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 @Override
163 public final int compareTo(final AnyObjectId other) {
164 if (this == other)
165 return 0;
166
167 int cmp;
168
169 cmp = NB.compareUInt32(w1, other.w1);
170 if (cmp != 0)
171 return cmp;
172
173 cmp = NB.compareUInt32(w2, other.w2);
174 if (cmp != 0)
175 return cmp;
176
177 cmp = NB.compareUInt32(w3, other.w3);
178 if (cmp != 0)
179 return cmp;
180
181 cmp = NB.compareUInt32(w4, other.w4);
182 if (cmp != 0)
183 return cmp;
184
185 return NB.compareUInt32(w5, other.w5);
186 }
187
188 /**
189 * Compare this ObjectId to a network-byte-order ObjectId.
190 *
191 * @param bs
192 * array containing the other ObjectId in network byte order.
193 * @param p
194 * position within {@code bs} to start the compare at. At least
195 * 20 bytes, starting at this position are required.
196 * @return a negative integer, zero, or a positive integer as this object is
197 * less than, equal to, or greater than the specified object.
198 */
199 public final int compareTo(final byte[] bs, final int p) {
200 int cmp;
201
202 cmp = NB.compareUInt32(w1, NB.decodeInt32(bs, p));
203 if (cmp != 0)
204 return cmp;
205
206 cmp = NB.compareUInt32(w2, NB.decodeInt32(bs, p + 4));
207 if (cmp != 0)
208 return cmp;
209
210 cmp = NB.compareUInt32(w3, NB.decodeInt32(bs, p + 8));
211 if (cmp != 0)
212 return cmp;
213
214 cmp = NB.compareUInt32(w4, NB.decodeInt32(bs, p + 12));
215 if (cmp != 0)
216 return cmp;
217
218 return NB.compareUInt32(w5, NB.decodeInt32(bs, p + 16));
219 }
220
221 /**
222 * Compare this ObjectId to a network-byte-order ObjectId.
223 *
224 * @param bs
225 * array containing the other ObjectId in network byte order.
226 * @param p
227 * position within {@code bs} to start the compare at. At least 5
228 * integers, starting at this position are required.
229 * @return a negative integer, zero, or a positive integer as this object is
230 * less than, equal to, or greater than the specified object.
231 */
232 public final int compareTo(final int[] bs, final int p) {
233 int cmp;
234
235 cmp = NB.compareUInt32(w1, bs[p]);
236 if (cmp != 0)
237 return cmp;
238
239 cmp = NB.compareUInt32(w2, bs[p + 1]);
240 if (cmp != 0)
241 return cmp;
242
243 cmp = NB.compareUInt32(w3, bs[p + 2]);
244 if (cmp != 0)
245 return cmp;
246
247 cmp = NB.compareUInt32(w4, bs[p + 3]);
248 if (cmp != 0)
249 return cmp;
250
251 return NB.compareUInt32(w5, bs[p + 4]);
252 }
253
254 /**
255 * Tests if this ObjectId starts with the given abbreviation.
256 *
257 * @param abbr
258 * the abbreviation.
259 * @return true if this ObjectId begins with the abbreviation; else false.
260 */
261 public boolean startsWith(final AbbreviatedObjectId abbr) {
262 return abbr.prefixCompare(this) == 0;
263 }
264
265 @Override
266 public final int hashCode() {
267 return w2;
268 }
269
270 /**
271 * Determine if this ObjectId has exactly the same value as another.
272 *
273 * @param other
274 * the other id to compare to. May be null.
275 * @return true only if both ObjectIds have identical bits.
276 */
277 public final boolean equals(final AnyObjectId other) {
278 return other != null ? equals(this, other) : false;
279 }
280
281 @Override
282 public final boolean equals(final Object o) {
283 if (o instanceof AnyObjectId)
284 return equals((AnyObjectId) o);
285 else
286 return false;
287 }
288
289 /**
290 * Copy this ObjectId to an output writer in raw binary.
291 *
292 * @param w
293 * the buffer to copy to. Must be in big endian order.
294 */
295 public void copyRawTo(final ByteBuffer w) {
296 w.putInt(w1);
297 w.putInt(w2);
298 w.putInt(w3);
299 w.putInt(w4);
300 w.putInt(w5);
301 }
302
303 /**
304 * Copy this ObjectId to a byte array.
