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 | - 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 |
49 | typedef PY_UINT32_T digit; |
50 | typedef PY_INT32_T sdigit; /* signed variant of digit */ |
51 | typedef PY_UINT64_T twodigits; |
52 | typedef 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 |
57 | typedef unsigned short digit; |
58 | typedef short sdigit; /* signed variant of digit */ |
59 | typedef unsigned long twodigits; |
60 | typedef 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 | |
89 | struct _longobject { |
90 | PyObject_VAR_HEAD |
91 | digit ob_digit[1]; |
92 | }; |
93 | |
94 | PyAPI_FUNC(PyLongObject *) _PyLong_New(Py_ssize_t); |
95 | |
96 | /* Return a copy of src. */ |
97 | PyAPI_FUNC(PyObject *) _PyLong_Copy(PyLongObject *src); |
98 | |
99 | #ifdef __cplusplus |
100 | } |
101 | #endif |
102 | #endif /* !Py_LONGINTREPR_H */ |
103 | #endif /* Py_LIMITED_API */ |
104 | |