Add Utils.equalsIgnoreCase methods

This change also corrects usage of "frequency", "priority" and "score"
* Frequency is the relative probability in dictionary.
* Score is the relative probability in suggestions.
* Priority is kind a sorted score.

Change-Id: Iafb135a4ecdb401cc505014a07c74dfcac44d699

java/proguard.flags

@@ -18,3 +18,7 @@
 -keep class com.android.inputmethod.latin.AutoCorrection {
   java.lang.CharSequence getAutoCorrectionWord();
 }
+
+-keep class com.android.inputmethod.latin.Utils {
+  boolean equalsIgnoreCase(...);
+}

java/src/com/android/inputmethod/latin/AutoCorrection.java

@@ -48,7 +48,7 @@ public class AutoCorrection {
     }
 
     public void updateAutoCorrectionStatus(Map<String, Dictionary> dictionaries,
-            WordComposer wordComposer, ArrayList<CharSequence> suggestions, int[] priorities,
+            WordComposer wordComposer, ArrayList<CharSequence> suggestions, int[] sortedScores,
             CharSequence typedWord, double autoCorrectionThreshold, int correctionMode,
             CharSequence quickFixedWord, CharSequence whitelistedWord) {
         if (hasAutoCorrectionForWhitelistedWord(whitelistedWord)) {
@@ -62,7 +62,7 @@ public class AutoCorrection {
             mHasAutoCorrection = true;
             mAutoCorrectionWord = quickFixedWord;
         } else if (hasAutoCorrectionForBinaryDictionary(wordComposer, suggestions, correctionMode,
-                priorities, typedWord, autoCorrectionThreshold)) {
+                sortedScores, typedWord, autoCorrectionThreshold)) {
             mHasAutoCorrection = true;
             mAutoCorrectionWord = suggestions.get(0);
         }
@@ -114,13 +114,13 @@ public class AutoCorrection {
     }
 
     private boolean hasAutoCorrectionForBinaryDictionary(WordComposer wordComposer,
-            ArrayList<CharSequence> suggestions, int correctionMode, int[] priorities,
+            ArrayList<CharSequence> suggestions, int correctionMode, int[] sortedScores,
             CharSequence typedWord, double autoCorrectionThreshold) {
         if (wordComposer.size() > 1 && (correctionMode == Suggest.CORRECTION_FULL
                 || correctionMode == Suggest.CORRECTION_FULL_BIGRAM)
-                && typedWord != null && suggestions.size() > 0 && priorities.length > 0) {
+                && typedWord != null && suggestions.size() > 0 && sortedScores.length > 0) {
             final CharSequence autoCorrectionCandidate = suggestions.get(0);
-            final int autoCorrectionCandidateScore = priorities[0];
+            final int autoCorrectionCandidateScore = sortedScores[0];
             // TODO: when the normalized score of the first suggestion is nearly equals to
             //       the normalized score of the second suggestion, behave less aggressive.
             mNormalizedScore = Utils.calcNormalizedScore(

java/src/com/android/inputmethod/latin/BinaryDictionary.java

@@ -54,8 +54,8 @@ public class BinaryDictionary extends Dictionary {
     private final int[] mInputCodes = new int[MAX_WORD_LENGTH * MAX_PROXIMITY_CHARS_SIZE];
     private final char[] mOutputChars = new char[MAX_WORD_LENGTH * MAX_WORDS];
     private final char[] mOutputChars_bigrams = new char[MAX_WORD_LENGTH * MAX_BIGRAMS];
-    private final int[] mFrequencies = new int[MAX_WORDS];
+    private final int[] mScores = new int[MAX_WORDS];
-    private final int[] mFrequencies_bigrams = new int[MAX_BIGRAMS];
+    private final int[] mBigramScores = new int[MAX_BIGRAMS];
 
     private final KeyboardSwitcher mKeyboardSwitcher = KeyboardSwitcher.getInstance();
     private final SubtypeSwitcher mSubtypeSwitcher = SubtypeSwitcher.getInstance();
@@ -149,14 +149,14 @@ public class BinaryDictionary extends Dictionary {
     private native boolean isValidWordNative(int nativeData, char[] word, int wordLength);
     private native int getSuggestionsNative(int dict, int proximityInfo, int[] xCoordinates,
             int[] yCoordinates, int[] inputCodes, int codesSize, int flags, char[] outputChars,
-            int[] frequencies);
+            int[] scores);
     private native int getBigramsNative(int dict, char[] prevWord, int prevWordLength,
-            int[] inputCodes, int inputCodesLength, char[] outputChars, int[] frequencies,
+            int[] inputCodes, int inputCodesLength, char[] outputChars, int[] scores,
             int maxWordLength, int maxBigrams, int maxAlternatives);
 
