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• Proftpd: How to set default root to a users home directory without jailing the user?

  - by sacamano

  Hi there. I've installed proftpd on my debian box but I'm having having some trouble with the configuration. In my proftpd.conf I've added; DefaultRoot ~ !ftp_special This works fine in that all users except members of ftp-special are unable to navigate outside of their home folder. However, I want users that are members of ftp-special to enter a special home folder when logging on to the ftp server but at the same time I want them to be able to navigate the entire server. Right now, if a user that is a member of ftp-special logs on his entry-point is the root ( / ). Thanks in advance.

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• What does an object look like in memory?

  - by NeilMonday

  This is probably a really dumb question, but I will ask anyway. I am curious what an object looks like in memory. Obviously it would have to have all of its member data in it. I assume that functions for an object would not be duplicated in memory (or maybe I am wrong?). It would seem wasteful to have 999 objects in memory all with the same function defined over and over. If there is only 1 function in memory for all 999 objects, then how does each function know who's member data to modify (I specifically want to know at the low level). Is there an object pointer that gets sent to the function behind the scenes? Perhaps it is different for every compiler? Also, how does the static keyword affect this? With static member data, I would think that all 999 objects would use the exact same memory location for their static member data. Where does this get stored? Static functions I guess would also just be one place in memory, and would not have to interact with instantiated objects, which I think I understand.

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• Grails - Where to store properties related to domains

  - by GalmWing

  This is something I have been struggling about for some time now. The thing is: I have many (20 or so) static arrays of values. I say static because that is how I'm actually storing them, as static arrays inside some domains. For example, if I have a list of known websites, I do: class Website { ... static websites = ["web1", "web2" ...] } But I do this just while developing, because I can easily change the arrays if needed, but what I'm going to do when the application is ready for deployment? In my project it is very probable that, at some point, these arrays of values change. I've been researching on that matter, one can store application properties inside an external .properties file, but it will be impossible to store an array, even futile, because if some array gets an additional value, the application can't recognize it until the name of the new property is added where needed. Another approach is to store this information in the database, but for some reason it seems like a waste to add 20 or more tables that will have just two rows, an id and a name. And the last option, as far as I know, would be an XML, but I'm not very experienced with those. It seems groovy has a way of creating and reading XML files relatively easy, but I don't know how difficult would be to modify an XML whose layout is predefined in the application. Needless to say that storing them in the config.groovy is not an option since any change will require to recompile. I haven't come across some "standard" (maybe a best practice?) way of dealing with these. So the questions is: Where to store these arrays?

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• New user register, script auto create problems!

  - by SKY

  Hi, im currently trying to create a php script that when a new user register, a script (eg:wordpress,blog etc..) will install for them. I'm currently got the code below for just single setup, but how can i setup a form for multi user? which only allowing them to input the username (subdomain) and password. <?php class scriptname_Config { public static $title = 'new_script_title'; // Domain name and path where new script will installed in public static $domain = 'username.domain.com'; public static $absolutePath = '/new_register_username/'; // Settings for general mysql database public static $db = array( 'host' => 'localhost', 'database' => 'scriptname', 'user' => 'root', 'password' => '', 'prefix' => 'scriptname_' ); } define( 'scriptname_BASE_URL', 'http://'.scriptname_Config::$domain.scriptname_Config::$absolutePath ); ?> Or any tutorial that will help is appreciate! Thanks!

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• C# specifying generic delegate type param at runtime

  - by smerlin

  following setup, i have several generic functions, and i need to choose the type and the function identified by two strings at runtime. my first try looked like this: public static class FOOBAR { public delegate void MyDelegateType(int param); public static void foo<T>(int param){...} public static void bar<T>(int param){...} public static void someMethod(string methodstr, string typestr) { MyDelegateType mydel; Type mytype; switch(typestr) { case "int": mytype = typeof(int); break; case "double": mytype = typeof(double); break; default: throw new InvalidTypeException(typestr); } switch(methodstr) { case "foo": mydel = foo<mytype>; //error break; case "bar": mydel = bar<mytype>; //error break; default: throw new InvalidTypeException(methodstr); } for(int i=0; i<1000; ++i) mydel(i); } } since this didnt work, i nested those switchs (a methodstr switch inside the typestr switch or viceversa), but that solution is really ugly and unmaintainable. The number of types is pretty much fixed, but the number of functions like foo or bar will increase by high numbers, so i dont want nested switchs. So how can i make this working without using nested switchs ?

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• Interview question : What is the fastest way to generate prime number recursively ?

