1  #ifndef Py_LIMITED_API
       2  #ifndef Py_LONGINTREPR_H
       3  #define Py_LONGINTREPR_H
       4  #ifdef __cplusplus
       5  extern "C" {
       6  #endif
       7  
       8  
       9  /* This is published for the benefit of "friends" marshal.c and _decimal.c. */
      10  
      11  /* Parameters of the integer representation.  There are two different
      12     sets of parameters: one set for 30-bit digits, stored in an unsigned 32-bit
      13     integer type, and one set for 15-bit digits with each digit stored in an
      14     unsigned short.  The value of PYLONG_BITS_IN_DIGIT, defined either at
      15     configure time or in pyport.h, is used to decide which digit size to use.
      16  
      17     Type 'digit' should be able to hold 2*PyLong_BASE-1, and type 'twodigits'
      18     should be an unsigned integer type able to hold all integers up to
      19     PyLong_BASE*PyLong_BASE-1.  x_sub assumes that 'digit' is an unsigned type,
      20     and that overflow is handled by taking the result modulo 2**N for some N >
      21     PyLong_SHIFT.  The majority of the code doesn't care about the precise
      22     value of PyLong_SHIFT, but there are some notable exceptions:
      23  
      24     - PyLong_{As,From}ByteArray require that PyLong_SHIFT be at least 8
      25  
      26     - long_hash() requires that PyLong_SHIFT is *strictly* less than the number
      27       of bits in an unsigned long, as do the PyLong <-> long (or unsigned long)
      28       conversion functions
      29  
      30     - the Python int <-> size_t/Py_ssize_t conversion functions expect that
      31       PyLong_SHIFT is strictly less than the number of bits in a size_t
      32  
      33     - the marshal code currently expects that PyLong_SHIFT is a multiple of 15
      34  
      35     - NSMALLNEGINTS and NSMALLPOSINTS should be small enough to fit in a single
      36       digit; with the current values this forces PyLong_SHIFT >= 9
      37  
      38    The values 15 and 30 should fit all of the above requirements, on any
      39    platform.
      40  */
      41  
      42  #if PYLONG_BITS_IN_DIGIT == 30
      43  typedef uint32_t digit;
      44  typedef int32_t sdigit; /* signed variant of digit */
      45  typedef uint64_t twodigits;
      46  typedef int64_t stwodigits; /* signed variant of twodigits */
      47  #define PyLong_SHIFT    30
      48  #define _PyLong_DECIMAL_SHIFT   9 /* max(e such that 10**e fits in a digit) */
      49  #define _PyLong_DECIMAL_BASE    ((digit)1000000000) /* 10 ** DECIMAL_SHIFT */
      50  #elif PYLONG_BITS_IN_DIGIT == 15
      51  typedef unsigned short digit;
      52  typedef short sdigit; /* signed variant of digit */
      53  typedef unsigned long twodigits;
      54  typedef long stwodigits; /* signed variant of twodigits */
      55  #define PyLong_SHIFT    15
      56  #define _PyLong_DECIMAL_SHIFT   4 /* max(e such that 10**e fits in a digit) */
      57  #define _PyLong_DECIMAL_BASE    ((digit)10000) /* 10 ** DECIMAL_SHIFT */
      58  #else
      59  #error "PYLONG_BITS_IN_DIGIT should be 15 or 30"
      60  #endif
      61  #define PyLong_BASE     ((digit)1 << PyLong_SHIFT)
      62  #define PyLong_MASK     ((digit)(PyLong_BASE - 1))
      63  
      64  /* Long integer representation.
      65     The absolute value of a number is equal to
      66          SUM(for i=0 through abs(ob_size)-1) ob_digit[i] * 2**(SHIFT*i)
      67     Negative numbers are represented with ob_size < 0;
      68     zero is represented by ob_size == 0.
      69     In a normalized number, ob_digit[abs(ob_size)-1] (the most significant
      70     digit) is never zero.  Also, in all cases, for all valid i,
      71          0 <= ob_digit[i] <= MASK.
      72     The allocation function takes care of allocating extra memory
      73     so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available.
      74     We always allocate memory for at least one digit, so accessing ob_digit[0]
      75     is always safe. However, in the case ob_size == 0, the contents of
      76     ob_digit[0] may be undefined.
      77  
      78     CAUTION:  Generic code manipulating subtypes of PyVarObject has to
      79     aware that ints abuse  ob_size's sign bit.
      80  */
      81  
      82  struct _longobject {
      83      PyObject_VAR_HEAD
      84      digit ob_digit[1];
      85  };
      86  
      87  PyAPI_FUNC(PyLongObject *) _PyLong_New(Py_ssize_t);
      88  
      89  /* Return a copy of src. */
      90  PyAPI_FUNC(PyObject *) _PyLong_Copy(PyLongObject *src);
      91  
      92  #ifdef __cplusplus
      93  }
      94  #endif
      95  #endif /* !Py_LONGINTREPR_H */
      96  #endif /* Py_LIMITED_API */