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QuestDB is high performance SQL time series database
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 *  Copyright (c) 2014-2019 Appsicle
 *  Copyright (c) 2019-2024 QuestDB
 *
 *  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
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package io.questdb.cairo.map;

import io.questdb.cairo.sql.Record;
import io.questdb.cairo.sql.SqlExecutionCircuitBreaker;
import io.questdb.std.Unsafe;
import io.questdb.std.bytes.Bytes;

public final class OrderedMapCursor implements MapRecordCursor {
    // Set to -1 when key-value pair is var-size.
    private final long alignedKeyValueSize;
    private final OrderedMap map;
    private final OrderedMapRecord recordA;
    private final OrderedMapRecord recordB;
    private final long valueSize;
    private long address;
    private int count;
    private int remaining;
    private long topAddress;

    OrderedMapCursor(OrderedMapRecord record, OrderedMap map) {
        this.recordA = record;
        this.recordB = record.clone();
        this.map = map;
        this.valueSize = map.valueSize();
        if (map.keySize() != -1) {
            alignedKeyValueSize = Bytes.align8b(map.keySize() + map.valueSize());
        } else {
            alignedKeyValueSize = -1;
        }
    }

    @Override
    public void calculateSize(SqlExecutionCircuitBreaker circuitBreaker, Counter counter) {
        if (remaining > 0) {
            counter.add(remaining);
            remaining = 0;
        }
    }

    @Override
    public void close() {
        // no-op
    }

    @Override
    public MapRecord getRecord() {
        return recordA;
    }

    @Override
    public MapRecord getRecordB() {
        return recordB;
    }

    @Override
    public boolean hasNext() {
        if (remaining > 0) {
            recordA.of(address);
            if (alignedKeyValueSize == -1) {
                int keySize = Unsafe.getUnsafe().getInt(address);
                address = Bytes.align8b(address + OrderedMap.VAR_KEY_HEADER_SIZE + keySize + valueSize);
            } else {
                address += alignedKeyValueSize;
            }
            remaining--;
            return true;
        }
        return false;
    }

    @Override
    public void recordAt(Record record, long atRowId) {
        ((OrderedMapRecord) record).of(atRowId);
    }

    @Override
    public long size() {
        return map.size();
    }

    @Override
    public void toTop() {
        address = topAddress;
        remaining = count;
    }

    OrderedMapCursor init(long address, long limit, int count) {
        this.address = this.topAddress = address;
        this.remaining = this.count = count;
        recordA.setLimit(limit);
        recordB.setLimit(limit);
        return this;
    }
}