     private final void loadDictionary(String path, long startOffset, long length) {
         mNativeDict = openNative(path, startOffset, length,
-                    TYPED_LETTER_MULTIPLIER, FULL_WORD_FREQ_MULTIPLIER,
+                    TYPED_LETTER_MULTIPLIER, FULL_WORD_SCORE_MULTIPLIER,
                     MAX_WORD_LENGTH, MAX_WORDS, MAX_PROXIMITY_CHARS_SIZE);
         mDictLength = length;
     }
@@ -168,7 +168,7 @@ public class BinaryDictionary extends Dictionary {
 
         char[] chars = previousWord.toString().toCharArray();
         Arrays.fill(mOutputChars_bigrams, (char) 0);
-        Arrays.fill(mFrequencies_bigrams, 0);
+        Arrays.fill(mBigramScores, 0);
 
         int codesSize = codes.size();
         Arrays.fill(mInputCodes, -1);
@@ -177,18 +177,18 @@ public class BinaryDictionary extends Dictionary {
                 Math.min(alternatives.length, MAX_PROXIMITY_CHARS_SIZE));
 
         int count = getBigramsNative(mNativeDict, chars, chars.length, mInputCodes, codesSize,
-                mOutputChars_bigrams, mFrequencies_bigrams, MAX_WORD_LENGTH, MAX_BIGRAMS,
+                mOutputChars_bigrams, mBigramScores, MAX_WORD_LENGTH, MAX_BIGRAMS,
                 MAX_PROXIMITY_CHARS_SIZE);
 
         for (int j = 0; j < count; ++j) {
-            if (mFrequencies_bigrams[j] < 1) break;
+            if (mBigramScores[j] < 1) break;
             final int start = j * MAX_WORD_LENGTH;
             int len = 0;
             while (len <  MAX_WORD_LENGTH && mOutputChars_bigrams[start + len] != 0) {
                 ++len;
             }
             if (len > 0) {
-                callback.addWord(mOutputChars_bigrams, start, len, mFrequencies_bigrams[j],
+                callback.addWord(mOutputChars_bigrams, start, len, mBigramScores[j],
                         mDicTypeId, DataType.BIGRAM);
             }
         }
@@ -197,17 +197,17 @@ public class BinaryDictionary extends Dictionary {
     @Override
     public void getWords(final WordComposer codes, final WordCallback callback) {
         final int count = getSuggestions(codes, mKeyboardSwitcher.getLatinKeyboard(),
-                mOutputChars, mFrequencies);
+                mOutputChars, mScores);
 
         for (int j = 0; j < count; ++j) {
-            if (mFrequencies[j] < 1) break;
+            if (mScores[j] < 1) break;
             final int start = j * MAX_WORD_LENGTH;
             int len = 0;
             while (len < MAX_WORD_LENGTH && mOutputChars[start + len] != 0) {
                 ++len;
             }
             if (len > 0) {
-                callback.addWord(mOutputChars, start, len, mFrequencies[j], mDicTypeId,
+                callback.addWord(mOutputChars, start, len, mScores[j], mDicTypeId,
                         DataType.UNIGRAM);
             }
         }
@@ -218,7 +218,7 @@ public class BinaryDictionary extends Dictionary {
     }
 
     /* package for test */ int getSuggestions(final WordComposer codes, final Keyboard keyboard,
-            char[] outputChars, int[] frequencies) {
+            char[] outputChars, int[] scores) {
         if (!isValidDictionary()) return -1;
 
         final int codesSize = codes.size();
@@ -232,12 +232,12 @@ public class BinaryDictionary extends Dictionary {
                     Math.min(alternatives.length, MAX_PROXIMITY_CHARS_SIZE));
         }
         Arrays.fill(outputChars, (char) 0);
-        Arrays.fill(frequencies, 0);
+        Arrays.fill(scores, 0);
 
         return getSuggestionsNative(
                 mNativeDict, keyboard.getProximityInfo(),
                 codes.getXCoordinates(), codes.getYCoordinates(), mInputCodes, codesSize,
-                mFlags, outputChars, frequencies);
+                mFlags, outputChars, scores);
     }
 
