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Fork of https://github.com/airlift/aircompressor (zstd only). This module is temporary until we get an official release that includes the ZstdInputStream API (which is already implemented by two different people but neither PR shows any progress).

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/*
 * 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 ai.vespa.airlift.zstd;

import java.util.Arrays;

class BlockCompressionState
{
    public final int[] hashTable;
    public final int[] chainTable;

    private final long baseAddress;

    // starting point of the window with respect to baseAddress
    private int windowBaseOffset;

    public BlockCompressionState(CompressionParameters parameters, long baseAddress)
    {
        this.baseAddress = baseAddress;
        hashTable = new int[1 << parameters.getHashLog()];
        chainTable = new int[1 << parameters.getChainLog()]; // TODO: chain table not used by Strategy.FAST
    }

    public void reset()
    {
        Arrays.fill(hashTable, 0);
        Arrays.fill(chainTable, 0);
    }

    public void enforceMaxDistance(long inputLimit, int maxDistance)
    {
        int distance = (int) (inputLimit - baseAddress);

        int newOffset = distance - maxDistance;
        if (windowBaseOffset < newOffset) {
            windowBaseOffset = newOffset;
        }
    }

    public long getBaseAddress()
    {
        return baseAddress;
    }

    public int getWindowBaseOffset()
    {
        return windowBaseOffset;
    }
}