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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.commons.codec.binary;
19  
20  import java.util.Arrays;
21  
22  import org.apache.commons.codec.BinaryDecoder;
23  import org.apache.commons.codec.BinaryEncoder;
24  import org.apache.commons.codec.DecoderException;
25  import org.apache.commons.codec.EncoderException;
26  
27  /**
28   * Abstract superclass for Base-N encoders and decoders.
29   *
30   * <p>
31   * This class is thread-safe.
32   * </p>
33   *
34   * @version $Id: BaseNCodec.java 1563226 2014-01-31 19:38:06Z ggregory $
35   */
36  public abstract class BaseNCodec implements BinaryEncoder, BinaryDecoder {
37  
38      /**
39       * Holds thread context so classes can be thread-safe.
40       *
41       * This class is not itself thread-safe; each thread must allocate its own copy.
42       *
43       * @since 1.7
44       */
45      static class Context {
46  
47          /**
48           * Place holder for the bytes we're dealing with for our based logic.
49           * Bitwise operations store and extract the encoding or decoding from this variable.
50           */
51          int ibitWorkArea;
52  
53          /**
54           * Place holder for the bytes we're dealing with for our based logic.
55           * Bitwise operations store and extract the encoding or decoding from this variable.
56           */
57          long lbitWorkArea;
58  
59          /**
60           * Buffer for streaming.
61           */
62          byte[] buffer;
63  
64          /**
65           * Position where next character should be written in the buffer.
66           */
67          int pos;
68  
69          /**
70           * Position where next character should be read from the buffer.
71           */
72          int readPos;
73  
74          /**
75           * Boolean flag to indicate the EOF has been reached. Once EOF has been reached, this object becomes useless,
76           * and must be thrown away.
77           */
78          boolean eof;
79  
80          /**
81           * Variable tracks how many characters have been written to the current line. Only used when encoding. We use
82           * it to make sure each encoded line never goes beyond lineLength (if lineLength &gt; 0).
83           */
84          int currentLinePos;
85  
86          /**
87           * Writes to the buffer only occur after every 3/5 reads when encoding, and every 4/8 reads when decoding. This
88           * variable helps track that.
89           */
90          int modulus;
91  
92          Context() {
93          }
94  
95          /**
96           * Returns a String useful for debugging (especially within a debugger.)
97           *
98           * @return a String useful for debugging.
99           */
100         @SuppressWarnings("boxing") // OK to ignore boxing here
101         @Override
102         public String toString() {
103             return String.format("%s[buffer=%s, currentLinePos=%s, eof=%s, ibitWorkArea=%s, lbitWorkArea=%s, " +
104                     "modulus=%s, pos=%s, readPos=%s]", this.getClass().getSimpleName(), Arrays.toString(buffer),
105                     currentLinePos, eof, ibitWorkArea, lbitWorkArea, modulus, pos, readPos);
106         }
107     }
108 
109     /**
110      * EOF
111      *
112      * @since 1.7
113      */
114     static final int EOF = -1;
115 
116     /**
117      *  MIME chunk size per RFC 2045 section 6.8.
118      *
119      * <p>
120      * The {@value} character limit does not count the trailing CRLF, but counts all other characters, including any
121      * equal signs.
122      * </p>
123      *
124      * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 6.8</a>
125      */
126     public static final int MIME_CHUNK_SIZE = 76;
127 
128     /**
129      * PEM chunk size per RFC 1421 section 4.3.2.4.
130      *
131      * <p>
132      * The {@value} character limit does not count the trailing CRLF, but counts all other characters, including any
133      * equal signs.
134      * </p>
135      *
136      * @see <a href="http://tools.ietf.org/html/rfc1421">RFC 1421 section 4.3.2.4</a>
137      */
138     public static final int PEM_CHUNK_SIZE = 64;
139 
140     private static final int DEFAULT_BUFFER_RESIZE_FACTOR = 2;
141 
142     /**
143      * Defines the default buffer size - currently {@value}
144      * - must be large enough for at least one encoded block+separator
145      */
146     private static final int DEFAULT_BUFFER_SIZE = 8192;
147 
148     /** Mask used to extract 8 bits, used in decoding bytes */
149     protected static final int MASK_8BITS = 0xff;
150 
151     /**
152      * Byte used to pad output.
