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extern "C" { | |
/* This is published for the benefit of "friends" marshal.c and _decimal.c. */ | |
/* Parameters of the integer representation. There are two different | |
sets of parameters: one set for 30-bit digits, stored in an unsigned 32-bit | |
integer type, and one set for 15-bit digits with each digit stored in an | |
unsigned short. The value of PYLONG_BITS_IN_DIGIT, defined either at | |
configure time or in pyport.h, is used to decide which digit size to use. | |
Type 'digit' should be able to hold 2*PyLong_BASE-1, and type 'twodigits' | |
should be an unsigned integer type able to hold all integers up to | |
PyLong_BASE*PyLong_BASE-1. x_sub assumes that 'digit' is an unsigned type, | |
and that overflow is handled by taking the result modulo 2**N for some N > | |
PyLong_SHIFT. The majority of the code doesn't care about the precise | |
value of PyLong_SHIFT, but there are some notable exceptions: | |
- long_pow() requires that PyLong_SHIFT be divisible by 5 | |
- PyLong_{As,From}ByteArray require that PyLong_SHIFT be at least 8 | |
- long_hash() requires that PyLong_SHIFT is *strictly* less than the number | |
of bits in an unsigned long, as do the PyLong <-> long (or unsigned long) | |
conversion functions | |
- the Python int <-> size_t/Py_ssize_t conversion functions expect that | |
PyLong_SHIFT is strictly less than the number of bits in a size_t | |
- the marshal code currently expects that PyLong_SHIFT is a multiple of 15 | |
- NSMALLNEGINTS and NSMALLPOSINTS should be small enough to fit in a single | |
digit; with the current values this forces PyLong_SHIFT >= 9 | |
The values 15 and 30 should fit all of the above requirements, on any | |
platform. | |
*/ | |
typedef uint32_t digit; | |
typedef int32_t sdigit; /* signed variant of digit */ | |
typedef uint64_t twodigits; | |
typedef int64_t stwodigits; /* signed variant of twodigits */ | |
typedef unsigned short digit; | |
typedef short sdigit; /* signed variant of digit */ | |
typedef unsigned long twodigits; | |
typedef long stwodigits; /* signed variant of twodigits */ | |
/* 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 ints 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); | |
} | |