Mattias Gaertner schrieb:
On Mon, 24 Nov 2014 22:15:29 +0100
Hans-Peter Diettrich <[email protected]> wrote:
[...]
The Delphi (and FPC) encoding model allows for strings of different
static (declared) and dynamic (true content) encoding, see the special
handling of RawByteString (Wiki).
So far it's not a good idea to simply *assume* that a string variable
contains bytes of the declared encoding. In detail one should check or
force the right dynamic encoding of every string variable, before
searching for specific bytes (chars) in it.
I'm missing documentation for working safely (and efficiently) with such
irregular strings, most probably none of the FPC (and Delphi) developers
ever noticed how users are left alone with this problem :-(
Maybe I don't understand the question, but it seems to me this is
documented where static-, dynamic cp and rawbytestring are explained.
More concrete questions:
How can a user be sure that a string parameter in a subroutine has the
specified encoding?
How to check, how to fix if needed?
http://wiki.freepascal.org/FPC_Unicode_support#Ansistring
When a procedure requires a specific encoding it uses a specific String
type. If it works with CP_ACP it uses "String". If it needs UTF8 it
uses UTF8String.
Such specifications are meaningless when the string parameters can have
a different dynamic encoding :-(
Unicode Delphi works well as long as only one codepage (CP_ACP) is used,
in addition to Unicode (UTF-16) strings. As soon as multiple codepages
can be involved at the same time, the dynamic string encodings become
almost random (observed in Delphi XE). FPC now already has multiple
built-in codepage variables (DefaultSystemCodePage...), with possibly
different values, so that the observed Delphi mess is inevitable, as
long as RawByteString results (of e.g. standard stringhandling
functions) are *not* converted when assigned to a string variable of
some specific static encoding.
Unfortunately I cannot test Lazarus trunk since a long time, no answer
on my request for assistance. So I have to wait for the next installable
download, before I can give concrete examples.
DoDi
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