Objects/memoryobject.c

   1
   2 /* Memoryview object implementation */
   3
   4 #include "Python.h"
   5
   6 static Py_ssize_t
   7 get_shape0(Py_buffer *buf)
   8 {
   9     if (buf->shape != NULL)
  10         return buf->shape[0];
  11     if (buf->ndim == 0)
  12         return 1;
  13     PyErr_SetString(PyExc_TypeError,
  14         "exported buffer does not have any shape information associated "
  15         "to it");
  16     return -1;
  17 }
  18
  19 static void
  20 dup_buffer(Py_buffer *dest, Py_buffer *src)
  21 {
  22     *dest = *src;
  23     if (src->ndim == 1 && src->shape != NULL) {
  24         dest->shape = &(dest->smalltable[0]);
  25         dest->shape[0] = get_shape0(src);
  26     }
  27     if (src->ndim == 1 && src->strides != NULL) {
  28         dest->strides = &(dest->smalltable[1]);
  29         dest->strides[0] = src->strides[0];
  30     }
  31 }
  32
  33 static int
  34 memory_getbuf(PyMemoryViewObject *self, Py_buffer *view, int flags)
  35 {
  36     int res = 0;
  37     /* XXX for whatever reason fixing the flags seems necessary */
  38     if (self->view.readonly)
  39         flags &= ~PyBUF_WRITABLE;
  40     if (self->view.obj != NULL)
  41         res = PyObject_GetBuffer(self->view.obj, view, flags);
  42     if (view)
  43         dup_buffer(view, &self->view);
  44     return res;
  45 }
  46
  47 static void
  48 memory_releasebuf(PyMemoryViewObject *self, Py_buffer *view)
  49 {
  50     PyBuffer_Release(view);
  51 }
  52
  53 PyDoc_STRVAR(memory_doc,
  54 "memoryview(object)\n\
  55 \n\
  56 Create a new memoryview object which references the given object.");
  57
  58 PyObject *
  59 PyMemoryView_FromBuffer(Py_buffer *info)
  60 {
  61     PyMemoryViewObject *mview;
  62
  63     mview = (PyMemoryViewObject *)
  64         PyObject_GC_New(PyMemoryViewObject, &PyMemoryView_Type);
  65     if (mview == NULL)
  66         return NULL;
  67     mview->base = NULL;
  68     dup_buffer(&mview->view, info);
  69     /* NOTE: mview->view.obj should already have been incref'ed as
  70        part of PyBuffer_FillInfo(). */
  71     _PyObject_GC_TRACK(mview);
  72     return (PyObject *)mview;
  73 }
  74
  75 PyObject *
  76 PyMemoryView_FromObject(PyObject *base)
  77 {
  78     PyMemoryViewObject *mview;
  79
  80     if (!PyObject_CheckBuffer(base)) {
  81         PyErr_SetString(PyExc_TypeError,
  82             "cannot make memory view because object does "
  83             "not have the buffer interface");
  84         return NULL;
  85     }
  86
  87     mview = (PyMemoryViewObject *)
  88         PyObject_GC_New(PyMemoryViewObject, &PyMemoryView_Type);
  89     if (mview == NULL)
  90         return NULL;
  91
  92     mview->base = NULL;
  93     if (PyObject_GetBuffer(base, &(mview->view), PyBUF_FULL_RO) < 0) {
  94         Py_DECREF(mview);
  95         return NULL;
  96     }
  97
  98     mview->base = base;
  99     Py_INCREF(base);
 100     _PyObject_GC_TRACK(mview);
 101     return (PyObject *)mview;
 102 }
 103
 104 static PyObject *
 105 memory_new(PyTypeObject *subtype, PyObject *args, PyObject *kwds)
 106 {
 107     PyObject *obj;
 108     static char *kwlist[] = {"object", 0};
 109
 110     if (!PyArg_ParseTupleAndKeywords(args, kwds, "O:memoryview", kwlist,
 111                                      &obj)) {
 112         return NULL;
 113     }
 114
 115     return PyMemoryView_FromObject(obj);
 116 }
 117
 118
 119 static void
 120 _strided_copy_nd(char *dest, char *src, int nd, Py_ssize_t *shape,
 121                  Py_ssize_t *strides, Py_ssize_t itemsize, char fort)
 122 {
 123     int k;
 124     Py_ssize_t outstride;
 125
 126     if (nd==0) {
 127         memcpy(dest, src, itemsize);
 128     }
 129     else if (nd == 1) {
 130         for (k = 0; k<shape[0]; k++) {
 131             memcpy(dest, src, itemsize);
 132             dest += itemsize;
 133             src += strides[0];
 134         }
 135     }
 136     else {
 137         if (fort == 'F') {
 138             /* Copy first dimension first,
 139                second dimension second, etc...
