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Lucene example source code file (BytesRef.java)

This example Lucene source code file (BytesRef.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

bytesref, bytesref, comparator, comparator, empty_bytes, hash_prime, io, object, override, override, string, stringbuilder, utf8sortedasunicodecomparator, utf8sortedasutf16comparator, utf8sortedasutf16comparator, util

The Lucene BytesRef.java source code

package org.apache.lucene.util;

/**
 * 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.
 */

import java.util.Comparator;
import java.io.UnsupportedEncodingException;

/** Represents byte[], as a slice (offset + length) into an
 *  existing byte[].
 *
 *  @lucene.experimental */
public final class BytesRef implements Comparable<BytesRef> {

  static final int HASH_PRIME = 31;
  public static final byte[] EMPTY_BYTES = new byte[0]; 

  /** The contents of the BytesRef. Should never be {@code null}. */
  public byte[] bytes;

  /** Offset of first valid byte. */
  public int offset;

  /** Length of used bytes. */
  public int length;

  public BytesRef() {
    bytes = EMPTY_BYTES;
  }

  /** This instance will directly reference bytes w/o making a copy.
   * bytes should not be null.
   */
  public BytesRef(byte[] bytes, int offset, int length) {
    assert bytes != null;
    this.bytes = bytes;
    this.offset = offset;
    this.length = length;
  }

  /** This instance will directly reference bytes w/o making a copy.
   * bytes should not be null */
  public BytesRef(byte[] bytes) {
    assert bytes != null;
    this.bytes = bytes;
    this.offset = 0;
    this.length = bytes.length;
  }

  public BytesRef(int capacity) {
    this.bytes = new byte[capacity];
  }

  /**
   * @param text Initialize the byte[] from the UTF8 bytes
   * for the provided Sring.  This must be well-formed
   * unicode text, with no unpaired surrogates or U+FFFF.
   */
  public BytesRef(CharSequence text) {
    this();
    copy(text);
  }
  
  /**
   * @param text Initialize the byte[] from the UTF8 bytes
   * for the provided array.  This must be well-formed
   * unicode text, with no unpaired surrogates or U+FFFF.
   */
  public BytesRef(char text[], int offset, int length) {
    this(length * 4);
    copy(text, offset, length);
  }

  public BytesRef(BytesRef other) {
    this();
    copy(other);
  }

  /* // maybe?
  public BytesRef(BytesRef other, boolean shallow) {
    this();
    if (shallow) {
      offset = other.offset;
      length = other.length;
      bytes = other.bytes;
    } else {
      copy(other);
    }
  }
  */

  /**
   * Copies the UTF8 bytes for this string.
   * 
   * @param text Must be well-formed unicode text, with no
   * unpaired surrogates or invalid UTF16 code units.
   */
  public void copy(CharSequence text) {
    UnicodeUtil.UTF16toUTF8(text, 0, text.length(), this);
  }

  /**
   * Copies the UTF8 bytes for this string.
   * 
   * @param text Must be well-formed unicode text, with no
   * unpaired surrogates or invalid UTF16 code units.
   */
  public void copy(char text[], int offset, int length) {
    UnicodeUtil.UTF16toUTF8(text, offset, length, this);
  }

  public boolean bytesEquals(BytesRef other) {
    if (length == other.length) {
      int otherUpto = other.offset;
      final byte[] otherBytes = other.bytes;
      final int end = offset + length;
      for(int upto=offset;upto<end;upto++,otherUpto++) {
        if (bytes[upto] != otherBytes[otherUpto]) {
          return false;
        }
      }
      return true;
    } else {
      return false;
    }
  }

  @Override
  public Object clone() {
    return new BytesRef(this);
  }

  private boolean sliceEquals(BytesRef other, int pos) {
    if (pos < 0 || length - pos < other.length) {
      return false;
    }
    int i = offset + pos;
    int j = other.offset;
    final int k = other.offset + other.length;
    
    while (j < k) {
      if (bytes[i++] != other.bytes[j++]) {
        return false;
      }
    }
    
    return true;
  }
  
  public boolean startsWith(BytesRef other) {
    return sliceEquals(other, 0);
  }

  public boolean endsWith(BytesRef other) {
    return sliceEquals(other, length - other.length);
  }
  
  /** Calculates the hash code as required by TermsHash during indexing.
   * <p>It is defined as:
   * <pre>
   *  int hash = 0;
   *  for (int i = offset; i < offset + length; i++) {
   *    hash = 31*hash + bytes[i];
   *  }
   * </pre>
   */
  @Override
  public int hashCode() {
    int result = 0;
    final int end = offset + length;
    for(int i=offset;i<end;i++) {
      result = HASH_PRIME * result + bytes[i];
    }
    return result;
  }

  @Override
  public boolean equals(Object other) {
    if (other == null) {
      return false;
    }
    return this.bytesEquals((BytesRef) other);
  }

  /** Interprets stored bytes as UTF8 bytes, returning the
   *  resulting string */
  public String utf8ToString() {
    try {
      return new String(bytes, offset, length, "UTF-8");
    } catch (UnsupportedEncodingException uee) {
      // should not happen -- UTF8 is presumably supported
      // by all JREs
      throw new RuntimeException(uee);
    }
  }

