From: Daniel Berger <djberge@...>
Date: 2003-07-16T01:38:24+09:00
Subject: Re: Determining if a String is marshalled



Brian Candler wrote:
> On Wed, Jul 16, 2003 at 12:45:46AM +0900, Daniel Berger wrote:
> 
>>I was just wondering if there's a way to determine if a string has been 
>>marshalled without visual inspection.  Something along the lines of 
>>"string.marshalled?"  or "string.kind_of?(MarshaledString)".  Is there a 
>>regex I could use?
> 
> 
> Check for the first two bytes, which are the major/minor version number.
> Rather than hard-code it, you could do
> 
>    marshall_sig = Marshal.dump("")[0..1]
>    marshall_check = /\A#{marshall_sig}/
> 
> irb(main):004:0> "abc" =~ marshall_check
> => nil
> irb(main):005:0> Marshal.dump(123) =~ marshall_check
> => 0
> 
> Of course, the string might actually start with those bytes, but they are
> low ("\004\006" on my machine) so unlikely to occur in a normal string.
> 
> Regards,
> 
> Brian.

Thanks Brian and Matz for the info.  My only concern might be that a 
pack'd string would inadvertantly pass this test.  I guess that's what 
begin/rescue is for, though. :)

Regards,

Dan