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Disruptor - Concurrent Programming Framework
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/*
 * Copyright 2012 LMAX Ltd.
 *
 * Licensed 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.lmax.disruptor;

/**
 * Coordinates claiming sequences for access to a data structure while tracking dependent {@link Sequence}s
 */
public interface Sequencer extends Cursored
{
    /** Set to -1 as sequence starting point */
    long INITIAL_CURSOR_VALUE = -1L;

    /**
     * The capacity of the data structure to hold entries.
     *
     * @return the size of the RingBuffer.
     */
    int getBufferSize();

    /**
     * Has the buffer got capacity to allocate another sequence.  This is a concurrent
     * method so the response should only be taken as an indication of available capacity.
     * @param requiredCapacity in the buffer
     * @return true if the buffer has the capacity to allocate the next sequence otherwise false.
     */
    boolean hasAvailableCapacity(final int requiredCapacity);

    /**
     * Claim the next event in sequence for publishing.
     * @return the claimed sequence value
     */
    long next();

    /**
     * Claim the next n events in sequence for publishing.  This is for batch event producing.  Using batch producing
     * requires a little care and some math.
     *      * int n = 10;
     * long hi = sequencer.next(n);
     * long lo = hi - (n - 1);
     * for (long sequence = lo; sequence <= hi; sequence++) {
     *     // Do work.
     * }
     * sequencer.publish(lo, hi);
     * 
     *
     * @param n the number of sequences to claim
     * @return the highest claimed sequence value
     */
    long next(int n);

    /**
     * Attempt to claim the next event in sequence for publishing.  Will return the
     * number of the slot if there is at least requiredCapacity slots
     * available.
     * @return the claimed sequence value
     * @throws InsufficientCapacityException
     */
    long tryNext() throws InsufficientCapacityException;

    /**
     * Attempt to claim the next n events in sequence for publishing.  Will return the
     * highest numbered slot if there is at least requiredCapacity slots
     * available.  Have a look at {@link Sequencer#next()} for a description on how to
     * use this method.
     *
     * @param n the number of sequences to claim
     * @return the claimed sequence value
     * @throws InsufficientCapacityException
     */
    long tryNext(int n) throws InsufficientCapacityException;

    /**
     * Get the remaining capacity for this sequencer.
     * @return The number of slots remaining.
     */
    long remainingCapacity();

    /**
     * Claim a specific sequence.  Only used if initialising the ring buffer to
     * a specific value.
     *
     * @param sequence The sequence to initialise too.
     */
    void claim(long sequence);

    /**
     * Publishes a sequence. Call when the event has been filled.
     *
     * @param sequence
     */
    void publish(long sequence);

    /**
     * Batch publish sequences.  Called when all of the events have been filled.
     *
     * @param lo first sequence number to publish
     * @param hi last sequence number to publish
     */
    void publish(long lo, long hi);

    /**
     * Confirms if a sequence is published and the event is available for use; non-blocking.
     *
     * @param sequence of the buffer to check
     * @return true if the sequence is available for use, false if not
     */
    boolean isAvailable(long sequence);

    /**
     * Add the specified gating sequences to this instance of the Disruptor.  They will
     * safely and atomically added to the list of gating sequences.
     *
     * @param gatingSequences The sequences to add.
     */
    void addGatingSequences(Sequence... gatingSequences);

    /**
     * Remove the specified sequence from this sequencer.
     *
     * @param sequence to be removed.
     * @return true if this sequence was found, false otherwise.
     */
    boolean removeGatingSequence(Sequence sequence);

    /**
     * Create a new SequenceBarrier to be used by an EventProcessor to track which messages
     * are available to be read from the ring buffer given a list of sequences to track.
     *
     * @see SequenceBarrier
     * @param sequencesToTrack
     * @return A sequence barrier that will track the specified sequences.
     */
    SequenceBarrier newBarrier(Sequence... sequencesToTrack);

    /**
     * Get the minimum sequence value from all of the gating sequences
     * added to this ringBuffer.
     *
     * @return The minimum gating sequence or the cursor sequence if
     * no sequences have been added.
     */
    long getMinimumSequence();

    long getHighestPublishedSequence(long sequence, long availableSequence);
}