org.javimmutable.collections.array.SingleBranchTrieNode Maven / Gradle / Ivy

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// Burton Computer Corporation
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package org.javimmutable.collections.array;

import org.javimmutable.collections.Holder;
import org.javimmutable.collections.Holders;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.iterators.GenericIterator;

import javax.annotation.Nullable;
import javax.annotation.concurrent.Immutable;

@Immutable
class SingleBranchTrieNode
    extends TrieNode
{
    private final int shift;
    private final int branchIndex;
    private final TrieNode child;

    private SingleBranchTrieNode(int shift,
                                 int branchIndex,
                                 TrieNode child)
    {
        assert shift >= 0;
        this.shift = shift;
        this.branchIndex = branchIndex;
        this.child = child;
    }

    static  SingleBranchTrieNode forIndex(int shift,
                                                int index,
                                                TrieNode child)
    {
        final int branchIndex = (index >>> shift) & 0x1f;
        return new SingleBranchTrieNode<>(shift, branchIndex, child);
    }

    static  SingleBranchTrieNode forBranchIndex(int shift,
                                                      int branchIndex,
                                                      TrieNode child)
    {
        return new SingleBranchTrieNode<>(shift, branchIndex, child);
    }

    @Override
    public int valueCount()
    {
        return child.valueCount();
    }

    @Override
    public boolean isEmpty()
    {
        return false;
    }

    @Override
    public T getValueOr(int shift,
                        int index,
                        T defaultValue)
    {
        assert this.shift == shift;
        final int branchIndex = (index >>> shift) & 0x1f;
        return (this.branchIndex == branchIndex) ? child.getValueOr(shift - 5, index, defaultValue) : defaultValue;
    }

    @Override
    public Holder find(int shift,
                          int index)
    {
        assert this.shift == shift;
        final int branchIndex = (index >>> shift) & 0x1f;
        return (this.branchIndex == branchIndex) ? child.find(shift - 5, index) : Holders.of();
    }

    @Override
    public TrieNode assign(int shift,
                              int index,
                              T value)
    {
        assert this.shift == shift;
        final int branchIndex = (index >>> shift) & 0x1f;
        if (this.branchIndex == branchIndex) {
            TrieNode newChild = child.assign(shift - 5, index, value);
            return selectNodeForUpdateResult(shift, branchIndex, newChild);
        } else {
            return MultiBranchTrieNode.forBranchIndex(shift, this.branchIndex, child).assign(shift, index, value);
        }
    }

    @Override
    public TrieNode delete(int shift,
                              int index)
    {
        assert this.shift == shift;
        final int branchIndex = (index >>> shift) & 0x1f;
        if (this.branchIndex != branchIndex) {
            return this;
        } else {
            final TrieNode newChild = child.delete(shift - 5, index);
            return selectNodeForDeleteResult(shift, branchIndex, newChild);
        }
    }

    @Override
    public int getShift()
    {
        return shift;
    }

    @Override
    public boolean isLeaf()
    {
        return false;
    }

    @Override
    public TrieNode trimmedToMinimumDepth()
    {
        return (branchIndex == 0) ? child.trimmedToMinimumDepth() : this;
    }

    @Nullable
    @Override
    public GenericIterator.State> iterateOverRange(@Nullable GenericIterator.State> parent,
                                                                                   int offset,
                                                                                   int limit)
    {
        return child.iterateOverRange(parent, offset, limit);
    }

    @Override
    public void checkInvariants()
    {
        if (shift < 0 || shift > ROOT_SHIFT) {
            throw new IllegalStateException("illegal shift value: " + shift);
        }
        if (branchIndex < 0 || branchIndex >= 32) {
            throw new IllegalStateException("illegal branchIndex value: " + branchIndex);
        }
        child.checkInvariants();
    }

    // for tests
    int getBranchIndex()
    {
        return branchIndex;
    }

    // for tests
    TrieNode getChild()
    {
        return child;
    }

    private TrieNode selectNodeForUpdateResult(int shift,
                                                  int branchIndex,
                                                  TrieNode newChild)
    {
        assert newChild.isLeaf() || (newChild.getShift() == (shift - 5));
        return (newChild == child) ? this : new SingleBranchTrieNode<>(shift, branchIndex, newChild);
    }

    private TrieNode selectNodeForDeleteResult(int shift,
                                                  int branchIndex,
                                                  TrieNode newChild)
    {
        if (newChild == child) {
            return this;
        } else if (newChild.isEmpty()) {
            return of();
        } else if (newChild.isLeaf()) {
            return newChild;
        } else {
            assert newChild.getShift() == (shift - 5);
            return new SingleBranchTrieNode<>(shift, branchIndex, newChild);
        }
    }
}