RefDatabase.java
/*
* Copyright (C) 2010, 2013 Google Inc. and others
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0 which is available at
* https://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.eclipse.jgit.lib;
import static java.util.stream.Collectors.toList;
import static java.util.stream.Collectors.toSet;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import org.eclipse.jgit.annotations.NonNull;
import org.eclipse.jgit.annotations.Nullable;
/**
* Abstraction of name to {@link org.eclipse.jgit.lib.ObjectId} mapping.
* <p>
* A reference database stores a mapping of reference names to
* {@link org.eclipse.jgit.lib.ObjectId}. Every
* {@link org.eclipse.jgit.lib.Repository} has a single reference database,
* mapping names to the tips of the object graph contained by the
* {@link org.eclipse.jgit.lib.ObjectDatabase}.
*/
public abstract class RefDatabase {
/**
* Order of prefixes to search when using non-absolute references.
* <p>
* {@link #findRef(String)} takes this search space into consideration
* when locating a reference by name. The first entry in the path is
* always {@code ""}, ensuring that absolute references are resolved
* without further mangling.
*/
protected static final String[] SEARCH_PATH = { "", //$NON-NLS-1$
Constants.R_REFS, //
Constants.R_TAGS, //
Constants.R_HEADS, //
Constants.R_REMOTES //
};
/**
* Maximum number of times a {@link SymbolicRef} can be traversed.
* <p>
* If the reference is nested deeper than this depth, the implementation
* should either fail, or at least claim the reference does not exist.
*
* @since 4.2
*/
public static final int MAX_SYMBOLIC_REF_DEPTH = 5;
/**
* Magic value for {@link #getRefsByPrefix(String)} to return all
* references.
*/
public static final String ALL = "";//$NON-NLS-1$
/**
* Initialize a new reference database at this location.
*
* @throws java.io.IOException
* the database could not be created.
*/
public abstract void create() throws IOException;
/**
* Close any resources held by this database.
*/
public abstract void close();
/**
* With versioning, each reference has a version number that increases on
* update. See {@link Ref#getUpdateIndex()}.
*
* @implSpec This method returns false by default. Implementations
* supporting versioning must override it to return true.
* @return true if the implementation assigns update indices to references.
* @since 5.3
*/
public boolean hasVersioning() {
return false;
}
/**
* Determine if a proposed reference name overlaps with an existing one.
* <p>
* Reference names use '/' as a component separator, and may be stored in a
* hierarchical storage such as a directory on the local filesystem.
* <p>
* If the reference "refs/heads/foo" exists then "refs/heads/foo/bar" must
* not exist, as a reference cannot have a value and also be a container for
* other references at the same time.
* <p>
* If the reference "refs/heads/foo/bar" exists than the reference
* "refs/heads/foo" cannot exist, for the same reason.
*
* @param name
* proposed name.
* @return true if the name overlaps with an existing reference; false if
* using this name right now would be safe.
* @throws java.io.IOException
* the database could not be read to check for conflicts.
* @see #getConflictingNames(String)
*/
public abstract boolean isNameConflicting(String name) throws IOException;
/**
* Determine if a proposed reference cannot coexist with existing ones. If
* the passed name already exists, it's not considered a conflict.
*
* @param name
* proposed name to check for conflicts against
* @return a collection of full names of existing refs which would conflict
* with the passed ref name; empty collection when there are no
* conflicts
* @throws java.io.IOException
* @since 2.3
* @see #isNameConflicting(String)
*/
@NonNull
public Collection<String> getConflictingNames(String name)
throws IOException {
Map<String, Ref> allRefs = getRefs(ALL);
// Cannot be nested within an existing reference.
int lastSlash = name.lastIndexOf('/');
while (0 < lastSlash) {
String needle = name.substring(0, lastSlash);
if (allRefs.containsKey(needle))
return Collections.singletonList(needle);
lastSlash = name.lastIndexOf('/', lastSlash - 1);
}
List<String> conflicting = new ArrayList<>();
// Cannot be the container of an existing reference.
String prefix = name + '/';
for (String existing : allRefs.keySet())
if (existing.startsWith(prefix))
conflicting.add(existing);
return conflicting;
}
/**
* Create a new update command to create, modify or delete a reference.
*
* @param name
* the name of the reference.
* @param detach
* if {@code true} and {@code name} is currently a
* {@link org.eclipse.jgit.lib.SymbolicRef}, the update will
* replace it with an {@link org.eclipse.jgit.lib.ObjectIdRef}.
