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// Collects code that was copied in from cpython, for a couple of different reasons:
// * We wanted to modify it to produce a more efficient version for our uses
// * We needed to call it and it was static :(
// * We wanted to call it and needed to backport it
#include "pythonsupport.h"
#if CPY_3_12_FEATURES
// Slow path of CPyLong_AsSsize_tAndOverflow (non-inlined)
Py_ssize_t
CPyLong_AsSsize_tAndOverflow_(PyObject *vv, int *overflow)
{
PyLongObject *v = (PyLongObject *)vv;
size_t x, prev;
Py_ssize_t res;
Py_ssize_t i;
int sign;
*overflow = 0;
res = -1;
i = CPY_LONG_TAG(v);
sign = 1;
x = 0;
if (i & CPY_SIGN_NEGATIVE) {
sign = -1;
}
i >>= CPY_NON_SIZE_BITS;
while (--i >= 0) {
prev = x;
x = (x << PyLong_SHIFT) + CPY_LONG_DIGIT(v, i);
if ((x >> PyLong_SHIFT) != prev) {
*overflow = sign;
goto exit;
}
}
/* Haven't lost any bits, but casting to long requires extra
* care.
*/
if (x <= (size_t)CPY_TAGGED_MAX) {
res = (Py_ssize_t)x * sign;
}
else if (sign < 0 && x == CPY_TAGGED_ABS_MIN) {
res = CPY_TAGGED_MIN;
}
else {
*overflow = sign;
/* res is already set to -1 */
}
exit:
return res;
}
#else
// Slow path of CPyLong_AsSsize_tAndOverflow (non-inlined, Python 3.11 and earlier)
Py_ssize_t
CPyLong_AsSsize_tAndOverflow_(PyObject *vv, int *overflow)
{
/* This version by Tim Peters */
PyLongObject *v = (PyLongObject *)vv;
size_t x, prev;
Py_ssize_t res;
Py_ssize_t i;
int sign;
*overflow = 0;
res = -1;
i = Py_SIZE(v);
sign = 1;
x = 0;
if (i < 0) {
sign = -1;
i = -(i);
}
while (--i >= 0) {
prev = x;
x = (x << PyLong_SHIFT) + CPY_LONG_DIGIT(v, i);
if ((x >> PyLong_SHIFT) != prev) {
*overflow = sign;
goto exit;
}
}
/* Haven't lost any bits, but casting to long requires extra
* care.
*/
if (x <= (size_t)CPY_TAGGED_MAX) {
res = (Py_ssize_t)x * sign;
}
else if (sign < 0 && x == CPY_TAGGED_ABS_MIN) {
res = CPY_TAGGED_MIN;
}
else {
*overflow = sign;
/* res is already set to -1 */
}
exit:
return res;
}
#endif
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