Subject: Re: [PATCH 08/13] t/helper: add zlib test-tool

From: Junio C Hamano <[email-masked]>
Date: Mon, 19 May 2025 08:03:11 -0700

Jeff King <[email-masked]> writes:

> So let's introduce a short test helper for just doing zlib operations.

Oooh. I remember that I did want to use something like this from
time to time.  Nice.

> +static void do_zlib(struct git_zstream *stream,
> +		    int (*zlib_func)(git_zstream *, int),
> +		    int fd_in, int fd_out)
> +{
> +	struct strbuf buf_in = STRBUF_INIT;
> +	int status = Z_OK;
> +
> +	if (strbuf_read(&buf_in, fd_in, 0) < 0)
> +		die_errno("read error");
> +
> +	stream->next_in = (unsigned char *)buf_in.buf;
> +	stream->avail_in = buf_in.len;
> +
> +	while (status == Z_OK ||
> +	       (status == Z_BUF_ERROR && !stream->avail_out)) {
> +		unsigned char buf_out[4096];
> +
> +		stream->next_out = buf_out;
> +		stream->avail_out = sizeof(buf_out);
> +
> +		status = zlib_func(stream, Z_FINISH);
> +		if (write_in_full(fd_out, buf_out,
> +				  sizeof(buf_out) - stream->avail_out) < 0)
> +			die_errno("write error");
> +	}

Even though I may have written this as do {} while() loop, I do not
mind a while () loop that depends on status being initialized to
Z_OK.

> +	if (status != Z_STREAM_END)
> +		die("zlib error %d", status);
> +
> +	strbuf_release(&buf_in);
> +}

Looking good.

> +int cmd__zlib(int argc, const char **argv)
> +{
> +	git_zstream stream;
> +
> +	if (argc != 2)
> +		usage(zlib_usage);
> +
> +	memset(&stream, 0, sizeof(stream));
> +
> +	if (!strcmp(argv[1], "inflate")) {
> +		git_inflate_init(&stream);
> +		do_zlib(&stream, git_inflate, 0, 1);
> +		git_inflate_end(&stream);
> +	} else if (!strcmp(argv[1], "deflate")) {
> +		git_deflate_init(&stream, Z_DEFAULT_COMPRESSION);
> +		do_zlib(&stream, git_deflate, 0, 1);
> +		git_deflate_end(&stream);
> +	} else {
> +		error("unknown mode: %s", argv[1]);
> +		usage(zlib_usage);
> +	}
> +
> +	return 0;
> +}