Strange behaviour with mmfile

[bioinfornatics]

I missed to show the code

$ cat test_mmap.d
import std.stdio;
import std.mmfile;

void main(string[] args ){
    MmFile m = new MmFile( args[0] );
    foreach( ulong c; 0..m.length )
        writeln( m[c], " ", cast(dchar) m[c] );
}