@Override
	public long length( ) throws IOException {
		int length = 0;
		for ( Program program : programs ) {
			length += program.getMemory().getSize( );
		}
		return length;
	}
TODO
Check to make sure programs are disjoint and contiguous memory spaces.
Ghidra/Features/FileFormats/src/main/java/ghidra/file/formats/ext4/MultiProgramMemoryByteProvider.java