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QuestDB is High Performance Time Series Database

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 * Copyright (C) 2014-2016 Appsicle
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 * This program is free software: you can redistribute it and/or  modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 *
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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package com.questdb.iter;

import com.questdb.Journal;
import com.questdb.Partition;
import com.questdb.ex.JournalException;
import com.questdb.ex.JournalRuntimeException;
import com.questdb.std.AbstractImmutableIterator;

public class PartitionBufferedIterator extends AbstractImmutableIterator implements JournalIterator, PeekingIterator {
    private final long hi;
    private final long lo;
    private final T obj;
    private final Partition partition;
    private long cursor;

    public PartitionBufferedIterator(Partition partition, long lo, long hi) {
        this.lo = lo;
        this.cursor = lo;
        this.hi = hi;
        this.obj = partition.getJournal().newObject();
        this.partition = partition;
    }

    @Override
    public Journal getJournal() {
        return partition.getJournal();
    }

    @Override
    public boolean hasNext() {
        return cursor <= hi;
    }

    @Override
    public T next() {
        return get(cursor++);
    }

    @Override
    public boolean isEmpty() {
        return cursor > hi;
    }

    @Override
    public T peekFirst() {
        return get(lo);
    }

    @Override
    public T peekLast() {
        return get(hi);
    }

    private T get(long localRowID) {
        try {
            if (!partition.isOpen()) {
                partition.open();
            }
            partition.read(localRowID, obj);
            return obj;
        } catch (JournalException e) {
            throw new JournalRuntimeException("Cannot read partition " + partition + " at " + localRowID, e);
        }
    }
}