     @Override

java/src/com/android/inputmethod/latin/Dictionary.java

@@ -29,7 +29,7 @@ public abstract class Dictionary {
     /**
      * The weight to give to a word if it's length is the same as the number of typed characters.
      */
-    protected static final int FULL_WORD_FREQ_MULTIPLIER = 2;
+    protected static final int FULL_WORD_SCORE_MULTIPLIER = 2;
 
     public static enum DataType {
         UNIGRAM, BIGRAM
@@ -42,17 +42,17 @@ public abstract class Dictionary {
     public interface WordCallback {
         /**
          * Adds a word to a list of suggestions. The word is expected to be ordered based on
-         * the provided frequency.
+         * the provided score.
          * @param word the character array containing the word
          * @param wordOffset starting offset of the word in the character array
          * @param wordLength length of valid characters in the character array
-         * @param frequency the frequency of occurrence. This is normalized between 1 and 255, but
+         * @param score the score of occurrence. This is normalized between 1 and 255, but
          * can exceed those limits
          * @param dicTypeId of the dictionary where word was from
          * @param dataType tells type of this data
          * @return true if the word was added, false if no more words are required
          */
-        boolean addWord(char[] word, int wordOffset, int wordLength, int frequency, int dicTypeId,
+        boolean addWord(char[] word, int wordOffset, int wordLength, int score, int dicTypeId,
                 DataType dataType);
     }
 

java/src/com/android/inputmethod/latin/ExpandableDictionary.java

@@ -327,7 +327,7 @@ public class ExpandableDictionary extends Dictionary {
                                     final int finalFreq;
                                     if (skipPos < 0) {
                                         finalFreq = freq * snr * addedAttenuation
-                                                * FULL_WORD_FREQ_MULTIPLIER;
+                                                * FULL_WORD_SCORE_MULTIPLIER;
                                     } else {
                                         finalFreq = computeSkippedWordFinalFreq(freq,
                                                 snr * addedAttenuation, mInputLength);

java/src/com/android/inputmethod/latin/Suggest.java

@@ -47,7 +47,7 @@ public class Suggest implements Dictionary.WordCallback {
 
     /**
      * Words that appear in both bigram and unigram data gets multiplier ranging from
-     * BIGRAM_MULTIPLIER_MIN to BIGRAM_MULTIPLIER_MAX depending on the frequency score from
+     * BIGRAM_MULTIPLIER_MIN to BIGRAM_MULTIPLIER_MAX depending on the score from
      * bigram data.
      */
     public static final double BIGRAM_MULTIPLIER_MIN = 1.2;
@@ -92,13 +92,13 @@ public class Suggest implements Dictionary.WordCallback {
     private boolean mQuickFixesEnabled;
 
     private double mAutoCorrectionThreshold;
-    private int[] mPriorities = new int[mPrefMaxSuggestions];
+    private int[] mScores = new int[mPrefMaxSuggestions];
-    private int[] mBigramPriorities = new int[PREF_MAX_BIGRAMS];
+    private int[] mBigramScores = new int[PREF_MAX_BIGRAMS];
 
     private ArrayList<CharSequence> mSuggestions = new ArrayList<CharSequence>();
     ArrayList<CharSequence> mBigramSuggestions  = new ArrayList<CharSequence>();
     private ArrayList<CharSequence> mStringPool = new ArrayList<CharSequence>();
-    private String mLowerOriginalWord;
+    private CharSequence mTypedWord;
 
     // TODO: Remove these member variables by passing more context to addWord() callback method
     private boolean mIsFirstCharCapitalized;
@@ -207,8 +207,8 @@ public class Suggest implements Dictionary.WordCallback {
             throw new IllegalArgumentException("maxSuggestions must be between 1 and 100");
         }
         mPrefMaxSuggestions = maxSuggestions;
-        mPriorities = new int[mPrefMaxSuggestions];
+        mScores = new int[mPrefMaxSuggestions];
-        mBigramPriorities = new int[PREF_MAX_BIGRAMS];
+        mBigramScores = new int[PREF_MAX_BIGRAMS];
         collectGarbage(mSuggestions, mPrefMaxSuggestions);
         while (mStringPool.size() < mPrefMaxSuggestions) {
             StringBuilder sb = new StringBuilder(getApproxMaxWordLength());
@@ -256,25 +256,23 @@ public class Suggest implements Dictionary.WordCallback {
         mIsFirstCharCapitalized = wordComposer.isFirstCharCapitalized();
         mIsAllUpperCase = wordComposer.isAllUpperCase();
         collectGarbage(mSuggestions, mPrefMaxSuggestions);
-        Arrays.fill(mPriorities, 0);
+        Arrays.fill(mScores, 0);
 
