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cwr_next(): move invariants out of loops. 

This simplifies and clarifies the code, and gives a small speedup.
This commit is contained in:
Tim Peters 2013-09-03 11:49:31 -05:00
parent c554f725a0
commit 9edb168dd7
1 changed files with 12 additions and 16 deletions
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28
Modules/itertoolsmodule.c
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@ -2713,20 +2713,20 @@ cwr_next(cwrobject *co)
PyObject *result = co->result;
Py_ssize_t n = PyTuple_GET_SIZE(pool);
Py_ssize_t r = co->r;
Py_ssize_t i, j, index;
Py_ssize_t i, index;
if (co->stopped)
return NULL;
if (result == NULL) {
/* On the first pass, initialize result tuple using the indices */
/* On the first pass, initialize result tuple with pool[0] */
result = PyTuple_New(r);
if (result == NULL)
goto empty;
co->result = result;
elem = PyTuple_GET_ITEM(pool, 0);
for (i=0; i<r ; i++) {
index = indices[i];
elem = PyTuple_GET_ITEM(pool, index);
assert(indices[i] == 0);
Py_INCREF(elem);
PyTuple_SET_ITEM(result, i, elem);
}
@ -2749,27 +2749,23 @@ cwr_next(cwrobject *co)
empty tuple is a singleton and cached in PyTuple's freelist. */
assert(r == 0 || Py_REFCNT(result) == 1);
/* Scan indices right-to-left until finding one that is not
* at its maximum (n-1). */
/* Scan indices right-to-left until finding one that is not
* at its maximum (n-1). */
for (i=r-1 ; i >= 0 && indices[i] == n-1; i--)
;
/* If i is negative, then the indices are all at
their maximum value and we're done. */
their maximum value and we're done. */
if (i < 0)
goto empty;
/* Increment the current index which we know is not at its
maximum. Then set all to the right to the same value. */
indices[i]++;
for (j=i+1 ; j<r ; j++)
indices[j] = indices[j-1];
/* Update the result tuple for the new indices
starting with i, the leftmost index that changed */
maximum. Then set all to the right to the same value. */
index = indices[i] + 1;
assert(index < n);
elem = PyTuple_GET_ITEM(pool, index);
for ( ; i<r ; i++) {
index = indices[i];
elem = PyTuple_GET_ITEM(pool, index);
indices[i] = index;
Py_INCREF(elem);
oldelem = PyTuple_GET_ITEM(result, i);
PyTuple_SET_ITEM(result, i, elem);