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EDIReader is a Java package for parsing business documents structured according to EDI standards. It supports the SAX and JAXP interfaces defined for XML, making it suitable for use in any XML-based system that allows the configuration of a custom SAX parser.

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/*
 * Copyright 2005-2015 by BerryWorks Software, LLC. All rights reserved.
 *
 * This file is part of EDIReader. You may obtain a license for its use directly from
 * BerryWorks Software, and you may also choose to use this software under the terms of the
 * GPL version 3. Other products in the EDIReader software suite are available only by licensing
 * with BerryWorks. Only those files bearing the GPL statement below are available under the GPL.
 *
 * EDIReader is free software: you can redistribute it and/or modify it under the terms of the
 * GNU General Public License as published by the Free Software Foundation, either version 3 of
 * the License, or (at your option) any later version.
 *
 * EDIReader is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
 * even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with EDIReader.  If not,
 * see .
 */

package com.berryworks.edireader.util.base64;

import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.CoderResult;

/**
 * Provides for base-64 decoding of Java Strings.
 */
public class StringBase64Decoder extends AbstractDecoder
{
  private final StringBuilder stringBuffer = new StringBuilder();
  private final ByteBuffer byteBuffer = ByteBuffer.allocate(100);

  @Override
  protected void emit(byte b)
  {
    if (!byteBuffer.hasRemaining())
    {
      feedStringBuffer();
      byteBuffer.clear();
    }
    byteBuffer.put(b);
  }

  private void feedStringBuffer()
  {
    byteBuffer.flip();
    stringBuffer.append(charset.decode(byteBuffer));
  }

  /**
   * Decodes the characters in a base-64 encoded String, producing the
   * original data as a String.
   *
   * @param encodedText
   * @return
   */
  public String decodeAsString(String encodedText)
  {
    CharBuffer charBuffer = CharBuffer.wrap(encodedText);

    // Allocate a modest sized non-direct ByteBuffer to receive the
    // bytes as they are encoded from the String
    ByteBuffer base64ByteBuffer = ByteBuffer.allocate(100);

    // Use the encoder repeatedly until all of the chars have been encoded as bytes
    // and presented as input for base 64 encoding.
    CharsetEncoder encoder = charset.newEncoder();
    while (true)
    {
      CoderResult coderResult = encoder.encode(charBuffer, base64ByteBuffer, true);
      if (coderResult.isError())
        throw new RuntimeException("Unrecoverable failure in Base64 encoding");
      base64ByteBuffer.flip();
      while (base64ByteBuffer.hasRemaining())
        consume(base64ByteBuffer.get());
      if (coderResult.isUnderflow()) break;
      base64ByteBuffer.clear();
    }
    endOfData();
    feedStringBuffer();

    return stringBuffer.toString();
  }
}