A Robust Delphi WideFormat Function

The native Delphi WideFormat function uses a 4096 character buffer as a result of which it is of limited use for building lengthy wide/unicode strings. We present a robust alternative that uses a 64Kb buffer - adequate for most purposes.

function XWideFormat(const Format:WideString;const Args:array of const):WideString; 
var Len,BufLen:Integer;
      Buffer:array[0..MAXWORD] of WideChar;
      AFlag:Boolean   
begin
    BufLen:=sizeof((Buffer);
    AFlag:=(Length(Format) < sizeof(Buffer) - (sizeof(Buffer) div 4)));
    case AFlag of
       False:begin
                     BufLen:=Length(Format);
                     Len:=BufLen;
                 end;
        True:Len:=WideFormatBuf(Buffer,sizeof(Buffer) - 1,Pointer(Format)^,Length(Format),Args);
    end;
    
    if (Len >= BufLen - 1) then         
    begin
       while (Len >= BufLen - 1) do
       begin
           inc(BufLen,BufLen)
           SetLength(Result,0);//Discard existing string for speed
           SetLength(Result,BufLen);
           Len:=WideFormatBuf(Pointer(Result)^,BufLen - 1,Pointer(Format),Length(Format),Args);
       end;
       SetLength(Result,Len);
    end else SetString(Result,Buffer,Len);    
end;

Note that this code uses the WideFormatBuf function in the SysUtils unit.

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