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  • operator[][] C++

    - by bobobobo
    I'd like to overload operator[][] to give internal access to a 2D array of char in C++. Right now I'm only overloading operator[], which goes something like class Object { char ** charMap ; char* operator[]( int row ) { return charMap[row] ; } } ; It works ok.. Is it possible to override operator[][] though?

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  • is it possible to get the class of the interface <Set>

    - by user1164885
    Am having some arguments say (String a, Treeset b, Set c) and i try to get the class by arguments[i].getClass(); of the above arguments.. is it possible to get the class of the interface . ex., Class[] argumentTypes = new Class [arguments.length]; for (int i = 0 ; i < arguments.length ; i++) { argumentTypes[i] = arguments[i].getClass(); }

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  • Is objective C 2.0 a proper superset of C?

    - by RankWeis
    I've heard that objective-C is a proper superset of C, but is objective-C 2.0? The reason I ask is that either it isn't, or I misunderstand the phrase 'proper superset', because this code is valid C syntax: import int main () { char *nil = "hello"; printf("%s\n",nil); } But does not compile in Objective-C 2.0. Obviously, this is an easily fixable problem, but I'm writing a paper, and feel that this is something that should be pointed out.

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  • g++ creates several symbols of a const ?

    - by nissen
    In one of my header (C++) files I changed #define TIMEOUT 10 to the more(?) C++ way: const int TIMEOUT = 10; It seems however, g++(v 4.4.3) now includes this symbol several times in the binary. $ nm -C build/ipd/ipd |head 08050420 T ToUnixTime 08050470 T ParseTime 080504c0 T ParseISOTime 080518e4 r TIMEOUT 080518ec r TIMEOUT 080518f4 r TIMEOUT 080518fc r TIMEOUT 080503e0 T HandleMessage How come ?

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  • DirectorySearch.PageSize = 2 doesn't work

    - by Bero
    using (DirectorySearcher srch = new DirectorySearcher(String.Format("(memberOf= {0})",p_Target.DistinguishedName))) { srch.PageSize = 2; SearchResultCollection results = results = srch.FindAll(); int count = results.Count; } count = 3 (THREE) and not 2. Why is that? I don't want to have all results in just one page. I know that PageSize = 2 is silly small but I set that value in this case just for testing purpose (in reality it will be more).

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  • Accessing variables in other classes (Java)

    - by George
    Why doesn't the following program return 0, since I am accessing p from a new A(), which has not had main called on it? public class A { public int p = 0; public static void main(String[] args) { p = Integer.parseInt(args[0]); new B().go(); } } class B { public void go() { System.out.println(new A().p); } }

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  • Why Chrome modifies IDT?

    - by muslon
    Chrome 4.0.266.0, Rootkit Unhooker 3.7.300.503. Iff Chrome is running, RkUnhooker shows in Code Hooks: IDT--Int 0x000000B1 0x863DDDD4 - [unknown_irp_handler] IDT modification Why does Chrome modifies IDT?

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  • Boost MultiIndex - objects or pointers (and how to use them?)?

    - by Sarah
    I'm programming an agent-based simulation and have decided that Boost's MultiIndex is probably the most efficient container for my agents. I'm not a professional programmer, and my background is very spotty. I've two questions: Is it better to have the container contain the agents (of class Host) themselves, or is it more efficient for the container to hold Host *? Hosts will sometimes be deleted from memory (that's my plan, anyway... need to read up on new and delete). Hosts' private variables will get updated occasionally, which I hope to do through the modify function in MultiIndex. There will be no other copies of Hosts in the simulation, i.e., they will not be used in any other containers. If I use pointers to Hosts, how do I set up the key extraction properly? My code below doesn't compile. // main.cpp - ATTEMPTED POINTER VERSION ... #include <boost/multi_index_container.hpp> #include <boost/multi_index/hashed_index.hpp> #include <boost/multi_index/member.hpp> #include <boost/multi_index/ordered_index.hpp> #include <boost/multi_index/mem_fun.hpp> #include <boost/tokenizer.hpp> typedef multi_index_container< Host *, indexed_by< // hash by Host::id hashed_unique< BOOST_MULTI_INDEX_MEM_FUN(Host,int,Host::getID) > // arg errors here > // end indexed_by > HostContainer; ... int main() { ... HostContainer testHosts; Host * newHostPtr; newHostPtr = new Host( t, DOB, idCtr, 0, currentEvents ); testHosts.insert( newHostPtr ); ... } I can't find a precisely analogous example in the Boost documentation, and my knowledge of C++ syntax is still very weak. The code does appear to work when I replace all the pointer references with the class objects themselves. As best I can read it, the Boost documentation (see summary table at bottom) implies I should be able to use member functions with pointer elements.

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  • C++ sort method

    - by qwead
    I want to sort a vector using std::sort, but my sort method is a static method of a class, and I want to call std::sort outside it, but it seems to be trouble doing it this way. On the class: static int CompareIt(void *sol1, void *sol2) { ... } std::sort call: sort(distanceList.at(q).begin(), distanceList.at(q).end(), &DistanceNodeComparator::CompareIt); Shouldn't it be possible to do this way?

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  • Targeting all subclassed CCSprites (cocos2d)

    - by Joethemonkey101
    I'm working on a method to end the level, but to do so, I have to see that all of the enemy character have been killed. If my enemies are CCSprites, how do I make a method that detects if all of them are dead? I'm tracking their health with an int called enemyHp. For example, this is an if statement I made to remove the enemy if (enemy.enemyHp <= 0) { To recap - I want to make a method that detects when all enemies have been killed. Thanks

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  • C++: Enum or #define

    - by sub
    I'm building a toy interpreter and I have implemented a token class which holds the token type and value. The token type is usually an integer, but how should I abstract the int's? What would be the better idea: // #defines #define T_NEWLINE 1; #define T_STRING 2; #define T_BLAH 3; /** * Or... */ // enum enum TokenTypes { t_newline, t_string, t_blah };

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  • When I do ""+1 I get a String - Why

    - by steve
    Hi, Please understand firstly that I fully understand that Java will return a String when I use ""+int. What I'm really not sure about is what exactly is happening down at the memory aspect. How exactly is java performing this conversion. I mean this in a very indepth way, not 'auto boxing' or anything like that :) I'm hoping someone with a deeper understanding can explain what exactly is done.

