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 or Corporation for National Research Initiatives or
  19 CNRI not be used in advertising or publicity pertaining to
  20 distribution of the software without specific, written prior
  21 permission.
  22
  23 While CWI is the initial source for this software, a modified version
  24 is made available by the Corporation for National Research Initiatives
  25 (CNRI) at the Internet address ftp://ftp.python.org.
  26
  27 STICHTING MATHEMATISCH CENTRUM AND CNRI DISCLAIM ALL WARRANTIES WITH
  28 REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
  29 MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH
  30 CENTRUM OR CNRI BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
  31 DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  32 PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
  33 TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
  34 PERFORMANCE OF THIS SOFTWARE.
  35
  36 ******************************************************************/
  37
  38 /* This is published for the benefit of "friend" marshal.c only. */
  39
  40 /* Parameters of the long integer representation.
  41    These shouldn't have to be changed as C should guarantee that a short
  42    contains at least 16 bits, but it's made changeable any way.
  43    Note: 'digit' should be able to hold 2*MASK+1, and 'twodigits'
  44    should be able to hold the intermediate results in 'mul'
  45    (at most MASK << SHIFT).
  46    Also, x_sub assumes that 'digit' is an unsigned type, and overflow
  47    is handled by taking the result mod 2**N for some N > SHIFT.
  48    And, at some places it is assumed that MASK fits in an int, as well. */
  49
  50 typedef unsigned short digit;
  51 typedef unsigned int wdigit; /* digit widened to parameter size */
  52 typedef unsigned long twodigits;
  53 typedef long stwodigits; /* signed variant of twodigits */
  54
  55 #define SHIFT   15
  56 #define BASE    ((digit)1 << SHIFT)
  57 #define MASK    ((int)(BASE - 1))
  58
  59 /* Long integer representation.
  60    The absolute value of a number is equal to
  61         SUM(for i=0 through abs(ob_size)-1) ob_digit[i] * 2**(SHIFT*i)
  62    Negative numbers are represented with ob_size < 0;
  63    zero is represented by ob_size == 0.
  64    In a normalized number, ob_digit[abs(ob_size)-1] (the most significant
  65    digit) is never zero.  Also, in all cases, for all valid i,
  66         0 <= ob_digit[i] <= MASK.
  67    The allocation fuction takes care of allocating extra memory
  68    so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available. */
  69
  70 struct _longobject {
  71         PyObject_HEAD
  72         int ob_size;
  73         digit ob_digit[1];
  74 };
  75
  76 DL_IMPORT(PyLongObject *) _PyLong_New Py_PROTO((int));
  77
  78 #ifdef __cplusplus
  79 }
  80 #endif
  81 #endif /* !Py_LONGINTREPR_H */