add newline character strip flag to flux_buffer_read_line()

[chu11]

While working on #1331, it occurred to me that dumping data from a buffer to a log was common. By default, flux_buffer_read_line() returns a buffer with the newline character at the end, which should be stripped before dumping into a log.

It would be convenient if the library had an option to automatically strip it for you. I'm imagining just a boolean flag, so a flux_buffer_read_line (flux_buffer_t *b, int *len, bool newline) prototype.

The flag would have to be propogated into APIs that call this too of course.

[grondo]

Not that this isn't a good idea, but since e7fd48c flux_log() at least splits log messages at newlines and strips any trailing newlines for you.

Just my opinion, but I'm not a fan of the extra argument to flux_buffer_read_line, which would then have to be propagated throughout the API as you mention. I'd slightly prefer a flux_buffer_trim() which would nullify all trailing whitespace in a flux_buffer_t. Would something like that be acceptable?

[chu11]

Ohh, I wasn't even aware flux_log() did that. I saw this newline stripping code in cron.

    char *p, *saveptr = NULL;                                                                                                          
    while ((p = strtok_r (s, "\n", &saveptr))) {                                                                                       
        flux_log (h, level, "cron-%ju[%s]: rank=%d: command=\"%s\": \"%s\"",                                                           
                e->id, e->name, e->rank, e->command, p);                                                                               
        s = NULL;                                                                                                                      
    }  

which I guess is unnecessary.

Not sure a flux_buffer_trim() would work, b/c what if there are multiple lines in the buffer? Perhaps some type of flag option for the whole buffer would be best.

But for the mean time, this isn't important since flux_log() takes care of these things.

[grondo]

Not sure a flux_buffer_trim() would work, b/c what if there are multiple lines in the buffer? Perhaps some type of flag option for the whole buffer would be best.

Oh yeah, sorry I wasn't thinking when I typed that. I was forgetting how the flux_buffer_read_line was being used -- and the returned buffer is const, so can't be easily modified in place by a simplistic trim function.

In the future we could add a flag to the buffer as a whole maybe, or a separate function flux_buffer_read_trimmed_line() -- I slightly prefer that to a flag on every call. However, this is just one person's opinion.

I saw this newline stripping code in cron.

Yeah, that predates the changes to flux_log() I think, and could be simplified now since flux_log also converts multiple lines to multiple log messages.