Re: [PATCH 6/9] oid-array: provide a for-loop iterator

From: Eric Sunshine <sunshine@sunshineco.com>
Date: Dec 4, 2020, 19:18 UTC
Message-ID: <CAPig+cTLs5bkY=Pwg+4tT2KHfVHFjkrNTeS_ygGEwq0cOOJ9wQ@mail.gmail.com>
In-Reply-To: <X8qFo+GJJTbaPV58@coredump.intra.peff.net>

On Fri, Dec 4, 2020 at 1:54 PM Jeff King <peff@peff.net> wrote:

Show 20 quoted lines

> [...]
> The caller does have to remember to sort the array first. We could add
> an assertion into the helper that array->sorted is set, but I didn't
> want to complicate what is otherwise a pretty fast code path.
> [...]
> Signed-off-by: Jeff King <peff@peff.net>
> ---
> diff --git a/oid-array.h b/oid-array.h
> @@ -111,4 +113,24 @@ void oid_array_filter(struct oid_array *array,
> +/**
> + * Find the next unique oid in the array after position "cur". You
> + * can use this to iterate over unique elements, like:
> + *
> + *   size_t i;
> + *   oid_array_sort(array);
> + *   for (i = 0; i < array->nr; i = oid_array_next_unique(array, i))
> + *     printf("%s", oid_to_hex(array->oids[i]);
> + *
> + * Non-unique iteration can just increment with "i++" to visit each element.
> + */

Minor: I see that the example code sorts the array first -- which is
necessary, as explained in the commit message -- but I wonder if it is
worth calling out explicitly in the prose:

    Find the next unique oid in the array after position `cur`.
    The array must be sorted for this to work. You can use
    this to iterate over unique elements like this:

Show 8 quoted lines

> +static inline size_t oid_array_next_unique(struct oid_array *array, size_t cur)
> +{
> +       do {
> +               cur++;
> +       } while (cur < array->nr &&
> +                oideq(array->oid + cur, array->oid + cur - 1));
> +       return cur;
> +}