1 /*
2 * Copyright (C) 2006-2008, Shawn O. Pearce <spearce@spearce.org>
3 * and other copyright owners as documented in the project's IP log.
4 *
5 * This program and the accompanying materials are made available
6 * under the terms of the Eclipse Distribution License v1.0 which
7 * accompanies this distribution, is reproduced below, and is
8 * available at http://www.eclipse.org/org/documents/edl-v10.php
9 *
10 * All rights reserved.
11 *
12 * Redistribution and use in source and binary forms, with or
13 * without modification, are permitted provided that the following
14 * conditions are met:
15 *
16 * - Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 *
19 * - Redistributions in binary form must reproduce the above
20 * copyright notice, this list of conditions and the following
21 * disclaimer in the documentation and/or other materials provided
22 * with the distribution.
23 *
24 * - Neither the name of the Eclipse Foundation, Inc. nor the
25 * names of its contributors may be used to endorse or promote
26 * products derived from this software without specific prior
27 * written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
30 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
31 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
32 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
33 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
34 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
35 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
36 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
37 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
38 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
40 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
41 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
42 */
43
44 package org.eclipse.jgit.lib;
45
46 import java.io.IOException;
47 import java.io.OutputStream;
48 import java.io.Writer;
49 import java.nio.ByteBuffer;
50
51 import org.eclipse.jgit.util.NB;
52
53 /**
54 * A (possibly mutable) SHA-1 abstraction.
55 * <p>
56 * If this is an instance of {@link MutableObjectId} the concept of equality
57 * with this instance can alter at any time, if this instance is modified to
58 * represent a different object name.
59 */
60 public abstract class AnyObjectId implements Comparable<AnyObjectId> {
61
62 /**
63 * Compare to object identifier byte sequences for equality.
64 *
65 * @param firstObjectId
66 * the first identifier to compare. Must not be null.
67 * @param secondObjectId
68 * the second identifier to compare. Must not be null.
69 * @return true if the two identifiers are the same.
70 */
71 public static boolean equals(final AnyObjectId firstObjectId,
72 final AnyObjectId secondObjectId) {
73 if (firstObjectId == secondObjectId)
74 return true;
75
76 // We test word 2 first as odds are someone already used our
77 // word 1 as a hash code, and applying that came up with these
78 // two instances we are comparing for equality. Therefore the
79 // first two words are very likely to be identical. We want to
80 // break away from collisions as quickly as possible.
81 //
82 return firstObjectId.w2 == secondObjectId.w2
83 && firstObjectId.w3 == secondObjectId.w3
84 && firstObjectId.w4 == secondObjectId.w4
85 && firstObjectId.w5 == secondObjectId.w5
86 && firstObjectId.w1 == secondObjectId.w1;
87 }
88
89 int w1;
90
91 int w2;
92
93 int w3;
94
95 int w4;
96
97 int w5;
98
99 /**
100 * Get the first 8 bits of the ObjectId.
101 *
102 * This is a faster version of {@code getByte(0)}.
103 *
104 * @return a discriminator usable for a fan-out style map. Returned values
105 * are unsigned and thus are in the range [0,255] rather than the
106 * signed byte range of [-128, 127].
107 */
108 public final int getFirstByte() {
109 return w1 >>> 24;
110 }
111
112 /**
113 * Get any byte from the ObjectId.
114 *
115 * Callers hard-coding {@code getByte(0)} should instead use the much faster
116 * special case variant {@link #getFirstByte()}.
117 *
118 * @param index
119 * index of the byte to obtain from the raw form of the ObjectId.
120 * Must be in range [0, {@link Constants#OBJECT_ID_LENGTH}).
121 * @return the value of the requested byte at {@code index}. Returned values
122 * are unsigned and thus are in the range [0,255] rather than the
123 * signed byte range of [-128, 127].
124 * @throws ArrayIndexOutOfBoundsException
125 * {@code index} is less than 0, equal to
126 * {@link Constants#OBJECT_ID_LENGTH}, or greater than
127 * {@link Constants#OBJECT_ID_LENGTH}.
128 */
129 public final int getByte(int index) {
130 int w;
131 switch (index >> 2) {
132 case 0:
133 w = w1;
134 break;
135 case 1:
136 w = w2;
137 break;
138 case 2:
139 w = w3;
140 break;
141 case 3:
142 w = w4;
143 break;
144 case 4:
145 w = w5;
146 break;
147 default:
148 throw new ArrayIndexOutOfBoundsException(index);
149 }
150
151 return (w >>> (8 * (3 - (index & 3)))) & 0xff;
152 }
153
154 /**
155 * Compare this ObjectId to another and obtain a sort ordering.