  - by hilal

  Generation of prime number is simple but what is the fastest way to find it and generate( prime numbers) it recursively ? Here is my solution. However, it is not the best way. I think it is O(N*sqrt(N)). Please correct me, if I am wrong. public static boolean isPrime(int n) { if (n < 2) { return false; } else if (n % 2 == 0 & n != 2) { return false; } else { return isPrime(n, (int) Math.sqrt(n)); } } private static boolean isPrime(int n, int i) { if (i < 2) { return true; } else if (n % i == 0) { return false; } else { return isPrime(n, --i); } } public static void generatePrimes(int n){ if(n < 2) { return ; } else if(isPrime(n)) { System.out.println(n); } generatePrimes(--n); } public static void main(String[] args) { generatePrimes(200); }

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• Threads syncronization with ThreadPoolExecutor

  - by justme1

  I'm trying to implement some logic when I create main(father) thread witch executes several other threads. Then it waits for some condition which child threads creates. After condition is meet the father executes some more child threads. The problem that when I use wait/notify I have java.lang.IllegalMonitorStateException exception. Here is the code: public class MyExecutor { final static ArrayBlockingQueue<Runnable> queue = new ArrayBlockingQueue<Runnable>(10); final static ExecutorService svc = Executors.newFixedThreadPool(1); static final ThreadPoolExecutor threadPool = new ThreadPoolExecutor(5, 8, 10, TimeUnit.SECONDS, queue); public static void main(String[] args) throws InterruptedException { final MyExecutor me = new MyExecutor(); svc.execute(new Runnable() { public void run() { try { System.out.println("Main Thread"); me.execute(threadPool, 1); System.out.println("Main Thread waiting"); wait(); System.out.println("Main Thread notified"); me.execute(threadPool, 2); Thread.sleep(100); threadPool.shutdown(); threadPool.awaitTermination(20000, TimeUnit.SECONDS); } catch (InterruptedException e) { e.printStackTrace(); } } }); svc.shutdown(); svc.awaitTermination(10000, TimeUnit.SECONDS); System.out.println("Main Thread finished"); } public void execute(ThreadPoolExecutor tpe, final int id) { tpe.execute(new Runnable() { public void run() { try { System.out.println("Child Thread " + id); Thread.sleep(2000); System.out.println("Child Thread " + id + " finished"); notify(); } catch (InterruptedException e) { e.printStackTrace(); } } }); } } When I comment wait and notify line I have the following output: Main Thread Main Thread waiting Main Thread notified Child Thread 1 Child Thread 2 Child Thread 1 finished Child Thread 2 finished Main Thread finished

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• Input In Java- How does it work?

  - by Nir Avnon

  Hey guys, with a lot of help from you i was managed to write this nice code (I'm new in it, so kind of exciting.. :) ) And still I have not understand how can I input this code. first of all, I get an this error in the console line (I'm using Eclipse): Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0 at NumberConverter.main(NumberConverter.java:5). What does that mean? I just want to chack whether it works, and I can't call the function/program any how. I used to call in an "old fashion way", like in scheme, to the function that I wrote and see if something happens. How does it work in java? Do we call the program itself? function? what and where do we write? -I want to chack if it works, doesn't matter how, and I'll be glad to know how can I plugin input. Thank you so much! public class NumberConverter{ public static void main(String[] args) { int i = Integer.parseInt(args[0]); toBinary(i); toOctal(i); toHex(i); } public static void toBinary(int int1){ System.out.println(int1 + " in binary is"); System.out.println(Integer.toBinaryString(int1)); } public static void toOctal(int int1){ System.out.println(int1 + " in octal is"); System.out.println(Integer.toOctalString(int1)); } public static void toHex(int int1){ System.out.println(int1 + " in hex is"); System.out.println(Integer.toHexString(int1)); } }

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• Resource allocation and automatic deallocation

  - by nabulke

  In my application I got many instances of class CDbaOciNotifier. They all share a pointer to only one instance of class OCIEnv. What I like to achieve is that allocation and deallocation of the resource class OCIEnv will be handled automatically inside class CDbaOciNotifier. The desired behaviour is, with the first instance of class CDbaOciNotifier the environment will be created, after that all following notifiers use that same environment. With the destruction of the last notifier, the environment will be destroyed too (call to custom deleter). What I've got so far (using a static factory method to create notifiers): #pragma once #include <string> #include <memory> #include "boost\noncopyable.hpp" class CDbaOciNotifier : private boost::noncopyable { public: virtual ~CDbaOciNotifier(void); static std::auto_ptr<CDbaOciNotifier> createNotifier(const std::string &tnsName, const std::string &user, const std::string &password); private: CDbaOciNotifier(OCIEnv* envhp); // All notifiers share one environment static OCIEnv* m_ENVHP; // Custom deleter static void freeEnvironment(OCIEnv *env); OCIEnv* m_envhp; }; CPP: #include "DbaOciNotifier.h" using namespace std; OCIEnv* CDbaOciNotifier::m_ENVHP = 0; CDbaOciNotifier::~CDbaOciNotifier(void) { } CDbaOciNotifier::CDbaOciNotifier(OCIEnv* envhp) :m_envhp(envhp) { } void CDbaOciNotifier::freeEnvironment(OCIEnv *env) { OCIHandleFree((dvoid *) env, (ub4) OCI_HTYPE_ENV); *env = null; } auto_ptr<CDbaOciNotifier> CDbaOciNotifier::createNotifier(const string &tnsName, const string &user, const string &password) { if(!m_ENVHP) { OCIEnvCreate( (OCIEnv **) &m_ENVHP, OCI_EVENTS|OCI_OBJECT, (dvoid *)0, (dvoid * (*)(dvoid *, size_t)) 0, (dvoid * (*)(dvoid *, dvoid *, size_t))0, (void (*)(dvoid *, dvoid *)) 0, (size_t) 0, (dvoid **) 0 ); } //shared_ptr<OCIEnv> spEnvhp(m_ENVHP, freeEnvironment); ...got so far... return auto_ptr<CDbaOciNotifier>(new CDbaOciNotifier(m_ENVHP)); } I'd like to avoid counting references (notifiers) myself, and use something like shared_ptr. Do you see an easy solution to my problem?

