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  • Streaming multiple TObjects to a TMemoryStream

    - by Altar
    I need to store multiple objects (most of them are TObject/non persistent) to a TMemoryStream, save the stream to disk and load it back. The objects need to be streamed one after each other. Some kind of universal container. I started to make several functions that store stuff to stream - for example function StreamReadString(CONST MemStream: TMemoryStream): string; StreamWriteString(CONST MemStream: TMemoryStream; s: string); However, it seems that I need to rewrite a lot of code. One of the many examples is TStringList.LoadFromStream that will not work so it needs to be rewritten. This is because TStringList needs to be the last object in the stream (it reads from current position to the end of the stream). Anybody knows a library that provide basic functionality like this? I am using Delphi 7 so RTTI won't help too much.

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  • Redirecting one file to another using dub2 and strtok

    - by Sergiy Zakharov
    OK, here goes. I have to write a program, in which I need to use strtok and dup2 to redirect one file to another, but I need to also have the user to actually put the command cat < file1 file2, but not from the shell, but instead by using my program. That's why I need strtok. And the reason my program doesn't work is probably because of that, because I don't really understand how strtok works. I found a similar program on the internet, but they just take the ls command and redirect it to the file. That's it. My program is much more complicated. I mean, it would've been easier just to say in shell cat < file1 file2, but for some reason they want us to do it this way. So, anyways, here is what I have so far (here I just combined what I have found on the internet with what I already had from before. We had to do something similar but then the user would just go ls or ls -l. Very simple stuff. This is much harder, for me, at least.) #include <fcntl.h> #include <unistd.h> #include <stdio.h> #include <errno.h> #include <sys/wait.h> #include <string.h> int main() { pid_t pid; char line[256]; char *args[129]; int i; int fd; int status; char *temp; while (1) { printf(">"); if (fgets(line, 256, stdin) == 0) { exit(0); } else { pid = fork(); if (pid == 0) { i = 0; temp = strtok("<",line); while (temp != NULL) { args[i++] = temp; temp = strtok(">",line); args[i] = '\0'; } fd = open("hello", O_RDONLY); dup2(fd, STDIN_FILENO); fd = open("world", O_WRONLY|O_CREAT|O_TRUNC, S_IRWXU); dup2(fd, STDOUT_FILENO ); close(fd); execvp(args[0], args); } else { close(fd); wait(&status); } } } } Any help would be greatly appreciated.

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  • How to use the vtable to determine class type

    - by Alex Silverman
    I was recently on an interview for a position where C/C++ is the primary language and during one question I was told that it's possible to use the vtable to determine which class in a hierarchy a base pointer actually stores. So if, for example you have class A { public: A() {} virtual ~A() {} virtual void method1() {} }; class B : public A { public: B() {} virtual ~B() {} virtual void method1() {} }; and you instantiate A * pFoo = new B(), is it indeed possible to use the vtable to determine whether pFoo contains a pointer to an instance of A or B?

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  • error in encryption program

    - by Raja
    #include<iostream> #include<math.h> #include<string> using namespace std; int gcd(int n,int m) { if(m<=n && n%m ==0) return m; if(n<m) return gcd(m,n); else return gcd(m,n%m); } int REncryptText(char m) { int p = 11, q = 3; int e = 3; int n = p * q; int phi = (p - 1) * (q - 1); int check1 = gcd(e, p - 1); int check2 = gcd(e, q - 1); int check3 = gcd(e, phi); // // Compute d such that ed = 1 (mod phi) //i.e. compute d = e-1 mod phi = 3-1 mod 20 //i.e. find a value for d such that phi divides (ed-1) //i.e. find d such that 20 divides 3d-1. //Simple testing (d = 1, 2, ...) gives d = 7 // double d = Math.Pow(e, -1) % phi; int d = 7; // public key = (n,e) // (33,3) //private key = (n,d) //(33 ,7) double g = pow(m,e); int ciphertext = g %n; // Now say we want to encrypt the message m = 7, c = me mod n = 73 mod 33 = 343 mod 33 = 13. Hence the ciphertext c = 13. //double decrypt = Math.Pow(ciphertext, d) % n; return ciphertext; } int main() { char plaintext[80],str[80]; cout<<" enter the text you want to encrpt"; cin.get(plaintext,79); int l =strlen(plaintext); for ( int i =0 ; i<l ; i++) { char s = plaintext[i]; str[i]=REncryptText(s); } for ( int i =0 ; i<l ; i++) { cout<<"the encryption of string"<<endl; cout<<str[i]; } return 0; }

