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 typedef uint32_t digit; 46 typedef int32_t sdigit; /* signed variant of digit */ 47 typedef uint64_t twodigits; 48 typedef int64_t stwodigits; /* signed variant of twodigits */ 49 #define PyLong_SHIFT 30 50 #define _PyLong_DECIMAL_SHIFT 9 /* max(e such that 10**e fits in a digit) */ 51 #define _PyLong_DECIMAL_BASE ((digit)1000000000) /* 10 ** DECIMAL_SHIFT */ 52 #elif PYLONG_BITS_IN_DIGIT == 15 53 typedef unsigned short digit; 54 typedef short sdigit; /* signed variant of digit */ 55 typedef unsigned long twodigits; 56 typedef long stwodigits; /* signed variant of twodigits */ 57 #define PyLong_SHIFT 15 58 #define _PyLong_DECIMAL_SHIFT 4 /* max(e such that 10**e fits in a digit) */ 59 #define _PyLong_DECIMAL_BASE ((digit)10000) /* 10 ** DECIMAL_SHIFT */ 60 #else 61 #error "PYLONG_BITS_IN_DIGIT should be 15 or 30" 62 #endif 63 #define PyLong_BASE ((digit)1 << PyLong_SHIFT) 64 #define PyLong_MASK ((digit)(PyLong_BASE - 1)) 65 66 #if PyLong_SHIFT % 5 != 0 67 #error "longobject.c requires that PyLong_SHIFT be divisible by 5" 68 #endif 69 70 /* Long integer representation. 71 The absolute value of a number is equal to 72 SUM(for i=0 through abs(ob_size)-1) ob_digit[i] * 2**(SHIFT*i) 73 Negative numbers are represented with ob_size < 0; 74 zero is represented by ob_size == 0. 75 In a normalized number, ob_digit[abs(ob_size)-1] (the most significant 76 digit) is never zero. Also, in all cases, for all valid i, 77 0 <= ob_digit[i] <= MASK. 78 The allocation function takes care of allocating extra memory 79 so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available. 80 81 CAUTION: Generic code manipulating subtypes of PyVarObject has to 82 aware that ints abuse ob_size's sign bit. 83 */ 84 85 struct _longobject { 86 PyObject_VAR_HEAD 87 digit ob_digit[1]; 88 }; 89 90 PyAPI_FUNC(PyLongObject *) _PyLong_New(Py_ssize_t); 91 92 /* Return a copy of src. */ 93 PyAPI_FUNC(PyObject *) _PyLong_Copy(PyLongObject *src); 94 95 #ifdef __cplusplus 96 } 97 #endif 98 #endif /* !Py_LONGINTREPR_H */ 99 #endif /* Py_LIMITED_API */ 100
