in reply to Faster way to parse binary stream

If the entire string (after the first 'no of strings' byte) is made up length/string pairs, then (subject to using an unenbalmed version of Perl) let unpack take care of it. Ignore/skip the first byte and use the ()repeat pattern to deal with it. Eg: 

$count = 3;
$str1 = "First string";
$str2 = "Second string";
$str3 = "Third string";
$bytes = pack("C C A* C A* C A*", $count, length($str1),
   $str1, length($str2), $str2, length($str3), $str3);;

print for unpack 'x(c/a*)*', $bytes;;
First string
Second string
Third string

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If there is other stuff following the strings, then you'll need to unpack the first byte and then generate the pattern: 

$n = unpack 'C', $bytes;;

print for unpack 'x (c/a*)' . $n, $bytes;;
First string
Second string
Third string

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Re^2: Faster way to parse binary stream
by ikegami (Patriarch) on Jun 19, 2007 at 20:29 UTC

    You can even combine the two calls to unpack: 

    my @strings = unpack 'c/(c/a*)', $bytes;

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Re^2: Faster way to parse binary stream
by Roy Johnson (Monsignor) on Jun 19, 2007 at 20:29 UTC
    I hadn't seen the slash template item before. To quote from the docs:

    The / template character allows packing and unpacking of strings where the packed structure contains a byte count followed by the string itself. You write length-item/string-item.

    Good solution, BrowserUK.

    Caution: Contents may have been coded under pressure.
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      Thanks to all who replied - the "C/(C/A*)*" looks like the way to go :)
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