content: // Protocol Buffers - Google's data interchange format
  // Copyright 2008 Google Inc.  All rights reserved.
  // https://developers.google.com/protocol-buffers/
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  // copyright notice, this list of conditions and the following disclaimer
  // in the documentation and/or other materials provided with the
  // distribution.
  //     * Neither the name of Google Inc. nor the names of its
  // contributors may be used to endorse or promote products derived from
  // this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  package com.google.protobuf;
  
  import static com.google.protobuf.Internal.EMPTY_BYTE_BUFFER;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.nio.ByteBuffer;
  import java.util.Iterator;
  
  class IterableByteBufferInputStream extends InputStream {
    /** The {@link Iterator} with type {@link ByteBuffer} of {@code input} */
    private Iterator<ByteBuffer> iterator;
    /** The current ByteBuffer; */
    private ByteBuffer currentByteBuffer;
    /** The number of ByteBuffers in the input data. */
    private int dataSize;
    /**
     * Current {@code ByteBuffer}'s index
     *
     * <p>If index equals dataSize, then all the data in the InputStream has been consumed
     */
    private int currentIndex;
    /** The current position for current ByteBuffer */
    private int currentByteBufferPos;
    /** Whether current ByteBuffer has an array */
    private boolean hasArray;
    /**
     * If the current ByteBuffer is unsafe-direct based, currentArray is null; otherwise should be the
     * array inside ByteBuffer.
     */
    private byte[] currentArray;
    /** Current ByteBuffer's array offset */
    private int currentArrayOffset;
    /**
     * If the current ByteBuffer is unsafe-direct based, currentAddress is the start address of this
     * ByteBuffer; otherwise should be zero.
     */
    private long currentAddress;
  
    IterableByteBufferInputStream(Iterable<ByteBuffer> data) {
      iterator = data.iterator();
      dataSize = 0;
      for (ByteBuffer unused : data) {
        dataSize++;
      }
      currentIndex = -1;
  
      if (!getNextByteBuffer()) {
        currentByteBuffer = EMPTY_BYTE_BUFFER;
        currentIndex = 0;
        currentByteBufferPos = 0;
        currentAddress = 0;
      }
    }
  
    private boolean getNextByteBuffer() {
      currentIndex++;
      if (!iterator.hasNext()) {
        return false;
      }
      currentByteBuffer = iterator.next();
      currentByteBufferPos = currentByteBuffer.position();
      if (currentByteBuffer.hasArray()) {
        hasArray = true;
        currentArray = currentByteBuffer.array();
        currentArrayOffset = currentByteBuffer.arrayOffset();
      } else {
        hasArray = false;
        currentAddress = UnsafeUtil.addressOffset(currentByteBuffer);
        currentArray = null;
      }
      return true;
    }
  
    private void updateCurrentByteBufferPos(int numberOfBytesRead) {
      currentByteBufferPos += numberOfBytesRead;
      if (currentByteBufferPos == currentByteBuffer.limit()) {
        getNextByteBuffer();
      }
    }
  
    @Override
    public int read() throws IOException {
      if (currentIndex == dataSize) {
        return -1;
      }
      if (hasArray) {
        int result = currentArray[currentByteBufferPos + currentArrayOffset] & 0xFF;
        updateCurrentByteBufferPos(1);
        return result;
      } else {
        int result = UnsafeUtil.getByte(currentByteBufferPos + currentAddress) & 0xFF;
        updateCurrentByteBufferPos(1);
        return result;
      }
    }
  
    @Override
    public int read(byte[] output, int offset, int length) throws IOException {
      if (currentIndex == dataSize) {
        return -1;
      }
      int remaining = currentByteBuffer.limit() - currentByteBufferPos;
      if (length > remaining) {
        length = remaining;
      }
      if (hasArray) {
        System.arraycopy(
            currentArray, currentByteBufferPos + currentArrayOffset, output, offset, length);
        updateCurrentByteBufferPos(length);
      } else {
        int prevPos = currentByteBuffer.position();
        currentByteBuffer.position(currentByteBufferPos);
        currentByteBuffer.get(output, offset, length);
        currentByteBuffer.position(prevPos);
        updateCurrentByteBufferPos(length);
      }
      return length;
    }
  }
  