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  • subscript requires array or pointer ERROR

    - by Kristian
    Hi, I know what is my mistake can't figer how to solve it. Im writing an winAPI that counts how many 'a' characters are found is a givien file. Im still getting the error " subscript requires array or pointer " (please find the comment in the code) #include "stdafx.h" #include <windows.h> int _tmain(int argc, _TCHAR* argv[]) { WCHAR str=L'a'; HANDLE A; TCHAR *fn; fn=L"d:\\test.txt"; A= CreateFile(fn,GENERIC_READ,0,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,NULL); if(A==INVALID_HANDLE_VALUE) { _tprintf(L"cannot open file \n"); } else { DWORD really; int countletter; int stringsize; do { BYTE x[1024]; ReadFile(A,x,1024,&really,NULL); stringsize = sizeof(really); for(int i =0;i<stringsize;i++) { if(really[i]==str) //here Im getting the error countletter++; } }while(really==1024); CloseHandle(A); _tprintf(L"NUmbers of A's found is %d \n",countletter); } return 0; } now I know I can't make comparesion between array and a WCHAR but hw to fix it ?

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  • C# Convert string to nullable type (int, double, etc...)

    - by Nathan Koop
    I am attempting to do some data conversion. Unfortunately, much of the data is in strings, where it should be int's or double, etc... So what I've got is something like: double? amount = Convert.ToDouble(strAmount); The problem with this approach is if strAmount is empty, if it's empty I want it to amount to be null, so when I add it into the database the column will be null. So I ended up writing this: double? amount = null; if(strAmount.Trim().Length>0) { amount = Convert.ToDouble(strAmount); } Now this works fine, but I now have five lines of code instead of one. This makes things a little more difficult to read, especially when I have a large amount of columns to convert. I thought I'd use an extension to the string class and generic's to pass in the type, this is because it could be a double, or an int, or a long. So I tried this: public static class GenericExtension { public static Nullable<T> ConvertToNullable<T>(this string s, T type) where T: struct { if (s.Trim().Length > 0) { return (Nullable<T>)s; } return null; } } But I get the error: Cannot convert type 'string' to 'T?' Is there a way around this? I am not very familiar with creating methods using generics.

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  • C++ Loop - Need variable to accumulate sum

    - by user1780064
    I'm writing a program to ask the user to enter a value between 5 and 21 (inclusive). If the number entered is not in this range, it prints, "Please try again". If the number is within the range, I need to take that number, and print the sum of all the numbers from 1 to the value entered. So if the user entered "7", the sum would be "28". I successfully wrote the first loop, in the case of the number not being within the range, but cannot figure out how to run the second loop- whether to use a while, do-while, or for loop. Please advise. #include <iostream> int main () { int uservalue; int count; int sum; //Prompt user for input do { cout << "Enter a value from 5 to 21: "; cin >> uservalue; if (uservalue < 5 || uservalue > 21) cout << "Value out of range. Try again..." << endl; } while (uservalue < 5 || uservalue > 21); cout << endl; //Loop to accumulate sum for (count = 1, count < uservalue, count++;) { sum = uservalue + count; if (uservalue <= 5 || uservalue <= 21) cout << the sum is " << sum << endl; } return 0; }

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  • What wrapper class in C++ should I use for automated resource management?

    - by Vilx-
    I'm a C++ amateur. I'm writing some Win32 API code and there are handles and weirdly compositely allocated objects aplenty. So I was wondering - is there some wrapper class that would make resource management easier? For example, when I want to load some data I open a file with CreateFile() and get a HANDLE. When I'm done with it, I should call CloseHandle() on it. But for any reasonably complex loading function there will be dozens of possible exit points, not to mention exceptions. So it would be great if I could wrap the handle in some kind of wrapper class which would automatically call CloseHandle() once execution left the scope. Even better - it could do some reference counting so I can pass it around in and out of other functions, and it would release the resource only when the last reference left scope. The concept is simple - but is there something like that in the standard library? I'm using Visual Studio 2008, by the way, and I don't want to attach a 3rd party framework like Boost or something.

