Replace a string in a UTF-8 file without BOM in Inno Setup

Question

I need to change some values in a configuration file. The file is UTF-8 without BOM. I need to save it the same way. How do I do it with Inno Setup Unicode edition?

Note:

• Replace a text in a file with Inno Setup doesn't work
• and Create a UTF8 file without BOM with Inno Setup (Unicode version) doesn't show how to read the file correctly.

Answer 1

const
  CP_UTF8 = 65001;

// ...
var
  FileName: string;
  S: string;
begin
  FileName := 'test.txt';
  if not LoadStringFromFileInCP(FileName, S, CP_UTF8) then
  begin
    Log('Error loading the file');
  end
    else
  if StringChangeEx(S, 'žluťoučký kůň', 'ďábelské ódy', True) <= 0 then
  begin
    Log('No value was replaced');
  end
    else
  if not SaveStringToFileInCP(FileName, S, CP_UTF8) then
  begin
    Log('Error writing the file');
  end
    else
  begin
    Log('Replacement successful');
  end;
end;

LoadStringFromFileInCP and SaveStringToFileInCP come from:
Convert array of string to Unicode and back to ANSI in Inno Setup

The code needs Unicode version of Inno Setup (the only version as of Inno Setup 6).
For Unicode string literals, your .iss file must be in UTF-8 encoding with BOM.