From: Stefan Sperling <stsp@stsp.name>
Subject: Re: diff: Add api for consumers to check if diff is printable
To: Tom Jones <thj@freebsd.org>
Cc: gameoftrees@openbsd.org
Date: Thu, 29 Sep 2022 11:31:12 +0200

On Thu, Sep 29, 2022 at 10:17:52AM +0100, Tom Jones wrote:
> Programs using the libdiff api they can need to know if the diff
> contained anything that would be printed, or would be empty.
> 
> Expose the same check that the outputs do as a function call.
> 
> - Tom

I would prefer a name such as diff_result_contains_printable_chunks()
to make it more obvious that this interface implements a boolean check.

> diff --git a/include/diff_main.h b/include/diff_main.h
> index 5e816ae..7b6d039 100644
> --- a/include/diff_main.h
> +++ b/include/diff_main.h
> @@ -251,3 +251,4 @@ struct diff_result *diff_main(const struct diff_config *config,
>  			      struct diff_data *left,
>  			      struct diff_data *right);
>  void diff_result_free(struct diff_result *result);
> +int diff_printable_chunks(struct diff_result *result);
> diff --git a/lib/diff_main.c b/lib/diff_main.c
> index c531ad2..3043a9d 100644
> --- a/lib/diff_main.c
> +++ b/lib/diff_main.c
> @@ -628,3 +628,19 @@ diff_result_free(struct diff_result *result)
>  	ARRAYLIST_FREE(result->chunks);
>  	free(result);
>  }
> +
> +int
> +diff_printable_chunks(struct diff_result *result)
> +{
> +	struct diff_chunk *c;
> +	enum diff_chunk_type t;
> +
> +	for (int i = 0; i < result->chunks.len; i++) {
> +		c = &result->chunks.head[i];
> +		t = diff_chunk_type(c);
> +		if (t == CHUNK_MINUS || t == CHUNK_PLUS)
> +			return 1;
> +	}
> +
> +	return 0;
> +}