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.
> Here are timings:
>
> (py33) zbook:mytests $ python3.3 -m timeit -n 50 -r 5 -s "from
> mytests.unicode_index import test_1" "test_1()"
> 50 loops, best of 5: 152 msec per loop
> (py33) zbook:mytests $ python3.3 -m timeit -n 50 -r 5 -s "from
> mytests.unicode_index import test_2" "test_2()"
> 50 loops, best of 5: 86.5 msec per loop
> (py33) zbook:mytests $ python3.3 -m timeit -n 50 -r 5 -s "from
> mytests.unicode_index import test_3" "test_3()"
> 50 loops, best of 5: 86.5 msec per loop
>
> So your suggestion would be preferable.
Nice. Yes, looks like it' worth it.
Stefan
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