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Merge 3.3 into default.

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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 11:52:59 -05:00
commit c6171e49ab
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; PyObject *result = co->result;
Py_ssize_t n = PyTuple_GET_SIZE(pool); Py_ssize_t n = PyTuple_GET_SIZE(pool);
Py_ssize_t r = co->r; Py_ssize_t r = co->r;
Py_ssize_t i, j, index; Py_ssize_t i, index;
if (co->stopped) if (co->stopped)
return NULL; return NULL;
if (result == 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); result = PyTuple_New(r);
if (result == NULL) if (result == NULL)
goto empty; goto empty;
co->result = result; co->result = result;
elem = PyTuple_GET_ITEM(pool, 0);
for (i=0; i<r ; i++) { for (i=0; i<r ; i++) {
index = indices[i]; assert(indices[i] == 0);
elem = PyTuple_GET_ITEM(pool, index);
Py_INCREF(elem); Py_INCREF(elem);
PyTuple_SET_ITEM(result, i, 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. */ empty tuple is a singleton and cached in PyTuple's freelist. */
assert(r == 0 || Py_REFCNT(result) == 1); assert(r == 0 || Py_REFCNT(result) == 1);
/* Scan indices right-to-left until finding one that is not /* Scan indices right-to-left until finding one that is not
* at its maximum (n-1). */ * at its maximum (n-1). */
for (i=r-1 ; i >= 0 && indices[i] == n-1; i--) for (i=r-1 ; i >= 0 && indices[i] == n-1; i--)
; ;
/* If i is negative, then the indices are all at /* 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) if (i < 0)
goto empty; goto empty;
/* Increment the current index which we know is not at its /* Increment the current index which we know is not at its
maximum. Then set all to the right to the same value. */ maximum. Then set all to the right to the same value. */
indices[i]++; index = indices[i] + 1;
for (j=i+1 ; j<r ; j++) assert(index < n);
indices[j] = indices[j-1]; elem = PyTuple_GET_ITEM(pool, index);
/* Update the result tuple for the new indices
starting with i, the leftmost index that changed */
for ( ; i<r ; i++) { for ( ; i<r ; i++) {
index = indices[i]; indices[i] = index;
elem = PyTuple_GET_ITEM(pool, index);
Py_INCREF(elem); Py_INCREF(elem);
oldelem = PyTuple_GET_ITEM(result, i); oldelem = PyTuple_GET_ITEM(result, i);
PyTuple_SET_ITEM(result, i, elem); PyTuple_SET_ITEM(result, i, elem);