mirror of https://github.com/python/cpython
59 lines
1.9 KiB
C
59 lines
1.9 KiB
C
#ifndef Py_LONGINTREPR_H
|
|
#define Py_LONGINTREPR_H
|
|
#ifdef __cplusplus
|
|
extern "C" {
|
|
#endif
|
|
|
|
|
|
/* This is published for the benefit of "friend" marshal.c only. */
|
|
|
|
/* Parameters of the long integer representation.
|
|
These shouldn't have to be changed as C should guarantee that a short
|
|
contains at least 16 bits, but it's made changeable anyway.
|
|
Note: 'digit' should be able to hold 2*MASK+1, and 'twodigits'
|
|
should be able to hold the intermediate results in 'mul'
|
|
(at most MASK << SHIFT).
|
|
Also, x_sub assumes that 'digit' is an unsigned type, and overflow
|
|
is handled by taking the result mod 2**N for some N > SHIFT.
|
|
And, at some places it is assumed that MASK fits in an int, as well. */
|
|
|
|
typedef unsigned short digit;
|
|
typedef unsigned int wdigit; /* digit widened to parameter size */
|
|
#define BASE_TWODIGITS_TYPE long
|
|
typedef unsigned BASE_TWODIGITS_TYPE twodigits;
|
|
typedef BASE_TWODIGITS_TYPE stwodigits; /* signed variant of twodigits */
|
|
|
|
#define SHIFT 15
|
|
#define BASE ((digit)1 << SHIFT)
|
|
#define MASK ((int)(BASE - 1))
|
|
|
|
/* Long integer representation.
|
|
The absolute value of a number is equal to
|
|
SUM(for i=0 through abs(ob_size)-1) ob_digit[i] * 2**(SHIFT*i)
|
|
Negative numbers are represented with ob_size < 0;
|
|
zero is represented by ob_size == 0.
|
|
In a normalized number, ob_digit[abs(ob_size)-1] (the most significant
|
|
digit) is never zero. Also, in all cases, for all valid i,
|
|
0 <= ob_digit[i] <= MASK.
|
|
The allocation function takes care of allocating extra memory
|
|
so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available.
|
|
|
|
CAUTION: Generic code manipulating subtypes of PyVarObject has to
|
|
aware that longs abuse ob_size's sign bit.
|
|
*/
|
|
|
|
struct _longobject {
|
|
PyObject_VAR_HEAD
|
|
digit ob_digit[1];
|
|
};
|
|
|
|
DL_IMPORT(PyLongObject *) _PyLong_New(int);
|
|
|
|
/* Return a copy of src. */
|
|
DL_IMPORT(PyObject *) _PyLong_Copy(PyLongObject *src);
|
|
|
|
#ifdef __cplusplus
|
|
}
|
|
#endif
|
|
#endif /* !Py_LONGINTREPR_H */
|