Re^3: Unpacking fixed length records

B Bu But it works for me? My "perl -v" insists it is 5.8.0. What version of Perl are you running? I changed the test program input and format to more closely mirror what you wanted.

  $str = "\000\005ABC\000\004DE\000\003F";
  $fmt = "(n XX /a)*";

returns

'0', '5', '65', '66', '67'
'0', '4', '68', '69'
'0', '3', '70'

Also tried it with "(nXX/a)*" with same results. When you run the same program does it get different results or a syntax error? You said it doesn't parse? As in it doesn't split the input correctly? Could it be a big/little-endian problem?

(shenme wants to know if the battery in his new toy has run down)

Comment on Re^3: Unpacking fixed length records

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Re: Re^4: Unpacking fixed length records by diotalevi (Canon) on Oct 07, 2002 at 14:29 UTC
Ok, so it appears to be the data that's goofy. I re-ran your code snippet and it worked just fine. When I run that on my data I get the error "/ must follow a numeric type" which according to diagnostics is "(F) You had an unpack template that contained a '#', but this did not follow some numeric unpack specification. See perlfunc/pack.". That's an unhelpful error (to me anyway). I had misinterpreted that to be a compile-time error so didn't even think that the unpack format was valid. Now I'm stuck with a blob of data that doesn't appear to unpack correctly. I tried cutting bits off from the end and oddly - it works sometimes though not consistently from different contexts. The behaviour is so bizarre that I'm just going to have to write a better test for it to tease out where either I'm going wrong or perl is buggy. When I know something further I'll post to this or a new thread later. `__SIG__ printf "You are here %08x\n", unpack "L!", unpack "P4", pack "L!", B:: +svref_2object(sub{})->OUTSIDE` [download]	[reply] [d/l]

Replies are listed 'Best First'.

Re: Re^4: Unpacking fixed length records
by diotalevi (Canon) on Oct 07, 2002 at 14:29 UTC

Ok, so it appears to be the data that's goofy. I re-ran your code snippet and it worked just fine. When I run that on my data I get the error "/ must follow a numeric type" which according to diagnostics is "(F) You had an unpack template that contained a '#', but this did not follow some numeric unpack specification. See perlfunc/pack.". That's an unhelpful error (to me anyway). I had misinterpreted that to be a compile-time error so didn't even think that the unpack format was valid.

Now I'm stuck with a blob of data that doesn't appear to unpack correctly. I tried cutting bits off from the end and oddly - it works sometimes though not consistently from different contexts. The behaviour is so bizarre that I'm just going to have to write a better test for it to tease out where either I'm going wrong or perl is buggy. When I know something further I'll post to this or a new thread later.

__SIG__
printf "You are here %08x\n", unpack "L!", unpack "P4", pack "L!", B::
+svref_2object(sub{})->OUTSIDE
[download]

[reply]
[d/l]