com.signalfx.shaded.jetty.util.ArrayTernaryTrie Maven / Gradle / Ivy
//
// ========================================================================
// Copyright (c) 1995-2022 Mort Bay Consulting Pty Ltd and others.
// ------------------------------------------------------------------------
// 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.
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//
package com.signalfx.shaded.jetty.util;
import java.nio.ByteBuffer;
import java.util.AbstractMap;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
/**
* A Ternary Trie String lookup data structure.
*
* This Trie is of a fixed size and cannot grow (which can be a good thing with regards to DOS when used as a cache).
*
*
* The Trie is stored in 3 arrays:
*
*
* - char[] _tree
- This is semantically 2 dimensional array flattened into a 1 dimensional char array. The second dimension
* is that every 4 sequential elements represents a row of: character; hi index; eq index; low index, used to build a
* ternary trie of key strings.
* - String[] _key
- An array of key values where each element matches a row in the _tree array. A non zero key element
* indicates that the _tree row is a complete key rather than an intermediate character of a longer key.
* - V[] _value
- An array of values corresponding to the _key array
*
* The lookup of a value will iterate through the _tree array matching characters. If the equal tree branch is followed,
* then the _key array is looked up to see if this is a complete match. If a match is found then the _value array is looked up
* to return the matching value.
*
*
* This Trie may be instantiated either as case sensitive or insensitive.
*
* 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.
*
*
* @param the Entry type
*/
public class ArrayTernaryTrie extends AbstractTrie
{
private static int LO = 1;
private static int EQ = 2;
private static int HI = 3;
/**
* The Size of a Trie row is the char, and the low, equal and high
* child pointers
*/
private static final int ROW_SIZE = 4;
/**
* The maximum capacity of the implementation. Over that,
* the 16 bit indexes can overflow and the trie
* cannot find existing entries anymore.
*/
public static final int MAX_CAPACITY = Character.MAX_VALUE - 1;
/**
* The Trie rows in a single array which allows a lookup of row,character
* to the next row in the Trie. This is actually a 2 dimensional
* array that has been flattened to achieve locality of reference.
*/
private final char[] _tree;
/**
* The key (if any) for a Trie row.
* A row may be a leaf, a node or both in the Trie tree.
*/
private final String[] _key;
/**
* The value (if any) for a Trie row.
* A row may be a leaf, a node or both in the Trie tree.
*/
private final V[] _value;
/**
* The number of rows allocated
*/
private char _rows;
/**
* Create a case insensitive Trie of default capacity.
*/
public ArrayTernaryTrie()
{
this(128);
}
/**
* Create a Trie of default capacity
*
* @param insensitive true if the Trie is insensitive to the case of the key.
*/
public ArrayTernaryTrie(boolean insensitive)
{
this(insensitive, 128);
}
/**
* Create a case insensitive Trie
*
* @param capacity The capacity of the Trie, which is in the worst case
* is the total number of characters of all keys stored in the Trie.
* The capacity needed is dependent of the shared prefixes of the keys.
* For example, a capacity of 6 nodes is required to store keys "foo"
* and "bar", but a capacity of only 4 is required to
* store "bar" and "bat".
*/
public ArrayTernaryTrie(int capacity)
{
this(true, capacity);
}
/**
* Create a Trie
*
* @param insensitive true if the Trie is insensitive to the case of the key.
* @param capacity The capacity of the Trie, which is in the worst case
* is the total number of characters of all keys stored in the Trie.
* The capacity needed is dependent of the shared prefixes of the keys.
* For example, a capacity of 6 nodes is required to store keys "foo"
* and "bar", but a capacity of only 4 is required to
* store "bar" and "bat".
*/
public ArrayTernaryTrie(boolean insensitive, int capacity)
{
super(insensitive);
if (capacity > MAX_CAPACITY)
throw new IllegalArgumentException("Capacity " + capacity + " > " + MAX_CAPACITY);
_value = (V[])new Object[capacity + 1];
_tree = new char[(capacity + 1) * ROW_SIZE];
_key = new String[capacity + 1];
}
/**
* Copy Trie and change capacity by a factor
*
* @param trie the trie to copy from
* @param factor the factor to grow the capacity by
*/
public ArrayTernaryTrie(ArrayTernaryTrie trie, double factor)
{
super(trie.isCaseInsensitive());
int capacity = (int)(trie._value.length * factor);
if (capacity > MAX_CAPACITY)
throw new IllegalArgumentException("Capacity " + capacity + " > " + MAX_CAPACITY);
_rows = trie._rows;
_value = Arrays.copyOf(trie._value, capacity);
_tree = Arrays.copyOf(trie._tree, capacity * ROW_SIZE);
_key = Arrays.copyOf(trie._key, capacity);
}
@Override
public void clear()
{
_rows = 0;
Arrays.fill(_value, null);
Arrays.fill(_tree, (char)0);
Arrays.fill(_key, null);
}
@Override
public boolean put(String s, V v)
{
int t = 0;
int limit = s.length();
if (limit > MAX_CAPACITY)
return false;
int last = 0;
for (int k = 0; k < limit; k++)
{
char c = s.charAt(k);
if (isCaseInsensitive() && c < 128)
c = StringUtil.lowercases[c];
while (true)
{
if (_rows == MAX_CAPACITY)
return false;
int row = ROW_SIZE * t;
// Do we need to create the new row?