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  • C++ iterator and const_iterator problem for own container class

    - by BaCh
    Hi there, I'm writing an own container class and have run into a problem I can't get my head around. Here's the bare-bone sample that shows the problem. It consists of a container class and two test classes: one test class using a std:vector which compiles nicely and the second test class which tries to use my own container class in exact the same way but fails miserably to compile. #include <vector> #include <algorithm> #include <iterator> using namespace std; template <typename T> class MyContainer { public: class iterator { public: typedef iterator self_type; inline iterator() { } }; class const_iterator { public: typedef const_iterator self_type; inline const_iterator() { } }; iterator begin() { return iterator(); } const_iterator begin() const { return const_iterator(); } }; // This one compiles ok, using std::vector class TestClassVector { public: void test() { vector<int>::const_iterator I=myc.begin(); } private: vector<int> myc; }; // this one fails to compile. Why? class TestClassMyContainer { public: void test(){ MyContainer<int>::const_iterator I=myc.begin(); } private: MyContainer<int> myc; }; int main(int argc, char ** argv) { return 0; } gcc tells me: test2.C: In member function ‘void TestClassMyContainer::test()’: test2.C:51: error: conversion from ‘MyContainer::iterator’ to non-scalar type ‘MyContainer::const_iterator’ requested I'm not sure where and why the compiler wants to convert an iterator to a const_iterator for my own class but not for the STL vector class. What am I doing wrong?

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  • Node.js/Express Partials problem: Can't be nested too deep?

    - by heorling
    I'm learning Node.js, Express, haml.js and liking it. I've run into a prety annoying problem though. I'm pretty new to this but have been getting nice results so far. I'm writing a jquery heavy web app that relies on a table containing divs. The divs slide around, switch back and fourth and are resized etc to my hearts content. What I'm looking for a way to switch (template?) the divs. Since I've been building in express and mimicking the chat example it would make sense to use partials. The rub is that I've been using inexplicit divs in haml, held within a td. The divs are cunstructed as follows: %tr %td .class1.class2.class3.classetc Which has worked fine cross browser. Parsing the classes works great for the js code to pass arguments around, fetch values etc. What I'd like to be able to do is something like: %tr %td .class1.class2.class3.classetc %ul#messages != this.partial('message.html.haml', { collection: messages }) Any combination I've tried with this has failed however. And I might have tried them all. If I could put a partial into that div I'd probably be set. And you can nest them as long as you use #ids instead of .classes. But if you use more than one class it breaks! I think that's the most accurate way of summing it up. How do you do this? I've checked out various templating solutions like mu.js and micro template like by John Resig. I earlier checked out this thread on templating engines. It's very possible I'm making some fundamental mistake here, I'm new to this. What's a good way to do this?

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  • Using a variable derived from a drop-down list as the column name in a select statement ... Access DB

    - by user1459698
    I'm working with the world's worst DB that was already here so don't blame me for that. So, here's what I have so far ... module = txtModule.value presstype = txtPressType.value SQL_query = "SELECT * FROM tbl_spareparts WHERE '"& module &"' <> '""' AND '"& module &"' = '"& presstype &"' AND Manufacturer = '"& txtsrch.value &"' ORDER BY SAP_Part_No" Set rsData = conn.Execute(SQL_query) This brings up the following SQL statement: SELECT * FROM tbl_spareparts WHERE 'Banyan_Module' <> '"' AND 'Banyan_Module' = 'PB' AND Manufacturer = 'Tester' ORDER BY SAP_Part_No Is there any way I can use the module variable as a column name - obviously the ''s around the column name are causing an error. This is really bothering me. BTW, I'm writing this in VBScript inside a .HTA application page as it has to run locally on tech PCs. Thanks. R.

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  • How to filter and intercept Linux packets by using net_dev_add() API?