153      */
154     protected static final byte PAD_DEFAULT = '='; // Allow static access to default
155 
156     protected final byte PAD = PAD_DEFAULT; // instance variable just in case it needs to vary later
157 
158     /** Number of bytes in each full block of unencoded data, e.g. 4 for Base64 and 5 for Base32 */
159     private final int unencodedBlockSize;
160 
161     /** Number of bytes in each full block of encoded data, e.g. 3 for Base64 and 8 for Base32 */
162     private final int encodedBlockSize;
163 
164     /**
165      * Chunksize for encoding. Not used when decoding.
166      * A value of zero or less implies no chunking of the encoded data.
167      * Rounded down to nearest multiple of encodedBlockSize.
168      */
169     protected final int lineLength;
170 
171     /**
172      * Size of chunk separator. Not used unless {@link #lineLength} &gt; 0.
173      */
174     private final int chunkSeparatorLength;
175 
176     /**
177      * Note <code>lineLength</code> is rounded down to the nearest multiple of {@link #encodedBlockSize}
178      * If <code>chunkSeparatorLength</code> is zero, then chunking is disabled.
179      * @param unencodedBlockSize the size of an unencoded block (e.g. Base64 = 3)
180      * @param encodedBlockSize the size of an encoded block (e.g. Base64 = 4)
181      * @param lineLength if &gt; 0, use chunking with a length <code>lineLength</code>
182      * @param chunkSeparatorLength the chunk separator length, if relevant
183      */
184     protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize,
185                          final int lineLength, final int chunkSeparatorLength) {
186         this.unencodedBlockSize = unencodedBlockSize;
187         this.encodedBlockSize = encodedBlockSize;
188         final boolean useChunking = lineLength > 0 && chunkSeparatorLength > 0;
189         this.lineLength = useChunking ? (lineLength / encodedBlockSize) * encodedBlockSize : 0;
190         this.chunkSeparatorLength = chunkSeparatorLength;
191     }
192 
193     /**
194      * Returns true if this object has buffered data for reading.
195      *
196      * @param context the context to be used
197      * @return true if there is data still available for reading.
198      */
199     boolean hasData(final Context context) {  // package protected for access from I/O streams
200         return context.buffer != null;
201     }
202 
203     /**
204      * Returns the amount of buffered data available for reading.
205      *
206      * @param context the context to be used
207      * @return The amount of buffered data available for reading.
208      */
209     int available(final Context context) {  // package protected for access from I/O streams
210         return context.buffer != null ? context.pos - context.readPos : 0;
211     }
212 
213     /**
214      * Get the default buffer size. Can be overridden.
215      *
216      * @return {@link #DEFAULT_BUFFER_SIZE}
217      */
218     protected int getDefaultBufferSize() {
219         return DEFAULT_BUFFER_SIZE;
220     }
221 
222     /**
223      * Increases our buffer by the {@link #DEFAULT_BUFFER_RESIZE_FACTOR}.
224      * @param context the context to be used
225      */
226     private byte[] resizeBuffer(final Context context) {
227         if (context.buffer == null) {
228             context.buffer = new byte[getDefaultBufferSize()];
229             context.pos = 0;
230             context.readPos = 0;
231         } else {
232             final byte[] b = new byte[context.buffer.length * DEFAULT_BUFFER_RESIZE_FACTOR];
233             System.arraycopy(context.buffer, 0, b, 0, context.buffer.length);
234             context.buffer = b;
235         }
236         return context.buffer;
237     }
238 
239     /**
240      * Ensure that the buffer has room for <code>size</code> bytes
241      *
242      * @param size minimum spare space required
243      * @param context the context to be used
244      */
245     protected byte[] ensureBufferSize(final int size, final Context context){
246         if ((context.buffer == null) || (context.buffer.length < context.pos + size)){
247             return resizeBuffer(context);
248         }
249         return context.buffer;
250     }
251 
252     /**
253      * Extracts buffered data into the provided byte[] array, starting at position bPos, up to a maximum of bAvail
254      * bytes. Returns how many bytes were actually extracted.
255      * <p>
256      * Package protected for access from I/O streams.
257      *
258      * @param b
259      *            byte[] array to extract the buffered data into.
260      * @param bPos
261      *            position in byte[] array to start extraction at.
262      * @param bAvail
263      *            amount of bytes we're allowed to extract. We may extract fewer (if fewer are available).