if (t == _rows)
{
_rows = (char)MathUtils.cappedAdd(_rows, 1, _key.length);
if (_rows == _key.length)
return false;
_tree[row] = c;
}
char n = _tree[row];
int diff = n - c;
if (diff == 0)
t = _tree[last = (row + EQ)];
else if (diff < 0)
t = _tree[last = (row + LO)];
else
t = _tree[last = (row + HI)];
// do we need a new row?
if (t == 0)
{
t = _rows;
_tree[last] = (char)t;
}
if (diff == 0)
break;
}
}
// Do we need to create the new row?
if (t == _rows)
{
if (_rows == _key.length)
return false;
_rows++;
}
// Put the key and value
_key[t] = v == null ? null : s;
_value[t] = v;
return true;
}
@Override
public V get(String s, int offset, int len)
{
int t = 0;
for (int i = 0; i < len; )
{
char c = s.charAt(offset + i++);
if (isCaseInsensitive() && c < 128)
c = StringUtil.lowercases[c];
while (true)
{
int row = ROW_SIZE * t;
char n = _tree[row];
int diff = n - c;
if (diff == 0)
{
t = _tree[row + EQ];
if (t == 0)
return null;
break;
}
t = _tree[row + hilo(diff)];
if (t == 0)
return null;
}
}
return _value[t];
}
@Override
public V get(ByteBuffer b, int offset, int len)
{
int t = 0;
offset += b.position();
for (int i = 0; i < len; )
{
byte c = (byte)(b.get(offset + i++) & 0x7f);
if (isCaseInsensitive())
c = (byte)StringUtil.lowercases[c];
while (true)
{
int row = ROW_SIZE * t;
char n = _tree[row];
int diff = n - c;
if (diff == 0)
{
t = _tree[row + EQ];
if (t == 0)
return null;
break;
}
t = _tree[row + hilo(diff)];
if (t == 0)
return null;
}
}
return _value[t];
}
@Override
public V getBest(String s)
{
return getBest(0, s, 0, s.length());
}
@Override
public V getBest(String s, int offset, int length)
{
return getBest(0, s, offset, length);
}
private V getBest(int t, String s, int offset, int len)
{
int node = t;
int end = offset + len;
loop:
while (offset < end)
{
char c = s.charAt(offset++);
len--;
if (isCaseInsensitive() && c < 128)
c = StringUtil.lowercases[c];
while (true)
{
int row = ROW_SIZE * t;
char n = _tree[row];
int diff = n - c;
if (diff == 0)
{
t = _tree[row + EQ];
if (t == 0)
break loop;
// if this node is a match, recurse to remember
if (_key[t] != null)
{
node = t;
V better = getBest(t, s, offset, len);
if (better != null)
return better;
}
break;
}
t = _tree[row + hilo(diff)];
if (t == 0)
break loop;
}
}
return _value[node];
}
@Override
public V getBest(ByteBuffer b, int offset, int len)
{
if (b.hasArray())
return getBest(0, b.array(), b.arrayOffset() + b.position() + offset, len);
return getBest(0, b, offset, len);
}
@Override
public V getBest(byte[] b, int offset, int len)
{
return getBest(0, b, offset, len);
}
private V getBest(int t, byte[] b, int offset, int len)
{
int node = t;
int end = offset + len;
loop:
while (offset < end)
{
byte c = (byte)(b[offset++] & 0x7f);
len--;
if (isCaseInsensitive())
c = (byte)StringUtil.lowercases[c];
while (true)
{
int row = ROW_SIZE * t;
char n = _tree[row];
int diff = n - c;
if (diff == 0)
{
t = _tree[row + EQ];
if (t == 0)
break loop;
// if this node is a match, recurse to remember
if (_key[t] != null)
{
node = t;
V better = getBest(t, b, offset, len);
if (better != null)
return better;
}
break;
}
t = _tree[row + hilo(diff)];
if (t == 0)
break loop;
}
}
return _value[node];
}
private V getBest(int t, ByteBuffer b, int offset, int len)
{
int node = t;
int o = offset + b.position();
loop:
for (int i = 0; i < len; i++)
{
if (o + i >= b.limit())
return null;
byte c = (byte)(b.get(o + i) & 0x7f);
if (isCaseInsensitive())
c = (byte)StringUtil.lowercases[c];
while (true)
{
int row = ROW_SIZE * t;
char n = _tree[row];
int diff = n - c;
if (diff == 0)
{
t = _tree[row + EQ];
if (t == 0)
break loop;
// if this node is a match, recurse to remember
if (_key[t] != null)
{
node = t;
V best = getBest(t, b, offset + i + 1, len - i - 1);
if (best != null)
return best;
}
break;
}
t = _tree[row + hilo(diff)];
if (t == 0)
break loop;
}
}
