按照bit读取或写入java的IO流

写了个按照bit读取或写入java的IO流的简单代码，保留在博客里备忘。

/**
 * 按bit读取的input。
 * */
public class BitInput {

    private InputStream input;
    private int         value;
    private int         next = 7;

    public BitInput(InputStream input) {
        this.input = input;
    }

    /**
     * 读取一个bit,1,0,-1(文件结束)。
     * */
    public int readBit() throws Exception {

        if (next == 7) {
            value = input.read();
            if (value == -1) {
                return -1;
            }
        }

        int result = (value & (1 << next)) >>> next;
        next--;

        if (next == -1) {
            next = 7;
        }

        return result;
    }

    /**
     * 读取size个bit。
     * */
    public int[] readBits(int size) throws Exception {
        int[] result = new int[size];
        for (int i = 0; i < size; i++) {
            int v = readBit();
            if (v == -1) {
                throw new RuntimeException();
            }
            result[i] = v;
        }
        return result;
    }
}

/**
 * 按bit写出的output。
 * */
public class BitOutput {

    private OutputStream out;
    private int          value;
    private int          next = 7;

    public BitOutput(OutputStream out) {
        this.out = out;
    }

    public void writeBitOne() throws Exception {
        write(1);
    }

    public void writeBitZero() throws Exception {
        write(0);
    }

    private void write(int bit) throws Exception {
        value = value | (bit << next);
        next--;

        if (next < 0) {
            out.write(value);
            value = 0;
            next = 7;
        }
    }

    public void writeBits(String bits) throws Exception {
        for (int i = 0; i < bits.length(); i++) {
            char v = bits.charAt(i);
            if (v == '0' || v == '1') {
                write(v - '0');
                continue;
            }
            throw new RuntimeException();
        }
    }

    public void writeBits(int[] bits) throws Exception {
        for (int bit : bits) {
            if (bit == 0 || bit == 1) {
                write(bit);
                continue;
            }
            throw new RuntimeException();
        }
    }

    public void close() throws Exception {
        if (next == 7) {
            return;
        }
        out.write(value);
    }
}