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  • Understanding Request Validation in ASP.NET MVC 3

    - by imran_ku07
         Introduction:             A fact that you must always remember "never ever trust user inputs". An application that trusts user inputs may be easily vulnerable to XSS, XSRF, SQL Injection, etc attacks. XSS and XSRF are very dangerous attacks. So to mitigate these attacks ASP.NET introduced request validation in ASP.NET 1.1. During request validation, ASP.NET will throw HttpRequestValidationException: 'A potentially dangerous XXX value was detected from the client', if he found, < followed by an exclamation(like <!) or < followed by the letters a through z(like <s) or & followed by a pound sign(like &#123) as a part of query string, posted form and cookie collection. In ASP.NET 4.0, request validation becomes extensible. This means that you can extend request validation. Also in ASP.NET 4.0, by default request validation is enabled before the BeginRequest phase of an HTTP request. ASP.NET MVC 3 moves one step further by making request validation granular. This allows you to disable request validation for some properties of a model while maintaining request validation for all other cases. In this article I will show you the use of request validation in ASP.NET MVC 3. Then I will briefly explain the internal working of granular request validation.       Description:             First of all create a new ASP.NET MVC 3 application. Then create a simple model class called MyModel,     public class MyModel { public string Prop1 { get; set; } public string Prop2 { get; set; } }             Then just update the index action method as follows,   public ActionResult Index(MyModel p) { return View(); }             Now just run this application. You will find that everything works just fine. Now just append this query string ?Prop1=<s to the url of this application, you will get the HttpRequestValidationException exception.           Now just decorate the Index action method with [ValidateInputAttribute(false)],   [ValidateInput(false)] public ActionResult Index(MyModel p) { return View(); }             Run this application again with same query string. You will find that your application run without any unhandled exception.           Up to now, there is nothing new in ASP.NET MVC 3 because ValidateInputAttribute was present in the previous versions of ASP.NET MVC. Any problem with this approach? Yes there is a problem with this approach. The problem is that now users can send html for both Prop1 and Prop2 properties and a lot of developers are not aware of it. This means that now everyone can send html with both parameters(e.g, ?Prop1=<s&Prop2=<s). So ValidateInput attribute does not gives you the guarantee that your application is safe to XSS or XSRF. This is the reason why ASP.NET MVC team introduced granular request validation in ASP.NET MVC 3. Let's see this feature.           Remove [ValidateInputAttribute(false)] on Index action and update MyModel class as follows,   public class MyModel { [AllowHtml] public string Prop1 { get; set; } public string Prop2 { get; set; } }             Note that AllowHtml attribute is only decorated on Prop1 property. Run this application again with ?Prop1=<s query string. You will find that your application run just fine. Run this application again with ?Prop1=<s&Prop2=<s query string, you will get HttpRequestValidationException exception. This shows that the granular request validation in ASP.NET MVC 3 only allows users to send html for properties decorated with AllowHtml attribute.            Sometimes you may need to access Request.QueryString or Request.Form directly. You may change your code as follows,   [ValidateInput(false)] public ActionResult Index() { var prop1 = Request.QueryString["Prop1"]; return View(); }             Run this application again, you will get the HttpRequestValidationException exception again even you have [ValidateInput(false)] on your Index action. The reason is that Request flags are still not set to unvalidate. I will explain this later. For making this work you need to use Unvalidated extension method,     public ActionResult Index() { var q = Request.Unvalidated().QueryString; var prop1 = q["Prop1"]; return View(); }             Unvalidated extension method is defined in System.Web.Helpers namespace . So you need to add using System.Web.Helpers; in this class file. Run this application again, your application run just fine.             There you have it. If you are not curious to know the internal working of granular request validation then you can skip next paragraphs completely. If you are interested then carry on reading.             Create a new ASP.NET MVC 2 application, then open global.asax.cs file and the following lines,     protected void Application_BeginRequest() { var q = Request.QueryString; }             Then make the Index action method as,    [ValidateInput(false)] public ActionResult Index(string id) { return View(); }             Please note that the Index action method contains a parameter and this action method is decorated with [ValidateInput(false)]. Run this application again, but now with ?id=<s query string, you will get HttpRequestValidationException exception at Application_BeginRequest method. Now just add the following entry in web.config,   <httpRuntime requestValidationMode="2.0"/>             Now run this application again. This time your application will run just fine. Now just see the following quote from ASP.NET 4 Breaking Changes,   In ASP.NET 4, by default, request validation is enabled for all requests, because it is enabled before the BeginRequest phase of an HTTP request. As a result, request validation applies to requests for all ASP.NET resources, not just .aspx page requests. This includes requests such as Web service calls and custom HTTP handlers. Request validation is also active when custom HTTP modules are reading the contents of an HTTP request.             This clearly state that request validation is enabled before the BeginRequest phase of an HTTP request. For understanding what does enabled means here, we need to see HttpRequest.ValidateInput, HttpRequest.QueryString and HttpRequest.Form methods/properties in System.Web assembly. Here is the implementation of HttpRequest.ValidateInput, HttpRequest.QueryString and HttpRequest.Form methods/properties in System.Web assembly,     public NameValueCollection Form { get { if (this._form == null) { this._form = new HttpValueCollection(); if (this._wr != null) { this.FillInFormCollection(); } this._form.MakeReadOnly(); } if (this._flags[2]) { this._flags.Clear(2); this.ValidateNameValueCollection(this._form, RequestValidationSource.Form); } return this._form; } } public NameValueCollection QueryString { get { if (this._queryString == null) { this._queryString = new HttpValueCollection(); if (this._wr != null) { this.FillInQueryStringCollection(); } this._queryString.MakeReadOnly(); } if (this._flags[1]) { this._flags.Clear(1); this.ValidateNameValueCollection(this._queryString, RequestValidationSource.QueryString); } return this._queryString; } } public void ValidateInput() { if (!this._flags[0x8000]) { this._flags.Set(0x8000); this._flags.Set(1); this._flags.Set(2); this._flags.Set(4); this._flags.Set(0x40); this._flags.Set(0x80); this._flags.Set(0x100); this._flags.Set(0x200); this._flags.Set(8); } }             