* Otherwise, the update will recursively traverse
* {@link org.eclipse.jgit.lib.SymbolicRef}s and operate on the
* leaf {@link org.eclipse.jgit.lib.ObjectIdRef}.
* @return a new update for the requested name; never null.
* @throws java.io.IOException
* the reference space cannot be accessed.
*/
@NonNull
public abstract RefUpdate newUpdate(String name, boolean detach)
throws IOException;
/**
* Create a new update command to rename a reference.
*
* @param fromName
* name of reference to rename from
* @param toName
* name of reference to rename to
* @return an update command that knows how to rename a branch to another.
* @throws java.io.IOException
* the reference space cannot be accessed.
*/
@NonNull
public abstract RefRename newRename(String fromName, String toName)
throws IOException;
/**
* Create a new batch update to attempt on this database.
* <p>
* The default implementation performs a sequential update of each command.
*
* @return a new batch update object.
*/
@NonNull
public BatchRefUpdate newBatchUpdate() {
return new BatchRefUpdate(this);
}
/**
* Whether the database is capable of performing batch updates as atomic
* transactions.
* <p>
* If true, by default {@link org.eclipse.jgit.lib.BatchRefUpdate} instances
* will perform updates atomically, meaning either all updates will succeed,
* or all updates will fail. It is still possible to turn off this behavior
* on a per-batch basis by calling {@code update.setAtomic(false)}.
* <p>
* If false, {@link org.eclipse.jgit.lib.BatchRefUpdate} instances will
* never perform updates atomically, and calling
* {@code update.setAtomic(true)} will cause the entire batch to fail with
* {@code REJECTED_OTHER_REASON}.
* <p>
* This definition of atomicity is stronger than what is provided by
* {@link org.eclipse.jgit.transport.ReceivePack}. {@code ReceivePack} will
* attempt to reject all commands if it knows in advance some commands may
* fail, even if the storage layer does not support atomic transactions.
* Here, atomicity applies even in the case of unforeseeable errors.
*
* @return whether transactions are atomic by default.
* @since 3.6
*/
public boolean performsAtomicTransactions() {
return false;
}
/**
* Compatibility synonym for {@link #findRef(String)}.
*
* @param name
* the name of the reference. May be a short name which must be
* searched for using the standard {@link #SEARCH_PATH}.
* @return the reference (if it exists); else {@code null}.
* @throws IOException
* the reference space cannot be accessed.
* @deprecated Use {@link #findRef(String)} instead.
*/
@Deprecated
@Nullable
public final Ref getRef(String name) throws IOException {
return findRef(name);
}
/**
* Read a single reference.
* <p>
* Aside from taking advantage of {@link #SEARCH_PATH}, this method may be
* able to more quickly resolve a single reference name than obtaining the
* complete namespace by {@code getRefs(ALL).get(name)}.
* <p>
* To read a specific reference without using @{link #SEARCH_PATH}, see
* {@link #exactRef(String)}.
*
* @param name
* the name of the reference. May be a short name which must be
* searched for using the standard {@link #SEARCH_PATH}.
* @return the reference (if it exists); else {@code null}.
* @throws java.io.IOException
* the reference space cannot be accessed.
* @since 5.3
*/
@Nullable
public final Ref findRef(String name) throws IOException {
String[] names = new String[SEARCH_PATH.length];
for (int i = 0; i < SEARCH_PATH.length; i++) {
names[i] = SEARCH_PATH[i] + name;
}
return firstExactRef(names);
}
/**
* Read a single reference.
* <p>
* Unlike {@link #findRef}, this method expects an unshortened reference
* name and does not search using the standard {@link #SEARCH_PATH}.
*
* @param name
* the unabbreviated name of the reference.
* @return the reference (if it exists); else {@code null}.
* @throws java.io.IOException
* the reference space cannot be accessed.
* @since 4.1
*/
@Nullable
public abstract Ref exactRef(String name) throws IOException;
/**
* Read the specified references.
* <p>
* This method expects a list of unshortened reference names and returns
* a map from reference names to refs. Any named references that do not
* exist will not be included in the returned map.
*
* @param refs
* the unabbreviated names of references to look up.
* @return modifiable map describing any refs that exist among the ref
* ref names supplied. The map can be an unsorted map.
* @throws java.io.IOException
* the reference space cannot be accessed.
