【架构师训练营第 1 期】第五周作业

public class ConsistencyHash {
    private SortedMap<Integer, String> hashCircle = new TreeMap<>();    private int virtualNodeCount;
    public ConsistencyHash(List<String> nodeList, int virtualNodeCount) {        this.virtualNodeCount = virtualNodeCount;        nodeList.forEach(this::addNode);    }
    /**     * 算法。     *     * @param digest     * @param nTime     * @return     */    private Long getHash(byte[] digest, int nTime) {        long rv = ((long) (digest[3 + nTime * 4] & 0xFF) << 24)                | ((long) (digest[2 + nTime * 4] & 0xFF) << 16)                | ((long) (digest[1 + nTime * 4] & 0xFF) << 8)                | (digest[0 + nTime * 4] & 0xFF);        /* Truncate to 32-bits */        return rv & 0xffffffffL;    }
    /**     * FNV1_32_HASH算法     */    private int getHash(String str) {        final int p = 16777619;        int hash = (int) 2166136261L;        for (int i = 0; i < str.length(); i++) {            hash = (hash ^ str.charAt(i)) * p;        }        hash += hash << 13;        hash ^= hash >> 7;        hash += hash << 3;        hash ^= hash >> 17;        hash += hash << 5;        // 如果算出来的值为负数则取其绝对值        if (hash < 0) {            hash = Math.abs(hash);        }        return hash;    }
    /**     * 添加节点     * @param node     */    public void addNode(String node) {        if (node == null) {            return;        }        for (int i = 0; i < virtualNodeCount; i++) {            int hash = getHash(node+i);            hashCircle.put(hash, node);            System.out.println(String.format("虚拟节点[ %s ] hash: %s 已添加", i, hash));        }    }    /**     * 获取node节点     * @param     */    public String getNode(String key) {        if (key == null) {            return null;        }        if (hashCircle.isEmpty()) {            return null;        }        int hash = getHash(key);        if (!hashCircle.containsKey(hash)) {            //未命中对应的节点            SortedMap<Integer, String> tailMap = hashCircle.tailMap(hash);            hash = tailMap.isEmpty() ? hashCircle.firstKey() : tailMap.firstKey();        }        return hashCircle.get(hash);    }}