Writing binary file in Inno Setup

Question

How does one write to a binary file in Inno Setup script? It's a configuration file I want to edit in the PrepareToInstall step. The problem is that I'm looking at the support functions:

TStream = class(TObject)
  function Read(Buffer: String; Count: Longint): Longint;
  function Write(Buffer: String; Count: Longint): Longint;
  function Seek(Offset: Longint; Origin: Word): Longint;
  procedure ReadBuffer(Buffer: String; Count: Longint);
  procedure WriteBuffer(Buffer: String; Count: Longint);
  function CopyFrom(Source: TStream; Count: Longint): Longint;
  property Position: Longint; read write;
  property Size: Longint; read write;
end;

And it seems even the most basic write function writes strings. Should I just do it in a batch script?

Answer 1

Consider the string in the TStream interface as a buffer of chars/bytes.

With Ansi version of Inno Setup, it's quite easy, as there one byte equals one char.

It's bit more complicated with Unicode version of Inno Setup, where the string is an array of 2-byte chars.

See also Read bytes from file at desired position with Inno Setup.

To convert a hex string to the actual binary data, you can use the CryptStringToBinary Windows API function.

The following code works both in Ansi and Unicode version of Inno Setup (You should use the Unicode version, if possible).

#ifndef Unicode
const CharSize = 1;
#define AW "A"
#else
const CharSize = 2;
#define AW "W"
#endif

function CryptStringToBinary(
  sz: string; cch: LongWord; flags: LongWord; binary: string; var size: LongWord;
  skip: LongWord; flagsused: LongWord): Integer;
  external 'CryptStringToBinary{#AW}@crypt32.dll stdcall';

const
  CRYPT_STRING_HEX = $04;

procedure WriteHexToFile(Hex: string; FileName: string);
var
  Stream: TFileStream;
  Buffer: string;
  Size: LongWord;
begin
  Stream := TFileStream.Create(FileName, fmCreate);

  try
    SetLength(Buffer, (Length(Hex) div 2*CharSize) + CharSize - 1);
    Size := Length(Hex) div 2;
    if (CryptStringToBinary(
          Hex, Length(Hex), CRYPT_STRING_HEX, Buffer, Size, 0, 0) = 0) or
       (Size <> Length(Hex) div 2) then
    begin
      RaiseException('Error decoding hex string');
    end;

    Stream.WriteBuffer(Buffer, Size);
  finally
    Stream.Free;
  end;
end;

Use it like:

procedure WriteHexToFileTest;
var
  Hex: string;
begin
  Hex :=
    '000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f' + 
    '202122232425262728292a2b2c2d2e2f303132333435363738393a3b3c3d3e3f' + 
    '404142434445464748494a4b4c4d4e4f505152535455565758595a5b5c5d5e5f' + 
    '606162636465666768696a6b6c6d6e6f707172737475767778797a7b7c7d7e7f' + 
    '808182838485868788898a8b8c8d8e8f909192939495969798999a9b9c9d9e9f' + 
    'a0a1a2a3a4a5a6a7a8a9aaabacadaeafb0b1b2b3b4b5b6b7b8b9babbbcbdbebf' + 
    'c0c1c2c3c4c5c6c7c8c9cacbcccdcecfd0d1d2d3d4d5d6d7d8d9dadbdcffffdedf' + 
    'e0e1e2e3e4e5e6e7e8e9eaebecedeeeff0f1f2f3f4f5f6f7f8f9fafbfcfdfeff';

  WriteHexToFile(Hex, 'my_binary_file.dat');
end;