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A driver for DataStax Enterprise (DSE) and Apache Cassandra 1.2+ clusters that works exclusively with the Cassandra Query Language version 3 (CQL3) and Cassandra's binary protocol, supporting DSE-specific features such as geospatial types, DSE Graph and DSE authentication.

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/*
 * Copyright DataStax, Inc.
 *
 * This software can be used solely with DataStax Enterprise. Please consult the license at
 * http://www.datastax.com/terms/datastax-dse-driver-license-terms
 */
package com.datastax.driver.core;

import com.datastax.driver.core.exceptions.DriverInternalError;

public enum ConsistencyLevel {

    ANY(0),
    ONE(1),
    TWO(2),
    THREE(3),
    QUORUM(4),
    ALL(5),
    LOCAL_QUORUM(6),
    EACH_QUORUM(7),
    SERIAL(8),
    LOCAL_SERIAL(9),
    LOCAL_ONE(10);

    // Used by the native protocol
    final int code;
    private static final ConsistencyLevel[] codeIdx;

    static {
        int maxCode = -1;
        for (ConsistencyLevel cl : ConsistencyLevel.values())
            maxCode = Math.max(maxCode, cl.code);
        codeIdx = new ConsistencyLevel[maxCode + 1];
        for (ConsistencyLevel cl : ConsistencyLevel.values()) {
            if (codeIdx[cl.code] != null)
                throw new IllegalStateException("Duplicate code");
            codeIdx[cl.code] = cl;
        }
    }

    private ConsistencyLevel(int code) {
        this.code = code;
    }

    static ConsistencyLevel fromCode(int code) {
        if (code < 0 || code >= codeIdx.length)
            throw new DriverInternalError(String.format("Unknown code %d for a consistency level", code));
        return codeIdx[code];
    }

    /**
     * Whether or not this consistency level applies to the local data-center only.
     *
     * @return whether this consistency level is {@code LOCAL_ONE} or {@code LOCAL_QUORUM}.
     */
    public boolean isDCLocal() {
        return this == LOCAL_ONE || this == LOCAL_QUORUM;
    }

    /**
     * Whether or not this consistency level is serial, that is,
     * applies only to the "paxos" phase of a
     * Lightweight transaction.
     * 
     * Serial consistency levels are only meaningful when executing conditional updates ({@code INSERT}, {@code UPDATE}
     * or {@code DELETE} statements with an {@code IF} condition).
     * 
     * Two consistency levels belong to this category: {@link #SERIAL} and {@link #LOCAL_SERIAL}.
     *
     * @return whether this consistency level is {@link #SERIAL} or {@link #LOCAL_SERIAL}.
     * @see Statement#setSerialConsistencyLevel(ConsistencyLevel)
     * @see Lightweight transactions
     */
    public boolean isSerial() {
        return this == SERIAL || this == LOCAL_SERIAL;
    }

}