/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.jackrabbit.oak.plugins.memory;
import static com.google.common.base.Objects.toStringHelper;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import static org.apache.jackrabbit.oak.plugins.memory.EmptyNodeState.EMPTY_NODE;
import java.io.IOException;
import java.io.InputStream;
import javax.annotation.CheckForNull;
import javax.annotation.Nonnull;
import com.google.common.base.Objects;
import com.google.common.io.ByteStreams;
import org.apache.jackrabbit.oak.api.Blob;
import org.apache.jackrabbit.oak.api.PropertyState;
import org.apache.jackrabbit.oak.api.Type;
import org.apache.jackrabbit.oak.commons.PathUtils;
import org.apache.jackrabbit.oak.spi.state.EqualsDiff;
import org.apache.jackrabbit.oak.spi.state.MoveDetector;
import org.apache.jackrabbit.oak.spi.state.NodeBuilder;
import org.apache.jackrabbit.oak.spi.state.NodeState;
/**
* In-memory node state builder.
* <p>
* A {@code MemoryNodeBuilder} instance tracks uncommitted changes without
* relying on weak references or requiring hard references on the entire
* accessed subtree. It does this by relying on {@code MutableNodeState}
* instances for tracking <em>uncommitted changes</em> and on {@code Head}
* instances for tracking the connectedness of the builder. A builder keeps
* a reference to the parent builder and knows its own name, which is used
* to check for relevant changes in its parent builder and update its state
* accordingly.
* <p>
* A builder is in one of three possible states, which is tracked within
* its {@code Head} instance:
* <dl>
* <dt><em>unconnected</em></dt>
* <dd>
* A child builder with no content changes starts in this state.
* Before each access the unconnected builder checks its parent for
* relevant changes.
* </dd>
* <dt><em>connected</em></dt>
* <dd>
* Once a builder is first modified, it switches to the connected state
* and records all modification in a shared {@code MutableNodeState}
* instance. Before each access the connected builder checks whether its
* parents base state has been reset and if so, resets its own base state
* accordingly.
* </dd>
* <dt><em>root</em></dt>
* <dd>
* Same as the connected state but only the root of the builder hierarchy
* can have this state.
* </dd>
* </dl>
*/
public class MemoryNodeBuilder implements NodeBuilder {
/**
* Parent builder, or {@code null} for a root builder.
*/
private final MemoryNodeBuilder parent;
/**
* Name of this child node within the parent builder,
* or {@code null} for a root builder.
*/
private final String name;
/**
* Root builder, or {@code this} for the root builder itself.
*/
private final MemoryNodeBuilder rootBuilder;
/**
* Internal revision counter for the base state of this builder. The counter
* is incremented in the root builder whenever its base state is reset.
* Each builder instance has its own copy of this revision counter for
* quickly checking whether its base state needs updating.
* @see #reset(org.apache.jackrabbit.oak.spi.state.NodeState)
* @see #base()
*/
private long baseRevision;
/**
* The base state of this builder, possibly non-existent if this builder
* represents a new node that didn't yet exist in the base content tree.
*/
@Nonnull
private NodeState base;
/**
* Head of this builder. Always use {@link #head()} for accessing to
* ensure the connected state is correctly updated.
*/
private Head head;
/**
* Creates a new in-memory child builder.
* @param parent parent builder
* @param name name of this node
*/
protected MemoryNodeBuilder(MemoryNodeBuilder parent, String name) {
this.parent = parent;
this.name = name;
this.rootBuilder = parent.rootBuilder;
this.base = parent.base().getChildNode(name);
this.baseRevision = parent.baseRevision;
this.head = new UnconnectedHead(baseRevision, base);
}
/**
* Creates a new in-memory node state builder rooted at
* and based on the passed {@code base} state.
* @param base base state of the new builder
*/
public MemoryNodeBuilder(@Nonnull NodeState base) {
this.parent = null;
this.name = null;
this.rootBuilder = this;
this.baseRevision = 0;
this.base = checkNotNull(base);
this.head = new RootHead();
}
/**
* Update the head of this builder to reflect the actual connected state.
* @return head of this builder
*/
private Head head() {
Head newHead = head.update();
if (newHead != head) {
head = newHead;
}
return newHead;
}
/**
* @return {@code true} iff this is the root builder
*/
protected final boolean isRoot() {
return this == rootBuilder;
}
/**
* Update the base state of this builder by recursively retrieving it
* from its parent builder.
* @return base state of this builder
*/
@Nonnull
private NodeState base() {
if (rootBuilder.baseRevision != baseRevision) {
base = parent.base().getChildNode(name);
baseRevision = rootBuilder.baseRevision;
}
return base;
}
/**
* Factory method for creating new child state builders. Subclasses may
* override this method to control the behavior of child state builders.
