content: /*
   * Copyright 1999-2101 Alibaba Group.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package com.alibaba.simpleEL.dialect.ql.parser;
  
  
  public class SymbolTable {
  
      public static final int DEFAULT_TABLE_SIZE = 128;
  
      private final Entry[] buckets;
      private final String[] symbols;
      private final char[][] symbols_char;
  
      private final int indexMask;
  
      public SymbolTable() {
          this(DEFAULT_TABLE_SIZE);
      }
  
      public SymbolTable(int tableSize) {
          this.indexMask = tableSize - 1;
          this.buckets = new Entry[tableSize];
          this.symbols = new String[tableSize];
          this.symbols_char = new char[tableSize][];
      }
  
      /**
       * Adds the specified symbol to the symbol table and returns a reference to
       * the unique symbol. If the symbol already exists, the previous symbol
       * reference is returned instead, in order guarantee that symbol references
       * remain unique.
       * 
       * @param symbol The new symbol.
       */
      public String addSymbol(String symbol) {
          return addSymbol(symbol.toCharArray(), 0, symbol.length(), symbol.hashCode());
      }
  
      public int getIndexMask() {
          return indexMask;
      }
  
      public String addSymbol(char[] buffer, int offset, int len) {
          // search for identical symbol
          int hash = hash(buffer, offset, len);
          return addSymbol(buffer, offset, len, hash);
      }
  
      /**
       * Adds the specified symbol to the symbol table and returns a reference to
       * the unique symbol. If the symbol already exists, the previous symbol
       * reference is returned instead, in order guarantee that symbol references
       * remain unique.
       * 
       * @param buffer The buffer containing the new symbol.
       * @param offset The offset into the buffer of the new symbol.
       * @param len The length of the new symbol in the buffer.
       */
      public String addSymbol(char[] buffer, int offset, int len, int hash) {
  
          // int bucket = indexFor(hash, tableSize);
          final int bucket = hash & indexMask;
  
          String sym = symbols[bucket];
  
          boolean match = true;
  
          if (sym != null) {
              if (sym.length() == len) {
                  char[] characters = symbols_char[bucket];
  
                  for (int i = 0; i < len; i++) {
                      if (buffer[offset + i] != characters[i]) {
                          match = false;
                          break;
                      }
                  }
  
                  if (match) {
                      return sym;
                  }
              } else {
                  match = false;
              }
          }
  
          OUTER: for (Entry entry = buckets[bucket]; entry != null; entry = entry.next) {
              char[] characters = entry.characters;
              if (len == characters.length && hash == entry.hashCode) {
                  for (int i = 0; i < len; i++) {
                      if (buffer[offset + i] != characters[i]) {
                          continue OUTER;
                      }
                  }
                  return entry.symbol;
              }
          }
  
          // add new entry
          Entry entry = new Entry(buffer, offset, len, hash, buckets[bucket]);
          buckets[bucket] = entry;
          if (match) {
              symbols[bucket] = entry.symbol;
              symbols_char[bucket] = entry.characters;
          }
          return entry.symbol;
  
      } // addSymbol(char[],int,int):String
  
      public static final int hash(String symbol) {
          return hash(symbol.toCharArray(), 0, symbol.length());
      }
  
      // same as String.hashCode
      public static final int hash(char[] buffer, int offset, int len) {
          int h = 0;
          int off = offset;
  
          for (int i = 0; i < len; i++) {
              h = 31 * h + buffer[off++];
          }
          return h;
      }
  
      //
      // Classes
      //
  
      /**
       * This class is a symbol table entry. Each entry acts as a node in a linked
       * list.
       */
      protected static final class Entry {
          public final String symbol;
          public final int hashCode;
  
          public final char[] characters;
  
          /** The next entry. */
          public Entry next;
  
          //
          // Constructors
          //
  
          /**
           * Constructs a new entry from the specified symbol information and next
           * entry reference.
           */
          public Entry(char[] ch, int offset, int length, int hash, Entry next) {
              characters = new char[length];
              System.arraycopy(ch, offset, characters, 0, length);
              symbol = new String(characters).intern();
              this.next = next;
              this.hashCode = hash;
          }
  
      } // class Entry
  
  } // class SymbolTable
  