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 (BASE-1)*(2*BASE+1) == MASK*(2*MASK+3)).

    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    long_pow() requires that SHIFT be divisible by 5. */

    20 

    21 typedef unsigned short digit;

    22 typedef unsigned int wdigit; /* digit widened to parameter size */

    23 #define BASE_TWODIGITS_TYPE long

    24 typedef unsigned BASE_TWODIGITS_TYPE twodigits;

    25 typedef BASE_TWODIGITS_TYPE stwodigits; /* signed variant of twodigits */

    26 

    27 #define PyLong_SHIFT    15

    28 #define PyLong_BASE     ((digit)1 << PyLong_SHIFT)

    29 #define PyLong_MASK     ((int)(PyLong_BASE - 1))

    30 

    31 /* b/w compatibility with Python 2.5 */

    32 #define SHIFT	PyLong_SHIFT

    33 #define BASE	PyLong_BASE

    34 #define MASK	PyLong_MASK

    35 

    36 #if PyLong_SHIFT % 5 != 0

    37 #error "longobject.c requires that PyLong_SHIFT be divisible by 5"

    38 #endif

    39 

    40 /* Long integer representation.

    41    The absolute value of a number is equal to

    42    	SUM(for i=0 through abs(ob_size)-1) ob_digit[i] * 2**(SHIFT*i)

    43    Negative numbers are represented with ob_size < 0;

    44    zero is represented by ob_size == 0.

    45    In a normalized number, ob_digit[abs(ob_size)-1] (the most significant

    46    digit) is never zero.  Also, in all cases, for all valid i,

    47    	0 <= ob_digit[i] <= MASK.

    48    The allocation function takes care of allocating extra memory

    49    so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available.

    50 

    51    CAUTION:  Generic code manipulating subtypes of PyVarObject has to

    52    aware that longs abuse  ob_size's sign bit.

    53 */

    54 

    55 struct _longobject {

    56 	PyObject_VAR_HEAD

    57 	digit ob_digit[1];

    58 };

    59 

    60 PyAPI_FUNC(PyLongObject *) _PyLong_New(Py_ssize_t);

    61 

    62 /* Return a copy of src. */

    63 PyAPI_FUNC(PyObject *) _PyLong_Copy(PyLongObject *src);

    64 

    65 #ifdef __cplusplus

    66 }

    67 #endif

    68 #endif /* !Py_LONGINTREPR_H */