* @return new builder
*/
protected MemoryNodeBuilder createChildBuilder(String name) {
return new MemoryNodeBuilder(this, name);
}
/**
* Called whenever <em>this</em> node is modified, i.e. a property is
* added, changed or removed, or a child node is added or removed. Changes
* inside child nodes or the subtrees below are not reported. The default
* implementation triggers an {@link #updated()} call on the root builder
* (unless this is already the root builder), which subclasses can use
* to capture aggregate update information across the whole tree.
*/
protected void updated() {
if (this != rootBuilder) {
rootBuilder.updated();
}
}
/**
* Accessor for parent builder
*/
protected final MemoryNodeBuilder getParent() {
return parent;
}
/**
* Accessor for name
*/
protected final String getName() {
return name;
}
/**
* Throws away all changes in this builder and resets the base to the
* given node state.
*
* @param newBase new base state
*/
public void reset(@Nonnull NodeState newBase) {
checkState(parent == null);
base = checkNotNull(newBase);
baseRevision = rootHead().setState(newBase) + 1;
}
/**
* Replaces the current state of this builder with the given node state.
* The base state remains unchanged.
*
* @param newHead new head state
*/
protected void set(NodeState newHead) {
checkState(parent == null);
// updating the base revision forces all sub-builders to refresh
baseRevision = rootHead().setState(newHead);
}
//--------------------------------------------------------< NodeBuilder >---
@Override @Nonnull
public NodeState getNodeState() {
return head().getImmutableNodeState();
}
@Override @Nonnull
public NodeState getBaseState() {
return base();
}
@Override
public boolean exists() {
return head().getCurrentNodeState().exists();
}
@Override
public boolean isNew() {
return exists() && !getBaseState().exists();
}
@Override
public boolean isNew(String name) {
return hasProperty(name) && !getBaseState().hasProperty(name);
}
@Override
public boolean isModified() {
return head().isModified();
}
@Override
public boolean isReplaced() {
return head().isReplaced();
}
@Override
public boolean isReplaced(String name) {
return head().isReplaced(name);
}
@Override
public long getChildNodeCount(long max) {
return head().getCurrentNodeState().getChildNodeCount(max);
}
@Override
public Iterable<String> getChildNodeNames() {
return head().getCurrentNodeState().getChildNodeNames();
}
@Override
public boolean hasChildNode(String name) {
return head().getCurrentNodeState().hasChildNode(checkNotNull(name));
}
@Override
public NodeBuilder child(String name) {
if (hasChildNode(name)) {
return getChildNode(name);
} else {
return setChildNode(name);
}
}
@Override
public NodeBuilder getChildNode(String name) {
return createChildBuilder(checkNotNull(name));
}
@Override
public NodeBuilder setChildNode(String name) {
return setChildNode(checkNotNull(name), EMPTY_NODE);
}
@Override
public NodeBuilder setChildNode(String name, NodeState state) {
checkState(exists(), "This builder does not exist: " + this.name);
head().getMutableNodeState().setChildNode(checkNotNull(name), checkNotNull(state));
MemoryNodeBuilder builder = createChildBuilder(name);
updated();
return builder;
}
@Override
public boolean remove() {
if (!isRoot() && exists()) {
head().getMutableNodeState(); // Make sure the removed node is connected
parent.head().getMutableNodeState().removeChildNode(name);
updated();
return true;
} else {
return false;
}
}
/**
* This implementation has the same semantics as adding this node
* with name {@code newName} as a new child of {@code newParent} followed
* by removing this node. As a consequence this implementation allows
* moving this node into the subtree rooted here, the result of which
* is the same as removing this node.
* <p>
* See also {@link NodeBuilder#moveTo(NodeBuilder, String) the general contract}
* for {@code MoveTo}.
*
* @param newParent builder for the new parent.
* @param newName name of this child at the new parent
* @return {@code true} on success, {@code false} otherwise
*/
@Override
public boolean moveTo(NodeBuilder newParent, String newName) {
checkNotNull(newParent);
checkNotNull(newName);
if (isRoot() || !exists() || newParent.hasChildNode(newName)) {
return false;
} else {
if (newParent.exists()) {
annotateSourcePath();
NodeState nodeState = getNodeState();
newParent.setChildNode(newName, nodeState);
remove();
return true;
} else {
return false;
}
}
}
/**
* Annotate this builder with its source path if this builder has not
* been transiently added. The source path is written to a property with
* the name {@link MoveDetector#SOURCE_PATH}.
