io.deephaven.engine.table.impl.join.dupcompact.CharReverseDupCompactKernel Maven / Gradle / Ivy

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/**
 * Copyright (c) 2016-2022 Deephaven Data Labs and Patent Pending
 */
package io.deephaven.engine.table.impl.join.dupcompact;

import io.deephaven.chunk.*;
import io.deephaven.chunk.attributes.Any;
import io.deephaven.chunk.attributes.ChunkPositions;
import io.deephaven.engine.rowset.chunkattributes.RowKeys;
import org.jetbrains.annotations.NotNull;

public class CharReverseDupCompactKernel implements DupCompactKernel {

    static final CharReverseDupCompactKernel INSTANCE = new CharReverseDupCompactKernel();

    private CharReverseDupCompactKernel() {
        // Use the singleton INSTANCE
    }

    @Override
    public int compactDuplicates(
            @NotNull final WritableChunk chunkToCompact,
            @NotNull final WritableLongChunk rowKeys) {
        return compactDuplicates(chunkToCompact.asWritableCharChunk(), rowKeys);
    }

    @Override
    public int compactDuplicatesPreferFirst(
            @NotNull final WritableChunk chunkToCompact,
            @NotNull final WritableIntChunk chunkPositions) {
        return compactDuplicatesPreferFirst(chunkToCompact.asWritableCharChunk(), chunkPositions);
    }

    private static int compactDuplicates(
            @NotNull final WritableCharChunk chunkToCompact,
            @NotNull final WritableLongChunk rowKeys) {
        final int inputSize = chunkToCompact.size();
        if (inputSize == 0) {
            return -1;
        }

        int wpos = 0;
        int rpos = 0;

        char last = chunkToCompact.get(0);

        while (rpos < inputSize) {
            final char current = chunkToCompact.get(rpos);
            if (!leq(last, current)) {
                return rpos;
            }
            last = current;

            while (rpos < inputSize - 1 && eq(current, chunkToCompact.get(rpos + 1))) {
                rpos++;
            }
            chunkToCompact.set(wpos, current);
            rowKeys.set(wpos, rowKeys.get(rpos));
            rpos++;
            wpos++;
        }
        chunkToCompact.setSize(wpos);
        rowKeys.setSize(wpos);

        return -1;
    }

    private static int compactDuplicatesPreferFirst(
            @NotNull final WritableCharChunk chunkToCompact,
            @NotNull final WritableIntChunk chunkPositions) {
        final int inputSize = chunkToCompact.size();
        if (inputSize == 0) {
            return -1;
        }

        int wpos = 0;
        int rpos = 0;

        char last = chunkToCompact.get(0);

        while (rpos < inputSize) {
            final char current = chunkToCompact.get(rpos);
            if (!leq(last, current)) {
                return rpos;
            }
            last = current;

            chunkToCompact.set(wpos, current);
            chunkPositions.set(wpos, chunkPositions.get(rpos));
            rpos++;
            wpos++;

            while (rpos < inputSize && eq(current, chunkToCompact.get(rpos))) {
                rpos++;
            }
        }
        chunkToCompact.setSize(wpos);
        chunkPositions.setSize(wpos);

        return -1;
    }

    // region comparison functions
    // note that this is a descending kernel, thus the comparisons here are backwards (e.g., the lt function is in terms of the sort direction, so is implemented by gt)
    private static int doComparison(char lhs, char rhs) {
        return -1 * Character.compare(lhs, rhs);
    }
    // endregion comparison functions

    private static boolean leq(char lhs, char rhs) {
        return doComparison(lhs, rhs) <= 0;
    }

    private static boolean eq(char lhs, char rhs) {
        // region equality function
        return lhs == rhs;
        // endregion equality function
    }
}