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 * without modification, are permitted provided that the following
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 * from this software without specific prior written permission.
 *
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package examples.rmisocfac;

import java.io.*;

class XorInputStream extends FilterInputStream {

   /*
    * The byte being used to "decrypt" each byte of data.
    */
    private final byte pattern;

    /*
     * Constructs an input stream that uses the specified pattern
     * to "decrypt" each byte of data.
     */
    public XorInputStream(InputStream in, byte pattern) {
        super(in);
        this.pattern = pattern;
    }

    /*
     * Reads in a byte and xor's the byte with the pattern.
     * Returns the byte.
     */
    public int read() throws IOException {
        int b = in.read();
        //If not end of file or an error, truncate b to one byte
        if (b != -1)
          b = (b ^ pattern) & 0xFF;

        return b;
    }

    /*
     * Reads up to len bytes
     */
    public int read(byte b[], int off, int len) throws IOException {
        int numBytes = in.read(b, off, len);

        if (numBytes <= 0)
            return numBytes;

        for(int i = 0; i < numBytes; i++) {
            b[off + i] = (byte)((b[off + i] ^ pattern) & 0xFF);
        }

        return numBytes;
    }
}