001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.commons.codec.net;
019
020import java.io.ByteArrayOutputStream;
021import java.io.UnsupportedEncodingException;
022import java.nio.charset.Charset;
023import java.nio.charset.IllegalCharsetNameException;
024import java.nio.charset.StandardCharsets;
025import java.nio.charset.UnsupportedCharsetException;
026import java.util.BitSet;
027
028import org.apache.commons.codec.BinaryDecoder;
029import org.apache.commons.codec.BinaryEncoder;
030import org.apache.commons.codec.DecoderException;
031import org.apache.commons.codec.EncoderException;
032import org.apache.commons.codec.StringDecoder;
033import org.apache.commons.codec.StringEncoder;
034import org.apache.commons.codec.binary.StringUtils;
035
036/**
037 * Codec for the Quoted-Printable section of <a href="http://www.ietf.org/rfc/rfc1521.txt">RFC 1521</a>.
038 * <p>
039 * The Quoted-Printable encoding is intended to represent data that largely consists of octets that correspond to
040 * printable characters in the ASCII character set. It encodes the data in such a way that the resulting octets are
041 * unlikely to be modified by mail transport. If the data being encoded are mostly ASCII text, the encoded form of the
042 * data remains largely recognizable by humans. A body which is entirely ASCII may also be encoded in Quoted-Printable
043 * to ensure the integrity of the data should the message pass through a character- translating, and/or line-wrapping
044 * gateway.
045 * </p>
046 * <p>
047 * Note:
048 * </p>
049 * <p>
050 * Depending on the selected {@code strict} parameter, this class will implement a different set of rules of the
051 * quoted-printable spec:
052 * </p>
053 * <ul>
054 *   <li>{@code strict=false}: only rules #1 and #2 are implemented</li>
055 *   <li>{@code strict=true}: all rules #1 through #5 are implemented</li>
056 * </ul>
057 * <p>
058 * Originally, this class only supported the non-strict mode, but the codec in this partial form could already be used
059 * for certain applications that do not require quoted-printable line formatting (rules #3, #4, #5), for instance
060 * Q codec. The strict mode has been added in 1.10.
061 * </p>
062 * <p>
063 * This class is immutable and thread-safe.
064 * </p>
065 *
066 * @see <a href="http://www.ietf.org/rfc/rfc1521.txt">RFC 1521 MIME (Multipurpose Internet Mail Extensions) Part One:
067 *          Mechanisms for Specifying and Describing the Format of Internet Message Bodies </a>
068 *
069 * @since 1.3
070 */
071public class QuotedPrintableCodec implements BinaryEncoder, BinaryDecoder, StringEncoder, StringDecoder {
072    /**
073     * The default Charset used for string decoding and encoding.
074     */
075    private final Charset charset;
076
077    /**
078     * Indicates whether soft line breaks shall be used during encoding (rule #3-5).
079     */
080    private final boolean strict;
081
082    /**
083     * BitSet of printable characters as defined in RFC 1521.
084     */
085    private static final BitSet PRINTABLE_CHARS = new BitSet(256);
086
087    private static final byte ESCAPE_CHAR = '=';
088
089    private static final byte TAB = 9;
090
091    private static final byte SPACE = 32;
092
093    private static final byte CR = 13;
094
095    private static final byte LF = 10;
096
097    /**
098     * Safe line length for quoted printable encoded text.
099     */
100    private static final int SAFE_LENGTH = 73;
101
102    // Static initializer for printable chars collection
103    static {
104        // alpha characters
105        for (int i = 33; i <= 60; i++) {
106            PRINTABLE_CHARS.set(i);
107        }
108        for (int i = 62; i <= 126; i++) {
109            PRINTABLE_CHARS.set(i);
110        }
111        PRINTABLE_CHARS.set(TAB);
112        PRINTABLE_CHARS.set(SPACE);
113    }
114
115    /**
116     * Default constructor, assumes default Charset of {@link StandardCharsets#UTF_8}
117     */
118    public QuotedPrintableCodec() {
119        this(StandardCharsets.UTF_8, false);
120    }
121
122    /**
123     * Constructor which allows for the selection of the strict mode.