156 *
157 * @param other
158 * the other id to compare to. Must not be null.
159 * @return < 0 if this id comes before other; 0 if this id is equal to
160 * other; > 0 if this id comes after other.
161 */
162 public final int compareTo(final AnyObjectId other) {
163 if (this == other)
164 return 0;
165
166 int cmp;
167
168 cmp = NB.compareUInt32(w1, other.w1);
169 if (cmp != 0)
170 return cmp;
171
172 cmp = NB.compareUInt32(w2, other.w2);
173 if (cmp != 0)
174 return cmp;
175
176 cmp = NB.compareUInt32(w3, other.w3);
177 if (cmp != 0)
178 return cmp;
179
180 cmp = NB.compareUInt32(w4, other.w4);
181 if (cmp != 0)
182 return cmp;
183
184 return NB.compareUInt32(w5, other.w5);
185 }
186
187 /**
188 * Compare this ObjectId to a network-byte-order ObjectId.
189 *
190 * @param bs
191 * array containing the other ObjectId in network byte order.
192 * @param p
193 * position within {@code bs} to start the compare at. At least
194 * 20 bytes, starting at this position are required.
195 * @return a negative integer, zero, or a positive integer as this object is
196 * less than, equal to, or greater than the specified object.
197 */
198 public final int compareTo(final byte[] bs, final int p) {
199 int cmp;
200
201 cmp = NB.compareUInt32(w1, NB.decodeInt32(bs, p));
202 if (cmp != 0)
203 return cmp;
204
205 cmp = NB.compareUInt32(w2, NB.decodeInt32(bs, p + 4));
206 if (cmp != 0)
207 return cmp;
208
209 cmp = NB.compareUInt32(w3, NB.decodeInt32(bs, p + 8));
210 if (cmp != 0)
211 return cmp;
212
213 cmp = NB.compareUInt32(w4, NB.decodeInt32(bs, p + 12));
214 if (cmp != 0)
215 return cmp;
216
217 return NB.compareUInt32(w5, NB.decodeInt32(bs, p + 16));
218 }
219
220 /**
221 * Compare this ObjectId to a network-byte-order ObjectId.
222 *
223 * @param bs
224 * array containing the other ObjectId in network byte order.
225 * @param p
226 * position within {@code bs} to start the compare at. At least 5
227 * integers, starting at this position are required.
228 * @return a negative integer, zero, or a positive integer as this object is
229 * less than, equal to, or greater than the specified object.
230 */
231 public final int compareTo(final int[] bs, final int p) {
232 int cmp;
233
234 cmp = NB.compareUInt32(w1, bs[p]);
235 if (cmp != 0)
236 return cmp;
237
238 cmp = NB.compareUInt32(w2, bs[p + 1]);
239 if (cmp != 0)
240 return cmp;
241
242 cmp = NB.compareUInt32(w3, bs[p + 2]);
243 if (cmp != 0)
244 return cmp;
245
246 cmp = NB.compareUInt32(w4, bs[p + 3]);
247 if (cmp != 0)
248 return cmp;
249
250 return NB.compareUInt32(w5, bs[p + 4]);
251 }
252
253 /**
254 * Tests if this ObjectId starts with the given abbreviation.
255 *
256 * @param abbr
257 * the abbreviation.
258 * @return true if this ObjectId begins with the abbreviation; else false.
259 */
260 public boolean startsWith(final AbbreviatedObjectId abbr) {
261 return abbr.prefixCompare(this) == 0;
262 }
263
264 public final int hashCode() {
265 return w2;
266 }
267
268 /**
269 * Determine if this ObjectId has exactly the same value as another.
270 *
271 * @param other
272 * the other id to compare to. May be null.
273 * @return true only if both ObjectIds have identical bits.
274 */
275 public final boolean equals(final AnyObjectId other) {
276 return other != null ? equals(this, other) : false;
277 }
278
279 public final boolean equals(final Object o) {
280 if (o instanceof AnyObjectId)
281 return equals((AnyObjectId) o);
282 else
283 return false;
284 }
285
286 /**
287 * Copy this ObjectId to an output writer in raw binary.
