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
66 Long integers are made up of a number of 30- or 15-bit digits, depending on
67 the platform. The number of digits (ndigits) is stored in the high bits of
68 the lv_tag field (lvtag >> _PyLong_NON_SIZE_BITS).
69
70 The absolute value of a number is equal to
71 SUM(for i=0 through ndigits-1) ob_digit[i] * 2**(PyLong_SHIFT*i)
72
73 The sign of the value is stored in the lower 2 bits of lv_tag.
74
75 - 0: Positive
76 - 1: Zero
77 - 2: Negative
78
79 The third lowest bit of lv_tag is reserved for an immortality flag, but is
80 not currently used.
81
82 In a normalized number, ob_digit[ndigits-1] (the most significant
83 digit) is never zero. Also, in all cases, for all valid i,
84 0 <= ob_digit[i] <= PyLong_MASK.
85
86 The allocation function takes care of allocating extra memory
87 so that ob_digit[0] ... ob_digit[ndigits-1] are actually available.
88 We always allocate memory for at least one digit, so accessing ob_digit[0]
89 is always safe. However, in the case ndigits == 0, the contents of
90 ob_digit[0] may be undefined.
91 */
92
93 typedef struct _PyLongValue {
94 uintptr_t lv_tag; /* Number of digits, sign and flags */
95 digit ob_digit[1];
96 } _PyLongValue;
97
98 struct _longobject {
99 PyObject_HEAD
100 _PyLongValue long_value;
101 };
102
103 PyAPI_FUNC(PyLongObject*) _PyLong_New(Py_ssize_t);
104
105 // Return a copy of src.
106 PyAPI_FUNC(PyObject*) _PyLong_Copy(PyLongObject *src);
107
108 PyAPI_FUNC(PyLongObject*) _PyLong_FromDigits(
109 int negative,
110 Py_ssize_t digit_count,
111 digit *digits);
112
113
114 /* Inline some internals for speed. These should be in pycore_long.h
115 * if user code didn't need them inlined. */
116
117 #define _PyLong_SIGN_MASK 3
118 #define _PyLong_NON_SIZE_BITS 3
119
120
121 static inline int
_PyLong_IsCompact(const PyLongObject * op)122 _PyLong_IsCompact(const PyLongObject* op) {
123 assert(PyType_HasFeature((op)->ob_base.ob_type, Py_TPFLAGS_LONG_SUBCLASS));
124 return op->long_value.lv_tag < (2 << _PyLong_NON_SIZE_BITS);
125 }
126
127 #define PyUnstable_Long_IsCompact _PyLong_IsCompact
128
129 static inline Py_ssize_t
_PyLong_CompactValue(const PyLongObject * op)130 _PyLong_CompactValue(const PyLongObject *op)
131 {
132 Py_ssize_t sign;
133 assert(PyType_HasFeature((op)->ob_base.ob_type, Py_TPFLAGS_LONG_SUBCLASS));
134 assert(PyUnstable_Long_IsCompact(op));
135 sign = 1 - (op->long_value.lv_tag & _PyLong_SIGN_MASK);
136 return sign * (Py_ssize_t)op->long_value.ob_digit[0];
137 }
138
139 #define PyUnstable_Long_CompactValue _PyLong_CompactValue
140
141
142 #ifdef __cplusplus
143 }
144 #endif
145 #endif /* !Py_LONGINTREPR_H */
146 #endif /* Py_LIMITED_API */
147