return _value[node];
}
@Override
public String toString()
{
StringBuilder buf = new StringBuilder();
for (int r = 0; r < _rows; r++)
{
if (_key[r] != null && _value[r] != null)
{
buf.append(',');
buf.append(_key[r]);
buf.append('=');
buf.append(_value[r].toString());
}
}
if (buf.length() == 0)
return "{}";
buf.setCharAt(0, '{');
buf.append('}');
return buf.toString();
}
@Override
public Set keySet()
{
Set keys = new HashSet<>();
for (int r = 0; r < _rows; r++)
{
if (_key[r] != null && _value[r] != null)
keys.add(_key[r]);
}
return keys;
}
public int size()
{
int s = 0;
for (int r = 0; r < _rows; r++)
{
if (_key[r] != null && _value[r] != null)
s++;
}
return s;
}
public boolean isEmpty()
{
for (int r = 0; r < _rows; r++)
{
if (_key[r] != null && _value[r] != null)
return false;
}
return true;
}
public Set> entrySet()
{
Set> entries = new HashSet<>();
for (int r = 0; r < _rows; r++)
{
if (_key[r] != null && _value[r] != null)
entries.add(new AbstractMap.SimpleEntry<>(_key[r], _value[r]));
}
return entries;
}
@Override
public boolean isFull()
{
return _rows == _key.length;
}
public static int hilo(int diff)
{
// branchless equivalent to return ((diff<0)?LO:HI);
// return 3+2*((diff&Integer.MIN_VALUE)>>Integer.SIZE-1);
return 1 + (diff | Integer.MAX_VALUE) / (Integer.MAX_VALUE / 2);
}
public void dump()
{
for (int r = 0; r < _rows; r++)
{
char c = _tree[r * ROW_SIZE + 0];
System.err.printf("%4d [%s,%d,%d,%d] '%s':%s%n",
r,
(c < ' ' || c > 127) ? ("" + (int)c) : "'" + c + "'",
(int)_tree[r * ROW_SIZE + LO],
(int)_tree[r * ROW_SIZE + EQ],
(int)_tree[r * ROW_SIZE + HI],
_key[r],
_value[r]);
}
}
public static class Growing implements Trie
{
private final int _growby;
private ArrayTernaryTrie _trie;
public Growing()
{
this(1024, 1024);
}
public Growing(int capacity, int growby)
{
_growby = growby;
_trie = new ArrayTernaryTrie<>(capacity);
}
public Growing(boolean insensitive, int capacity, int growby)
{
_growby = growby;
_trie = new ArrayTernaryTrie<>(insensitive, capacity);
}
@Override
public boolean put(V v)
{
return put(v.toString(), v);
}
@Override
public int hashCode()
{
return _trie.hashCode();
}
@Override
public V remove(String s)
{
return _trie.remove(s);
}
@Override
public V get(String s)
{
return _trie.get(s);
}
@Override
public V get(ByteBuffer b)
{
return _trie.get(b);
}
@Override
public V getBest(byte[] b, int offset, int len)
{
return _trie.getBest(b, offset, len);
}
@Override
public boolean isCaseInsensitive()
{
return _trie.isCaseInsensitive();
}
@Override
public boolean equals(Object obj)
{
return _trie.equals(obj);
}
@Override
public void clear()
{
_trie.clear();
}
@Override
public boolean put(String s, V v)
{
boolean added = _trie.put(s, v);
while (!added && _growby > 0)
{
int newCapacity = _trie._key.length + _growby;
if (newCapacity > MAX_CAPACITY)
return false;
ArrayTernaryTrie bigger = new ArrayTernaryTrie<>(_trie.isCaseInsensitive(), newCapacity);
for (Map.Entry entry : _trie.entrySet())
{
bigger.put(entry.getKey(), entry.getValue());
}
_trie = bigger;
added = _trie.put(s, v);
}
return added;
}
@Override
public V get(String s, int offset, int len)
{
return _trie.get(s, offset, len);
}
@Override
public V get(ByteBuffer b, int offset, int len)
{
return _trie.get(b, offset, len);
}
@Override
public V getBest(String s)
{
return _trie.getBest(s);
}
@Override
public V getBest(String s, int offset, int length)
{
return _trie.getBest(s, offset, length);
}
@Override
public V getBest(ByteBuffer b, int offset, int len)
{
return _trie.getBest(b, offset, len);
}
@Override
public String toString()
{
return _trie.toString();
}
@Override
public Set keySet()
{
return _trie.keySet();
}
@Override
public boolean isFull()
{
return false;
}
public void dump()
{
_trie.dump();
}
public boolean isEmpty()
{
return _trie.isEmpty();
}
public int size()
{
return _trie.size();
}
}
}