 140                Set up the recursive loop backwards so that final
 141                dimension is actually copied last.
 142             */
 143             outstride = itemsize;
 144             for (k=1; k<nd-1;k++) {
 145                 outstride *= shape[k];
 146             }
 147             for (k=0; k<shape[nd-1]; k++) {
 148                 _strided_copy_nd(dest, src, nd-1, shape,
 149                                  strides, itemsize, fort);
 150                 dest += outstride;
 151                 src += strides[nd-1];
 152             }
 153         }
 154
 155         else {
 156             /* Copy last dimension first,
 157                second-to-last dimension second, etc.
 158                Set up the recursion so that the
 159                first dimension is copied last
 160             */
 161             outstride = itemsize;
 162             for (k=1; k < nd; k++) {
 163                 outstride *= shape[k];
 164             }
 165             for (k=0; k<shape[0]; k++) {
 166                 _strided_copy_nd(dest, src, nd-1, shape+1,
 167                                  strides+1, itemsize,
 168                                  fort);
 169                 dest += outstride;
 170                 src += strides[0];
 171             }
 172         }
 173     }
 174     return;
 175 }
 176
 177 void _add_one_to_index_F(int nd, Py_ssize_t *index, Py_ssize_t *shape);
 178 void _add_one_to_index_C(int nd, Py_ssize_t *index, Py_ssize_t *shape);
 179
 180 static int
 181 _indirect_copy_nd(char *dest, Py_buffer *view, char fort)
 182 {
 183     Py_ssize_t *indices;
 184     int k;
 185     Py_ssize_t elements;
 186     char *ptr;
 187     void (*func)(int, Py_ssize_t *, Py_ssize_t *);
 188
 189     if (view->ndim > PY_SSIZE_T_MAX / sizeof(Py_ssize_t)) {
 190         PyErr_NoMemory();
 191         return -1;
 192     }
 193
 194     indices = (Py_ssize_t *)PyMem_Malloc(sizeof(Py_ssize_t)*view->ndim);
 195     if (indices == NULL) {
 196         PyErr_NoMemory();
 197         return -1;
 198     }
 199     for (k=0; k<view->ndim;k++) {
 200         indices[k] = 0;
 201     }
 202
 203     elements = 1;
 204     for (k=0; k<view->ndim; k++) {
 205         elements *= view->shape[k];
 206     }
 207     if (fort == 'F') {
 208         func = _add_one_to_index_F;
 209     }
 210     else {
 211         func = _add_one_to_index_C;
 212     }
 213     while (elements--) {
 214         func(view->ndim, indices, view->shape);
 215         ptr = PyBuffer_GetPointer(view, indices);
 216         memcpy(dest, ptr, view->itemsize);
 217         dest += view->itemsize;
 218     }
 219
 220     PyMem_Free(indices);
 221     return 0;
 222 }
 223
 224 /*
 225    Get a the data from an object as a contiguous chunk of memory (in
 226    either 'C' or 'F'ortran order) even if it means copying it into a
 227    separate memory area.