         // Save a lowercase version of the original word
         CharSequence typedWord = wordComposer.getTypedWord();
         if (typedWord != null) {
             final String typedWordString = typedWord.toString();
             typedWord = typedWordString;
-            mLowerOriginalWord = typedWordString.toLowerCase();
             // Treating USER_TYPED as UNIGRAM suggestion for logging now.
             LatinImeLogger.onAddSuggestedWord(typedWordString, Suggest.DIC_USER_TYPED,
                     Dictionary.DataType.UNIGRAM);
-        } else {
-            mLowerOriginalWord = "";
         }
+        mTypedWord = typedWord;
 
         if (wordComposer.size() == 1 && (mCorrectionMode == CORRECTION_FULL_BIGRAM
                 || mCorrectionMode == CORRECTION_BASIC)) {
             // At first character typed, search only the bigrams
-            Arrays.fill(mBigramPriorities, 0);
+            Arrays.fill(mBigramScores, 0);
             collectGarbage(mBigramSuggestions, PREF_MAX_BIGRAMS);
 
             if (!TextUtils.isEmpty(prevWordForBigram)) {
@@ -346,7 +344,7 @@ public class Suggest implements Dictionary.WordCallback {
                 mWhiteListDictionary.getWhiteListedWord(typedWordString));
 
         mAutoCorrection.updateAutoCorrectionStatus(mUnigramDictionaries, wordComposer,
-                mSuggestions, mPriorities, typedWord, mAutoCorrectionThreshold, mCorrectionMode,
+                mSuggestions, mScores, typedWord, mAutoCorrectionThreshold, mCorrectionMode,
                 autoText, whitelistedWord);
 
         if (autoText != null) {
@@ -364,26 +362,25 @@ public class Suggest implements Dictionary.WordCallback {
 
         if (DBG) {
             double normalizedScore = mAutoCorrection.getNormalizedScore();
-            ArrayList<SuggestedWords.SuggestedWordInfo> frequencyInfoList =
+            ArrayList<SuggestedWords.SuggestedWordInfo> scoreInfoList =
                     new ArrayList<SuggestedWords.SuggestedWordInfo>();
-            frequencyInfoList.add(new SuggestedWords.SuggestedWordInfo("+", false));
+            scoreInfoList.add(new SuggestedWords.SuggestedWordInfo("+", false));
-            final int priorityLength = mPriorities.length;
+            for (int i = 0; i < mScores.length; ++i) {
-            for (int i = 0; i < priorityLength; ++i) {
                 if (normalizedScore > 0) {
-                    final String priorityThreshold = Integer.toString(mPriorities[i]) + " (" +
+                    final String scoreThreshold = Integer.toString(mScores[i]) + " (" +
                             normalizedScore + ")";
-                    frequencyInfoList.add(
+                    scoreInfoList.add(
-                            new SuggestedWords.SuggestedWordInfo(priorityThreshold, false));
+                            new SuggestedWords.SuggestedWordInfo(scoreThreshold, false));
                     normalizedScore = 0.0;
                 } else {
-                    final String priority = Integer.toString(mPriorities[i]);
+                    final String score = Integer.toString(mScores[i]);
-                    frequencyInfoList.add(new SuggestedWords.SuggestedWordInfo(priority, false));
+                    scoreInfoList.add(new SuggestedWords.SuggestedWordInfo(score, false));
                 }
             }
-            for (int i = priorityLength; i < mSuggestions.size(); ++i) {
+            for (int i = mScores.length; i < mSuggestions.size(); ++i) {
-                frequencyInfoList.add(new SuggestedWords.SuggestedWordInfo("--", false));
+                scoreInfoList.add(new SuggestedWords.SuggestedWordInfo("--", false));
             }
-            return new SuggestedWords.Builder().addWords(mSuggestions, frequencyInfoList);
+            return new SuggestedWords.Builder().addWords(mSuggestions, scoreInfoList);
         }
         return new SuggestedWords.Builder().addWords(mSuggestions, null);
     }
@@ -419,52 +416,37 @@ public class Suggest implements Dictionary.WordCallback {
         return mAutoCorrection.hasAutoCorrection();
     }
 