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  • Haskell. Numbers in binary numbers. words

    - by Katja
    Hi! I need to code words into binary numbers. IN: "BCD..." OUT:1011... I have written already funktion for coding characters into siple numbers IN: 'C' OUT: 3 IN: 'c' OUT: 3 lett2num :: Char -> Int lett2num x | (ord 'A' <= ord x) && (ord x <= ord 'Z') = (ord x - ord 'A') + 1 | (ord 'a' <= ord x) && (ord x <= ord 'z') = (ord x - ord 'a') +1 num2lett :: Int -> Char num2lett n | (n <= ord 'A') && (n <= ord 'Z') = chr(ord 'A'+ n - 1) | (n <= ord 'a') && (n <= ord 'Z') = chr(ord 'A'+ n - 1) I wrote as well function for codind simple numbers into binary. num2bin :: Int->[Int] num2bin 0 = [] num2bin n | n>=0 = n `mod` 2 : (num2bin( n `div` 2)) | otherwise = error but I donw want those binary numbers to be in a list how can I get rid of the lists? Thanks

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  • Hiredis waiting for message

    - by Vivek Goel
    I am using hiredis C library to connect to redis server. I am not able to figure out how to wait for new messages after subscribing to new message. My code look like: signal(SIGPIPE, SIG_IGN ); struct event_base *base = event_base_new(); redisAsyncContext *c = redisAsyncConnect("127.0.0.1", 6379); if (c->err) { /* Let *c leak for now... */ printf("Error: %s\n", c->errstr); return 1; } redisLibeventAttach(c, base); redisAsyncSetConnectCallback(c, connectCallback); redisAsyncSetDisconnectCallback(c, disconnectCallback); redisAsyncCommand(c, NULL, NULL, "SET key %b", argv[argc - 1], strlen(argv[argc - 1])); redisAsyncCommand(c, getCallback, (char*) "end-1", "GET key"); redisAsyncCommand(c, getCallback, (char*) "end-1", "SUBSCRIBE foo"); Now how to tell hiredis to wait for message on channel ?

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  • segmentation fault

    - by gcc
    int num_arrays; char *p[20]; char tempc; int i=0; do { p[i]=malloc(sizeof(int)); scanf("%s",p[i]); tempc=p[i]; ++i; }while(tempc=='x'); num_arrays=atoi(p[0]); When i write num_arrays=atoi(..),gcc give me segmentation fault or memory stack is exceeded, I don't understand why it behaves like that can anyone explain, why?

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  • Unmanaged C++ instantiation question

    - by Jim Jones
    Want to verify that my understanding of how this works. Have an unmanaged C++ Class with one public instance variable: char* character_encoding; and whose only constructor is defined as: TF_StringList(const char* encoding = "cp_1252"); when I use this class in either managed or unmanaged C++, the first thing I do is declare a pointer to an object of this class: const TF_StringList * categories; Then later I instantiate it: categories = new TF_StringList(); this gives me a pointer to an object of type TF_StringList whose variable character_encoding is set to "cp_1252"; So, is all that logic valid? Jim

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  • How to call a bool function...

    - by Gerri
    Hello, I did not see anything that address my particular code problem. I have a bool function in a class; the bool function is named: bool Triplet::operator ==(const Triplet& operand)const And I am trying to call it in Main but having problems just getting the call right. Apparently if I leave out any thing in the wording it gives an error that I have too few aruguments and if I try to use the entire wording of the function, I get the error that I need a semi-colon, but I already have a semi-colon at the end of the call, so I know that something else is wrong and I simply cannot figure out what is wrong! Any help would be appreciated! Thanks in advance.

