Re: [PATCH v6 07/13] minmax: Introduce {min,max}_array()

[Christophe Leroy]

Le 23/06/2023 à 10:58, Herve Codina a écrit :
> Introduce min_array() (resp max_array()) in order to get the
> minimal (resp maximum) of values present in an array.
> 
> Signed-off-by: Herve Codina <herve.codina@xxxxxxxxxxx>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>

Reviewed-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>

> ---
>   include/linux/minmax.h | 64 ++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 64 insertions(+)
> 
> diff --git a/include/linux/minmax.h b/include/linux/minmax.h
> index 396df1121bff..798c6963909f 100644
> --- a/include/linux/minmax.h
> +++ b/include/linux/minmax.h
> @@ -133,6 +133,70 @@
>    */
>   #define max_t(type, x, y)	__careful_cmp((type)(x), (type)(y), >)
>   
> +/*
> + * Remove a const qualifier from integer types
> + * _Generic(foo, type-name: association, ..., default: association) performs a
> + * comparison against the foo type (not the qualified type).
> + * Do not use the const keyword in the type-name as it will not match the
> + * unqualified type of foo.
> + */
> +#define __unconst_integer_type_cases(type)	\
> +	unsigned type:  (unsigned type)0,	\
> +	signed type:    (signed type)0
> +
> +#define __unconst_integer_typeof(x) typeof(			\
> +	_Generic((x),						\
> +		char: (char)0,					\
> +		__unconst_integer_type_cases(char),		\
> +		__unconst_integer_type_cases(short),		\
> +		__unconst_integer_type_cases(int),		\
> +		__unconst_integer_type_cases(long),		\
> +		__unconst_integer_type_cases(long long),	\
> +		default: (x)))
> +
> +/*
> + * Do not check the array parameter using __must_be_array().
> + * In the following legit use-case where the "array" passed is a simple pointer,
> + * __must_be_array() will return a failure.
> + * --- 8< ---
> + * int *buff
> + * ...
> + * min = min_array(buff, nb_items);
> + * --- 8< ---
> + *
> + * The first typeof(&(array)[0]) is needed in order to support arrays of both
> + * 'int *buff' and 'int buff[N]' types.
> + *
> + * The array can be an array of const items.
> + * typeof() keeps the const qualifier. Use __unconst_integer_typeof() in order
> + * to discard the const qualifier for the __element variable.
> + */
> +#define __minmax_array(op, array, len) ({				\
> +	typeof(&(array)[0]) __array = (array);				\
> +	typeof(len) __len = (len);					\
> +	__unconst_integer_typeof(__array[0]) __element = __array[--__len]; \
> +	while (__len--)							\
> +		__element = op(__element, __array[__len]);		\
> +	__element; })
> +
> +/**
> + * min_array - return minimum of values present in an array
> + * @array: array
> + * @len: array length
> + *
> + * Note that @len must not be zero (empty array).
> + */
> +#define min_array(array, len) __minmax_array(min, array, len)
> +
> +/**
> + * max_array - return maximum of values present in an array
> + * @array: array
> + * @len: array length
> + *
> + * Note that @len must not be zero (empty array).
> + */
> +#define max_array(array, len) __minmax_array(max, array, len)
> +
>   /**
>    * clamp_t - return a value clamped to a given range using a given type
>    * @type: the type of variable to use