public synchronized int getNextBlockOffset() {
		for(int i = 0; i < this.blockOffsets.length; i++){
			if(this.blocks.containsKey(blockOffsets[i]))
				continue;
			if(System.currentTimeMillis() - this.blockLastRequested[i] < 500)
				continue;
			this.blockLastRequested[i] = System.currentTimeMillis();
			return blockOffsets[i];
		}
		
		return -1;
	}