io.virtdata.libbasics.shared.from_long.to_int.HashedLineToInt Maven / Gradle / Ivy

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With inspiration from other libraries

There is a newer version: 2.12.15

package io.virtdata.libbasics.shared.from_long.to_int;

import io.virtdata.annotations.ThreadSafeMapper;
import io.virtdata.util.VirtDataResources;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.List;
import java.util.function.LongToIntFunction;

/**
 * Return a pseudo-randomly selected integer value from a file of numeric values.
 * Each line in the file must contain one parsable integer value.
 */
@ThreadSafeMapper
public class HashedLineToInt implements LongToIntFunction {
    private final static Logger logger = LoggerFactory.getLogger(HashedLineToInt.class);

    private int[] values;
    private final String filename;
    private final Hash intHash;

    public HashedLineToInt(String filename) {
        this.filename = filename;
        List lines = VirtDataResources.readDataFileLines(filename);
        this.values = lines.stream().mapToInt(Integer::parseInt).toArray();
        this.intHash = new Hash();
    }

    public String toString() {
        return getClass().getSimpleName() + ":" + filename;
    }

    @Override
    public int applyAsInt(long value) {
        int itemIdx = intHash.applyAsInt(value) % values.length;
        return values[itemIdx];
    }
}