The above code indicates that HttpRequest.QueryString and HttpRequest.Form will only validate the querystring and form collection if certain flags are set. These flags are automatically set if you call HttpRequest.ValidateInput method. Now run the above application again(don't forget to append ?id=<s query string in the url) with the same settings(i.e, requestValidationMode="2.0" setting in web.config and Application_BeginRequest method in global.asax.cs), your application will run just fine. Now just update the Application_BeginRequest method as,   protected void Application_BeginRequest() { Request.ValidateInput(); var q = Request.QueryString; }             Note that I am calling Request.ValidateInput method prior to use Request.QueryString property. ValidateInput method will internally set certain flags(discussed above). These flags will then tells the Request.QueryString (and Request.Form) property that validate the query string(or form) when user call Request.QueryString(or Request.Form) property. So running this application again with ?id=<s query string will throw HttpRequestValidationException exception. Now I hope it is clear to you that what does requestValidationMode do. It just tells the ASP.NET that not invoke the Request.ValidateInput method internally before the BeginRequest phase of an HTTP request if requestValidationMode is set to a value less than 4.0 in web.config. Here is the implementation of HttpRequest.ValidateInputIfRequiredByConfig method which will prove this statement(Don't be confused with HttpRequest and Request. Request is the property of HttpRequest class),    internal void ValidateInputIfRequiredByConfig() { ............................................................... ............................................................... ............................................................... ............................................................... if (httpRuntime.RequestValidationMode >= VersionUtil.Framework40) { this.ValidateInput(); } }              Hopefully the above discussion will clear you how requestValidationMode works in ASP.NET 4. It is also interesting to note that both HttpRequest.QueryString and HttpRequest.Form only throws the exception when you access them first time. Any subsequent access to HttpRequest.QueryString and HttpRequest.Form will not throw any exception. Continuing with the above example, just update Application_BeginRequest method in global.asax.cs file as,   protected void Application_BeginRequest() { try { var q = Request.QueryString; var f = Request.Form; } catch//swallow this exception { } var q1 = Request.QueryString; var f1 = Request.Form; }             Without setting requestValidationMode to 2.0 and without decorating ValidateInput attribute on Index action, your application will work just fine because both HttpRequest.QueryString and HttpRequest.Form will clear their flags after reading HttpRequest.QueryString and HttpRequest.Form for the first time(see the implementation of HttpRequest.QueryString and HttpRequest.Form above).           Now let's see ASP.NET MVC 3 granular request validation internal working. First of all we need to see type of HttpRequest.QueryString and HttpRequest.Form properties. Both HttpRequest.QueryString and HttpRequest.Form properties are of type NameValueCollection which is inherited from the NameObjectCollectionBase class. NameObjectCollectionBase class contains _entriesArray, _entriesTable, NameObjectEntry.Key and NameObjectEntry.Value fields which granular request validation uses internally. In addition granular request validation also uses _queryString, _form and _flags fields, ValidateString method and the Indexer of HttpRequest class. Let's see when and how granular request validation uses these fields.           Create a new ASP.NET MVC 3 application. Then put a breakpoint at Application_BeginRequest method and another breakpoint at HomeController.Index method. Now just run this application. When the break point inside Application_BeginRequest method hits then add the following expression in quick watch window, System.Web.HttpContext.Current.Request.QueryString. You will see the following screen,                                              Now Press F5 so that the second breakpoint inside HomeController.Index method hits. When the second breakpoint hits then add the following expression in quick watch window again, System.Web.HttpContext.Current.Request.QueryString. You will see the following screen,                            First screen shows that _entriesTable field is of type System.Collections.Hashtable and _entriesArray field is of type System.Collections.ArrayList during the BeginRequest phase of the HTTP request. While the second screen shows that _entriesTable type is changed to Microsoft.Web.Infrastructure.DynamicValidationHelper.LazilyValidatingHashtable and _entriesArray type is changed to Microsoft.Web.Infrastructure.DynamicValidationHelper.LazilyValidatingArrayList during executing the Index action method. In addition to these members, ASP.NET MVC 3 also perform some operation on _flags, _form, _queryString and other members of HttpRuntime class internally. This shows that ASP.NET MVC 3 performing some operation on the members of HttpRequest class for making granular request validation possible.           Both LazilyValidatingArrayList and LazilyValidatingHashtable classes are defined in the Microsoft.Web.Infrastructure assembly. You may wonder why their name starts with Lazily. The fact is that now with ASP.NET MVC 3, request validation will be performed lazily. In simple words, Microsoft.Web.Infrastructure assembly is now taking the responsibility for request validation from System.Web assembly. See the below screens. The first screen depicting HttpRequestValidationException exception in ASP.NET MVC 2 application while the second screen showing HttpRequestValidationException exception in ASP.NET MVC 3 application.   In MVC 2:                 In MVC 3:                          The stack trace of the second screenshot shows that Microsoft.Web.Infrastructure assembly (instead of System.Web assembly) is now performing request validation in ASP.NET MVC 3. Now you may ask: where Microsoft.Web.Infrastructure assembly is performing some operation on the members of HttpRequest class. There are at least two places where the Microsoft.Web.Infrastructure assembly performing some operation , Microsoft.Web.Infrastructure.DynamicValidationHelper.GranularValidationReflectionUtil.GetInstance method and Microsoft.Web.Infrastructure.DynamicValidationHelper.ValidationUtility.CollectionReplacer.ReplaceCollection method, Here is the implementation of these methods,   private static GranularValidationReflectionUtil GetInstance() { try { if (DynamicValidationShimReflectionUtil.Instance != null) { return null; } GranularValidationReflectionUtil util = new GranularValidationReflectionUtil(); Type containingType = typeof(NameObjectCollectionBase); string fieldName = "_entriesArray"; bool isStatic = false; Type fieldType = typeof(ArrayList); FieldInfo fieldInfo = CommonReflectionUtil.FindField(containingType, fieldName, isStatic, fieldType); util._del_get_NameObjectCollectionBase_entriesArray = MakeFieldGetterFunc<NameObjectCollectionBase, ArrayList>(fieldInfo); util._del_set_NameObjectCollectionBase_entriesArray = MakeFieldSetterFunc<NameObjectCollectionBase, ArrayList>(fieldInfo); Type type6 = typeof(NameObjectCollectionBase); string str2 = "_entriesTable"; bool flag2 = false; Type type7 = typeof(Hashtable); FieldInfo info2 = CommonReflectionUtil.FindField(type6, str2, flag2, type7); util._del_get_NameObjectCollectionBase_entriesTable = MakeFieldGetterFunc<NameObjectCollectionBase, Hashtable>(info2); util._del_set_NameObjectCollectionBase_entriesTable = MakeFieldSetterFunc<NameObjectCollectionBase, Hashtable>(info2); Type targetType = CommonAssemblies.System.GetType("System.Collections.Specialized.NameObjectCollectionBase+NameObjectEntry"); Type type8 = targetType; string str3 = "Key"; bool flag3 = false; Type type9 = typeof(string); FieldInfo info3 = CommonReflectionUtil.FindField(type8, str3, flag3, type9); util._del_get_NameObjectEntry_Key = MakeFieldGetterFunc<string>(targetType, info3); Type type10 = targetType; string str4 = "Value"; bool flag4 = false; Type type11 = typeof(object); FieldInfo info4 = CommonReflectionUtil.FindField(type10, str4, flag4, type11); util._del_get_NameObjectEntry_Value = MakeFieldGetterFunc<object>(targetType, info4); util._del_set_NameObjectEntry_Value = MakeFieldSetterFunc(targetType, info4); Type type12 = typeof(HttpRequest); string methodName = "ValidateString"; bool flag5 = false; Type[] argumentTypes = new Type[] { typeof(string), typeof(string), typeof(RequestValidationSource) }; Type returnType = typeof(void); MethodInfo methodInfo = CommonReflectionUtil.FindMethod(type12, methodName, flag5, argumentTypes, returnType); util._del_validateStringCallback = CommonReflectionUtil.MakeFastCreateDelegate<HttpRequest, ValidateStringCallback>(methodInfo); Type type = CommonAssemblies.SystemWeb.GetType("System.Web.HttpValueCollection"); util._del_HttpValueCollection_ctor = CommonReflectionUtil.MakeFastNewObject<Func<NameValueCollection>>(type); Type type14 = typeof(HttpRequest); string str6 = "_form"; bool flag6 = false; Type type15 = type; FieldInfo info6 = CommonReflectionUtil.FindField(type14, str6, flag6, type15); util._del_get_HttpRequest_form = MakeFieldGetterFunc<HttpRequest, NameValueCollection>(info6); util._del_set_HttpRequest_form = MakeFieldSetterFunc(typeof(HttpRequest), info6); Type type16 = typeof(HttpRequest); string str7 = "_queryString"; bool flag7 = false; Type type17 = type; FieldInfo info7 = CommonReflectionUtil.FindField(type16, str7, flag7, type17); util._del_get_HttpRequest_queryString = MakeFieldGetterFunc<HttpRequest, NameValueCollection>(info7); util._del_set_HttpRequest_queryString = MakeFieldSetterFunc(typeof(HttpRequest), info7); Type type3 = CommonAssemblies.SystemWeb.GetType("System.Web.Util.SimpleBitVector32"); Type type18 = typeof(HttpRequest); string str8 = "_flags"; bool flag8 = false; Type type19 = type3; FieldInfo flagsFieldInfo = CommonReflectionUtil.FindField(type18, str8, flag8, type19); Type type20 = type3; string str9 = "get_Item"; bool flag9 = false; Type[] typeArray4 = new Type[] { typeof(int) }; Type type21 = typeof(bool); MethodInfo itemGetter = CommonReflectionUtil.FindMethod(type20, str9, flag9, typeArray4, type21); Type type22 = type3; string str10 = "set_Item"; bool flag10 = false; Type[] typeArray6 = new Type[] { typeof(int), typeof(bool) }; Type type23 = typeof(void); MethodInfo itemSetter = CommonReflectionUtil.FindMethod(type22, str10, flag10, typeArray6, type23); MakeRequestValidationFlagsAccessors(flagsFieldInfo, itemGetter, itemSetter, out util._del_BitVector32_get_Item, out util._del_BitVector32_set_Item); return util; } catch { return null; } } private static void ReplaceCollection(HttpContext context, FieldAccessor<NameValueCollection> fieldAccessor, Func<NameValueCollection> propertyAccessor, Action<NameValueCollection> storeInUnvalidatedCollection, RequestValidationSource validationSource, ValidationSourceFlag validationSourceFlag) { NameValueCollection originalBackingCollection; ValidateStringCallback validateString; SimpleValidateStringCallback simpleValidateString; Func<NameValueCollection> getActualCollection; Action<NameValueCollection> makeCollectionLazy; HttpRequest request = context.Request; Func<bool> getValidationFlag = delegate { return _reflectionUtil.GetRequestValidationFlag(request, validationSourceFlag); }; Func<bool> func = delegate { return !getValidationFlag(); }; Action<bool> setValidationFlag = delegate (bool value) { _reflectionUtil.SetRequestValidationFlag(request, validationSourceFlag, value); }; if ((fieldAccessor.Value != null) && func()) { storeInUnvalidatedCollection(fieldAccessor.Value); } else { originalBackingCollection = fieldAccessor.Value; validateString = _reflectionUtil.MakeValidateStringCallback(context.Request); simpleValidateString = delegate (string value, string key) { if (((key == null) || !key.StartsWith("__", StringComparison.Ordinal)) && !string.IsNullOrEmpty(value)) { validateString(value, key, validationSource); } }; getActualCollection = delegate { fieldAccessor.Value = originalBackingCollection; bool flag = getValidationFlag(); setValidationFlag(false); NameValueCollection col = propertyAccessor(); setValidationFlag(flag); storeInUnvalidatedCollection(new NameValueCollection(col)); return col; }; makeCollectionLazy = delegate (NameValueCollection col) { simpleValidateString(col[null], null); LazilyValidatingArrayList array = new LazilyValidatingArrayList(_reflectionUtil.GetNameObjectCollectionEntriesArray(col), simpleValidateString); _reflectionUtil.SetNameObjectCollectionEntriesArray(col, array); LazilyValidatingHashtable table = new LazilyValidatingHashtable(_reflectionUtil.GetNameObjectCollectionEntriesTable(col), simpleValidateString); _reflectionUtil.SetNameObjectCollectionEntriesTable(col, table); }; Func<bool> hasValidationFired = func; Action disableValidation = delegate { setValidationFlag(false); }; Func<int> fillInActualFormContents = delegate { NameValueCollection values = getActualCollection(); makeCollectionLazy(values); return values.Count; }; DeferredCountArrayList list = new DeferredCountArrayList(hasValidationFired, disableValidation, fillInActualFormContents); NameValueCollection target = _reflectionUtil.NewHttpValueCollection(); _reflectionUtil.SetNameObjectCollectionEntriesArray(target, list); fieldAccessor.Value = target; } }             Hopefully the above code will help you to understand the internal working of granular request validation. It is also important to note that Microsoft.Web.Infrastructure assembly invokes HttpRequest.ValidateInput method internally. For further understanding please see Microsoft.Web.Infrastructure assembly code. Finally you may ask: at which stage ASP NET MVC 3 will invoke these methods. You will find this answer by looking at the following method source,   Unvalidated extension method for HttpRequest class defined in System.Web.Helpers.Validation class. System.Web.Mvc.MvcHandler.ProcessRequestInit method. System.Web.Mvc.ControllerActionInvoker.ValidateRequest method. System.Web.WebPages.WebPageHttpHandler.ProcessRequestInternal method.       Summary:             ASP.NET helps in preventing XSS attack using a feature called request validation. In this article, I showed you how you can use granular request validation in ASP.NET MVC 3. I explain you the internal working of  granular request validation. Hope you will enjoy this article too.   SyntaxHighlighter.all()

