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Issue #11004: Repair edge case in deque.count().

Browse source 
(Reviewed by Georg Brandl.)

Also made similar changes to deque.reverse() though this wasn't
strictly necessary (the edge case cannot occur with two pointers
moving to meet in the middle).  Making the change in reverse()
was more a matter of future-proofing.
This commit is contained in:
Raymond Hettinger 2011-01-25 21:32:39 +00:00
parent 5543e81352
commit 512d2cc643
3 changed files with 18 additions and 4 deletions
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11
Modules/_collectionsmodule.c
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@ -485,7 +485,8 @@ deque_reverse(dequeobject *deque, PyObject *unused)
/* Advance left block/index pair */
leftindex++;
if (leftindex == BLOCKLEN) {
assert (leftblock->rightlink != NULL);
if (leftblock->rightlink == NULL)
break;
leftblock = leftblock->rightlink;
leftindex = 0;
}
@ -493,7 +494,8 @@ deque_reverse(dequeobject *deque, PyObject *unused)
/* Step backwards with the right block/index pair */
rightindex--;
if (rightindex == -1) {
assert (rightblock->leftlink != NULL);
if (rightblock->leftlink == NULL)
break;
rightblock = rightblock->leftlink;
rightindex = BLOCKLEN - 1;
}
@ -509,7 +511,7 @@ deque_count(dequeobject *deque, PyObject *v)
{
block *leftblock = deque->leftblock;
Py_ssize_t leftindex = deque->leftindex;
Py_ssize_t n = (deque->len);
Py_ssize_t n = deque->len;
Py_ssize_t i;
Py_ssize_t count = 0;
PyObject *item;
@ -533,7 +535,8 @@ deque_count(dequeobject *deque, PyObject *v)
/* Advance left block/index pair */
leftindex++;
if (leftindex == BLOCKLEN) {
assert (leftblock->rightlink != NULL);
if (leftblock->rightlink == NULL) /* can occur when i==n-1 */
break;
leftblock = leftblock->rightlink;
leftindex = 0;
}