在同一个 Stream 上启动多个异步读/写操作会损坏数据吗？
我使用异步 I/O，因为它不会阻塞调用线程并在幕后执行线程处理工作。如果我在同一个 Stream 上调用多个异步操作（例如 BeginWrite()），我是否需要担心数据缓冲区内容混合在一起？
假设我想发送 3 个缓冲区：
Buffer1: 1111111111
Buffer2: 2222222222
Buffer3: 3333333333
我不介意缓冲区是否以错误的顺序发送，所以
333333333311111111112222222222
没问题，但是缓冲区内容是否有可能完全混合在一起？
122213121212122333313111223333
PS：我100％确定有人已经以某种形式问过这个问题......
I'm using asynchronous I/O because it does not block the calling thread and does the threading stuff behind the scenes. If I invoke multiple async operations like BeginWrite()'s on the same Stream, should I need to worry about that data buffer contents are mixed together?
Let's assume I want to send 3 buffers:
Buffer1: 1111111111
Buffer2: 2222222222
Buffer3: 3333333333
I don't mind if the buffers are sent in incorrect order, so
333333333311111111112222222222
is ok, but is it possible that buffer contents are got completely mixed together?
122213121212122333313111223333
PS: I'm 100% sure that someone already asked this in some form...
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这取决于 Stream 的实现。例如，套接字支持多个重叠的读取和写入请求，文件 API 也是如此。它们保证每个操作的一致性（无交错内容）以及操作顺序：例如，对于套接字读取，接收到的字节将按照发布的顺序放置在发布的缓冲区中。如果不提供这些保证，就不可能编写高性能网络应用程序，因为重叠的发送是需要的，但重叠的接收实际上是高性能网络IO需要的。许多文章中都描述了此行为，包括好的 ole' Windows Sockets 2.0：使用完成端口编写可扩展的 Winsock 应用程序< /a> 并在 MSDN 重叠输入/输出：
毫不奇怪，同样的保证也适用于世界的托管端，例如。
NetworkStream类：话虽这么说，在流上随机进行异步读取和写入很快就会导致混乱。应用程序需要仔细编排线程提交操作的顺序，以便顺序具有确定性。通常，这意味着在（同步）列表中保留记帐，并在持有同步锁的同时特别小心地执行异步操作调用。
最后一点是，所有这些异步 API 在调用时都特别注意，完成的顺序不能保证与提交的顺序匹配。
It depends on the implementation of the Stream. For instance sockets support multiple overlapped requests both for read and for write, and so does the file API. They guarantee consistency of each operation (no interleaving content) and also order of operations: for instance for socket reads the bytes received will be placed in the buffers posted in the order posted. If these guarantees would not be provided it would impossible to write high performance network application, as overlapping Sends are desired but overlapping Receives are actually required for high performance network IO. This behavior is described in many articles, including good ole' Windows Sockets 2.0: Write Scalable Winsock Apps Using Completion Ports and is documented on MSDN Overlapped Input/Output:
Not surprisingly, the same guarantees carry over to the managed side of the world, eg. the
NetworkStreamclass:That being said, throwing randomly async reads and writes on a Stream will result in chaos pretty quickly. Applications need to carefully orchestrate the order in which threads submit the operations so that the order is deterministic. Usually this means keeping accounting in a (synchronized) list with special care to do the async operation invocation while holding the synchronization lock.
One final note is that all these async APIs make a special note in calling out that the order of completion is not guaranteed to match the order of submission.
不，文件流不支持多个并发 IO。 Windows 文件系统处理得不太好。它几乎肯定会抛出异常。
编辑：
同步和重叠输入和输出似乎指示文件系统将正确处理多个重叠的 IO 请求。我的不好。
但是，不要尝试对
FileStream进行并发同步写入。 这会引发异常。No, file streams do not support multiple concurrent IOs. The Windows file system does not handle that well. It will almost certainly throw an exception.
Edit:
Synchronization and Overlapped Input and Output seems to indicate that the file system will correctly handle multiple overlapped IO requests. My bad.
Do not, however, try to do concurrent synchronous writes on a
FileStream. That throws an exception.