  /** Returns hex encoded bytes, eg [0x6c 0x75 0x63 0x65 0x6e 0x65] */
  @Override
  public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append('[');
    final int end = offset + length;
    for(int i=offset;i<end;i++) {
      if (i > offset) {
        sb.append(' ');
      }
      sb.append(Integer.toHexString(bytes[i]&0xff));
    }
    sb.append(']');
    return sb.toString();
  }

  public void copy(BytesRef other) {
    if (bytes.length < other.length) {
      bytes = new byte[other.length];
    }
    System.arraycopy(other.bytes, other.offset, bytes, 0, other.length);
    length = other.length;
    offset = 0;
  }

  public void append(BytesRef other) {
    int newLen = length + other.length;
    if (bytes.length < newLen) {
      byte[] newBytes = new byte[newLen];
      System.arraycopy(bytes, offset, newBytes, 0, length);
      offset = 0;
      bytes = newBytes;
    }
    System.arraycopy(other.bytes, other.offset, bytes, length+offset, other.length);
    length = newLen;
  }

  public void grow(int newLength) {
    bytes = ArrayUtil.grow(bytes, newLength);
  }

  /** Unsigned byte order comparison */
  public int compareTo(BytesRef other) {
    if (this == other) return 0;

    final byte[] aBytes = this.bytes;
    int aUpto = this.offset;
    final byte[] bBytes = other.bytes;
    int bUpto = other.offset;

    final int aStop = aUpto + Math.min(this.length, other.length);

    while(aUpto < aStop) {
      int aByte = aBytes[aUpto++] & 0xff;
      int bByte = bBytes[bUpto++] & 0xff;
      int diff = aByte - bByte;
      if (diff != 0) return diff;
    }

    // One is a prefix of the other, or, they are equal:
    return this.length - other.length;
  }

  private final static Comparator<BytesRef> utf8SortedAsUnicodeSortOrder = new UTF8SortedAsUnicodeComparator();

  public static Comparator<BytesRef> getUTF8SortedAsUnicodeComparator() {
    return utf8SortedAsUnicodeSortOrder;
  }

  private static class UTF8SortedAsUnicodeComparator implements Comparator<BytesRef> {
    // Only singleton
    private UTF8SortedAsUnicodeComparator() {};

    public int compare(BytesRef a, BytesRef b) {
      final byte[] aBytes = a.bytes;
      int aUpto = a.offset;
      final byte[] bBytes = b.bytes;
      int bUpto = b.offset;
      
      final int aStop;
      if (a.length < b.length) {
        aStop = aUpto + a.length;
      } else {
        aStop = aUpto + b.length;
      }

      while(aUpto < aStop) {
        int aByte = aBytes[aUpto++] & 0xff;
        int bByte = bBytes[bUpto++] & 0xff;

        int diff = aByte - bByte;
        if (diff != 0) {
          return diff;
        }
      }

      // One is a prefix of the other, or, they are equal:
      return a.length - b.length;
    }    
  }

  private final static Comparator<BytesRef> utf8SortedAsUTF16SortOrder = new UTF8SortedAsUTF16Comparator();

  public static Comparator<BytesRef> getUTF8SortedAsUTF16Comparator() {
    return utf8SortedAsUTF16SortOrder;
  }

  private static class UTF8SortedAsUTF16Comparator implements Comparator<BytesRef> {
    // Only singleton
    private UTF8SortedAsUTF16Comparator() {};

    public int compare(BytesRef a, BytesRef b) {

      final byte[] aBytes = a.bytes;
      int aUpto = a.offset;
      final byte[] bBytes = b.bytes;
      int bUpto = b.offset;
      
      final int aStop;
      if (a.length < b.length) {
        aStop = aUpto + a.length;
      } else {
        aStop = aUpto + b.length;
      }

      while(aUpto < aStop) {
        int aByte = aBytes[aUpto++] & 0xff;
        int bByte = bBytes[bUpto++] & 0xff;

        if (aByte != bByte) {

          // See http://icu-project.org/docs/papers/utf16_code_point_order.html#utf-8-in-utf-16-order

          // We know the terms are not equal, but, we may
          // have to carefully fixup the bytes at the
          // difference to match UTF16's sort order:
          
          // NOTE: instead of moving supplementary code points (0xee and 0xef) to the unused 0xfe and 0xff, 
          // we move them to the unused 0xfc and 0xfd [reserved for future 6-byte character sequences]
          // this reserves 0xff for preflex's term reordering (surrogate dance), and if unicode grows such
          // that 6-byte sequences are needed we have much bigger problems anyway.
          if (aByte >= 0xee && bByte >= 0xee) {
            if ((aByte & 0xfe) == 0xee) {
              aByte += 0xe;
            }
            if ((bByte&0xfe) == 0xee) {
              bByte += 0xe;
            }
          }
          return aByte - bByte;
        }
      }

      // One is a prefix of the other, or, they are equal:
      return a.length - b.length;
    }
  }
}

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