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Miscellaneous refactorings 

* Add comment to the maxlen structure entry about the meaning of maxlen == -1
* Factor-out code common to deque_append(left) and deque_extend(left)
* Factor inner-loop in deque_clear() to use only 1 test per loop instead of 2
* Tighten inner-loops for deque_item() and deque_ass_item() so that the
  compiler can combine the decrement and test into a single step.
This commit is contained in:
Raymond Hettinger 2016-01-24 09:12:06 -08:00
parent 1aa78938b0
commit d84ec225bd
1 changed files with 58 additions and 65 deletions
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123
Modules/_collectionsmodule.c
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@ -81,7 +81,7 @@ typedef struct {
Py_ssize_t leftindex; /* 0 <= leftindex < BLOCKLEN */
Py_ssize_t rightindex; /* 0 <= rightindex < BLOCKLEN */
size_t state; /* incremented whenever the indices move */
Py_ssize_t maxlen;
Py_ssize_t maxlen; /* maxlen is -1 for unbounded deques */
PyObject *weakreflist;
} dequeobject;
@ -264,13 +264,13 @@ PyDoc_STRVAR(popleft_doc, "Remove and return the leftmost element.");
#define NEEDS_TRIM(deque, maxlen) ((size_t)(maxlen) < (size_t)(Py_SIZE(deque)))
static PyObject *
deque_append(dequeobject *deque, PyObject *item)
int
deque_append_internal(dequeobject *deque, PyObject *item, Py_ssize_t maxlen)
{
if (deque->rightindex == BLOCKLEN - 1) {
block *b = newblock();
if (b == NULL)
return NULL;
return -1;
b->leftlink = deque->rightblock;
CHECK_END(deque->rightblock->rightlink);
deque->rightblock->rightlink = b;
@ -279,27 +279,35 @@ deque_append(dequeobject *deque, PyObject *item)
deque->rightindex = -1;
}
Py_SIZE(deque)++;
Py_INCREF(item);
deque->rightindex++;
deque->rightblock->data[deque->rightindex] = item;
if (NEEDS_TRIM(deque, deque->maxlen)) {
if (NEEDS_TRIM(deque, maxlen)) {
PyObject *olditem = deque_popleft(deque, NULL);
Py_DECREF(olditem);
} else {
deque->state++;
}
return 0;
}
static PyObject *
deque_append(dequeobject *deque, PyObject *item)
{
Py_INCREF(item);
if (deque_append_internal(deque, item, deque->maxlen) < 0)
return NULL;
Py_RETURN_NONE;
}
PyDoc_STRVAR(append_doc, "Add an element to the right side of the deque.");
static PyObject *
deque_appendleft(dequeobject *deque, PyObject *item)
int
deque_appendleft_internal(dequeobject *deque, PyObject *item, Py_ssize_t maxlen)
{
if (deque->leftindex == 0) {
block *b = newblock();
if (b == NULL)
return NULL;
return -1;
b->rightlink = deque->leftblock;
CHECK_END(deque->leftblock->leftlink);
deque->leftblock->leftlink = b;
@ -308,7 +316,6 @@ deque_appendleft(dequeobject *deque, PyObject *item)
deque->leftindex = BLOCKLEN;
}
Py_SIZE(deque)++;
Py_INCREF(item);
deque->leftindex--;
deque->leftblock->data[deque->leftindex] = item;
if (NEEDS_TRIM(deque, deque->maxlen)) {
@ -317,6 +324,15 @@ deque_appendleft(dequeobject *deque, PyObject *item)
} else {
deque->state++;
}
return 0;
}
static PyObject *
deque_appendleft(dequeobject *deque, PyObject *item)
{
Py_INCREF(item);
if (deque_appendleft_internal(deque, item, deque->maxlen) < 0)
return NULL;
Py_RETURN_NONE;
}
@ -387,28 +403,10 @@ deque_extend(dequeobject *deque, PyObject *iterable)
iternext = *Py_TYPE(it)->tp_iternext;
while ((item = iternext(it)) != NULL) {
