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Library providing immutable/persistent collection classes for
Java. While collections are immutable they provide methods for
adding and removing values by creating new modified copies of
themselves. Each copy shares almost all of its structure with
other copies to minimize memory consumption.
///###////////////////////////////////////////////////////////////////////////
//
// Burton Computer Corporation
// http://www.burton-computer.com
//
// Copyright (c) 2017, Burton Computer Corporation
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//
// Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in
// the documentation and/or other materials provided with the
// distribution.
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// Neither the name of the Burton Computer Corporation nor the names
// of its contributors may be used to endorse or promote products
// derived from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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package org.javimmutable.collections.hash.hamt;
import org.javimmutable.collections.Cursor;
import org.javimmutable.collections.Holder;
import org.javimmutable.collections.Holders;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.SplitableIterator;
import org.javimmutable.collections.common.MutableDelta;
import org.javimmutable.collections.cursors.SingleValueCursor;
import org.javimmutable.collections.hash.collision_map.CollisionMap;
import org.javimmutable.collections.iterators.SingleValueIterator;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import java.util.Iterator;
/**
* HamtNode that stores only one value. Any assign that would progress down the tree
* below this node replaces it with a normal node instead. These exist to shorten the
* height of the overall tree structure when hashCodes are dispersed.
*/
public class HamtLeafNode
implements HamtNode
{
private final int hashCode;
@Nonnull
private final T value;
HamtLeafNode(int hashCode,
@Nonnull T value)
{
this.hashCode = hashCode;
this.value = value;
}
@Override
public Holder find(@Nonnull CollisionMap collisionMap,
int hashCode,
@Nonnull K hashKey)
{
if (hashCode == this.hashCode) {
return collisionMap.findValue(value, hashKey);
} else {
return Holders.of();
}
}
@Override
public V getValueOr(@Nonnull CollisionMap collisionMap,
int hashCode,
@Nonnull K hashKey,
V defaultValue)
{
if (hashCode == this.hashCode) {
return collisionMap.getValueOr(value, hashKey, defaultValue);
} else {
return defaultValue;
}
}
@Nonnull
@Override
public HamtNode assign(@Nonnull CollisionMap collisionMap,
int hashCode,
@Nonnull K hashKey,
@Nullable V value,
@Nonnull MutableDelta sizeDelta)
{
final int thisHashCode = this.hashCode;
final T thisValue = this.value;
if (hashCode == thisHashCode) {
final T newValue = collisionMap.update(thisValue, hashKey, value, sizeDelta);
if (newValue == thisValue) {
return this;
} else {
return new HamtLeafNode<>(hashCode, newValue);
}
} else if (Integer.numberOfLeadingZeros(thisHashCode) < Integer.numberOfLeadingZeros(hashCode)) {
// our path is longer so expand using new value then add our values to tree
final MutableDelta ignored = new MutableDelta();
final Iterator> entries = collisionMap.iterator(thisValue);
HamtNode expanded = HamtBranchNode.forLeafExpansion(hashCode, collisionMap.update(null, hashKey, value, sizeDelta));
while (entries.hasNext()) {
JImmutableMap.Entry entry = entries.next();
expanded = expanded.assign(collisionMap, thisHashCode, entry.getKey(), entry.getValue(), ignored);
}
return expanded;
} else {
// our path is shorter so expand using our hashcode then add new value to tree
final HamtNode expanded = HamtBranchNode.forLeafExpansion(thisHashCode, thisValue);
return expanded.assign(collisionMap, hashCode, hashKey, value, sizeDelta);
}
}
@Nonnull
@Override
public HamtNode delete(@Nonnull CollisionMap collisionMap,
int hashCode,
@Nonnull K hashKey,
@Nonnull MutableDelta sizeDelta)
{
final int thisHashCode = this.hashCode;
final T thisValue = this.value;
if (hashCode == this.hashCode) {
final T newValue = collisionMap.delete(thisValue, hashKey, sizeDelta);
if (newValue == thisValue) {
return this;
} else if (newValue == null) {
return HamtEmptyNode.of();
} else {
return new HamtLeafNode<>(hashCode, newValue);
}
} else {
return this;
}
}
public HamtNode liftNode(int index)
{
return new HamtLeafNode<>(hashCode << HamtBranchNode.SHIFT | index, value);
}
@Override
public boolean isEmpty()
{
return false;
}
@Nonnull
@Override
public SplitableIterator> iterator(CollisionMap collisionMap)
{
return collisionMap.iterator(value);
}
@Nonnull
@Override
public Cursor> cursor(CollisionMap collisionMap)
{
return collisionMap.cursor(value);
}
@Nonnull
@Override
public SplitableIterator iterator()
{
return SingleValueIterator.of(value);
}
@Nonnull
@Override
public Cursor cursor()
{
return SingleValueCursor.of(value);
}
}