1 #ifndef Py_LONGINTREPR_H 2 #define Py_LONGINTREPR_H 3 #ifdef __cplusplus 4 extern "C" { 5 #endif 6 7 8 /* This is published for the benefit of "friend" marshal.c only. */ 9 10 /* Parameters of the long integer representation. There are two different 11 sets of parameters: one set for 30-bit digits, stored in an unsigned 32-bit 12 integer type, and one set for 15-bit digits with each digit stored in an 13 unsigned short. The value of PYLONG_BITS_IN_DIGIT, defined either at 14 configure time or in pyport.h, is used to decide which digit size to use. 15 16 Type 'digit' should be able to hold 2*PyLong_BASE-1, and type 'twodigits' 17 should be an unsigned integer type able to hold all integers up to 18 PyLong_BASE*PyLong_BASE-1. x_sub assumes that 'digit' is an unsigned type, 19 and that overflow is handled by taking the result modulo 2**N for some N > 20 PyLong_SHIFT. The majority of the code doesn't care about the precise 21 value of PyLong_SHIFT, but there are some notable exceptions: 22 23 - long_pow() requires that PyLong_SHIFT be divisible by 5 24 25 - PyLong_{As,From}ByteArray require that PyLong_SHIFT be at least 8 26 27 - long_hash() requires that PyLong_SHIFT is *strictly* less than the number 28 of bits in an unsigned long, as do the PyLong <-> long (or unsigned long) 29 conversion functions 30 31 - the long <-> size_t/Py_ssize_t conversion functions expect that 32 PyLong_SHIFT is strictly less than the number of bits in a size_t 33 34 - the marshal code currently expects that PyLong_SHIFT is a multiple of 15 35 36 The values 15 and 30 should fit all of the above requirements, on any 37 platform. 38 */ 39 40 #if PYLONG_BITS_IN_DIGIT == 30 41 #if !(defined HAVE_UINT64_T && defined HAVE_UINT32_T && \ 42 defined HAVE_INT64_T && defined HAVE_INT32_T) 43 #error "30-bit long digits requested, but the necessary types are not available on this platform" 44 #endif 45 typedef PY_UINT32_T digit; 46 typedef PY_INT32_T sdigit; /* signed variant of digit */ 47 typedef PY_UINT64_T twodigits; 48 typedef PY_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 /* b/w compatibility with Python 2.5 */ 67 #define SHIFT PyLong_SHIFT 68 #define BASE PyLong_BASE 69 #define MASK PyLong_MASK 70 71 #if PyLong_SHIFT % 5 != 0 72 #error "longobject.c requires that PyLong_SHIFT be divisible by 5" 73 #endif 74 75 /* Long integer representation. 76 The absolute value of a number is equal to 77 SUM(for i=0 through abs(ob_size)-1) ob_digit[i] * 2**(SHIFT*i) 78 Negative numbers are represented with ob_size < 0; 79 zero is represented by ob_size == 0. 80 In a normalized number, ob_digit[abs(ob_size)-1] (the most significant 81 digit) is never zero. Also, in all cases, for all valid i, 82 0 <= ob_digit[i] <= MASK. 83 The allocation function takes care of allocating extra memory 84 so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available. 85 86 CAUTION: Generic code manipulating subtypes of PyVarObject has to 87 aware that longs abuse ob_size's sign bit. 88 */ 89 90 struct _longobject { 91 PyObject_VAR_HEAD 92 digit ob_digit[1]; 93 }; 94 95 PyAPI_FUNC(PyLongObject *) _PyLong_New(Py_ssize_t); 96 97 /* Return a copy of src. */ 98 PyAPI_FUNC(PyObject *) _PyLong_Copy(PyLongObject *src); 99 100 #ifdef __cplusplus 101 } 102 #endif 103 #endif /* !Py_LONGINTREPR_H */ 104
