TFile.java 文件源码

/**
 * Constructor
 * 
 * @param reader
 *          The TFile reader object.
 * @param begin
 *          Begin location of the scan.
 * @param end
 *          End location of the scan.
 * @throws IOException
 */
Scanner(Reader reader, Location begin, Location end) throws IOException {
  this.reader = reader;
  // ensure the TFile index is loaded throughout the life of scanner.
  reader.checkTFileDataIndex();
  beginLocation = begin;
  endLocation = end;

  valTransferBuffer = new BytesWritable();
  // TODO: remember the longest key in a TFile, and use it to replace
  // MAX_KEY_SIZE.
  keyBuffer = new byte[MAX_KEY_SIZE];
  keyDataInputStream = new DataInputBuffer();
  valueBufferInputStream = new ChunkDecoder();
  valueDataInputStream = new DataInputStream(valueBufferInputStream);

  if (beginLocation.compareTo(endLocation) >= 0) {
    currentLocation = new Location(endLocation);
  } else {
    currentLocation = new Location(0, 0);
    initBlock(beginLocation.getBlockIndex());
    inBlockAdvance(beginLocation.getRecordIndex());
  }
}