Re: [PATCH v2 1/2] protocol: add protocol version formatting function

From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: Aug 4, 2021, 23:32 UTC
Message-ID: <87czqsn5k9.fsf@evledraar.gmail.com>
In-Reply-To: <63f98062788a7c5d44fafecfde78077bdce2af73.1628115065.git.steadmon@google.com>

On Wed, Aug 04 2021, Josh Steadmon wrote:

Show 21 quoted lines

> Add a function to get human-readable names for the various wire protocol
> versions.
>
> Signed-off-by: Josh Steadmon <steadmon@google.com>
> ---
>  protocol.c | 14 ++++++++++++++
>  protocol.h |  6 ++++++
>  2 files changed, 20 insertions(+)
>
> diff --git a/protocol.c b/protocol.c
> index 052d7edbb9..7ec7ce896e 100644
> --- a/protocol.c
> +++ b/protocol.c
> @@ -14,6 +14,20 @@ static enum protocol_version parse_protocol_version(const char *value)
>  		return protocol_unknown_version;
>  }
>  
> +const char *format_protocol_version(enum protocol_version version)
> +{
> +	switch (version) {
> +		case protocol_v0:

Don't indent "case" one more than "switch".

(Looking at CodingGuidelines we only have that advice for *.sh, but we follow it for C too).

Show 7 quoted lines

> +			return "0";
> +		case protocol_v1:
> +			return "1";
> +		case protocol_v2:
> +			return "2";
> +		default:
> +			return "UNKNOWN_VERSION";

Using the "default" case like that is an anti-pattern, i.e. you enumerted all arms except protocol_unknown_version, which is implicitly covered by your "default" case.

Just list it, and don't have a "default" case, then the compiler will complain if we ever add a new case that's not covered.

As an aside, and not strictly needed here: More generally between this and parse_protocol_version() it seems like this would benefit from just declaring the bidirectional mapping beween the enum fields and string values, and then have this and that function use that. See e.g. object_type_strings and associated functions in object.c for another enum that has such a bidirectional lookup.