Faster hex decoder

import java.util.Arrays;
import java.util.function.IntUnaryOperator;

public class FasterHex {

    private FasterHex() {}

    private static final short[] DECODE_TABLE = new short[13_159]; // ('f' << 7) + 'f' + 1

    static {
        Arrays.fill(DECODE_TABLE, (byte) -1);
        insertAll('0', '9');
        insertAll('A', 'F');
        insertAll('a', 'f');
    }

    private static void insertAll(int start, int end) {
        for (int i = start; i <= end; i++) {
            for (int j = '0'; j <= '9'; j++) insert(i, j);
            for (int j = 'A'; j <= 'F'; j++) insert(i, j);
            for (int j = 'a'; j <= 'f'; j++) insert(i, j);
        }
    }

    private static void insert(int i, int j) {
        // ASCII values are at most 7 bits
        DECODE_TABLE[i << 7 | j] = (short) (decodeNibble(i) << 4 | decodeNibble(j));
    }

    private static int decodeNibble(int c) {
        switch (c) {
        case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': return c - '0';
        case 'A': case 'B': case 'C': case 'D': case 'E': case 'F': return  c - ('A' - 0xA);
        case 'a': case 'b': case 'c': case 'd': case 'e': case 'f': return c - ('a' - 0xa);
        default: throw new AssertionError();
        }
    }

    public static byte[] decode(int offset, int len, IntUnaryOperator extractor) {
        byte[] dest = new byte[len / 2];
        for (int i = 0; i < dest.length; i++, offset += 2) {
            dest[i] = (byte) decodeByte(extractor, offset);
        }
        return dest;
    }

    private static short decodeByte(IntUnaryOperator extractor, int offset) {
        try {
            short val = DECODE_TABLE[extractor.applyAsInt(offset) << 7 | extractor.applyAsInt(offset+1)];
            if(val >= 0) {
                return val;
            }
        } catch (ArrayIndexOutOfBoundsException ignored) {
            /* fall through */
        }
        throw new IllegalArgumentException("invalid hex pair @ " + offset);
    }
}