| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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 org.apache.uima.internal.util; |
| |
| import java.io.BufferedReader; |
| import java.io.File; |
| import java.io.FileReader; |
| import java.io.IOException; |
| import java.util.HashMap; |
| import java.util.Vector; |
| |
| /** |
| * The SymbolTable class provides a generic symbol table. A symbol table is a bijective mapping |
| * between strings and integers. Symbol numbering starts at a point defined by the user, which is 0 |
| * by default. A SymbolTable provides quick access to symbol numbers (code points) through a hash |
| * table. The reverse map is facilitated through a separate vector of the symbols. This is memory |
| * intensive, but much faster than searching through the hashtable. |
| */ |
| public class SymbolTable { |
| |
| // The default starting point |
| private static final int DEFAULT_START = 0; |
| |
| // The actual starting point |
| private int start; |
| |
| private HashMap hashtable; // String -> Integer |
| |
| private Vector symbols; // Vector<String> |
| |
| /** |
| * Use this constructor if you need your symbol numbering to start at a different point than 0. |
| * |
| * @param start |
| * The code point of the first symbol added to the table. Subsequent symbols will have |
| * larger code points. |
| */ |
| public SymbolTable(int start) { |
| this.hashtable = new HashMap(); |
| this.symbols = new Vector(); |
| this.start = start; |
| } |
| |
| /** Default constructor */ |
| public SymbolTable() { |
| this(DEFAULT_START); |
| } |
| |
| /** |
| * Init the symbol table from an array of strings, where code points correspond to array |
| * positions. Warning: if the array contains duplicate strings, the numbering will be off! |
| * |
| * @param names |
| * The String array containing the symbols. |
| */ |
| public SymbolTable(String[] names) { |
| // Start numbering at 0. |
| this(0); |
| for (int i = 0; i < names.length; i++) { |
| this.set(names[i]); |
| } |
| } |
| |
| public boolean contains(String symbol) { |
| return (this.getStart() <= this.get(symbol)); |
| } |
| |
| /** |
| * Get the starting number of the symbol table. |
| * |
| * @return The start of the table. |
| */ |
| public int getStart() { |
| return this.start; |
| } |
| |
| /** |
| * Perform a deep copy. |
| * |
| * @return A copy of <code>this</code>. |
| */ |
| public SymbolTable copy() { |
| SymbolTable copy = new SymbolTable(this.start); |
| int max = this.symbols.size(); |
| for (int i = 0; i < max; i++) { |
| copy.set((String) this.symbols.get(i)); |
| } |
| return copy; |
| } |
| |
| // Utility function to convert from relative addressing (external) |
| // to absolute addressing (internal). |
| private final int rel2abs(int i) { |
| return (i - this.start); |
| } |
| |
| // Utility function to convert from absolute addressing (internal) |
| // to relative addressing (external). |
| private final int abs2rel(int i) { |
| return (i + this.start); |
| } |
| |
| /** |
| * Create new symbol in table. If the symbol already exists, only the symbol's number is returned. |
| * Use get() if you need to find out if the symbol is already in the table. |
| * |
| * @param symbol |
| * the input string to be put in the table. |
| * @return the symbol's number. |
| */ |
| public int set(String symbol) { |
| if (this.hashtable.containsKey(symbol)) { |
| return ((Integer) this.hashtable.get(symbol)).intValue(); |
| } |
| int rel; |
| int abs; |
| synchronized (this) { // synchronize write access to internal data |
| // structures |
| abs = this.hashtable.size(); |
| rel = abs2rel(abs); |
| // System.out.println("Adding symbol " + symbol + " at pos: " + i); |
| this.hashtable.put(symbol, new Integer(rel)); |
| this.symbols.insertElementAt(symbol, abs); |
| } |
| return rel; |
| } |
| |
| /** |
| * Get value of symbol in table. |
| * |
| * @param symbol |
| * the input string. |
| * @return the symbol's number, if the symbol is in the table, and <code>start-1</code>, else |
| * (where <code>start</code> is the code point of the first symbol). |
| */ |
| public int get(String symbol) { |
| if (this.hashtable.containsKey(symbol)) { |
| return ((Integer) this.hashtable.get(symbol)).intValue(); |
| } |
| return (this.start - 1); |
| } |
| |
| /** |
| * Find the symbol corresponding to a value. |
| * |
| * @param i |
| * the number that we want to get the string value for. |
| * @return the symbol corresponding to the input number, if it exists, and null, else. |
| */ |
| public String getSymbol(int i) { |
| int abs = rel2abs(i); |
| if (abs < 0 || abs >= this.symbols.size()) { |
| // System.out.println("Out of bounds error in SymbolTable object"); |
| return null; |
| } |
| return (String) this.symbols.get(abs); |
| |
| } |
| |
| /** |
| * Returns number of symbols in table. |
| * |
| * @return The number of symbols in the table. |
| */ |
| public int size() { |
| return this.symbols.size(); |
| } |
| |
| /** |
| * Returns the string representation of the internal hash table. |
| * |
| * @return A string representing the symbol table. |
| */ |
| public String toString() { |
| StringBuffer buf = new StringBuffer(); |
| buf.append("{ "); |
| final int max = getStart() + size(); |
| for (int i = getStart(); i < max; i++) { |
| buf.append(i + ":" + getSymbol(i)); |
| if ((i + 1) < max) { |
| buf.append(", "); |
| } |
| } |
| buf.append(" }"); |
| return buf.toString(); |
| } |
| |
| /** |
| * Read a file line by line, and create an entry for each line. Empty lines are ignored. Lines |
| * containing only whitespace are not. |
| * |
| * @param filename |
| * The name of the file to be read in. |
| * @return The SymbolTable created from the file. |
| * @exception IOException |
| * Errors reading in the file. |
| */ |
| public static SymbolTable readFromFile(String filename) throws IOException { |
| File stf = new File(filename); |
| FileReader fr = null; |
| BufferedReader in = null; |
| try { |
| fr = new FileReader(stf); |
| in = new BufferedReader(fr); |
| SymbolTable st = new SymbolTable(); |
| String word; |
| while ((word = in.readLine()) != null) { |
| if (!word.equals("")) { |
| st.set(word); |
| } |
| } |
| return st; |
| } finally { |
| if (in != null) { |
| in.close(); |
| } |
| } |
| } |
| |
| } |