288 *
289 * @param w
290 * the buffer to copy to. Must be in big endian order.
291 */
292 public void copyRawTo(final ByteBuffer w) {
293 w.putInt(w1);
294 w.putInt(w2);
295 w.putInt(w3);
296 w.putInt(w4);
297 w.putInt(w5);
298 }
299
300 /**
301 * Copy this ObjectId to a byte array.
302 *
303 * @param b
304 * the buffer to copy to.
305 * @param o
306 * the offset within b to write at.
307 */
308 public void copyRawTo(final byte[] b, final int o) {
309 NB.encodeInt32(b, o, w1);
310 NB.encodeInt32(b, o + 4, w2);
311 NB.encodeInt32(b, o + 8, w3);
312 NB.encodeInt32(b, o + 12, w4);
313 NB.encodeInt32(b, o + 16, w5);
314 }
315
316 /**
317 * Copy this ObjectId to an int array.
318 *
319 * @param b
320 * the buffer to copy to.
321 * @param o
322 * the offset within b to write at.
323 */
324 public void copyRawTo(final int[] b, final int o) {
325 b[o] = w1;
326 b[o + 1] = w2;
327 b[o + 2] = w3;
328 b[o + 3] = w4;
329 b[o + 4] = w5;
330 }
331
332 /**
333 * Copy this ObjectId to an output writer in raw binary.
334 *
335 * @param w
336 * the stream to write to.
337 * @throws IOException
338 * the stream writing failed.
339 */
340 public void copyRawTo(final OutputStream w) throws IOException {
341 writeRawInt(w, w1);
342 writeRawInt(w, w2);
343 writeRawInt(w, w3);
344 writeRawInt(w, w4);
345 writeRawInt(w, w5);
346 }
347
348 private static void writeRawInt(final OutputStream w, int v)
349 throws IOException {
350 w.write(v >>> 24);
351 w.write(v >>> 16);
352 w.write(v >>> 8);
353 w.write(v);
354 }
355
356 /**
357 * Copy this ObjectId to an output writer in hex format.
358 *
359 * @param w
360 * the stream to copy to.
361 * @throws IOException
362 * the stream writing failed.
363 */
364 public void copyTo(final OutputStream w) throws IOException {
365 w.write(toHexByteArray());
366 }
367
368 /**
369 * Copy this ObjectId to a byte array in hex format.
370 *
371 * @param b
372 * the buffer to copy to.
373 * @param o
374 * the offset within b to write at.
375 */
376 public void copyTo(byte[] b, int o) {
377 formatHexByte(b, o + 0, w1);
378 formatHexByte(b, o + 8, w2);
379 formatHexByte(b, o + 16, w3);
380 formatHexByte(b, o + 24, w4);
381 formatHexByte(b, o + 32, w5);
382 }
383
384 /**
385 * Copy this ObjectId to a ByteBuffer in hex format.
386 *
387 * @param b
388 * the buffer to copy to.
389 */
390 public void copyTo(ByteBuffer b) {
391 b.put(toHexByteArray());
392 }
393
394 private byte[] toHexByteArray() {
395 final byte[] dst = new byte[Constants.OBJECT_ID_STRING_LENGTH];
396 formatHexByte(dst, 0, w1);
397 formatHexByte(dst, 8, w2);
398 formatHexByte(dst, 16, w3);
399 formatHexByte(dst, 24, w4);
400 formatHexByte(dst, 32, w5);
401 return dst;
402 }
403
404 private static final byte[] hexbyte = { '0', '1', '2', '3', '4', '5', '6',
405 '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
406
407 private static void formatHexByte(final byte[] dst, final int p, int w) {
408 int o = p + 7;
409 while (o >= p && w != 0) {
410 dst[o--] = hexbyte[w & 0xf];
411 w >>>= 4;
412 }
413 while (o >= p)
414 dst[o--] = '0';
415 }
416
417 /**
418 * Copy this ObjectId to an output writer in hex format.
419 *
420 * @param w
421 * the stream to copy to.
422 * @throws IOException
423 * the stream writing failed.
424 */
425 public void copyTo(final Writer w) throws IOException {
426 w.write(toHexCharArray());
427 }
428
429 /**
430 * Copy this ObjectId to an output writer in hex format.
431 *
432 * @param tmp
433 * temporary char array to buffer construct into before writing.