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  • PLEASE HELP JAVA/SQL question

    - by fred-ghosn
    Hello everyone, well I'm new here and I really need some help.. I want to create a table and this table's name will be inserted from a textfield. However when I run the query it's giving me an error, any help on this one? Ill paste the code here: public boolean CreateTable() { TableNumber=jTextField4.getText(); try { String password = null; String s = "CREATE TABLE '"+TableNumber+'" (Item char(50),Price char(50))"; ConnectionForOrders(); stmt = conn.createStatement(); stmt.executeUpdate(s); boolean f=false; ConnectionForOrdersclose();

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  • emacs: how do I use edebug on code that is defined in a macro?

    - by Cheeso
    I don't even know the proper terminology for this lisp syntax, so I don't know if the words I'm using to ask the question, make sense. But the question makes sense, I'm sure. So let me just show you. cc-mode (cc-fonts.el) has things called "matchers" which are bits of code that run to decide how to fontify a region of code. That sounds simple enough, but the matcher code is in a form I don't completely understand, with babckticks and comma-atsign and just comma and so on, and furthermore it is embedded in a c-lang-defcost, which itself is a macro. And I want to run edebug on that code. Look: (c-lang-defconst c-basic-matchers-after "Font lock matchers for various things that should be fontified after generic casts and declarations are fontified. Used on level 2 and higher." t `(;; Fontify the identifiers inside enum lists. (The enum type ;; name is handled by `c-simple-decl-matchers' or ;; `c-complex-decl-matchers' below. ,@(when (c-lang-const c-brace-id-list-kwds) `((,(c-make-font-lock-search-function (concat "\\<\\(" (c-make-keywords-re nil (c-lang-const c-brace-id-list-kwds)) "\\)\\>" ;; Disallow various common punctuation chars that can't come ;; before the '{' of the enum list, to avoid searching too far. "[^\]\[{}();,/#=]*" "{") '((c-font-lock-declarators limit t nil) (save-match-data (goto-char (match-end 0)) (c-put-char-property (1- (point)) 'c-type 'c-decl-id-start) (c-forward-syntactic-ws)) (goto-char (match-end 0))))))) I am reading up on lisp syntax to figure out what those things are and what to call them, but aside from that, how can I run edebug on the code that follows the comment that reads ;; Fontify the identifiers inside enum lists. ? I know how to run edebug on a defun - just invoke edebug-defun within the function's definition, and off I go. Is there a corresponding thing I need to do to edebug the cc-mode matcher code forms?

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  • passin structure form VC++ to C#

    - by Anu
    Hi, im using C# dll in VC++ application.I have somedetails in VC++ like PageNumer pageTitle PageDesc BoxDetail I have to pass this to C# Dll. So i made one structure in VC++,then i pas that to C#.But i could't do that.Pls help mw. VC++ Function: struct SCS3OverVwPg { __int32 iOvrPgNo; char sOvrPgTitle[30]; //OverView Page Title }; void CToolTab::SendOverview() { SCS3OverVwPg *pOverVw = 0; pOverVw = new SCS3OverVwPg; Globals1::gwtoolbar->SetTree(pOverVw); } C# function: public struct SCS3Over { Int32 iOvrPgNo; char[] sOvrPgTitle; } public void SetTree(SCS3Over x) { MessageBox.Show("Data received"); } If i do like this,it shows error error C2664: 'Tabcontrol::ToolBar::SetTree' : cannot convert parameter 1 from 'SCS3OverVwPg *' to 'SCS3Over' IF i change name in C# dll to SCS3OverwPg, it show error of structure redifinition Pls help me.

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  • C++ linked list based tree structure. Sanely move nodes between lists.

