/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.alibaba.jstorm.common.metric.codahale;

import java.io.Serializable;

public class LongAdder extends Striped64 implements Serializable {
    @SuppressWarnings("all")
    private static final long serialVersionUID = 7249069246863182397L;

    /**
     * Version of plus for use in retryUpdate
     */
    final long fn(long v, long x) {
        return v + x;
    }

    /**
     * Creates a new adder with initial sum of zero.
     */
    LongAdder() {
    }

    /**
     * Adds the given value.
     *
     * @param x the value to add
     */
    public void add(long x) {
        Cell[] as;
        long b, v;
        HashCode hc;
        Cell a;
        int n;
        if ((as = cells) != null || !casBase(b = base, b + x)) {
            boolean uncontended = true;
            int h = (hc = threadHashCode.get()).code;
            if (as == null || (n = as.length) < 1 ||
                    (a = as[(n - 1) & h]) == null ||
                    !(uncontended = a.cas(v = a.value, v + x)))
                retryUpdate(x, hc, uncontended);
        }
    }

    /**
     * Equivalent to {@code add(1)}.
     */
    public void increment() {
        add(1L);
    }

    /**
     * Equivalent to {@code add(-1)}.
     */
    public void decrement() {
        add(-1L);
    }

    /**
     * Returns the current sum.  The returned value is <em>NOT</em> an atomic snapshot; invocation
     * in the absence of concurrent updates returns an accurate result, but concurrent updates that
     * occur while the sum is being calculated might not be incorporated.
     *
     * @return the sum
     */
    public long sum() {
        long sum = base;
        Cell[] as = cells;
        if (as != null) {
            int n = as.length;
            for (int i = 0; i < n; ++i) {
                Cell a = as[i];
                if (a != null)
                    sum += a.value;
            }
        }
        return sum;
    }

    /**
     * Resets variables maintaining the sum to zero.  This method may be a useful alternative to
     * creating a new adder, but is only effective if there are no concurrent updates.  Because this
     * method is intrinsically racy, it should only be used when it is known that no threads are
     * concurrently updating.
     */
    public void reset() {
        internalReset(0L);
    }

    /**
     * Equivalent in effect to {@link #sum} followed by {@link #reset}. This method may apply for
     * example during quiescent points between multithreaded computations.  If there are updates
     * concurrent with this method, the returned value is <em>not</em> guaranteed to be the final
     * value occurring before the reset.
     *
     * @return the sum
     */
    public long sumThenReset() {
        long sum = base;
        Cell[] as = cells;
        base = 0L;
        if (as != null) {
            int n = as.length;
            for (int i = 0; i < n; ++i) {
                Cell a = as[i];
                if (a != null) {
                    sum += a.value;
                    a.value = 0L;
                }
            }
        }
        return sum;
    }

    /**
     * Returns the String representation of the {@link #sum}.
     *
     * @return the String representation of the {@link #sum}
     */
    public String toString() {
        return Long.toString(sum());
    }

    /**
     * Equivalent to {@link #sum}.
     *
     * @return the sum
     */
    public long longValue() {
        return sum();
    }

    /**
     * Returns the {@link #sum} as an {@code int} after a narrowing primitive conversion.
     */
    public int intValue() {
        return (int) sum();
    }

    /**
     * Returns the {@link #sum} as a {@code float} after a widening primitive conversion.
     */
    public float floatValue() {
        return (float) sum();
    }

    /**
     * Returns the {@link #sum} as a {@code double} after a widening primitive conversion.
     */
    public double doubleValue() {
        return (double) sum();
    }

    private void writeObject(java.io.ObjectOutputStream s)
            throws java.io.IOException {
        s.defaultWriteObject();
        s.writeLong(sum());
    }

    private void readObject(java.io.ObjectInputStream s)
            throws java.io.IOException, ClassNotFoundException {
        s.defaultReadObject();
        busy = 0;
        cells = null;
        base = s.readLong();
    }
}