    - by Khajavi
    I'm writing ethernet network driver for linux. I want to receive packets, edit and resend them. I know how to edit the packet in packet_interceptor function, but how can I drop incoming packets in this function?? #include <linux/netdevice.h> #include <linux/skbuff.h> #include <linux/ip.h> #include <net/sock.h> struct packet_type my_proto; int packet_interceptor(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) { // I dont want certain packets go to upper in net_devices for further processing. // How can I drop sk_buff here?! return 0; } static int hello_init( void ) { printk(KERN_INFO "Hello, world!\n"); my_proto.type = htons(ETH_P_ALL); my_proto.dev = NULL; my_proto.func = packet_interceptor; dev_add_pack(&my_proto); return 0; } static void hello_exit(void) { dev_remove_pack(&my_proto); printk(KERN_INFO "Bye, world\n"); } module_init(hello_init); module_exit(hello_exit);

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  • How to import a module from PyPI when I have another module with the same name

    - by kuzzooroo
    I'm trying to use the lockfile module from PyPI. I do my development within Spyder. After installing the module from PyPI, I can't import it by doing import lockfile. I end up importing anaconda/lib/python2.7/site-packages/spyderlib/utils/external/lockfile.py instead. Spyder seems to want to have the spyderlib/utils/external directory at the beginning of sys.path, or at least none of the polite ways I can find to add my other paths get me in front of spyderlib/utils/external. I'm using python2.7 but with from __future__ import absolute_import. Here's what I've already tried: Writing code that modifies sys.path before running import lockfile. This works, but it can't be the correct way of doing things. Circumventing the normal mechanics of importing in Python using the imp module (I haven't gotten this to work yet, but I'm guessing it could be made to work) Installing the package with something like pip install --install-option="--prefix=modules_with_name_collisions" package_name. I haven't gotten this to work yet either, but I'm guess it could be made to work. It looks like this option is intended to create an entirely separate lib tree, which is more than I need. Source Using pip install --target=lockfile_from_pip. The files show up in the directory where I tell them to go, but import doesn't find them. And in fact pip uninstall can't find them either. I get Cannot uninstall requirement lockfile-from-pip, not installed and I guess I will just delete the directories and hope that's clean. Source So what's the preferred way for me to get access to the PyPI lockfile module?

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  • How to mock/stub a directory of files and their contents using RSpec?

    - by John Topley
    A while ago I asked "How to test obtaining a list of files within a directory using RSpec?" and although I got a couple of useful answers, I'm still stuck, hence a new question with some more detail about what I'm trying to do. I'm writing my first RubyGem. It has a module that contains a class method that returns an array containing a list of non-hidden files within a specified directory. Like this: files = Foo.bar :directory => './public' The array also contains an element that represents metadata about the files. This is actually a hash of hashes generated from the contents of the files, the idea being that changing even a single file changes the hash. I've written my pending RSpec examples, but I really have no idea how to implement them: it "should compute a hash of the files within the specified directory" it "shouldn't include hidden files or directories within the specified directory" it "should compute a different hash if the content of a file changes" I really don't want to have the tests dependent on real files acting as fixtures. How can I mock or stub the files and their contents? The gem implementation will use Find.find, but as one of the answers to my other question said, I don't need to test the library. I really have no idea how to write these specs, so any help much appreciated!

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  • How to limit TCP writes to particular size and then block untlil the data is read

