Main.java

package com.company;

import java.util.ArrayList;
import java.util.List;

public class Main {

    public static void main(String[] args) {
        System.out.println(read_vi32(write_vi32(0)));
    }

    static int read_vi32(byte[] bytes) {
        int value = 0;
        int bytePart = 0;
        boolean still;
        int pos = 0;

        while (bytePart < Integer.SIZE) {
            int curr = bytes[pos++];
            still = (curr & 0b10000000) == 0b10000000;

            if (bytePart > 0)
                value += ((curr & 0b01111111) << bytePart);
            else
                value += (curr & 0b01111111);

            bytePart += 7;

            if (!still)
                return value;
        }

        throw new Error("Too much data");
    }

    static byte[] write_vi32(int value) {
        if (((value >= 0)) && ((value <= 0b01111111))) {
            return new byte[] {(byte) value};
        }

        byte bytePart;
        int intPart = value;

        List<Byte> bytes = new ArrayList<>();
        while (intPart != 0) {
            bytePart = (byte) (intPart & 0b01111111);
            intPart >>>= 7;
            if (intPart > 0)
                bytePart |= 0b10000000;

            bytes.add(bytePart);
        }
        byte[] array = new byte[bytes.size()];
        for (int i = 0; i < bytes.size(); i++)
            array[i] = bytes.get(i);
        return array;
    }
}