mescc: Mes C Library: Add integer division algorithm.

* lib/mes/div.c: New file.
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Danny Milosavljevic 2019-06-14 00:57:43 +02:00 committed by Jan Nieuwenhuizen
parent 1bb64ec48f
commit cc870b4adc
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lib/mes/div.c Normal file
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/* -*-comment-start: "//";comment-end:""-*-
* GNU Mes --- Maxwell Equations of Software
* Copyright © 2016,2017,2018,2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
* Copyright © 2019 Danny Milosavljevic <dannym@scratchpost.org>
*
* This file is part of GNU Mes.
*
* GNU Mes is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or (at
* your option) any later version.
*
* GNU Mes is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU Mes. If not, see <http://www.gnu.org/licenses/>.
*/
#include <mes/lib.h>
#include <assert.h>
#include <stdint.h>
#include <limits.h>
/*#define LONG_MIN (-(~0UL>>1)-1)*/
typedef struct
{
long quot;
long rem;
} ldiv_t;
void __mesabi_div0(void)
{
eputs(" ***MES C LIB*** divide by zero numerator=");
eputs("\n");
assert(0);
}
/* Compare gcc: __udivdi3 */
unsigned long __mesabi_uldiv(unsigned long a, unsigned long b, unsigned long* remainder)
{
unsigned long tmp;
if (!remainder)
remainder = &tmp;
*remainder = 0;
if (b == 1)
return a;
else if (b == 0)
__mesabi_div0();
else
{
unsigned long x;
for (x = 0; a >= b; a -= b)
++x;
*remainder = a;
return x;
}
}
/* Note: Rounds towards zero */
ldiv_t ldiv(long a, long b)
{
ldiv_t result;
int negative_result = (a < 0) ^ (b < 0);
assert(a != LONG_MIN && b != LONG_MIN);
if (a < 0)
a = -a;
if (b < 0)
b = -b;
result.quot = __mesabi_uldiv(a, b, &result.rem);
if (negative_result)
result.quot = -result.quot;
return result;
}