SegmentTermPositions(SegmentReader p) 
{
  
    super(p);
    this.proxStream = null;  // the proxStream will be cloned lazily when nextPosition() is called for the first time
}

 public final  void close() throws IOException 
{
    super.close();
    if (proxStream != null) proxStream.close();
}

 public byte[] getPayload(byte[] data,
    int offset) throws IOException 
{
    if (!needToLoadPayload) {
      throw new IOException("Payload cannot be loaded more than once for the same term position.");
    }
    // read payloads lazily
    byte[] retArray;
    int retOffset;
    if (data == null || data.length - offset <  payloadLength) {
      // the array is too small to store the payload data,
      // so we allocate a new one
      retArray = new byte[payloadLength];
      retOffset = 0;
    } else {
      retArray = data;
      retOffset = offset;
    }
    proxStream.readBytes(retArray, retOffset, payloadLength);
    needToLoadPayload = false;
    return retArray;
}

 public int getPayloadLength() 
{
    return payloadLength;
}

 public boolean isPayloadAvailable() 
{
    return needToLoadPayload && payloadLength  > 0;
}

 public final boolean next() throws IOException 
{
    // we remember to skip the remaining positions of the current
    // document lazily
    lazySkipProxCount += proxCount;
    if (super.next()) {               // run super
      proxCount = freq;               // note frequency
      position = 0;               // reset position
      return true;
    }
    return false;
}

 public final int nextPosition() throws IOException 
{
    // perform lazy skips if neccessary
    lazySkip();
    proxCount--;
    return position += readDeltaPosition();
}

 public final int read(int[] docs,
    int[] freqs) 
{
    throw new UnsupportedOperationException("TermPositions does not support processing multiple documents in one call. Use TermDocs instead.");
}

 final  void seek(TermInfo ti,
    Term term) throws IOException 
{
    super.seek(ti, term);
    if (ti != null)
      lazySkipPointer = ti.proxPointer;
    lazySkipProxCount = 0;
    proxCount = 0;
    payloadLength = 0;
    needToLoadPayload = false;
}

 protected  void skipProx(long proxPointer,
    int payloadLength) throws IOException 
{
    // we save the pointer, we might have to skip there lazily
    lazySkipPointer = proxPointer;
    lazySkipProxCount = 0;
    proxCount = 0;
    this.payloadLength = payloadLength;
    needToLoadPayload = false;
}

Called by super.skipTo().

 protected final  void skippingDoc() throws IOException 
{
    // we remember to skip a document lazily
    lazySkipProxCount += freq;
}