io.geewit.snowflake.BitsAllocator Maven / Gradle / Ivy

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package io.geewit.snowflake;


/**
 * Allocate 64 bits for the UID(long)

 * sign (fixed 1bit) -> deltaSecond -> workerId -> sequence(within the same second)
 *
 * @author geewit
 */
public class BitsAllocator {
    /**
     * Total 64 bits
     */
    public static final int TOTAL_BITS = 1 << 6;
    private final int timestampBits;
    private final int workerIdBits;
    private final int sequenceBits;
    /**
     * Max value for workId & sequence
     */
    private final long maxDeltaSeconds;
    private final long maxWorkerId;
    private final long maxSequence;
    /**
     * Shift for timestamp & workerId
     */
    private final int timestampShift;
    private final int workerIdShift;
    /**
     * Bits for [sign-> second-> workId-> sequence]
     */
    private final int signBits = 1;

    /**
     * Constructor with timestampBits, workerIdBits, sequenceBits

     * The highest bit used for sign, so 63 bits for timestampBits, workerIdBits, sequenceBits
     */
    public BitsAllocator(int timestampBits, int workerIdBits, int sequenceBits) {
        // make sure allocated 64 bits
        int allocateTotalBits = signBits + timestampBits + workerIdBits + sequenceBits;
        assert allocateTotalBits == TOTAL_BITS : "allocate not enough 64 bits";

        // initialize bits
        this.timestampBits = timestampBits;
        this.workerIdBits = workerIdBits;
        this.sequenceBits = sequenceBits;

        // initialize max value
        this.maxDeltaSeconds = ~(-1L << timestampBits);
        this.maxWorkerId = ~(-1L << workerIdBits);
        this.maxSequence = ~(-1L << sequenceBits);

        // initialize shift
        this.timestampShift = workerIdBits + sequenceBits;
        this.workerIdShift = sequenceBits;
    }

    /**
     * Allocate bits for UID according to delta seconds & workerId & sequence

     * Note that: The highest bit will always be 0 for sign
     *
     * @param deltaSeconds
     * @param workerId
     * @param sequence
     * @return
     */
    public long allocate(long deltaSeconds, long workerId, long sequence) {
        return (deltaSeconds << timestampShift) | (workerId << workerIdShift) | sequence;
    }

    /**
     * Getters
     */
    public int getSignBits() {
        return signBits;
    }

    public int getTimestampBits() {
        return timestampBits;
    }

    public int getWorkerIdBits() {
        return workerIdBits;
    }

    public int getSequenceBits() {
        return sequenceBits;
    }

    public long getMaxDeltaSeconds() {
        return maxDeltaSeconds;
    }

    public long getMaxWorkerId() {
        return maxWorkerId;
    }

    public long getMaxSequence() {
        return maxSequence;
    }

    public int getTimestampShift() {
        return timestampShift;
    }

    public int getWorkerIdShift() {
        return workerIdShift;
    }

    @Override
    public String toString() {
        return "BitsAllocator{" +
                "signBits=" + signBits +
                ", timestampBits=" + timestampBits +
                ", workerIdBits=" + workerIdBits +
                ", sequenceBits=" + sequenceBits +
                ", maxDeltaSeconds=" + maxDeltaSeconds +
                ", maxWorkerId=" + maxWorkerId +
                ", maxSequence=" + maxSequence +
                ", timestampShift=" + timestampShift +
                ", workerIdShift=" + workerIdShift +
                '}';
    }
}