-    private static boolean compareCaseInsensitive(final String lowerOriginalWord,
-            final char[] word, final int offset, final int length) {
-        final int originalLength = lowerOriginalWord.length();
-        if (originalLength == length && Character.isUpperCase(word[offset])) {
-            for (int i = 0; i < originalLength; i++) {
-                if (lowerOriginalWord.charAt(i) != Character.toLowerCase(word[offset+i])) {
-                    return false;
-                }
-            }
-            return true;
-        }
-        return false;
-    }
-
     @Override
-    public boolean addWord(final char[] word, final int offset, final int length, int freq,
+    public boolean addWord(final char[] word, final int offset, final int length, int score,
             final int dicTypeId, final Dictionary.DataType dataType) {
         Dictionary.DataType dataTypeForLog = dataType;
-        ArrayList<CharSequence> suggestions;
+        final ArrayList<CharSequence> suggestions;
-        int[] priorities;
+        final int[] sortedScores;
-        int prefMaxSuggestions;
+        final int prefMaxSuggestions;
         if(dataType == Dictionary.DataType.BIGRAM) {
             suggestions = mBigramSuggestions;
-            priorities = mBigramPriorities;
+            sortedScores = mBigramScores;
             prefMaxSuggestions = PREF_MAX_BIGRAMS;
         } else {
             suggestions = mSuggestions;
-            priorities = mPriorities;
+            sortedScores = mScores;
             prefMaxSuggestions = mPrefMaxSuggestions;
         }
 
         int pos = 0;
 
         // Check if it's the same word, only caps are different
-        if (compareCaseInsensitive(mLowerOriginalWord, word, offset, length)) {
+        if (Utils.equalsIgnoreCase(mTypedWord, word, offset, length)) {
             // TODO: remove this surrounding if clause and move this logic to
             // getSuggestedWordBuilder.
             if (suggestions.size() > 0) {
-                final String currentHighestWordLowerCase =
+                final String currentHighestWord = suggestions.get(0).toString();
-                        suggestions.get(0).toString().toLowerCase();
                 // If the current highest word is also equal to typed word, we need to compare
                 // frequency to determine the insertion position. This does not ensure strictly
                 // correct ordering, but ensures the top score is on top which is enough for
                 // removing duplicates correctly.
-                if (compareCaseInsensitive(currentHighestWordLowerCase, word, offset, length)
+                if (Utils.equalsIgnoreCase(currentHighestWord, word, offset, length)
-                        && freq <= priorities[0]) {
+                        && score <= sortedScores[0]) {
                     pos = 1;
                 }
             }
@@ -475,24 +457,24 @@ public class Suggest implements Dictionary.WordCallback {
                 if(bigramSuggestion >= 0) {
                     dataTypeForLog = Dictionary.DataType.BIGRAM;
                     // turn freq from bigram into multiplier specified above
-                    double multiplier = (((double) mBigramPriorities[bigramSuggestion])
+                    double multiplier = (((double) mBigramScores[bigramSuggestion])
                             / MAXIMUM_BIGRAM_FREQUENCY)
                             * (BIGRAM_MULTIPLIER_MAX - BIGRAM_MULTIPLIER_MIN)
                             + BIGRAM_MULTIPLIER_MIN;
                     /* Log.d(TAG,"bigram num: " + bigramSuggestion
                             + "  wordB: " + mBigramSuggestions.get(bigramSuggestion).toString()
-                            + "  currentPriority: " + freq + "  bigramPriority: "
+                            + "  currentScore: " + score + "  bigramScore: "
-                            + mBigramPriorities[bigramSuggestion]
+                            + mBigramScores[bigramSuggestion]
                             + "  multiplier: " + multiplier); */
-                    freq = (int)Math.round((freq * multiplier));
+                    score = (int)Math.round((score * multiplier));
                 }
             }
 
-            // Check the last one's priority and bail
+            // Check the last one's score and bail
-            if (priorities[prefMaxSuggestions - 1] >= freq) return true;
+            if (sortedScores[prefMaxSuggestions - 1] >= score) return true;
             while (pos < prefMaxSuggestions) {
-                if (priorities[pos] < freq
+                if (sortedScores[pos] < score
-                        || (priorities[pos] == freq && length < suggestions.get(pos).length())) {
+                        || (sortedScores[pos] == score && length < suggestions.get(pos).length())) {
                     break;
                 }
                 pos++;
@@ -502,8 +484,8 @@ public class Suggest implements Dictionary.WordCallback {
             return true;
         }
 
