Erwan's Blog

In a previous article, I have shared a delphi unit for libewf.

Now lets code a proxy for ImDisk using that external libyal library to mount an EWF file.

I initially used this template from reboot.pro and came with the below basic delphi unit.

Once I had done that, it was pretty easy to fill in the missing parts to mount and EWF reusing my previous libewf delphi unit.
See code attached.proxy_EWF

library proxy;

uses
  SysUtils,
  Classes,windows;

{$R *.res}

type
  dllread_proc = function (handle:thandle; buf:pointer; size:cardinal; offset:int64): integer; cdecl;
  dllwrite_proc = function (handle:thandle; buf:pointer; size:cardinal; offset:int64): integer; cdecl;
  dllclose_proc = function (handle:thandle): integer; cdecl;

var
file_handle:thandle;

function SetFilePointerEx (hFile: THandle; lDistanceToMove: int64; lpNewFilePointer: Pointer; dwMoveMethod: DWORD): BOOL; stdcall; external 'kernel32.dll';
function GetFileSizeEx(hFile: THandle; var lpFileSize: Int64): BOOL; stdcall; external 'kernel32.dll' name 'GetFileSizeEx';

function my_read_proc(handle:thandle; buf:pointer; size:cardinal; offset:int64): integer; cdecl;
var
bytes_read:cardinal;
begin
	writeln('Read request - size:'+inttostr(size)+' offset:'+inttostr(offset));
	SetFilePointerEx(handle, offset, nil, FILE_BEGIN);
	ReadFile(handle, buf^, size, bytes_read, nil);
	result:=bytes_read;
end;

function my_write_proc(handle:thandle; buf:pointer; size:cardinal; offset:int64): integer; cdecl;
var
bytes_written:cardinal;
begin
	writeln('Write request - size:'+inttostr(size)+' offset:'+inttostr(offset));
	SetFilePointerEx(handle, offset, nil, FILE_BEGIN);
	WriteFile(handle, buf^, size, bytes_written, nil);
	result:=bytes_written;
end;

function my_close_proc(handle:thandle): integer; cdecl;
begin
	writeln('Close request');
	CloseHandle(handle);
	result:=0;
end;

function dllopen(filename:pchar; read_only:integer; var dllread:dllread_proc; var dllwrite:dllwrite_proc; var dllclose:dllclose_proc; var size:int64):thandle;cdecl;
begin
	writeln('File to open: '+filename);

	dllread := my_read_proc;
	dllwrite := my_write_proc;
	dllclose := my_close_proc;

	file_handle := CreateFile(filename, GENERIC_READ or GENERIC_WRITE, FILE_SHARE_READ, nil, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
	GetFileSizeEx(file_handle, size);

	result:=file_handle;
end;

exports
  dllopen index 1;

begin
end.

The command lines for the proxy and ImDisk are below :

devio --dll=proxy.dll;dllopen shm:test_proxy c:\test.vmdk
imdisk -a -t proxy -o shm -o ro -f test_proxy -m Z:

Devio in action :