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• How to interpret kernel panics?

  - by Owen

  Hi all, I'm new to linux kernel and could barely understand how to debug kernel panics. I have this error below and I don't know where in the C code should I start checking. I was thinking maybe I could echo what functions are being called so I could check where in the code is this null pointer dereferenced. What print function should I use ? How do you interpret the error message below? Unable to handle kernel NULL pointer dereference at virtual address 0000000d pgd = c7bdc000 [0000000d] *pgd=4785f031, *pte=00000000, *ppte=00000000 Internal error: Oops: 17 [#1] PREEMPT Modules linked in: bcm5892_secdom_fw(P) bcm5892_lcd snd_bcm5892 msr bcm5892_sci bcm589x_ohci_p12 bcm5892_skeypad hx_decoder(P) pinnacle hx_memalloc(P) bcm_udc_dwc scsi_mod g_serial sd_mod usb_storage CPU: 0 Tainted: P (2.6.27.39-WR3.0.2ax_standard #1) PC is at __kmalloc+0x70/0xdc LR is at __kmalloc+0x48/0xdc pc : [c0098cc8] lr : [c0098ca0] psr: 20000093 sp : c7a9fd50 ip : c03a4378 fp : c7a9fd7c r10: bf0708b4 r9 : c7a9e000 r8 : 00000040 r7 : bf06d03c r6 : 00000020 r5 : a0000093 r4 : 0000000d r3 : 00000000 r2 : 00000094 r1 : 00000020 r0 : c03a4378 Flags: nzCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment user Control: 00c5387d Table: 47bdc008 DAC: 00000015 Process sh (pid: 1088, stack limit = 0xc7a9e260) Stack: (0xc7a9fd50 to 0xc7aa0000) fd40: c7a6a1d0 00000020 c7a9fd7c c7ba8fc0 fd60: 00000040 c7a6a1d0 00000020 c71598c0 c7a9fd9c c7a9fd80 bf06d03c c0098c64 fd80: c71598c0 00000003 c7a6a1d0 bf06c83c c7a9fdbc c7a9fda0 bf06d098 bf06d008 fda0: c7159880 00000000 c7a6a2d8 c7159898 c7a9fde4 c7a9fdc0 bf06d130 bf06d078 fdc0: c79ca000 c7159880 00000000 00000000 c7afbc00 c7a9e000 c7a9fe0c c7a9fde8 fde0: bf06d4b4 bf06d0f0 00000000 c79fd280 00000000 0f700000 c7a9e000 00000241 fe00: c7a9fe3c c7a9fe10 c01c37b4 bf06d300 00000000 c7afbc00 00000000 00000000 fe20: c79cba84 c7463c78 c79fd280 c7473b00 c7a9fe6c c7a9fe40 c00a184c c01c35e4 fe40: 00000000 c7bb0005 c7a9fe64 c79fd280 c7463c78 00000000 c00a1640 c785e380 fe60: c7a9fe94 c7a9fe70 c009c438 c00a164c c79fd280 c7a9fed8 c7a9fed8 00000003 fe80: 00000242 00000000 c7a9feb4 c7a9fe98 c009c614 c009c2a4 00000000 c7a9fed8 fea0: c7a9fed8 00000000 c7a9ff64 c7a9feb8 c00aa6bc c009c5e8 00000242 000001b6 fec0: 000001b6 00000241 00000022 00000000 00000000 c7a9fee0 c785e380 c7473b00 fee0: d8666b0d 00000006 c7bb0005 00000300 00000000 00000000 00000001 40002000 ff00: c7a9ff70 c79b10a0 c79b10a0 00005402 00000003 c78d69c0 ffffff9c 00000242 ff20: 000001b6 c79fd280 c7a9ff64 c7a9ff38 c785e380 c7473b00 00000000 00000241 ff40: 000001b6 ffffff9c 00000003 c7bb0000 c7a9e000 00000000 c7a9ff94 c7a9ff68 ff60: c009c128 c00aa380 4d18b5f0 08000000 00000000 00071214 0007128c 00071214 ff80: 00000005 c0027ee4 c7a9ffa4 c7a9ff98 c009c274 c009c0d8 00000000 c7a9ffa8 ffa0: c0027d40 c009c25c 00071214 0007128c 0007128c 00000241 000001b6 00000000 ffc0: 00071214 0007128c 00071214 00000005 00073580 00000003 000713e0 400010d0 ffe0: 00000001 bef0c7b8 000269cc 4d214fec 60000010 0007128c 00000000 00000000 Backtrace: [] (__kmalloc+0x0/0xdc) from [] (gs_alloc_req+0x40/0x70 [g_serial]) r8:c71598c0 r7:00000020 r6:c7a6a1d0 r5:00000040 r4:c7ba8fc0 [] (gs_alloc_req+0x0/0x70 [g_serial]) from [] (gs_alloc_requests+0x2c/0x78 [g_serial]) r7:bf06c83c r6:c7a6a1d0 r5:00000003 r4:c71598c0 [] (gs_alloc_requests+0x0/0x78 [g_serial]) from [] (gs_start_io+0x4c/0xac [g_serial]) r7:c7159898 r6:c7a6a2d8 r5:00000000 r4:c7159880 [] (gs_start_io+0x0/0xac [g_serial]) from [] (gs_open+0x1c0/0x224 [g_serial]) r9:c7a9e000 r8:c7afbc00 r7:00000000 r6:00000000 r5:c7159880 r4:c79ca000 [] (gs_open+0x0/0x224 [g_serial]) from [] (tty_open+0x1dc/0x314) [] (tty_open+0x0/0x314) from [] (chrdev_open+0x20c/0x22c) [] (chrdev_open+0x0/0x22c) from [] (__dentry_open+0x1a0/0x2b8) r8:c785e380 r7:c00a1640 r6:00000000 r5:c7463c78 r4:c79fd280 [] (__dentry_open+0x0/0x2b8) from [] (nameidata_to_filp+0x38/0x50) [] (nameidata_to_filp+0x0/0x50) from [] (do_filp_open+0x348/0x6f4) r4:00000000 [] (do_filp_open+0x0/0x6f4) from [] (do_sys_open+0x5c/0x170) [] (do_sys_open+0x0/0x170) from [] (sys_open+0x24/0x28) r8:c0027ee4 r7:00000005 r6:00071214 r5:0007128c r4:00071214 [] (sys_open+0x0/0x28) from [] (ret_fast_syscall+0x0/0x2c) Code: e59c4080 e59c8090 e3540000 159c308c (17943103) ---[ end trace be196e7cee3cb1c9 ]--- note: sh[1088] exited with preempt_count 2 process '-/bin/sh' (pid 1088) exited. Scheduling for restart. Welcome to Wind River Linux