 228
 229    Returns a new reference to a Memory view object.  If no copy is needed,
 230    the memory view object points to the original memory and holds a
 231    lock on the original.  If a copy is needed, then the memory view object
 232    points to a brand-new Bytes object (and holds a memory lock on it).
 233
 234    buffertype
 235
 236    PyBUF_READ  buffer only needs to be read-only
 237    PyBUF_WRITE buffer needs to be writable (give error if not contiguous)
 238    PyBUF_SHADOW buffer needs to be writable so shadow it with
 239                 a contiguous buffer if it is not. The view will point to
 240                 the shadow buffer which can be written to and then
 241                 will be copied back into the other buffer when the memory
 242                 view is de-allocated.  While the shadow buffer is
 243                 being used, it will have an exclusive write lock on
 244                 the original buffer.
 245  */
 246
 247 PyObject *
 248 PyMemoryView_GetContiguous(PyObject *obj, int buffertype, char fort)
 249 {
 250     PyMemoryViewObject *mem;
 251     PyObject *bytes;
 252     Py_buffer *view;
 253     int flags;
 254     char *dest;
 255
 256     if (!PyObject_CheckBuffer(obj)) {
 257         PyErr_SetString(PyExc_TypeError,
 258                         "object does not have the buffer interface");
 259         return NULL;
 260     }
 261
 262     mem = PyObject_GC_New(PyMemoryViewObject, &PyMemoryView_Type);
 263     if (mem == NULL)
 264         return NULL;
 265
 266     view = &mem->view;
 267     flags = PyBUF_FULL_RO;
 268     switch(buffertype) {
 269     case PyBUF_WRITE:
 270         flags = PyBUF_FULL;
 271         break;
 272     }
 273
 274     if (PyObject_GetBuffer(obj, view, flags) != 0) {
 275         Py_DECREF(mem);
 276         return NULL;
 277     }
 278
 279     if (PyBuffer_IsContiguous(view, fort)) {
 280         /* no copy needed */
 281         Py_INCREF(obj);
 282         mem->base = obj;
 283         _PyObject_GC_TRACK(mem);
 284         return (PyObject *)mem;
 285     }
 286     /* otherwise a copy is needed */
 287     if (buffertype == PyBUF_WRITE) {
 288         Py_DECREF(mem);
 289         PyErr_SetString(PyExc_BufferError,
 290                         "writable contiguous buffer requested "
 291                         "for a non-contiguousobject.");
 292         return NULL;
 293     }
 294     bytes = PyBytes_FromStringAndSize(NULL, view->len);
 295     if (bytes == NULL) {
 296         Py_DECREF(mem);
 297         return NULL;
 298     }
 299     dest = PyBytes_AS_STRING(bytes);
 300     /* different copying strategy depending on whether
 301        or not any pointer de-referencing is needed
 302     */
 303     /* strided or in-direct copy */
 304     if (view->suboffsets==NULL) {
 305         _strided_copy_nd(dest, view->buf, view->ndim, view->shape,
 306                          view->strides, view->itemsize, fort);
 307     }
 308     else {
 309         if (_indirect_copy_nd(dest, view, fort) < 0) {
 310             Py_DECREF(bytes);
 311             Py_DECREF(mem);
 312             return NULL;
 313         }
 314     }
 315     if (buffertype == PyBUF_SHADOW) {
 316         /* return a shadowed memory-view object */
 317         view->buf = dest;
 318         mem->base = PyTuple_Pack(2, obj, bytes);
 319         Py_DECREF(bytes);
 320         if (mem->base == NULL) {
 321             Py_DECREF(mem);
 322             return NULL;
 323         }
 324     }
 325     else {
 326         PyBuffer_Release(view);  /* XXX ? */
 327         /* steal the reference */
 328         mem->base = bytes;
 329     }
 330     _PyObject_GC_TRACK(mem);
 331     return (PyObject *)mem;
 332 }
 333
 334
