jetty-util/src/main/java/org/eclipse/jetty/util/TreeTrie.java

//
//  ========================================================================
//  Copyright (c) 1995-2017 Mort Bay Consulting Pty. Ltd.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package org.eclipse.jetty.util;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

/* ------------------------------------------------------------ */
/** A Trie String lookup data structure using a tree
 * <p>This implementation is always case insensitive and is optimal for
 * a variable number of fixed strings with few special characters.
 * </p>
 * <p>This Trie is stored in a Tree and is unlimited in capacity</p>
 * 
 * <p>This Trie is not Threadsafe and contains no mutual exclusion 
 * or deliberate memory barriers.  It is intended for an ArrayTrie to be
 * built by a single thread and then used concurrently by multiple threads
 * and not mutated during that access.  If concurrent mutations of the
 * Trie is required external locks need to be applied.
 * </p>
 * 
 * @param <V>
 */
public class TreeTrie<V> extends AbstractTrie<V>
{
    private static final int[] __lookup = 
    { // 0   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F
   /*0*/-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 
   /*1*/-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 
   /*2*/31, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 26, -1, 27, 30, -1,
   /*3*/-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 28, 29, -1, -1, -1, -1,
   /*4*/-1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
   /*5*/15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
   /*6*/-1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
   /*7*/15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
    };
    private static final int INDEX = 32;
    private final TreeTrie<V>[]  _nextIndex;
    private final List<TreeTrie<V>> _nextOther=new ArrayList<>();
    private final char _c;
    private String _key;
    private V _value;

    public TreeTrie()
    {
        super(true);
        _nextIndex = new TreeTrie[INDEX];
        _c=0;
    }
    
    private TreeTrie(char c)
    {
        super(true);
        _nextIndex = new TreeTrie[INDEX];
        this._c=c;
    }

    @Override
    public boolean put(String s, V v)
    {
        TreeTrie<V> t = this;
        int limit = s.length();
        for(int k=0; k < limit; k++)
        {
            char c=s.charAt(k);
            
            int index=c>=0&&c<0x7f?__lookup[c]:-1;
            if (index>=0)
            {
                if (t._nextIndex[index] == null)
                    t._nextIndex[index] = new TreeTrie<V>(c);
                t = t._nextIndex[index];
            }
            else
            {
                TreeTrie<V> n=null;
                for (int i=t._nextOther.size();i-->0;)
                {
                    n=t._nextOther.get(i);
                    if (n._c==c)
                        break;
                    n=null;
                }
                if (n==null)
                {
                    n=new TreeTrie<V>(c);
                    t._nextOther.add(n);
                }
                t=n;
            }
        }
        t._key=v==null?null:s;
        t._value = v;
        return true;
    }

    @Override
    public V get(String s,int offset, int len)
    {
        TreeTrie<V> t = this;
        for(int i=0; i < len; i++)
        {
            char c=s.charAt(offset+i);
            int index=c>=0&&c<0x7f?__lookup[c]:-1;
            if (index>=0)
            {
                if (t._nextIndex[index] == null) 
                    return null;
                t = t._nextIndex[index];
            }
            else
            {
                TreeTrie<V> n=null;
                for (int j=t._nextOther.size();j-->0;)
                {
                    n=t._nextOther.get(j);
                    if (n._c==c)
                        break;
                    n=null;
                }
                if (n==null)
                    return null;
                t=n;
            }
        }
        return t._value;
    }

    @Override
    public V get(ByteBuffer b,int offset,int len)
    {
        TreeTrie<V> t = this;
        for(int i=0; i < len; i++)
        {
            byte c=b.get(offset+i);
            int index=c>=0&&c<0x7f?__lookup[c]:-1;
            if (index>=0)
            {
                if (t._nextIndex[index] == null) 
                    return null;
                t = t._nextIndex[index];
            }
            else
            {
                TreeTrie<V> n=null;
                for (int j=t._nextOther.size();j-->0;)
                {
                    n=t._nextOther.get(j);
                    if (n._c==c)
                        break;
                    n=null;
                }
                if (n==null)
                    return null;
                t=n;
            }
        }
        return t._value;
    }