-        System.arraycopy(priorities, pos, priorities, pos + 1, prefMaxSuggestions - pos - 1);
+        System.arraycopy(sortedScores, pos, sortedScores, pos + 1, prefMaxSuggestions - pos - 1);
-        priorities[pos] = freq;
+        sortedScores[pos] = score;
         int poolSize = mStringPool.size();
         StringBuilder sb = poolSize > 0 ? (StringBuilder) mStringPool.remove(poolSize - 1)
                 : new StringBuilder(getApproxMaxWordLength());

java/src/com/android/inputmethod/latin/Utils.java

@@ -285,7 +285,7 @@ public class Utils {
 
     // In dictionary.cpp, getSuggestion() method,
     // suggestion scores are computed using the below formula.
-    // original score (called 'frequency')
+    // original score
     //  := pow(mTypedLetterMultiplier (this is defined 2),
     //         (the number of matched characters between typed word and suggested word))
     //     * (individual word's score which defined in the unigram dictionary,
@@ -295,7 +295,7 @@ public class Utils {
     //       (full match up to min(before.length(), after.length())
     //       => Then multiply by FULL_MATCHED_WORDS_PROMOTION_RATE (this is defined 1.2)
     //     - If the word is a true full match except for differences in accents or
-    //       capitalization, then treat it as if the frequency was 255.
+    //       capitalization, then treat it as if the score was 255.
     //     - If before.length() == after.length()
     //       => multiply by mFullWordMultiplier (this is defined 2))
     // So, maximum original score is pow(2, min(before.length(), after.length())) * 255 * 2 * 1.2
@@ -561,4 +561,66 @@ public class Utils {
             Log.e(TAG, "Could not load native library jni_latinime");
         }
     }
+
+    /**
+     * Returns true if a and b are equal ignoring the case of the character.
+     * @param a first character to check
+     * @param b second character to check
+     * @return {@code true} if a and b are equal, {@code false} otherwise.
+     */
+    public static boolean equalsIgnoreCase(char a, char b) {
+        // Some language, such as Turkish, need testing both cases.
+        return a == b
+                || Character.toLowerCase(a) == Character.toLowerCase(b)
+                || Character.toUpperCase(a) == Character.toUpperCase(b);
+    }
+
+    /**
+     * Returns true if a and b are equal ignoring the case of the characters, including if they are
+     * both null.
+     * @param a first CharSequence to check
+     * @param b second CharSequence to check
+     * @return {@code true} if a and b are equal, {@code false} otherwise.
+     */
+    public static boolean equalsIgnoreCase(CharSequence a, CharSequence b) {
+        if (a == b)
+            return true;  // including both a and b are null.
+        if (a == null || b == null)
+            return false;
+        final int length = a.length();
+        if (length != b.length())
+            return false;
+        for (int i = 0; i < length; i++) {
+            if (!equalsIgnoreCase(a.charAt(i), b.charAt(i)))
+                return false;
+        }
+        return true;
+    }
+
+    /**
+     * Returns true if a and b are equal ignoring the case of the characters, including if a is null
+     * and b is zero length.
+     * @param a CharSequence to check
+     * @param b character array to check
+     * @param offset start offset of array b
+     * @param length length of characters in array b
+     * @return {@code true} if a and b are equal, {@code false} otherwise.
+     * @throws IndexOutOfBoundsException
+     *   if {@code offset < 0 || length < 0 || offset + length > data.length}.
+     * @throws NullPointerException if {@code b == null}.
+     */
+    public static boolean equalsIgnoreCase(CharSequence a, char[] b, int offset, int length) {
+        if (offset < 0 || length < 0 || length > b.length - offset)
+            throw new IndexOutOfBoundsException("array.length=" + b.length + " offset=" + offset
+                    + " length=" + length);
+        if (a == null)
+            return length == 0;  // including a is null and b is zero length.
+        if (a.length() != length)
+            return false;
+        for (int i = 0; i < length; i++) {
+            if (!equalsIgnoreCase(a.charAt(i), b[offset + i]))
+                return false;
+        }
+        return true;
+    }
 }