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• Why does the Ternary\Conditional operator seem significantly faster

  - by Jodrell

  Following on from this question, which I have partially answered. I compile this console app in x64 Release Mode, with optimizations on, and run it from the command line without a debugger attached. using System; using System.Diagnostics; class Program { static void Main() { var stopwatch = new Stopwatch(); var ternary = Looper(10, Ternary); var normal = Looper(10, Normal); if (ternary != normal) { throw new Exception(); } stopwatch.Start(); ternary = Looper(10000000, Ternary); stopWatch.Stop(); Console.WriteLine( "Ternary took {0}ms", stopwatch.ElapsedMilliseconds); stopwatch.Start(); normal = Looper(10000000, Normal); stopWatch.Stop(); Console.WriteLine( "Normal took {0}ms", stopwatch.ElapsedMilliseconds); if (ternary != normal) { throw new Exception(); } Console.ReadKey(); } static int Looper(int iterations, Func<bool, int, int> operation) { var result = 0; for (int i = 0; i < iterations; i++) { var condition = result % 11 == 4; var value = ((i * 11) / 3) % 5; result = operation(condition, value); } return result; } static int Ternary(bool condition, in value) { return value + (condition ? 2 : 1); } static int Normal(int iterations) { if (condition) { return = 2 + value; } return = 1 + value; } } I don't get any exceptions and the output to the console is somthing close to, Ternary took 107ms Normal took 230ms When I break down the CIL for the two logical functions I get this, ... Ternary ... { : ldarg.1 // push second arg : ldarg.0 // push first arg : brtrue.s T // if first arg is true jump to T : ldc.i4.1 // push int32(1) : br.s F // jump to F T: ldc.i4.2 // push int32(2) F: add // add either 1 or 2 to second arg : ret // return result } ... Normal ... { : ldarg.0 // push first arg : brfalse.s F // if first arg is false jump to F : ldc.i4.2 // push int32(2) : ldarg.1 // push second arg : add // add second arg to 2 : ret // return result F: ldc.i4.1 // push int32(1) : ldarg.1 // push second arg : add // add second arg to 1 : ret // return result } Whilst the Ternary CIL is a little shorter, it seems to me that the execution path through the CIL for either function takes 3 loads and 1 or 2 jumps and a return. Why does the Ternary function appear to be twice as fast. I underdtand that, in practice, they are both very quick and indeed, quich enough but, I would like to understand the discrepancy.

