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1 #ifndef Py_LIMITED_API
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2 #ifndef Py_LONGINTREPR_H
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3 #define Py_LONGINTREPR_H
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4 #ifdef __cplusplus
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5 extern "C" {
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6 #endif
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7
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8
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9 /* This is published for the benefit of "friends" marshal.c and _decimal.c. */
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10
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11 /* Parameters of the integer representation. There are two different
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12 sets of parameters: one set for 30-bit digits, stored in an unsigned 32-bit
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13 integer type, and one set for 15-bit digits with each digit stored in an
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14 unsigned short. The value of PYLONG_BITS_IN_DIGIT, defined either at
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15 configure time or in pyport.h, is used to decide which digit size to use.
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16
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17 Type 'digit' should be able to hold 2*PyLong_BASE-1, and type 'twodigits'
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18 should be an unsigned integer type able to hold all integers up to
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19 PyLong_BASE*PyLong_BASE-1. x_sub assumes that 'digit' is an unsigned type,
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20 and that overflow is handled by taking the result modulo 2**N for some N >
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21 PyLong_SHIFT. The majority of the code doesn't care about the precise
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22 value of PyLong_SHIFT, but there are some notable exceptions:
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23
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24 - long_pow() requires that PyLong_SHIFT be divisible by 5
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25
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26 - PyLong_{As,From}ByteArray require that PyLong_SHIFT be at least 8
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27
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28 - long_hash() requires that PyLong_SHIFT is *strictly* less than the number
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29 of bits in an unsigned long, as do the PyLong <-> long (or unsigned long)
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30 conversion functions
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31
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32 - the Python int <-> size_t/Py_ssize_t conversion functions expect that
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33 PyLong_SHIFT is strictly less than the number of bits in a size_t
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34
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35 - the marshal code currently expects that PyLong_SHIFT is a multiple of 15
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36
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37 - NSMALLNEGINTS and NSMALLPOSINTS should be small enough to fit in a single
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38 digit; with the current values this forces PyLong_SHIFT >= 9
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39
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40 The values 15 and 30 should fit all of the above requirements, on any
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41 platform.
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42 */
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43
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44 #if PYLONG_BITS_IN_DIGIT == 30
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45 typedef uint32_t digit;
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46 typedef int32_t sdigit; /* signed variant of digit */
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47 typedef uint64_t twodigits;
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48 typedef int64_t stwodigits; /* signed variant of twodigits */
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49 #define PyLong_SHIFT 30
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50 #define _PyLong_DECIMAL_SHIFT 9 /* max(e such that 10**e fits in a digit) */
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51 #define _PyLong_DECIMAL_BASE ((digit)1000000000) /* 10 ** DECIMAL_SHIFT */
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52 #elif PYLONG_BITS_IN_DIGIT == 15
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53 typedef unsigned short digit;
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54 typedef short sdigit; /* signed variant of digit */
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55 typedef unsigned long twodigits;
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56 typedef long stwodigits; /* signed variant of twodigits */
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57 #define PyLong_SHIFT 15
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58 #define _PyLong_DECIMAL_SHIFT 4 /* max(e such that 10**e fits in a digit) */
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59 #define _PyLong_DECIMAL_BASE ((digit)10000) /* 10 ** DECIMAL_SHIFT */
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60 #else
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61 #error "PYLONG_BITS_IN_DIGIT should be 15 or 30"
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62 #endif
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63 #define PyLong_BASE ((digit)1 << PyLong_SHIFT)
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64 #define PyLong_MASK ((digit)(PyLong_BASE - 1))
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65
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66 #if PyLong_SHIFT % 5 != 0
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67 #error "longobject.c requires that PyLong_SHIFT be divisible by 5"
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68 #endif
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69
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70 /* Long integer representation.
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71 The absolute value of a number is equal to
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72 SUM(for i=0 through abs(ob_size)-1) ob_digit[i] * 2**(SHIFT*i)
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73 Negative numbers are represented with ob_size < 0;
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74 zero is represented by ob_size == 0.
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75 In a normalized number, ob_digit[abs(ob_size)-1] (the most significant
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76 digit) is never zero. Also, in all cases, for all valid i,
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77 0 <= ob_digit[i] <= MASK.
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78 The allocation function takes care of allocating extra memory
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79 so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available.
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80
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81 CAUTION: Generic code manipulating subtypes of PyVarObject has to
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82 aware that ints abuse ob_size's sign bit.
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83 */
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84
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85 struct _longobject {
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86 PyObject_VAR_HEAD
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87 digit ob_digit[1];
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88 };
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89
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90 PyAPI_FUNC(PyLongObject *) _PyLong_New(Py_ssize_t);
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91
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92 /* Return a copy of src. */
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93 PyAPI_FUNC(PyObject *) _PyLong_Copy(PyLongObject *src);
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94
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95 #ifdef __cplusplus
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96 }
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97 #endif
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98 #endif /* !Py_LONGINTREPR_H */
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99 #endif /* Py_LIMITED_API */
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