57 lines
1.5 KiB
C
57 lines
1.5 KiB
C
/*
|
|
* Copyright (C) 2014 Michael Brown <mbrown@fensystems.co.uk>.
|
|
*
|
|
* This program 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 2 of the
|
|
* License, or any later version.
|
|
*
|
|
* This program 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 this program; if not, write to the Free Software
|
|
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
|
|
* 02110-1301, USA.
|
|
*
|
|
* You can also choose to distribute this program under the terms of
|
|
* the Unmodified Binary Distribution Licence (as given in the file
|
|
* COPYING.UBDL), provided that you have satisfied its requirements.
|
|
*/
|
|
|
|
FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
|
|
|
|
/** @file
|
|
*
|
|
* Integer square root
|
|
*
|
|
*/
|
|
|
|
#include <ipxe/isqrt.h>
|
|
|
|
/**
|
|
* Find integer square root
|
|
*
|
|
* @v value Value
|
|
* @v isqrt Integer square root of value
|
|
*/
|
|
unsigned long isqrt ( unsigned long value ) {
|
|
unsigned long result = 0;
|
|
unsigned long bit = ( 1UL << ( ( 8 * sizeof ( bit ) ) - 2 ) );
|
|
|
|
while ( bit > value )
|
|
bit >>= 2;
|
|
while ( bit ) {
|
|
if ( value >= ( result + bit ) ) {
|
|
value -= ( result + bit );
|
|
result = ( ( result >> 1 ) + bit );
|
|
} else {
|
|
result >>= 1;
|
|
}
|
|
bit >>= 2;
|
|
}
|
|
return result;
|
|
}
|