读写Unicode和UTF8格式文件

//----------------------------------------------
// Unit Name: FileExt.pas
// Comment: 读写UTF8和UNICODE格式文件的一组函数
// Author: xieyunc 改自网络
// Date : 2007-11-23 10:47:59
//----------------------------------------------
unit FileExt;

interface
  uses SysUtils,Windows,Types,Classes;

const
  utf8Head:  Array[0..2] of Char = (#239,#$bb,#$bf);
  unicodeHead: Array[0..1] of Char = (#255,#$fe);

function ReadUtf8File(const filename:string):UTF8String;
  procedure WriteUtf8File(const filename:string;mem:Utf8String);
  function ReadUnicodeFile(const filename:string):WideString;
  procedure WriteUnicodeFile(const filename:string;mem:Widestring);

implementation

// read utf8 file
function ReadUtf8File(const filename:string):Utf8String;
var
  memoStream:TFileStream;
  buf:array of Char;
begin
  memoStream:=TFileStream.Create(filename, fmOpenRead);
  try
    setlength(buf,memoStream.size);
    memoStream.ReadBuffer(buf[0], memoStream.size);
    //utf-8 file
    if (buf[0]=Utf8Head[0]) and (buf[1]=Utf8Head[1]) and (buf[2]=Utf8Head[2]) then
    begin
        FillChar(buf, SizeOf(buf), #0);
        memoStream.Seek(3,soFromBeginning);
        setlength(buf,memoStream.size-3);
        memoStream.ReadBuffer(buf[0], memoStream.size-3);
        result:=Utf8String(buf);
        exit;
    end else result:=UTF8Encode(WideString('文件不是UTF8格式！'));
  finally
    memoStream.Free;
  end;
end;

// read unicode file
function ReadUnicodeFile(const filename:string):WideString;
var
  memoStream:TFileStream;
  buf:array of Char;
begin
  memoStream:=TFileStream.Create(filename, fmOpenRead);
  try
    setlength(buf,memoStream.size);
    memoStream.ReadBuffer(buf[0], memoStream.size);
    //unicode file
    if (buf[0]=UnicodeHead[0]) and (buf[1]=UnicodeHead[1]) then
    begin
      FillChar(buf, SizeOf(buf), #0);
      memoStream.Seek(2,soFromBeginning);
      setlength(buf,memoStream.size-2);
      memoStream.ReadBuffer(buf[0], memoStream.size-2);
      result:=PWideChar(buf);
      exit;
    end else result:=WideString('文件不是UNICODE格式！');
  finally
    memoStream.Free;
  end;
end;

procedure WriteUnicodeFile(const filename:string;mem:Widestring);
var
  wms:TMemoryStream;
begin
  wms:=TMemoryStream.Create;
  wms.WriteBuffer(unicodeHead,length(unicodeHead));
  wms.WriteBuffer(PChar(mem)^,length(mem)*2);
  wms.SaveToFile(filename);
  wms.Free;
end;

procedure WriteUtf8File(const filename:string;mem:Utf8String);
var
  wms:TMemoryStream;
begin
  wms:=TMemoryStream.Create;
  wms.WriteBuffer(utf8Head,length(utf8Head));
  wms.WriteBuffer(pchar(mem)^,length(Ansistring(mem)));
  wms.SaveToFile(filename);
  wms.Free;
end;

end.

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谢祥选【小宇飞刀(xieyunc)】