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  • Design by Contract with Microsoft .Net Code Contract

    - by Fredrik N
    I have done some talks on different events and summits about Defensive Programming and Design by Contract, last time was at Cornerstone’s Developer Summit 2010. Next time will be at SweNug (Sweden .Net User Group). I decided to write a blog post about of some stuffs I was talking about. Users are a terrible thing! Protect your self from them ”Human users have a gift for doing the worst possible thing at the worst possible time.” – Michael T. Nygard, Release It! The kind of users Michael T. Nygard are talking about is the users of a system. We also have users that uses our code, the users I’m going to focus on is the users of our code. Me and you and another developers. “Any fool can write code that a computer can understand. Good programmers write code that humans can understand.” – Martin Fowler Good programmers also writes code that humans know how to use, good programmers also make sure software behave in a predictable manner despise inputs or user actions. Design by Contract   Design by Contract (DbC) is a way for us to make a contract between us (the code writer) and the users of our code. It’s about “If you give me this, I promise to give you this”. It’s not about business validations, that is something completely different that should be part of the domain model. DbC is to make sure the users of our code uses it in a correct way, and that we can rely on the contract and write code in a way where we know that the users will follow the contract. It will make it much easier for us to write code with a contract specified. Something like the following code is something we may see often: public void DoSomething(Object value) { value.DoIKnowThatICanDoThis(); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Where “value” can be uses directly or passed to other methods and later be used. What some of us can easily forget here is that the “value” can be “null”. We will probably not passing a null value, but someone else that uses our code maybe will do it. I think most of you (including me) have passed “null” into a method because you don’t know if the argument need to be specified to a valid value etc. I bet most of you also have got the “Null reference exception”. Sometimes this “Null reference exception” can be hard and take time to fix, because we need to search among our code to see where the “null” value was passed in etc. Wouldn’t it be much better if we can as early as possible specify that the value can’t not be null, so the users of our code also know it when the users starts to use our code, and before run time execution of the code? This is where DbC comes into the picture. We can use DbC to specify what we need, and by doing so we can rely on the contract when we write our code. So the code above can actually use the DoIKnowThatICanDoThis() method on the value object without being worried that the “value” can be null. The contract between the users of the code and us writing the code, says that the “value” can’t be null.   Pre- and Postconditions   When working with DbC we are specifying pre- and postconditions.  Precondition is a condition that should be met before a query or command is executed. An example of a precondition is: “The Value argument of the method can’t be null”, and we make sure the “value” isn’t null before the method is called. Postcondition is a condition that should be met when a command or query is completed, a postcondition will make sure the result is correct. An example of a postconditon is “The method will return a list with at least 1 item”. Commands an Quires When using DbC, we need to know what a Command and a Query is, because some principles that can be good to follow are based on commands and queries. A Command is something that will not return anything, like the SQL’s CREATE, UPDATE and DELETE. There are two kinds of Commands when using DbC, the Creation commands (for example a Constructor), and Others. Others can for example be a Command to add a value to a list, remove or update a value etc. //Creation commands public Stack(int size) //Other commands public void Push(object value); public void Remove(); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   A Query, is something that will return something, for example an Attribute, Property or a Function, like the SQL’s SELECT.   There are two kinds of Queries, the Basic Queries  (Quires that aren’t based on another queries), and the Derived Queries, queries that is based on another queries. Here is an example of queries of a Stack: //Basic Queries public int Count; public object this[int index] { get; } //Derived Queries //Is related to Count Query public bool IsEmpty() { return Count == 0; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } To understand about some principles that are good to follow when using DbC, we need to know about the Commands and different Queries. The 6 Principles When working with DbC, it’s advisable to follow some principles to make it easier to define and use contracts. The following DbC principles are: Separate commands and queries. Separate basic queries from derived queries. For each derived query, write a postcondition that specifies what result will be returned, in terms of one or more basic queries. For each command, write a postcondition that specifies the value of every basic query. For every query and command, decide on a suitable precondition. Write invariants to define unchanging properties of objects. Before I will write about each of them I want you to now that I’m going to use .Net 4.0 Code Contract. I will in the rest of the post uses a simple Stack (Yes I know, .Net already have a Stack class) to give you the basic understanding about using DbC. A Stack is a data structure where the first item in, will be the first item out. Here is a basic implementation of a Stack where not contract is specified yet: public class Stack { private object[] _array; //Basic Queries public uint Count; public object this[uint index] { get { return _array[index]; } set { _array[index] = value; } } //Derived Queries //Is related to Count Query public bool IsEmpty() { return Count == 0; } //Is related to Count and this[] Query public object Top() { return this[Count]; } //Creation commands public Stack(uint size) { Count = 0; _array = new object[size]; } //Other commands public void Push(object value) { this[++Count] = value; } public void Remove() { this[Count] = null; Count--; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   Note: The Stack is implemented in a way to demonstrate the use of Code Contract in a simple way, the implementation may not look like how you would implement it, so don’t think this is the perfect Stack implementation, only used for demonstration.   Before I will go deeper into the principles I will simply mention how we can use the .Net Code Contract. I mention before about pre- and postcondition, is about “Require” something and to “Ensure” something. When using Code Contract, we will use a static class called “Contract” and is located in he “System.Diagnostics.Contracts” namespace. The contract must be specified at the top or our member statement block. To specify a precondition with Code Contract we uses the Contract.Requires method, and to specify a postcondition, we uses the Contract.Ensure method. Here is an example where both a pre- and postcondition are used: public object Top() { Contract.Requires(Count > 0, "Stack is empty"); Contract.Ensures(Contract.Result<object>() == this[Count]); return this[Count]; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   The contract above requires that the Count is greater than 0, if not we can’t get the item at the Top of a Stack. We also Ensures that the results (By using the Contract.Result method, we can specify a postcondition that will check if the value returned from a method is correct) of the Top query is equal to this[Count].   1. Separate Commands and Queries   When working with DbC, it’s important to separate Command and Quires. A method should either be a command that performs an Action, or returning information to the caller, not both. By asking a question the answer shouldn’t be changed. The following is an example of a Command and a Query of a Stack: public void Push(object value) public object Top() .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   The Push is a command and will not return anything, just add a value to the Stack, the Top is a query to get the item at the top of the stack.   2. Separate basic queries from derived queries There are two different kinds of queries,  the basic queries that doesn’t rely on another queries, and derived queries that uses a basic query. The “Separate basic queries from derived queries” principle is about about that derived queries can be specified in terms of basic queries. So this principles is more about recognizing that a query is a derived query or a basic query. It will then make is much easier to follow the other principles. The following code shows a basic query and a derived query: //Basic Queries public uint Count; //Derived Queries //Is related to Count Query public bool IsEmpty() { return Count == 0; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   We can see that IsEmpty will use the Count query, and that makes the IsEmpty a Derived query.   