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Beautify and better document the use of the size_t cast for bounds checking.

This commit is contained in:
Raymond Hettinger 2015-03-02 21:45:02 -08:00
parent 738f805074
commit 3c186ba441
1 changed files with 12 additions and 6 deletions
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18
Modules/_collectionsmodule.c
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@ -765,6 +765,14 @@ deque_clear(dequeobject *deque)
Py_SIZE(deque) == 0);
}
static int
valid_index(Py_ssize_t i, Py_ssize_t limit)
{
/* The cast to size_t let us use just a single comparison
to check whether i is in the range: 0 <= i < limit */
return (size_t) i < (size_t) limit;
}
static PyObject *
deque_item(dequeobject *deque, Py_ssize_t i)
{
@ -772,9 +780,8 @@ deque_item(dequeobject *deque, Py_ssize_t i)
PyObject *item;
Py_ssize_t n, index=i;
if ((size_t)i >= (size_t)Py_SIZE(deque)) {
PyErr_SetString(PyExc_IndexError,
"deque index out of range");
if (!valid_index(i, Py_SIZE(deque))) {
PyErr_SetString(PyExc_IndexError, "deque index out of range");
return NULL;
}
@ -836,9 +843,8 @@ deque_ass_item(dequeobject *deque, Py_ssize_t i, PyObject *v)
block *b;
Py_ssize_t n, len=Py_SIZE(deque), halflen=(len+1)>>1, index=i;
if ((size_t)i >= (size_t)len) {
PyErr_SetString(PyExc_IndexError,
"deque index out of range");
if (!valid_index(i, len)) {
PyErr_SetString(PyExc_IndexError, "deque index out of range");
return -1;
}
if (v == NULL)