ref: 196da4ec6f429683a351312d1f0bcb05847e7f89
dir: /sys/src/cmd/python/Include/longintrepr.h/
#ifndef Py_LONGINTREPR_H #define Py_LONGINTREPR_H #ifdef __cplusplus extern "C" { #endif /* This is published for the benefit of "friend" marshal.c only. */ /* Parameters of the long integer representation. These shouldn't have to be changed as C should guarantee that a short contains at least 16 bits, but it's made changeable anyway. Note: 'digit' should be able to hold 2*MASK+1, and 'twodigits' should be able to hold the intermediate results in 'mul' (at most (BASE-1)*(2*BASE+1) == MASK*(2*MASK+3)). Also, x_sub assumes that 'digit' is an unsigned type, and overflow is handled by taking the result mod 2**N for some N > SHIFT. And, at some places it is assumed that MASK fits in an int, as well. long_pow() requires that SHIFT be divisible by 5. */ typedef unsigned short digit; typedef unsigned int wdigit; /* digit widened to parameter size */ #define BASE_TWODIGITS_TYPE long typedef unsigned BASE_TWODIGITS_TYPE twodigits; typedef BASE_TWODIGITS_TYPE stwodigits; /* signed variant of twodigits */ #define SHIFT 15 #define BASE ((digit)1 << SHIFT) #define MASK ((int)(BASE - 1)) #if SHIFT % 5 != 0 #error "longobject.c requires that SHIFT be divisible by 5" #endif /* Long integer representation. The absolute value of a number is equal to SUM(for i=0 through abs(ob_size)-1) ob_digit[i] * 2**(SHIFT*i) Negative numbers are represented with ob_size < 0; zero is represented by ob_size == 0. In a normalized number, ob_digit[abs(ob_size)-1] (the most significant digit) is never zero. Also, in all cases, for all valid i, 0 <= ob_digit[i] <= MASK. The allocation function takes care of allocating extra memory so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available. CAUTION: Generic code manipulating subtypes of PyVarObject has to aware that longs abuse ob_size's sign bit. */ struct _longobject { PyObject_VAR_HEAD digit ob_digit[1]; }; PyAPI_FUNC(PyLongObject *) _PyLong_New(Py_ssize_t); /* Return a copy of src. */ PyAPI_FUNC(PyObject *) _PyLong_Copy(PyLongObject *src); #ifdef __cplusplus } #endif #endif /* !Py_LONGINTREPR_H */