On Mon, 25 Jun 2012, Peter Maydell wrote: > Add field32() and field64() functions which extract a particular > bit field from a word and return it. Based on an idea by Jia Liu. > > Suggested-by: Jia Liu <pro...@gmail.com> > Signed-off-by: Peter Maydell <peter.mayd...@linaro.org> > ---
[..snip..] > +static inline uint64_t field64(uint64_t value, int start, int length) > +{ > + assert(start >= 0 && start <= 63 && length > 0 && start + length <= 64); > + return (value >> start) & (~0ULL >> (64 - length)); > +} > + > +/** > + * field32 - return a specified bit field from a uint32_t value > + * @value: The value to extract the bit field from > + * @start: The lowest bit in the bit field (numbered from 0) > + * @length: The length of the bit field > + * > + * Returns the value of the bit field extracted from the input value. > + */ > +static inline uint32_t field32(uint32_t value, int start, int length) > +{ > + assert(start >= 0 && start <= 31 && length > 0 && start + length <= 32); > + return (value >> start) & ~0U >> (32 - length); > +} > + > #endif > The field32 and field64 are inconsistent w.r.t. grouping, while both are correct, one has to go through precedence list mentally in the latter case. -- mailto:av1...@comtv.ru