Include/longintrepr.h

   1 #ifndef Py_LONGINTREPR_H
   2 #define Py_LONGINTREPR_H
   3 #ifdef __cplusplus
   4 extern "C" {
   5 #endif
   6
   7
   8 /* This is published for the benefit of "friend" marshal.c only. */
   9
  10 /* Parameters of the long integer representation.
  11    These shouldn't have to be changed as C should guarantee that a short
  12    contains at least 16 bits, but it's made changeable anyway.
  13    Note: 'digit' should be able to hold 2*MASK+1, and 'twodigits'
  14    should be able to hold the intermediate results in 'mul'
  15    (at most MASK << SHIFT).
  16    Also, x_sub assumes that 'digit' is an unsigned type, and overflow
  17    is handled by taking the result mod 2**N for some N > SHIFT.
  18    And, at some places it is assumed that MASK fits in an int, as well. */
  19
  20 typedef unsigned short digit;
  21 typedef unsigned int wdigit; /* digit widened to parameter size */
  22 #define BASE_TWODIGITS_TYPE long
  23 typedef unsigned BASE_TWODIGITS_TYPE twodigits;
  24 typedef BASE_TWODIGITS_TYPE stwodigits; /* signed variant of twodigits */
  25
  26 #define SHIFT   15
  27 #define BASE    ((digit)1 << SHIFT)
  28 #define MASK    ((int)(BASE - 1))
  29
  30 /* Long integer representation.
  31    The absolute value of a number is equal to
  32         SUM(for i=0 through abs(ob_size)-1) ob_digit[i] * 2**(SHIFT*i)
  33    Negative numbers are represented with ob_size < 0;
  34    zero is represented by ob_size == 0.
  35    In a normalized number, ob_digit[abs(ob_size)-1] (the most significant
  36    digit) is never zero.  Also, in all cases, for all valid i,
  37         0 <= ob_digit[i] <= MASK.
  38    The allocation function takes care of allocating extra memory
  39    so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available. */
  40
  41 struct _longobject {
  42         PyObject_HEAD
  43         int ob_size;
  44         digit ob_digit[1];
  45 };
  46
  47 DL_IMPORT(PyLongObject *) _PyLong_New(int);
  48
  49 #ifdef __cplusplus
  50 }
  51 #endif
  52 #endif /* !Py_LONGINTREPR_H */