in reply to pack auto-chomps/chops?

pack:

A: A text (ASCII) string, will be space padded

Emphasis mine. If spaces are added by pack, they'll be removed by unpack. I guess it means \s when it says space. Fix: 

sub by_ip
{
    return
        map substr($_, 4),
        sort
        map inet_aton( (split /\s/, $_, 2)[0] ) . $_,
        @_
}

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Re^2: pack auto-chomps/chops?
by bv (Friar) on Oct 07, 2009 at 19:14 UTC

    Ah, that's tricky. I suppose you're right, though. Do you know if there's a web-browsable version of the Perl source code anywhere I could check into that?

    By the way, your solution works but is slower than just appending a "\n" to the end during the final map.

    print pack("A25",pack("V*",map{1919242272+$_}(34481450,-49737472,6228,0,-285028276,6979,-1380265972)))
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      your solution works but is slower than just appending a "\n" to the end during the final map

      If pack is faster — seems odd — you could use Z instead of A.

      Ah, that's tricky. I suppose you're right, though. Do you know if there's a web-browsable version of the Perl source code anywhere I could check into that?

      http://perl5.git.perl.org/perl.git Look for pp_unpack in pp*.c (probably pp.c specifically pp_pack.c).

      The relevant code: 

      1458                     for (ptr = s+len-1; ptr >= s; ptr--)
1459                         if (*ptr != 0 && !isSPACE(*ptr)) break;
1460                     ptr++;

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      and 

      #define isSPACE(c) \
        ((c) == ' ' || (c) == '\t' || (c) == '\n' || (c) =='\r' || (c)
+ == '\f')

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      aka \s

      Update: Added relevant code.

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        Thanks, that really helps clear it up. As far as speed goes, I increased my data set and the 3 solutions (pack-and-append, pack-with-Z, and substr) are very tightly tied. I'll go with the Z approach for my final code.

        print pack("A25",pack("V*",map{1919242272+$_}(34481450,-49737472,6228,0,-285028276,6979,-1380265972)))
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