cpython/Include/longintrepr.h
Tim Peters 7d3a511a40 Cray J90 fixes for long ints.
This was a convenient excuse to create the pyport.h file recently
discussed!
Please use new Py_ARITHMETIC_RIGHT_SHIFT when right-shifting a
signed int and you *need* sign-extension.  This is #define'd in
pyport.h, keying off new config symbol SIGNED_RIGHT_SHIFT_ZERO_FILLS.
If you're running on a platform that needs that symbol #define'd,
the std tests never would have worked for you (in particular,
at least test_long would have failed).
The autoconfig stuff got added to Python after my Unix days, so
I don't know how that works.  Would someone please look into doing
& testing an auto-config of the SIGNED_RIGHT_SHIFT_ZERO_FILLS
symbol?  It needs to be defined if & only if, e.g., (-1) >> 3 is
not -1.
2000-07-08 04:17:21 +00:00

61 lines
2.2 KiB
C

#ifndef Py_LONGINTREPR_H
#define Py_LONGINTREPR_H
#ifdef __cplusplus
extern "C" {
#endif
/***********************************************************
Copyright (c) 2000, BeOpen.com.
Copyright (c) 1995-2000, Corporation for National Research Initiatives.
Copyright (c) 1990-1995, Stichting Mathematisch Centrum.
All rights reserved.
See the file "Misc/COPYRIGHT" for information on usage and
redistribution of this file, and for a DISCLAIMER OF ALL WARRANTIES.
******************************************************************/
/* 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 fuction takes care of allocating extra memory
so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available. */
struct _longobject {
PyObject_HEAD
int ob_size;
digit ob_digit[1];
};
DL_IMPORT(PyLongObject *) _PyLong_New(int);
#ifdef __cplusplus
}
#endif
#endif /* !Py_LONGINTREPR_H */