001 /****************************************************************
002 * Licensed to the Apache Software Foundation (ASF) under one *
003 * or more contributor license agreements. See the NOTICE file *
004 * distributed with this work for additional information *
005 * regarding copyright ownership. The ASF licenses this file *
006 * to you under the Apache License, Version 2.0 (the *
007 * "License"); you may not use this file except in compliance *
008 * with the License. You may obtain a copy of the License at *
009 * *
010 * http://www.apache.org/licenses/LICENSE-2.0 *
011 * *
012 * Unless required by applicable law or agreed to in writing, *
013 * software distributed under the License is distributed on an *
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY *
015 * KIND, either express or implied. See the License for the *
016 * specific language governing permissions and limitations *
017 * under the License. *
018 ****************************************************************/
019
020 package org.apache.james.mime4j.codec;
021
022 import java.nio.ByteBuffer;
023 import java.nio.charset.Charset;
024 import java.util.BitSet;
025 import java.util.Locale;
026
027 import org.apache.james.mime4j.util.CharsetUtil;
028
029 /**
030 * Static methods for encoding header field values. This includes encoded-words
031 * as defined in <a href='http://www.faqs.org/rfcs/rfc2047.html'>RFC 2047</a>
032 * or display-names of an e-mail address, for example.
033 */
034 public class EncoderUtil {
035 private static final byte[] BASE64_TABLE = Base64OutputStream.BASE64_TABLE;
036 private static final char BASE64_PAD = '=';
037
038 private static final BitSet Q_REGULAR_CHARS = initChars("=_?");
039
040 private static final BitSet Q_RESTRICTED_CHARS = initChars("=_?\"#$%&'(),.:;<>@[\\]^`{|}~");
041
042 private static final int MAX_USED_CHARACTERS = 50;
043
044 private static final String ENC_WORD_PREFIX = "=?";
045 private static final String ENC_WORD_SUFFIX = "?=";
046
047 private static final int ENCODED_WORD_MAX_LENGTH = 75; // RFC 2047
048
049 private static final BitSet TOKEN_CHARS = initChars("()<>@,;:\\\"/[]?=");
050
051 private static final BitSet ATEXT_CHARS = initChars("()<>@.,;:\\\"[]");
052
053 private static BitSet initChars(String specials) {
054 BitSet bs = new BitSet(128);
055 for (char ch = 33; ch < 127; ch++) {
056 if (specials.indexOf(ch) == -1) {
057 bs.set(ch);
058 }
059 }
060 return bs;
061 }
062
063 /**
064 * Selects one of the two encodings specified in RFC 2047.
065 */
066 public enum Encoding {
067 /** The B encoding (identical to base64 defined in RFC 2045). */
068 B,
069 /** The Q encoding (similar to quoted-printable defined in RFC 2045). */
070 Q
071 }
072
073 /**
074 * Indicates the intended usage of an encoded word.
075 */
076 public enum Usage {
077 /**
078 * Encoded word is used to replace a 'text' token in any Subject or
079 * Comments header field.
080 */
081 TEXT_TOKEN,
082 /**
083 * Encoded word is used to replace a 'word' entity within a 'phrase',
084 * for example, one that precedes an address in a From, To, or Cc
085 * header.
086 */
087 WORD_ENTITY
088 }
089
090 private EncoderUtil() {
091 }
092
093 /**
094 * Encodes the display-name portion of an address. See <a
095 * href='http://www.faqs.org/rfcs/rfc5322.html'>RFC 5322</a> section 3.4
096 * and <a href='http://www.faqs.org/rfcs/rfc2047.html'>RFC 2047</a> section
097 * 5.3. The specified string should not be folded.
098 *
099 * @param displayName
100 * display-name to encode.
101 * @return encoded display-name.
102 */
103 public static String encodeAddressDisplayName(String displayName) {
104 // display-name = phrase
105 // phrase = 1*( encoded-word / word )
106 // word = atom / quoted-string
107 // atom = [CFWS] 1*atext [CFWS]
108 // CFWS = comment or folding white space
109
110 if (isAtomPhrase(displayName)) {
111 return displayName;
112 } else if (hasToBeEncoded(displayName, 0)) {
113 return encodeEncodedWord(displayName, Usage.WORD_ENTITY);
114 } else {
115 return quote(displayName);
116 }
117 }
118
119 /**
120 * Encodes the local part of an address specification as described in RFC
121 * 5322 section 3.4.1. Leading and trailing CFWS should have been removed
122 * before calling this method. The specified string should not contain any
123 * illegal (control or non-ASCII) characters.