    - by ustulation
    {Qt 4.7.0 , VS 2010} I have a Server written in Qt and a 3rd party client executable. Qt based server uses QTcpServer and QTcpSocket facilities (non-blocking). Going through the articles on TCP I understand the following: the original implementation of TCP mentioned the negotiable window size to be a 16-bit value, thus maximum being 65535 bytes. But implementations often used the RFC window-scale-extension that allows the sliding window size to be scalable by bit-shifting to yield a maximum of 1 gigabyte. This is implementation defined. This could have resulted in majorly different window sizes on receiver and sender end as the server uses Qt facilities without hardcoding any window size limit. Client 1st asks for all information it can based on the previous messages from the server before handling the new (accumulating) incoming messages. So at some point Server receives a lot of messages each asking for data of several MB's. This the server processes and puts it into the sender buffer. Client however is unable to handle the messages at the same pace and it seems that client’s receiver buffer is far smaller (65535 bytes maybe) than sender’s transmit window size. The messages thus get accumulated at sender’s end until the sender’s buffer is full too after which the TCP writes on sender would block. This however does not happen as sender buffer is much larger. Hence this manifests as increase in memory consumption on the sender’s end. To prevent this from happening, I used Qt’s socket’s waitForBytesWritten() with timeout set to -1 for infinite waiting period. This as I see from the behaviour blocks the thread writing TCP data until the data has actually been sensed by the receiver’s window (which will happen when earlier messages have been processed by the client at application level). This has caused memory consumption at Server end to be almost negligible. is there a better alternative to this (in Qt) if i want to restrict the memory consumption at server end to say x MB's? Also please point out if any of my understandings is incorrect.

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  • Can I get a reference to an object created in a jQuery plugin?

    - by gargantaun
    Perhaps my brain is fried, but I'm writing a plugin that created an tweaks an element, but also creates an object that i'd like access to. So the plugin looks like this (function ($) { $.fn.myPlugin = function () { return this.each(function () { // do some stuff to the element... this.objectInstance = new usefulObject(); }); }; })(jQuery); function usefulObject(){ // useful object properties and methods.... this.doSomething = function(){ alert("Don't google Google. You'll break the internet."); } } so when I call the plugin, I also want to be able to get access to that usefulObject that I created. I thought something like this might work.... tweakedElement = $("#someDiv").myPlugin(); tweakedElement.objectInstance.doSomething(); ... but that's not working. How can I achieve this? Can I achieve this? Answers on a postcard, or down below, whichever suits you.

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  • Code coverage with phpunit; can't get to one place.

    - by HA17
    In the xdebug code coverage, it shows the line "return false;" (below "!$r") as not covered by my tests. But, the $sql is basically hard-coded. How do I get coverage on that? Do I overwrite "$table" somehow? Or kill the database server for this part of the test? I guess this is probably telling me I'm not writing my model very well, right? Because I can't test it well. How can I write this better? Since this one line is not covered, the whole method is not covered and the reports are off. I'm fairly new to phpunit. Thanks. public function retrieve_all() { $table = $this->tablename(); $sql = "SELECT t.* FROM `{$table}` as t"; $r = dbq ( $sql, 'read' ); if(!$r) { return false; } $ret = array (); while ( $rs = mysql_fetch_array ( $r, MYSQL_ASSOC ) ) { $ret[] = $rs; } return $ret; }

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  • Help me build a CouchDB mapreduce

    - by mit
    There are CouchDB documents that are list elements: { "type" : "el", "id" : "1", "content" : "first" } { "type" : "el", "id" : "2", "content" : "second" } { "type" : "el", "id" : "3", "content" : "third" } There is one document that defines the list: { "type" : "list", "elements" : ["2","1"] , "id" : "abc123" } As you can see the third element was deleted, it is no longer part of the list. So it must not be part of the result. Now I want a view that returns the content elements including the right order. The result could be: { "content" : ["second", "first"] } In this case the order of the elements is already as it should be. Another possible result: { "content" : [{"content" : "first", "order" : 2},{"content" : "second", "order" : 1}] } I started writing the map function: map = function (doc) { if (doc.type === 'el') { emit(doc.id, {"content" : doc.content}); //emit the id and the content exit; } if (doc.type === 'list') { for ( var i=0, l=doc.elements.length; i<l; ++i ){ emit(doc.elements[i], { "order" : i }); //emit the id and the order } } } This is as far as I can get. Can you correct my mistakes and write a reduce function? Remember that the third document must not be part of the result.