124     *
125     * @param strict
126     *            if {@code true}, soft line breaks will be used
127     * @since 1.10
128     */
129    public QuotedPrintableCodec(final boolean strict) {
130        this(StandardCharsets.UTF_8, strict);
131    }
132
133    /**
134     * Constructor which allows for the selection of a default Charset.
135     *
136     * @param charset
137     *            the default string Charset to use.
138     * @since 1.7
139     */
140    public QuotedPrintableCodec(final Charset charset) {
141        this(charset, false);
142    }
143
144    /**
145     * Constructor which allows for the selection of a default Charset and strict mode.
146     *
147     * @param charset
148     *            the default string Charset to use.
149     * @param strict
150     *            if {@code true}, soft line breaks will be used
151     * @since 1.10
152     */
153    public QuotedPrintableCodec(final Charset charset, final boolean strict) {
154        this.charset = charset;
155        this.strict = strict;
156    }
157
158    /**
159     * Constructor which allows for the selection of a default Charset.
160     *
161     * @param charsetName
162     *            the default string Charset to use.
163     * @throws UnsupportedCharsetException
164     *             If no support for the named Charset is available
165     *             in this instance of the Java virtual machine
166     * @throws IllegalArgumentException
167     *             If the given charsetName is null
168     * @throws IllegalCharsetNameException
169     *             If the given Charset name is illegal
170     *
171     * @since 1.7 throws UnsupportedCharsetException if the named Charset is unavailable
172     */
173    public QuotedPrintableCodec(final String charsetName)
174            throws IllegalCharsetNameException, IllegalArgumentException, UnsupportedCharsetException {
175        this(Charset.forName(charsetName), false);
176    }
177
178    /**
179     * Encodes byte into its quoted-printable representation.
180     *
181     * @param b
182     *            byte to encode
183     * @param buffer
184     *            the buffer to write to
185     * @return The number of bytes written to the {@code buffer}
186     */
187    private static final int encodeQuotedPrintable(final int b, final ByteArrayOutputStream buffer) {
188        buffer.write(ESCAPE_CHAR);
189        final char hex1 = Utils.hexDigit(b >> 4);
190        final char hex2 = Utils.hexDigit(b);
191        buffer.write(hex1);
192        buffer.write(hex2);
193        return 3;
194    }
195
196    /**
197     * Return the byte at position {@code index} of the byte array and
198     * make sure it is unsigned.
199     *
200     * @param index
201     *            position in the array
202     * @param bytes
203     *            the byte array
204     * @return the unsigned octet at position {@code index} from the array
205     */
206    private static int getUnsignedOctet(final int index, final byte[] bytes) {
207        int b = bytes[index];
208        if (b < 0) {
209            b = 256 + b;
210        }
211        return b;
212    }
213
214    /**
215     * Write a byte to the buffer.
216     *
217     * @param b
218     *            byte to write
219     * @param encode
220     *            indicates whether the octet shall be encoded
221     * @param buffer
222     *            the buffer to write to
223     * @return the number of bytes that have been written to the buffer
224     */
225    private static int encodeByte(final int b, final boolean encode,
226                                  final ByteArrayOutputStream buffer) {
227        if (encode) {
228            return encodeQuotedPrintable(b, buffer);
229        }
230        buffer.write(b);
231        return 1;
232    }
233
234    /**
235     * Checks whether the given byte is whitespace.
236     *
237     * @param b
238     *            byte to be checked
239     * @return {@code true} if the byte is either a space or tab character
240     */
241    private static boolean isWhitespace(final int b) {
242        return b == SPACE || b == TAB;
243    }
244
245    /**
246     * Encodes an array of bytes into an array of quoted-printable 7-bit characters. Unsafe characters are escaped.
247     * <p>
248     * This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
249     * RFC 1521 and is suitable for encoding binary data and unformatted text.
250     *
251     * @param printable
252     *            bitset of characters deemed quoted-printable
253     * @param bytes
254     *            array of bytes to be encoded
255     * @return array of bytes containing quoted-printable data
256     */
257    public static final byte[] encodeQuotedPrintable(final BitSet printable, final byte[] bytes) {
258        return encodeQuotedPrintable(printable, bytes, false);
259    }
260
261    /**
262     * Encodes an array of bytes into an array of quoted-printable 7-bit characters. Unsafe characters are escaped.
