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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.
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//
// 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
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// of its contributors may be used to endorse or promote products
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// 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.array;
import org.javimmutable.collections.Cursor;
import org.javimmutable.collections.Holder;
import org.javimmutable.collections.Holders;
import org.javimmutable.collections.Indexed;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.SplitableIterator;
import org.javimmutable.collections.common.MutableDelta;
import org.javimmutable.collections.cursors.LazyMultiCursor;
import org.javimmutable.collections.indexed.IndexedArray;
import org.javimmutable.collections.iterators.LazyMultiIterator;
import javax.annotation.Nonnull;
import javax.annotation.concurrent.Immutable;
@Immutable
public class MultiBranchTrieNode
extends TrieNode
{
private final int shift;
private final int bitmask;
@Nonnull
private final TrieNode[] entries;
private MultiBranchTrieNode(int shift,
int bitmask,
@Nonnull TrieNode[] entries)
{
assert shift >= 0;
this.shift = shift;
this.bitmask = bitmask;
this.entries = entries;
}
@SuppressWarnings("SameParameterValue")
static MultiBranchTrieNode forTesting(int shift)
{
TrieNode[] entries = allocate(0);
return new MultiBranchTrieNode<>(shift, 0, entries);
}
static MultiBranchTrieNode forIndex(int shift,
int index,
@Nonnull TrieNode child)
{
int branchIndex = ((index >>> shift) & 0x1f);
return forBranchIndex(shift, branchIndex, child);
}
static MultiBranchTrieNode forBranchIndex(int shift,
int branchIndex,
@Nonnull TrieNode child)
{
assert (branchIndex >= 0) && (branchIndex < 32);
TrieNode[] entries = allocate(1);
entries[0] = child;
return new MultiBranchTrieNode<>(shift, 1 << branchIndex, entries);
}
static MultiBranchTrieNode forEntries(int shift,
@Nonnull TrieNode[] entries)
{
final int length = entries.length;
final int bitmask = (length == 32) ? -1 : ((1 << length) - 1);
return new MultiBranchTrieNode<>(shift, bitmask, entries.clone());
}
static MultiBranchTrieNode forSource(int index,
int size,
@Nonnull Indexed source,
int offset)
{
final TrieNode[] entries = allocate(size);
for (int i = 0; i < size; ++i) {
entries[i] = LeafTrieNode.of(index++, source.get(offset++));
}
final int bitmask = (size == 32) ? -1 : ((1 << size) - 1);
return new MultiBranchTrieNode<>(0, bitmask, entries);
}
static MultiBranchTrieNode fullWithout(int shift,
@Nonnull TrieNode[] entries,
int withoutIndex)
{
assert entries.length == 32;
final TrieNode[] newEntries = allocate(31);
System.arraycopy(entries, 0, newEntries, 0, withoutIndex);
System.arraycopy(entries, withoutIndex + 1, newEntries, withoutIndex, 31 - withoutIndex);
final int newMask = ~(1 << withoutIndex);
return new MultiBranchTrieNode<>(shift, newMask, newEntries);
}
@Override
public boolean isEmpty()
{
return entries.length == 0;
}
@Override
public T getValueOr(int shift,
int index,
T defaultValue)
{
assert this.shift == shift;
final int bit = 1 << ((index >>> shift) & 0x1f);
final int bitmask = this.bitmask;
if ((bitmask & bit) == 0) {
return defaultValue;
} else {
final int childIndex = realIndex(bitmask, bit);
return entries[childIndex].getValueOr(shift - 5, index, defaultValue);
}
}
@Override
public Holder find(int shift,
int index)
{
assert this.shift == shift;
final int bit = 1 << ((index >>> shift) & 0x1f);
final int bitmask = this.bitmask;
if ((bitmask & bit) == 0) {
return Holders.of();
} else {
final int childIndex = realIndex(bitmask, bit);
return entries[childIndex].find(shift - 5, index);
}
}
@Override
public TrieNode assign(int shift,
int index,
T value,
MutableDelta sizeDelta)
{
assert this.shift == shift;
final int bit = 1 << ((index >>> shift) & 0x1f);
final int bitmask = this.bitmask;
final int childIndex = realIndex(bitmask, bit);
final TrieNode[] entries = this.entries;
if ((bitmask & bit) == 0) {
final TrieNode newChild = LeafTrieNode.of(index, value);
sizeDelta.add(1);
return selectNodeForInsertResult(shift, bit, bitmask, childIndex, entries, newChild);
} else {
final TrieNode child = entries[childIndex];
final TrieNode newChild = child.assign(shift - 5, index, value, sizeDelta);
return selectNodeForUpdateResult(shift, bitmask, childIndex, entries, child, newChild);
}
}
@Override
public TrieNode delete(int shift,
int index,