3. For each derived query, write a postcondition that specifies what result will be returned, in terms of one or more basic queries.   When the derived query is recognize we can follow the 3ed principle. For each derived query, we can create a postcondition that specifies what result our derived query will return in terms of one or more basic queries. Remember that DbC is about contracts between the users of the code and us writing the code. So we can’t use demand that the users will pass in a valid value, we must also ensure that we will give the users what the users wants, when the user is following our contract. The IsEmpty query of the Stack will use a Count query and that will make the IsEmpty a Derived query, so we should now write a postcondition that specified what results will be returned, in terms of using a basic query and in this case the Count query, //Basic Queries public uint Count; //Derived Queries public bool IsEmpty() { Contract.Ensures(Contract.Result<bool>() == (Count == 0)); return Count == 0; } The Contract.Ensures is used to create a postcondition. The above code will make sure that the results of the IsEmpty (by using the Contract.Result to get the result of the IsEmpty method) is correct, that will say that the IsEmpty will be either true or false based on Count is equal to 0 or not. The postcondition are using a basic query, so the IsEmpty is now following the 3ed principle. We also have another Derived Query, the Top query, it will also need a postcondition and it uses all basic queries. The Result of the Top method must be the same value as the this[] query returns. //Basic Queries public uint Count; public object this[uint index] { get { return _array[index]; } set { _array[index] = value; } } //Derived Queries //Is related to Count and this[] Query public object Top() { Contract.Ensures(Contract.Result<object>() == this[Count]); return this[Count]; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   4. For each command, write a postcondition that specifies the value of every basic query.   For each command we will create a postconditon that specifies the value of basic queries. If we look at the Stack implementation we will have three Commands, one Creation command, the Constructor, and two others commands, Push and Remove. Those commands need a postcondition and they should include basic query to follow the 4th principle. //Creation commands public Stack(uint size) { Contract.Ensures(Count == 0); Count = 0; _array = new object[size]; } //Other commands public void Push(object value) { Contract.Ensures(Count == Contract.OldValue<uint>(Count) + 1); Contract.Ensures(this[Count] == value); this[++Count] = value; } public void Remove() { Contract.Ensures(Count == Contract.OldValue<uint>(Count) - 1); this[Count] = null; Count--; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   As you can see the Create command will Ensures that Count will be 0 when the Stack is created, when a Stack is created there shouldn’t be any items in the stack. The Push command will take a value and put it into the Stack, when an item is pushed into the Stack, the Count need to be increased to know the number of items added to the Stack, and we must also make sure the item is really added to the Stack. The postconditon of the Push method will make sure the that old value of the Count (by using the Contract.OldValue we can get the value a Query has before the method is called)  plus 1 will be equal to the Count query, this is the way we can ensure that the Push will increase the Count with one. We also make sure the this[] query will now contain the item we pushed into the Stack. The Remove method must make sure the Count is decreased by one when the top item is removed from the Stack. The Commands is now following the 4th principle, where each command now have a postcondition that used the value of basic queries. Note: The principle says every basic Query, the Remove only used one Query the Count, it’s because this command can’t use the this[] query because an item is removed, so the only way to make sure an item is removed is to just use the Count query, so the Remove will still follow the principle.   5. For every query and command, decide on a suitable precondition.   We have now focused only on postcondition, now time for some preconditons. The 5th principle is about deciding a suitable preconditon for every query and command. If we starts to look at one of our basic queries (will not go through all Queries and commands here, just some of them) the this[] query, we can’t pass an index that is lower then 1 (.Net arrays and list are zero based, but not the stack in this blog post ;)) and the index can’t be lesser than the number of items in the stack. So here we will need a preconditon. public object this[uint index] { get { Contract.Requires(index >= 1); Contract.Requires(index <= Count); return _array[index]; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Think about the Contract as an documentation about how to use the code in a correct way, so if the contract could be specified elsewhere (not part of the method body), we could simply write “return _array[index]” and there is no need to check if index is greater or lesser than Count, because that is specified in a “contract”. The implementation of Code Contract, requires that the contract is specified in the code. As a developer I would rather have this contract elsewhere (Like Spec#) or implemented in a way Eiffel uses it as part of the language. Now when we have looked at one Query, we can also look at one command, the Remove command (You can see the whole implementation of the Stack at the end of this blog post, where precondition is added to more queries and commands then what I’m going to show in this section). We can only Remove an item if the Count is greater than 0. So we can write a precondition that will require that Count must be greater than 0. public void Remove() { Contract.Requires(Count > 0); Contract.Ensures(Count == Contract.OldValue<uint>(Count) - 1); this[Count] = null; Count--; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   6. Write invariants to define unchanging properties of objects.   The last principle is about making sure the object are feeling great! This is done by using invariants. When using Code Contract we can specify invariants by adding a method with the attribute ContractInvariantMethod, the method must be private or public and can only contains calls to Contract.Invariant. To make sure the Stack feels great, the Stack must have 0 or more items, the Count can’t never be a negative value to make sure each command and queries can be used of the Stack. Here is our invariant for the Stack object: [ContractInvariantMethod] private void ObjectInvariant() { Contract.Invariant(Count >= 0); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   Note: The ObjectInvariant method will be called every time after a Query or Commands is called. Here is the full example using Code Contract:   public class Stack { private object[] _array; //Basic Queries public uint Count; public object this[uint index] { get { Contract.Requires(index >= 1); Contract.Requires(index <= Count); return _array[index]; } set { Contract.Requires(index >= 1); Contract.Requires(index <= Count); _array[index] = value; } } //Derived Queries //Is related to Count Query public bool IsEmpty() { Contract.Ensures(Contract.Result<bool>() == (Count == 0)); return Count == 0; } //Is related to Count and this[] Query public object Top() { Contract.Requires(Count > 0, "Stack is empty"); Contract.Ensures(Contract.Result<object>() == this[Count]); return this[Count]; } //Creation commands public Stack(uint size) { Contract.Requires(size > 0); Contract.Ensures(Count == 0); Count = 0; _array = new object[size]; } //Other commands public void Push(object value) { Contract.Requires(value != null); Contract.Ensures(Count == Contract.OldValue<uint>(Count) + 1); Contract.Ensures(this[Count] == value); this[++Count] = value; } public void Remove() { Contract.Requires(Count > 0); Contract.Ensures(Count == Contract.OldValue<uint>(Count) - 1); this[Count] = null; Count--; } [ContractInvariantMethod] private void ObjectInvariant() { Contract.Invariant(Count >= 0); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Summary By using Design By Contract we can make sure the users are using our code in a correct way, and we must also make sure the users will get the expected results when they uses our code. This can be done by specifying contracts. To make it easy to use Design By Contract, some principles may be good to follow like the separation of commands an queries. With .Net 4.0 we can use the Code Contract feature to specify contracts.

