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1 /*******************************************************************************
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2 * Copyright (c) 2005 IBM Corporation and others.
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3 * All rights reserved. This program and the accompanying materials
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4 * are made available under the terms of the Eclipse Public License v1.0
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5 * which accompanies this distribution, and is available at
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6 * http://www.eclipse.org/legal/epl-v10.html
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7 *
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8 * Contributors:
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9 * IBM - Initial API and implementation
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10 * Port to the D programming language:
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11 * Frank Benoit <benoit@tionex.de>
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12 *******************************************************************************/
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13 module dwtx.core.internal.jobs.StringPool;
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14
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15 import dwt.dwthelper.utils;
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16 import dwtx.dwtxhelper.Collection;
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17
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18 /**
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19 * A string pool is used for sharing strings in a way that eliminates duplicate
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20 * equal strings. A string pool instance can be maintained over a long period
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21 * of time, or used as a temporary structure during a string sharing pass over
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22 * a data structure.
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23 * <p>
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24 * This class is not intended to be subclassed by clients.
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25 * </p>
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26 *
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27 * Note: This class is copied from dwtx.core.resources
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28 *
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29 * @since 3.1
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30 */
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31 public final class StringPool {
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32 private int savings;
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33 private const HashMap map;
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34
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35 public this(){
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36 map = new HashMap();
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37 }
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38
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39 /**
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40 * Adds a <code>String</code> to the pool. Returns a <code>String</code>
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41 * that is equal to the argument but that is unique within this pool.
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42 * @param string The string to add to the pool
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43 * @return A string that is equal to the argument.
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44 */
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45 public String add(String string) {
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46 if (string is null)
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47 return string;
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48 Object result = map.get(string);
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49 if (result !is null) {
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50 if (stringcast(result) !is string)
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51 savings += 44 + 2 * string.length;
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52 return stringcast( result );
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53 }
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54 map.put(string, string);
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55 return string;
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56 }
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57
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58 /**
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59 * Returns an estimate of the size in bytes that was saved by sharing strings in
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60 * the pool. In particular, this returns the size of all strings that were added to the
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61 * pool after an equal string had already been added. This value can be used
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62 * to estimate the effectiveness of a string sharing operation, in order to
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63 * determine if or when it should be performed again.
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64 *
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65 * In some cases this does not precisely represent the number of bytes that
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66 * were saved. For example, say the pool already contains string S1. Now
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67 * string S2, which is equal to S1 but not identical, is added to the pool five
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68 * times. This method will return the size of string S2 multiplied by the
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69 * number of times it was added, even though the actual savings in this case
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70 * is only the size of a single copy of S2.
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71 */
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72 public int getSavedStringCount() {
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73 return savings;
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74 }
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75 }
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