iPXE
isqrt.c
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1 /*
2  * Copyright (C) 2014 Michael Brown <mbrown@fensystems.co.uk>.
3  *
4  * This program is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU General Public License as
6  * published by the Free Software Foundation; either version 2 of the
7  * License, or any later version.
8  *
9  * This program is distributed in the hope that it will be useful, but
10  * WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12  * General Public License for more details.
13  *
14  * You should have received a copy of the GNU General Public License
15  * along with this program; if not, write to the Free Software
16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
17  * 02110-1301, USA.
18  *
19  * You can also choose to distribute this program under the terms of
20  * the Unmodified Binary Distribution Licence (as given in the file
21  * COPYING.UBDL), provided that you have satisfied its requirements.
22  */
23 
24 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
25 
26 /** @file
27  *
28  * Integer square root
29  *
30  */
31 
32 #include <ipxe/isqrt.h>
33 
34 /**
35  * Find integer square root
36  *
37  * @v value Value
38  * @v isqrt Integer square root of value
39  */
40 unsigned long isqrt ( unsigned long value ) {
41  unsigned long result = 0;
42  unsigned long bit = ( 1UL << ( ( 8 * sizeof ( bit ) ) - 2 ) );
43 
44  while ( bit > value )
45  bit >>= 2;
46  while ( bit ) {
47  if ( value >= ( result + bit ) ) {
48  value -= ( result + bit );
49  result = ( ( result >> 1 ) + bit );
50  } else {
51  result >>= 1;
52  }
53  bit >>= 2;
54  }
55  return result;
56 }
static unsigned int unsigned int bit
Definition: bigint.h:205
unsigned long isqrt(unsigned long value)
Find integer square root.
Definition: isqrt.c:40
int result
Definition: bigint.h:148
pseudo_bit_t value[0x00020]
Definition: arbel.h:13
FILE_LICENCE(GPL2_OR_LATER_OR_UBDL)
Integer square root.