124 *
125 * @param localPart
126 * the local part to encode
127 * @return the encoded local part.
128 */
129 public static String encodeAddressLocalPart(String localPart) {
130 // local-part = dot-atom / quoted-string
131 // dot-atom = [CFWS] dot-atom-text [CFWS]
132 // CFWS = comment or folding white space
133
134 if (isDotAtomText(localPart)) {
135 return localPart;
136 } else {
137 return quote(localPart);
138 }
139 }
140
141 /**
142 * Encodes the specified strings into a header parameter as described in RFC
143 * 2045 section 5.1 and RFC 2183 section 2. The specified strings should not
144 * contain any illegal (control or non-ASCII) characters.
145 *
146 * @param name
147 * parameter name.
148 * @param value
149 * parameter value.
150 * @return encoded result.
151 */
152 public static String encodeHeaderParameter(String name, String value) {
153 name = name.toLowerCase(Locale.US);
154
155 // value := token / quoted-string
156 if (isToken(value)) {
157 return name + "=" + value;
158 } else {
159 return name + "=" + quote(value);
160 }
161 }
162
163 /**
164 * Shortcut method that encodes the specified text into an encoded-word if
165 * the text has to be encoded.
166 *
167 * @param text
168 * text to encode.
169 * @param usage
170 * whether the encoded-word is to be used to replace a text token
171 * or a word entity (see RFC 822).
172 * @param usedCharacters
173 * number of characters already used up (<code>0 <= usedCharacters <= 50</code>).
174 * @return the specified text if encoding is not necessary or an encoded
175 * word or a sequence of encoded words otherwise.
176 */
177 public static String encodeIfNecessary(String text, Usage usage,
178 int usedCharacters) {
179 if (hasToBeEncoded(text, usedCharacters))
180 return encodeEncodedWord(text, usage, usedCharacters);
181 else
182 return text;
183 }
184
185 /**
186 * Determines if the specified string has to encoded into an encoded-word.
187 * Returns <code>true</code> if the text contains characters that don't
188 * fall into the printable ASCII character set or if the text contains a
189 * 'word' (sequence of non-whitespace characters) longer than 77 characters
190 * (including characters already used up in the line).
191 *
192 * @param text
193 * text to analyze.
194 * @param usedCharacters
195 * number of characters already used up (<code>0 <= usedCharacters <= 50</code>).
196 * @return <code>true</code> if the specified text has to be encoded into
197 * an encoded-word, <code>false</code> otherwise.
198 */
199 public static boolean hasToBeEncoded(String text, int usedCharacters) {
200 if (text == null)
201 throw new IllegalArgumentException();
202 if (usedCharacters < 0 || usedCharacters > MAX_USED_CHARACTERS)
203 throw new IllegalArgumentException();
204
205 int nonWhiteSpaceCount = usedCharacters;
206
207 for (int idx = 0; idx < text.length(); idx++) {
208 char ch = text.charAt(idx);
209 if (ch == '\t' || ch == ' ') {
210 nonWhiteSpaceCount = 0;
211 } else {
212 nonWhiteSpaceCount++;
213 if (nonWhiteSpaceCount > 77) {
214 // Line cannot be folded into multiple lines with no more
215 // than 78 characters each. Encoding as encoded-words makes
216 // that possible. One character has to be reserved for
217 // folding white space; that leaves 77 characters.
218 return true;
219 }
220
221 if (ch < 32 || ch >= 127) {
222 // non-printable ascii character has to be encoded
223 return true;
224 }
225 }
226 }
227
228 return false;
229 }
230
231 /**
232 * Encodes the specified text into an encoded word or a sequence of encoded
233 * words separated by space. The text is separated into a sequence of
234 * encoded words if it does not fit in a single one.
235 * <p>
236 * The charset to encode the specified text into a byte array and the
237 * encoding to use for the encoded-word are detected automatically.
238 * <p>
239 * This method assumes that zero characters have already been used up in the
240 * current line.
241 *
242 * @param text
243 * text to encode.
244 * @param usage
245 * whether the encoded-word is to be used to replace a text token
246 * or a word entity (see RFC 822).
247 * @return the encoded word (or sequence of encoded words if the given text
248 * does not fit in a single encoded word).
