HtmlAgilityPack 库 StackOverflowException 解决方案

     最近试用HtmlAgilityPack 来解析html，试用过程中程序会抛出StackOverflowException异常，从MSDN上可以看到，从 .NET Framework 2.0 版开始，将无法通过 try-catch 块捕获 StackOverflowException 对象，并且默认情况下将终止相应的进程。

 

    调查原因，发现，当一个html结构非常复杂时，HtmlAgilityPack 的递归次数会非常多，于是就报StackOverflowException异常，google了一下，找到下面的解决方案

首先，在库中新增一个类：

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

public class StackChecker {     public unsafe static bool HasSufficientStack(long bytes)     {         var stackInfo = new MEMORY_BASIC_INFORMATION();           // We subtract one page for our request. VirtualQuery rounds UP to the next page.         // Unfortunately, the stack grows down. If we're on the first page (last page in the         // VirtualAlloc), we'll be moved to the next page, which is off the stack! Note this         // doesn't work right for IA64 due to bigger pages.         IntPtr currentAddr = new IntPtr((uint)&stackInfo - 4096);           // Query for the current stack allocation information.         VirtualQuery(currentAddr, ref stackInfo, sizeof(MEMORY_BASIC_INFORMATION));           // If the current address minus the base (remember: the stack grows downward in the         // address space) is greater than the number of bytes requested plus the reserved         // space at the end, the request has succeeded.         return ((uint)currentAddr.ToInt64() - stackInfo.AllocationBase) >             (bytes + STACK_RESERVED_SPACE);     }       // We are conservative here. We assume that the platform needs a whole 16 pages to     // respond to stack overflow (using an x86/x64 page-size, not IA64). That's 64KB,     // which means that for very small stacks (e.g. 128KB) we'll fail a lot of stack checks     // incorrectly.     private const long STACK_RESERVED_SPACE = 4096 * 16;       [DllImport("kernel32.dll")]     private static extern int VirtualQuery(         IntPtr lpAddress,         ref MEMORY_BASIC_INFORMATION lpBuffer,         int dwLength);       private struct MEMORY_BASIC_INFORMATION     {         internal uint BaseAddress;         internal uint AllocationBase;         internal uint AllocationProtect;         internal uint RegionSize;         internal uint State;         internal uint Protect;         internal uint Type;     } }

 

然后，在递归次数较多的地方（such as HtmlNode.WriteTo(TextWriter outText) andHtmlNode.WriteTo(XmlWriter writer)):）添加下面的代码：

?

if (!StackChecker.HasSufficientStack(4*1024))

                throw new Exception("The document is too complex to parse");

 

OK，大功告成！

关注作者

欢迎关注作者微信公众号, 一起交流软件开发：