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  • Tired of Exploring

    - by Abhi
    Dear All I am tired of my work. I am exploring all day and at the end of the day i feel that i have not gain anything. Its been 1 year & 3 month working in Wince 6.0 r3 but i feel that i have gained nothing. I feel like that i have wasted these month without doing anything. At fast i worked in GUI application in which i was gaining confidence but then i was shifted from that domain to something for which lot of knowledge is required i.e writing or adjusting BSP. Now at present i have shifted to work on silverlight which is again a new domain for me. My day starts from 10am and ends at 7pm @ office by doing nothing. I am tired completely. Can anyone help me what shall i do in this situation? How shall i start to achieve the target? Where should i stick "deadline" or "learning the target first" as deadline is also important? I am completely depressed.

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  • Checking if a file is a directory or just a file.

    - by Jookia
    I'm writing a program to check if something is a file or is a directory. Is there a better way to do it than this? #include <stdio.h> #include <sys/types.h> #include <dirent.h> #include <errno.h> int isFile(const char* name) { DIR* directory = opendir(name); if(directory != NULL) { closedir(directory); return 0; } if(errno == ENOTDIR) { return 1; } return -1; } int main(void) { const char* file = "./testFile"; const char* directory = "./"; printf("Is %s a file? %s.\n", file, ((isFile(file) == 1) ? "Yes" : "No")); printf("Is %s a directory? %s.\n", directory, ((isFile(directory) == 0) ? "Yes" : "No")); return 0; }

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  • Cross-Application User Authentication

    - by Chris Lieb
    We have a webapp written in .NET that uses NTLM for SSO. We are writing a new webapp in Java that will tightly integrate with the original application. Unfortunately, Java has no support for performing the server portion of NTLM authentication and the only library that I can find requires too much setup to be allowed by IT. To work around this, I came up with a remote authentication scheme to work across applications and would like your opinions on it. It does not need to be extremely secure, but at the same time not easily be broken. User is authenticated into .NET application using NTLM User clicks link that leaves .NET application .NET application generates random number and stores it in the user table along with the user's full username (domain\username) Insecure token is formed as random number:username Insecure token is run through secure cipher (likely AES-256) using pre-shared key stored within the application to produce a secure token The secure token is passed as part of the query string to the Java application The Java application decrypts the secure key using the same pre-shared key stored within its own code to get the insecure token The random number and username are split apart The username is used to retrieve the user's information from the user table and the stored random number is checked against the one pulled from the insecure token If the numbers match, the username is put into the session for the user and they are now authenticated If the numbers do not match, the user is redirected to the .NET application's home page The random number is removed from the database

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  • When using Direct3D, how much math is being done on the CPU?

    - by zirgen
    Context: I'm just starting out. I'm not even touching the Direct3D 11 API, and instead looking at understanding the pipeline, etc. From looking at documentation and information floating around the web, it seems like some calculations are being handled by the application. That, is, instead of simply presenting matrices to multiply to the GPU, the calculations are being done by a math library that operates on the CPU. I don't have any particular resources to point to, although I guess I can point to the XNA Math Library or the samples shipped in the February DX SDK. When you see code like mViewProj = mView * mProj;, that projection is being calculated on the CPU. Or am I wrong? If you were writing a program, where you can have 10 cubes on the screen, where you can move or rotate cubes, as well as viewpoint, what calculations would you do on the CPU? I think I would store the geometry for the a single cube, and then transform matrices representing the actual instances. And then it seems I would use the XNA math library, or another of my choosing, to transform each cube in model space. Then get the coordinates in world space. Then push the information to the GPU. That's quite a bit of calculation on the CPU. Am I wrong? Am I reaching conclusions based on too little information and understanding? What terms should I Google for, if the answer is STFW? Or if I am right, why aren't these calculations being pushed to the GPU as well?

