content: package org.apache.lucene.util;
  
  import java.util.Comparator;
  
  /**
   * 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.
   */
  
  /**
   * Represents char[], as a slice (offset + length) into an existing char[].
   * The {@link #chars} member should never be null; use
   * {@link #EMPTY_ARRAY} if necessary.
   * @lucene.internal
   */
  public final class CharsRef implements Comparable<CharsRef>, CharSequence {
    private static final char[] EMPTY_ARRAY = new char[0];
    public char[] chars;
    public int offset;
    public int length;
  
    /**
     * Creates a new {@link CharsRef} initialized an empty array zero-length
     */
    public CharsRef() {
      this(EMPTY_ARRAY, 0, 0);
    }
  
    /**
     * Creates a new {@link CharsRef} initialized with an array of the given
     * capacity
     */
    public CharsRef(int capacity) {
      chars = new char[capacity];
    }
  
    /**
     * Creates a new {@link CharsRef} initialized with the given array, offset and
     * length
     */
    public CharsRef(char[] chars, int offset, int length) {
      assert chars != null;
      assert chars.length >= offset + length;
      this.chars = chars;
      this.offset = offset;
      this.length = length;
    }
  
    /**
     * Creates a new {@link CharsRef} initialized with the given Strings character
     * array
     */
    public CharsRef(String string) {
      this.chars = string.toCharArray();
      this.offset = 0;
      this.length = chars.length;
    }
  
    /**
     * Creates a new {@link CharsRef} and copies the contents of the source into
     * the new instance.
     * @see #copy(CharsRef)
     */
    public CharsRef(CharsRef other) {
      copy(other);
    }
  
    @Override
    public Object clone() {
      return new CharsRef(this);
    }
  
    @Override
    public int hashCode() {
      final int prime = 31;
      int result = 0;
      final int end = offset + length;
      for (int i = offset; i < end; i++) {
        result = prime * result + chars[i];
      }
      return result;
    }
  
    @Override
    public boolean equals(Object other) {
      if (this == other) {
        return true;
      }
  
      if (other instanceof CharsRef) {
        return charsEquals((CharsRef) other);
      }
  
      if (other instanceof CharSequence) {
        final CharSequence seq = (CharSequence) other;
        if (length == seq.length()) {
          int n = length;
          int i = offset;
          int j = 0;
          while (n-- != 0) {
            if (chars[i++] != seq.charAt(j++))
              return false;
          }
          return true;
        }
      }
      return false;
    }
  
    public boolean charsEquals(CharsRef other) {
      if (length == other.length) {
        int otherUpto = other.offset;
        final char[] otherChars = other.chars;
        final int end = offset + length;
        for (int upto = offset; upto < end; upto++, otherUpto++) {
          if (chars[upto] != otherChars[otherUpto]) {
            return false;
          }
        }
        return true;
      } else {
        return false;
      }
    }
  
    /** Signed int order comparison */
    public int compareTo(CharsRef other) {
      if (this == other)
        return 0;
  
      final char[] aChars = this.chars;
      int aUpto = this.offset;
      final char[] bChars = other.chars;
      int bUpto = other.offset;
  
      final int aStop = aUpto + Math.min(this.length, other.length);
  
      while (aUpto < aStop) {
        int aInt = aChars[aUpto++];
        int bInt = bChars[bUpto++];
        if (aInt > bInt) {
          return 1;
        } else if (aInt < bInt) {
          return -1;
        }
      }
  
      // One is a prefix of the other, or, they are equal:
      return this.length - other.length;
    }
    
    /**
     * Copies the given {@link CharsRef} referenced content into this instance
     * starting at offset 0.
     * 
     * @param other
     *          the {@link CharsRef} to copy
     */
    public void copy(CharsRef other) {
      if (chars == null) {
        chars = new char[other.length];
      } else {
        chars = ArrayUtil.grow(chars, other.length);
      }
      System.arraycopy(other.chars, other.offset, chars, 0, other.length);
      length = other.length;
      offset = 0;
    }
  
    public void grow(int newLength) {
      if (chars.length < newLength) {
        chars = ArrayUtil.grow(chars, newLength);
      }
    }
  
    /**
     * Copies the given array into this CharsRef starting at offset 0
     */
    public void copy(char[] otherChars, int otherOffset, int otherLength) {
      grow(otherLength);
      System.arraycopy(otherChars, otherOffset, this.chars, 0,
          otherLength);
      this.offset = 0;
      this.length = otherLength;
    }
  
    /**
     * Appends the given array to this CharsRef
     */
    public void append(char[] otherChars, int otherOffset, int otherLength) {
      final int newLength = length + otherLength;
      grow(this.offset + newLength);
      System.arraycopy(otherChars, otherOffset, this.chars, this.offset+length,
          otherLength);
      this.length += otherLength;
    }
  
    @Override
    public String toString() {
      return new String(chars, offset, length);
    }
  
    public int length() {
      return length;
    }
  
    public char charAt(int index) {
      return chars[offset + index];
    }
  
    public CharSequence subSequence(int start, int end) {
      return new CharsRef(chars, offset + start, offset + end - 1);
    }
    
    private final static Comparator<CharsRef> utf16SortedAsUTF8SortOrder = new UTF16SortedAsUTF8Comparator();
    
    public static Comparator<CharsRef> getUTF16SortedAsUTF8Comparator() {
      return utf16SortedAsUTF8SortOrder;
    }
    
    private static class UTF16SortedAsUTF8Comparator implements Comparator<CharsRef> {
      // Only singleton
      private UTF16SortedAsUTF8Comparator() {};
  
      public int compare(CharsRef a, CharsRef b) {
        if (a == b)
          return 0;
  
        final char[] aChars = a.chars;
        int aUpto = a.offset;
        final char[] bChars = b.chars;
        int bUpto = b.offset;
  
        final int aStop = aUpto + Math.min(a.length, b.length);
  
        while (aUpto < aStop) {
          char aChar = aChars[aUpto++];
          char bChar = bChars[bUpto++];
          if (aChar != bChar) {
            // http://icu-project.org/docs/papers/utf16_code_point_order.html
            
            /* aChar != bChar, fix up each one if they're both in or above the surrogate range, then compare them */
            if (aChar >= 0xd800 && bChar >= 0xd800) {
              if (aChar >= 0xe000) {
                aChar -= 0x800;
              } else {
                aChar += 0x2000;
              }
              
              if (bChar >= 0xe000) {
                bChar -= 0x800;
              } else {
                bChar += 0x2000;
              }
            }
            
            /* now aChar and bChar are in code point order */
            return (int)aChar - (int)bChar; /* int must be 32 bits wide */
          }
        }
  
        // One is a prefix of the other, or, they are equal:
        return a.length - b.length;
      }
    }
  }