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
45#if !(defined HAVE_UINT64_T && defined HAVE_UINT32_T && \
46 defined HAVE_INT64_T && defined HAVE_INT32_T)
47#error "30-bit long digits requested, but the necessary types are not available on this platform"
48#endif
49typedef PY_UINT32_T digit;
50typedef PY_INT32_T sdigit; /* signed variant of digit */
51typedef PY_UINT64_T twodigits;
52typedef PY_INT64_T stwodigits; /* signed variant of twodigits */
53#define PyLong_SHIFT 30
54#define _PyLong_DECIMAL_SHIFT 9 /* max(e such that 10**e fits in a digit) */
55#define _PyLong_DECIMAL_BASE ((digit)1000000000) /* 10 ** DECIMAL_SHIFT */
56#elif PYLONG_BITS_IN_DIGIT == 15
57typedef unsigned short digit;
58typedef short sdigit; /* signed variant of digit */
59typedef unsigned long twodigits;
60typedef long stwodigits; /* signed variant of twodigits */
61#define PyLong_SHIFT 15
62#define _PyLong_DECIMAL_SHIFT 4 /* max(e such that 10**e fits in a digit) */
63#define _PyLong_DECIMAL_BASE ((digit)10000) /* 10 ** DECIMAL_SHIFT */
64#else
65#error "PYLONG_BITS_IN_DIGIT should be 15 or 30"
66#endif
67#define PyLong_BASE ((digit)1 << PyLong_SHIFT)
68#define PyLong_MASK ((digit)(PyLong_BASE - 1))
69
70#if PyLong_SHIFT % 5 != 0
71#error "longobject.c requires that PyLong_SHIFT be divisible by 5"
72#endif
73
74/* Long integer representation.
75 The absolute value of a number is equal to
76 SUM(for i=0 through abs(ob_size)-1) ob_digit[i] * 2**(SHIFT*i)
77 Negative numbers are represented with ob_size < 0;
78 zero is represented by ob_size == 0.
79 In a normalized number, ob_digit[abs(ob_size)-1] (the most significant
80 digit) is never zero. Also, in all cases, for all valid i,
81 0 <= ob_digit[i] <= MASK.
82 The allocation function takes care of allocating extra memory
83 so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available.
84
85 CAUTION: Generic code manipulating subtypes of PyVarObject has to
86 aware that ints abuse ob_size's sign bit.
87*/
88
89struct _longobject {
90 PyObject_VAR_HEAD
91 digit ob_digit[1];
92};
93
94PyAPI_FUNC(PyLongObject *) _PyLong_New(Py_ssize_t);
95
96/* Return a copy of src. */
97PyAPI_FUNC(PyObject *) _PyLong_Copy(PyLongObject *src);
98
99#ifdef __cplusplus
100}
101#endif
102#endif /* !Py_LONGINTREPR_H */
103#endif /* Py_LIMITED_API */
104