content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   * 
   *      http://www.apache.org/licenses/LICENSE-2.0
   * 
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.apache.commons.codec.net;
  
  import java.io.UnsupportedEncodingException;
  import java.util.BitSet;
  
  import org.apache.commons.codec.DecoderException;
  import org.apache.commons.codec.EncoderException;
  import org.apache.commons.codec.CharEncoding;
  import org.apache.commons.codec.StringDecoder;
  import org.apache.commons.codec.StringEncoder;
  
  /**
   * <p>
   * Similar to the Quoted-Printable content-transfer-encoding defined in <a
   * href="http://www.ietf.org/rfc/rfc1521.txt">RFC 1521</a> and designed to allow text containing mostly ASCII
   * characters to be decipherable on an ASCII terminal without decoding.
   * </p>
   * 
   * <p>
   * <a href="http://www.ietf.org/rfc/rfc1522.txt">RFC 1522</a> describes techniques to allow the encoding of non-ASCII
   * text in various portions of a RFC 822 [2] message header, in a manner which is unlikely to confuse existing message
   * handling software.
   * </p>
   * 
   * @see <a href="http://www.ietf.org/rfc/rfc1522.txt">MIME (Multipurpose Internet Mail Extensions) Part Two: Message
   *          Header Extensions for Non-ASCII Text</a>
   * 
   * @author Apache Software Foundation
   * @since 1.3
   * @version $Id: QCodec.java 797857 2009-07-25 23:43:33Z ggregory $
   */
  public class QCodec extends RFC1522Codec implements StringEncoder, StringDecoder {
      /**
       * The default charset used for string decoding and encoding.
       */
      private final String charset;
  
      /**
       * BitSet of printable characters as defined in RFC 1522.
       */
      private static final BitSet PRINTABLE_CHARS = new BitSet(256);
      // Static initializer for printable chars collection
      static {
          // alpha characters
          PRINTABLE_CHARS.set(' ');
          PRINTABLE_CHARS.set('!');
          PRINTABLE_CHARS.set('"');
          PRINTABLE_CHARS.set('#');
          PRINTABLE_CHARS.set('$');
          PRINTABLE_CHARS.set('%');
          PRINTABLE_CHARS.set('&');
          PRINTABLE_CHARS.set('\'');
          PRINTABLE_CHARS.set('(');
          PRINTABLE_CHARS.set(')');
          PRINTABLE_CHARS.set('*');
          PRINTABLE_CHARS.set('+');
          PRINTABLE_CHARS.set(',');
          PRINTABLE_CHARS.set('-');
          PRINTABLE_CHARS.set('.');
          PRINTABLE_CHARS.set('/');
          for (int i = '0'; i <= '9'; i++) {
              PRINTABLE_CHARS.set(i);
          }
          PRINTABLE_CHARS.set(':');
          PRINTABLE_CHARS.set(';');
          PRINTABLE_CHARS.set('<');
          PRINTABLE_CHARS.set('>');
          PRINTABLE_CHARS.set('@');
          for (int i = 'A'; i <= 'Z'; i++) {
              PRINTABLE_CHARS.set(i);
          }
          PRINTABLE_CHARS.set('[');
          PRINTABLE_CHARS.set('\\');
          PRINTABLE_CHARS.set(']');
          PRINTABLE_CHARS.set('^');
          PRINTABLE_CHARS.set('`');
          for (int i = 'a'; i <= 'z'; i++) {
              PRINTABLE_CHARS.set(i);
          }
          PRINTABLE_CHARS.set('{');
          PRINTABLE_CHARS.set('|');
          PRINTABLE_CHARS.set('}');
          PRINTABLE_CHARS.set('~');
      }
  
      private static final byte BLANK = 32;
  
      private static final byte UNDERSCORE = 95;
  
      private boolean encodeBlanks = false;
  
      /**
       * Default constructor.
       */
      public QCodec() {
          this(CharEncoding.UTF_8);
      }
  
      /**
       * Constructor which allows for the selection of a default charset
       * 
       * @param charset
       *                  the default string charset to use.
       * 
       * @see <a href="http://java.sun.com/j2se/1.4.2/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
       */
      public QCodec(final String charset) {
          super();
          this.charset = charset;
      }
  
      protected String getEncoding() {
          return "Q";
      }
  
      protected byte[] doEncoding(byte[] bytes) {
          if (bytes == null) {
              return null;
          }
          byte[] data = QuotedPrintableCodec.encodeQuotedPrintable(PRINTABLE_CHARS, bytes);
          if (this.encodeBlanks) {
              for (int i = 0; i < data.length; i++) {
                  if (data[i] == BLANK) {
                      data[i] = UNDERSCORE;
                  }
              }
          }
          return data;
      }
  
