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PyLong_From{Unsigned,}Long: count the # of digits first, so no more space

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is allocated than needed (used to allocate 80 bytes of digit space no
matter how small the long input).  This also runs faster, at least on 32-
bit boxes.
This commit is contained in:
Tim Peters 2001-06-14 04:56:19 +00:00
parent ff70d3c8d4
commit ce9de2f79a
1 changed files with 41 additions and 21 deletions
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62
Objects/longobject.c
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@ -57,21 +57,34 @@ _PyLong_New(int size)
PyObject *
PyLong_FromLong(long ival)
{
/* Assume a C long fits in at most 5 'digits' */
/* Works on both 32- and 64-bit machines */
PyLongObject *v = _PyLong_New(5);
PyLongObject *v;
unsigned long t; /* unsigned so >> doesn't propagate sign bit */
int ndigits = 0;
int negative = 0;
if (ival < 0) {
ival = -ival;
negative = 1;
}
/* Count the number of Python digits.
We used to pick 5 ("big enough for anything"), but that's a
waste of time and space given that 5*15 = 75 bits are rarely
needed. */
t = (unsigned long)ival;
while (t) {
++ndigits;
t >>= SHIFT;
}
v = _PyLong_New(ndigits);
if (v != NULL) {
unsigned long t = ival;
int i;
if (ival < 0) {
t = -ival;
v->ob_size = -(v->ob_size);
}
for (i = 0; i < 5; i++) {
v->ob_digit[i] = (digit) (t & MASK);
digit *p = v->ob_digit;
v->ob_size = negative ? -ndigits : ndigits;
t = (unsigned long)ival;
while (t) {
*p++ = (digit)(t & MASK);
t >>= SHIFT;
}
v = long_normalize(v);
}
return (PyObject *)v;
}
@ -81,17 +94,24 @@ PyLong_FromLong(long ival)
PyObject *
PyLong_FromUnsignedLong(unsigned long ival)
{
/* Assume a C long fits in at most 5 'digits' */
/* Works on both 32- and 64-bit machines */
PyLongObject *v = _PyLong_New(5);
PyLongObject *v;
unsigned long t;
int ndigits = 0;
/* Count the number of Python digits. */
t = (unsigned long)ival;
while (t) {
++ndigits;
t >>= SHIFT;
}
v = _PyLong_New(ndigits);
if (v != NULL) {
unsigned long t = ival;
int i;
for (i = 0; i < 5; i++) {
v->ob_digit[i] = (digit) (t & MASK);
t >>= SHIFT;
digit *p = v->ob_digit;
v->ob_size = ndigits;
while (ival) {
*p++ = (digit)(ival & MASK);
ival >>= SHIFT;
}
v = long_normalize(v);
}
return (PyObject *)v;
}