cpython/Include/longintrepr.h

#ifndef Py_LONGINTREPR_H
#define Py_LONGINTREPR_H
#ifdef __cplusplus
extern "C" {
#endif

/***********************************************************
Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam,
The Netherlands.

                        All Rights Reserved

Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the names of Stichting Mathematisch
Centrum or CWI or Corporation for National Research Initiatives or
CNRI not be used in advertising or publicity pertaining to
distribution of the software without specific, written prior
permission.

While CWI is the initial source for this software, a modified version
is made available by the Corporation for National Research Initiatives
(CNRI) at the Internet address ftp://ftp.python.org.

STICHTING MATHEMATISCH CENTRUM AND CNRI DISCLAIM ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH
CENTRUM OR CNRI BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.

******************************************************************/

/* 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 any way.
   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 */
typedef unsigned long twodigits;
typedef long 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];
};

PyLongObject *_PyLong_New Py_PROTO((int));

#ifdef __cplusplus
}
#endif
#endif /* !Py_LONGINTREPR_H */