if (deque->rightindex == BLOCKLEN - 1) {
block *b = newblock();
if (b == NULL) {
Py_DECREF(item);
Py_DECREF(it);
return NULL;
}
b->leftlink = deque->rightblock;
CHECK_END(deque->rightblock->rightlink);
deque->rightblock->rightlink = b;
deque->rightblock = b;
MARK_END(b->rightlink);
deque->rightindex = -1;
}
Py_SIZE(deque)++;
deque->rightindex++;
deque->rightblock->data[deque->rightindex] = item;
if (NEEDS_TRIM(deque, maxlen)) {
PyObject *olditem = deque_popleft(deque, NULL);
Py_DECREF(olditem);
} else {
deque->state++;
if (deque_append_internal(deque, item, maxlen) < 0) {
Py_DECREF(item);
Py_DECREF(it);
return NULL;
}
}
return finalize_iterator(it);
@ -452,28 +450,10 @@ deque_extendleft(dequeobject *deque, PyObject *iterable)
iternext = *Py_TYPE(it)->tp_iternext;
while ((item = iternext(it)) != NULL) {
if (deque->leftindex == 0) {
block *b = newblock();
if (b == NULL) {
Py_DECREF(item);
Py_DECREF(it);
return NULL;
}
b->rightlink = deque->leftblock;
CHECK_END(deque->leftblock->leftlink);
deque->leftblock->leftlink = b;
deque->leftblock = b;
MARK_END(b->leftlink);
deque->leftindex = BLOCKLEN;
}
Py_SIZE(deque)++;
deque->leftindex--;
deque->leftblock->data[deque->leftindex] = item;
if (NEEDS_TRIM(deque, maxlen)) {
PyObject *olditem = deque_pop(deque, NULL);
Py_DECREF(olditem);
} else {
deque->state++;
if (deque_appendleft_internal(deque, item, maxlen) < 0) {
Py_DECREF(item);
Py_DECREF(it);
return NULL;
}
}
return finalize_iterator(it);
@ -565,8 +545,9 @@ deque_clear(dequeobject *deque)
block *prevblock;
block *leftblock;
Py_ssize_t leftindex;
Py_ssize_t n;
Py_ssize_t n, m;
PyObject *item;
PyObject **itemptr, **limit;
if (Py_SIZE(deque) == 0)
return;
@ -608,17 +589,25 @@ deque_clear(dequeobject *deque)
/* Now the old size, leftblock, and leftindex are disconnected from
the empty deque and we can use them to decref the pointers.
*/
while (n--) {
item = leftblock->data[leftindex];
Py_DECREF(item);
leftindex++;
if (leftindex == BLOCKLEN && n) {
itemptr = &leftblock->data[leftindex];
m = (BLOCKLEN - leftindex > n) ? n : BLOCKLEN - leftindex;
limit = &leftblock->data[leftindex + m];
n -= m;
while (1) {
if (itemptr == limit) {
if (n == 0)
break;
CHECK_NOT_END(leftblock->rightlink);
prevblock = leftblock;
leftblock = leftblock->rightlink;
leftindex = 0;
itemptr = leftblock->data;
m = (n > BLOCKLEN) ? BLOCKLEN : n;
limit = &leftblock->data[m];
n -= m;
freeblock(prevblock);
}
item = *(itemptr++);
Py_DECREF(item);
}
CHECK_END(leftblock->rightlink);
freeblock(leftblock);
@ -1185,14 +1174,16 @@ deque_item(dequeobject *deque, Py_ssize_t i)
i = (Py_ssize_t)((size_t) i % BLOCKLEN);
if (index < (Py_SIZE(deque) >> 1)) {
b = deque->leftblock;
while (n--)
n++;
while (--n)
b = b->rightlink;
} else {
n = (Py_ssize_t)(
((size_t)(deque->leftindex + Py_SIZE(deque) - 1))
/ BLOCKLEN - n);
b = deque->rightblock;
while (n--)
n++;
while (--n)
b = b->leftlink;
}
}
@ -1235,14 +1226,16 @@ deque_ass_item(dequeobject *deque, Py_ssize_t i, PyObject *v)
i = (Py_ssize_t)((size_t) i % BLOCKLEN);
if (index <= halflen) {
b = deque->leftblock;
while (n--)
n++;
while (--n)
b = b->rightlink;
} else {
n = (Py_ssize_t)(
((size_t)(deque->leftindex + Py_SIZE(deque) - 1))
/ BLOCKLEN - n);
b = deque->rightblock;
while (n--)
n++;
while (--n)
b = b->leftlink;
}
Py_INCREF(v);