c# - .NET 中的异步 XmlReader？

Question

有没有办法异步访问 XmlReader？ xml 是从许多不同的客户端(如 XMPP)中通过网络传入的；源源不断的<action>...</action > 标签。

我所追求的是能够使用类似 BeginRead/EndRead 的界面。我设法想出的最佳解决方案是在底层网络流上对 0 字节进行异步读取，然后当一些数据到达时，调用 XmlReader 上的 Read - 然而这将阻塞直到节点的所有数据变得可用。该解决方案大致如下所示

private Stream syncstream;
private NetworkStream ns;
private XmlReader reader;

//this code runs first
public void Init()
{
    syncstream = Stream.Synchronized(ns);
    reader = XmlReader.Create(syncstream);
    byte[] x = new byte[1];
    syncstream.BeginRead(x, 0, 0, new AsynchronousCallback(ReadCallback), null);
}

private void ReadCallback(IAsyncResult ar)
{
    syncstream.EndRead(ar);
    reader.Read(); //this will block for a while, until the entire node is available
    //do soemthing to the xml node
    byte[] x = new byte[1];
    syncstream.BeginRead(x, 0, 0, new AsynchronousCallback(ReadCallback), null);
}

编辑:如果字符串包含完整的 xml 节点，这是一种可能的算法吗？

Func<string, bool> nodeChecker = currentBuffer =>
                {
                    //if there is nothing, definetly no tag
                    if (currentBuffer == "") return false;
                    //if we have <![CDATA[ and not ]]>, hold on, else pass it on
                    if (currentBuffer.Contains("<![CDATA[") && !currentBuffer.Contains("]]>")) return false;
                    if (currentBuffer.Contains("<![CDATA[") && currentBuffer.Contains("]]>")) return true;
                    //these tag-related things will also catch <? ?> processing instructions
                    //if there is a < but no >, we still have an open tag
                    if (currentBuffer.Contains("<") && !currentBuffer.Contains(">")) return false;
                //if there is a <...>, we have a complete element.
                //>...< will never happen because we will pass it on to the parser when we get to >
                if (currentBuffer.Contains("<") && currentBuffer.Contains(">")) return true;
                //if there is no < >, we have a complete text node
                if (!currentBuffer.Contains("<") && !currentBuffer.Contains(">")) return true;
                //> and no < will never happen, we will pass it on to the parser when we get to >
                //by default, don't block
                return false;
            };

Answer 1

XmlReader 以 4kB block 的形式缓冲，如果我记得几年前我看过这个的话。您可以将入站数据填充到 4kB(恶心!)，或者使用更好的解析器。我通过将 James Clark 的 XP (Java) 作为 Jabber-Net 的一部分移植到 C# 来修复此问题，此处:

http://code.google.com/p/jabber-net/source/browse/#svn/trunk/xpnet

它是 LGPL，只处理 UTF8，没有打包使用，几乎没有文档，所以我不推荐使用它。 :)