binary in fields and strings

[Dar Scott]

On Thursday, November 13, 2003, at 11:05 AM, Alex Rice wrote:

> Is it true that Revolution fields and strings can contain any 
> character including NULL and EOF?

Strings do just fine with ASCII NUL (0) and EOT (4).  The Revolution 
EOF is encoded as 4, also.

A few features have trouble with some values.  For example, you can't 
have a NUL in an array key.

I have seen (some versions back) NULs cause trouble in fields.  They 
mess up display and the data gotten back is garbled.  The last I 
looked, IIRC, the docs recommended avoiding any control characters in 
fields other than tab and the end of line (LF in Rev).

I don't know of a way somebody might type those.  I have some vague 
memory of holding down some key and typing digits in Windows.  I have 
not tried that with Revolution.

> I am debugging a situation where somehow a EOF character within a 
> string got sent to my CLIPS external, which caused an error, 
> understandably.

I am not sure I understand.

Is this because you open a pipe to a process and that process looks for 
the EOF character instead of a close?

Or is this because it makes a mess of parsing?

> Just want to make sure I understand what's happening before I make a 
> fix.

The limits, I think, to data passed to an external include the string 
being null terminated and some sort of 64K limit.  I don't remember 
whether the latter is for the entire call or a single parameter.

If the CLIPS library has a character set limitation, it would be 
reasonable to matchText() on that in any case.  I'd put that in and 
then use that to track down the source.

Dar Scott