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Issue #4258: Make it possible to use 30-bit digits for PyLongs:

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- new configure option --enable-big-digits
 - new structseq sys.int_info giving information about the internal format
By default, 30-bit digits are enabled on 64-bit machines but
disabled on 32-bit machines.
This commit is contained in:
Mark Dickinson 2009-03-18 20:06:12 +00:00
parent e7f45b8e59
commit bd7926478d
15 changed files with 865 additions and 68 deletions
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62
Objects/longobject.c
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@ -4,6 +4,7 @@
#include "Python.h"
#include "longintrepr.h"
#include "structseq.h"
#include <ctype.h>
#include <stddef.h>
@ -204,6 +205,7 @@ PyLong_FromLong(long ival)
return (PyObject*)v;
}
#if PyLONG_SHIFT==15
/* 2 digits */
if (!(abs_ival >> 2*PyLong_SHIFT)) {
v = _PyLong_New(2);
@ -216,6 +218,7 @@ PyLong_FromLong(long ival)
}
return (PyObject*)v;
}
#endif
/* Larger numbers: loop to determine number of digits */
t = abs_ival;
@ -2864,10 +2867,20 @@ long_mul(PyLongObject *a, PyLongObject *b)
CHECK_BINOP(a, b);
/* fast path for single-digit multiplication */
if (ABS(Py_SIZE(a)) <= 1 && ABS(Py_SIZE(b)) <= 1) {
PyObject *r;
r = PyLong_FromLong(MEDIUM_VALUE(a)*MEDIUM_VALUE(b));
return r;
stwodigits v = (stwodigits)(MEDIUM_VALUE(a)) * MEDIUM_VALUE(b);
#ifdef HAVE_LONG_LONG
return PyLong_FromLongLong((PY_LONG_LONG)v);
#else
/* if we don't have long long then we're almost certainly
using 15-bit digits, so v will fit in a long. In the
unlikely event that we're using 30-bit digits on a platform
without long long, a large v will just cause us to fall
through to the general multiplication code below. */
if (v >= LONG_MIN && v <= LONG_MAX)
return PyLong_FromLong((long)v);
#endif
}
z = k_mul(a, b);
@ -3991,6 +4004,45 @@ PyTypeObject PyLong_Type = {
PyObject_Del, /* tp_free */
};
static PyTypeObject Int_InfoType;
PyDoc_STRVAR(int_info__doc__,
"sys.int_info\n\
\n\
A struct sequence that holds information about Python's\n\
internal representation of integers. The attributes are read only.");
static PyStructSequence_Field int_info_fields[] = {
{"bits_per_digit", "size of a digit in bits"},
{"sizeof_digit", "size in bytes of the C type used to "
"represent a digit"},
{NULL, NULL}
};
static PyStructSequence_Desc int_info_desc = {
"sys.int_info", /* name */
int_info__doc__, /* doc */
int_info_fields, /* fields */
2 /* number of fields */
};
PyObject *
PyLong_GetInfo(void)
{
PyObject* int_info;
int field = 0;
int_info = PyStructSequence_New(&Int_InfoType);
if (int_info == NULL)
return NULL;
PyStructSequence_SET_ITEM(int_info, field++, PyLong_FromLong(PyLong_SHIFT));
PyStructSequence_SET_ITEM(int_info, field++, PyLong_FromLong(sizeof(digit)));
if (PyErr_Occurred()) {
Py_CLEAR(int_info);
return NULL;
}
return int_info;
}
int
_PyLong_Init(void)
{
@ -4023,6 +4075,10 @@ _PyLong_Init(void)
v->ob_digit[0] = abs(ival);
}
#endif
/* initialize int_info */
if (Int_InfoType.tp_name == 0)
PyStructSequence_InitType(&Int_InfoType, &int_info_desc);
return 1;
}