DataOutput.java

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;
    }
  }

  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());
      }
    }
  }
}