MappedResizableBuffer for read-only files

[darthninja1]

The IoUtil.map call assumes you have r/w access to the file. I have a usecase where I need to mmap a read-only file generated by a different process. Could you add support for read-only files?

I locally modified the below line in MappedResizableBuffer and it seems to work fine now -

addressOffset = IoUtil.map(fileChannel, FileChannel.MapMode.READ_ONLY, offset, length);

[mjpt777]

Why do you need a resizable buffer if read only? Why not do a normally mapping and wrap with UnsafeBuffer?

[darthninja1]

Because UnsafeBuffer takes integer offsets (afaik). I have to mmap a file > 2GB. And I want to avoid re-wrapping different sections of the file.