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• Best approach for using Scanner Objects in Java?

  - by devjeetroy

  Although I'm more of a C++/ASM guy, I have to work with java as a part of my undergrad course at college. Our teacher taught us input using Scanner(System.in), and told us that if multiple functions are were taking user input, it would be advisable that a single Scanner object is passed around so as to reduce chances of the input stream getting screwed up. Now using this approach has gotten me into a situation where I'm trying to use a Scanner.nextLine(), and this statement does not wait for user input. It just moves on to the following statement. I figured there may be some residual cr/lf or other characters in the Scanner that might not have been retrieved are causing the problem. Here is the code. while(lineScanner.hasNext()) { if(isPlaceHolder(temp = lineScanner.next())) { temp = temp.replace("<",""); temp = temp.replace(">", ""); System.out.print("Enter "+aOrA(temp.charAt(0)) +" " +temp + " : "); temp = consoleInput.nextLine(); } outputFileStream.print(temp + " "); } All of the code is inside a function which receives a Scanner object consoleInput. Ok, so what happens when i run it is that when the program enters the if() the first time, It carries out theSystem.out.print, does not wait for user input, and moves on to the second time that it enters the 'if' block. This time, it takes the input and the rest of the program operates normally. What is even more surprising is that when i check the output file created by the program, it is perfect, just as i want to be. Almost as if the first time input using the scanner is correct. I have solved this problem by creating a new system.in Scanner in the function itself, instead of receiving the Scanner object as a parameter. But I am still very curious to know what the hell is happening and why it couldn't be solved using a simple Scanner.reset(). Would it be better to just simply create a Scanner Object for each function? Thanks, Devjeet PS. Although I know how to take input using fileinputstreams and the like, we are not supposed to use it with the homework.

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• What are the steps to convert this function to a model/controller in Zend Framework?

  - by Joel

  Hi guys, I'm learning Zend Framework MVC, and I have a website that is mainly static php pages. However one of the pages is using functions, etc, and I'm trying to figure out what the process is for converting this to an OOP setup. Within the <body> I have this function (and more, but this is the first function): function filterEventDetails($contentText) { $data = array(); foreach($contentText as $row) { if(strstr($row, 'When: ')) { ##cleaning "when" string to get date in the format "May 28, 2009"## $data['duration'] = str_replace('When: ','',$row); list($when, ) = explode(' to ',$data['duration']); $data['when'] = substr($when,4); if(strlen($data['when'])>13) $data['when'] = trim(str_replace(strrchr($data['when'], ' '),'',$data['when'])); $data['duration'] = substr($data['duration'], 0, strlen($data['duration'])-4); //trimming time zone identifier (UTC etc.) } if(strstr($row, 'Where: ')) { $data['where'] = str_replace('Where: ','',$row); //pr($row); //$where = strstr($row, 'Where: '); //pr($where); } if(strstr($row, 'Event Description: ')) { $event_desc = str_replace('Event Description: ','',$row); //$event_desc = strstr($row, 'Event Description: '); ## Filtering event description and extracting venue, ticket urls etc from it. //$event_desc = str_replace('Event Description: ','',$contentText[3]); $event_desc_array = explode('|',$event_desc); array_walk($event_desc_array,'get_desc_second_part'); //pr($event_desc_array); $data['venue_url'] = $event_desc_array[0]; $data['details'] = $event_desc_array[1]; $data['tickets_url'] = $event_desc_array[2]; $data['tickets_button'] = $event_desc_array[3]; $data['facebook_url'] = $event_desc_array[4]; $data['facebook_icon'] = $event_desc_array[5]; } } return $data; } ?> So right now I have this in my example.phtml view page. I understand this needs to be a model and acted on by the controller, but I'm really not sure where to start with this conversion? This is a function tht is taking info from a Google calendar and parsing it for the view. Thanks for any help!

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• Primary language - C++/Qt, C#, Java?

