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https://github.com/alibaba/druid.git
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remove SymbolTable
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wenshao
@@ -1,198 +0,0 @@
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/*
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* Copyright 1999-2011 Alibaba Group Holding Ltd.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.alibaba.druid.sql.parser;
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/**
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* @author wenshao<szujobs@hotmail.com>
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*/
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public class SymbolTable {
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//
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// Constants
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//
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/** Default table size. */
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public static final int DEFAULT_TABLE_SIZE = 128;
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public static final int MAX_SIZE = 1024;
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/** Buckets. */
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private final Entry[] buckets;
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private final String[] symbols;
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private final char[][] symbolsChar;
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// actual table size
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private final int indexMask;
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private int size = 0;
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//
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// Constructors
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//
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/** Constructs a symbol table with a default number of buckets. */
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public SymbolTable(){
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this(DEFAULT_TABLE_SIZE);
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}
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/** Constructs a symbol table with a specified number of buckets. */
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public SymbolTable(int tableSize){
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this.indexMask = tableSize - 1;
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this.buckets = new Entry[tableSize];
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this.symbols = new String[tableSize];
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this.symbolsChar = new char[tableSize][];
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}
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//
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// Public methods
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//
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/**
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* Adds the specified symbol to the symbol table and returns a reference to the unique symbol. If the symbol already
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* exists, the previous symbol reference is returned instead, in order guarantee that symbol references remain
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* unique.
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*
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* @param symbol The new symbol.
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*/
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public String addSymbol(String symbol) {
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return addSymbol(symbol.toCharArray(), 0, symbol.length(), symbol.hashCode());
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}
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public int getIndexMask() {
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return indexMask;
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}
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public String addSymbol(char[] buffer, int offset, int len) {
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// search for identical symbol
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int hash = hash(buffer, offset, len);
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return addSymbol(buffer, offset, len, hash);
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}
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/**
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* Adds the specified symbol to the symbol table and returns a reference to the unique symbol. If the symbol already
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* exists, the previous symbol reference is returned instead, in order guarantee that symbol references remain
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* unique.
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*
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* @param buffer The buffer containing the new symbol.
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* @param offset The offset into the buffer of the new symbol.
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* @param len The length of the new symbol in the buffer.
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*/
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public String addSymbol(char[] buffer, int offset, int len, int hash) {
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// int bucket = indexFor(hash, tableSize);
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final int bucket = hash & indexMask;
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String sym = symbols[bucket];
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boolean match = true;
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if (sym != null) {
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if (sym.length() == len) {
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char[] characters = symbolsChar[bucket];
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for (int i = 0; i < len; i++) {
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if (buffer[offset + i] != characters[i]) {
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match = false;
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break;
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}
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}
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if (match) {
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return sym;
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}
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} else {
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match = false;
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}
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}
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OUTER: for (Entry entry = buckets[bucket]; entry != null; entry = entry.next) {
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char[] characters = entry.characters;
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if (len == characters.length && hash == entry.hashCode) {
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for (int i = 0; i < len; i++) {
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if (buffer[offset + i] != characters[i]) {
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continue OUTER;
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}
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}
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return entry.symbol;
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}
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}
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if (size >= MAX_SIZE) {
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return new String(buffer, offset, len);
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}
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// add new entry
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Entry entry = new Entry(buffer, offset, len, hash, buckets[bucket]);
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buckets[bucket] = entry;
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if (match) {
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symbols[bucket] = entry.symbol;
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symbolsChar[bucket] = entry.characters;
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}
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size++;
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return entry.symbol;
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} // addSymbol(char[],int,int):String
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public static final int hash(String symbol) {
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return hash(symbol.toCharArray(), 0, symbol.length());
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}
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// same as String.hashCode
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public static final int hash(char[] buffer, int offset, int len) {
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int h = 0;
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int off = offset;
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for (int i = 0; i < len; i++) {
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h = 31 * h + buffer[off++];
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}
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return h;
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}
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//
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// Classes
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//
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/**
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* This class is a symbol table entry. Each entry acts as a node in a linked list.
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*/
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protected static final class Entry {
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public final String symbol;
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public final int hashCode;
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public final char[] characters;
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/** The next entry. */
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public Entry next;
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//
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// Constructors
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//
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/**
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* Constructs a new entry from the specified symbol information and next entry reference.
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*/
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public Entry(char[] ch, int offset, int length, int hash, Entry next){
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characters = new char[length];
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System.arraycopy(ch, offset, characters, 0, length);
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symbol = new String(characters).intern();
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this.next = next;
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this.hashCode = hash;
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}
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} // class Entry
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} // class SymbolTable
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