249 * @see #hasToBeEncoded(String, int)
250 */
251 public static String encodeEncodedWord(String text, Usage usage) {
252 return encodeEncodedWord(text, usage, 0, null, null);
253 }
254
255 /**
256 * Encodes the specified text into an encoded word or a sequence of encoded
257 * words separated by space. The text is separated into a sequence of
258 * encoded words if it does not fit in a single one.
259 * <p>
260 * The charset to encode the specified text into a byte array and the
261 * encoding to use for the encoded-word are detected automatically.
262 *
263 * @param text
264 * text to encode.
265 * @param usage
266 * whether the encoded-word is to be used to replace a text token
267 * or a word entity (see RFC 822).
268 * @param usedCharacters
269 * number of characters already used up (<code>0 <= usedCharacters <= 50</code>).
270 * @return the encoded word (or sequence of encoded words if the given text
271 * does not fit in a single encoded word).
272 * @see #hasToBeEncoded(String, int)
273 */
274 public static String encodeEncodedWord(String text, Usage usage,
275 int usedCharacters) {
276 return encodeEncodedWord(text, usage, usedCharacters, null, null);
277 }
278
279 /**
280 * Encodes the specified text into an encoded word or a sequence of encoded
281 * words separated by space. The text is separated into a sequence of
282 * encoded words if it does not fit in a single one.
283 *
284 * @param text
285 * text to encode.
286 * @param usage
287 * whether the encoded-word is to be used to replace a text token
288 * or a word entity (see RFC 822).
289 * @param usedCharacters
290 * number of characters already used up (<code>0 <= usedCharacters <= 50</code>).
291 * @param charset
292 * the Java charset that should be used to encode the specified
293 * string into a byte array. A suitable charset is detected
294 * automatically if this parameter is <code>null</code>.
295 * @param encoding
296 * the encoding to use for the encoded-word (either B or Q). A
297 * suitable encoding is automatically chosen if this parameter is
298 * <code>null</code>.
299 * @return the encoded word (or sequence of encoded words if the given text
300 * does not fit in a single encoded word).
301 * @see #hasToBeEncoded(String, int)
302 */
303 public static String encodeEncodedWord(String text, Usage usage,
304 int usedCharacters, Charset charset, Encoding encoding) {
305 if (text == null)
306 throw new IllegalArgumentException();
307 if (usedCharacters < 0 || usedCharacters > MAX_USED_CHARACTERS)
308 throw new IllegalArgumentException();
309
310 if (charset == null)
311 charset = determineCharset(text);
312
313 byte[] bytes = encode(text, charset);
314
315 if (encoding == null)
316 encoding = determineEncoding(bytes, usage);
317
318 if (encoding == Encoding.B) {
319 String prefix = ENC_WORD_PREFIX + charset.name() + "?B?";
320 return encodeB(prefix, text, usedCharacters, charset, bytes);
321 } else {
322 String prefix = ENC_WORD_PREFIX + charset.name() + "?Q?";
323 return encodeQ(prefix, text, usage, usedCharacters, charset, bytes);
324 }
325 }
326
327 /**
328 * Encodes the specified byte array using the B encoding defined in RFC
329 * 2047.
330 *
331 * @param bytes
332 * byte array to encode.
333 * @return encoded string.
334 */
335 public static String encodeB(byte[] bytes) {
336 StringBuilder sb = new StringBuilder();
337
338 int idx = 0;
339 final int end = bytes.length;
340 for (; idx < end - 2; idx += 3) {
341 int data = (bytes[idx] & 0xff) << 16 | (bytes[idx + 1] & 0xff) << 8
342 | bytes[idx + 2] & 0xff;
343 sb.append((char) BASE64_TABLE[data >> 18 & 0x3f]);
344 sb.append((char) BASE64_TABLE[data >> 12 & 0x3f]);
345 sb.append((char) BASE64_TABLE[data >> 6 & 0x3f]);
346 sb.append((char) BASE64_TABLE[data & 0x3f]);
347 }
348
349 if (idx == end - 2) {
350 int data = (bytes[idx] & 0xff) << 16 | (bytes[idx + 1] & 0xff) << 8;
351 sb.append((char) BASE64_TABLE[data >> 18 & 0x3f]);
352 sb.append((char) BASE64_TABLE[data >> 12 & 0x3f]);
353 sb.append((char) BASE64_TABLE[data >> 6 & 0x3f]);
354 sb.append(BASE64_PAD);
355
356 } else if (idx == end - 1) {
357 int data = (bytes[idx] & 0xff) << 16;
358 sb.append((char) BASE64_TABLE[data >> 18 & 0x3f]);
359 sb.append((char) BASE64_TABLE[data >> 12 & 0x3f]);
360 sb.append(BASE64_PAD);
361 sb.append(BASE64_PAD);
362 }
363
364 return sb.toString();
365 }
366
367 /**
368 * Encodes the specified byte array using the Q encoding defined in RFC
369 * 2047.
