    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.lang3;
    018
    019/**
    020 * <p>Operations on {@link CharSequence} that are
    021 * {@code null} safe.</p>
    022 *
    023 * @see CharSequence
    024 * @since 3.0
    025 */
    026public class CharSequenceUtils {
    027
    028    private static final int NOT_FOUND = -1;
    029
    030    /**
    031     * <p>{@code CharSequenceUtils} instances should NOT be constructed in
    032     * standard programming. </p>
    033     *
    034     * <p>This constructor is public to permit tools that require a JavaBean
    035     * instance to operate.</p>
    036     */
    037    public CharSequenceUtils() {
    038        super();
    039    }
    040
    041    //-----------------------------------------------------------------------
    042    /**
    043     * <p>Returns a new {@code CharSequence} that is a subsequence of this
    044     * sequence starting with the {@code char} value at the specified index.</p>
    045     *
    046     * <p>This provides the {@code CharSequence} equivalent to {@link String#substring(int)}.
    047     * The length (in {@code char}) of the returned sequence is {@code length() - start},
    048     * so if {@code start == end} then an empty sequence is returned.</p>
    049     *
    050     * @param cs  the specified subsequence, null returns null
    051     * @param start  the start index, inclusive, valid
    052     * @return a new subsequence, may be null
    053     * @throws IndexOutOfBoundsException if {@code start} is negative or if
    054     *  {@code start} is greater than {@code length()}
    055     */
    056    public static CharSequence subSequence(final CharSequence cs, final int start) {
    057        return cs == null ? null : cs.subSequence(start, cs.length());
    058    }
    059
    060    //-----------------------------------------------------------------------
    061    /**
    062     * Returns the index within {@code cs} of the first occurrence of the
    063     * specified character, starting the search at the specified index.
    064     * <p>
    065     * If a character with value {@code searchChar} occurs in the
    066     * character sequence represented by the {@code cs}
    067     * object at an index no smaller than {@code start}, then
    068     * the index of the first such occurrence is returned. For values
    069     * of {@code searchChar} in the range from 0 to 0xFFFF (inclusive),
    070     * this is the smallest value <i>k</i> such that:
    071     * <blockquote><pre>
    072     * (this.charAt(<i>k</i>) == searchChar) &amp;&amp; (<i>k</i> &gt;= start)
    073     * </pre></blockquote>
    074     * is true. For other values of {@code searchChar}, it is the
    075     * smallest value <i>k</i> such that:
    076     * <blockquote><pre>
    077     * (this.codePointAt(<i>k</i>) == searchChar) &amp;&amp; (<i>k</i> &gt;= start)
    078     * </pre></blockquote>
    079     * is true. In either case, if no such character occurs inm {@code cs}
    080     * at or after position {@code start}, then
    081     * {@code -1} is returned.
    082     *
    083     * <p>
    084     * There is no restriction on the value of {@code start}. If it
    085     * is negative, it has the same effect as if it were zero: the entire
    086     * {@code CharSequence} may be searched. If it is greater than
    087     * the length of {@code cs}, it has the same effect as if it were
    088     * equal to the length of {@code cs}: {@code -1} is returned.
    089     *
    090     * <p>All indices are specified in {@code char} values
    091     * (Unicode code units).
    092     *
    093     * @param cs  the {@code CharSequence} to be processed, not null
    094     * @param searchChar  the char to be searched for
    095     * @param start  the start index, negative starts at the string start
    096     * @return the index where the search char was found, -1 if not found
    097     * @since 3.6 updated to behave more like {@code String}
    098     */
    099    static int indexOf(final CharSequence cs, final int searchChar, int start) {
    100        if (cs instanceof String) {
    101            return ((String) cs).indexOf(searchChar, start);
    102        }
    103        final int sz = cs.length();
    104        if (start < 0) {
    105            start = 0;
    106        }
    107        if (searchChar < Character.MIN_SUPPLEMENTARY_CODE_POINT) {
    108            for (int i = start; i < sz; i++) {
    109                if (cs.charAt(i) == searchChar) {
    110                    return i;
    111                }
    112            }
    113        }
    114        //supplementary characters (LANG1300)
    115        if (searchChar <= Character.MAX_CODE_POINT) {
    116            final char[] chars = Character.toChars(searchChar);
    117            for (int i = start; i < sz - 1; i++) {
    118                final char high = cs.charAt(i);
    119                final char low = cs.charAt(i + 1);
    120                if (high == chars[0] && low == chars[1]) {
    121                    return i;
    122                }
    123            }
    124        }
    125        return NOT_FOUND;
    126    }
    127
    128    /**
    129     * Used by the indexOf(CharSequence methods) as a green implementation of indexOf.
