Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
import java.math.BigInteger;

public class Main {
    public static int[] generateCompactNaf(BigInteger k) {
        if ((k.bitLength() >>> 16) != 0) {
            throw new IllegalArgumentException("'k' must have bitlength < 2^16");
        }

        BigInteger _3k = k.shiftLeft(1).add(k);

        int digits = _3k.bitLength() - 1;
        int[] naf = new int[(digits + 1) >> 1];

        int length = 0, zeroes = 0;
        for (int i = 1; i <= digits; ++i) {
            boolean _3kBit = _3k.testBit(i);
            boolean kBit = k.testBit(i);

            if (_3kBit == kBit) {
                ++zeroes;
            } else {
                int digit = kBit ? -1 : 1;
                naf[length++] = (digit << 16) | zeroes;
                zeroes = 0;
            }
        }

        if (naf.length > length) {
            naf = trim(naf, length);
        }

        return naf;
    }

    private static byte[] trim(byte[] a, int length) {
        byte[] result = new byte[length];
        System.arraycopy(a, 0, result, 0, result.length);
        return result;
    }

    private static int[] trim(int[] a, int length) {
        int[] result = new int[length];
        System.arraycopy(a, 0, result, 0, result.length);
        return result;
    }
}