* <p>
* The source path of a builder is its current path if its current
* source path annotation is empty and none of its parents has a source
* path annotation set. Otherwise it is the source path of the first parent
* (or self) that has its source path annotation set appended with the relative
* path from that parent to this builder.
* <p>
* This builder has been transiently added when there exists no
* base node at its source path.
*/
protected final void annotateSourcePath() {
String sourcePath = getSourcePath();
if (!isTransientlyAdded(sourcePath)) {
setProperty(MoveDetector.SOURCE_PATH, sourcePath);
}
}
private final String getSourcePath() {
// Traverse up the hierarchy until we encounter the first builder
// having a source path annotation or until we hit the root
MemoryNodeBuilder builder = this;
String sourcePath = getSourcePathAnnotation(builder);
while (sourcePath == null && builder.parent != null) {
builder = builder.parent;
sourcePath = getSourcePathAnnotation(builder);
}
if (sourcePath == null) {
// Neither self nor any parent has a source path annotation. The source
// path is just the path of this builder
return getPath();
} else {
// The source path is the source path of the first parent having a source
// path annotation with the relative path from this builder up to that
// parent appended.
return PathUtils.concat(sourcePath,
PathUtils.relativize(builder.getPath(), getPath()));
}
}
private static String getSourcePathAnnotation(MemoryNodeBuilder builder) {
PropertyState base = builder.getBaseState().getProperty(MoveDetector.SOURCE_PATH);
PropertyState head = builder.getNodeState().getProperty(MoveDetector.SOURCE_PATH);
if (Objects.equal(base, head)) {
// Both null: no source path annotation
// Both non null but equals: source path annotation is from a previous commit
return null;
} else {
return head.getValue(Type.STRING);
}
}
private boolean isTransientlyAdded(String path) {
NodeState node = rootBuilder.getBaseState();
for (String name : PathUtils.elements(path)) {
node = node.getChildNode(name);
}
return !node.exists();
}
@Override
public boolean copyTo(NodeBuilder newParent, String newName) {
if (isRoot()) {
return false;
} else {
checkNotNull(newParent).setChildNode(checkNotNull(newName), getNodeState());
return true;
}
}
@Override
public long getPropertyCount() {
return head().getCurrentNodeState().getPropertyCount();
}
@Override
public Iterable<? extends PropertyState> getProperties() {
return head().getCurrentNodeState().getProperties();
}
@Override
public boolean hasProperty(String name) {
return head().getCurrentNodeState().hasProperty(checkNotNull(name));
}
@Override
public PropertyState getProperty(String name) {
return head().getCurrentNodeState().getProperty(checkNotNull(name));
}
@Override
public boolean getBoolean(String name) {
return head().getCurrentNodeState().getBoolean(checkNotNull(name));
}
@Override @CheckForNull
public String getString(@Nonnull String name) {
return head().getCurrentNodeState().getString(checkNotNull(name));
}
@Override @CheckForNull
public String getName(@Nonnull String name) {
return head().getCurrentNodeState().getName(checkNotNull(name));
}
@Override @Nonnull
public Iterable<String> getNames(@Nonnull String name) {
return head().getCurrentNodeState().getNames(checkNotNull(name));
}
@Override
public NodeBuilder setProperty(PropertyState property) {
checkState(exists(), "This builder does not exist: " + name);
head().getMutableNodeState().setProperty(checkNotNull(property));
updated();
return this;
}
@Override
public <T> NodeBuilder setProperty(String name, T value) {
setProperty(PropertyStates.createProperty(name, value));
return this;
}
@Override
public <T> NodeBuilder setProperty(String name, T value, Type<T> type) {
setProperty(PropertyStates.createProperty(name, value, type));
return this;
}
@Override
public NodeBuilder removeProperty(String name) {
checkState(exists(), "This builder does not exist: " + name);
if (head().getMutableNodeState().removeProperty(checkNotNull(name))) {
updated();
}
return this;
}
@Override
public Blob createBlob(InputStream stream) throws IOException {
try {
return new ArrayBasedBlob(ByteStreams.toByteArray(stream));
} finally {
stream.close();
}
}
/**
* @return path of this builder.
*/
public final String getPath() {
return parent == null ? "/" : getPath(new StringBuilder()).toString();
}
private RootHead rootHead() {
return (RootHead) rootBuilder.head;
}
private StringBuilder getPath(StringBuilder parentPath) {
return parent == null ? parentPath : parent.getPath(parentPath).append('/').append(name);
}
@Override
public String toString() {
return toStringHelper(this).add("path", getPath()).toString();
}
//------------------------------------------------------------< Head >---
/**
* Subclasses of this base class represent the different states associated
* builders can have: <em>unconnected</em>, <em>connected</em>, and <em>root</em>.