263     * <p>
264     * Depending on the selection of the {@code strict} parameter, this function either implements the full ruleset
265     * or only a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
266     * RFC 1521 and is suitable for encoding binary data and unformatted text.
267     *
268     * @param printable
269     *            bitset of characters deemed quoted-printable
270     * @param bytes
271     *            array of bytes to be encoded
272     * @param strict
273     *            if {@code true} the full ruleset is used, otherwise only rule #1 and rule #2
274     * @return array of bytes containing quoted-printable data
275     * @since 1.10
276     */
277    public static final byte[] encodeQuotedPrintable(BitSet printable, final byte[] bytes, final boolean strict) {
278        if (bytes == null) {
279            return null;
280        }
281        if (printable == null) {
282            printable = PRINTABLE_CHARS;
283        }
284        final ByteArrayOutputStream buffer = new ByteArrayOutputStream();
285
286        if (strict) {
287            int pos = 1;
288            // encode up to buffer.length - 3, the last three octets will be treated
289            // separately for simplification of note #3
290            for (int i = 0; i < bytes.length - 3; i++) {
291                final int b = getUnsignedOctet(i, bytes);
292                if (pos < SAFE_LENGTH) {
293                    // up to this length it is safe to add any byte, encoded or not
294                    pos += encodeByte(b, !printable.get(b), buffer);
295                } else {
296                    // rule #3: whitespace at the end of a line *must* be encoded
297                    encodeByte(b, !printable.get(b) || isWhitespace(b), buffer);
298
299                    // rule #5: soft line break
300                    buffer.write(ESCAPE_CHAR);
301                    buffer.write(CR);
302                    buffer.write(LF);
303                    pos = 1;
304                }
305            }
306
307            // rule #3: whitespace at the end of a line *must* be encoded
308            // if we would do a soft break line after this octet, encode whitespace
309            int b = getUnsignedOctet(bytes.length - 3, bytes);
310            boolean encode = !printable.get(b) || (isWhitespace(b) && pos > SAFE_LENGTH - 5);
311            pos += encodeByte(b, encode, buffer);
312
313            // note #3: '=' *must not* be the ultimate or penultimate character
314            // simplification: if < 6 bytes left, do a soft line break as we may need
315            //                 exactly 6 bytes space for the last 2 bytes
316            if (pos > SAFE_LENGTH - 2) {
317                buffer.write(ESCAPE_CHAR);
318                buffer.write(CR);
319                buffer.write(LF);
320            }
321            for (int i = bytes.length - 2; i < bytes.length; i++) {
322                b = getUnsignedOctet(i, bytes);
323                // rule #3: trailing whitespace shall be encoded
324                encode = !printable.get(b) || (i > bytes.length - 2 && isWhitespace(b));
325                encodeByte(b, encode, buffer);
326            }
327        } else {
328            for (final byte c : bytes) {
329                int b = c;
330                if (b < 0) {
331                    b = 256 + b;
332                }
333                if (printable.get(b)) {
334                    buffer.write(b);
335                } else {
336                    encodeQuotedPrintable(b, buffer);
337                }
338            }
339        }
340        return buffer.toByteArray();
341    }
342
343    /**
344     * Decodes an array quoted-printable characters into an array of original bytes. Escaped characters are converted
345     * back to their original representation.
346     * <p>
347     * This function fully implements the quoted-printable encoding specification (rule #1 through rule #5) as
348     * defined in RFC 1521.