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  • Know more about Cache Buffer Handle

    - by Liu Maclean(???)
    ??????«latch free:cache buffer handles???SQL????»?????cache buffer handle latch?????,?????????: “?????pin?buffer header???????buffer handle,??buffer handle?????????cache buffer handles?,??????cache buffer handles??????,???????cache???buffer handles,?????(reserved set)?????????????_db_handles_cached(???5)???,?????????????????SQL??????????????????????,????pin??????,????????handle,?????????5?cached buffer handles???handle????????????????,Oracle?????????????????pin?”????“?buffer,????????????????handle???db_block_buffers/processes,????_cursor_db_buffers_pinned???????cache buffer handles?????,??????,????????????SQL,????cache?buffer handles?????????,??????????????,???????????/?????” ????T.ASKMACLEAN.COM????,??????cache Buffer handle?????: cache buffer handle ??: ------------------------------ | Buffer state object | ------------------------------ | Place to hang the buffer | ------------------------------ | Consistent Get? | ------------------------------ | Proc Owning SO | ------------------------------ | Flags(RIR) | ------------------------------ ???? cache buffer handle SO: 70000046fdfe530, type: 24, owner: 70000041b018630, flag: INIT/-/-/0×00(buffer) (CR) PR: 70000048e92d148 FLG: 0×500000lock rls: 0, class bit: 0kcbbfbp: [BH: 7000001c7f069b0, LINK: 70000046fdfe570]where: kdswh02: kdsgrp, why: 0BH (7000001c7f069b0) file#: 12 rdba: 0×03061612 (12/398866) class: 1 ba: 7000001c70ee000set: 75 blksize: 8192 bsi: 0 set-flg: 0 pwbcnt: 0dbwrid: 2 obj: 66209 objn: 48710 tsn: 6 afn: 12hash: [700000485f12138,700000485f12138] lru: [70000025af67790,700000132f69ee0]lru-flags: hot_bufferckptq: [NULL] fileq: [NULL] objq: [700000114f5dd10,70000028bf5d620]use: [70000046fdfe570,70000046fdfe570] wait: [NULL]st: SCURRENT md: SHR tch: 0flags: affinity_lockLRBA: [0x0.0.0] HSCN: [0xffff.ffffffff] HSUB: [65535]where: kdswh02: kdsgrp, why: 0 # Example:#   (buffer) (CR) PR: 37290 FLG:    0#   kcbbfbp    : [BH: befd8, LINK: 7836c] (WAITING) Buffer handle (X$KCBBF) kernel cache, buffer buffer_handles Query x$kcbbf  – lists all the buffer handles ???? _db_handles             System-wide simultaneous buffer operations ,no of buffer handles_db_handles_cached      Buffer handles cached each process , no of processes  default 5_cursor_db_buffers_pinned  additional number of buffers a cursor can pin at once_session_kept_cursor_pins       Number of cursors pins to keep in a session When a buffer is pinned it is attached to buffer state object. ??? ???????? cache buffer handles latch ? buffer pin???: SESSION A : SQL> select * from v$version; BANNER ---------------------------------------------------------------- Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bi PL/SQL Release 10.2.0.5.0 - Production CORE    10.2.0.5.0      Production TNS for Linux: Version 10.2.0.5.0 - Production NLSRTL Version 10.2.0.5.0 - Production SQL> create table test_cbc_handle(t1 int); Table created. SQL> insert into test_cbc_handle values(1); 1 row created. SQL> commit; Commit complete. SQL> select rowid from test_cbc_handle; ROWID ------------------ AAANO6AABAAAQZSAAA SQL> select * from test_cbc_handle where rowid='AAANO6AABAAAQZSAAA';         T1 ----------          1 SQL> select addr,name from v$latch_parent where name='cache buffer handles'; ADDR             NAME ---------------- -------------------------------------------------- 00000000600140A8 cache buffer handles SQL> select to_number('00000000600140A8','xxxxxxxxxxxxxxxxxxxx') from dual; TO_NUMBER('00000000600140A8','XXXXXXXXXXXXXXXXXXXX') ----------------------------------------------------                                           1610694824 ??cache buffer handles????parent latch ??? child latch ???SESSION A hold ??????cache buffer handles parent latch ???? oradebug call kslgetl ??, kslgetl?oracle??get latch??? SQL> oradebug setmypid; Statement processed. SQL> oradebug call kslgetl 1610694824 1; Function returned 1 ?????SESSION B ???: SQL> select * from v$latchholder;        PID        SID LADDR            NAME                                                                   GETS ---------- ---------- ---------------- ---------------------------------------------------------------- ----------         15        141 00000000600140A8 cache buffer handles                                                    119 cache buffer handles latch ???session A hold??,????????acquire cache buffer handle latch SQL> select * from test_cbc_handle where rowid='AAANO6AABAAAQZSAAA';         T1 ----------          1 ?????Server Process?????? read buffer, ????????"_db_handles_cached", ??process?cache 5? cache buffer handle ??"_db_handles_cached"=0,?process????5????cache buffer handle , ???? process ???pin buffer,???hold cache buffer handle latch??????cache buffer handle SQL> alter system set "_db_handles_cached"=0 scope=spfile; System altered. ????? shutdown immediate; startup; session A: SQL> oradebug setmypid; Statement processed. SQL> oradebug call kslgetl 1610694824 1; Function returned 1 session B: select * from test_cbc_handle where rowid='AAANO6AABAAAQZSAAA'; session B hang!! WHY? SQL> oradebug setmypid; Statement processed. SQL> oradebug dump systemstate 266; Statement processed.   SO: 0x11b30b7b0, type: 2, owner: (nil), flag: INIT/-/-/0x00   (process) Oracle pid=22, calls cur/top: (nil)/0x11b453c38, flag: (0) -             int error: 0, call error: 0, sess error: 0, txn error 0   (post info) last post received: 0 0 0               last post received-location: No post               last process to post me: none               last post sent: 0 0 0               last post sent-location: No post               last process posted by me: none     (latch info) wait_event=0 bits=8       holding    (efd=4) 600140a8 cache buffer handles level=3   SO: 0x11b305810, type: 2, owner: (nil), flag: INIT/-/-/0x00   (process) Oracle pid=10, calls cur/top: 0x11b455ac0/0x11b450a58, flag: (0) -             int error: 0, call error: 0, sess error: 0, txn error 0   (post info) last post received: 0 0 0               last post received-location: No post               last process to post me: none               last post sent: 0 0 0               last post sent-location: No post               last process posted by me: none     (latch info) wait_event=0 bits=2         Location from where call was made: kcbzgs:       waiting for 600140a8 cache buffer handles level=3 FBD93353:000019F0    10   162 10005   1 KSL WAIT BEG [latch: cache buffer handles] 1610694824/0x600140a8 125/0x7d 0/0x0 FF936584:00002761    10   144 10005   1 KSL WAIT BEG [latch: cache buffer handles] 1610694824/0x600140a8 125/0x7d 0/0x0 PID=22 holding ??cache buffer handles latch PID=10 ?? cache buffer handles latch, ????"_db_handles_cached"=0 ?? process??????cache buffer handles ??systemstate???? kcbbfbp cache buffer handle??, ?? "_db_handles_cached"=0 ? cache buffer handles latch?hold ?? ????cache buffer handles latch , ??? buffer?pin?????????? session A exit session B: SQL> select * from v$latchholder; no rows selected SQL> insert into test_cbc_handle values(2); 1 row created. SQL> commit; Commit complete. SQL> SQL> select t1,rowid from test_cbc_handle;         T1 ROWID ---------- ------------------          1 AAANPAAABAAAQZSAAA          2 AAANPAAABAAAQZSAAB SQL> select spid,pid from v$process where addr = ( select paddr from v$session where sid=(select distinct sid from v$mystat)); SPID                PID ------------ ---------- 19251                10 ? GDB ? SPID=19215 ?debug , ?? kcbrls ????breakpoint ??? ????release buffer [oracle@vrh8 ~]$ gdb $ORACLE_HOME/bin/oracle 19251 GNU gdb (GDB) Red Hat Enterprise Linux (7.0.1-37.el5) Copyright (C) 2009 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.  Type "show copying" and "show warranty" for details. This GDB was configured as "x86_64-redhat-linux-gnu". For bug reporting instructions, please see: <http://www.gnu.org/software/gdb/bugs/>... Reading symbols from /s01/oracle/product/10.2.0.5/db_1/bin/oracle...(no debugging symbols found)...done. Attaching to program: /s01/oracle/product/10.2.0.5/db_1/bin/oracle, process 19251 Reading symbols from /s01/oracle/product/10.2.0.5/db_1/lib/libskgxp10.so...