package io;

import java.io.*;


/**
 *  For stripping off the high bit of a byte
 *
 *  @version 1.0
 *  @author  Prof. David Bernstein, James Madison University
 */
public class SevenBitInputStream extends FilterInputStream
{
    /**
     * Explicit Value Constructor
     *
     * @param is   The underlying InputStream to filter
     */
    public SevenBitInputStream(InputStream is)
    {
	super(is);
    }


    /**
     * Reads the next byte of data from this input stream. 
     * The value byte is returned as an int in the range 0 to 127.
     *
     * @return The value of the byte (as an int)
     */
    public int read() throws IOException
    {
	int   i;

	i = in.read();     // in is a variable FilterInputStream
	return (i & 127);  // Bitwise AND
    }



    /**
     * Reads up to len bytes of data into an array of bytes. 
     *
     * @param b    The byte array into which the data are read
     * @param off  The start offset
     * @param len  The (maximum) number of bytes read
     * @return     The total number of bytes read
     */
    public int read(byte[] b, int off, int len) throws IOException
    {
	int    i, n;


	n = in.read(b, off, len);
	for (i=0; i < n; i++) b[i] = (byte)(b[i] & 127);

	return n;
    }

}