370 *
371 * @param bytes
372 * byte array to encode.
373 * @param usage
374 * whether the encoded-word is to be used to replace a text token
375 * or a word entity (see RFC 822).
376 * @return encoded string.
377 */
378 public static String encodeQ(byte[] bytes, Usage usage) {
379 BitSet qChars = usage == Usage.TEXT_TOKEN ? Q_REGULAR_CHARS
380 : Q_RESTRICTED_CHARS;
381
382 StringBuilder sb = new StringBuilder();
383
384 final int end = bytes.length;
385 for (int idx = 0; idx < end; idx++) {
386 int v = bytes[idx] & 0xff;
387 if (v == 32) {
388 sb.append('_');
389 } else if (!qChars.get(v)) {
390 sb.append('=');
391 sb.append(hexDigit(v >>> 4));
392 sb.append(hexDigit(v & 0xf));
393 } else {
394 sb.append((char) v);
395 }
396 }
397
398 return sb.toString();
399 }
400
401 /**
402 * Tests whether the specified string is a token as defined in RFC 2045
403 * section 5.1.
404 *
405 * @param str
406 * string to test.
407 * @return <code>true</code> if the specified string is a RFC 2045 token,
408 * <code>false</code> otherwise.
409 */
410 public static boolean isToken(String str) {
411 // token := 1*<any (US-ASCII) CHAR except SPACE, CTLs, or tspecials>
412 // tspecials := "(" / ")" / "<" / ">" / "@" / "," / ";" / ":" / "\" /
413 // <"> / "/" / "[" / "]" / "?" / "="
414 // CTL := 0.- 31., 127.
415
416 final int length = str.length();
417 if (length == 0)
418 return false;
419
420 for (int idx = 0; idx < length; idx++) {
421 char ch = str.charAt(idx);
422 if (!TOKEN_CHARS.get(ch))
423 return false;
424 }
425
426 return true;
427 }
428
429 private static boolean isAtomPhrase(String str) {
430 // atom = [CFWS] 1*atext [CFWS]
431
432 boolean containsAText = false;
433
434 final int length = str.length();
435 for (int idx = 0; idx < length; idx++) {
436 char ch = str.charAt(idx);
437 if (ATEXT_CHARS.get(ch)) {
438 containsAText = true;
439 } else if (!CharsetUtil.isWhitespace(ch)) {
440 return false;
441 }
442 }
443
444 return containsAText;
445 }
446
447 // RFC 5322 section 3.2.3
448 private static boolean isDotAtomText(String str) {
449 // dot-atom-text = 1*atext *("." 1*atext)
450 // atext = ALPHA / DIGIT / "!" / "#" / "$" / "%" / "&" / "'" / "*" /
451 // "+" / "-" / "/" / "=" / "?" / "^" / "_" / "`" / "{" / "|" / "}" / "~"
452
453 char prev = '.';
454
455 final int length = str.length();
456 if (length == 0)
457 return false;
458
459 for (int idx = 0; idx < length; idx++) {
460 char ch = str.charAt(idx);
461
462 if (ch == '.') {
463 if (prev == '.' || idx == length - 1)
464 return false;
465 } else {
466 if (!ATEXT_CHARS.get(ch))
467 return false;
468 }
469
470 prev = ch;
471 }
472
473 return true;
474 }
475
476 // RFC 5322 section 3.2.4
477 private static String quote(String str) {
478 // quoted-string = [CFWS] DQUOTE *([FWS] qcontent) [FWS] DQUOTE [CFWS]
479 // qcontent = qtext / quoted-pair
480 // qtext = %d33 / %d35-91 / %d93-126
481 // quoted-pair = ("\" (VCHAR / WSP))
482 // VCHAR = %x21-7E
483 // DQUOTE = %x22
484
485 String escaped = str.replaceAll("[\\\\\"]", "\\\\$0");
486 return "\"" + escaped + "\"";
487 }
488
489 private static String encodeB(String prefix, String text,
490 int usedCharacters, Charset charset, byte[] bytes) {
491 int encodedLength = bEncodedLength(bytes);
492
493 int totalLength = prefix.length() + encodedLength