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• binary quicksort

  - by davit-datuashvili

  hi i want implement Binary quicksort algorithm from robert sedgewick book it looks like this public class quickb{ public static final int bitsword=32; public static void quicksortB(int a[],int l,int r,int d){ int i=l; int j=r-1; if (r<=l || d>bitsword) return ; while (j!=i) { while (digit(a[i],d)==0 && (i<j)) i++; while (digit(a[j],d)==1 && (j>i)) j++; int t=a[i]; a[i]=a[j]; a[j]=t; } if (digit(a[r-1],d)== 0) j++; quicksortB(a,l,j-1,d+1); quicksortB(a,j,r,d+1); } public static void main(String[]args){ int a[]=new int[]{4,7,3,9,8,2}; quicksortB(a,0,a.length-1,0); for (int i=0;i<a.length;i++){ System.out.println(a[i]); } } public static int digit(int m,int d){ return (m>>d)&1; } } but it show me error: java.lang.ArrayIndexOutOfBoundsException: 6 at quickb.quicksortB(quickb.java:13) at quickb.main(quickb.java:32) what is wrong?

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• Force calling the derived class implementation within a generic function in C#?

  - by Adam Hardy

  Ok so I'm currently working with a set of classes that I don't have control over in some pretty generic functions using these objects. Instead of writing literally tens of functions that essentially do the same thing for each class I decided to use a generic function instead. Now the classes I'm dealing with are a little weird in that the derived classes share many of the same properties but the base class that they are derived from doesn't. One such property example is .Parent which exists on a huge number of derived classes but not on the base class and it is this property that I need to use. For ease of understanding I've created a small example as follows: class StandardBaseClass {} // These are simulating the SMO objects class StandardDerivedClass : StandardBaseClass { public object Parent { get; set; } } static class Extensions { public static object GetParent(this StandardDerivedClass sdc) { return sdc.Parent; } public static object GetParent(this StandardBaseClass sbc) { throw new NotImplementedException("StandardBaseClass does not contain a property Parent"); } // This is the Generic function I'm trying to write and need the Parent property. public static void DoSomething<T>(T foo) where T : StandardBaseClass { object Parent = ((T)foo).GetParent(); } } In the above example calling DoSomething() will throw the NotImplemented Exception in the base class's implementation of GetParent(), even though I'm forcing the cast to T which is a StandardDerivedClass. This is contrary to other casting behaviour where by downcasting will force the use of the base class's implementation. I see this behaviour as a bug. Has anyone else out there encountered this?

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• Maximize/Minimize is causing Close Button to be re-enabled after disabling it -- Why?

  - by Brainsick

  I have used P/Invoke to call GetSystemMenu and EnableMenuItem (win32api) to disable the close functionality. However, after minimizing or maximizing my Windows Forms application the button is re-enabled. Obviously minimizing or maximizing is causing the behavior, but how? I'm not sure where to look to prevent this behavior. Should I be preventing the maximize and minimize behavior or is there something particularly wrong with the way in which I P/Invoked the calls? Once the application (main form) has loaded, I call the static method from a button click. class PInvoke { // P/Invoke signatures [DllImport("user32.dll")] static extern IntPtr GetSystemMenu(IntPtr hWnd, bool bRevert); [DllImport("user32.dll")] static extern bool EnableMenuItem(IntPtr hMenu, uint uIDEnableItem, uint uEnable); // SysCommand (WM_SYSCOMMAND) constant internal const UInt32 SC_CLOSE = 0xF060; // Constants used with Add/Check/EnableMenuItem internal const UInt32 MF_BYCOMMAND = 0x00000000; internal const UInt32 MF_ENABLED = 0x00000000; internal const UInt32 MF_GRAYED = 0x00000001; internal const UInt32 MF_DISABLED = 0x00000002; /// <summary> /// Sets the state of the Close (X) button and the System Menu close functionality. /// </summary> /// <param name="window">Window or Form</param> /// <param name="bEnabled">Enabled state</param> public static void EnableCloseButton(IWin32Window window, bool bEnabled) { IntPtr hSystemMenu = GetSystemMenu(window.Handle, false); EnableMenuItem(hSystemMenu, SC_CLOSE, MF_BYCOMMAND | (bEnabled ? MF_ENABLED : MF_GRAYED)); } }

