[dm-devel] [RFC PATCH 11/20] libmultipath: add vector_convert()

[Benjamin Marzinski]

On Tue, Feb 20, 2018 at 02:26:49PM +0100, Martin Wilck wrote:
> This is a handy helper for creating one vector from another,
> mapping each element of the origin vector to an element of
> the target vector with a given conversion function. It can
> also be used to "concatenate" vectors by passing in a non-NULL first
> argument.
> 

Reviewed-by: Benjamin Marzinski <bmarzins at redhat.com>

> Signed-off-by: Martin Wilck <mwilck at suse.com>
> ---
>  libmultipath/vector.h | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/libmultipath/vector.h b/libmultipath/vector.h
> index 3f6e579ae19a..6018b57525bf 100644
> --- a/libmultipath/vector.h
> +++ b/libmultipath/vector.h
> @@ -42,6 +42,35 @@ typedef struct _vector *vector;
>  #define vector_foreach_slot_backwards(v,p,i) \
>  	for (i = VECTOR_SIZE(v); i > 0 && ((p) = (v)->slot[i-1]); i--)
>  
> +#define identity(x) (x)
> +/*
> + * Given a vector vec with elements of given type,
> + * return a newly allocated vector with elements conv(e) for each element
> + * e in vec. "conv" may be a macro or a function.
> + * Use "identity" for a simple copy.
> + */
> +#define vector_convert(new, vec, type, conv)				\
> +	({								\
> +		const struct _vector *__v = (vec);			\
> +		vector __t = (new);					\
> +		type *__j;						\
> +		int __i;						\
> +									\
> +		if (__t == NULL)					\
> +			__t = vector_alloc();				\
> +		if (__t != NULL) {					\
> +			vector_foreach_slot(__v, __j, __i) {		\
> +				if (vector_alloc_slot(__t) == NULL) {	\
> +					vector_free(__t);		\
> +					__t = NULL;			\
> +					break;				\
> +				}					\
> +				vector_set_slot(__t, conv(__j));	\
> +			}						\
> +		}							\
> +		__t;							\
> +	})
> +
>  /* Prototypes */
>  extern vector vector_alloc(void);
>  extern void *vector_alloc_slot(vector v);
> -- 
> 2.16.1