第五周作业

public interface HashAlgorithm {
	public int getHash(String v);
}

public class FNV1A32HashAlgorithm implements HashAlgorithm{
	private static final long FNV_32_INIT = 2166136261L;  
	private static final long FNV_32_PRIME = 16777619;  
	
	public int getHash(String v) {
		int hash = (int)FNV_32_INIT;  
        int len = v.length();  
        for (int i = 0; i < len; i++) {  
        	hash ^= v.charAt(i);  
        	hash *= FNV_32_PRIME;  
        }
        hash += hash << 13;
        hash ^= hash >> 7;
        hash += hash << 3;
        hash ^= hash >> 17;
        hash += hash << 5;

        if (hash < 0)
            hash = Math.abs(hash);
        
		return hash;
	}
}

public class HashRing {
	private HashAlgorithm ha;
	private int vns;
	private static SortedMap<Integer, String> virtualNodes = new TreeMap<Integer, String>();
	
	public HashRing() {
		this(200, new FNV1A32HashAlgorithm());
	}
	
	public HashRing(int vns) {
		this(vns, new FNV1A32HashAlgorithm());
	}
	
	public HashRing(int vns, HashAlgorithm ha ) {
		this.vns = vns;
		this.ha = ha;
	}
	
	public void addServer(String server) {
		for(int i=0; i<vns; i++){
            String virtualNodeName = server + "##" + i;
            int hash = ha.getHash(virtualNodeName);
            virtualNodes.put(hash, virtualNodeName);           
        }
	}
	
	public int getHash(String data) {
		return ha.getHash(data);
	}
	
	public String getServer(String data) {
        int hash = ha.getHash(data);
        SortedMap<Integer, String> subMap = virtualNodes.tailMap(hash);
        String virtualNode;
        if(subMap.isEmpty()){
        	Integer i = virtualNodes.firstKey();
        	virtualNode = virtualNodes.get(i);
        }else{
        	Integer i = subMap.firstKey();
        	virtualNode = subMap.get(i);
        }
        if(virtualNode.length() > 0){
            return virtualNode.substring(0, virtualNode.indexOf("##"));
        }
        return null;
	}

 }