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• C#: How to implement a smart cache

  - by Svish

  I have some places where implementing some sort of cache might be useful. For example in cases of doing resource lookups based on custom strings, finding names of properties using reflection, or to have only one PropertyChangedEventArgs per property name. A simple example of the last one: public static class Cache { private static Dictionary<string, PropertyChangedEventArgs> cache; static Cache() { cache = new Dictionary<string, PropertyChangedEventArgs>(); } public static PropertyChangedEventArgs GetPropertyChangedEventArgsa(string propertyName) { if (cache.ContainsKey(propertyName)) return cache[propertyName]; return cache[propertyName] = new PropertyChangedEventArgs(propertyName); } } But, will this work well? For example if we had a whole load of different propertyNames, that would mean we would end up with a huge cache sitting there never being garbage collected or anything. I'm imagining if what is cached are larger values and if the application is a long-running one, this might end up as kind of a problem... or what do you think? How should a good cache be implemented? Is this one good enough for most purposes? Any examples of some nice cache implementations that are not too hard to understand or way too complex to implement?

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• Dilemma with two types and operator +

  - by user35443

  I have small problem with operators. I have this code: public class A { public string Name { get; set; } public A() { } public A(string Name) { this.Name = Name; } public static implicit operator B(A a) { return new B(a.Name); } public static A operator+(A a, A b) { return new A(a.Name + " " + b.Name); } } public class B { public string Name { get; set; } public B() { } public B(string Name) { this.Name = Name; } public static implicit operator A(B b) { return new A(b.Name); } public static B operator +(B b, B a) { return new B(b.Name + " " + a.Name); } } Now I want to know, which's conversion operator will be called and which's addition operator will be called in this operation: new A("a") + new B("b"); Will it be operator of A, or of B? (Or both?) Thanks....

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• ref and out parameters in C# and cannot be marked as variant.

  - by Water Cooler v2

  What does the statement mean? From here ref and out parameters in C# and cannot be marked as variant. 1) Does it mean that the following can not be done. public class SomeClass<R, A>: IVariant<R, A> { public virtual R DoSomething( ref A args ) { return null; } } 2) Or does it mean I cannot have the following. public delegate R Reader<out R, in A>(A arg, string s); public static void AssignReadFromPeonMethodToDelegate(ref Reader<object, Peon> pReader) { pReader = ReadFromPeon; } static object ReadFromPeon(Peon p, string propertyName) { return p.GetType().GetField(propertyName).GetValue(p); } static Reader<object, Peon> pReader; static void Main(string[] args) { AssignReadFromPeonMethodToDelegate(ref pReader); bCanReadWrite = (bool)pReader(peon, "CanReadWrite"); Console.WriteLine("Press any key to quit..."); Console.ReadKey(); } I tried (2) and it worked.

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• Using overloaded operator== in a generic function

  - by Dimitri C.

  Consider the following code: class CustomClass { public CustomClass(string value) { m_value = value; } public static bool operator==(CustomClass a, CustomClass b) { return a.m_value == b.m_value; } public static bool operator!=(CustomClass a, CustomClass b) { return a.m_value != b.m_value; } public override bool Equals(object o) { return m_value == (o as CustomClass).m_value; } public override int GetHashCode() { return 0; /* not needed */ } string m_value; } class G { public static bool enericFunction1<T>(T a1, T a2) where T : class { return a1.Equals(a2); } public static bool enericFunction2<T>(T a1, T a2) where T : class { return a1==a2; } } Now when I call both generic functions, one succeeds and one fails: var a = new CustomClass("same value"); var b = new CustomClass("same value"); Debug.Assert(G.enericFunction1(a, b)); // Succeeds Debug.Assert(G.enericFunction2(a, b)); // Fails Apparently, G.enericFunction2 executes the default operator== implementation instead of my override. Can anybody explain why this happens?

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• Efficiently get the size of a parameter pack up to a certain index

  - by NmdMystery

  I want to be able to determine the number of bytes that are in a subset of a parameter pack from 0 to a given index. Right now I'm using a non-constexpr way of doing this. Below is my code: template <size_t index, typename... args> struct pack_size_index; template <size_t index, typename type_t, typename... args> struct pack_size_index <index, type_t, args...> { static const size_t index_v = index; static const size_t value(void) { if (index_v > 0) { return sizeof(type_t) + pack_size_index<index - 1, args...>::value(); } return 0; } }; template <size_t index> struct pack_size_index <index> { static const size_t index_v = index; static const size_t value(void) { return 0; } }; Usage: //output: 5 (equal to 1 + 4) std::cout << pack_size_index<2, bool, float, int, double>::value() << std::endl; //output: 20 (equal to 8 + 8 + 4) std::cout << pack_size_index<3, double, double, float, int>::value() << std::endl; This gets the job done, but this uses runtime comparison and the resulting executable increases in size rapidly whenever this is used. What's a less expensive way of doing this?

