googlers / maze / linux / 7ceeff443be92913f7edd1134d677fa2a1824cd0 / . / include / asm-generic / bitops / count_zeros.h

/* Count leading and trailing zeros functions | |

* | |

* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. | |

* Written by David Howells (dhowells@redhat.com) | |

* | |

* This program is free software; you can redistribute it and/or | |

* modify it under the terms of the GNU General Public Licence | |

* as published by the Free Software Foundation; either version | |

* 2 of the Licence, or (at your option) any later version. | |

*/ | |

#ifndef _ASM_GENERIC_BITOPS_COUNT_ZEROS_H_ | |

#define _ASM_GENERIC_BITOPS_COUNT_ZEROS_H_ | |

#include <asm/bitops.h> | |

/** | |

* count_leading_zeros - Count the number of zeros from the MSB back | |

* @x: The value | |

* | |

* Count the number of leading zeros from the MSB going towards the LSB in @x. | |

* | |

* If the MSB of @x is set, the result is 0. | |

* If only the LSB of @x is set, then the result is BITS_PER_LONG-1. | |

* If @x is 0 then the result is COUNT_LEADING_ZEROS_0. | |

*/ | |

static inline int count_leading_zeros(unsigned long x) | |

{ | |

if (sizeof(x) == 4) | |

return BITS_PER_LONG - fls(x); | |

else | |

return BITS_PER_LONG - fls64(x); | |

} | |

#define COUNT_LEADING_ZEROS_0 BITS_PER_LONG | |

/** | |

* count_trailing_zeros - Count the number of zeros from the LSB forwards | |

* @x: The value | |

* | |

* Count the number of trailing zeros from the LSB going towards the MSB in @x. | |

* | |

* If the LSB of @x is set, the result is 0. | |

* If only the MSB of @x is set, then the result is BITS_PER_LONG-1. | |

* If @x is 0 then the result is COUNT_TRAILING_ZEROS_0. | |

*/ | |

static inline int count_trailing_zeros(unsigned long x) | |

{ | |

#define COUNT_TRAILING_ZEROS_0 (-1) | |

if (sizeof(x) == 4) | |

return ffs(x); | |

else | |

return (x != 0) ? __ffs(x) : COUNT_TRAILING_ZEROS_0; | |

} | |

#endif /* _ASM_GENERIC_BITOPS_COUNT_ZEROS_H_ */ |