[Toybox] [PENDING] [fold.c] [Question]

Samuel Holland samuel at sholland.org
Mon Aug 27 15:28:38 PDT 2018


On 08/27/18 03:09, haroon maqsood wrote:
> Hi Rob,
> I started working on fold.c cleanup,
> going through the code, and testing it out, i have a couple of questions.
>  1. gnu fold engulfs \n unconditionally i.e if there is a \n after the fold has
>     happened that redundant \n does not make it to the output , that kind of
>     makes sense but the posix spec only mentions carriage returns and only if
>     the -b option is not specified. (Note* That the current pending/fold outputs
>     an extra new line.)

If a line is exactly the length that a newline would need to go after the last
character, no additional newline should be added. If there is, that's a bug. If
you're referring to a different situation, please give an example.

>  2. the current fold implementation has unfold capability , that i think should
>     not be squeezed in fold (as of yet), my plan is to have unfold as a separate
>     utility that uses infrastructure from fold if necessary, or at least make
>     unfold as a config option, please share your thoughts on this.
>  3. The tabstop thing is bit confusing for me, as the posix spec says "Tab stops
>     shall be at each column position such that n modulo 8 equals 1." ( from
>     this i understand that given the column the next column where the tab ends
>     should be a column whose modulo 8 returns 1 , kind of this pseudo code ?
>     where start is the current column. (am i understanding it right ?)
> int get_next_ts(int start)
> {
>      if (start <= 1)
>           return 9;
>      if ((start % 8) == 1)
>           return start;
>      return get_next_ts(++start);
> }

Yes, this is correct. A more idiomatic algorithm would be:

int get_next_ts(int start)
	return ((start + 8) & -8) + 1;

> Haroon


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