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  • Problem with making a simple JS XmlHttpRequest call

    - by recipriversexclusion
    I have to create a very simple client that makes GET and POST calls to our server and parses the returned XML. I am writing this in JavaScript, problem is I don't know how to program in JS (started to look into this just this morning)! As n initial test, I am trying to ping to the Twitter API, here's the function that gets called when user enters the URL http://api.twitter.com/1/users/lookup.xml and hits the submit button: function doRequest() { var req_url, req_type, body; req_url = document.getElementById('server_url').value; req_type = document.getElementById('request_type').value; alert("Connecting to url: " + req_url + " with HTTP method: " + req_type); req = new XMLHttpRequest(); req.open(req_type, req_url, false, "username", "passwd");// synchronous conn req.onreadystatechange=function() { if (req.readyState == 4) { alert(req.status); } } req.send(null); } When I run this on FF, I get a Access to restricted URI denied" code: "1012 error on Firebug. Stuff I googled suggested that this was a FF-specific problem so I switched to Chrome. Over there, the second alert comes up, but displays 0 as HTTP status code, which I found weird. Can anyone spot what the problem is? People say this stuff is easier to use with JQuery but learning that on top of JS syntax is a bit too much now.

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  • Small openmp programm freezes sometimes (gcc, c, linux)

    - by osgx
    Hello Just write a small omp test, and it does not work correctly all the times: #include <omp.h> int main() { int i,j=0; #pragma omp parallel for(i=0;i<1000;i++) { #pragma omp barrier j+= j^i; } return j; } The usage of j for writing from all threads is incorrect in this example, BUT there must be only nondeterministic value of j I have a freeze. Compiled with gcc-4.3.1 -fopenmp a.c -o gcc -static Run on 4-core x86_Core2 Linux server: $ ./gcc and got freeze (sometimes; like 1 freeze for 4-5 fast runs). Strace: [pid 13118] <... futex resumed> ) = 0 [pid 13118] futex(0x80d3014, FUTEX_WAIT, 2, NULL <unfinished ...> [pid 13120] <... futex resumed> ) = 0 [pid 13119] futex(0x80d3014, FUTEX_WAIT, 2, NULL <unfinished ...> [pid 13120] futex(0x80d3014, FUTEX_WAKE, 1) = 1 [pid 13120] futex(0x80cd798, FUTEX_WAIT, 1, NULL <unfinished ...> [pid 13109] <... futex resumed> ) = 0 [pid 13109] futex(0x80d3014, FUTEX_WAKE, 1) = 1 [pid 13109] futex(0x80d3020, FUTEX_WAIT, 251, NULL <unfinished ...> [pid 13118] <... futex resumed> ) = 0 [pid 13118] futex(0x80d3014, FUTEX_WAKE, 1) = 1 [pid 13119] <... futex resumed> ) = 0 [pid 13118] futex(0x80d3020, FUTEX_WAIT, 251, NULL <unfinished ...> [pid 13119] futex(0x80d3014, FUTEX_WAKE, 1) = 0 [pid 13119] futex(0x80d3020, FUTEX_WAIT, 251, NULL <freeze> Why do I have a freeze (deadlock)?

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  • How to backup using backup API's in c++

    - by user1603185
    I am writing an application that used to backup some specified file, therefore using the backup API calls i.e CreateFile BackupRead and WriteFile API's. getting errors Access violation reading location. I have attached code below. #include <windows.h> int main() { HANDLE hInput, hOutput; //m_filename is a variable holding the file path to read from hInput = CreateFile(L"C:\\Key.txt", GENERIC_READ, 0, NULL, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL); //strLocation contains the path of the file I want to create. hOutput= CreateFile(L"C:\\tmp\\", GENERIC_WRITE, NULL, NULL, CREATE_ALWAYS, NULL, NULL); DWORD dwBytesToRead = 1024 * 1024 * 10; BYTE *buffer; buffer = new BYTE[dwBytesToRead]; BOOL bReadSuccess = false,bWriteSuccess = false; DWORD dwBytesRead,dwBytesWritten; LPVOID lpContext; //Now comes the important bit: do { bReadSuccess = BackupRead(hInput, buffer, sizeof(BYTE) *dwBytesToRead, &dwBytesRead, false, true, &lpContext); bWriteSuccess= WriteFile(hOutput, buffer, sizeof(BYTE) *dwBytesRead, &dwBytesWritten, NULL); }while(dwBytesRead == dwBytesToRead); return 0; } Any one suggest me how to use these API's? Thanks.