 335 static PyObject *
 336 memory_format_get(PyMemoryViewObject *self)
 337 {
 338     return PyUnicode_FromString(self->view.format);
 339 }
 340
 341 static PyObject *
 342 memory_itemsize_get(PyMemoryViewObject *self)
 343 {
 344     return PyLong_FromSsize_t(self->view.itemsize);
 345 }
 346
 347 static PyObject *
 348 _IntTupleFromSsizet(int len, Py_ssize_t *vals)
 349 {
 350     int i;
 351     PyObject *o;
 352     PyObject *intTuple;
 353
 354     if (vals == NULL) {
 355         Py_INCREF(Py_None);
 356         return Py_None;
 357     }
 358     intTuple = PyTuple_New(len);
 359     if (!intTuple) return NULL;
 360     for(i=0; i<len; i++) {
 361         o = PyLong_FromSsize_t(vals[i]);
 362         if (!o) {
 363             Py_DECREF(intTuple);
 364             return NULL;
 365         }
 366         PyTuple_SET_ITEM(intTuple, i, o);
 367     }
 368     return intTuple;
 369 }
 370
 371 static PyObject *
 372 memory_shape_get(PyMemoryViewObject *self)
 373 {
 374     return _IntTupleFromSsizet(self->view.ndim, self->view.shape);
 375 }
 376
 377 static PyObject *
 378 memory_strides_get(PyMemoryViewObject *self)
 379 {
 380     return _IntTupleFromSsizet(self->view.ndim, self->view.strides);
 381 }
 382
 383 static PyObject *
 384 memory_suboffsets_get(PyMemoryViewObject *self)
 385 {
 386     return _IntTupleFromSsizet(self->view.ndim, self->view.suboffsets);
 387 }
 388
 389 static PyObject *
 390 memory_readonly_get(PyMemoryViewObject *self)
 391 {
 392     return PyBool_FromLong(self->view.readonly);
 393 }
 394
 395 static PyObject *
 396 memory_ndim_get(PyMemoryViewObject *self)
 397 {
 398     return PyLong_FromLong(self->view.ndim);
 399 }
 400
 401 static PyGetSetDef memory_getsetlist[] ={
 402     {"format",          (getter)memory_format_get,      NULL, NULL},
 403     {"itemsize",        (getter)memory_itemsize_get,    NULL, NULL},
 404     {"shape",           (getter)memory_shape_get,       NULL, NULL},
 405     {"strides",         (getter)memory_strides_get,     NULL, NULL},
 406     {"suboffsets",      (getter)memory_suboffsets_get,  NULL, NULL},
 407     {"readonly",        (getter)memory_readonly_get,    NULL, NULL},
 408     {"ndim",            (getter)memory_ndim_get,        NULL, NULL},
 409     {NULL, NULL, NULL, NULL},
 410 };
 411
 412
 413 static PyObject *
 414 memory_tobytes(PyMemoryViewObject *self, PyObject *noargs)
 415 {
 416     Py_buffer view;
 417     PyObject *res;
 418
 419     if (PyObject_GetBuffer((PyObject *)self, &view, PyBUF_FULL) < 0)
 420         return NULL;
 421
 422     res = PyBytes_FromStringAndSize(NULL, view.len);
 423     PyBuffer_ToContiguous(PyBytes_AS_STRING(res), &view, view.len, 'C');
 424     PyBuffer_Release(&view);
 425     return res;
 426 }
 427
 428 /* TODO: rewrite this function using the struct module to unpack
 429    each buffer item */
 430
 431 static PyObject *
 432 memory_tolist(PyMemoryViewObject *mem, PyObject *noargs)
 433 {
 434     Py_buffer *view = &(mem->view);
 435     Py_ssize_t i;
 436     PyObject *res, *item;
 437     char *buf;
 438
 439     if (strcmp(view->format, "B") || view->itemsize != 1) {
 440         PyErr_SetString(PyExc_NotImplementedError,
 441                 "tolist() only supports byte views");
 442         return NULL;
 443     }
 444     if (view->ndim != 1) {
 445         PyErr_SetString(PyExc_NotImplementedError,
 446                 "tolist() only supports one-dimensional objects");
 447         return NULL;
 448     }
 449     res = PyList_New(view->len);
 450     if (res == NULL)
 451         return NULL;
 452     buf = view->buf;
 453     for (i = 0; i < view->len; i++) {
 454         item = PyInt_FromLong((unsigned char) *buf);
 455         if (item == NULL) {
