mirror of https://github.com/python/cpython
62 lines
2.2 KiB
C
62 lines
2.2 KiB
C
#ifndef Py_LONGINTREPR_H
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#define Py_LONGINTREPR_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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/***********************************************************
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Copyright (c) 2000, BeOpen.com.
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Copyright (c) 1995-2000, Corporation for National Research Initiatives.
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Copyright (c) 1990-1995, Stichting Mathematisch Centrum.
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All rights reserved.
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See the file "Misc/COPYRIGHT" for information on usage and
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redistribution of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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******************************************************************/
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/* This is published for the benefit of "friend" marshal.c only. */
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/* Parameters of the long integer representation.
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These shouldn't have to be changed as C should guarantee that a short
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contains at least 16 bits, but it's made changeable anyway.
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Note: 'digit' should be able to hold 2*MASK+1, and 'twodigits'
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should be able to hold the intermediate results in 'mul'
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(at most MASK << SHIFT).
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Also, x_sub assumes that 'digit' is an unsigned type, and overflow
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is handled by taking the result mod 2**N for some N > SHIFT.
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And, at some places it is assumed that MASK fits in an int, as well. */
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typedef unsigned short digit;
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typedef unsigned int wdigit; /* digit widened to parameter size */
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#define BASE_TWODIGITS_TYPE long
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typedef unsigned BASE_TWODIGITS_TYPE twodigits;
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typedef BASE_TWODIGITS_TYPE stwodigits; /* signed variant of twodigits */
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#define SHIFT 15
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#define BASE ((digit)1 << SHIFT)
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#define MASK ((int)(BASE - 1))
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/* Long integer representation.
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The absolute value of a number is equal to
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SUM(for i=0 through abs(ob_size)-1) ob_digit[i] * 2**(SHIFT*i)
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Negative numbers are represented with ob_size < 0;
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zero is represented by ob_size == 0.
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In a normalized number, ob_digit[abs(ob_size)-1] (the most significant
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digit) is never zero. Also, in all cases, for all valid i,
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0 <= ob_digit[i] <= MASK.
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The allocation fuction takes care of allocating extra memory
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so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available. */
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struct _longobject {
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PyObject_HEAD
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int ob_size;
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digit ob_digit[1];
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};
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DL_IMPORT(PyLongObject *) _PyLong_New(int);
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#ifdef __cplusplus
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}
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#endif
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#endif /* !Py_LONGINTREPR_H */
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