1 /*
2 * Copyright (C) 2010, 2013 Google Inc.
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.util.ArrayList;
48 import java.util.Collection;
49 import java.util.Collections;
50 import java.util.HashMap;
51 import java.util.List;
52 import java.util.Map;
53
54 /**
55 * Abstraction of name to {@link ObjectId} mapping.
56 * <p>
57 * A reference database stores a mapping of reference names to {@link ObjectId}.
58 * Every {@link Repository} has a single reference database, mapping names to
59 * the tips of the object graph contained by the {@link ObjectDatabase}.
60 */
61 public abstract class RefDatabase {
62 /**
63 * Order of prefixes to search when using non-absolute references.
64 * <p>
65 * The implementation's {@link #getRef(String)} method must take this search
66 * space into consideration when locating a reference by name. The first
67 * entry in the path is always {@code ""}, ensuring that absolute references
68 * are resolved without further mangling.
69 */
70 protected static final String[] SEARCH_PATH = { "", //$NON-NLS-1$
71 Constants.R_REFS, //
72 Constants.R_TAGS, //
73 Constants.R_HEADS, //
74 Constants.R_REMOTES //
75 };
76
77 /**
78 * Maximum number of times a {@link SymbolicRef} can be traversed.
79 * <p>
80 * If the reference is nested deeper than this depth, the implementation
81 * should either fail, or at least claim the reference does not exist.
82 */
83 protected static final int MAX_SYMBOLIC_REF_DEPTH = 5;
84
85 /** Magic value for {@link #getRefs(String)} to return all references. */
86 public static final String ALL = "";//$NON-NLS-1$
87
88 /**
89 * Initialize a new reference database at this location.
90 *
91 * @throws IOException
92 * the database could not be created.
93 */
94 public abstract void create() throws IOException;
95
96 /** Close any resources held by this database. */
97 public abstract void close();
98
99 /**
100 * Determine if a proposed reference name overlaps with an existing one.
101 * <p>
102 * Reference names use '/' as a component separator, and may be stored in a
103 * hierarchical storage such as a directory on the local filesystem.
104 * <p>
105 * If the reference "refs/heads/foo" exists then "refs/heads/foo/bar" must
106 * not exist, as a reference cannot have a value and also be a container for
107 * other references at the same time.
108 * <p>
109 * If the reference "refs/heads/foo/bar" exists than the reference
110 * "refs/heads/foo" cannot exist, for the same reason.
111 *
112 * @param name
113 * proposed name.
114 * @return true if the name overlaps with an existing reference; false if
115 * using this name right now would be safe.
116 * @throws IOException
117 * the database could not be read to check for conflicts.
118 * @see #getConflictingNames(String)
119 */
120 public abstract boolean isNameConflicting(String name) throws IOException;
121
122 /**
123 * Determine if a proposed reference cannot coexist with existing ones. If
124 * the passed name already exists, it's not considered a conflict.
125 *
126 * @param name
127 * proposed name to check for conflicts against
128 * @return a collection of full names of existing refs which would conflict
129 * with the passed ref name; empty collection when there are no
130 * conflicts
131 * @throws IOException
132 * @since 2.3
133 * @see #isNameConflicting(String)
134 */
135 public Collection<String> getConflictingNames(String name)
136 throws IOException {
137 Map<String, Ref> allRefs = getRefs(ALL);
138 // Cannot be nested within an existing reference.
139 int lastSlash = name.lastIndexOf('/');
140 while (0 < lastSlash) {
141 String needle = name.substring(0, lastSlash);
142 if (allRefs.containsKey(needle))
143 return Collections.singletonList(needle);
144 lastSlash = name.lastIndexOf('/', lastSlash - 1);
145 }
146
147 List<String> conflicting = new ArrayList<String>();
148 // Cannot be the container of an existing reference.
149 String prefix = name + '/';
150 for (String existing : allRefs.keySet())
151 if (existing.startsWith(prefix))
152 conflicting.add(existing);
153
154 return conflicting;
155 }
156
157 /**
158 * Create a new update command to create, modify or delete a reference.
159 *
160 * @param name
161 * the name of the reference.
162 * @param detach
163 * if {@code true} and {@code name} is currently a
164 * {@link SymbolicRef}, the update will replace it with an
165 * {@link ObjectIdRef}. Otherwise, the update will recursively
166 * traverse {@link SymbolicRef}s and operate on the leaf
167 * {@link ObjectIdRef}.
168 * @return a new update for the requested name; never null.
169 * @throws IOException
170 * the reference space cannot be accessed.
171 */
172 public abstract RefUpdate newUpdate(String name, boolean detach)
173 throws IOException;
174
175 /**
176 * Create a new update command to rename a reference.
177 *
178 * @param fromName
179 * name of reference to rename from
180 * @param toName
181 * name of reference to rename to
182 * @return an update command that knows how to rename a branch to another.
183 * @throws IOException
184 * the reference space cannot be accessed.
185 */
186 public abstract RefRename newRename(String fromName, String toName)
187 throws IOException;
188
189 /**
190 * Create a new batch update to attempt on this database.
191 * <p>
192 * The default implementation performs a sequential update of each command.
193 *
194 * @return a new batch update object.
195 */
196 public BatchRefUpdate newBatchUpdate() {
197 return new BatchRefUpdate(this);
198 }
199
200 /**
201 * @return if the database performs {@code newBatchUpdate()} as an atomic
202 * transaction.
203 * @since 3.6
204 */
205 public boolean performsAtomicTransactions() {
206 return false;
207 }
208
209 /**
210 * Read a single reference.
