英文:
Go: How to receive a whole UDP Datagram
问题
我的问题：使用net.Read...方法只复制给定字节数组或切片大小的字节数。当然，我不想每次都分配最大的64 kB UDP数据报。
有没有一种go的方法可以确定数据报的大小（数据报头中的大小），或者重复读取直到完全读取数据报？
英文:
My Problem: With net.Read... Methods copy only the number of bytes of the size of the given byte-array or slice. I don't want to allocate the maximum UDP datagram of 64 kB every time of course.
Is there a go way to determine the size of the datagram (which is in the datagram header) or read again until the datagram is completely read?
答案1
得分: 2
尝试使用ReadFromUDP函数：
func (c *UDPConn) ReadFromUDP(b []byte) (n int, addr *UDPAddr, err error)
ReadFromUDP从连接c中读取一个UDP数据包，并将数据包的有效负载复制到b中。它返回复制到b中的字节数以及数据包的返回地址。
数据包的大小可以从n中获取，然后您可以使用它来定义一个自定义的切片（或其他数据结构）来存储数据报。这依赖于会话期间数据报大小不会改变，实际上它不应该改变。
英文:
Try ReadFromUDP:
func (c *UDPConn) ReadFromUDP(b []byte) (n int, addr *UDPAddr, err error)
>>ReadFromUDP reads a UDP packet from c, copying the payload into b. It returns the number of bytes copied into b and the return address that was on the packet.
The packet size should be available from n, which you can then use to define a custom slice (or other data structure) to store the datagrams in. This relies on the datagram size not changing during the session, which it really shouldn't.
答案2
得分: 0
通常在UDP协议中，数据包的大小是预先知道的，通常要小得多，大约为1.5k或更小。
你可以预先分配一个最大大小的静态缓冲区用于所有读取操作，然后一旦你知道从套接字读取的数据报的大小，就可以分配一个实际大小的字节数组，并将数据复制到其中。我认为你不能对同一个数据报进行额外的读取操作。
英文:
Usually in a UDP protocol packet sizes are known in advance, and it's usually much smaller, in the order of 1.5k or less.
What you can do is preallocate a maximum size static buffer for all reads, then once you know the size of the datagram you've read from the socket, allocate a byte array with the actual size and copy the data to it. I don't think you can do extra reads of the same datagram.
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