* Its methods provide access to the node state being built by this builder.
*/
private abstract static class Head {
/**
* Returns the up-to-date head of the associated builder. In most
* cases the returned value will be the current head instance, but
* a different head can be returned if a state transition is needed.
* The returned value is then used as the new current head of the
* builder.
*
* @return up-to-date head of the associated builder
*/
public abstract Head update();
/**
* Returns the current node state associated with this head. This state
* is only stable across one method call and must not be passed outside
* the {@code NodeBuilder} API boundary.
* @return current head state.
*/
public abstract NodeState getCurrentNodeState();
/**
* Connects the builder to which this head belongs and all its parents
* and return the mutable node state associated with this head. This state
* is only stable across one method call and must not be passed outside
* the {@code NodeBuilder} API boundary.
* @return current head state.
*/
public abstract MutableNodeState getMutableNodeState();
/**
* Returns the current nodes state associated with this head.
* @return current head state.
*/
public abstract NodeState getImmutableNodeState();
/**
* Check whether the associated builder represents a modified node, which has
* either modified properties or removed or added child nodes.
* @return {@code true} for a modified node
*/
public abstract boolean isModified();
/**
* Check whether the associated builder represents a node that
* used to exist but was replaced with other content.
*
* @return {@code true} for a replaced node
*/
public abstract boolean isReplaced();
/**
* Check whether the named property is replaced.
*
* @param name property name
* @return {@code true} for a replaced property
*/
public abstract boolean isReplaced(String name);
}
private class UnconnectedHead extends Head {
private long revision;
private NodeState state;
UnconnectedHead(long revision, NodeState state) {
this.revision = revision;
this.state = state;
}
@Override
public Head update() {
long rootRevision = rootHead().revision;
if (revision != rootRevision) {
// root revision changed: recursively re-get state from parent
NodeState parentState = parent.head().getCurrentNodeState();
NodeState newState = parentState.getChildNode(name);
if (newState instanceof MutableNodeState) {
// transition state to ConnectedHead
return new ConnectedHead((MutableNodeState) newState);
} else {
// update to match the latest revision
state = newState;
revision = rootRevision;
}
}
return this;
}
@Override
public NodeState getCurrentNodeState() {
return state;
}
@Override
public MutableNodeState getMutableNodeState() {
// switch to connected state recursively up to the parent
MutableNodeState parentState = parent.head().getMutableNodeState();
MutableNodeState state = parentState.getMutableChildNode(name);
// triggers a head state transition at next access
return new ConnectedHead(state).getMutableNodeState();
}
@Override
public NodeState getImmutableNodeState() {
assert !(state instanceof MutableNodeState);
return state;
}
@Override
public boolean isModified() {
return EqualsDiff.modified(base(), state);
}
@Override
public boolean isReplaced() {
return false;
}
@Override
public boolean isReplaced(String name) {
return false;
}
@Override
public String toString() {
return toStringHelper(this).add("path", getPath()).toString();
}
}
private class ConnectedHead extends Head {
protected long revision = rootBuilder.baseRevision;
protected MutableNodeState state;
public ConnectedHead(MutableNodeState state) {
this.state = state;
}
@Override
public Head update() {
if (revision != rootBuilder.baseRevision) {
// the root builder's base state has been reset: transition back
// to unconnected and connect again if necessary.
// No need to pass base() instead of base as the subsequent
// call to update will take care of updating to the latest state.
return new UnconnectedHead(baseRevision, base).update();
} else {
return this;
}
}
@Override
public NodeState getCurrentNodeState() {
return state;
}
@Override
public MutableNodeState getMutableNodeState() {
// incrementing the root revision triggers unconnected
// child state to re-get their state on next access
rootHead().revision++;
return state;
}
@Override
public NodeState getImmutableNodeState() {
return state.snapshot();
}
@Override
public boolean isModified() {
return state.isModified(base());
}
@Override
public boolean isReplaced() {
return state.isReplaced(base());
}
@Override
public boolean isReplaced(String name) {
return state.isReplaced(base(), name);
}
@Override
public String toString() {
return toStringHelper(this).add("path", getPath()).toString();
}
}
private class RootHead extends ConnectedHead {
public RootHead() {
// Base of root is always up to date. No need to call base()
super(new MutableNodeState(base));
}
@Override
public Head update() {
return this;
}
public final long setState(NodeState state) {
this.state = new MutableNodeState(state);
// To be able to make a distinction between set() and reset(), we
revision++; // increment the revision twice and
return revision++; // return the intermediate value
}
}
}