#ifndef Py_LIMITED_API
#ifndef Py_LONGINTREPR_H
#define Py_LONGINTREPR_H
#ifdef __cplusplus
extern "C" {
#endif
/* 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:
- 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.
*/
#if PYLONG_BITS_IN_DIGIT == 30
typedef uint32_t digit;
typedef int32_t sdigit; /* signed variant of digit */
typedef uint64_t twodigits;
typedef int64_t stwodigits; /* signed variant of twodigits */
#define PyLong_SHIFT 30
#define _PyLong_DECIMAL_SHIFT 9 /* max(e such that 10**e fits in a digit) */
#define _PyLong_DECIMAL_BASE ((digit)1000000000) /* 10 ** DECIMAL_SHIFT */
#elif PYLONG_BITS_IN_DIGIT == 15
typedef unsigned short digit;
typedef short sdigit; /* signed variant of digit */
typedef unsigned long twodigits;
typedef long stwodigits; /* signed variant of twodigits */
#define PyLong_SHIFT 15
#define _PyLong_DECIMAL_SHIFT 4 /* max(e such that 10**e fits in a digit) */
#define _PyLong_DECIMAL_BASE ((digit)10000) /* 10 ** DECIMAL_SHIFT */
#else
#error "PYLONG_BITS_IN_DIGIT should be 15 or 30"
#endif
#define PyLong_BASE ((digit)1 << PyLong_SHIFT)
#define PyLong_MASK ((digit)(PyLong_BASE - 1))
/* Long integer representation.
Long integers are made up of a number of 30- or 15-bit digits, depending on
the platform. The number of digits (ndigits) is stored in the high bits of
the lv_tag field (lvtag >> _PyLong_NON_SIZE_BITS).
The absolute value of a number is equal to
SUM(for i=0 through ndigits-1) ob_digit[i] * 2**(PyLong_SHIFT*i)
The sign of the value is stored in the lower 2 bits of lv_tag.
- 0: Positive
- 1: Zero
- 2: Negative
The third lowest bit of lv_tag is reserved for an immortality flag, but is
not currently used.
In a normalized number, ob_digit[ndigits-1] (the most significant
digit) is never zero. Also, in all cases, for all valid i,
0 <= ob_digit[i] <= PyLong_MASK.
The allocation function takes care of allocating extra memory
so that ob_digit[0] ... ob_digit[ndigits-1] are actually available.
We always allocate memory for at least one digit, so accessing ob_digit[0]
is always safe. However, in the case ndigits == 0, the contents of
ob_digit[0] may be undefined.
*/
typedef struct _PyLongValue {
uintptr_t lv_tag; /* Number of digits, sign and flags */
digit ob_digit[1];
} _PyLongValue;
struct _longobject {
PyObject_HEAD
_PyLongValue long_value;
};
PyAPI_FUNC(PyLongObject*) _PyLong_New(Py_ssize_t);
// Return a copy of src.
PyAPI_FUNC(PyObject*) _PyLong_Copy(PyLongObject *src);
PyAPI_FUNC(PyLongObject*) _PyLong_FromDigits(
int negative,
Py_ssize_t digit_count,
digit *digits);
/* Inline some internals for speed. These should be in pycore_long.h
* if user code didn't need them inlined. */
#define _PyLong_SIGN_MASK 3
#define _PyLong_NON_SIZE_BITS 3
static inline int
_PyLong_IsCompact(const PyLongObject* op) {
assert(PyType_HasFeature((op)->ob_base.ob_type, Py_TPFLAGS_LONG_SUBCLASS));
return op->long_value.lv_tag < (2 << _PyLong_NON_SIZE_BITS);
}
#define PyUnstable_Long_IsCompact _PyLong_IsCompact
static inline Py_ssize_t
_PyLong_CompactValue(const PyLongObject *op)
{
Py_ssize_t sign;
assert(PyType_HasFeature((op)->ob_base.ob_type, Py_TPFLAGS_LONG_SUBCLASS));
assert(PyUnstable_Long_IsCompact(op));
sign = 1 - (op->long_value.lv_tag & _PyLong_SIGN_MASK);
return sign * (Py_ssize_t)op->long_value.ob_digit[0];
}
#define PyUnstable_Long_CompactValue _PyLong_CompactValue
#ifdef __cplusplus
}
#endif
#endif /* !Py_LONGINTREPR_H */
#endif /* Py_LIMITED_API */