    130     *
    131     * @param cs the {@code CharSequence} to be processed
    132     * @param searchChar the {@code CharSequence} to be searched for
    133     * @param start the start index
    134     * @return the index where the search sequence was found
    135     */
    136    static int indexOf(final CharSequence cs, final CharSequence searchChar, final int start) {
    137        if (cs instanceof String) {
    138            return ((String) cs).indexOf(searchChar.toString(), start);
    139        } else if (cs instanceof StringBuilder) {
    140            return ((StringBuilder) cs).indexOf(searchChar.toString(), start);
    141        } else if (cs instanceof StringBuffer) {
    142            return ((StringBuffer) cs).indexOf(searchChar.toString(), start);
    143        }
    144        return cs.toString().indexOf(searchChar.toString(), start);
    145//        if (cs instanceof String && searchChar instanceof String) {
    146//            // TODO: Do we assume searchChar is usually relatively small;
    147//            //       If so then calling toString() on it is better than reverting to
    148//            //       the green implementation in the else block
    149//            return ((String) cs).indexOf((String) searchChar, start);
    150//        } else {
    151//            // TODO: Implement rather than convert to String
    152//            return cs.toString().indexOf(searchChar.toString(), start);
    153//        }
    154    }
    155
    156    /**
    157     * Returns the index within {@code cs} of the last occurrence of
    158     * the specified character, searching backward starting at the
    159     * specified index. For values of {@code searchChar} in the range
    160     * from 0 to 0xFFFF (inclusive), the index returned is the largest
    161     * value <i>k</i> such that:
    162     * <blockquote><pre>
    163     * (this.charAt(<i>k</i>) == searchChar) &amp;&amp; (<i>k</i> &lt;= start)
    164     * </pre></blockquote>
    165     * is true. For other values of {@code searchChar}, it is the
    166     * largest value <i>k</i> such that:
    167     * <blockquote><pre>
    168     * (this.codePointAt(<i>k</i>) == searchChar) &amp;&amp; (<i>k</i> &lt;= start)
    169     * </pre></blockquote>
    170     * is true. In either case, if no such character occurs in {@code cs}
    171     * at or before position {@code start}, then {@code -1} is returned.
    172     *
    173     * <p>All indices are specified in {@code char} values
    174     * (Unicode code units).
    175     *
    176     * @param cs  the {@code CharSequence} to be processed
    177     * @param searchChar  the char to be searched for
    178     * @param start  the start index, negative returns -1, beyond length starts at end
    179     * @return the index where the search char was found, -1 if not found
    180     * @since 3.6 updated to behave more like {@code String}
    181     */
    182    static int lastIndexOf(final CharSequence cs, final int searchChar, int start) {
    183        if (cs instanceof String) {
    184            return ((String) cs).lastIndexOf(searchChar, start);
    185        }
    186        final int sz = cs.length();
    187        if (start < 0) {
    188            return NOT_FOUND;
    189        }
    190        if (start >= sz) {
    191            start = sz - 1;
    192        }
    193        if (searchChar < Character.MIN_SUPPLEMENTARY_CODE_POINT) {
    194            for (int i = start; i >= 0; --i) {
    195                if (cs.charAt(i) == searchChar) {
    196                    return i;
    197                }
    198            }
    199        }
    200        //supplementary characters (LANG1300)
    201        //NOTE - we must do a forward traversal for this to avoid duplicating code points
    202        if (searchChar <= Character.MAX_CODE_POINT) {
    203            final char[] chars = Character.toChars(searchChar);
    204            //make sure it's not the last index
    205            if (start == sz - 1) {
    206                return NOT_FOUND;
    207            }
    208            for (int i = start; i >= 0; i--) {
    209                final char high = cs.charAt(i);
    210                final char low = cs.charAt(i + 1);
    211                if (chars[0] == high && chars[1] == low) {
    212                    return i;
    213                }
    214            }
    215        }
    216        return NOT_FOUND;
    217    }
    218
    219    static final int TO_STRING_LIMIT = 16;
    220
    221    /**
    222     * Used by the lastIndexOf(CharSequence methods) as a green implementation of lastIndexOf
    223     *
    224     * @param cs the {@code CharSequence} to be processed
    225     * @param searchChar the {@code CharSequence} to be searched for
    226     * @param start the start index
    227     * @return the index where the search sequence was found
    228     */
    229    static int lastIndexOf(final CharSequence cs, final CharSequence searchChar, int start) {
    230        if (searchChar instanceof String) {
    231            if (cs instanceof String) {
    232                return ((String) cs).lastIndexOf((String) searchChar, start);
    233            } else if (cs instanceof StringBuilder) {
    234                return ((StringBuilder) cs).lastIndexOf((String) searchChar, start);
    235            } else if (cs instanceof StringBuffer) {
    236                return ((StringBuffer) cs).lastIndexOf((String) searchChar, start);
