Keyboard firmwares for Atmel AVR and Cortex-M
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util.c 1018B

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  1. /*
  2. Copyright 2011 Jun Wako <[email protected]>
  3. This program is free software: you can redistribute it and/or modify
  4. it under the terms of the GNU General Public License as published by
  5. the Free Software Foundation, either version 2 of the License, or
  6. (at your option) any later version.
  7. This program is distributed in the hope that it will be useful,
  8. but WITHOUT ANY WARRANTY; without even the implied warranty of
  9. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  10. GNU General Public License for more details.
  11. You should have received a copy of the GNU General Public License
  12. along with this program. If not, see <http://www.gnu.org/licenses/>.
  13. */
  14. #include "util.h"
  15. // bit population
  16. int bitpop(uint8_t bits)
  17. {
  18. int c;
  19. for (c = 0; bits; c++)
  20. bits &= bits -1;
  21. return c;
  22. }
  23. // most significant on-bit
  24. int biton(uint8_t bits)
  25. {
  26. int n = 0;
  27. if (bits >> 4) { bits >>= 4; n += 4;}
  28. if (bits >> 2) { bits >>= 2; n += 2;}
  29. if (bits >> 1) { bits >>= 1; n += 1;}
  30. return n;
  31. }