Subject: Re: [PATCH alt-v2] Improve function dir.c:trim_trailing_spaces()

From: Junio C Hamano <[email-masked]>
Date: Mon, 02 Jun 2014 13:23:41 -0700

Pasha Bolokhov <[email-masked]> writes:

> Discard the unnecessary 'nr_spaces' variable, remove 'strlen()' and
> improve the 'if' structure. Switch to pointers instead of integers
>
> Slightly more rare occurrences of 'text  \    ' with a backslash
> in between spaces are handled correctly. Namely, the code in
> 8ba87adad6 does not reset 'last_space' when a backslash is
> encountered and the above line stays intact as a result.
> Add a test at the end of t/t0008-ignores.sh to exhibit this behavior
>
> Signed-off-by: Pasha Bolokhov <[email-masked]>
> ---
> After correcting for the trailing backslash 'text\', a switch()
> structure gives better readability than nested 'ifs', the way I see it.
> Add a test to show that the trailing backslash 'text\' is handled
> correctly
>
>  dir.c              | 35 ++++++++++++++++++++---------------
>  t/t0008-ignores.sh | 23 +++++++++++++++++++++++
>  2 files changed, 43 insertions(+), 15 deletions(-)
>
> diff --git a/dir.c b/dir.c
> index eb6f581..06483d4 100644
> --- a/dir.c
> +++ b/dir.c
> @@ -508,21 +508,26 @@ void clear_exclude_list(struct exclude_list *el)
>  
>  static void trim_trailing_spaces(char *buf)
>  {
> -	int i, last_space = -1, nr_spaces, len = strlen(buf);
> -	for (i = 0; i < len; i++)
> -		if (buf[i] == '\\')
> -			i++;
> -		else if (buf[i] == ' ') {
> -			if (last_space == -1) {
> -				last_space = i;
> -				nr_spaces = 1;
> -			} else
> -				nr_spaces++;
> -		} else
> -			last_space = -1;
> -
> -	if (last_space != -1 && last_space + nr_spaces == len)
> -		buf[last_space] = '\0';
> +	char *p, *last_space = NULL;
> +
> +	for (p = buf; *p; p++)
> +		switch (*p) {
> +		case ' ':
> +			if (!last_space)
> +				last_space = p;
> +			break;
> +
> +		case '\\':
> +			p++;
> +			if (!*p)
> +				return;
> +

Write

			/* fallthru */

here.

> +		default:
> +			last_space = NULL;
> +		}
> +
> +	if (last_space)
> +		*last_space = '\0';
>  }

I think the loop structure is a lot simpler to follow (with or
without switch/case) with this change.  Good.

>  int add_excludes_from_file_to_list(const char *fname,
> diff --git a/t/t0008-ignores.sh b/t/t0008-ignores.sh
> index 63beb99..4cea858 100755
> --- a/t/t0008-ignores.sh
> +++ b/t/t0008-ignores.sh
> @@ -806,4 +806,27 @@ test_expect_success !MINGW 'quoting allows trailing whitespace' '
>  	test_cmp err.expect err
>  '
>  
> +test_expect_success NOT_MINGW,NOT_CYGWIN 'correct handling of backslashes' '
> +	rm -rf whitespace &&
> +	mkdir whitespace &&
> +	>"whitespace/trailing 1  "	&&
> +	>"whitespace/trailing 2 \\\\"	&&
> +	>"whitespace/trailing 3 \\\\"	&&
> +	>"whitespace/trailing 4   \\ "	&&
> +	>"whitespace/trailing 5 \\ \\ "	&&
> +	>"whitespace/trailing 6 \\a\\"	&&

Don't be cute and try to align with tabs.

> +	>whitespace/untracked &&
> +	echo "whitespace/trailing 1 \\    "			>ignore  &&
> +	echo "whitespace/trailing 2 \\\\\\\\\\\\\\\\"		>>ignore &&
> +	echo "whitespace/trailing 3 \\\\\\\\\\\\\\\\ "		>>ignore &&
> +	echo "whitespace/trailing 4   \\\\\\\\\\\\    "		>>ignore &&
> +	echo "whitespace/trailing 5 \\\\\\\\ \\\\\\\\\\\\   "	>>ignore &&
> +	echo "whitespace/trailing 6 \\\\\\\\a\\\\\\\\"		>>ignore &&
> +	echo whitespace/untracked >expect &&
> +	: >err.expect &&

Other file truncation is done with ">whitespace/filename" without an
explicit ":" aka no-op command; I know this was copied from a
previous test but perhaps we want to be consistent?

> +	git ls-files -o -X ignore whitespace >actual 2>err &&
> +	test_cmp expect actual &&
> +	test_cmp err.expect err
> +'
> +
>  test_done