Am 27.06.2012 12:29, schrieb Peter Maydell:
> 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>
> ---
> v1->v2: added missing brackets to field32() to bring it in to line
> with field64()
> (Still using 'int' rather than 'unsigned' for bit numbers as per
> rationale in previous discussion.)
Reviewed-by: Andreas Färber <afaer...@suse.de>
Do you have followup patches that make use of this? Might illustrate
what variables and types are being passed in.
/-F
>
> bitops.h | 28 ++++++++++++++++++++++++++++
> 1 files changed, 28 insertions(+), 0 deletions(-)
>
> diff --git a/bitops.h b/bitops.h
> index 07d1a06..ffbb387 100644
> --- a/bitops.h
> +++ b/bitops.h
> @@ -269,4 +269,32 @@ static inline unsigned long hweight_long(unsigned long w)
> return count;
> }
>
> +/**
> + * field64 - return a specified bit field from a uint64_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 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
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