检查文件是否为文本文件

Function isAscii(NomeFile: String): Boolean; const
Sett=2048;
var
i: Integer;
F: file;
a: Boolean;
TotSize, IncSize, ReadSize: Integer;
c: Array[0..Sett] of byte;
begin
If FileExists(NomeFile) then
begin
{$I-}
AssignFile(F, NomeFile);
Reset(F, 1);
TotSize:=FileSize(F);
IncSize:=0;
a:=true;
while (IncSize<TotSize) and (a=true) do
begin
ReadSize:=Sett;
If IncSize+ReadSize>TotSize then ReadSize:=TotSize-IncSize;
IncSize:=IncSize+ReadSize;
BlockRead(F, c, ReadSize);
For i := 0 to ReadSize-1 do // Iterate
If (c<32) and (not (c in [9, 10, 13, 26])) then a:=False;
end; // while
CloseFile(F);
{$I+}
If IOResult<>0 then Result:=False
else Result:=a;
end;
end;
　
procedure TForm1.Button1Click(Sender: TObject);
begin
if OpenDialog1.Execute then
begin
if isAscii(OpenDialog1.FileName) then
begin
ShowMessage('ASCII File');
end;
end;
end;