494 + ENC_WORD_SUFFIX.length();
495 if (totalLength <= ENCODED_WORD_MAX_LENGTH - usedCharacters) {
496 return prefix + encodeB(bytes) + ENC_WORD_SUFFIX;
497 } else {
498 String part1 = text.substring(0, text.length() / 2);
499 byte[] bytes1 = encode(part1, charset);
500 String word1 = encodeB(prefix, part1, usedCharacters, charset,
501 bytes1);
502
503 String part2 = text.substring(text.length() / 2);
504 byte[] bytes2 = encode(part2, charset);
505 String word2 = encodeB(prefix, part2, 0, charset, bytes2);
506
507 return word1 + " " + word2;
508 }
509 }
510
511 private static int bEncodedLength(byte[] bytes) {
512 return (bytes.length + 2) / 3 * 4;
513 }
514
515 private static String encodeQ(String prefix, String text, Usage usage,
516 int usedCharacters, Charset charset, byte[] bytes) {
517 int encodedLength = qEncodedLength(bytes, usage);
518
519 int totalLength = prefix.length() + encodedLength
520 + ENC_WORD_SUFFIX.length();
521 if (totalLength <= ENCODED_WORD_MAX_LENGTH - usedCharacters) {
522 return prefix + encodeQ(bytes, usage) + ENC_WORD_SUFFIX;
523 } else {
524 String part1 = text.substring(0, text.length() / 2);
525 byte[] bytes1 = encode(part1, charset);
526 String word1 = encodeQ(prefix, part1, usage, usedCharacters,
527 charset, bytes1);
528
529 String part2 = text.substring(text.length() / 2);
530 byte[] bytes2 = encode(part2, charset);
531 String word2 = encodeQ(prefix, part2, usage, 0, charset, bytes2);
532
533 return word1 + " " + word2;
534 }
535 }
536
537 private static int qEncodedLength(byte[] bytes, Usage usage) {
538 BitSet qChars = usage == Usage.TEXT_TOKEN ? Q_REGULAR_CHARS
539 : Q_RESTRICTED_CHARS;
540
541 int count = 0;
542
543 for (int idx = 0; idx < bytes.length; idx++) {
544 int v = bytes[idx] & 0xff;
545 if (v == 32) {
546 count++;
547 } else if (!qChars.get(v)) {
548 count += 3;
549 } else {
550 count++;
551 }
552 }
553
554 return count;
555 }
556
557 private static byte[] encode(String text, Charset charset) {
558 ByteBuffer buffer = charset.encode(text);
559 byte[] bytes = new byte[buffer.limit()];
560 buffer.get(bytes);
561 return bytes;
562 }
563
564 private static Charset determineCharset(String text) {
565 // it is an important property of iso-8859-1 that it directly maps
566 // unicode code points 0000 to 00ff to byte values 00 to ff.
567 boolean ascii = true;
568 final int len = text.length();
569 for (int index = 0; index < len; index++) {
570 char ch = text.charAt(index);
571 if (ch > 0xff) {
572 return CharsetUtil.UTF_8;
573 }
574 if (ch > 0x7f) {
575 ascii = false;
576 }
577 }
578 return ascii ? CharsetUtil.US_ASCII : CharsetUtil.ISO_8859_1;
579 }
580
581 private static Encoding determineEncoding(byte[] bytes, Usage usage) {
582 if (bytes.length == 0)
583 return Encoding.Q;
584
585 BitSet qChars = usage == Usage.TEXT_TOKEN ? Q_REGULAR_CHARS
586 : Q_RESTRICTED_CHARS;
587
588 int qEncoded = 0;
589 for (int i = 0; i < bytes.length; i++) {
590 int v = bytes[i] & 0xff;
591 if (v != 32 && !qChars.get(v)) {
592 qEncoded++;
593 }
594 }
595
596 int percentage = qEncoded * 100 / bytes.length;
597 return percentage > 30 ? Encoding.B : Encoding.Q;
598 }
599
600 private static char hexDigit(int i) {
601 return i < 10 ? (char) (i + '0') : (char) (i - 10 + 'A');
602 }
603 }