* @since 4.1
*/
@NonNull
public Map<String, Ref> exactRef(String... refs) throws IOException {
Map<String, Ref> result = new HashMap<>(refs.length);
for (String name : refs) {
Ref ref = exactRef(name);
if (ref != null) {
result.put(name, ref);
}
}
return result;
}
/**
* Find the first named reference.
* <p>
* This method expects a list of unshortened reference names and returns
* the first that exists.
*
* @param refs
* the unabbreviated names of references to look up.
* @return the first named reference that exists (if any); else {@code null}.
* @throws java.io.IOException
* the reference space cannot be accessed.
* @since 4.1
*/
@Nullable
public Ref firstExactRef(String... refs) throws IOException {
for (String name : refs) {
Ref ref = exactRef(name);
if (ref != null) {
return ref;
}
}
return null;
}
/**
* Returns all refs.
* <p>
* This includes {@code HEAD}, branches under {@code ref/heads/}, tags
* under {@code refs/tags/}, etc. It does not include pseudo-refs like
* {@code FETCH_HEAD}; for those, see {@link #getAdditionalRefs}.
* <p>
* Symbolic references to a non-existent ref (for example,
* {@code HEAD} pointing to a branch yet to be born) are not included.
* <p>
* Callers interested in only a portion of the ref hierarchy can call
* {@link #getRefsByPrefix} instead.
*
* @return immutable list of all refs.
* @throws java.io.IOException
* the reference space cannot be accessed.
* @since 5.0
*/
@NonNull
public List<Ref> getRefs() throws IOException {
return getRefsByPrefix(ALL);
}
/**
* Get a section of the reference namespace.
*
* @param prefix
* prefix to search the namespace with; must end with {@code /}.
* If the empty string ({@link #ALL}), obtain a complete snapshot
* of all references.
* @return modifiable map that is a complete snapshot of the current
* reference namespace, with {@code prefix} removed from the start
* of each key. The map can be an unsorted map.
* @throws java.io.IOException
* the reference space cannot be accessed.
* @deprecated use {@link #getRefsByPrefix} instead
*/
@NonNull
@Deprecated
public abstract Map<String, Ref> getRefs(String prefix) throws IOException;
/**
* Returns refs whose names start with a given prefix.
* <p>
* The default implementation uses {@link #getRefs(String)}. Implementors of
* {@link RefDatabase} should override this method directly if a better
* implementation is possible.
*
* @param prefix string that names of refs should start with; may be
* empty (to return all refs).
* @return immutable list of refs whose names start with {@code prefix}.
* @throws java.io.IOException
* the reference space cannot be accessed.
* @since 5.0
*/
@NonNull
public List<Ref> getRefsByPrefix(String prefix) throws IOException {
Map<String, Ref> coarseRefs;
int lastSlash = prefix.lastIndexOf('/');
if (lastSlash == -1) {
coarseRefs = getRefs(ALL);
} else {
coarseRefs = getRefs(prefix.substring(0, lastSlash + 1));
}
List<Ref> result;
if (lastSlash + 1 == prefix.length()) {
result = coarseRefs.values().stream().collect(toList());
} else {
String p = prefix.substring(lastSlash + 1);
result = coarseRefs.entrySet().stream()
.filter(e -> e.getKey().startsWith(p))
.map(e -> e.getValue())
.collect(toList());
}
return Collections.unmodifiableList(result);
}
/**
* Returns refs whose names start with a given prefix excluding all refs that
* start with one of the given prefixes.
*
* <p>
* The default implementation is not efficient. Implementors of {@link RefDatabase}
* should override this method directly if a better implementation is possible.
*
* @param include string that names of refs should start with; may be empty.
* @param excludes strings that names of refs can't start with; may be empty.
* @return immutable list of refs whose names start with {@code prefix} and none
* of the strings in {@code exclude}.
* @throws java.io.IOException the reference space cannot be accessed.
* @since 5.11
*/
@NonNull
public List<Ref> getRefsByPrefixWithExclusions(String include, Set<String> excludes)
throws IOException {
Stream<Ref> refs = getRefs(include).values().stream();
for(String exclude: excludes) {
refs = refs.filter(r -> !r.getName().startsWith(exclude));
}
return Collections.unmodifiableList(refs.collect(Collectors.toList()));
}
/**
* Returns refs whose names start with one of the given prefixes.
* <p>
* The default implementation uses {@link #getRefsByPrefix(String)}.
* Implementors of {@link RefDatabase} should override this method directly
* if a better implementation is possible.
*
* @param prefixes
* strings that names of refs should start with.
