[fpc-pascal] FileIO in FPC 3.0

[Jonas Maebe]

Andreas Dorn wrote on Fri, 25 Sep 2015:

> If I understand that correctly, it stores the filename in a string that
> has been tagged as valid UTF-16.

There are no tags for valid, invalid or unchecked UTF-16. A  
unicodestring is basically a sequence of widechars. Some operations,  
such as converting to a different string type,  
uppercasing/lowercasing, case-insensitive comparison etc may however  
fail in case it's not valid UTF-16.

> Do I then have to be careful about any automagic conversions?

As long as you don't assign it to another string type besides  
unicodestring and widestring (this includes passing it as a parameter  
to a routine expecting a non-unicode/widestring parameter): no.

> Is it safe to pass the Filename to procedures from the RTL without  
> risking corruption?

It depends which RTL procedures.

> For me this is more a general problem when dealing with external data.
> Should I tag raw external data as UTF-16/UTF-8 and be super-careful,
> or should I tag it as some kind of "raw" string (which one?) and handle
> any conversions manually.

There is no "raw string" tag. There are only strings and arrays of  
bytes/words. There are no RTL file APIs accepting arrays of byte/word  
parameters.

> (Now lets better not start about the encoding of Filenames on  
> non-Windows OS... :-))

Everything about that for the supported platforms is explained at  
http://wiki.freepascal.org/FPC_Unicode_support#DefaultFileSystemCodePage


Jonas