Re: [PATCH v2 05/10] split-index.c: dump "link" extension as json

[Jeff Hostetler <git@jeffhostetler.com>]

On 6/24/2019 9:02 AM, Nguyễn Thái Ngọc Duy wrote:
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
>   json-writer.c             | 14 ++++++++++++++
>   json-writer.h             |  3 +++
>   split-index.c             |  9 ++++++++-
>   t/t3011-ls-files-json.sh  | 14 ++++++++++++++
>   t/t3011/split-index (new) | 39 +++++++++++++++++++++++++++++++++++++++
>   5 files changed, 78 insertions(+), 1 deletion(-)
> 
> diff --git a/json-writer.c b/json-writer.c
> index 0608726512..c0bd302e4e 100644
> --- a/json-writer.c
> +++ b/json-writer.c
> @@ -1,4 +1,5 @@
>   #include "cache.h"
> +#include "ewah/ewok.h"
>   #include "json-writer.h"
>   
>   void jw_init(struct json_writer *jw)
> @@ -224,6 +225,19 @@ void jw_object_stat_data(struct json_writer *jw, const char *name,
>   	jw_end(jw);
>   }
>   
> +static void dump_ewah_one(size_t pos, void *jw)
> +{
> +	jw_array_intmax(jw, pos);
> +}
> +
> +void jw_object_ewah(struct json_writer *jw, const char *key,
> +		    struct ewah_bitmap *ewah)
> +{
> +	jw_object_inline_begin_array(jw, key);
> +	ewah_each_bit(ewah, dump_ewah_one, jw);
> +	jw_end(jw);
> +}
> +

As I said in an earlier commit in this series, I'd prefer
that we keep such data-structure-specific helper functions
in the source file that defines the data structure rather
than adding them to json-writer.[ch]

I'm curious how big these EWAHs will be in practice and
how useful an array of integers will be (especially as the
pretty format will be one integer per line).  Perhaps it
would helpful to have an extended example in one of the
tests.

Would it be better to have the caller of ewah_each_bit()
build a hex or bit string in a strbuf and then write it
as a single string?

Jeff