org.javimmutable.collections.array.MultiBranchTrieNode Maven / Gradle / Ivy
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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];
}
}
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