unicode文本文件输出在XE2和Delphi 2009之间有所不同吗？ [英] unicode text file output differs between XE2 and Delphi 2009?

问题描述

当我尝试下面的代码时，与D2009相比，XE2中的代码似乎有所不同。

  procedure TForm1.Button1Click（发件人：TObject）; 
 var Outfile：textfile; 
 myByte：Byte; 
 
 begin 
 assignfile（Outfile，'test_chinese.txt'）; 
重写（Outfile）; 
 
为myByte在TEncoding.UTF8.GetPreamble做写（Outfile，AnsiChar（myByte））; 
 //这是UTF-8 BOM 
 
 Writeln（Outfile，utf8string（'总结'））; 
 Writeln（Outfile，'°C'）; 
 Closefile（Outfile）; 
结束
  

在Windows 8 PC上编译XE2在写字板中给出

??
C

txt十六进制代码：EF BB BF 3F 3F 0D 0A B0 43 0D 0A

在Windows XP PC上使用D2009编写，在Wordpad中提供

总结
°C

txt hex代码：EF BB BF E6 80 BB E7 BB 93 0D 0A B0 43 0D 0A

我的问题是为什么它不同，如何将汉字保存到文本文件中旧的文本文件I / O？

谢谢！

解决方案

在XE2之前， AssignFile（） 有一个可选的 CodePage 参数，设置输出文件的代码页：

 函数AssignFile（var F：File; FileName：String; [CodePage：Word]）：Integer;超载; 
  

Write（）和 Writeln（）都有重载，支持 UnicodeString 和 WideChar 输入。 p>

因此，您可以创建一个文件，其代码页设置为 CP_UTF8 ，然后写入/ ln（）会在将Unicode字符串写入文件时自动将Unicode字符串转换为UTF-8。

缺点是您不会能够使用 AnsiChar 值写入UTF-8 BOM，因为单个字节将被转换为UTF-8，因此不能正确写入。您可以通过将BOM编写为单个Unicode字符（它实际上是 - U + FEFF ）而不是单个字节来解决。

这在XE2中有效：

  procedure TForm1.Button1Click（Sender：TObject）; 
 var 
 Outfile：TextFile; 
 begin 
 AssignFile（Outfile，'test_chinese.txt'，CP_UTF8）; 
重写（Outfile）; 
 
 //这是UTF-8 BOM 
写（Outfile，＃$ FEFF）; 
 
 Writeln（Outfile，'总结'）; 
 Writeln（Outfile，'°C'）; 
 CloseFile（Outfile）; 
结束如果您希望在D2009和XE2之间更兼容和更可靠的东西，请使用 
  TStreamWriter 代替：
  procedure TForm1.Button1Click（Sender：TObject）; 
 var 
 Outfile：TStreamWriter; 
 begin 
 Outfile：= TStreamWriter.Create（'test_chinese.txt'，False，TEncoding.UTF8）; 
 try 
 Outfile.WriteLine（'总结'）; 
 Outfile.WriteLine（'°C'）; 
 finally 
 Outfile.Free; 
结束
结束
  
或手动执行文件I / O：
  procedure TForm1.Button1Click（Sender：TObject）; 
 var 
 Outfile：TFileStream; 
 BOM：TBytes; 
 
程序WriteBytes（const B：TBytes）; 
 begin 
如果B& ''然后Outfile.WriteBuffer（B [0]，Length（B））; 
结束
 
程序WriteStr（const S：UTF8String）; 
 begin 
如果S  - ''然后Outfile.WriteBuffer（S [1]，Length（S））; 
结束
 
程序WriteLine（const S：UTF8String）; 
 begin 
 WriteStr（S）; 
 WriteStr（sLineBreak）; 
结束
 
 begin 
 Outfile：= TFileStream.Create（'test_chinese.txt'，fmCreate）; 
 try 
 WriteBytes（TEncoding.UTF8.GetPreamble）; 
 WriteLine（'总结'）; 
 WriteLine（'°C'）; 
 finally 
 Outfile.Free; 
结束
结束
  
 
When I try the code below there seem to be different output in XE2 compared to D2009.
procedure TForm1.Button1Click(Sender: TObject);
var Outfile:textfile;
    myByte: Byte;

begin
  assignfile(Outfile,'test_chinese.txt');
  Rewrite(Outfile);

  for myByte in TEncoding.UTF8.GetPreamble do write(Outfile, AnsiChar(myByte));
  //This is the UTF-8 BOM

  Writeln(Outfile,utf8string('总结'));
  Writeln(Outfile,'°C');
  Closefile(Outfile);
end;
Compiling with XE2 on a Windows 8 PC gives in WordPad

??
 C

txt hex code: EF BB BF 3F 3F 0D 0A B0 43 0D 0A

Compiling with D2009 on a Windows XP PC gives in Wordpad

总结
°C

txt hex code: EF BB BF E6 80 BB E7 BB 93 0D 0A B0 43 0D 0A

My questions is why it differs and how can I save Chinese characters to a text file using the old text file I/O?

Thanks!
解决方案
In XE2 onwards, AssignFile() has an optional CodePage parameter that sets the codepage of the output file:
function AssignFile(var F: File; FileName: String; [CodePage: Word]): Integer; overload;
Write() and Writeln() both have overloads that support UnicodeString and WideChar inputs.

So, you can create a file that has its codepage set to CP_UTF8, and then Write/ln() will automatically convert Unicode strings to UTF-8 when writing them to the file.

The downside is that you will not be able to write the UTF-8 BOM using AnsiChar values anymore, because the individual bytes will get converted to UTF-8 and thus not be written correctly.  You can get around that by writing the BOM as a single Unicode character (which it what it really is - U+FEFF) instead of as individual bytes.

This works in XE2:
procedure TForm1.Button1Click(Sender: TObject);
var
  Outfile: TextFile;
begin
  AssignFile(Outfile, 'test_chinese.txt', CP_UTF8);
  Rewrite(Outfile);

  //This is the UTF-8 BOM
  Write(Outfile, #$FEFF);

  Writeln(Outfile, '总结');
  Writeln(Outfile, '°C');
  CloseFile(Outfile);
end;
With that said, if you want something that is more compatible and reliable between D2009 and XE2, use TStreamWriter instead:
procedure TForm1.Button1Click(Sender: TObject);
var
  Outfile: TStreamWriter;
begin
  Outfile := TStreamWriter.Create('test_chinese.txt', False, TEncoding.UTF8);
  try
    Outfile.WriteLine('总结');
    Outfile.WriteLine('°C');
  finally
    Outfile.Free;
  end;
end;
Or do the file I/O manually:
procedure TForm1.Button1Click(Sender: TObject);
var
  Outfile: TFileStream;
  BOM: TBytes;

  procedure WriteBytes(const B: TBytes);
  begin
    if B <> '' then Outfile.WriteBuffer(B[0], Length(B));
  end;

  procedure WriteStr(const S: UTF8String);
  begin
    if S <> '' then Outfile.WriteBuffer(S[1], Length(S));
  end;

  procedure WriteLine(const S: UTF8String);
  begin
    WriteStr(S);
    WriteStr(sLineBreak);
  end;

begin
  Outfile := TFileStream.Create('test_chinese.txt', fmCreate);
  try
    WriteBytes(TEncoding.UTF8.GetPreamble);
    WriteLine('总结');
    WriteLine('°C');
  finally
    Outfile.Free;
  end;
end;


                        
这篇关于unicode文本文件输出在XE2和Delphi 2009之间有所不同吗？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！