmpfunc)list_compare, /*tp_compare*/
1442         (reprfunc)list_repr, /*tp_repr*/
1443         0,              /*tp_as_number*/
1444         &list_as_sequence,      /*tp_as_sequence*/
1445         0,              /*tp_as_mapping*/
1446 };
1447
1448
1449 /* During a sort, we really can't have anyone modifying the list; it could
1450    cause core dumps.  Thus, we substitute a dummy type that raises an
1451    explanatory exception when a modifying operation is used.  Caveat:
1452    comparisons may behave differently; but I guess it's a bad idea anyway to
1453    compare a list that's being sorted... */
1454
1455 static PyObject *
1456 immutable_list_op(/*No args!*/)
1457 {
1458         PyErr_SetString(PyExc_TypeError,
1459                         "a list cannot be modified while it is being sorted");
1460         return NULL;
1461 }
1462
1463 static PyMethodDef immutable_list_methods[] = {
1464         {"append",      (PyCFunction)immutable_list_op},
1465         {"insert",      (PyCFunction)immutable_list_op},
1466         {"remove",      (PyCFunction)immutable_list_op},
1467         {"index",       (PyCFunction)listindex},
1468         {"count",       (PyCFunction)listcount},
1469         {"reverse",     (PyCFunction)immutable_list_op},
1470         {"sort",        (PyCFunction)immutable_list_op},
1471         {NULL,          NULL}           /* sentinel */
1472 };
1473
1474 static PyObject *
1475 immutable_list_getattr(f, name)
1476         PyListObject *f;
1477         char *name;
1478 {
1479         return Py_FindMethod(immutable_list_methods, (PyObject *)f, name);
1480 }
1481
1482 static int
1483 immutable_list_ass(/*No args!*/)
1484 {
1485         immutable_list_op();
1486         return -1;
1487 }
1488
1489 static PySequenceMethods immutable_list_as_sequence = {
1490         (inquiry)list_length, /*sq_length*/
1491         (binaryfunc)list_concat, /*sq_concat*/
1492         (intargfunc)list_repeat, /*sq_repeat*/
1493         (intargfunc)list_item, /*sq_item*/
1494         (intintargfunc)list_slice, /*sq_slice*/
1495         (intobjargproc)immutable_list_ass, /*sq_ass_item*/
1496         (intintobjargproc)immutable_list_ass, /*sq_ass_slice*/
1497 };
1498
1499 static PyTypeObject immutable_list_type = {
1500         PyObject_HEAD_INIT(&PyType_Type)
1501         0,
1502         "list (immutable, during sort)",
1503         sizeof(PyListObject),
1504         0,
1505         0,              /*tp_dealloc*/ /* Cannot happen */
1506         (printfunc)list_print, /*tp_print*/
1507         (getattrfunc)immutable_list_getattr, /*tp_getattr*/
1508         0,              /*tp_setattr*/
1509         0,              /*tp_compare*/ /* Won't be called */
1510         (reprfunc)list_repr, /*tp_repr*/
1511         0,              /*tp_as_number*/
1512         &immutable_list_as_sequence,    /*tp_as_sequence*/
1513         0,              /*tp_as_mapping*/
1514 };
1515