1#ifndef Py_LIMITED_API
2#ifndef Py_LONGINTREPR_H
3#define Py_LONGINTREPR_H
4#ifdef __cplusplus
5extern "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 - long_pow() requires that PyLong_SHIFT be divisible by 5
25
26 - PyLong_{As,From}ByteArray require that PyLong_SHIFT be at least 8
27
28 - long_hash() requires that PyLong_SHIFT is *strictly* less than the number
29 of bits in an unsigned long, as do the PyLong <-> long (or unsigned long)
30 conversion functions
31
32 - the Python int <-> size_t/Py_ssize_t conversion functions expect that
33 PyLong_SHIFT is strictly less than the number of bits in a size_t
34
35 - the marshal code currently expects that PyLong_SHIFT is a multiple of 15
36
37 - NSMALLNEGINTS and NSMALLPOSINTS should be small enough to fit in a single
38 digit; with the current values this forces PyLong_SHIFT >= 9
39
40 The values 15 and 30 should fit all of the above requirements, on any
41 platform.
42*/
43
44#if PYLONG_BITS_IN_DIGIT == 30
45typedef uint32_t digit;
46typedef int32_t sdigit; /* signed variant of digit */
47typedef uint64_t twodigits;
48typedef int64_t stwodigits; /* signed variant of twodigits */
49#define PyLong_SHIFT 30
50#define _PyLong_DECIMAL_SHIFT 9 /* max(e such that 10**e fits in a digit) */
51#define _PyLong_DECIMAL_BASE ((digit)1000000000) /* 10 ** DECIMAL_SHIFT */
52#elif PYLONG_BITS_IN_DIGIT == 15
53typedef unsigned short digit;
54typedef short sdigit; /* signed variant of digit */
55typedef unsigned long twodigits;
56typedef long stwodigits; /* signed variant of twodigits */
57#define PyLong_SHIFT 15
58#define _PyLong_DECIMAL_SHIFT 4 /* max(e such that 10**e fits in a digit) */
59#define _PyLong_DECIMAL_BASE ((digit)10000) /* 10 ** DECIMAL_SHIFT */
60#else
61#error "PYLONG_BITS_IN_DIGIT should be 15 or 30"
62#endif
63#define PyLong_BASE ((digit)1 << PyLong_SHIFT)
64#define PyLong_MASK ((digit)(PyLong_BASE - 1))
65
66#if PyLong_SHIFT % 5 != 0
67#error "longobject.c requires that PyLong_SHIFT be divisible by 5"
68#endif
69
70/* Long integer representation.
71 The absolute value of a number is equal to
72 SUM(for i=0 through abs(ob_size)-1) ob_digit[i] * 2**(SHIFT*i)
73 Negative numbers are represented with ob_size < 0;
74 zero is represented by ob_size == 0.
75 In a normalized number, ob_digit[abs(ob_size)-1] (the most significant
76 digit) is never zero. Also, in all cases, for all valid i,
77 0 <= ob_digit[i] <= MASK.
78 The allocation function takes care of allocating extra memory
79 so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available.
80
81 CAUTION: Generic code manipulating subtypes of PyVarObject has to
82 aware that ints abuse ob_size's sign bit.
83*/
84
85struct _longobject {
86 PyObject_VAR_HEAD
87 digit ob_digit[1];
88};
89
90PyAPI_FUNC(PyLongObject *) _PyLong_New(Py_ssize_t);
91
92/* Return a copy of src. */
93PyAPI_FUNC(PyObject *) _PyLong_Copy(PyLongObject *src);
94
95#ifdef __cplusplus
96}
97#endif
98#endif /* !Py_LONGINTREPR_H */
99#endif /* Py_LIMITED_API */
100

source code of include/python3.10/longintrepr.h