Delphi How to save and read utf-8 text files

To the customer to do a batch image recognition and synthesis of double-layer PDF program, the final customer needs to generate a copy of the Notepad file, is the text after the OCR, and specify the UTF-8 format. There was a little bit of a problem when dealing with utf-8, and now it's summarized as follows

First, the Utf8encode function of Delphi is used to convert ordinary characters to utf-8 encoding.

Create a stream that MemoryStream or FileStream can

The function looks like this

Reference
Procedure Saveutf8file (acontent:widestring; afilename:string);
Var
Ffilestream:tfilestream;
futf8bytes:string;
s:string;
Begin
Ffilestream:=tfilestream.create (afilename,fmcreate);
futf8bytes:= Utf8encode (acontent);
Ffilestream.write (Futf8bytes[1],length (futf8bytes));
Ffilestream.free;
End

After running the view generated files, all garbled, Internet search found

Unicode text file: The first two characters are FF FE (16 binary)
Utf-8 text file: The first two characters are EF BB (16 binary)

I forgot to put the file in the head.

So after adding the code

Reference
Procedure Saveutf8file (acontent:widestring; afilename:string);
Var
Ffilestream:tfilestream;
futf8bytes:string;
s:string;
Begin
Ffilestream:=tfilestream.create (afilename,fmcreate);
futf8bytes:= Utf8encode (acontent);
s:=# $EF # $BB # $BF;
Ffilestream.write (S[1],length (S));
Ffilestream.write (Futf8bytes[1],length (futf8bytes));
Ffilestream.free;
End

After saving the file to view, or garbled. Find a half-day problem finally found that the problem appears in the declaration of the parameter widestring, changed to a string is no problem.

The last generated code is as follows

Reference
Procedure Saveutf8file (acontent:string; afilename:string);
Var
Ffilestream:tfilestream;
futf8bytes:string;
s:string;
Begin
Ffilestream:=tfilestream.create (afilename,fmcreate);
futf8bytes:= Utf8encode (acontent);
s:=# $EF # $BB # $BF;
Ffilestream.write (S[1],length (S));
Ffilestream.write (Futf8bytes[1],length (futf8bytes));
Ffilestream.free;
End

Attach a code that reads Utf-8 text

Reference
function  loadutf8file (afilename:string): string; 
var 
  Ffilestream: tfilestream; 
  fansibytes:string; 
  s:string; 
begin 
  Ffilestream:=tfilestream.create (afilename,fmopenread);  
  SetLength (s,ffilestream.size);  
  Ffilestream.read (S[1],length (S));  
  fansibytes:= Utf8decode (Copy (S,4,maxint));  
  result:= fansibytes; 
End;