static enum divmod_result
i_divmod(register long x, register long y,
long *p_xdivy, long *p_xmody)
{
long xdivy, xmody;
if (y == 0) {
PyErr_SetString(PyExc_ZeroDivisionError,
"integer division or modulo by zero");
return DIVMOD_ERROR;
}
/* (-sys.maxint-1)/-1 is the only overflow case. */
if (y == -1 && x < 0 && x == -x) {
if (err_ovf("integer division"))
return DIVMOD_ERROR;
return DIVMOD_OVERFLOW;
}
xdivy = x / y;
xmody = x - xdivy * y;
/* If the signs of x and y differ, and the remainder is non-0,
* C89 doesn't define whether xdivy is now the floor or the
* ceiling of the infinitely precise quotient. We want the floor,
* and we have it iff the remainder's sign matches y's.
*/
if (xmody && ((y ^ xmody) < 0) /* i.e. and signs differ */) {
xmody += y;
--xdivy;
assert(xmody && ((y ^ xmody) >= 0));
}
*p_xdivy = xdivy;
*p_xmody = xmody;
return DIVMOD_OK;
}
static PyObject *
int_sub(PyIntObject *v, PyIntObject *w)
{
register long a, b, x;
a = v->ob_ival;
b = w->ob_ival;
x = a - b;
if ((x^a) < 0 && (x^~b) < 0)
return err_ovf("integer subtraction");
return PyInt_FromLong(x);
}
static PyObject *
int_add(PyIntObject *v, PyIntObject *w)
{
register long a, b, x;
a = v->ob_ival;
b = w->ob_ival;
x = a + b;
if ((x^a) < 0 && (x^b) < 0)
return err_ovf("integer addition");
return PyInt_FromLong(x);
}
static PyObject *
int_neg(PyIntObject *v)
{
register long a, x;
a = v->ob_ival;
x = -a;
if (a < 0 && x < 0) {
if (err_ovf("integer negation"))
return NULL;
return PyNumber_Negative(PyLong_FromLong(a));
}
return PyInt_FromLong(x);
}
static PyObject *
int_add(PyIntObject *v, PyIntObject *w)
{
register long a, b, x;
CONVERT_TO_LONG(v, a);
CONVERT_TO_LONG(w, b);
x = a + b;
if ((x^a) >= 0 || (x^b) >= 0)
return PyInt_FromLong(x);
if (err_ovf("integer addition"))
return NULL;
return PyLong_Type.tp_as_number->nb_add((PyObject *)v, (PyObject *)w);
}
static PyObject *
int_pow(PyIntObject *v, PyIntObject *w, PyIntObject *z)
{
register long iv, iw, iz=0, ix, temp, prev;
CONVERT_TO_LONG(v, iv);
CONVERT_TO_LONG(w, iw);
if (iw < 0) {
if ((PyObject *)z != Py_None) {
PyErr_SetString(PyExc_TypeError, "pow() 2nd argument "
"cannot be negative when 3rd argument specified");
return NULL;
}
/* Return a float. This works because we know that
this calls float_pow() which converts its
arguments to double. */
return PyFloat_Type.tp_as_number->nb_power(
(PyObject *)v, (PyObject *)w, (PyObject *)z);
}
if ((PyObject *)z != Py_None) {
CONVERT_TO_LONG(z, iz);
if (iz == 0) {
PyErr_SetString(PyExc_ValueError,
"pow() 3rd argument cannot be 0");
return NULL;
}
}
/*
* XXX: The original exponentiation code stopped looping
* when temp hit zero; this code will continue onwards
* unnecessarily, but at least it won't cause any errors.
* Hopefully the speed improvement from the fast exponentiation
* will compensate for the slight inefficiency.
* XXX: Better handling of overflows is desperately needed.
*/
temp = iv;
ix = 1;
while (iw > 0) {
prev = ix; /* Save value for overflow check */
if (iw & 1) {
ix = ix*temp;
if (temp == 0)
break; /* Avoid ix / 0 */
if (ix / temp != prev) {
if (err_ovf("integer exponentiation"))
return NULL;
return PyLong_Type.tp_as_number->nb_power(
(PyObject *)v,
(PyObject *)w,
(PyObject *)z);
}
}
iw >>= 1; /* Shift exponent down by 1 bit */
if (iw==0) break;
prev = temp;
temp *= temp; /* Square the value of temp */
if (prev!=0 && temp/prev!=prev) {
if (err_ovf("integer exponentiation"))
return NULL;
return PyLong_Type.tp_as_number->nb_power(
(PyObject *)v, (PyObject *)w, (PyObject *)z);
}
if (iz) {
/* If we did a multiplication, perform a modulo */
ix = ix % iz;
temp = temp % iz;
}
}
if (iz) {
long div, mod;
switch (i_divmod(ix, iz, &div, &mod)) {
case DIVMOD_OK:
ix = mod;
break;
case DIVMOD_OVERFLOW:
return PyLong_Type.tp_as_number->nb_power(
(PyObject *)v, (PyObject *)w, (PyObject *)z);
default:
return NULL;
}
}
return PyInt_FromLong(ix);
}
static PyObject *
int_mul(PyObject *v, PyObject *w)
{
long a, b;
long longprod; /* a*b in native long arithmetic */
double doubled_longprod; /* (double)longprod */
double doubleprod; /* (double)a * (double)b */
if (USE_SQ_REPEAT(v)) {
repeat:
/* sequence * int */
a = PyInt_AsLong(w);
#if LONG_MAX != INT_MAX
if (a > INT_MAX) {
PyErr_SetString(PyExc_ValueError,
"sequence repeat count too large");
return NULL;
}
else if (a < INT_MIN)
a = INT_MIN;
/* XXX Why don't I either
- set a to -1 whenever it's negative (after all,
sequence repeat usually treats negative numbers
as zero(); or
- raise an exception when it's less than INT_MIN?
I'm thinking about a hypothetical use case where some
sequence type might use a negative value as a flag of
some kind. In those cases I don't want to break the
code by mapping all negative values to -1. But I also
don't want to break e.g. []*(-sys.maxint), which is
perfectly safe, returning []. As a compromise, I do
map out-of-range negative values.
*/
#endif
return (*v->ob_type->tp_as_sequence->sq_repeat)(v, a);
}
if (USE_SQ_REPEAT(w)) {
PyObject *tmp = v;
v = w;
w = tmp;
goto repeat;
}
CONVERT_TO_LONG(v, a);
CONVERT_TO_LONG(w, b);
longprod = a * b;
doubleprod = (double)a * (double)b;
doubled_longprod = (double)longprod;
/* Fast path for normal case: small multiplicands, and no info
is lost in either method. */
if (doubled_longprod == doubleprod)
return PyInt_FromLong(longprod);
/* Somebody somewhere lost info. Close enough, or way off? Note
that a != 0 and b != 0 (else doubled_longprod == doubleprod == 0).
The difference either is or isn't significant compared to the
true value (of which doubleprod is a good approximation).
*/
{
const double diff = doubled_longprod - doubleprod;
const double absdiff = diff >= 0.0 ? diff : -diff;
const double absprod = doubleprod >= 0.0 ? doubleprod :
-doubleprod;
/* absdiff/absprod <= 1/32 iff
32 * absdiff <= absprod -- 5 good bits is "close enough" */
if (32.0 * absdiff <= absprod)
return PyInt_FromLong(longprod);
else if (err_ovf("integer multiplication"))
return NULL;
else
return PyLong_Type.tp_as_number->nb_multiply(v, w);
}
}