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• is it good "form" to declare new classes in the same file ?

  - by hatorade

  I code in Python a lot, and I frequently create classes. Now, I'm not sure if this is good Python form, but I just declare a class in the same file as my main(). class foo { ... } I'm wondering if it's good form in Java to do the same? For example, class foo { public static int name; public static int numPoints; public static int[] points; } public class bar { public static void main(String[] args) { ... } } Does not throw errors in Eclipse, so it must be allowed. But is it okay to do? Would it be better to just declare this class in a separate file..? Edit: I just want to emphasize that my new class literally is just a container to hold the same type of data multiple times, and literally will only have like 3 values. So it's total about 5 lines of code. The question is - does this merit a new file?

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• Writing a recursive sorting algorithm of an array of integers

  - by 12345

  I am trying to write a recursive sorting algorithm for an array of integers. The following codes prints to the console: 3, 5, 2, 1, 1, 2, 6, 7, 8, 10, 20 The output should be sorted but somehow "it doesn't work". public static void main(String[] args) { int[] unsortedList = {20, 3, 1, 2, 1, 2, 6, 8, 10, 5, 7}; duplexSelectionSort(unsortedList, 0, unsortedList.length-1); for (int i = 0; i < unsortedList.length; i++) { System.out.println(unsortedList[i]); } } public static void duplexSelectionSort( int[] unsortedNumbers, int startIndex, int stopIndex) { int minimumIndex = 0; int maximumIndex = 0; if (startIndex < stopIndex) { int index = 0; while (index <= stopIndex) { if (unsortedNumbers[index] < unsortedNumbers[minimumIndex]) { minimumIndex = index; } if (unsortedNumbers[index] > unsortedNumbers[maximumIndex]) { maximumIndex = index; } index++; } swapEdges(unsortedNumbers, startIndex, stopIndex, minimumIndex, maximumIndex); duplexSelectionSort(unsortedNumbers, startIndex + 1, stopIndex - 1); } } public static void swapEdges( int[] listOfIntegers, int startIndex, int stopIndex, int minimumIndex, int maximumIndex) { if ((minimumIndex == stopIndex) && (maximumIndex == startIndex)) { swap(listOfIntegers, startIndex, stopIndex); } else { if (maximumIndex == startIndex) { swap(listOfIntegers, maximumIndex, stopIndex); swap(listOfIntegers, minimumIndex, startIndex); } else { swap(listOfIntegers, minimumIndex, startIndex); swap(listOfIntegers, maximumIndex, stopIndex); } } } public static void swap(int[] listOfIntegers, int index1, int index2) { int savedElementAtIndex1 = listOfIntegers[index1]; listOfIntegers[index1] = listOfIntegers[index2]; listOfIntegers[index2] = savedElementAtIndex1; }

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• math.Random isn't working right

  - by RandomlyKnighted

  I'm trying to simulate a coin flip using the code below. public class Coin { public static double result; int[] count = new count[2]; public static void flip() { result = Math.random(); } public static boolean isHeads() { if (result == 0.0) { count[0]++; return false; } else { count[1]++; return true; } } public static void main(String[] args) { flip(); isHeads(); System.out.println(count[0]); System.out.println(count[1]); } } For some reason Eclipse says that the import java.util.Random; is never used even though I'm clearly using it. I didn't put my for loop into the code above but it loops n number of times and then outputs the result. No matter how many times it loops it always returns that the result is greater than 0.0 which can't be right. Am I calling Math.random incorrectly?

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• Program that edits string and prints each word individually with C

  - by Michael_19

  I keep getting the error segmentation fault (core dumped) when I run my progam. #include<stdio.h> #include<stdlib.h> int nextword(char *str); int main(void) { char str[] = "Hello! Today is a beautiful day!!\t\n"; int i = nextword(str); while(i != -1) { printf("%s\n",&(str[i])); i = nextword(NULL); } return 0; } int nextword(char *str) { // create two static variables - these stay around across calls static char *s; static int nextindex; int thisindex; // reset the static variables if (str != NULL) { s = str; thisindex = 0; // TODO: advance this index past any leading spaces while (s[thisindex]=='\n' || s[thisindex]=='\t' || s[thisindex]==' ' ) thisindex++; } else { // set the return value to be the nextindex thisindex = nextindex; } // if we aren't done with the string... if (thisindex != -1) { nextindex = thisindex; // TODO: two things // 1: place a '\0' after the current word // 2: advance nextindex to the beginning // of the next word while (s[nextindex] != ' ' && s[nextindex] != '\0') nextindex++; str[nextindex] = '\0'; nextindex++; } return thisindex; } The goal of the program is to print each word in the string str[] to the console on a new line. I am a beginning programmer and this is an assignment so I must use this type of format (no string library allowed). I just would like to know where I went wrong and how I can fix it.

