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Lucene example source code file (DataOutput.java)

This example Lucene source code file (DataOutput.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, copy_buffer_size, copy_buffer_size, dataoutput, deprecated, deprecated, io, ioexception, ioexception, string, util

The Lucene DataOutput.java source code

package org.apache.lucene.store;

/**
 * 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.io.IOException;
import java.util.Map;

import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.UnicodeUtil;

/**
 * Abstract base class for performing write operations of Lucene's low-level
 * data types.
 */
public abstract class DataOutput {

  /** Writes a single byte.
   * @see IndexInput#readByte()
   */
  public abstract void writeByte(byte b) throws IOException;

  /** Writes an array of bytes.
   * @param b the bytes to write
   * @param length the number of bytes to write
   * @see DataInput#readBytes(byte[],int,int)
   */
  public void writeBytes(byte[] b, int length) throws IOException {
    writeBytes(b, 0, length);
  }

  /** Writes an array of bytes.
   * @param b the bytes to write
   * @param offset the offset in the byte array
   * @param length the number of bytes to write
   * @see DataInput#readBytes(byte[],int,int)
   */
  public abstract void writeBytes(byte[] b, int offset, int length) throws IOException;

  /** Writes an int as four bytes.
   * @see DataInput#readInt()
   */
  public void writeInt(int i) throws IOException {
    writeByte((byte)(i >> 24));
    writeByte((byte)(i >> 16));
    writeByte((byte)(i >>  8));
    writeByte((byte) i);
  }

  /** Writes an int in a variable-length format.  Writes between one and
   * five bytes.  Smaller values take fewer bytes.  Negative numbers are not
   * supported.
   * @see DataInput#readVInt()
   */
  public final void writeVInt(int i) throws IOException {
    while ((i & ~0x7F) != 0) {
      writeByte((byte)((i & 0x7f) | 0x80));
      i >>>= 7;
    }
    writeByte((byte)i);
  }

  /** Writes a long as eight bytes.
   * @see DataInput#readLong()
   */
  public void writeLong(long i) throws IOException {
    writeInt((int) (i >> 32));
    writeInt((int) i);
  }

  /** Writes an long in a variable-length format.  Writes between one and nine
   * bytes.  Smaller values take fewer bytes.  Negative numbers are not
   * supported.
   * @see DataInput#readVLong()
   */
  public final void writeVLong(long i) throws IOException {
    while ((i & ~0x7F) != 0) {
      writeByte((byte)((i & 0x7f) | 0x80));
      i >>>= 7;
    }
    writeByte((byte)i);
  }

  /** Writes a string.
   * @see DataInput#readString()
   */
  public void writeString(String s) throws IOException {
    final BytesRef utf8Result = new BytesRef(10);
    UnicodeUtil.UTF16toUTF8(s, 0, s.length(), utf8Result);
    writeVInt(utf8Result.length);
    writeBytes(utf8Result.bytes, 0, utf8Result.length);
  }

  private static int COPY_BUFFER_SIZE = 16384;
  private byte[] copyBuffer;

  /** Copy numBytes bytes from input to ourself. */
  public void copyBytes(DataInput input, long numBytes) throws IOException {
    assert numBytes >= 0: "numBytes=" + numBytes;
    long left = numBytes;
    if (copyBuffer == null)
      copyBuffer = new byte[COPY_BUFFER_SIZE];
    while(left > 0) {
      final int toCopy;
      if (left > COPY_BUFFER_SIZE)
        toCopy = COPY_BUFFER_SIZE;
      else
        toCopy = (int) left;
      input.readBytes(copyBuffer, 0, toCopy);
      writeBytes(copyBuffer, 0, toCopy);
      left -= toCopy;
    }
  }

  /** Writes a sub sequence of characters from s as the old
   *  format (modified UTF-8 encoded bytes).
   * @param s the source of the characters
   * @param start the first character in the sequence
   * @param length the number of characters in the sequence
   * @deprecated -- please pre-convert to utf8 bytes
   * instead or use {@link #writeString}
   */
  @Deprecated
  public void writeChars(String s, int start, int length)
       throws IOException {
    final int end = start + length;
    for (int i = start; i < end; i++) {
      final int code = s.charAt(i);
      if (code >= 0x01 && code <= 0x7F)
	writeByte((byte)code);
      else if (((code >= 0x80) && (code <= 0x7FF)) || code == 0) {
	writeByte((byte)(0xC0 | (code >> 6)));
	writeByte((byte)(0x80 | (code & 0x3F)));
      } else {
	writeByte((byte)(0xE0 | (code >>> 12)));
	writeByte((byte)(0x80 | ((code >> 6) & 0x3F)));
	writeByte((byte)(0x80 | (code & 0x3F)));
      }
    }
  }

  /** Writes a sub sequence of characters from char[] as
   *  the old format (modified UTF-8 encoded bytes).
   * @param s the source of the characters
   * @param start the first character in the sequence
   * @param length the number of characters in the sequence
   * @deprecated -- please pre-convert to utf8 bytes instead or use {@link #writeString}
   */
  @Deprecated
  public void writeChars(char[] s, int start, int length)
    throws IOException {
    final int end = start + length;
    for (int i = start; i < end; i++) {
      final int code = s[i];
      if (code >= 0x01 && code <= 0x7F)
	writeByte((byte)code);
      else if (((code >= 0x80) && (code <= 0x7FF)) || code == 0) {
	writeByte((byte)(0xC0 | (code >> 6)));
	writeByte((byte)(0x80 | (code & 0x3F)));
      } else {
	writeByte((byte)(0xE0 | (code >>> 12)));
	writeByte((byte)(0x80 | ((code >> 6) & 0x3F)));
	writeByte((byte)(0x80 | (code & 0x3F)));
      }
    }
  }

  public void writeStringStringMap(Map<String,String> map) throws IOException {
    if (map == null) {
      writeInt(0);
    } else {
      writeInt(map.size());
      for(final Map.Entry<String, String> entry: map.entrySet()) {
        writeString(entry.getKey());
        writeString(entry.getValue());
      }
    }
  }
}

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