305 *
306 * @param b
307 * the buffer to copy to.
308 * @param o
309 * the offset within b to write at.
310 */
311 public void copyRawTo(final byte[] b, final int o) {
312 NB.encodeInt32(b, o, w1);
313 NB.encodeInt32(b, o + 4, w2);
314 NB.encodeInt32(b, o + 8, w3);
315 NB.encodeInt32(b, o + 12, w4);
316 NB.encodeInt32(b, o + 16, w5);
317 }
318
319 /**
320 * Copy this ObjectId to an int array.
321 *
322 * @param b
323 * the buffer to copy to.
324 * @param o
325 * the offset within b to write at.
326 */
327 public void copyRawTo(final int[] b, final int o) {
328 b[o] = w1;
329 b[o + 1] = w2;
330 b[o + 2] = w3;
331 b[o + 3] = w4;
332 b[o + 4] = w5;
333 }
334
335 /**
336 * Copy this ObjectId to an output writer in raw binary.
337 *
338 * @param w
339 * the stream to write to.
340 * @throws IOException
341 * the stream writing failed.
342 */
343 public void copyRawTo(final OutputStream w) throws IOException {
344 writeRawInt(w, w1);
345 writeRawInt(w, w2);
346 writeRawInt(w, w3);
347 writeRawInt(w, w4);
348 writeRawInt(w, w5);
349 }
350
351 private static void writeRawInt(final OutputStream w, int v)
352 throws IOException {
353 w.write(v >>> 24);
354 w.write(v >>> 16);
355 w.write(v >>> 8);
356 w.write(v);
357 }
358
359 /**
360 * Copy this ObjectId to an output writer in hex format.
361 *
362 * @param w
363 * the stream to copy to.
364 * @throws IOException
365 * the stream writing failed.
366 */
367 public void copyTo(final OutputStream w) throws IOException {
368 w.write(toHexByteArray());
369 }
370
371 /**
372 * Copy this ObjectId to a byte array in hex format.
373 *
374 * @param b
375 * the buffer to copy to.
376 * @param o
377 * the offset within b to write at.
378 */
379 public void copyTo(byte[] b, int o) {
380 formatHexByte(b, o + 0, w1);
381 formatHexByte(b, o + 8, w2);
382 formatHexByte(b, o + 16, w3);
383 formatHexByte(b, o + 24, w4);
384 formatHexByte(b, o + 32, w5);
385 }
386
387 /**
388 * Copy this ObjectId to a ByteBuffer in hex format.
389 *
390 * @param b
391 * the buffer to copy to.
392 */
393 public void copyTo(ByteBuffer b) {
394 b.put(toHexByteArray());
395 }
396
397 private byte[] toHexByteArray() {
398 final byte[] dst = new byte[Constants.OBJECT_ID_STRING_LENGTH];
399 formatHexByte(dst, 0, w1);
400 formatHexByte(dst, 8, w2);
401 formatHexByte(dst, 16, w3);
402 formatHexByte(dst, 24, w4);
403 formatHexByte(dst, 32, w5);
404 return dst;
405 }
406
407 private static final byte[] hexbyte = { '0', '1', '2', '3', '4', '5', '6',
408 '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
409
410 private static void formatHexByte(final byte[] dst, final int p, int w) {
411 int o = p + 7;
412 while (o >= p && w != 0) {
413 dst[o--] = hexbyte[w & 0xf];
414 w >>>= 4;
415 }
416 while (o >= p)
417 dst[o--] = '0';
418 }
419
420 /**
421 * Copy this ObjectId to an output writer in hex format.
422 *
423 * @param w
424 * the stream to copy to.
425 * @throws IOException
426 * the stream writing failed.
427 */
428 public void copyTo(final Writer w) throws IOException {
429 w.write(toHexCharArray());
430 }
431
432 /**
433 * Copy this ObjectId to an output writer in hex format.
434 *
435 * @param tmp
436 * temporary char array to buffer construct into before writing.
437 * Must be at least large enough to hold 2 digits for each byte
438 * of object id (40 characters or larger).
439 * @param w
440 * the stream to copy to.