349     *
350     * @param bytes
351     *            array of quoted-printable characters
352     * @return array of original bytes
353     * @throws DecoderException
354     *             Thrown if quoted-printable decoding is unsuccessful
355     */
356    public static final byte[] decodeQuotedPrintable(final byte[] bytes) throws DecoderException {
357        if (bytes == null) {
358            return null;
359        }
360        final ByteArrayOutputStream buffer = new ByteArrayOutputStream();
361        for (int i = 0; i < bytes.length; i++) {
362            final int b = bytes[i];
363            if (b == ESCAPE_CHAR) {
364                try {
365                    // if the next octet is a CR we have found a soft line break
366                    if (bytes[++i] == CR) {
367                        continue;
368                    }
369                    final int u = Utils.digit16(bytes[i]);
370                    final int l = Utils.digit16(bytes[++i]);
371                    buffer.write((char) ((u << 4) + l));
372                } catch (final ArrayIndexOutOfBoundsException e) {
373                    throw new DecoderException("Invalid quoted-printable encoding", e);
374                }
375            } else if (b != CR && b != LF) {
376                // every other octet is appended except for CR & LF
377                buffer.write(b);
378            }
379        }
380        return buffer.toByteArray();
381    }
382
383    /**
384     * Encodes an array of bytes into an array of quoted-printable 7-bit characters. Unsafe characters are escaped.
385     * <p>
386     * Depending on the selection of the {@code strict} parameter, this function either implements the full ruleset
387     * or only a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
388     * RFC 1521 and is suitable for encoding binary data and unformatted text.
389     *
390     * @param bytes
391     *            array of bytes to be encoded
392     * @return array of bytes containing quoted-printable data
393     */
394    @Override
395    public byte[] encode(final byte[] bytes) {
396        return encodeQuotedPrintable(PRINTABLE_CHARS, bytes, strict);
397    }
398
399    /**
400     * Decodes an array of quoted-printable characters into an array of original bytes. Escaped characters are converted
401     * back to their original representation.
402     * <p>
403     * This function fully implements the quoted-printable encoding specification (rule #1 through rule #5) as
404     * defined in RFC 1521.
405     *
406     * @param bytes
407     *            array of quoted-printable characters
408     * @return array of original bytes
409     * @throws DecoderException
410     *             Thrown if quoted-printable decoding is unsuccessful
411     */
412    @Override
413    public byte[] decode(final byte[] bytes) throws DecoderException {
414        return decodeQuotedPrintable(bytes);
415    }
416
417    /**
418     * Encodes a string into its quoted-printable form using the default string Charset. Unsafe characters are escaped.
419     * <p>
420     * Depending on the selection of the {@code strict} parameter, this function either implements the full ruleset
421     * or only a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
422     * RFC 1521 and is suitable for encoding binary data and unformatted text.
423     *
424     * @param sourceStr
425     *            string to convert to quoted-printable form
426     * @return quoted-printable string
427     * @throws EncoderException
428     *             Thrown if quoted-printable encoding is unsuccessful
429     *
430     * @see #getCharset()
431     */
432    @Override
433    public String encode(final String sourceStr) throws EncoderException {
434        return this.encode(sourceStr, getCharset());
435    }
436
437    /**
438     * Decodes a quoted-printable string into its original form using the specified string Charset. Escaped characters
439     * are converted back to their original representation.
440     *
441     * @param sourceStr
442     *            quoted-printable string to convert into its original form
443     * @param sourceCharset
444     *            the original string Charset
445     * @return original string
446     * @throws DecoderException
447     *             Thrown if quoted-printable decoding is unsuccessful
448     * @since 1.7
449     */
450    public String decode(final String sourceStr, final Charset sourceCharset) throws DecoderException {
451        if (sourceStr == null) {
452            return null;
453        }
454        return new String(this.decode(StringUtils.getBytesUsAscii(sourceStr)), sourceCharset);
455    }
456
457    /**
458     * Decodes a quoted-printable string into its original form using the specified string Charset. Escaped characters
459     * are converted back to their original representation.
460     *
461     * @param sourceStr
462     *            quoted-printable string to convert into its original form
463     * @param sourceCharset
464     *            the original string Charset
465     * @return original string
466     * @throws DecoderException
467     *             Thrown if quoted-printable decoding is unsuccessful
468     * @throws UnsupportedEncodingException
469     *             Thrown if Charset is not supported
470     */
471    public String decode(final String sourceStr, final String sourceCharset)
472            throws DecoderException, UnsupportedEncodingException {
473        if (sourceStr == null) {
474            return null;
475        }
476        return new String(decode(StringUtils.getBytesUsAscii(sourceStr)), sourceCharset);
477    }
478
479    /**
480     * Decodes a quoted-printable string into its original form using the default string Charset. Escaped characters are
481     * converted back to their original representation.