    - by krunk
    The requirements: Each Node in the list must contain a reference to its previous sibling Each Node in the list must contain a reference to its next sibling Each Node may have a list of child nodes Each child Node must have a reference to its parent node Basically what we have is a tree structure of arbitrary depth and length. Something like: -root(NULL) --Node1 ----ChildNode1 ------ChildOfChild --------AnotherChild ----ChildNode2 --Node2 ----ChildNode1 ------ChildOfChild ----ChildNode2 ------ChildOfChild --Node3 ----ChildNode1 ----ChildNode2 Given any individual node, you need to be able to either traverse its siblings. the children, or up the tree to the root node. A Node ends up looking something like this: class Node { Node* previoius; Node* next; Node* child; Node* parent; } I have a container class that stores these and provides STL iterators. It performs your typical linked list accessors. So insertAfter looks like: void insertAfter(Node* after, Node* newNode) { Node* next = after->next; after->next = newNode; newNode->previous = after; next->previous = newNode; newNode->next = next; newNode->parent = after->parent; } That's the setup, now for the question. How would one move a node (and its children etc) to another list without leaving the previous list dangling? For example, if Node* myNode exists in ListOne and I want to append it to listTwo. Using pointers, listOne is left with a hole in its list since the next and previous pointers are changed. One solution is pass by value of the appended Node. So our insertAfter method would become: void insertAfter(Node* after, Node newNode); This seems like an awkward syntax. Another option is doing the copying internally, so you'd have: void insertAfter(Node* after, const Node* newNode) { Node *new_node = new Node(*newNode); Node* next = after->next; after->next = new_node; new_node->previous = after; next->previous = new_node; new_node->next = next; new_node->parent = after->parent; } Finally, you might create a moveNode method for moving and prevent raw insertion or appending of a node that already has been assigned siblings and parents. // default pointer value is 0 in constructor and a operator bool(..) // is defined for the Node bool isInList(const Node* node) const { return (node->previous || node->next || node->parent); } // then in insertAfter and friends if(isInList(newNode) // throw some error and bail I thought I'd toss this out there and see what folks came up with.

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  • Dynamic allocated array is not freed

    - by Stefano
    I'm using the code above to dynamically allocate an array, do some work inside the function, return an element of the array and free the memory outside of the function. But when I try to deallocate the array it doesn't free the memory and I have a memory leak. The debugger pointed to the myArray variable shows me the error CXX0030. Why? struct MYSTRUCT { char *myvariable1; int myvariable2; char *myvariable2; .... }; void MyClass::MyFunction1() { MYSTRUCT *myArray= NULL; MYSTRUCT *myElement = this->MyFunction2(myArray); ... delete [] myArray; } MYSTRUCT* MyClass::MyFunction2(MYSTRUCT *array) { array = (MYSTRUCT*)operator new(bytesLength); ... return array[X]; }

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  • Why is comparing against "end()" iterator legal?

    - by sharptooth
    According to C++ standard (3.7.3.2/4) using (not only dereferencing, but also copying, casting, whatever else) an invalid pointer is undefined behavior (in case of doubt also see this question). Now the typical code to traverse an STL containter looks like this: std::vector<int> toTraverse; //populate the vector for( std::vector<int>::iterator it = toTraverse.begin(); it != toTraverse.end(); ++it ) { //process( *it ); } std::vector::end() is an iterator onto the hypothetic element beyond the last element of the containter. There's no element there, therefore using a pointer through that iterator is undefined behavior. Now how does the != end() work then? I mean in order to do the comparison an iterator needs to be constructed wrapping an invalid address and then that invalid address will have to be used in a comparison which again is undefined behavior. Is such comparison legal and why?

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  • Prolog .. Can i convert from a list of chars to a string or term in Prolog !!

    - by AhmadAssaf
    i use read_line_to_codes(Stream,Line) to read a line from a file .. first is there any way to read a line and assign it to a term in prolog ?? if not i managed to read a line and put it in this char list .. now this char list contains spaces .. which is bad .. so i want to convert it to a term or a string in prolog so that i can process it easier .. spaces cannot be atoms so thats a problem .. i appreciate the help !!

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  • Is calling of overload operator-> resolved at compile time?

    - by Brent
    when I tried to compile the code: (note: func and func2 is not typo) struct S { void func2() {} }; class O { public: inline S* operator->() const; private: S* ses; }; inline S* O::operator->() const { return ses; } int main() { O object; object->func(); return 0; } there is a compile error reported: D:\code>g++ operatorp.cpp -S -o operatorp.exe operatorp.cpp: In function `int main()': operatorp.cpp:27: error: 'struct S' has no member named 'func' it seems that invoke the overloaded function of "operator-" is done during compile time? I'd added "-S" option for compile only.