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• HttpContext.Items and Server.Transfer/Execute

  - by Rick Strahl

  A few days ago my buddy Ben Jones pointed out that he ran into a bug in the ScriptContainer control in the West Wind Web and Ajax Toolkit. The problem was basically that when a Server.Transfer call was applied the script container (and also various ClientScriptProxy script embedding routines) would potentially fail to load up the specified scripts. It turns out the problem is due to the fact that the various components in the toolkit use request specific singletons via a Current property. I use a static Current property tied to a Context.Items[] entry to handle this type of operation which looks something like this: /// <summary> /// Current instance of this class which should always be used to /// access this object. There are no public constructors to /// ensure the reference is used as a Singleton to further /// ensure that all scripts are written to the same clientscript /// manager. /// </summary> public static ClientScriptProxy Current { get { if (HttpContext.Current == null) return new ClientScriptProxy(); ClientScriptProxy proxy = null; if (HttpContext.Current.Items.Contains(STR_CONTEXTID)) proxy = HttpContext.Current.Items[STR_CONTEXTID] as ClientScriptProxy; else { proxy = new ClientScriptProxy(); HttpContext.Current.Items[STR_CONTEXTID] = proxy; } return proxy; } } The proxy is attached to a Context.Items[] item which makes the instance Request specific. This works perfectly fine in most situations EXCEPT when you’re dealing with Server.Transfer/Execute requests. Server.Transfer doesn’t cause Context.Items to be cleared so both the current transferred request and the original request’s Context.Items collection apply. For the ClientScriptProxy this causes a problem because script references are tracked on a per request basis in Context.Items to check for script duplication. Once a script is rendered an ID is written into the Context collection and so considered ‘rendered’: // No dupes - ref script include only once if (HttpContext.Current.Items.Contains( STR_SCRIPTITEM_IDENTITIFIER + fileId ) ) return; HttpContext.Current.Items.Add(STR_SCRIPTITEM_IDENTITIFIER + fileId, string.Empty); where the fileId is the script name or unique identifier. The problem is on the Transferred page the item will already exist in Context and so fail to render because it thinks the script has already rendered based on the Context item. Bummer. The workaround for this is simple once you know what’s going on, but in this case it was a bitch to track down because the context items are used in many places throughout this class. The trick is to determine when a request is transferred and then removing the specific keys. The first issue is to determine if a script is in a Trransfer or Execute call: if (HttpContext.Current.CurrentHandler != HttpContext.Current.Handler) Context.Handler is the original handler and CurrentHandler is the actual currently executing handler that is running when a Transfer/Execute is active. You can also use Context.PreviousHandler to get the last handler and chain through the whole list of handlers applied if Transfer calls are nested (dog help us all for the person debugging that). For the ClientScriptProxy the full logic to check for a transfer and remove the code looks like this: /// <summary> /// Clears all the request specific context items which are script references /// and the script placement index. /// </summary> public void ClearContextItemsOnTransfer() { if (HttpContext.Current != null) { // Check for Server.Transfer/Execute calls - we need to clear out Context.Items if (HttpContext.Current.CurrentHandler != HttpContext.Current.Handler) { List<string> Keys = HttpContext.Current.Items.Keys.Cast<string>().Where(s => s.StartsWith(STR_SCRIPTITEM_IDENTITIFIER) || s == STR_ScriptResourceIndex).ToList(); foreach (string key in Keys) { HttpContext.Current.Items.Remove(key); } } } } along with a small update to the Current property getter that sets a global flag to indicate whether the request was transferred: if (!proxy.IsTransferred && HttpContext.Current.Handler != HttpContext.Current.CurrentHandler) { proxy.ClearContextItemsOnTransfer(); proxy.IsTransferred = true; } return proxy; I know this is pretty ugly, but it works and it’s actually minimal fuss without affecting the behavior of the rest of the class. Ben had a different solution that involved explicitly clearing out the Context items and replacing the collection with a manually maintained list of items which also works, but required changes through the code to make this work. In hindsight, it would have been better to use a single object that encapsulates all the ‘persisted’ values and store that object in Context instead of all these individual small morsels. Hindsight is always 20/20 though :-}. If possible use Page.Items ClientScriptProxy is a generic component that can be used from anywhere in ASP.NET, so there are various methods that are not Page specific on this component which is why I used Context.Items, rather than the Page.Items collection.Page.Items would be a better choice since it will sidestep the above Server.Transfer nightmares as the Page is reloaded completely and so any new Page gets a new Items collection. No fuss there. So for the ScriptContainer control, which has to live on the page the behavior is a little different. It is attached to Page.Items (since it’s a control): /// <summary> /// Returns a current instance of this control if an instance /// is already loaded on the page. Otherwise a new instance is /// created, added to the Form and returned. /// /// It's important this function is not called too early in the /// page cycle - it should not be called before Page.OnInit(). /// /// This property is the preferred way to get a reference to a /// ScriptContainer control that is either already on a page /// or needs to be created. Controls in particular should always /// use this property. /// </summary> public static ScriptContainer Current { get { // We need a context for this to work! if (HttpContext.Current == null) return null; Page page = HttpContext.Current.CurrentHandler as Page; if (page == null) throw new InvalidOperationException(Resources.ERROR_ScriptContainer_OnlyWorks_With_PageBasedHandlers); ScriptContainer ctl = null; // Retrieve the current instance ctl = page.Items[STR_CONTEXTID] as ScriptContainer; if (ctl != null) return ctl; ctl = new ScriptContainer(); page.Form.Controls.Add(ctl); return ctl; } } The biggest issue with this approach is that you have to explicitly retrieve the page in the static Current property. Notice again the use of CurrentHandler (rather than Handler which was my original implementation) to ensure you get the latest page including the one that Server.Transfer fired. Server.Transfer and Server.Execute are Evil All that said – this fix is probably for the 2 people who are crazy enough to rely on Server.Transfer/Execute. :-} There are so many weird behavior problems with these commands that I avoid them at all costs. I don’t think I have a single application that uses either of these commands… Related Resources Full source of ClientScriptProxy.cs (repository) Part of the West Wind Web Toolkit Static Singletons for ASP.NET Controls Post © Rick Strahl, West Wind Technologies, 2005-2010Posted in ASP.NET  

