python (3.12.0)
1 #ifndef Py_LIMITED_API
2 #ifndef Py_LONGINTREPR_H
3 #define Py_LONGINTREPR_H
4 #ifdef __cplusplus
5 extern "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 - PyLong_{As,From}ByteArray require that PyLong_SHIFT be at least 8
25
26 - long_hash() requires that PyLong_SHIFT is *strictly* less than the number
27 of bits in an unsigned long, as do the PyLong <-> long (or unsigned long)
28 conversion functions
29
30 - the Python int <-> size_t/Py_ssize_t conversion functions expect that
31 PyLong_SHIFT is strictly less than the number of bits in a size_t
32
33 - the marshal code currently expects that PyLong_SHIFT is a multiple of 15
34
35 - NSMALLNEGINTS and NSMALLPOSINTS should be small enough to fit in a single
36 digit; with the current values this forces PyLong_SHIFT >= 9
37
38 The values 15 and 30 should fit all of the above requirements, on any
39 platform.
40 */
41
42 #if PYLONG_BITS_IN_DIGIT == 30
43 typedef uint32_t digit;
44 typedef int32_t sdigit; /* signed variant of digit */
45 typedef uint64_t twodigits;
46 typedef int64_t stwodigits; /* signed variant of twodigits */
47 #define PyLong_SHIFT 30
48 #define _PyLong_DECIMAL_SHIFT 9 /* max(e such that 10**e fits in a digit) */
49 #define _PyLong_DECIMAL_BASE ((digit)1000000000) /* 10 ** DECIMAL_SHIFT */
50 #elif PYLONG_BITS_IN_DIGIT == 15
51 typedef unsigned short digit;
52 typedef short sdigit; /* signed variant of digit */
53 typedef unsigned long twodigits;
54 typedef long stwodigits; /* signed variant of twodigits */
55 #define PyLong_SHIFT 15
56 #define _PyLong_DECIMAL_SHIFT 4 /* max(e such that 10**e fits in a digit) */
57 #define _PyLong_DECIMAL_BASE ((digit)10000) /* 10 ** DECIMAL_SHIFT */
58 #else
59 #error "PYLONG_BITS_IN_DIGIT should be 15 or 30"
60 #endif
61 #define PyLong_BASE ((digit)1 << PyLong_SHIFT)
62 #define PyLong_MASK ((digit)(PyLong_BASE - 1))
63
64 /* Long integer representation.
65 The absolute value of a number is equal to
66 SUM(for i=0 through abs(ob_size)-1) ob_digit[i] * 2**(SHIFT*i)
67 Negative numbers are represented with ob_size < 0;
68 zero is represented by ob_size == 0.
69 In a normalized number, ob_digit[abs(ob_size)-1] (the most significant
70 digit) is never zero. Also, in all cases, for all valid i,
71 0 <= ob_digit[i] <= MASK.
72 The allocation function takes care of allocating extra memory
73 so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available.
74 We always allocate memory for at least one digit, so accessing ob_digit[0]
75 is always safe. However, in the case ob_size == 0, the contents of
76 ob_digit[0] may be undefined.
77
78 CAUTION: Generic code manipulating subtypes of PyVarObject has to
79 aware that ints abuse ob_size's sign bit.
80 */
81
82 typedef struct _PyLongValue {
83 uintptr_t lv_tag; /* Number of digits, sign and flags */
84 digit ob_digit[1];
85 } _PyLongValue;
86
87 struct _longobject {
88 PyObject_HEAD
89 _PyLongValue long_value;
90 };
91
92 PyAPI_FUNC(PyLongObject *) _PyLong_New(Py_ssize_t);
93
94 /* Return a copy of src. */
95 PyAPI_FUNC(PyObject *) _PyLong_Copy(PyLongObject *src);
96
97 PyAPI_FUNC(PyLongObject *)
98 _PyLong_FromDigits(int negative, Py_ssize_t digit_count, digit *digits);
99
100
101 /* Inline some internals for speed. These should be in pycore_long.h
102 * if user code didn't need them inlined. */
103
104 #define _PyLong_SIGN_MASK 3
105 #define _PyLong_NON_SIZE_BITS 3
106
107
108 static inline int
109 _PyLong_IsCompact(const PyLongObject* op) {
110 assert(PyType_HasFeature((op)->ob_base.ob_type, Py_TPFLAGS_LONG_SUBCLASS));
111 return op->long_value.lv_tag < (2 << _PyLong_NON_SIZE_BITS);
112 }
113
114 #define PyUnstable_Long_IsCompact _PyLong_IsCompact
115
116 static inline Py_ssize_t
117 _PyLong_CompactValue(const PyLongObject *op)
118 {
119 assert(PyType_HasFeature((op)->ob_base.ob_type, Py_TPFLAGS_LONG_SUBCLASS));
120 assert(PyUnstable_Long_IsCompact(op));
121 Py_ssize_t sign = 1 - (op->long_value.lv_tag & _PyLong_SIGN_MASK);
122 return sign * (Py_ssize_t)op->long_value.ob_digit[0];
123 }
124
125 #define PyUnstable_Long_CompactValue _PyLong_CompactValue
126
127
128 #ifdef __cplusplus
129 }
130 #endif
131 #endif /* !Py_LONGINTREPR_H */
132 #endif /* Py_LIMITED_API */
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