ZeroInputStream.java

package org.shawnz;

import java.io.InputStream;
import java.util.Arrays;

public class ZeroInputStream extends InputStream {

    private final long zeroes;

    private long read;

    public ZeroInputStream() {
        this.zeroes = -1;
    }
    
    public ZeroInputStream(long zeroes) {
        if (zeroes < -1)
            throw new IllegalArgumentException();

        this.zeroes = zeroes;
    }

    public long getZeroes() {
        return zeroes;
    }

    public long getRead() {
        return read;
    }

    @Override
    public int available() {
        if (zeroes < 0)
            return 0;

        if (zeroes - read > Integer.MAX_VALUE)
            return Integer.MAX_VALUE;

        return (int) (zeroes - read);
    }

    @Override
    public int read() {
        if (zeroes >= 0 && read >= zeroes)
            return -1;

        read++;
        return 0;
    }

    @Override
    public int read(byte[] b, int off, int len) {
        if (zeroes >= 0 && read >= zeroes)
            return -1;

        if (off < 0 || len < 0 || len > b.length - off)
            throw new IndexOutOfBoundsException();

        int bytesToWrite = len;
        if (zeroes >= 0 && bytesToWrite > zeroes - read)
            bytesToWrite = (int) (zeroes - read);

        Arrays.fill(b, off, off + bytesToWrite, (byte) 0);

        read += bytesToWrite;
        return bytesToWrite;
    }

    @Override
    public byte[] readNBytes(int len) {
        int bytesToWrite = len;
        if (zeroes >= 0 && bytesToWrite > zeroes - read)
            bytesToWrite = (int) (zeroes - read);

        read += bytesToWrite;
        return new byte[bytesToWrite];
    }

    @Override
    public long skip(long n) {
        long bytesToSkip = n;

        if (zeroes >= 0 && bytesToSkip > zeroes - read)
            bytesToSkip = zeroes - read;

        read += bytesToSkip;
        return bytesToSkip;
    }
}