private synchronized void fallbackByteBufferReadFully()

in hadoop-api-shim/src/main/java/org/apache/hadoop/fs/shim/impl/FSDataInputStreamShimImpl.java [241:290]
38 lines of code
7 McCabe index (conditional complexity)

  private synchronized void fallbackByteBufferReadFully(long position, ByteBuffer buf)
      throws IOException {
    FSDataInputStream in = getInstance();
    int len = buf.remaining();
    LOG.debug("read @{} {} bytes", position, len);
    // position to return to.
    if (buf.hasArray()) {
      readIntoArrayByteBufferThroughReadFully(position, buf, len);
      return;
    }
    // no array.
    // is the inner stream ByteBufferReadable? if so, read
    // through that then seek back.
    if (isByteBufferReadableAvailable.get()) {
      LOG.debug("reading bytebuffer through seek and read(ByteBuffer)");
      try (SeekToThenBack back = new SeekToThenBack(position)) {
        while (buf.remaining() > 0) {
          int bytesRead = in.read(buf);
          if (bytesRead < 0) {
            throw new EOFException("No more data in stream; needed "
                + buf.remaining() + " to complete the read");
          }
        }
        return;
      } catch (UnsupportedOperationException ex) {
        LOG.debug("stream does not support ByteBufferReadable", ex);
        // don't try using this again
        isByteBufferReadableAvailable.set(false);
        /* and fall through into the final strategy */
      }
    }

    // final strategy.
    // buffer isn't an array, so need to create a smaller one then read via a series of readFully
    // calls.
    LOG.debug("Reading the byte buffer by reading into an array and copying");
    int bufferSize = Math.min(len, TEMPORARY_BUFFER);
    byte[] byteArray = new byte[bufferSize];
    long nextReadPosition = position;
    while (buf.remaining() > 0) {
      int bytesToRead = Math.min(bufferSize, buf.remaining());
      LOG.debug("Reading {} bytes from {}", bytesToRead, nextReadPosition);
      getInstance().readFully(nextReadPosition, byteArray, 0,
          bytesToRead);
      buf.put(byteArray, 0, bytesToRead);
      // move forward in the file
      nextReadPosition += bytesToRead;
    }

  }