Re: [PATCH v2 2/2] [GSOC] ref-filter: introduce enum atom_type

From: Junio C Hamano <gitster@pobox.com>
To: "ZheNing Hu via GitGitGadget" <gitgitgadget@gmail.com>
Cc: git@vger.kernel.org, Jeff King <peff@peff.net>,
	Hariom Verma <hariom18599@gmail.com>,
	Christian Couder <christian.couder@gmail.com>,
	ZheNing Hu <adlternative@gmail.com>
Subject: Re: [PATCH v2 2/2] [GSOC] ref-filter: introduce enum atom_type
Date: Tue, 11 May 2021 11:14:42 +0900	[thread overview]
Message-ID: <xmqqh7jaow31.fsf@gitster.g> (raw)
In-Reply-To: <a1f70b39b7efbadff9e2202968dd1ca65ea3c1b4.1620659000.git.gitgitgadget@gmail.com> (ZheNing Hu via GitGitGadget's message of "Mon, 10 May 2021 15:03:19 +0000")

"ZheNing Hu via GitGitGadget" <gitgitgadget@gmail.com> writes:

> the enum value of `ATOM_UNKNOWN` is equals to zero, which

s/the/The/;

> could ensure that we can easily distinguish such a struct
> where the atom_type is known from such a struct where it
> is unknown yet.
>
> the enum value of `ATOM_INVALID` is equals to the size of

Ditto.

> +/*
> + * The enum atom_type is used as the coordinates of valid_atom entry.
> + * In the atom parsing stage, it will be passed to used_atom.atom_type
> + * as the identifier of the atom type. We can judge the type of used_atom
> + * entry by `if (used_atom[i].atom_type == ATOM_*)`.
> + *
> + * ATOM_UNKNOWN equals to 0, used as an enumeration value of uninitialized
> + * atom_type.

Shouldn't it be (-1)?

And I'd assume I am right in the following.

> + * ATOM_INVALID equals to the size of valid_atom array, which could help us
> + * iterate over valid_atom array like this:
> + *
> + * 	for (i = ATOM_UNKNOWN + 1; i < ATOM_INVALID; i++) {

I find it far more intuitive to say

	for (i = 0; i < ATOM_INVALID; i++)

than having to say UNKNOWN+1.

In any case, the values should be indented, and a comment should
ensure that the final one stays at the end, perhaps like this.

	enum atom_type {
		ATOM_INVALID = -2,
		ATOM_UNKNOWN = -1,
		ATOM_REFNAME,
		...
		ATOM_ELSE,
		ATOM_MAX /* MUST BE AT THE END */
	}

(note that the trailing comma is deliberately omitted).

It would allow people to say

	for (i = 0; i < ATOM_MAX; i++)

instead, which would be even nicer.