将字节从一个ByteBuffer传输到另一个

Question

将尽可能多的字节从ByteBuffer bbuf_src放入另一个ByteBuffer
的最有效方法是什么bbuf_dest（以及知道传输了多少字节）？我正在尝试，bbuf_dest.put(bbuf_src)但似乎要抛出BufferOverflowException，当我需要它们时，我现在无法从Sun获取Javadocs（网络问题）。>
:( argh。

编辑：darnit，bbuf_src如果bbuf_src是ReadOnly缓冲区，则@Richard
的方法（使用来自backing数组的put（））将不起作用，因为您无法访问该数组。在那种情况下我该怎么办？

Answer 1

好吧，我已经适应了@Richard的答案：

public static int transferAsMuchAsPossible(
                     ByteBuffer bbuf_dest, ByteBuffer bbuf_src)
{
  int nTransfer = Math.min(bbuf_dest.remaining(), bbuf_src.remaining());
  if (nTransfer > 0)
  {
    bbuf_dest.put(bbuf_src.array(), 
                  bbuf_src.arrayOffset()+bbuf_src.position(), 
                  nTransfer);
    bbuf_src.position(bbuf_src.position()+nTransfer);
  }
  return nTransfer;
}

并进行测试以确保其有效：

public static boolean transferTest()
{
    ByteBuffer bb1 = ByteBuffer.allocate(256);
    ByteBuffer bb2 = ByteBuffer.allocate(50);
    for (int i = 0; i < 100; ++i)
    {
        bb1.put((byte)i);
    }
    bb1.flip();
    bb1.position(5);
    ByteBuffer bb1a = bb1.slice();
    bb1a.position(2);
    // bb3 includes the 5-100 range
    bb2.put((byte)77);
    // something to see this works when bb2 isn't empty
    int n = transferAsMuchAsPossible(bb2, bb1a);
    boolean itWorked = (n == 49);

    if (bb1a.position() != 51)
        itWorked = false;
    if (bb2.position() != 50)
        itWorked = false;
    bb2.rewind();
    if (bb2.get() != 77)
        itWorked = false;
    for (int i = 0; i < 49; ++i)
    {
        if (bb2.get() != i+7)
        {
            itWorked = false;
            break;
        }
    }
    return itWorked;
}