(no debugging symbols found)...done. Loaded symbols for /s01/oracle/product/10.2.0.5/db_1/lib/libskgxp10.so Reading symbols from /s01/oracle/product/10.2.0.5/db_1/lib/libhasgen10.so...(no debugging symbols found)...done. Loaded symbols for /s01/oracle/product/10.2.0.5/db_1/lib/libhasgen10.so Reading symbols from /s01/oracle/product/10.2.0.5/db_1/lib/libskgxn2.so...(no debugging symbols found)...done. Loaded symbols for /s01/oracle/product/10.2.0.5/db_1/lib/libskgxn2.so Reading symbols from /s01/oracle/product/10.2.0.5/db_1/lib/libocr10.so...(no debugging symbols found)...done. Loaded symbols for /s01/oracle/product/10.2.0.5/db_1/lib/libocr10.so Reading symbols from /s01/oracle/product/10.2.0.5/db_1/lib/libocrb10.so...(no debugging symbols found)...done. Loaded symbols for /s01/oracle/product/10.2.0.5/db_1/lib/libocrb10.so Reading symbols from /s01/oracle/product/10.2.0.5/db_1/lib/libocrutl10.so...(no debugging symbols found)...done. Loaded symbols for /s01/oracle/product/10.2.0.5/db_1/lib/libocrutl10.so Reading symbols from /s01/oracle/product/10.2.0.5/db_1/lib/libjox10.so...(no debugging symbols found)...done. Loaded symbols for /s01/oracle/product/10.2.0.5/db_1/lib/libjox10.so Reading symbols from /s01/oracle/product/10.2.0.5/db_1/lib/libclsra10.so...(no debugging symbols found)...done. Loaded symbols for /s01/oracle/product/10.2.0.5/db_1/lib/libclsra10.so Reading symbols from /s01/oracle/product/10.2.0.5/db_1/lib/libdbcfg10.so...(no debugging symbols found)...done. Loaded symbols for /s01/oracle/product/10.2.0.5/db_1/lib/libdbcfg10.so Reading symbols from /s01/oracle/product/10.2.0.5/db_1/lib/libnnz10.so...(no debugging symbols found)...done. Loaded symbols for /s01/oracle/product/10.2.0.5/db_1/lib/libnnz10.so Reading symbols from /usr/lib64/libaio.so.1...(no debugging symbols found)...done. Loaded symbols for /usr/lib64/libaio.so.1 Reading symbols from /lib64/libdl.so.2...(no debugging symbols found)...done. Loaded symbols for /lib64/libdl.so.2 Reading symbols from /lib64/libm.so.6...(no debugging symbols found)...done. Loaded symbols for /lib64/libm.so.6 Reading symbols from /lib64/libpthread.so.0...(no debugging symbols found)...done. [Thread debugging using libthread_db enabled] Loaded symbols for /lib64/libpthread.so.0 Reading symbols from /lib64/libnsl.so.1...(no debugging symbols found)...done. Loaded symbols for /lib64/libnsl.so.1 Reading symbols from /lib64/libc.so.6...(no debugging symbols found)...done. Loaded symbols for /lib64/libc.so.6 Reading symbols from /lib64/ld-linux-x86-64.so.2...(no debugging symbols found)...done. Loaded symbols for /lib64/ld-linux-x86-64.so.2 Reading symbols from /lib64/libnss_files.so.2...(no debugging symbols found)...done. Loaded symbols for /lib64/libnss_files.so.2 0x00000035c000d940 in __read_nocancel () from /lib64/libpthread.so.0 (gdb) break kcbrls Breakpoint 1 at 0x10e5d24 session B: select * from test_cbc_handle where rowid='AAANPAAABAAAQZSAAA'; select hang !! GDB (gdb) c Continuing. Breakpoint 1, 0x00000000010e5d24 in kcbrls () (gdb) bt #0  0x00000000010e5d24 in kcbrls () #1  0x0000000002e87d25 in qertbFetchByUserRowID () #2  0x00000000030c62b8 in opifch2 () #3  0x00000000032327f0 in kpoal8 () #4  0x00000000013b7c10 in opiodr () #5  0x0000000003c3c9da in ttcpip () #6  0x00000000013b3144 in opitsk () #7  0x00000000013b60ec in opiino () #8  0x00000000013b7c10 in opiodr () #9  0x00000000013a92f8 in opidrv () #10 0x0000000001fa3936 in sou2o () #11 0x000000000072d40b in opimai_real () #12 0x000000000072d35c in main () SQL> oradebug setmypid; Statement processed. SQL> oradebug dump systemstate 266; Statement processed. ?????? kcbbfbp buffer cache handle ?  SO state object ? BH BUFFER HEADER  link???     ----------------------------------------     SO: 0x11b452348, type: 3, owner: 0x11b305810, flag: INIT/-/-/0x00     (call) sess: cur 11b41bd18, rec 0, usr 11b41bd18; depth: 0       ----------------------------------------       SO: 0x1182dc750, type: 24, owner: 0x11b452348, flag: INIT/-/-/0x00       (buffer) (CR) PR: 0x11b305810 FLG: 0x108000       class bit: (nil)       kcbbfbp: [BH: 0xf2fc69f8, LINK: 0x1182dc790]       where: kdswh05: kdsgrp, why: 0       BH (0xf2fc69f8) file#: 1 rdba: 0x00410652 (1/67154) class: 1 ba: 0xf297c000         set: 3 blksize: 8192 bsi: 0 set-flg: 2 pwbcnt: 272         dbwrid: 0 obj: 54208 objn: 54202 tsn: 0 afn: 1         hash: [f2fc47f8,1181f3038] lru: [f2fc6b88,f2fc6968]         obj-flags: object_ckpt_list         ckptq: [1182ecf38,1182ecf38] fileq: [1182ecf58,1182ecf58] objq: [108712a28,108712a28]         use: [1182dc790,1182dc790] wait: [NULL]         st: XCURRENT md: SHR tch: 12         flags: buffer_dirty gotten_in_current_mode block_written_once                 redo_since_read         LRBA: [0xc7.73b.0] HSCN: [0x0.1cbe52] HSUB: [1]         Using State Objects           ----------------------------------------           SO: 0x1182dc750, type: 24, owner: 0x11b452348, flag: INIT/-/-/0x00           (buffer) (CR) PR: 0x11b305810 FLG: 0x108000           class bit: (nil)           kcbbfbp: [BH: 0xf2fc69f8, LINK: 0x1182dc790]           where: kdswh05: kdsgrp, why: 0         buffer tsn: 0 rdba: 0x00410652 (1/67154)         scn: 0x0000.001cbe52 seq: 0x01 flg: 0x02 tail: 0xbe520601         frmt: 0x02 chkval: 0x0000 type: 0x06=trans data tab 0, row 0, @0x1f9a tl: 6 fb: --H-FL-- lb: 0x0  cc: 1 col  0: [ 2]  c1 02 tab 0, row 1, @0x1f94 tl: 6 fb: --H-FL-- lb: 0x2  cc: 1 col  0: [ 2]  c1 15 end_of_block_dump         (buffer) (CR) PR: 0x11b305810 FLG: 0x108000 st: XCURRENT md: SHR tch: 12 ? buffer header?status= XCURRENT mode=KCBMSHARE KCBMSHR     current share ?????  x$kcbbf ????? cache buffer handle SQL> select distinct KCBBPBH from  x$kcbbf ; KCBBPBH ---------------- 00 00000000F2FC69F8            ==>0xf2fc69f8 SQL> select * from x$kcbbf where kcbbpbh='00000000F2FC69F8'; ADDR                   INDX    INST_ID KCBBFSO_TYP KCBBFSO_FLG KCBBFSO_OWN ---------------- ---------- ---------- ----------- ----------- ----------------   KCBBFFLG    KCBBFCR    KCBBFCM KCBBFMBR         KCBBPBH ---------- ---------- ---------- ---------------- ---------------- KCBBPBF          X0KCBBPBH        X0KCBBPBF        X1KCBBPBH ---------------- ---------------- ---------------- ---------------- X1KCBBPBF        KCBBFBH            KCBBFWHR   KCBBFWHY ---------------- ---------------- ---------- ---------- 00000001182DC750        748          1          24           1 000000011B452348    1081344          1          0 00               00000000F2FC69F8 00000001182DC750 00               00000001182DC750 00 00000001182DC7F8 00                      583          0 SQL> desc x$kcbbf;  Name                                      Null?    Type  ----------------------------------------- -------- ----------------------------  ADDR                                               RAW(8)  INDX                                               NUMBER  INST_ID                                            NUMBER  KCBBFSO_TYP                                        NUMBER  KCBBFSO_FLG                                        NUMBER  KCBBFSO_OWN                                        RAW(8)  KCBBFFLG                                           NUMBER  KCBBFCR                                            NUMBER  KCBBFCM                                            NUMBER  KCBBFMBR                                           RAW(8)  KCBBPBH                                            RAW(8)  KCBBPBF                                            RAW(8)  X0KCBBPBH                                          RAW(8)  X0KCBBPBF                                          RAW(8)  X1KCBBPBH                                          RAW(8)  X1KCBBPBF                                          RAW(8)  KCBBFBH                                            RAW(8)  KCBBFWHR                                           NUMBER  KCBBFWHY                                           NUMBER gdb ?? ?process??????kcbrls release buffer? ???cache buffer handle??? SQL> select distinct KCBBPBH from  x$kcbbf ; KCBBPBH ---------------- 00

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