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 (c) 2000, BeOpen.com.
   9 Copyright (c) 1995-2000, Corporation for National Research Initiatives.
  10 Copyright (c) 1990-1995, Stichting Mathematisch Centrum.
  11 All rights reserved.
  12
  13 See the file "Misc/COPYRIGHT" for information on usage and
  14 redistribution of this file, and for a DISCLAIMER OF ALL WARRANTIES.
  15 ******************************************************************/
  16
  17 /* This is published for the benefit of "friend" marshal.c only. */
  18
  19 /* Parameters of the long integer representation.
  20    These shouldn't have to be changed as C should guarantee that a short
  21    contains at least 16 bits, but it's made changeable anyway.
  22    Note: 'digit' should be able to hold 2*MASK+1, and 'twodigits'
  23    should be able to hold the intermediate results in 'mul'
  24    (at most MASK << SHIFT).
  25    Also, x_sub assumes that 'digit' is an unsigned type, and overflow
  26    is handled by taking the result mod 2**N for some N > SHIFT.
  27    And, at some places it is assumed that MASK fits in an int, as well. */
  28
  29 typedef unsigned short digit;
  30 typedef unsigned int wdigit; /* digit widened to parameter size */
  31 #define BASE_TWODIGITS_TYPE long
  32 typedef unsigned BASE_TWODIGITS_TYPE twodigits;
  33 typedef BASE_TWODIGITS_TYPE stwodigits; /* signed variant of twodigits */
  34
  35 #define SHIFT   15
  36 #define BASE    ((digit)1 << SHIFT)
  37 #define MASK    ((int)(BASE - 1))
  38
  39 /* Long integer representation.
  40    The absolute value of a number is equal to
  41         SUM(for i=0 through abs(ob_size)-1) ob_digit[i] * 2**(SHIFT*i)
  42    Negative numbers are represented with ob_size < 0;
  43    zero is represented by ob_size == 0.
  44    In a normalized number, ob_digit[abs(ob_size)-1] (the most significant
  45    digit) is never zero.  Also, in all cases, for all valid i,
  46         0 <= ob_digit[i] <= MASK.
  47    The allocation function takes care of allocating extra memory
  48    so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available. */
  49
  50 struct _longobject {
  51         PyObject_HEAD
  52         int ob_size;
  53         digit ob_digit[1];
  54 };
  55
  56 DL_IMPORT(PyLongObject *) _PyLong_New(int);
  57
  58 #ifdef __cplusplus
  59 }
  60 #endif
  61 #endif /* !Py_LONGINTREPR_H */