111 lines
2.7 KiB
C
111 lines
2.7 KiB
C
/* -*-comment-start: "//";comment-end:""-*-
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* GNU Mes --- Maxwell Equations of Software
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* Copyright © 2016,2017,2018,2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
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* Copyright © 2019 Danny Milosavljevic <dannym@scratchpost.org>
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*
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* This file is part of GNU Mes.
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*
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* GNU Mes is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or (at
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* your option) any later version.
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*
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* GNU Mes is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GNU Mes. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <mes/lib.h>
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#include <assert.h>
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#include <stdint.h>
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#include <limits.h>
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/*#define LONG_MIN (-(~0UL>>1)-1)*/
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typedef struct
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{
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long quot;
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long rem;
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} ldiv_t;
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void __mesabi_div0(void)
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{
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eputs(" ***MES C LIB*** divide by zero numerator=");
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eputs("\n");
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assert(0);
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}
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/* Compare gcc: __udivdi3 */
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unsigned long __mesabi_uldiv(unsigned long a, unsigned long b, unsigned long* remainder)
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{
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unsigned long tmp;
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if (!remainder)
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remainder = &tmp;
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*remainder = 0;
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if (b == 1)
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return a;
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else if (b == 0)
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__mesabi_div0();
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else
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{
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unsigned long x;
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for (x = 0; a >= b; a -= b)
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++x;
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*remainder = a;
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return x;
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}
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}
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/* Note: Rounds towards zero.
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Maintainer: Be careful to satisfy quot * b + rem == a.
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That means that rem can be negative. */
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ldiv_t ldiv(long a, long b)
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{
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ldiv_t result;
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int negate_result = (a < 0) ^ (b < 0);
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assert(b != LONG_MIN);
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if (a != LONG_MIN)
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{
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int negative_a = (a < 0);
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if (negative_a)
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a = -a;
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if (b < 0)
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b = -b;
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result.quot = __mesabi_uldiv(a, b, &result.rem);
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if (negate_result)
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result.quot = -result.quot;
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if (negative_a)
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result.rem = -result.rem;
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return result;
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}
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else
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{
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result.rem = 0;
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if (b < 0)
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b = -b;
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if (b == 1)
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{
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result.quot = a;
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/* Since result.quot is already negative, don't negate it again. */
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negate_result = !negate_result;
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}
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else if (b == 0)
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__mesabi_div0();
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else
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{
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long x;
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for (x = 0; a <= -b; a += b)
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++x;
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result.rem = a; /* negative */
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result.quot = x;
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}
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if (negate_result)
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result.quot = -result.quot;
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return result;
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}
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}
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