* @return immutable list of refs whose names start with one of
* {@code prefixes}. Refs can be unsorted and may contain duplicates
* if the prefixes overlap.
* @throws java.io.IOException
* the reference space cannot be accessed.
* @since 5.2
*/
@NonNull
public List<Ref> getRefsByPrefix(String... prefixes) throws IOException {
List<Ref> result = new ArrayList<>();
for (String prefix : prefixes) {
result.addAll(getRefsByPrefix(prefix));
}
return Collections.unmodifiableList(result);
}
/**
* Returns all refs that resolve directly to the given {@link ObjectId}.
* Includes peeled {@link ObjectId}s. This is the inverse lookup of
* {@link #exactRef(String...)}.
*
* <p>
* The default implementation uses a linear scan. Implementors of
* {@link RefDatabase} should override this method directly if a better
* implementation is possible.
*
* @param id
* {@link ObjectId} to resolve
* @return a {@link Set} of {@link Ref}s whose tips point to the provided
* id.
* @throws java.io.IOException
* the reference space cannot be accessed.
* @since 5.4
*/
@NonNull
public Set<Ref> getTipsWithSha1(ObjectId id) throws IOException {
return getRefs().stream().filter(r -> id.equals(r.getObjectId())
|| id.equals(r.getPeeledObjectId())).collect(toSet());
}
/**
* If the ref database does not support fast inverse queries, it may
* be advantageous to build a complete SHA1 to ref map in advance for
* multiple uses. To let applications decide on this decision,
* this function indicates whether the inverse map is available.
*
* @return whether this RefDatabase supports fast inverse ref queries.
* @throws IOException on I/O problems.
* @since 5.6
*/
public boolean hasFastTipsWithSha1() throws IOException {
return false;
}
/**
* Check if any refs exist in the ref database.
* <p>
* This uses the same definition of refs as {@link #getRefs()}. In
* particular, returns {@code false} in a new repository with no refs
* under {@code refs/} and {@code HEAD} pointing to a branch yet to be
* born, and returns {@code true} in a repository with no refs under
* {@code refs/} and a detached {@code HEAD} pointing to history.
*
* @return true if the database has refs.
* @throws java.io.IOException
* the reference space cannot be accessed.
* @since 5.0
*/
public boolean hasRefs() throws IOException {
return !getRefs().isEmpty();
}
/**
* Get the additional reference-like entities from the repository.
* <p>
* The result list includes non-ref items such as MERGE_HEAD and
* FETCH_RESULT cast to be refs. The names of these refs are not returned by
* <code>getRefs()</code> but are accepted by {@link #findRef(String)}
* and {@link #exactRef(String)}.
*
* @return a list of additional refs
* @throws java.io.IOException
* the reference space cannot be accessed.
*/
@NonNull
public abstract List<Ref> getAdditionalRefs() throws IOException;
/**
* Peel a possibly unpeeled reference by traversing the annotated tags.
* <p>
* If the reference cannot be peeled (as it does not refer to an annotated
* tag) the peeled id stays null, but
* {@link org.eclipse.jgit.lib.Ref#isPeeled()} will be true.
* <p>
* Implementors should check {@link org.eclipse.jgit.lib.Ref#isPeeled()}
* before performing any additional work effort.
*
* @param ref
* The reference to peel
* @return {@code ref} if {@code ref.isPeeled()} is true; otherwise a new
* Ref object representing the same data as Ref, but isPeeled() will
* be true and getPeeledObjectId() will contain the peeled object
* (or {@code null}).
* @throws java.io.IOException
* the reference space or object space cannot be accessed.
*/
@NonNull
public abstract Ref peel(Ref ref) throws IOException;
/**
* Triggers a refresh of all internal data structures.
* <p>
* In case the RefDatabase implementation has internal caches this method
* will trigger that all these caches are cleared.
* <p>
* Implementors should overwrite this method if they use any kind of caches.
*/
public void refresh() {
// nothing
}
/**
* Try to find the specified name in the ref map using {@link #SEARCH_PATH}.
*
* @param map
* map of refs to search within. Names should be fully qualified,
* e.g. "refs/heads/master".
* @param name
* short name of ref to find, e.g. "master" to find
* "refs/heads/master" in map.
* @return The first ref matching the name, or {@code null} if not found.
* @since 3.4
*/
@Nullable
public static Ref findRef(Map<String, Ref> map, String name) {
for (String prefix : SEARCH_PATH) {
String fullname = prefix + name;
Ref ref = map.get(fullname);
if (ref != null)
return ref;
}
return null;
}
}