← Back
Editing: longintrepr.h
#ifndef Py_LIMITED_API #ifndef Py_LONGINTREPR_H #define Py_LONGINTREPR_H #ifdef __cplusplus extern "C" { #endif /* This is published for the benefit of "friends" marshal.c and _decimal.c. */ /* Parameters of the integer representation. There are two different sets of parameters: one set for 30-bit digits, stored in an unsigned 32-bit integer type, and one set for 15-bit digits with each digit stored in an unsigned short. The value of PYLONG_BITS_IN_DIGIT, defined either at configure time or in pyport.h, is used to decide which digit size to use. Type 'digit' should be able to hold 2*PyLong_BASE-1, and type 'twodigits' should be an unsigned integer type able to hold all integers up to PyLong_BASE*PyLong_BASE-1. x_sub assumes that 'digit' is an unsigned type, and that overflow is handled by taking the result modulo 2**N for some N > PyLong_SHIFT. The majority of the code doesn't care about the precise value of PyLong_SHIFT, but there are some notable exceptions: - long_pow() requires that PyLong_SHIFT be divisible by 5 - PyLong_{As,From}ByteArray require that PyLong_SHIFT be at least 8 - long_hash() requires that PyLong_SHIFT is *strictly* less than the number of bits in an unsigned long, as do the PyLong <-> long (or unsigned long) conversion functions - the Python int <-> size_t/Py_ssize_t conversion functions expect that PyLong_SHIFT is strictly less than the number of bits in a size_t - the marshal code currently expects that PyLong_SHIFT is a multiple of 15 - NSMALLNEGINTS and NSMALLPOSINTS should be small enough to fit in a single digit; with the current values this forces PyLong_SHIFT >= 9 The values 15 and 30 should fit all of the above requirements, on any platform. */ #if PYLONG_BITS_IN_DIGIT == 30 typedef uint32_t digit; typedef int32_t sdigit; /* signed variant of digit */ typedef uint64_t twodigits; typedef int64_t stwodigits; /* signed variant of twodigits */ #define PyLong_SHIFT 30 #define _PyLong_DECIMAL_SHIFT 9 /* max(e such that 10**e fits in a digit) */ #define _PyLong_DECIMAL_BASE ((digit)1000000000) /* 10 ** DECIMAL_SHIFT */ #elif PYLONG_BITS_IN_DIGIT == 15 typedef unsigned short digit; typedef short sdigit; /* signed variant of digit */ typedef unsigned long twodigits; typedef long stwodigits; /* signed variant of twodigits */ #define PyLong_SHIFT 15 #define _PyLong_DECIMAL_SHIFT 4 /* max(e such that 10**e fits in a digit) */ #define _PyLong_DECIMAL_BASE ((digit)10000) /* 10 ** DECIMAL_SHIFT */ #else #error "PYLONG_BITS_IN_DIGIT should be 15 or 30" #endif #define PyLong_BASE ((digit)1 << PyLong_SHIFT) #define PyLong_MASK ((digit)(PyLong_BASE - 1)) #if PyLong_SHIFT % 5 != 0 #error "longobject.c requires that PyLong_SHIFT be divisible by 5" #endif /* Long integer representation. The absolute value of a number is equal to SUM(for i=0 through abs(ob_size)-1) ob_digit[i] * 2**(SHIFT*i) Negative numbers are represented with ob_size < 0; zero is represented by ob_size == 0. In a normalized number, ob_digit[abs(ob_size)-1] (the most significant digit) is never zero. Also, in all cases, for all valid i, 0 <= ob_digit[i] <= MASK. The allocation function takes care of allocating extra memory so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available. CAUTION: Generic code manipulating subtypes of PyVarObject has to aware that ints abuse ob_size's sign bit. */ struct _longobject { PyObject_VAR_HEAD digit ob_digit[1]; }; PyAPI_FUNC(PyLongObject *) _PyLong_New(Py_ssize_t); /* Return a copy of src. */ PyAPI_FUNC(PyObject *) _PyLong_Copy(PyLongObject *src); #ifdef __cplusplus } #endif #endif /* !Py_LONGINTREPR_H */ #endif /* Py_LIMITED_API */
Save File
Cancel