Re: How much was unpack()ed?

To "easily find out the place where unpack() finished" you could simply consume the string as you go:

(my($t),$foo) = unpack('Ca*', $foo);
if ( $t == 3 ) {
  ($v,$foo) = unpack('Z*a*', $foo); 
}
[download]

Unforunately Z* doesn't finish at the zero byte - it actually consumes the remainder of the input and discards everything beyond the zero.

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Re: Re: How much was unpack()ed? by BrowserUk (Patriarch) on May 21, 2004 at 17:33 UTC
If the fields are prefixed with length bytes, then you can prevent 'a' (or 'A' or 'Z') from consuming the rest of the string by telling format that the length byte is there. `$x = pack 'c/aN', '12345123451234512345', 99999; print for unpack 'c/a* N', $x; 12345123451234512345 99999` [download] The downside is that the length byte is then consumed. To workaround that, you have to unpack the length byte twice. `print for unpack 'cXc/a* N', $x; 20 12345123451234512345 99999` [download] However, I don't see how this helps the OP as his data has a 'type' byte but no 'length' byte. Examine what is said, not who speaks. "Efficiency is intelligent laziness." -David Dunham "Think for yourself!" - Abigail	[reply] [d/l] [select]
Re: Re: How much was unpack()ed? by ambrus (Abbot) on May 22, 2004 at 12:12 UTC
What? It seems to me that Z* does stop at the zero byte, it's only Z with a finite number that does not stop. Look. `$ perl -we '($a,$b)= unpack "Za", "nine\0eight"; warn ">>$a<< >>$b<< +";' >>nine<< >>eight<< at -e line 1. $ perl -we '($a,$b)= unpack "Z8a", "nine\0eight"; warn ">>$a<< >>$b<< +";' >>nine<< >>ht<< at -e line 1.` [download] This was with perl, v5.8.1 built for i686-linux. Update:* just checked, with perl 5.6.1, I get the wrong behaviour, that is, Z* consumes all the string.	[reply] [d/l]