 456             Py_DECREF(res);
 457             return NULL;
 458         }
 459         PyList_SET_ITEM(res, i, item);
 460         buf++;
 461     }
 462     return res;
 463 }
 464
 465 static PyMethodDef memory_methods[] = {
 466     {"tobytes", (PyCFunction)memory_tobytes, METH_NOARGS, NULL},
 467     {"tolist", (PyCFunction)memory_tolist, METH_NOARGS, NULL},
 468     {NULL,          NULL}           /* sentinel */
 469 };
 470
 471
 472 static void
 473 memory_dealloc(PyMemoryViewObject *self)
 474 {
 475     _PyObject_GC_UNTRACK(self);
 476     if (self->view.obj != NULL) {
 477         if (self->base && PyTuple_Check(self->base)) {
 478             /* Special case when first element is generic object
 479                with buffer interface and the second element is a
 480                contiguous "shadow" that must be copied back into
 481                the data areay of the first tuple element before
 482                releasing the buffer on the first element.
 483             */
 484
 485             PyObject_CopyData(PyTuple_GET_ITEM(self->base,0),
 486                               PyTuple_GET_ITEM(self->base,1));
 487
 488             /* The view member should have readonly == -1 in
 489                this instance indicating that the memory can
 490                be "locked" and was locked and will be unlocked
 491                again after this call.
 492             */
 493             PyBuffer_Release(&(self->view));
 494         }
 495         else {
 496             PyBuffer_Release(&(self->view));
 497         }
 498         Py_CLEAR(self->base);
 499     }
 500     PyObject_GC_Del(self);
 501 }
 502
 503 static PyObject *
 504 memory_repr(PyMemoryViewObject *self)
 505 {
 506     return PyUnicode_FromFormat("<memory at %p>", self);
 507 }
 508
 509 /* Sequence methods */
 510 static Py_ssize_t
 511 memory_length(PyMemoryViewObject *self)
 512 {
 513     return get_shape0(&self->view);
 514 }
 515
 516 /* Alternate version of memory_subcript that only accepts indices.
 517    Used by PySeqIter_New().
 518 */
 519 static PyObject *
 520 memory_item(PyMemoryViewObject *self, Py_ssize_t result)
 521 {
 522     Py_buffer *view = &(self->view);
 523
 524     if (view->ndim == 0) {
 525         PyErr_SetString(PyExc_IndexError,
 526                         "invalid indexing of 0-dim memory");
 527         return NULL;
 528     }
 529     if (view->ndim == 1) {
 530         /* Return a bytes object */
 531         char *ptr;
 532         ptr = (char *)view->buf;
 533         if (result < 0) {
 534             result += get_shape0(view);
 535         }
 536         if ((result < 0) || (result >= get_shape0(view))) {
 537             PyErr_SetString(PyExc_IndexError,
 538                                 "index out of bounds");
 539             return NULL;
 540         }
 541         if (view->strides == NULL)
 542             ptr += view->itemsize * result;
 543         else
 544             ptr += view->strides[0] * result;
 545         if (view->suboffsets != NULL &&
 546             view->suboffsets[0] >= 0) {
 547             ptr = *((char **)ptr) + view->suboffsets[0];
 548         }
 549         return PyBytes_FromStringAndSize(ptr, view->itemsize);
 550     } else {
 551         /* Return a new memory-view object */
 552         Py_buffer newview;
 553         memset(&newview, 0, sizeof(newview));
 554         /* XXX:  This needs to be fixed so it actually returns a sub-view */
 555         return PyMemoryView_FromBuffer(&newview);
 556     }
 557 }
 558
 559 /*
 560   mem[obj] returns a bytes object holding the data for one element if
 561            obj fully indexes the memory view or another memory-view object
 562            if it does not.