264      * @param context
265      *            the context to be used
266      * @return The number of bytes successfully extracted into the provided byte[] array.
267      */
268     int readResults(final byte[] b, final int bPos, final int bAvail, final Context context) {
269         if (context.buffer != null) {
270             final int len = Math.min(available(context), bAvail);
271             System.arraycopy(context.buffer, context.readPos, b, bPos, len);
272             context.readPos += len;
273             if (context.readPos >= context.pos) {
274                 context.buffer = null; // so hasData() will return false, and this method can return -1
275             }
276             return len;
277         }
278         return context.eof ? EOF : 0;
279     }
280 
281     /**
282      * Checks if a byte value is whitespace or not.
283      * Whitespace is taken to mean: space, tab, CR, LF
284      * @param byteToCheck
285      *            the byte to check
286      * @return true if byte is whitespace, false otherwise
287      */
288     protected static boolean isWhiteSpace(final byte byteToCheck) {
289         switch (byteToCheck) {
290             case ' ' :
291             case '\n' :
292             case '\r' :
293             case '\t' :
294                 return true;
295             default :
296                 return false;
297         }
298     }
299 
300     /**
301      * Encodes an Object using the Base-N algorithm. This method is provided in order to satisfy the requirements of
302      * the Encoder interface, and will throw an EncoderException if the supplied object is not of type byte[].
303      *
304      * @param obj
305      *            Object to encode
306      * @return An object (of type byte[]) containing the Base-N encoded data which corresponds to the byte[] supplied.
307      * @throws EncoderException
308      *             if the parameter supplied is not of type byte[]
309      */
310     @Override
311     public Object encode(final Object obj) throws EncoderException {
312         if (!(obj instanceof byte[])) {
313             throw new EncoderException("Parameter supplied to Base-N encode is not a byte[]");
314         }
315         return encode((byte[]) obj);
316     }
317 
318     /**
319      * Encodes a byte[] containing binary data, into a String containing characters in the Base-N alphabet.
320      * Uses UTF8 encoding.
321      *
322      * @param pArray
323      *            a byte array containing binary data
324      * @return A String containing only Base-N character data
325      */
326     public String encodeToString(final byte[] pArray) {
327         return StringUtils.newStringUtf8(encode(pArray));
328     }
329 
330     /**
331      * Encodes a byte[] containing binary data, into a String containing characters in the appropriate alphabet.
332      * Uses UTF8 encoding.
333      *
334      * @param pArray a byte array containing binary data
335      * @return String containing only character data in the appropriate alphabet.
336     */
337     public String encodeAsString(final byte[] pArray){
338         return StringUtils.newStringUtf8(encode(pArray));
339     }
340 
341     /**
342      * Decodes an Object using the Base-N algorithm. This method is provided in order to satisfy the requirements of
343      * the Decoder interface, and will throw a DecoderException if the supplied object is not of type byte[] or String.
344      *
345      * @param obj
346      *            Object to decode
347      * @return An object (of type byte[]) containing the binary data which corresponds to the byte[] or String
348      *         supplied.
349      * @throws DecoderException
350      *             if the parameter supplied is not of type byte[]
351      */
352     @Override
353     public Object decode(final Object obj) throws DecoderException {
354         if (obj instanceof byte[]) {
355             return decode((byte[]) obj);
356         } else if (obj instanceof String) {
357             return decode((String) obj);
358         } else {
359             throw new DecoderException("Parameter supplied to Base-N decode is not a byte[] or a String");
360         }
361     }
362 
363     /**
364      * Decodes a String containing characters in the Base-N alphabet.
365      *
366      * @param pArray
367      *            A String containing Base-N character data
368      * @return a byte array containing binary data
369      */
370     public byte[] decode(final String pArray) {
371         return decode(StringUtils.getBytesUtf8(pArray));
372     }
373 
374     /**
375      * Decodes a byte[] containing characters in the Base-N alphabet.
376      *
377      * @param pArray
378      *            A byte array containing Base-N character data
379      * @return a byte array containing binary data
380      */
381     @Override
382     public byte[] decode(final byte[] pArray) {
383         if (pArray == null || pArray.length == 0) {
384             return pArray;
385         }
386         final Context context = new Context();
387         decode(pArray, 0, pArray.length, context);
388         decode(pArray, 0, EOF, context); // Notify decoder of EOF.
