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Upon insertion, if memory runs out, the deque was left in a corrupted state. 

deque_item(): a performance bug: the linked list of blocks was followed
from the left in most cases, because the test (i < (deque->len >> 1)) was
after "i %= BLOCKLEN".

deque_clear(): replaced a call to deque_len() with deque->len; not sure what
this call was here for, nor if all compilers under the sun would inline it.

deque_traverse(): I belive that it could be called by the GC when the deque
has leftblock==rightblock==NULL, because it is tracked before the first block
is allocated (though closely before).  Still, a C extension module subclassing
deque could provide its own tp_alloc that could trigger a GC collection after
the PyObject_GC_Track()...

deque_richcompare(): rewrote to cleanly check for end-of-iterations instead of
relying on deque.__iter__().next() to succeed exactly len(deque) times -- an
assumption which can break if deques are subclassed.  Added a test.

I wonder if the length should be explicitely bounded to INT_MAX, with
OverflowErrors, as in listobject.c.  On 64-bit machines, adding more than
INT_MAX in the deque will result in trouble.  (Note to anyone/me fixing
this: carefully check for overflows if len is close to INT_MAX in the
following functions: deque_rotate(), deque_item(), deque_ass_item())
This commit is contained in:
Armin Rigo 2004-10-02 13:59:34 +00:00
parent 565ea5ae37
commit 974d757af1
2 changed files with 43 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
Lib/test/test_deque.py
View File

@ -479,6 +479,15 @@ class TestSubclass(unittest.TestCase):
d = None
self.assertRaises(ReferenceError, str, p)
def test_strange_subclass(self):
class X(deque):
def __iter__(self):
return iter([])
d1 = X([1,2,3])
d2 = X([4,5,6])
d1 == d2 # not clear if this is supposed to be True or False,
# but it used to give a SystemError
#==============================================================================
libreftest = """

