Include/longintrepr.h

   1 #ifndef Py_LONGINTREPR_H
   2 #define Py_LONGINTREPR_H
   3 #ifdef __cplusplus
   4 extern "C" {
   5 #endif
   6
   7 /***********************************************************
   8 Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam,
   9 The Netherlands.
  10
  11                         All Rights Reserved
  12
  13 Permission to use, copy, modify, and distribute this software and its
  14 documentation for any purpose and without fee is hereby granted,
  15 provided that the above copyright notice appear in all copies and that
  16 both that copyright notice and this permission notice appear in
  17 supporting documentation, and that the names of Stichting Mathematisch
  18 Centrum or CWI not be used in advertising or publicity pertaining to
  19 distribution of the software without specific, written prior permission.
  20
  21 STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO
  22 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
  23 FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE
  24 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  25 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  26 ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  27 OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  28
  29 ******************************************************************/
  30
  31 /* This is published for the benefit of "friend" marshal.c only. */
  32
  33 /* Parameters of the long integer representation.
  34    These shouldn't have to be changed as C should guarantee that a short
  35    contains at least 16 bits, but it's made changeable any way.
  36    Note: 'digit' should be able to hold 2*MASK+1, and 'twodigits'
  37    should be able to hold the intermediate results in 'mul'
  38    (at most MASK << SHIFT).
  39    Also, x_sub assumes that 'digit' is an unsigned type, and overflow
  40    is handled by taking the result mod 2**N for some N > SHIFT.
  41    And, at some places it is assumed that MASK fits in an int, as well. */
  42
  43 typedef unsigned short digit;
  44 typedef unsigned int wdigit; /* digit widened to parameter size */
  45 typedef unsigned long twodigits;
  46 typedef long stwodigits; /* signed variant of twodigits */
  47
  48 #define SHIFT   15
  49 #define BASE    ((digit)1 << SHIFT)
  50 #define MASK    ((int)(BASE - 1))
  51
  52 /* Long integer representation.
  53    The absolute value of a number is equal to
  54         SUM(for i=0 through abs(ob_size)-1) ob_digit[i] * 2**(SHIFT*i)
  55    Negative numbers are represented with ob_size < 0;
  56    zero is represented by ob_size == 0.
  57    In a normalized number, ob_digit[abs(ob_size)-1] (the most significant
  58    digit) is never zero.  Also, in all cases, for all valid i,
  59         0 <= ob_digit[i] <= MASK.
  60    The allocation fuction takes care of allocating extra memory
  61    so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available. */
  62
  63 struct _longobject {
  64         PyObject_HEAD
  65         int ob_size;
  66         digit ob_digit[1];
  67 };
  68
  69 PyLongObject *_PyLong_New Py_PROTO((int));
  70
  71 #ifdef __cplusplus
  72 }
  73 #endif
  74 #endif /* !Py_LONGINTREPR_H */