Re: [PATCH 1/3] unpack: replace xwrite() loop with write_in_full()

From: Patrick Steinhardt <ps@pks.im>
Date: Mar 4, 2024, 06:58 UTC
Message-ID: <ZeVxA1KvN18Y85J_@tanuki>
In-Reply-To: <20240302190348.3946569-2-gitster@pobox.com>

On Sat, Mar 02, 2024 at 11:03:46AM -0800, Junio C Hamano wrote:

Show 58 quoted lines

> We have two packfile stream consumers, index-pack and
> unpack-objects, that allow excess payload after the packfile stream
> data. Their code to relay excess data hasn't changed significantly
> since their original implementation that appeared in 67e5a5ec
> (git-unpack-objects: re-write to read from stdin, 2005-06-28) and
> 9bee2478 (mimic unpack-objects when --stdin is used with index-pack,
> 2006-10-25).
> 
> These code blocks contain hand-rolled loops using xwrite(), written
> before our write_in_full() helper existed. This helper now provides
> the same functionality.
> 
> Replace these loops with write_in_full() for shorter, clearer
> code. Update related variables accordingly.
> 
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> ---
>  builtin/index-pack.c     | 17 +++--------------
>  builtin/unpack-objects.c |  8 +-------
>  2 files changed, 4 insertions(+), 21 deletions(-)
> 
> diff --git a/builtin/index-pack.c b/builtin/index-pack.c
> index a3a37bd215..856428fef9 100644
> --- a/builtin/index-pack.c
> +++ b/builtin/index-pack.c
> @@ -1524,14 +1524,12 @@ static void final(const char *final_pack_name, const char *curr_pack_name,
>  	struct strbuf pack_name = STRBUF_INIT;
>  	struct strbuf index_name = STRBUF_INIT;
>  	struct strbuf rev_index_name = STRBUF_INIT;
> -	int err;
>  
>  	if (!from_stdin) {
>  		close(input_fd);
>  	} else {
>  		fsync_component_or_die(FSYNC_COMPONENT_PACK, output_fd, curr_pack_name);
> -		err = close(output_fd);
> -		if (err)
> +		if (close(output_fd))
>  			die_errno(_("error while closing pack file"));
>  	}
>  
> @@ -1566,17 +1564,8 @@ static void final(const char *final_pack_name, const char *curr_pack_name,
>  		write_or_die(1, buf.buf, buf.len);
>  		strbuf_release(&buf);
>  
> -		/*
> -		 * Let's just mimic git-unpack-objects here and write
> -		 * the last part of the input buffer to stdout.
> -		 */
> -		while (input_len) {
> -			err = xwrite(1, input_buffer + input_offset, input_len);
> -			if (err <= 0)
> -				break;
> -			input_len -= err;
> -			input_offset += err;
> -		}
> +		/* Write the last part of the buffer to stdout */
> +		write_in_full(1, input_buffer + input_offset, input_len);

With this change we stop updating `input_len` and `input_offset`, both of which are global variables. Assuming that tests pass this must be okay right now given that this is the final part of what we are writing. But I wonder whether we shouldn't update those regardless just so that these remain consistent?

Show 19 quoted lines

>  	}
>  
>  	strbuf_release(&rev_index_name);
> diff --git a/builtin/unpack-objects.c b/builtin/unpack-objects.c
> index e0a701f2b3..f1c85a00ae 100644
> --- a/builtin/unpack-objects.c
> +++ b/builtin/unpack-objects.c
> @@ -679,13 +679,7 @@ int cmd_unpack_objects(int argc, const char **argv, const char *prefix UNUSED)
>  	use(the_hash_algo->rawsz);
>  
>  	/* Write the last part of the buffer to stdout */
> -	while (len) {
> -		int ret = xwrite(1, buffer + offset, len);
> -		if (ret <= 0)
> -			break;
> -		len -= ret;
> -		offset += ret;
> -	}
> +	write_in_full(1, buffer + offset, len);

Same here.

Patrick

Show 6 quoted lines

>  	/* All done */
>  	return has_errors;
> -- 
> 2.44.0-84-gb387623c12
> 
>