将字节从一个ByteBuffer传输到另一个ByteBuffer [英] transferring bytes from one ByteBuffer to another

问题描述

将ByteBuffer bbuf_src 中尽可能多的字节放入另一个ByteBuffer bbuf_dest 的最有效方法是什么？以及知道传输了多少字节）？我正在尝试 bbuf_dest.put（bbuf_src）但似乎想要抛出一个BufferOverflowException，我现在无法从Sun获取javadoc（网络问题）需要它们。 > :( argh。

What's the most efficient way to put as many bytes as possible from a ByteBuffer bbuf_src into another ByteBuffer bbuf_dest (as well as know how many bytes were transferred)? I'm trying bbuf_dest.put(bbuf_src) but it seems to want to throw a BufferOverflowException and I can't get the javadocs from Sun right now (network problems) when I need them. >:( argh.

编辑：darnit，@ Richard的方法（使用来自<$的支持数组的put（）如果bbuf_src是一个ReadOnly缓冲区，则c $ c> bbuf_src ）将无效。因为你无法访问该数组。在这种情况下我该怎么办???

edit: darnit, @Richard's approach (use put() from the backing array of bbuf_src) won't work if bbuf_src is a ReadOnly buffer, as you can't get access to that array. What can I do in that case???

推荐答案

好的，我改编了@ Richard的回答：

OK, I've adapted @Richard's answer:

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;
}

以及确保其有效的测试：

and a test to make sure it works:

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;
}

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