mirror of https://github.com/python/cpython.git
70 lines
2.9 KiB
C
70 lines
2.9 KiB
C
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/***********************************************************
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Copyright 1991 by Stichting Mathematisch Centrum, Amsterdam, The
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Netherlands.
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All Rights Reserved
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Permission to use, copy, modify, and distribute this software and its
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documentation for any purpose and without fee is hereby granted,
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provided that the above copyright notice appear in all copies and that
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both that copyright notice and this permission notice appear in
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supporting documentation, and that the names of Stichting Mathematisch
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Centrum or CWI not be used in advertising or publicity pertaining to
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distribution of the software without specific, written prior permission.
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STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO
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THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
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FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE
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FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
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OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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******************************************************************/
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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 any way.
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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 long 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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typedef struct {
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OB_HEAD
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int ob_size; /* XXX Hack! newvarobj() stores it as unsigned! */
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digit ob_digit[1];
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} longobject;
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#define ABS(x) ((x) < 0 ? -(x) : (x))
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/* Internal use only */
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longobject *alloclongobject PROTO((int));
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longobject *long_normalize PROTO((longobject *));
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longobject *mul1 PROTO((longobject *, digit));
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longobject *muladd1 PROTO((longobject *, digit, digit));
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longobject *divrem1 PROTO((longobject *, digit, digit *));
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/* Check for interrupts during operations on long ints >= this size */
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#define INTRLIMIT 20
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