    237            }
    238        }
    239
    240        final int len1 = cs.length();
    241        final int len2 = searchChar.length();
    242
    243        if (start > len1) {
    244            start = len1;
    245        }
    246
    247        if (start < 0 || len2 < 0 || len2 > len1) {
    248            return -1;
    249        }
    250
    251        if (len2 == 0) {
    252            return start;
    253        }
    254
    255        if (len2 <= TO_STRING_LIMIT) {
    256            if (cs instanceof String) {
    257                return ((String) cs).lastIndexOf(searchChar.toString(), start);
    258            } else if (cs instanceof StringBuilder) {
    259                return ((StringBuilder) cs).lastIndexOf(searchChar.toString(), start);
    260            } else if (cs instanceof StringBuffer) {
    261                return ((StringBuffer) cs).lastIndexOf(searchChar.toString(), start);
    262            }
    263        }
    264
    265        if (start + len2 > len1) {
    266            start = len1 - len2;
    267        }
    268
    269        final char char0 = searchChar.charAt(0);
    270
    271        int i = start;
    272        while (true) {
    273            while (cs.charAt(i) != char0) {
    274                i--;
    275                if (i < 0) {
    276                    return -1;
    277                }
    278            }
    279            if (checkLaterThan1(cs, searchChar, len2, i)) {
    280                return i;
    281            }
    282            i--;
    283            if (i < 0) {
    284                return -1;
    285            }
    286        }
    287    }
    288
    289    private static boolean checkLaterThan1(final CharSequence cs, final CharSequence searchChar, final int len2, final int start1) {
    290        for (int i = 1, j = len2 - 1; i <= j; i++, j--) {
    291            if (cs.charAt(start1 + i) != searchChar.charAt(i)
    292                    ||
    293                    cs.charAt(start1 + j) != searchChar.charAt(j)
    294            ) {
    295                return false;
    296            }
    297        }
    298        return true;
    299    }
    300
    301    /**
    302     * Converts the given CharSequence to a char[].
    303     *
    304     * @param source the {@code CharSequence} to be processed.
    305     * @return the resulting char array, never null.
    306     * @since 3.11
    307     */
    308    public static char[] toCharArray(final CharSequence source) {
    309        final int len = StringUtils.length(source);
    310        if (len == 0) {
    311            return ArrayUtils.EMPTY_CHAR_ARRAY;
    312        }
    313        if (source instanceof String) {
    314            return ((String) source).toCharArray();
    315        }
    316        final char[] array = new char[len];
    317        for (int i = 0; i < len; i++) {
    318            array[i] = source.charAt(i);
    319        }
    320        return array;
    321    }
    322
    323    /**
    324     * Green implementation of regionMatches.
    325     *
    326     * @param cs the {@code CharSequence} to be processed
    327     * @param ignoreCase whether or not to be case insensitive
    328     * @param thisStart the index to start on the {@code cs} CharSequence
    329     * @param substring the {@code CharSequence} to be looked for
    330     * @param start the index to start on the {@code substring} CharSequence
    331     * @param length character length of the region
    332     * @return whether the region matched
    333     */
    334    static boolean regionMatches(final CharSequence cs, final boolean ignoreCase, final int thisStart,
    335            final CharSequence substring, final int start, final int length)    {
    336        if (cs instanceof String && substring instanceof String) {
    337            return ((String) cs).regionMatches(ignoreCase, thisStart, (String) substring, start, length);
    338        }
    339        int index1 = thisStart;
    340        int index2 = start;
    341        int tmpLen = length;
    342
    343        // Extract these first so we detect NPEs the same as the java.lang.String version
    344        final int srcLen = cs.length() - thisStart;
    345        final int otherLen = substring.length() - start;
    346
    347        // Check for invalid parameters
    348        if (thisStart < 0 || start < 0 || length < 0) {
    349            return false;
    350        }
    351
    352        // Check that the regions are long enough
    353        if (srcLen < length || otherLen < length) {
    354            return false;
    355        }
    356
    357        while (tmpLen-- > 0) {
    358            final char c1 = cs.charAt(index1++);
    359            final char c2 = substring.charAt(index2++);
    360
    361            if (c1 == c2) {
    362                continue;
    363            }
    364
    365            if (!ignoreCase) {
    366                return false;
    367            }
    368
    369            // The real same check as in String.regionMatches():
    370            final char u1 = Character.toUpperCase(c1);
    371            final char u2 = Character.toUpperCase(c2);
    372            if (u1 != u2 && Character.toLowerCase(u1) != Character.toLowerCase(u2)) {
    373                return false;
    374            }
    375        }
    376
    377        return true;
    378    }
    379}