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  • test cases for testing a strtok-alike function [C++]

    - by Neeraj
    Consider the following class definition: class StrToTokens { StrToTokens(const char* str, const char* delimiters = "\t\r\n"); //constructor string getNextToken(); void reset(); bool empty(); } Can someone list some good testcases to test the above class. A few I could think of are: empty string, empty delimiters, repeated delimiters, consecutive delimiters, string with only delimiters. However, the interviewer expected some more(better ones). Can you help out. Thanks.

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  • C++ catch constructor exception

    - by aaa
    hi. I do not seem to understand how to catch constructor exception. Here is relevant code: struct Thread { rysq::cuda::Fock fock_; template<class iterator> Thread(const rysq::cuda::Centers &centers, const iterator (&blocks)[4]) : fock_() { if (!fock_) throw; } }; Thread *ct; try { ct = new Thread(centers_, blocks); } catch(...) { return false; } // catch never happens, So catch statement do not execute and I get unhandled exception. What did I do wrong? this is straight C++ using g++.

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  • C: using clock() to measure time in multi-threaded programs

    - by Shinka
    I've always used clock() to measure how much time my application took from start to finish, as; int main(int argc, char *argv[]) { const clock_t START = clock(); // ... const double T_ELAPSED = (double)(clock() - START) / CLOCKS_PER_SEC; } Since I've started using POSIX threads this seem to fail. It looks like clock() increases N times faster with N threads. As I don't know how many threads are going to be running simultaneously, this approach fails. So how can I measure how much time has passed ?

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  • UInt32 to IntPtr

    - by ffenix
    I have the following problem: public class ListenThread : SocketInvoke { [DllImport("Ws2_32", CharSet = CharSet.Auto)] public unsafe static extern UInt32 WSAWaitForMultipleEvents(UInt32 cEvents, IntPtr hEventObject, UInt32 fWaitAll, UInt32 dwTimeout, Boolean fAlertable); public void ListenConnections(NetSharedData data) { while (true) { unsafe { if (WSAWaitForMultipleEvents((UInt32)1, data.signal, (UInt32)0, (UInt32)100, false) != WSA_WAIT_TIMEOUT) { } } } } data.signal is a UInt32 how i can cast it to IntPtr?, i try: IntPtr signal = (IntPtr)data.signal; but it doesn't work because i need a pointer to data.signal (UInt32) type and not the int value as an pointer, that will make a memory exception. An C++ example of what i need: int signal = 0; int* psignal = &signal;

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  • Iterator category

    - by Knowing me knowing you
    In code: //I know that to get this effect (being able to use it with std algorithms) I can inherit like I did in line below: class Iterator //: public std::iterator<std::bidirectional_iterator_tag,T> { private: T** itData_; public: //BUT I WOULD LIKE TO BE ABLE TO DO IT BY HAND AS WELL typedef std::bidirectional_iterator_tag iterator_category; typedef T* value_type;//SHOULD IT BE T AS value_type or T*? typedef std::ptrdiff_t difference_type; typedef T** pointer;//SHOULD IT BE T* AS pointer or T**? typedef T*& reference;//SHOULD IT BE T& AS reference or T*&? }; Basically what I'm asking is if I have my variable of type T** in iterator class is it right assumption that value type for this iterator will be T* and so on as I described in comments in code, right next to relevant lines. Thank you.

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  • Javascript pass reference by value

    - by Carlos R. Batista
    Im having this weird reference issue when im trying to get a JSON file through query: var themeData; $.getJSON("json/sample.js", function(data) { themeData = data.theme; console.log(themeData.sample[0].description); }); console.log(themeData.sample[0].description); The first console.log works, the second doesnt. Im guessing because "data" already expired by the time the script gets there and themeData is just a mere pointer to "data". Is there a ways I can make sure themeData gets a duplicate of "data" and not just a pointer to it?

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  • How to extract img src, title and alt from html using php?

    - by Sam
    I would like to create a page where all images which reside on my website are listed with title and alternative representation. I already wrote me a little program to find and load all html files, but now I am stuck at how to extract src, title and alt from the html < img src="/image/fluffybunny.jpg" title="Harvey the bunny" alt="a cute little fluffy bunny"/ I guess this should be done with some regex, but since the order of the tags may vary, and I need all of them, I don't really know how to parse this in an elegant way (I could do it the hard char by char way, but thats painful).

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