211 * <p>
212 * Aside from taking advantage of {@link #SEARCH_PATH}, this method may be
213 * able to more quickly resolve a single reference name than obtaining the
214 * complete namespace by {@code getRefs(ALL).get(name)}.
215 * <p>
216 * To read a specific reference without using @{link #SEARCH_PATH}, see
217 * {@link #exactRef(String)}.
218 *
219 * @param name
220 * the name of the reference. May be a short name which must be
221 * searched for using the standard {@link #SEARCH_PATH}.
222 * @return the reference (if it exists); else {@code null}.
223 * @throws IOException
224 * the reference space cannot be accessed.
225 */
226 public abstract Ref getRef(String name) throws IOException;
227
228 /**
229 * Read a single reference.
230 * <p>
231 * Unlike {@link #getRef}, this method expects an unshortened reference
232 * name and does not search using the standard {@link #SEARCH_PATH}.
233 *
234 * @param name
235 * the unabbreviated name of the reference.
236 * @return the reference (if it exists); else {@code null}.
237 * @throws IOException
238 * the reference space cannot be accessed.
239 * @since 4.1
240 */
241 public Ref exactRef(String name) throws IOException {
242 Ref ref = getRef(name);
243 if (ref == null || !name.equals(ref.getName())) {
244 return null;
245 }
246 return ref;
247 }
248
249 /**
250 * Read the specified references.
251 * <p>
252 * This method expects a list of unshortened reference names and returns
253 * a map from reference names to refs. Any named references that do not
254 * exist will not be included in the returned map.
255 *
256 * @param refs
257 * the unabbreviated names of references to look up.
258 * @return modifiable map describing any refs that exist among the ref
259 * ref names supplied. The map can be an unsorted map.
260 * @throws IOException
261 * the reference space cannot be accessed.
262 * @since 4.1
263 */
264 public Map<String, Ref> exactRef(String... refs) throws IOException {
265 Map<String, Ref> result = new HashMap<>(refs.length);
266 for (String name : refs) {
267 Ref ref = exactRef(name);
268 if (ref != null) {
269 result.put(name, ref);
270 }
271 }
272 return result;
273 }
274
275 /**
276 * Find the first named reference.
277 * <p>
278 * This method expects a list of unshortened reference names and returns
279 * the first that exists.
280 *
281 * @param refs
282 * the unabbreviated names of references to look up.
283 * @return the first named reference that exists (if any); else {@code null}.
284 * @throws IOException
285 * the reference space cannot be accessed.
286 * @since 4.1
287 */
288 public Ref firstExactRef(String... refs) throws IOException {
289 for (String name : refs) {
290 Ref ref = exactRef(name);
291 if (ref != null) {
292 return ref;
293 }
294 }
295 return null;
296 }
297
298 /**
299 * Get a section of the reference namespace.
300 *
301 * @param prefix
302 * prefix to search the namespace with; must end with {@code /}.
303 * If the empty string ({@link #ALL}), obtain a complete snapshot
304 * of all references.
305 * @return modifiable map that is a complete snapshot of the current
306 * reference namespace, with {@code prefix} removed from the start
307 * of each key. The map can be an unsorted map.
308 * @throws IOException
309 * the reference space cannot be accessed.
310 */
311 public abstract Map<String, Ref> getRefs(String prefix) throws IOException;
312
313 /**
314 * Get the additional reference-like entities from the repository.
315 * <p>
316 * The result list includes non-ref items such as MERGE_HEAD and
317 * FETCH_RESULT cast to be refs. The names of these refs are not returned by
318 * <code>getRefs(ALL)</code> but are accepted by {@link #getRef(String)}
319 * and {@link #exactRef(String)}.
320 *
321 * @return a list of additional refs
322 * @throws IOException
323 * the reference space cannot be accessed.
324 */
325 public abstract List<Ref> getAdditionalRefs() throws IOException;
326
327 /**
328 * Peel a possibly unpeeled reference by traversing the annotated tags.
329 * <p>
330 * If the reference cannot be peeled (as it does not refer to an annotated
331 * tag) the peeled id stays null, but {@link Ref#isPeeled()} will be true.
332 * <p>
333 * Implementors should check {@link Ref#isPeeled()} before performing any
334 * additional work effort.
335 *
336 * @param ref
337 * The reference to peel
338 * @return {@code ref} if {@code ref.isPeeled()} is true; otherwise a new
339 * Ref object representing the same data as Ref, but isPeeled() will
340 * be true and getPeeledObjectId() will contain the peeled object
341 * (or null).
342 * @throws IOException
343 * the reference space or object space cannot be accessed.
344 */
345 public abstract Ref peel(Ref ref) throws IOException;
346
347 /**
348 * Triggers a refresh of all internal data structures.
349 * <p>
350 * In case the RefDatabase implementation has internal caches this method
351 * will trigger that all these caches are cleared.
352 * <p>
353 * Implementors should overwrite this method if they use any kind of caches.
354 */
355 public void refresh() {
356 // nothing
357 }
358
359 /**
360 * Try to find the specified name in the ref map using {@link #SEARCH_PATH}.
361 *
362 * @param map
363 * map of refs to search within. Names should be fully qualified,
364 * e.g. "refs/heads/master".
365 * @param name
366 * short name of ref to find, e.g. "master" to find
367 * "refs/heads/master" in map.
368 * @return The first ref matching the name, or null if not found.
369 * @since 3.4
370 */
371 public static Ref findRef(Map<String, Ref> map, String name) {
372 for (String prefix : SEARCH_PATH) {
373 String fullname = prefix + name;
374 Ref ref = map.get(fullname);
375 if (ref != null)
376 return ref;
377 }
378 return null;
379 }
380 }