68
Modules/collectionsmodule.c
View File

@ -108,19 +108,19 @@ deque_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
static PyObject *
deque_append(dequeobject *deque, PyObject *item)
{
deque->rightindex++;
deque->len++;
deque->state++;
if (deque->rightindex == BLOCKLEN) {
if (deque->rightindex == BLOCKLEN-1) {
block *b = newblock(deque->rightblock, NULL);
if (b == NULL)
return NULL;
assert(deque->rightblock->rightlink == NULL);
deque->rightblock->rightlink = b;
deque->rightblock = b;
deque->rightindex = 0;
deque->rightindex = -1;
}
Py_INCREF(item);
deque->len++;
deque->rightindex++;
deque->rightblock->data[deque->rightindex] = item;
Py_RETURN_NONE;
}
@ -130,19 +130,19 @@ PyDoc_STRVAR(append_doc, "Add an element to the right side of the deque.");
static PyObject *
deque_appendleft(dequeobject *deque, PyObject *item)
{
deque->leftindex--;
deque->len++;
deque->state++;
if (deque->leftindex == -1) {
if (deque->leftindex == 0) {
block *b = newblock(NULL, deque->leftblock);
if (b == NULL)
return NULL;
assert(deque->leftblock->leftlink == NULL);
deque->leftblock->leftlink = b;
deque->leftblock = b;
deque->leftindex = BLOCKLEN - 1;
deque->leftindex = BLOCKLEN;
}
Py_INCREF(item);
deque->len++;
deque->leftindex--;
deque->leftblock->data[deque->leftindex] = item;
Py_RETURN_NONE;
}
@ -233,10 +233,8 @@ deque_extend(dequeobject *deque, PyObject *iterable)
return NULL;
while ((item = PyIter_Next(it)) != NULL) {
deque->rightindex++;
deque->len++;
deque->state++;
if (deque->rightindex == BLOCKLEN) {
if (deque->rightindex == BLOCKLEN-1) {
block *b = newblock(deque->rightblock, NULL);
if (b == NULL) {
Py_DECREF(item);
@ -246,8 +244,10 @@ deque_extend(dequeobject *deque, PyObject *iterable)
assert(deque->rightblock->rightlink == NULL);
deque->rightblock->rightlink = b;
deque->rightblock = b;
deque->rightindex = 0;
deque->rightindex = -1;
}
deque->len++;
deque->rightindex++;
deque->rightblock->data[deque->rightindex] = item;
}
Py_DECREF(it);
@ -269,10 +269,8 @@ deque_extendleft(dequeobject *deque, PyObject *iterable)
return NULL;
while ((item = PyIter_Next(it)) != NULL) {
deque->leftindex--;
deque->len++;
deque->state++;
if (deque->leftindex == -1) {
if (deque->leftindex == 0) {
block *b = newblock(NULL, deque->leftblock);
if (b == NULL) {
Py_DECREF(item);
@ -282,8 +280,10 @@ deque_extendleft(dequeobject *deque, PyObject *iterable)
assert(deque->leftblock->leftlink == NULL);
deque->leftblock->leftlink = b;
deque->leftblock = b;
deque->leftindex = BLOCKLEN - 1;
deque->leftindex = BLOCKLEN;
}
deque->len++;
deque->leftindex--;
deque->leftblock->data[deque->leftindex] = item;
}
Py_DECREF(it);
@ -365,7 +365,7 @@ deque_item(dequeobject *deque, int i)
{
block *b;
PyObject *item;
int n;
int n, index=i;
if (i < 0 || i >= deque->len) {
PyErr_SetString(PyExc_IndexError,
@ -383,7 +383,7 @@ deque_item(dequeobject *deque, int i)
i += deque->leftindex;
n = i / BLOCKLEN;
i %= BLOCKLEN;
if (i < (deque->len >> 1)) {
if (index < (deque->len >> 1)) {
b = deque->leftblock;
while (n--)
b = b->rightlink;
@ -514,7 +514,6 @@ deque_traverse(dequeobject *deque, visitproc visit, void *arg)
int index;
int indexlo = deque->leftindex;
assert(deque->leftblock != NULL);
for (b = deque->leftblock; b != NULL; b = b->rightlink) {
const int indexhi = b == deque->rightblock ?
deque->rightindex :
@ -642,7 +641,7 @@ static PyObject *
deque_richcompare(PyObject *v, PyObject *w, int op)
{
PyObject *it1=NULL, *it2=NULL, *x, *y;
int i, b, vs, ws, minlen, cmp=-1;
int b, vs, ws, cmp=-1;
if (!PyObject_TypeCheck(v, &deque_type) ||
!PyObject_TypeCheck(w, &deque_type)) {
@ -673,16 +672,13 @@ deque_richcompare(PyObject *v, PyObject *w, int op)
it2 = PyObject_GetIter(w);
if (it2 == NULL)
goto done;
minlen = (vs < ws) ? vs : ws;
for (i=0 ; i < minlen ; i++) {
for (;;) {
x = PyIter_Next(it1);
if (x == NULL)
if (x == NULL && PyErr_Occurred())
goto done;
y = PyIter_Next(it2);
if (y == NULL) {
Py_DECREF(x);
goto done;
}
if (x == NULL || y == NULL)
break;
b = PyObject_RichCompareBool(x, y, Py_EQ);
if (b == 0) {
cmp = PyObject_RichCompareBool(x, y, op);
@ -695,14 +691,18 @@ deque_richcompare(PyObject *v, PyObject *w, int op)
if (b == -1)
goto done;
}
/* Elements are equal through minlen. The longest input is the greatest */
/* We reached the end of one deque or both */
Py_XDECREF(x);
Py_XDECREF(y);
if (PyErr_Occurred())
goto done;
switch (op) {
case Py_LT: cmp = vs < ws; break;
case Py_LE: cmp = vs <= ws; break;
case Py_EQ: cmp = vs == ws; break;
case Py_NE: cmp = vs != ws; break;
case Py_GT: cmp = vs > ws; break;
case Py_GE: cmp = vs >= ws; break;
case Py_LT: cmp = y != NULL; break; /* if w was longer */
case Py_LE: cmp = x == NULL; break; /* if v was not longer */
case Py_EQ: cmp = x == y; break; /* if we reached the end of both */
case Py_NE: cmp = x != y; break; /* if one deque continues */
case Py_GT: cmp = x != NULL; break; /* if v was longer */
case Py_GE: cmp = y == NULL; break; /* if w was not longer */
}
done: