Easy to check recursion

墨蓝 2021-12-11 00:47 161阅读 0赞

Introduct  
(This article is translate version , original version written in chinese , you can see it at [http://www.cnblogs.com/xdesigner/archive/2006/08/02/465483.html][http_www.cnblogs.com_xdesigner_archive_2006_08_02_465483.html] )  
  I bring out a easy to check recursion , just call an universal function .  
  When we develop complex software , maybe handle recursion , for example , some code modify object1's data , then object2's data has been modified automatic . but when code modify object2's data , then object1's data has been modified automatic too , so there are a recursion , if this recursion is un-control , then system must throw out StackOverflowException . I think somebody must meet this thing .  
  Against this recursion cycle , It is nature to define a flag variable and use this variable to check recursion . When system modify object1's data , before modify , check this flat , if this flat has been set , then cancel modify operation , else , set this flag , modify object1's data , after modify operation , clear this flag . In this way , you can check recursion and avoid recursion cycle .  
  But in this way , you must define flag varible and maintains this flag , when system modify object's data and throw out exception , forget clear flag, then system can not modify object's data for ever.This is not expediently .  
  At there , I bring out a method to resolve this proplem . In fact , we can use system callback stack to check resursion . In .net software , we can get current thread's call stack from  type System.Diagnostics.StackTrace . StackTract's FrameCount property means stack layer count , and GetFrame function returns StackFrame object which maintains single stack layer's information , we can enumerate all call stack and check recursion . So I write a universal function to check recursion as following

/// <summary>  
/// Check the parent function has recursion  
/// </summary>  
/// <returns>If recursion return true , else return false </returns>  
public static bool CheckRecursion()  
\{  
    System.Diagnostics.StackTrace myTrace = new System.Diagnostics.StackTrace();  
    // If stack layer count less 3 , recursion impossible.  
    if (myTrace.FrameCount < 3)  
        return false;  
    System.IntPtr mh = myTrace.GetFrame(1).GetMethod().MethodHandle.Value;  
    for (int iCount = 2; iCount < myTrace.FrameCount; iCount++)  
    \{  
        System.Reflection.MethodBase m = myTrace.GetFrame(iCount).GetMethod();  
        if (m.MethodHandle.Value == mh)  
        \{  
            return true;  
        \}  
    \}  
    return false;  
\}

you can use this function anywhere , for example

void SomeFunction()// some function can not recursion  
\{  
   if( CheckRecursion())  
      return ;  
   //........ some code  
\}

We can expend this function , for example , where an universal function to return how many times recursion.  
  This function is easy to use , but I test that it is run slowly , so I suggest you can not use it continual . When you must check recursion continual , you have to define flag variable and check recursion fast .  
  XDesigner Studio ( [http://www.xdesigner.cn/default-eng.htm][http_www.xdesigner.cn_default-eng.htm] ) 2006-10-10

转载于:https://www.cnblogs.com/xdesigner/archive/2006/10/10/524963.html

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