/*
 * Copyright (c) 2006, 2018 Oracle and/or its affiliates. All rights reserved.
 * 
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package com.sun.ts.lib.util;

import java.io.OutputStream;
import java.io.InputStream;
import java.io.PrintStream;
import java.io.IOException;

/**
 * This class implements a BASE64 Character encoder as specified in RFC1521.
 * This RFC is part of the MIME specification as published by the Internet
 * Engineering Task Force (IETF). Unlike some other encoding schemes there is
 * nothing in this encoding that indicates where a buffer starts or ends.
 *
 * This means that the encoded text will simply start with the first line of
 * encoded text and end with the last line of encoded text.
 *
 * @version 1.23, 11/17/05
 * @author Chuck McManis
 * @see CharacterEncoder
 * @see BASE64Decoder
 */

public class BASE64Encoder extends CharacterEncoder {

  /** this class encodes three bytes per atom. */
  protected int bytesPerAtom() {
    return (3);
  }

  /**
   * this class encodes 57 bytes per line. This results in a maximum of 57/3 * 4
   * or 76 characters per output line. Not counting the line termination.
   */
  protected int bytesPerLine() {
    return (57);
  }

  /** This array maps the characters to their 6 bit values */
  private final static char pem_array[] = {
      // 0 1 2 3 4 5 6 7
      'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', // 0
      'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', // 1
      'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', // 2
      'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', // 3
      'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', // 4
      'o', 'p', 'q', 'r', 's', 't', 'u', 'v', // 5
      'w', 'x', 'y', 'z', '0', '1', '2', '3', // 6
      '4', '5', '6', '7', '8', '9', '+', '/' // 7
  };

  /**
   * encodeAtom - Take three bytes of input and encode it as 4 printable
   * characters. Note that if the length in len is less than three is encodes
   * either one or two '=' signs to indicate padding characters.
   */
  protected void encodeAtom(OutputStream outStream, byte data[], int offset,
      int len) throws IOException {
    byte a, b, c;

    if (len == 1) {
      a = data[offset];
      b = 0;
      c = 0;
      outStream.write(pem_array[(a >>> 2) & 0x3F]);
      outStream.write(pem_array[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);
      outStream.write('=');
      outStream.write('=');
    } else if (len == 2) {
      a = data[offset];
      b = data[offset + 1];
      c = 0;
      outStream.write(pem_array[(a >>> 2) & 0x3F]);
      outStream.write(pem_array[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);
      outStream.write(pem_array[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)]);
      outStream.write('=');
    } else {
      a = data[offset];
      b = data[offset + 1];
      c = data[offset + 2];
      outStream.write(pem_array[(a >>> 2) & 0x3F]);
      outStream.write(pem_array[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);
      outStream.write(pem_array[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)]);
      outStream.write(pem_array[c & 0x3F]);
    }
  }
}