MutableDelta sizeDelta)
{
assert this.shift == shift;
final int bit = 1 << ((index >>> shift) & 0x1f);
final int bitmask = this.bitmask;
final TrieNode[] entries = this.entries;
if ((bitmask & bit) == 0) {
return this;
} else {
final int childIndex = realIndex(bitmask, bit);
final TrieNode child = entries[childIndex];
final TrieNode newChild = child.delete(shift - 5, index, sizeDelta);
return selectNodeForDeleteResult(shift, bit, bitmask, entries, childIndex, child, newChild);
}
}
@Override
public int getShift()
{
return shift;
}
@Override
public boolean isLeaf()
{
return false;
}
@Override
public TrieNode trimmedToMinimumDepth()
{
return (bitmask == 1) ? entries[0].trimmedToMinimumDepth() : this;
}
@Nonnull
@Override
public Cursor> cursor()
{
if (shift != ROOT_SHIFT) {
return LazyMultiCursor.cursor(IndexedArray.retained(entries));
} else {
return LazyMultiCursor.cursor(IndexedArray.retained(entriesForSignedOrderIteration()));
}
}
@Nonnull
@Override
public SplitableIterator> iterator()
{
if (shift != ROOT_SHIFT) {
return LazyMultiIterator.iterator(IndexedArray.retained(entries));
} else {
return LazyMultiIterator.iterator(IndexedArray.retained(entriesForSignedOrderIteration()));
}
}
@Override
public void checkInvariants()
{
if (shift < 0 || shift > ROOT_SHIFT) {
throw new IllegalStateException("illegal shift value: " + shift);
}
if (entries.length != Integer.bitCount(bitmask)) {
throw new IllegalStateException("unexpected entries size: expected=" + Integer.bitCount(bitmask) + " actual=" + entries.length);
}
for (TrieNode entry : entries) {
entry.checkInvariants();
}
}
// for use by unit tests
int getBitmask()
{
return bitmask;
}
// for use by unit tests
TrieNode[] getEntries()
{
return entries.clone();
}
private TrieNode selectNodeForUpdateResult(int shift,
int bitmask,
int childIndex,
TrieNode[] entries,
TrieNode child,
TrieNode newChild)
{
if (newChild == child) {
return this;
} else {
assert newChild.isLeaf() || (newChild.getShift() == (shift - 5));
final TrieNode[] newEntries = entries.clone();
newEntries[childIndex] = newChild;
return new MultiBranchTrieNode<>(shift, bitmask, newEntries);
}
}
private TrieNode selectNodeForInsertResult(int shift,
int bit,
int bitmask,
int childIndex,
TrieNode[] entries,
TrieNode newChild)
{
final int oldLength = entries.length;
final TrieNode[] newEntries = allocate(oldLength + 1);
if (bitmask != 0) {
System.arraycopy(entries, 0, newEntries, 0, childIndex);
System.arraycopy(entries, childIndex, newEntries, childIndex + 1, oldLength - childIndex);
}
newEntries[childIndex] = newChild;
if (newEntries.length == 32) {
return new FullBranchTrieNode<>(shift, newEntries);
} else {
return new MultiBranchTrieNode<>(shift, bitmask | bit, newEntries);
}
}
private TrieNode selectNodeForDeleteResult(int shift,
int bit,
int bitmask,
TrieNode[] entries,
int childIndex,
TrieNode child,
TrieNode newChild)
{
if (newChild.isEmpty()) {
switch (entries.length) {
case 1:
return of();
case 2: {
final int newBitmask = bitmask & ~bit;
final int remainingIndex = Integer.numberOfTrailingZeros(newBitmask);
final TrieNode remainingChild = entries[realIndex(bitmask, 1 << remainingIndex)];
if (remainingChild.isLeaf()) {
return remainingChild;
} else {
return SingleBranchTrieNode.forBranchIndex(shift, remainingIndex, remainingChild);
}
}
default: {
final int newLength = entries.length - 1;
final TrieNode[] newArray = allocate(newLength);
System.arraycopy(entries, 0, newArray, 0, childIndex);
System.arraycopy(entries, childIndex + 1, newArray, childIndex, newLength - childIndex);
return new MultiBranchTrieNode<>(shift, bitmask & ~bit, newArray);
}
}
} else {
return selectNodeForUpdateResult(shift, bitmask, childIndex, entries, child, newChild);
}
}
private TrieNode[] entriesForSignedOrderIteration()
{
final TrieNode[] entries = this.entries;
final TrieNode[] nodes = allocate(entries.length);
final int bitmask = this.bitmask;
int offset = 0;
if ((bitmask & 0b0100) != 0) {
nodes[offset++] = entries[realIndex(bitmask, 0b0100)];
}
if ((bitmask & 0b1000) != 0) {
nodes[offset++] = entries[realIndex(bitmask, 0b1000)];
}
if ((bitmask & 0b0001) != 0) {
nodes[offset++] = entries[realIndex(bitmask, 0b0001)];
}
if ((bitmask & 0b0010) != 0) {
nodes[offset++] = entries[realIndex(bitmask, 0b0010)];
}
assert offset == nodes.length;
return nodes;
}
private static int realIndex(int bitmask,
int bit)
{
return Integer.bitCount(bitmask & (bit - 1));
}
@SuppressWarnings("unchecked")
static TrieNode[] allocate(int size)
{
return (TrieNode[])new TrieNode[size];
}
}