 563
 564            0-d memory-view objects can be referenced using ... or () but
 565            not with anything else.
 566  */
 567 static PyObject *
 568 memory_subscript(PyMemoryViewObject *self, PyObject *key)
 569 {
 570     Py_buffer *view;
 571     view = &(self->view);
 572
 573     if (view->ndim == 0) {
 574         if (key == Py_Ellipsis ||
 575             (PyTuple_Check(key) && PyTuple_GET_SIZE(key)==0)) {
 576             Py_INCREF(self);
 577             return (PyObject *)self;
 578         }
 579         else {
 580             PyErr_SetString(PyExc_IndexError,
 581                                 "invalid indexing of 0-dim memory");
 582             return NULL;
 583         }
 584     }
 585     if (PyIndex_Check(key)) {
 586         Py_ssize_t result;
 587         result = PyNumber_AsSsize_t(key, NULL);
 588         if (result == -1 && PyErr_Occurred())
 589                 return NULL;
 590         return memory_item(self, result);
 591     }
 592     else if (PySlice_Check(key)) {
 593         Py_ssize_t start, stop, step, slicelength;
 594
 595         if (PySlice_GetIndicesEx((PySliceObject*)key, get_shape0(view),
 596                                  &start, &stop, &step, &slicelength) < 0) {
 597             return NULL;
 598         }
 599
 600         if (step == 1 && view->ndim == 1) {
 601             Py_buffer newview;
 602             void *newbuf = (char *) view->buf
 603                                     + start * view->itemsize;
 604             int newflags = view->readonly
 605                     ? PyBUF_CONTIG_RO : PyBUF_CONTIG;
 606
 607             /* XXX There should be an API to create a subbuffer */
 608             if (view->obj != NULL) {
 609                 if (PyObject_GetBuffer(view->obj, &newview, newflags) == -1)
 610                     return NULL;
 611             }
 612             else {
 613                 newview = *view;
 614             }
 615             newview.buf = newbuf;
 616             newview.len = slicelength * newview.itemsize;
 617             newview.format = view->format;
 618             newview.shape = &(newview.smalltable[0]);
 619             newview.shape[0] = slicelength;
 620             newview.strides = &(newview.itemsize);
 621             return PyMemoryView_FromBuffer(&newview);
 622         }
 623         PyErr_SetNone(PyExc_NotImplementedError);
 624         return NULL;
 625     }
 626     PyErr_Format(PyExc_TypeError,
 627         "cannot index memory using \"%.200s\"",
 628         key->ob_type->tp_name);
 629     return NULL;
 630 }
 631
 632
 633 /* Need to support assigning memory if we can */
 634 static int
 635 memory_ass_sub(PyMemoryViewObject *self, PyObject *key, PyObject *value)
 636 {
 637     Py_ssize_t start, len, bytelen, i;
 638     Py_buffer srcview;
 639     Py_buffer *view = &(self->view);
 640     char *srcbuf, *destbuf;
 641
 642     if (view->readonly) {
 643         PyErr_SetString(PyExc_TypeError,
 644             "cannot modify read-only memory");
 645         return -1;
 646     }
 647     if (view->ndim != 1) {
 648         PyErr_SetNone(PyExc_NotImplementedError);
 649         return -1;
 650     }
 651     if (PyIndex_Check(key)) {
 652         start = PyNumber_AsSsize_t(key, NULL);
 653         if (start == -1 && PyErr_Occurred())
 654             return -1;
 655         if (start < 0) {
 656             start += get_shape0(view);
 657         }
 658         if ((start < 0) || (start >= get_shape0(view))) {
 659             PyErr_SetString(PyExc_IndexError,
 660                             "index out of bounds");
 661             return -1;
 662         }
 663         len = 1;
 664     }
 665     else if (PySlice_Check(key)) {
 666         Py_ssize_t stop, step;
 667
 668         if (PySlice_GetIndicesEx((PySliceObject*)key, get_shape0(view),
 669                          &start, &stop, &step, &len) < 0) {
 670             return -1;
 671         }
 672         if (step != 1) {
 673             PyErr_SetNone(PyExc_NotImplementedError);
 674             return -1;
 675         }
 676     }
 677     else {
 678         PyErr_Format(PyExc_TypeError,
 679             "cannot index memory using \"%.200s\"",
 680             key->ob_type->tp_name);
 681         return -1;
 682     }
 683     if (PyObject_GetBuffer(value, &srcview, PyBUF_CONTIG_RO) == -1) {
 684         return -1;
 685     }
 686     /* XXX should we allow assignment of different item sizes
 687        as long as the byte length is the same?
