Re: [PATCH 2/9] sha1-array: provide oid_array_filter

From: Junio C Hamano <gitster@pobox.com>
Date: Sep 12, 2018, 18:02 UTC
Message-ID: <xmqqzhwmlhlj.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <20180911234951.14129-3-sbeller@google.com>

Stefan Beller <sbeller@google.com> writes:

Show 18 quoted lines

> Helped-by: Junio C Hamano <gitster@pobox.com>
> Signed-off-by: Stefan Beller <sbeller@google.com>
> ---
>  sha1-array.c | 18 ++++++++++++++++++
>  sha1-array.h |  5 +++++
>  2 files changed, 23 insertions(+)
>
> diff --git a/sha1-array.c b/sha1-array.c
> index 265941fbf40..76323935dd7 100644
> --- a/sha1-array.c
> +++ b/sha1-array.c
> @@ -77,3 +77,21 @@ int oid_array_for_each_unique(struct oid_array *array,
>  	}
>  	return 0;
>  }
> +
> +int oid_array_filter(struct oid_array *array,
> +		     for_each_oid_fn fn,

It probably makes sense to call it "want" instead of "fn" to match object_array_filter().

Show 10 quoted lines

> +		     void *cbdata)
> +{
> +	int src, dst;
> +
> +	for (src = dst = 0; src < array->nr; src++) {
> +		if (fn(&array->oid[src], cbdata)) {
> +			if (dst < src)
> +				oidcpy(&array->oid[dst], &array->oid[src]);
> +			dst++;
> +		}

In fact, matching the implementation of object_array_fiter() may also make sense, as I do not see a strong reason why the resulting code would become better by rewriting "dst != src" over there to "dst < src" here.

Show 14 quoted lines

> +	}
> +	array->nr = dst;
> +
> +	return 0;
> +}
> diff --git a/sha1-array.h b/sha1-array.h
> index 232bf950172..a2d7c210835 100644
> --- a/sha1-array.h
> +++ b/sha1-array.h
> @@ -23,4 +23,9 @@ int oid_array_for_each_unique(struct oid_array *array,
>  			      for_each_oid_fn fn,
>  			      void *data);
>  
> +/* Call fn for each oid, and remove it if fn returns 0, retain it otherwise */

Also perhaps mimic the wording of object_array_filter()'s comment? I find it easier that the latter says "retaining only if X" instead of saying "remove if !X, retain otherwise"; it's both shorter and more to the point. It also is nicer that it notes that the order is preserved.

> +int oid_array_filter(struct oid_array *array,
> +		     for_each_oid_fn fn,
> +		     void *cbdata);
> +

Other than that, the function makes sense very much, and the callsite we see in patch 8/9 does, too.

Thanks.

>  #endif /* SHA1_ARRAY_H */