389         final byte[] result = new byte[context.pos];
390         readResults(result, 0, result.length, context);
391         return result;
392     }
393 
394     /**
395      * Encodes a byte[] containing binary data, into a byte[] containing characters in the alphabet.
396      *
397      * @param pArray
398      *            a byte array containing binary data
399      * @return A byte array containing only the basen alphabetic character data
400      */
401     @Override
402     public byte[] encode(final byte[] pArray) {
403         if (pArray == null || pArray.length == 0) {
404             return pArray;
405         }
406         final Context context = new Context();
407         encode(pArray, 0, pArray.length, context);
408         encode(pArray, 0, EOF, context); // Notify encoder of EOF.
409         final byte[] buf = new byte[context.pos - context.readPos];
410         readResults(buf, 0, buf.length, context);
411         return buf;
412     }
413 
414     // package protected for access from I/O streams
415     abstract void encode(byte[] pArray, int i, int length, Context context);
416 
417     // package protected for access from I/O streams
418     abstract void decode(byte[] pArray, int i, int length, Context context);
419 
420     /**
421      * Returns whether or not the <code>octet</code> is in the current alphabet.
422      * Does not allow whitespace or pad.
423      *
424      * @param value The value to test
425      *
426      * @return {@code true} if the value is defined in the current alphabet, {@code false} otherwise.
427      */
428     protected abstract boolean isInAlphabet(byte value);
429 
430     /**
431      * Tests a given byte array to see if it contains only valid characters within the alphabet.
432      * The method optionally treats whitespace and pad as valid.
433      *
434      * @param arrayOctet byte array to test
435      * @param allowWSPad if {@code true}, then whitespace and PAD are also allowed
436      *
437      * @return {@code true} if all bytes are valid characters in the alphabet or if the byte array is empty;
438      *         {@code false}, otherwise
439      */
440     public boolean isInAlphabet(final byte[] arrayOctet, final boolean allowWSPad) {
441         for (int i = 0; i < arrayOctet.length; i++) {
442             if (!isInAlphabet(arrayOctet[i]) &&
443                     (!allowWSPad || (arrayOctet[i] != PAD) && !isWhiteSpace(arrayOctet[i]))) {
444                 return false;
445             }
446         }
447         return true;
448     }
449 
450     /**
451      * Tests a given String to see if it contains only valid characters within the alphabet.
452      * The method treats whitespace and PAD as valid.
453      *
454      * @param basen String to test
455      * @return {@code true} if all characters in the String are valid characters in the alphabet or if
456      *         the String is empty; {@code false}, otherwise
457      * @see #isInAlphabet(byte[], boolean)
458      */
459     public boolean isInAlphabet(final String basen) {
460         return isInAlphabet(StringUtils.getBytesUtf8(basen), true);
461     }
462 
463     /**
464      * Tests a given byte array to see if it contains any characters within the alphabet or PAD.
465      *
466      * Intended for use in checking line-ending arrays
467      *
468      * @param arrayOctet
469      *            byte array to test
470      * @return {@code true} if any byte is a valid character in the alphabet or PAD; {@code false} otherwise
471      */
472     protected boolean containsAlphabetOrPad(final byte[] arrayOctet) {
473         if (arrayOctet == null) {
474             return false;
475         }
476         for (final byte element : arrayOctet) {
477             if (PAD == element || isInAlphabet(element)) {
478                 return true;
479             }
480         }
481         return false;
482     }
483 
484     /**
485      * Calculates the amount of space needed to encode the supplied array.
486      *
487      * @param pArray byte[] array which will later be encoded
488      *
489      * @return amount of space needed to encoded the supplied array.
490      * Returns a long since a max-len array will require &gt; Integer.MAX_VALUE
491      */
492     public long getEncodedLength(final byte[] pArray) {
493         // Calculate non-chunked size - rounded up to allow for padding
494         // cast to long is needed to avoid possibility of overflow
495         long len = ((pArray.length + unencodedBlockSize-1)  / unencodedBlockSize) * (long) encodedBlockSize;
496         if (lineLength > 0) { // We're using chunking
497             // Round up to nearest multiple
498             len += ((len + lineLength-1) / lineLength) * chunkSeparatorLength;
499         }
500         return len;
501     }
502 }