 688        (e.g. assign 2 shorts to a 4-byte slice) */
 689     if (srcview.itemsize != view->itemsize) {
 690         PyErr_Format(PyExc_TypeError,
 691             "mismatching item sizes for \"%.200s\" and \"%.200s\"",
 692             view->obj->ob_type->tp_name, srcview.obj->ob_type->tp_name);
 693         goto _error;
 694     }
 695     bytelen = len * view->itemsize;
 696     if (bytelen != srcview.len) {
 697         PyErr_SetString(PyExc_ValueError,
 698             "cannot modify size of memoryview object");
 699         goto _error;
 700     }
 701     /* Do the actual copy */
 702     destbuf = (char *) view->buf + start * view->itemsize;
 703     srcbuf = (char *) srcview.buf;
 704     if (destbuf + bytelen < srcbuf || srcbuf + bytelen < destbuf)
 705         /* No overlapping */
 706         memcpy(destbuf, srcbuf, bytelen);
 707     else if (destbuf < srcbuf) {
 708         /* Copy in ascending order */
 709         for (i = 0; i < bytelen; i++)
 710             destbuf[i] = srcbuf[i];
 711     }
 712     else {
 713         /* Copy in descencing order */
 714         for (i = bytelen - 1; i >= 0; i--)
 715             destbuf[i] = srcbuf[i];
 716     }
 717
 718     PyBuffer_Release(&srcview);
 719     return 0;
 720
 721 _error:
 722     PyBuffer_Release(&srcview);
 723     return -1;
 724 }
 725
 726 static PyObject *
 727 memory_richcompare(PyObject *v, PyObject *w, int op)
 728 {
 729     Py_buffer vv, ww;
 730     int equal = 0;
 731     PyObject *res;
 732
 733     vv.obj = NULL;
 734     ww.obj = NULL;
 735     if (op != Py_EQ && op != Py_NE)
 736         goto _notimpl;
 737     if (PyObject_GetBuffer(v, &vv, PyBUF_CONTIG_RO) == -1) {
 738         PyErr_Clear();
 739         goto _notimpl;
 740     }
 741     if (PyObject_GetBuffer(w, &ww, PyBUF_CONTIG_RO) == -1) {
 742         PyErr_Clear();
 743         goto _notimpl;
 744     }
 745
 746     if (vv.itemsize != ww.itemsize || vv.len != ww.len)
 747         goto _end;
 748
 749     equal = !memcmp(vv.buf, ww.buf, vv.len);
 750
 751 _end:
 752     PyBuffer_Release(&vv);
 753     PyBuffer_Release(&ww);
 754     if ((equal && op == Py_EQ) || (!equal && op == Py_NE))
 755         res = Py_True;
 756     else
 757         res = Py_False;
 758     Py_INCREF(res);
 759     return res;
 760
 761 _notimpl:
 762     PyBuffer_Release(&vv);
 763     PyBuffer_Release(&ww);
 764     Py_INCREF(Py_NotImplemented);
 765     return Py_NotImplemented;
 766 }
 767
 768
 769 static int
 770 memory_traverse(PyMemoryViewObject *self, visitproc visit, void *arg)
 771 {
 772     if (self->base != NULL)
 773         Py_VISIT(self->base);
 774     if (self->view.obj != NULL)
 775         Py_VISIT(self->view.obj);
 776     return 0;
 777 }
 778
 779 static int
 780 memory_clear(PyMemoryViewObject *self)
 781 {
 782     Py_CLEAR(self->base);
 783     PyBuffer_Release(&self->view);
 784     return 0;
 785 }
 786
 787
 788 /* As mapping */
 789 static PyMappingMethods memory_as_mapping = {
 790     (lenfunc)memory_length,               /* mp_length */
 791     (binaryfunc)memory_subscript,         /* mp_subscript */
 792     (objobjargproc)memory_ass_sub,        /* mp_ass_subscript */
 793 };
 794
 795 static PySequenceMethods memory_as_sequence = {
