Delphi读写UTF8、Unicode格式文本文件

数说明：f文件名、s写入或读取的文件内容、hs文件头、b是否读写文件头。

procedure SaveUTF(f: string; s: string; b: boolean = true);
var
  ms: TMemoryStream;
  hs: string;
begin
  if s = '' then
    exit;
  ms := TMemoryStream.Create;
  if b then
  begin
    hs := #$EF#$BB#$BF;
    ms.Write(hs[1], 3);
  end;
  s := AnsiToUtf8(s);
  ms.Write(s[1], Length(s));
  ms.Position := 0;
  ms.SaveToFile(f);
  ms.Free;
end;

function LoadUTF(f: string; b: boolean = true): string;
var
  ms: TMemoryStream;
  s, hs: string;
begin
  Result := '';
  if not FileExists(f) then
    exit;
  ms := TMemoryStream.Create;
  ms.LoadFromFile(f);
  if b then
  begin
    SetLength(hs, 3);
    ms.Read(hs[1], 3);
    if hs <> #$EF#$BB#$BF then
    begin
      ms.Free;
      exit;
    end;
    SetLength(s, ms.Size - 3);
    ms.Read(s[1], ms.Size - 3);
  end
  else
  begin
    SetLength(s, ms.Size);
    ms.Read(s[1], ms.Size);
  end;
  Result := Utf8ToAnsi(s);
  ms.Free;
end;

procedure SaveUnicode(f: string; s: string; b: boolean = true);
var
  ms: TMemoryStream;
  hs: string;
  ws: WideString;
begin
  if s = '' then
    exit;
  ms := TMemoryStream.Create;
  if b then
  begin
    hs := #$FF#$FE;
    ms.Write(hs[1], 2);
  end;
  ws := WideString(s);
  ms.Write(ws[1], Length(ws) * 2);
  ms.Position := 0;
  ms.SaveToFile(f);
  ms.Free;
end;

function LoadUnicode(f: string; b: boolean = true): string;
var
  ms: TMemoryStream;
  hs: string;
  ws: WideString;
begin
  Result := '';
  if not FileExists(f) then
    exit;
  ms := TMemoryStream.Create;
  ms.LoadFromFile(f);
  if b then
  begin
    SetLength(hs, 2);
    ms.Read(hs[1], 2);
    if hs <> #$FF#$FE then
    begin
      ms.Free;
      exit;
    end;
    SetLength(ws, (ms.Size - 2) div 2);
    ms.Read(ws[1], ms.Size - 2);
  end
  else
  begin
    SetLength(ws, ms.Size div 2);
    ms.Read(ws[1], ms.Size);
  end;
  Result := AnsiString(ws);
  ms.Free;
end;