441 * @throws IOException
442 * the stream writing failed.
443 */
444 public void copyTo(final char[] tmp, final Writer w) throws IOException {
445 toHexCharArray(tmp);
446 w.write(tmp, 0, Constants.OBJECT_ID_STRING_LENGTH);
447 }
448
449 /**
450 * Copy this ObjectId to a StringBuilder in hex format.
451 *
452 * @param tmp
453 * temporary char array to buffer construct into before writing.
454 * Must be at least large enough to hold 2 digits for each byte
455 * of object id (40 characters or larger).
456 * @param w
457 * the string to append onto.
458 */
459 public void copyTo(final char[] tmp, final StringBuilder w) {
460 toHexCharArray(tmp);
461 w.append(tmp, 0, Constants.OBJECT_ID_STRING_LENGTH);
462 }
463
464 private char[] toHexCharArray() {
465 final char[] dst = new char[Constants.OBJECT_ID_STRING_LENGTH];
466 toHexCharArray(dst);
467 return dst;
468 }
469
470 private void toHexCharArray(final char[] dst) {
471 formatHexChar(dst, 0, w1);
472 formatHexChar(dst, 8, w2);
473 formatHexChar(dst, 16, w3);
474 formatHexChar(dst, 24, w4);
475 formatHexChar(dst, 32, w5);
476 }
477
478 private static final char[] hexchar = { '0', '1', '2', '3', '4', '5', '6',
479 '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
480
481 static void formatHexChar(final char[] dst, final int p, int w) {
482 int o = p + 7;
483 while (o >= p && w != 0) {
484 dst[o--] = hexchar[w & 0xf];
485 w >>>= 4;
486 }
487 while (o >= p)
488 dst[o--] = '0';
489 }
490
491 @SuppressWarnings("nls")
492 @Override
493 public String toString() {
494 return "AnyObjectId[" + name() + "]";
495 }
496
497 /**
498 * @return string form of the SHA-1, in lower case hexadecimal.
499 */
500 public final String name() {
501 return new String(toHexCharArray());
502 }
503
504 /**
505 * @return string form of the SHA-1, in lower case hexadecimal.
506 */
507 public final String getName() {
508 return name();
509 }
510
511 /**
512 * Return an abbreviation (prefix) of this object SHA-1.
513 * <p>
514 * This implementation does not guarantee uniqueness. Callers should
515 * instead use {@link ObjectReader#abbreviate(AnyObjectId, int)} to obtain a
516 * unique abbreviation within the scope of a particular object database.
517 *
518 * @param len
519 * length of the abbreviated string.
520 * @return SHA-1 abbreviation.
521 */
522 public AbbreviatedObjectId abbreviate(final int len) {
523 final int a = AbbreviatedObjectId.mask(len, 1, w1);
524 final int b = AbbreviatedObjectId.mask(len, 2, w2);
525 final int c = AbbreviatedObjectId.mask(len, 3, w3);
526 final int d = AbbreviatedObjectId.mask(len, 4, w4);
527 final int e = AbbreviatedObjectId.mask(len, 5, w5);
528 return new AbbreviatedObjectId(len, a, b, c, d, e);
529 }
530
531 /**
532 * Obtain an immutable copy of this current object name value.
533 * <p>
534 * Only returns <code>this</code> if this instance is an unsubclassed
535 * instance of {@link ObjectId}; otherwise a new instance is returned
536 * holding the same value.
537 * <p>
538 * This method is useful to shed any additional memory that may be tied to
539 * the subclass, yet retain the unique identity of the object id for future
540 * lookups within maps and repositories.
541 *
542 * @return an immutable copy, using the smallest memory footprint possible.
543 */
544 public final ObjectId copy() {
545 if (getClass() == ObjectId.class)
546 return (ObjectId) this;
547 return new ObjectId(this);
548 }
549
550 /**
551 * Obtain an immutable copy of this current object name value.
552 * <p>
553 * See {@link #copy()} if <code>this</code> is a possibly subclassed (but
554 * immutable) identity and the application needs a lightweight identity
555 * <i>only</i> reference.
556 *
557 * @return an immutable copy. May be <code>this</code> if this is already
558 * an immutable instance.
559 */
560 public abstract ObjectId toObjectId();
561 }