434 * Must be at least large enough to hold 2 digits for each byte
435 * of object id (40 characters or larger).
436 * @param w
437 * the stream to copy to.
438 * @throws IOException
439 * the stream writing failed.
440 */
441 public void copyTo(final char[] tmp, final Writer w) throws IOException {
442 toHexCharArray(tmp);
443 w.write(tmp, 0, Constants.OBJECT_ID_STRING_LENGTH);
444 }
445
446 /**
447 * Copy this ObjectId to a StringBuilder in hex format.
448 *
449 * @param tmp
450 * temporary char array to buffer construct into before writing.
451 * Must be at least large enough to hold 2 digits for each byte
452 * of object id (40 characters or larger).
453 * @param w
454 * the string to append onto.
455 */
456 public void copyTo(final char[] tmp, final StringBuilder w) {
457 toHexCharArray(tmp);
458 w.append(tmp, 0, Constants.OBJECT_ID_STRING_LENGTH);
459 }
460
461 private char[] toHexCharArray() {
462 final char[] dst = new char[Constants.OBJECT_ID_STRING_LENGTH];
463 toHexCharArray(dst);
464 return dst;
465 }
466
467 private void toHexCharArray(final char[] dst) {
468 formatHexChar(dst, 0, w1);
469 formatHexChar(dst, 8, w2);
470 formatHexChar(dst, 16, w3);
471 formatHexChar(dst, 24, w4);
472 formatHexChar(dst, 32, w5);
473 }
474
475 private static final char[] hexchar = { '0', '1', '2', '3', '4', '5', '6',
476 '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
477
478 static void formatHexChar(final char[] dst, final int p, int w) {
479 int o = p + 7;
480 while (o >= p && w != 0) {
481 dst[o--] = hexchar[w & 0xf];
482 w >>>= 4;
483 }
484 while (o >= p)
485 dst[o--] = '0';
486 }
487
488 @SuppressWarnings("nls")
489 @Override
490 public String toString() {
491 return "AnyObjectId[" + name() + "]";
492 }
493
494 /**
495 * @return string form of the SHA-1, in lower case hexadecimal.
496 */
497 public final String name() {
498 return new String(toHexCharArray());
499 }
500
501 /**
502 * @return string form of the SHA-1, in lower case hexadecimal.
503 */
504 public final String getName() {
505 return name();
506 }
507
508 /**
509 * Return an abbreviation (prefix) of this object SHA-1.
510 * <p>
511 * This implementation does not guarantee uniqueness. Callers should
512 * instead use {@link ObjectReader#abbreviate(AnyObjectId, int)} to obtain a
513 * unique abbreviation within the scope of a particular object database.
514 *
515 * @param len
516 * length of the abbreviated string.
517 * @return SHA-1 abbreviation.
518 */
519 public AbbreviatedObjectId abbreviate(final int len) {
520 final int a = AbbreviatedObjectId.mask(len, 1, w1);
521 final int b = AbbreviatedObjectId.mask(len, 2, w2);
522 final int c = AbbreviatedObjectId.mask(len, 3, w3);
523 final int d = AbbreviatedObjectId.mask(len, 4, w4);
524 final int e = AbbreviatedObjectId.mask(len, 5, w5);
525 return new AbbreviatedObjectId(len, a, b, c, d, e);
526 }
527
528 /**
529 * Obtain an immutable copy of this current object name value.
530 * <p>
531 * Only returns <code>this</code> if this instance is an unsubclassed
532 * instance of {@link ObjectId}; otherwise a new instance is returned
533 * holding the same value.
534 * <p>
535 * This method is useful to shed any additional memory that may be tied to
536 * the subclass, yet retain the unique identity of the object id for future
537 * lookups within maps and repositories.
538 *
539 * @return an immutable copy, using the smallest memory footprint possible.
540 */
541 public final ObjectId copy() {
542 if (getClass() == ObjectId.class)
543 return (ObjectId) this;
544 return new ObjectId(this);
545 }
546
547 /**
548 * Obtain an immutable copy of this current object name value.
549 * <p>
550 * See {@link #copy()} if <code>this</code> is a possibly subclassed (but
551 * immutable) identity and the application needs a lightweight identity
552 * <i>only</i> reference.
553 *
554 * @return an immutable copy. May be <code>this</code> if this is already
555 * an immutable instance.
556 */
557 public abstract ObjectId toObjectId();
558 }