    @Override
    public V getBest(byte[] b,int offset,int len)
    {
        TreeTrie<V> t = this;
        for(int i=0; i < len; i++)
        {
            byte c=b[offset+i];
            int index=c>=0&&c<0x7f?__lookup[c]:-1;
            if (index>=0)
            {
                if (t._nextIndex[index] == null) 
                    break;
                t = t._nextIndex[index];
            }
            else
            {
                TreeTrie<V> n=null;
                for (int j=t._nextOther.size();j-->0;)
                {
                    n=t._nextOther.get(j);
                    if (n._c==c)
                        break;
                    n=null;
                }
                if (n==null)
                    break;
                t=n;
            }
            
            // Is the next Trie is a match
            if (t._key!=null)
            {
                // Recurse so we can remember this possibility
                V best=t.getBest(b,offset+i+1,len-i-1);
                if (best!=null)
                    return best;
                break;
            }
        }
        return t._value;
    }

    @Override
    public V getBest(String s, int offset, int len)
    {
        // TODO inefficient
        byte[] b=s.substring(offset,offset+len).getBytes(StandardCharsets.ISO_8859_1);
        return getBest(b,0,b.length);
    }
    
    @Override
    public V getBest(ByteBuffer b,int offset,int len)
    {
        if (b.hasArray())
            return getBest(b.array(),b.arrayOffset()+b.position()+offset,len);
        return getBestByteBuffer(b,offset,len);
    }
    
    private V getBestByteBuffer(ByteBuffer b,int offset,int len)
    {
        TreeTrie<V> t = this;
        int pos=b.position()+offset;
        for(int i=0; i < len; i++)
        {
            byte c=b.get(pos++);
            int index=c>=0&&c<0x7f?__lookup[c]:-1;
            if (index>=0)
            {
                if (t._nextIndex[index] == null) 
                    break;
                t = t._nextIndex[index];
            }
            else
            {
                TreeTrie<V> n=null;
                for (int j=t._nextOther.size();j-->0;)
                {
                    n=t._nextOther.get(j);
                    if (n._c==c)
                        break;
                    n=null;
                }
                if (n==null)
                    break;
                t=n;
            }
            
            // Is the next Trie is a match
            if (t._key!=null)
            {
                // Recurse so we can remember this possibility
                V best=t.getBest(b,offset+i+1,len-i-1);
                if (best!=null)
                    return best;
                break;
            }
        }
        return t._value;
    }
    

    @Override
    public String toString()
    {
        StringBuilder buf = new StringBuilder();
        toString(buf,this);
        
        if (buf.length()==0)
            return "{}";
        
        buf.setCharAt(0,'{');
        buf.append('}');
        return buf.toString();
    }

    private static <V> void toString(Appendable out, TreeTrie<V> t)
    {
        if (t != null)
        {
            if (t._value!=null)
            {
                try
                {
                    out.append(',');
                    out.append(t._key);
                    out.append('=');
                    out.append(t._value.toString());
                }
                catch (IOException e)
                {
                    throw new RuntimeException(e);
                }
            }
           
            for(int i=0; i < INDEX; i++)
            {
                if (t._nextIndex[i] != null)
                    toString(out,t._nextIndex[i]);
            }
            for (int i=t._nextOther.size();i-->0;)
                toString(out,t._nextOther.get(i));
        }           
    }

    @Override
    public Set<String> keySet()
    {
        Set<String> keys = new HashSet<>();
        keySet(keys,this);
        return keys;
    }
    
    private static <V> void keySet(Set<String> set, TreeTrie<V> t)
    {
        if (t != null)
        {
            if (t._key!=null)
                set.add(t._key);
           
            for(int i=0; i < INDEX; i++)
            {
                if (t._nextIndex[i] != null)
                    keySet(set,t._nextIndex[i]);
            }
            for (int i=t._nextOther.size();i-->0;)
                keySet(set,t._nextOther.get(i));
        }           
    }
    
    @Override
    public boolean isFull()
    {
        return false;
    }


}