Re: [PATCH 03/10] sha1-array: provide oid_array_remove_if

["Martin Ågren" <martin.agren@gmail.com>]

On 9 August 2018 at 00:17, Stefan Beller <sbeller@google.com> wrote:
> +int oid_array_remove_if(struct oid_array *array,
> +                       for_each_oid_fn fn,
> +                       void *data)
> +{
> +       int i, j;
> +       char *to_remove = xcalloc(array->nr, sizeof(char));

Do you really need this scratch space? Let's see..

> +       /* No oid_array_sort() here! See the api-oid-array.txt docs! */
> +
> +       for (i = 0; i < array->nr; i++) {
> +               int ret = fn(array->oid + i, data);
> +               if (ret)
> +                       to_remove[i] = 1;
> +       }
> +
> +       i = 0, j = 0;
> +       while (i < array->nr && j < array->nr) {
> +               while (i < array->nr && !to_remove[i])
> +                       i++;
> +               /* i at first marked for deletion or out */
> +               if (j < i)
> +                       j = i;
> +               while (j < array->nr && to_remove[j])
> +                       j++;
> +               /* j > i; j at first valid after first deletion range or out */
> +               if (i < array->nr && j < array->nr)
> +                       oidcpy(&array->oid[i], &array->oid[j]);
> +               else if (i >= array->nr)
> +                       assert(j >= array->nr);
> +                       /* no pruning happened, keep original array->nr */
> +               else if (j >= array->nr)
> +                       array->nr = i;
> +       }
> +
> +       free(to_remove);
> +
> +       return 0;
> +}

I can't entirely follow this index-fiddling, but then I haven't had my
morning coffee yet, so please forgive me if this is nonsense. Would it
suffice to let i point out where to place items (starting at the first
item not to keep) and j where to take them from (i.e., the items to
keep, after the initial run)?

> diff --git a/sha1-array.h b/sha1-array.h
> index 232bf950172..151c7ad7f30 100644
> --- a/sha1-array.h
> +++ b/sha1-array.h
> @@ -22,5 +22,8 @@ int oid_array_for_each(struct oid_array *array,
>  int oid_array_for_each_unique(struct oid_array *array,
>                               for_each_oid_fn fn,
>                               void *data);
> +int oid_array_remove_if(struct oid_array *array,
> +                       for_each_oid_fn fn,
> +                       void *data);

Maybe some documentation here, but this seems to be following suit. ;-)

Martin