      protected byte[] doDecoding(byte[] bytes) throws DecoderException {
          if (bytes == null) {
              return null;
          }
          boolean hasUnderscores = false;
          for (int i = 0; i < bytes.length; i++) {
              if (bytes[i] == UNDERSCORE) {
                  hasUnderscores = true;
                  break;
              }
          }
          if (hasUnderscores) {
              byte[] tmp = new byte[bytes.length];
              for (int i = 0; i < bytes.length; i++) {
                  byte b = bytes[i];
                  if (b != UNDERSCORE) {
                      tmp[i] = b;
                  } else {
                      tmp[i] = BLANK;
                  }
              }
              return QuotedPrintableCodec.decodeQuotedPrintable(tmp);
          } 
          return QuotedPrintableCodec.decodeQuotedPrintable(bytes);       
      }
  
      /**
       * Encodes a string into its quoted-printable form using the specified charset. Unsafe characters are escaped.
       * 
       * @param pString
       *                  string to convert to quoted-printable form
       * @param charset
       *                  the charset for pString
       * @return quoted-printable string
       * 
       * @throws EncoderException
       *                  thrown if a failure condition is encountered during the encoding process.
       */
      public String encode(final String pString, final String charset) throws EncoderException {
          if (pString == null) {
              return null;
          }
          try {
              return encodeText(pString, charset);
          } catch (UnsupportedEncodingException e) {
              throw new EncoderException(e.getMessage(), e);
          }
      }
  
      /**
       * Encodes a string into its quoted-printable form using the default charset. Unsafe characters are escaped.
       * 
       * @param pString
       *                  string to convert to quoted-printable form
       * @return quoted-printable string
       * 
       * @throws EncoderException
       *                  thrown if a failure condition is encountered during the encoding process.
       */
      public String encode(String pString) throws EncoderException {
          if (pString == null) {
              return null;
          }
          return encode(pString, getDefaultCharset());
      }
  
      /**
       * Decodes a quoted-printable string into its original form. Escaped characters are converted back to their original
       * representation.
       * 
       * @param pString
       *                  quoted-printable string to convert into its original form
       * 
       * @return original string
       * 
       * @throws DecoderException
       *                  A decoder exception is thrown if a failure condition is encountered during the decode process.
       */
      public String decode(String pString) throws DecoderException {
          if (pString == null) {
              return null;
          }
          try {
              return decodeText(pString);
          } catch (UnsupportedEncodingException e) {
              throw new DecoderException(e.getMessage(), e);
          }
      }
  
      /**
       * Encodes an object into its quoted-printable form using the default charset. Unsafe characters are escaped.
       * 
       * @param pObject
       *                  object to convert to quoted-printable form
       * @return quoted-printable object
       * 
       * @throws EncoderException
       *                  thrown if a failure condition is encountered during the encoding process.
       */
      public Object encode(Object pObject) throws EncoderException {
          if (pObject == null) {
              return null;
          } else if (pObject instanceof String) {
              return encode((String) pObject);
          } else {
              throw new EncoderException("Objects of type " + 
                    pObject.getClass().getName() + 
                    " cannot be encoded using Q codec");
          }
      }
  
      /**
       * Decodes a quoted-printable object into its original form. Escaped characters are converted back to their original
       * representation.
       * 
       * @param pObject
       *                  quoted-printable object to convert into its original form
       * 
       * @return original object
       * 
       * @throws DecoderException
       *                  Thrown if the argument is not a <code>String</code>. Thrown if a failure condition is
       *                  encountered during the decode process.
       */
      public Object decode(Object pObject) throws DecoderException {
          if (pObject == null) {
              return null;
          } else if (pObject instanceof String) {
              return decode((String) pObject);
          } else {
              throw new DecoderException("Objects of type " + 
                    pObject.getClass().getName() + 
                    " cannot be decoded using Q codec");
          }
      }
  
      /**
       * The default charset used for string decoding and encoding.
       * 
       * @return the default string charset.
       */
      public String getDefaultCharset() {
          return this.charset;
      }
  
      /**
       * Tests if optional tranformation of SPACE characters is to be used
       * 
       * @return <code>true</code> if SPACE characters are to be transformed, <code>false</code> otherwise
       */
      public boolean isEncodeBlanks() {
          return this.encodeBlanks;
      }
  
      /**
       * Defines whether optional tranformation of SPACE characters is to be used
       * 
       * @param b
       *                  <code>true</code> if SPACE characters are to be transformed, <code>false</code> otherwise
       */
      public void setEncodeBlanks(boolean b) {
          this.encodeBlanks = b;
      }
  }
  