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long_format(): Easy speedup for output bases that aren't a power of 2 (in 

particular, str(long) and repr(long) use base 10, and that gets a factor
of 4 speedup).  Another factor of 2 can be gotten by refactoring divrem1 to
support in-place division, but that started getting messy so I'm leaving
that out.
This commit is contained in:
Tim Peters 2001-07-13 02:59:26 +00:00
parent a3253d70bc
commit fad225f1ba
1 changed files with 26 additions and 9 deletions
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35
Objects/longobject.c
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@ -811,28 +811,45 @@ long_format(PyObject *aa, int base, int addL)
}
}
else {
/* Not 0, and base not a power of 2. Divide repeatedly by
base, but for speed use the highest power of base that
fits in a digit. */
digit powbase = base; /* powbase == base ** power */
int power = 1;
for (;;) {
unsigned long newpow = powbase * (unsigned long)base;
if (newpow >> SHIFT) /* doesn't fit in a digit */
break;
powbase = (digit)newpow;
++power;
}
Py_INCREF(a);
do {
int ntostore = power;
digit rem;
PyLongObject *temp = divrem1(a, (digit)base, &rem);
PyLongObject *temp = divrem1(a, powbase, &rem);
Py_DECREF(a);
if (temp == NULL) {
Py_DECREF(a);
Py_DECREF(str);
return NULL;
}
if (rem < 10)
rem += '0';
else
rem += 'A'-10;
assert(p > PyString_AS_STRING(str));
*--p = (char) rem;
Py_DECREF(a);
a = temp;
SIGCHECK({
Py_DECREF(a);
Py_DECREF(str);
return NULL;
})
while (--ntostore >= 0) {
digit nextrem = (digit)(rem / base);
char c = (char)(rem - nextrem * base);
assert(p > PyString_AS_STRING(str));
c += (c < 10) ? '0' : 'A'-10;
*--p = c;
rem = nextrem;
if (a->ob_size == 0 && rem == 0)
break; /* skip leading zeroes */
}
} while (ABS(a->ob_size) != 0);
Py_DECREF(a);
}