Question

I have a structure like below that needs to be saved and loaded from disk.

 RSecStructure= packed record    Name               : string[255];       {NEED UNICODE SUPPORT HERE}    ScreenName         : string[255];    OrigFileName       : string[255];                        Prim               : string[255];                                               ParentVersion      : integer;    sTag1              : string[255];          sTag2              : string[255];    sTag3              : string[255];    sTag4              : string[255];    DateAdd            : TDateTime;    DateModify         : TDateTime;   end; 

Until now I have used something like this to save the structure:

function var F: FILE;     Hdr: RSecStructure; begin ...  BlockWrite (F, Hdr, SizeOf(Hdr));    ... end 

The above code worked under Delphi 7. Under D2009 I got a lot of warning messages when I make assignments between short and Unicode strings. Until now I managed to write Delphi code without having ANY compiler warnings or hints and I want to stay like that. So I need an elegant was to save strings (Unicode will be great but not critical) to disk without getting warnings.

Answer 1

Alternatively, you can declare storable short unicode string record and implement implicit ‘to string’ and ‘from string’ conversions.

program TestShortUnicodeString;  {$APPTYPE CONSOLE}  uses   SysUtils;  type   TShortUnicodeString = record   private     Data: array [0..255] of char; //WARNING - NOT initialized to an empty string   public     class operator Implicit(const sus: TShortUnicodeString): string; inline;     class operator Implicit(const ws: string): TShortUnicodeString; inline;   end;  class operator TShortUnicodeString.Implicit(const sus: TShortUnicodeString): string; begin   Result := StrPas(sus.Data); end;  class operator TShortUnicodeString.Implicit(const ws: string): TShortUnicodeString; begin   // too long strings are silently truncated   StrPLCopy(Result.Data, ws, Length(Result.Data)-1); end;  type   TTestRec = record     ws1: TShortUnicodeString;     ws2: TShortUnicodeString;   end;  var   f    : file;   test1: TTestRec;   test2: TTestRec;  begin   test1.ws1 := '6*9 =';   test1.ws2 := ' 42';   AssignFile(f, 'test.dat');   Rewrite(f, 1);   BlockWrite(f, test1, SizeOf(test1));   CloseFile(f);   AssignFile(f, 'test.dat');   Reset(f, 1);   Assert(FileSize(f) = SizeOf(test2));   BlockRead(f, test2, SizeOf(test2));   CloseFile(f);   Writeln(string(test2.ws1), string(test2.ws2));   Readln; end. 

[The code above is released to public domain and carries no license obligations.]