 796         0,                                  /* sq_length */
 797         0,                                  /* sq_concat */
 798         0,                                  /* sq_repeat */
 799         (ssizeargfunc)memory_item,          /* sq_item */
 800 };
 801
 802 /* Buffer methods */
 803 static PyBufferProcs memory_as_buffer = {
 804     0,                                    /* bf_getreadbuffer */
 805     0,                                    /* bf_getwritebuffer */
 806     0,                                    /* bf_getsegcount */
 807     0,                                    /* bf_getcharbuffer */
 808     (getbufferproc)memory_getbuf,         /* bf_getbuffer */
 809     (releasebufferproc)memory_releasebuf, /* bf_releasebuffer */
 810 };
 811
 812
 813 PyTypeObject PyMemoryView_Type = {
 814     PyVarObject_HEAD_INIT(&PyType_Type, 0)
 815     "memoryview",
 816     sizeof(PyMemoryViewObject),
 817     0,
 818     (destructor)memory_dealloc,               /* tp_dealloc */
 819     0,                                        /* tp_print */
 820     0,                                        /* tp_getattr */
 821     0,                                        /* tp_setattr */
 822     0,                                        /* tp_compare */
 823     (reprfunc)memory_repr,                    /* tp_repr */
 824     0,                                        /* tp_as_number */
 825     &memory_as_sequence,                      /* tp_as_sequence */
 826     &memory_as_mapping,                       /* tp_as_mapping */
 827     0,                                        /* tp_hash */
 828     0,                                        /* tp_call */
 829     0,                                        /* tp_str */
 830     PyObject_GenericGetAttr,                  /* tp_getattro */
 831     0,                                        /* tp_setattro */
 832     &memory_as_buffer,                        /* tp_as_buffer */
 833     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
 834         Py_TPFLAGS_HAVE_NEWBUFFER,            /* tp_flags */
 835     memory_doc,                               /* tp_doc */
 836     (traverseproc)memory_traverse,            /* tp_traverse */
 837     (inquiry)memory_clear,                    /* tp_clear */
 838     memory_richcompare,                       /* tp_richcompare */
 839     0,                                        /* tp_weaklistoffset */
 840     0,                                        /* tp_iter */
 841     0,                                        /* tp_iternext */
 842     memory_methods,                           /* tp_methods */
 843     0,                                        /* tp_members */
 844     memory_getsetlist,                        /* tp_getset */
 845     0,                                        /* tp_base */
 846     0,                                        /* tp_dict */
 847     0,                                        /* tp_descr_get */
 848     0,                                        /* tp_descr_set */
 849     0,                                        /* tp_dictoffset */
 850     0,                                        /* tp_init */
 851     0,                                        /* tp_alloc */
 852     memory_new,                               /* tp_new */
 853 };