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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. FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
  24. /** @file
  25. *
  26. * Integer square root
  27. *
  28. */
  29. #include <ipxe/isqrt.h>
  30. /**
  31. * Find integer square root
  32. *
  33. * @v value Value
  34. * @v isqrt Integer square root of value
  35. */
  36. unsigned long isqrt ( unsigned long value ) {
  37. unsigned long result = 0;
  38. unsigned long bit = ( 1UL << ( ( 8 * sizeof ( bit ) ) - 2 ) );
  39. while ( bit > value )
  40. bit >>= 2;
  41. while ( bit ) {
  42. if ( value >= ( result + bit ) ) {
  43. value -= ( result + bit );
  44. result = ( ( result >> 1 ) + bit );
  45. } else {
  46. result >>= 1;
  47. }
  48. bit >>= 2;
  49. }
  50. return result;
  51. }