2013/3/1 Stefan Behnel <stefan...@behnel.de>:
> ZS, 28.02.2013 21:07:
>> 2013/2/28 Stefan Behnel:
>>>> This allows to write unicode text parsing code almost at C speed
>>>> mostly in python (+ .pxd defintions).
>>>
>>> I suggest simply adding a constant flag argument to the existing function
>>> that states if checking should be done or not. Inlining will let the C
>>> compiler drop the corresponding code, which may or may nor make it a little
>>> faster.
>>
>> static inline Py_UCS4 unicode_char2(PyObject* ustring, Py_ssize_t i, int
>> flag) {
>> Py_ssize_t length;
>> #if CYTHON_PEP393_ENABLED
>> if (PyUnicode_READY(ustring) < 0) return (Py_UCS4)-1;
>> #endif
>> if (flag) {
>> length = __Pyx_PyUnicode_GET_LENGTH(ustring);
>> if ((0 <= i) & (i < length)) {
>> return __Pyx_PyUnicode_READ_CHAR(ustring, i);
>> } else if ((-length <= i) & (i < 0)) {
>> return __Pyx_PyUnicode_READ_CHAR(ustring, i + length);
>> } else {
>> PyErr_SetString(PyExc_IndexError, "string index out of range");
>> return (Py_UCS4)-1;
>> }
>> } else {
>> return __Pyx_PyUnicode_READ_CHAR(ustring, i);
>> }
>> }
>
> I think you could even pass in two flags, one for wraparound and one for
> boundscheck, and then just evaluate them appropriately in the existing "if"
> tests above. That should allow both features to be supported independently
> in a fast way.
>
Intresting, could C compilers in optimization mode to eliminate unused
evaluation path in nested if statements with constant conditional
expressions?
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