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• After-meeting Free Pizza Social is back to Fladotnet's West Palm Beach .Net User Group

  - by Sam Abraham

  Sherlock Staffing is bringing back the free Pizza/Soda after-meeting social to Fladotnet's West Palm Beach .Net User Group. Group members will have ample time to network and share experiences while enjoying pizza and soda after each meeting. Alex Funkhouser, Sherlock Staffing's President and Chief Talent Agent, is a continuous supporter of the .Net community with Sherlock Staffing maintaining a strong presence in every user group and quickly stepping-in as sponsors to meet any arising community need. In addition to providing the Free Pizza and Soda, Sherlock Staffing will also maintain on-site presence to bring to members of the West Palm Beach .Net User Group the latest insider view on the Job Market and keep the group posted with available opportunities. Alex can be reached at: [email protected]. Check out Sherlock Staffing's Website at: http://www.sherstaff.com About Sherlock Staffing SherStaff is the premier staffing and consulting source for technical talent in Florida and beyond. The company provides recruiting and consulting services to both Fortune 1000 companies and to job candidates in a wide range of technology areas of expertise including the Microsoft Technologies, Oracle, WebSphere, Java/J2EE, and open source/Linux based technologies.  The primary focus is recruiting application developers, network engineers and database administrators. The company prides itself on the long term relationships established with both employers and employees to ensure placement of the best quality candidates in the top quality jobs.

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• We Don’t Need No Regions

  - by João Angelo

  If your code reaches a level where you want to hide it behind regions then you have a problem that regions won’t solve. Regions are good to hide things that you don’t want to have knowledge about such as auto-generated code. Normally, when you’re developing you end up reading more code than you write it so why would you want to complicate the reading process. I, for one, would love to have that one discussion around regions where someone convinces me that they solve a problem that has no other alternative solution, but I’m still waiting. The most frequent argument I hear about regions is that they allow you to structure your code, but why don’t just structure it using classes, methods and all that other stuff that OOP is about because at the end of the day, you should be doing object oriented programming and not region oriented programming. Having said that, I do believe that sometimes is helpful to have a quick overview of a code file contents and Visual Studio allows you to do just that through the Collapse to Definitions command (CTRL + M, CTRL + O) which collapses the members of all types; if you like regions, you should try this, it is much more useful to read all the members of a type than all the regions inside a type.