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  • C++ AI Design Question

    - by disney
    Hi, I am currently writing a bot for a MMORPG. Though, currently I am stuck at trying to figure out how to nicely implement this. The design problem is related to casting the character spells in the correct order. Here is a simple example to what I need to archieve. It's not related to casting them, but doing it in the correct order. I would know how simply cast them randomly, by checking which skill has not yet been casted, but in right order as being shown in the GUI, not really. note: the skill amount may differ, it's not always 3, maximum 10 though. Charactername < foobar has 3 skills. Skill 1: Name ( random1 ) cooldown ( 1000 ms ) cast duration ( 500 ms ) Skill 2: Name ( random2 ) cooldown ( 1500 ms ) cast duration ( 700 ms ) Skill 3: Name ( random3 ) cooldown ( 2000 ms ) cast duration ( 900 ms ) I don't really know how I could implement this, if anyone has some thoughts, feel free to share. I do know that most of the people don't like the idea of cheating in games, I don't like it either, nor I am actually playing the game, but its an interesting field for me. Thank you.

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  • how can i make sure only a single record is inserted when multiple apache threads are trying to acce

    - by Ed Gl
    I have a web service (xmlrpc service to be exact) that handles among other things writing data into the database. Here's the scenario: I often receive requests to either update or insert a record. What I would do is this: If the record already exists, append to the record, If not, create a new record The issue is that there are certain times I would get a 'burst' of requests, which spawns several apache threads to handle the request. These 'bursts' would come within less than milliseconds of each other. I now have several threads performing #1 and #2. Often two threads would would 'pass' number #1 and actually create two duplicate records (except for the primary key). I'd like to use some locking mechanism to prevent other threads from accessing the table while the other thread finishes its work. I'm just afraid of using it because if something happens I don't want to leave the table locked. Is there a solid way of handling this? I'm open to using locks if I can do it properly. Thanks,

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  • .NET Application with SQL Server CE Database

    - by blu
    I just started using SQL Server CE 3.5 in my WinForms Application (C# in VS 2008 SP1). I've noticed a couple of interesting things I'd like some input on: 1. Copying of sdf file to bin My sdf file is located inside of an Infrastructure project that houses my repository implementations. When the application is first debugged the sdf was copied to debug\bin. This is where all future reads/writes operate. At some point when this is deployed the file will go into a data folder using Click Once, but during development where should I be putting this sdf? Is having it in the bin typical, or are there any other recommendations? 2. Updating sdf It appears that writing to the sdf file does not immediately update the database. I am using Linq-to-SQL and am calling SubmitChanges, but on read the values are not returned. However if I close the application and re-open it the added value is there. Is there an additional flush step I need to take? What is causing this, file locking, buffering, something else? Update 3. Unit Tests I have an MS test project, and the sdf file is not being copied to the correct output directory. I have the settings: Build Action: Content Copy to Output Directory: Copy Always The message is: System.Data.SqlServerCe.SqlCeException: The database file cannot be found. Check the path to the database. I appreciate any guidance on these questions, thanks. If there is a tutorial other than what is on MSDN that you know about that would be great too. Working with CE is proving to be a difficult task and I welcome any help I can find.

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  • Noise with multi-threaded raytracer

    - by herber88
    This is my first multi-threaded implementation, so it's probably a beginners mistake. The threads handle the rendering of every second row of pixels (so all rendering is handled within each thread). The problem persists if the threads render the upper and lower parts of the screen respectively. Both threads read from the same variables, can this cause any problems? From what I've understood only writing can cause concurrency problems... Can calling the same functions cause any concurrency problems? And again, from what I've understood this shouldn't be a problem... The only time both threads write to the same variable is when saving the calculated pixel color. This is stored in an array, but they never write to the same indices in that array. Can this cause a problem? Multi-threaded rendered image (Spam prevention stops me from posting images directly..) Ps. I use the exactly same implementation in both cases, the ONLY difference is a single vs. two threads created for the rendering.

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