482     *
483     * @param sourceStr
484     *            quoted-printable string to convert into its original form
485     * @return original string
486     * @throws DecoderException
487     *             Thrown if quoted-printable decoding is unsuccessful. Thrown if Charset is not supported.
488     * @see #getCharset()
489     */
490    @Override
491    public String decode(final String sourceStr) throws DecoderException {
492        return this.decode(sourceStr, this.getCharset());
493    }
494
495    /**
496     * Encodes an object into its quoted-printable safe form. Unsafe characters are escaped.
497     *
498     * @param obj
499     *            string to convert to a quoted-printable form
500     * @return quoted-printable object
501     * @throws EncoderException
502     *             Thrown if quoted-printable encoding is not applicable to objects of this type or if encoding is
503     *             unsuccessful
504     */
505    @Override
506    public Object encode(final Object obj) throws EncoderException {
507        if (obj == null) {
508            return null;
509        } else if (obj instanceof byte[]) {
510            return encode((byte[]) obj);
511        } else if (obj instanceof String) {
512            return encode((String) obj);
513        } else {
514            throw new EncoderException("Objects of type " +
515                  obj.getClass().getName() +
516                  " cannot be quoted-printable encoded");
517        }
518    }
519
520    /**
521     * Decodes a quoted-printable object into its original form. Escaped characters are converted back to their original
522     * representation.
523     *
524     * @param obj
525     *            quoted-printable object to convert into its original form
526     * @return original object
527     * @throws DecoderException
528     *             Thrown if the argument is not a {@code String} or {@code byte[]}. Thrown if a failure
529     *             condition is encountered during the decode process.
530     */
531    @Override
532    public Object decode(final Object obj) throws DecoderException {
533        if (obj == null) {
534            return null;
535        } else if (obj instanceof byte[]) {
536            return decode((byte[]) obj);
537        } else if (obj instanceof String) {
538            return decode((String) obj);
539        } else {
540            throw new DecoderException("Objects of type " +
541                  obj.getClass().getName() +
542                  " cannot be quoted-printable decoded");
543        }
544    }
545
546    /**
547     * Gets the default Charset name used for string decoding and encoding.
548     *
549     * @return the default Charset name
550     * @since 1.7
551     */
552    public Charset getCharset() {
553        return this.charset;
554    }
555
556    /**
557     * Gets the default Charset name used for string decoding and encoding.
558     *
559     * @return the default Charset name
560     */
561    public String getDefaultCharset() {
562        return this.charset.name();
563    }
564
565    /**
566     * Encodes a string into its quoted-printable form using the specified Charset. Unsafe characters are escaped.
567     * <p>
568     * Depending on the selection of the {@code strict} parameter, this function either implements the full ruleset
569     * or only a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
570     * RFC 1521 and is suitable for encoding binary data and unformatted text.
571     *
572     * @param sourceStr
573     *            string to convert to quoted-printable form
574     * @param sourceCharset
575     *            the Charset for sourceStr
576     * @return quoted-printable string
577     * @since 1.7
578     */
579    public String encode(final String sourceStr, final Charset sourceCharset) {
580        if (sourceStr == null) {
581            return null;
582        }
583        return StringUtils.newStringUsAscii(this.encode(sourceStr.getBytes(sourceCharset)));
584    }
585
586    /**
587     * Encodes a string into its quoted-printable form using the specified Charset. Unsafe characters are escaped.
588     * <p>
589     * Depending on the selection of the {@code strict} parameter, this function either implements the full ruleset
590     * or only a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
591     * RFC 1521 and is suitable for encoding binary data and unformatted text.
592     *
593     * @param sourceStr
594     *            string to convert to quoted-printable form
595     * @param sourceCharset
596     *            the Charset for sourceStr
597     * @return quoted-printable string
598     * @throws UnsupportedEncodingException
599     *             Thrown if the Charset is not supported
600     */
601    public String encode(final String sourceStr, final String sourceCharset) throws UnsupportedEncodingException {
602        if (sourceStr == null) {
603            return null;
604        }
605        return StringUtils.newStringUsAscii(encode(sourceStr.getBytes(sourceCharset)));
606    }
607}