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• Preserving Permalinks

  - by Daniel Moth

  One of the things that gets me on a rant is websites that break permalinks. If you have posted something somewhere and there is a public URL pointing to it, that URL should never ever return a 404. You are breaking all websites that ever linked to you and you are breaking all search engine links to your content (that others will try and follow). It is a pet peeve of mine. So when I had to move my blog, obviously I would preserve the root URL (www.danielmoth.com/Blog/), but I also wanted to preserve every URL my blog has generated over the years. To be clear, our focus here is on the URL formatting, not the content migration which I'll talk about in my next post. In this post, I'll describe my solution first and then what it solves. 1. The IIS7 Rewrite Module and web.config There are a few ways you can map an old URL to a new one (so when requests to the old URL come in, they get redirected to the new one). The new blog engine I use (dasBlog) has built-in functionality to do that (Scott refers to it here). Instead, the way I chose to address the issue was to use the IIS7 rewrite module. The IIS7 rewrite module allows redirecting URLs based on pattern matching, regular expressions and, of course, hardcoded full URLs for things that don't fall into any pattern. You can configure it visually from IIS Manager using a handy dialog that allows testing patterns against input URLs. Here is what mine looked like after configuring a few rules: To learn more about this technology check out this video, the reference page and this overview blog post; all 3 pages have a collection of related resources at the bottom worth checking out too. All the visual configuration ends up in a web.config file at the root folder of your website. If you are on a shared hosting service, probably the only way you can use the Rewrite Module is by directly editing the web.config file. Next, I'll describe the URLs I had to map and how that manifested itself in the web.config file. What I did was create the rules locally using the GUI, and then took the generated web.config file and uploaded it to my live site. You can view my web.config here. 2. Monthly Archives Observe the difference between the way the two blog engines generate this type of URL Blogger: /Blog/2004_07_01_mothblog_archive.html dasBlog: /Blog/default,month,2004-07.aspx In my web.config file, the rule that deals with this is the one named "monthlyarchive_redirect". 3. Categories Observe the difference between the way the two blog engines generate this type of URL Blogger: /Blog/labels/Personal.html dasBlog: /Blog/CategoryView,category,Personal.aspx In my web.config file the rule that deals with this is the one named "category_redirect". 4. Posts Observe the difference between the way the two blog engines generate this type of URL Blogger: /Blog/2004/07/hello-world.html dasBlog: /Blog/Hello-World.aspx In my web.config file the rule that deals with this is the one named "post_redirect". Note: The decision is taken to use dasBlog URLs that do not include the date info (see the description of my Appearance settings). If we included the date info then it would have to include the day part, which blogger did not generate. This makes it impossible to redirect correctly and to have a single permalink for blog posts moving forward. An implication of this decision, is that no two blog posts can have the same title. The tool I will describe in my next post (inelegantly) deals with duplicates, but not with triplicates or higher. 5. Unhandled by a generic rule Unfortunately, the two blog engines use different rules for generating URLs for blog posts. Most of the time the conversion is as simple as the example of the previous section where a post titled "Hello World" generates a URL with the words separated by a hyphen. Some times that is not the case, for example: /Blog/2006/05/medc-wrap-up.html /Blog/MEDC-Wrapup.aspx or /Blog/2005/01/best-of-moth-2004.html /Blog/Best-Of-The-Moth-2004.aspx or /Blog/2004/11/more-windows-mobile-2005-details.html /Blog/More-Windows-Mobile-2005-Details-Emerge.aspx In short, blogger does not add words to the title beyond ~39 characters, it drops some words from the title generation (e.g. a, an, on, the), and it preserve hyphens that appear in the title. For this reason, we need to detect these and explicitly list them for redirects (no regular expression can help here because the full set of rules is not listed anywhere). In my web.config file the rule that deals with this is the one named "Redirect rule1 for FullRedirects" combined with the rewriteMap named "StaticRedirects". Note: The tool I describe in my next post will detect all the URLs that need to be explicitly redirected and will list them in a file ready for you to copy them to your web.config rewriteMap. 6. C# code doing the same as the web.config I wrote some naive code that does the same thing as the web.config: given a string it will return a new string converted according to the 3 rules above. It does not take into account the 4th case where an explicit hard-coded conversion is needed (the tool I present in the next post does take that into account). static string REGEX_post_redirect = "[0-9]{4}/[0-9]{2}/([0-9a-z-]+).html"; static string REGEX_category_redirect = "labels/([_0-9a-z-% ]+).html"; static string REGEX_monthlyarchive_redirect = "([0-9]{4})_([0-9]{2})_[0-9]{2}_mothblog_archive.html"; static string Redirect(string oldUrl) { GroupCollection g; if (RunRegExOnIt(oldUrl, REGEX_post_redirect, 2, out g)) return string.Concat(g[1].Value, ".aspx"); if (RunRegExOnIt(oldUrl, REGEX_category_redirect, 2, out g)) return string.Concat("CategoryView,category,", g[1].Value, ".aspx"); if (RunRegExOnIt(oldUrl, REGEX_monthlyarchive_redirect, 3, out g)) return string.Concat("default,month,", g[1].Value, "-", g[2], ".aspx"); return string.Empty; } static bool RunRegExOnIt(string toRegEx, string pattern, int groupCount, out GroupCollection g) { if (pattern.Length == 0) { g = null; return false; } g = new Regex(pattern, RegexOptions.IgnoreCase | RegexOptions.Compiled).Match(toRegEx).Groups; return (g.Count == groupCount); } Comments about this post welcome at the original blog.

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