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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License"); you may not
      5  * use this file except in compliance with the License. You may obtain a copy of
      6  * the License at
      7  *
      8  * http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
     12  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
     13  * License for the specific language governing permissions and limitations under
     14  * the License.
     15  */
     16 
     17 package com.android.inputmethod.latin;
     18 
     19 import com.android.inputmethod.keyboard.ProximityInfo;
     20 
     21 /**
     22  * Abstract base class for a dictionary that can do a fuzzy search for words based on a set of key
     23  * strokes.
     24  */
     25 public abstract class Dictionary {
     26     /**
     27      * The weight to give to a word if it's length is the same as the number of typed characters.
     28      */
     29     protected static final int FULL_WORD_SCORE_MULTIPLIER = 2;
     30 
     31     public static final int UNIGRAM = 0;
     32     public static final int BIGRAM = 1;
     33 
     34     public static final int NOT_A_PROBABILITY = -1;
     35     /**
     36      * Interface to be implemented by classes requesting words to be fetched from the dictionary.
     37      * @see #getWords(WordComposer, CharSequence, WordCallback, ProximityInfo)
     38      */
     39     public interface WordCallback {
     40         /**
     41          * Adds a word to a list of suggestions. The word is expected to be ordered based on
     42          * the provided score.
     43          * @param word the character array containing the word
     44          * @param wordOffset starting offset of the word in the character array
     45          * @param wordLength length of valid characters in the character array
     46          * @param score the score of occurrence. This is normalized between 1 and 255, but
     47          * can exceed those limits
     48          * @param dicTypeId of the dictionary where word was from
     49          * @param dataType tells type of this data, either UNIGRAM or BIGRAM
     50          * @return true if the word was added, false if no more words are required
     51          */
     52         boolean addWord(char[] word, int wordOffset, int wordLength, int score, int dicTypeId,
     53                 int dataType);
     54     }
     55 
     56     /**
     57      * Searches for words in the dictionary that match the characters in the composer. Matched
     58      * words are added through the callback object.
     59      * @param composer the key sequence to match
     60      * @param prevWordForBigrams the previous word, or null if none
     61      * @param callback the callback object to send matched words to as possible candidates
     62      * @param proximityInfo the object for key proximity. May be ignored by some implementations.
     63      * @see WordCallback#addWord(char[], int, int, int, int, int)
     64      */
     65     abstract public void getWords(final WordComposer composer,
     66             final CharSequence prevWordForBigrams, final WordCallback callback,
     67             final ProximityInfo proximityInfo);
     68 
     69     /**
     70      * Searches for pairs in the bigram dictionary that matches the previous word and all the
     71      * possible words following are added through the callback object.
     72      * @param composer the key sequence to match
     73      * @param previousWord the word before
     74      * @param callback the callback object to send possible word following previous word
     75      */
     76     public void getBigrams(final WordComposer composer, final CharSequence previousWord,
     77             final WordCallback callback) {
     78         // empty base implementation
     79     }
     80 
     81     /**
     82      * Checks if the given word occurs in the dictionary
     83      * @param word the word to search for. The search should be case-insensitive.
     84      * @return true if the word exists, false otherwise
     85      */
     86     abstract public boolean isValidWord(CharSequence word);
     87 
     88     public int getFrequency(CharSequence word) {
     89         return NOT_A_PROBABILITY;
     90     }
     91 
     92     /**
     93      * Compares the contents of the character array with the typed word and returns true if they
     94      * are the same.
     95      * @param word the array of characters that make up the word
     96      * @param length the number of valid characters in the character array
     97      * @param typedWord the word to compare with
     98      * @return true if they are the same, false otherwise.
     99      */
    100     protected boolean same(final char[] word, final int length, final CharSequence typedWord) {
    101         if (typedWord.length() != length) {
    102             return false;
    103         }
    104         for (int i = 0; i < length; i++) {
    105             if (word[i] != typedWord.charAt(i)) {
    106                 return false;
    107             }
    108         }
    109         return true;
    110     }
    111 
    112     /**
    113      * Override to clean up any resources.
    114      */
    115     public void close() {
    116         // empty base implementation
    117     }
    118 }
    119