  - by Airjoe

  I'm looking for some input, but let me start with a bit of background (for tl;dr skip to end). I'm an IT major with a concentration in networking. While I'm not a CS major nor do I want to program as a vocation, I do consider myself a programmer and do pretty well with the concepts involved. I've been programming since about 6th grade, started out with a proprietary game creation language that made my transition into C++ at college pretty easy. I like to make programs for myself and friends, and have been paid to program for local businesses. A bit about that- I wrote some programs for a couple local businesses in my senior year in high school. I wrote management systems for local shops (inventory, phone/pos orders, timeclock, customer info, and more stuff I can't remember). It definitely turned out to be over my head, as I had never had any formal programming education. It was a great learning experience, but damn was it crappy code. Oh yeah, by the way, it was all vb6. So, I've used vb6 pretty extensively, I've used c++ in my classes (intro to programming up to algorithms), used Java a little bit in another class (had to write a ping client program, pretty easy) and used Java for some simple Project Euler problems to help learn syntax and such when writing the program for the class. I've also used C# a bit for my own simple personal projects (simple programs, one which would just generate an HTTP request on a list of websites and notify if one responded unexpectedly or not at all, and another which just held a list of things to do and periodically reminded me to do them), things I would've written in vb6 a year or two ago. I've just started using Qt C++ for some undergrad research I'm working on. Now I've had some formal education, I [think I] understand organization in programming a lot better (I didn't even use classes in my vb6 programs where I really should have), how it's important to structure code, split into functions where appropriate, document properly, efficiency both in memory and speed, dynamic and modular programming etc. I was looking for some input on which language to pick up as my "primary". As I'm not a "real programmer", it will be mostly hobby projects, but will include some 'real' projects I'm sure. From my perspective: QtC++ and Java are cross platform, which is cool. Java and C# run in a virtual machine, but I'm not sure if that's a big deal (something extra to distribute, possibly a bit slower? I think Qt would require additional distributables too, right?). I don't really know too much more than this, so I appreciate any help, thanks! TL;DR Am an avocational programmer looking for a language, want quick and straight forward development, liked vb6, will be working with database driven GUI apps- should I go with QtC++, Java, C#, or perhaps something else?

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• Learning... anything really

  - by WebDevHobo

  I'm particularly interested in Windows PowerShell, but here's a somewhat more general complaint: When asking for help on learning something new, be it a small subject on PHP or understanding a class in Java, what usually happens is that people direct me towards the documentation pages. What I'm looking for is somewhat of a course. A deep explanation of why something works the way it does. I know my basic programming, like Java and C#. I've never seen C or C++, though I have seen a bit of assembler. I know what the Stack and Heap are, how boxing and unboxing works, why you have to deep-copy an array instead of copying the pointer and some other things. Windows PowerShell on the other hand, I know nothing about. And I notice that when reading the small document or some code, I usually forget what it does or why it works. What I am looking for is preferably, a nice tutorial that explains the beginnings, the concepts, and goes to more difficult things at a steady pace. The only thing documentation can do is explain what a function does. That's no good to me since I don't know what I want to do yet. I could read about a thousand functions, and forget about most of them, because I don't need to implement them right after it. Randomly wandering through the documentation doesn't do me any good. So conclude, what is a good tutorial on Windows Powershell? One which explains in clear language what is happening, one which builds on previous things learned. I don't think googling this is a good idea. Doing a Google search on this would turn up numerous tutorials. And experience tells me that you have to look long and hard to find the gem you're looking for. That's why I'm asking here. Because this is the place where you can find more experienced people. Many of the PowerShell guys among you will know the good ones already, and by asking you, I avoid wasting time that could be spent learning. So to summarize: I will not google this!

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• L-Soft LISTSERV TCPGUI Interface for PHP Creation

  - by poolnoodl

  I'm trying to use LISTSERV's "API" in PHP. L-Soft calls this TCPGUI, and essentially, you can request data like over Telnet. To do this, I'm using PHP's TCP socket functions. I've seen this done in other languages but can't quite convert it to PHP. I can connect, I can change set ASCII or BINARY mode. But I can never quite craft the header packet the way I need to authenticate, so I'm thinking I'm messing up my conversion. C: http://www.lsoft.com/manuals/16.0/htmlhelp/advanced%20topics/TCPGUI.html#2334328 $origin = '[email protected]'; $pwd = 'password'; $host = "example.com"; $port = 2306; $email = "[email protected]"; $list = "mailinglist"; $command = "Query $list FOR $email"; $fp = stream_socket_client("tcp://$host:$port", $errno, $errstr, 30); $cmd = $command . " PW=" . $pwd; $len = strlen($cmd); $orglen = strlen($origin); $n = $len + $orglen + 1; $headerPacket[0] = "1"; $headerPacket[1] = "B"; $headerPacket[2] = "\r"; $headerPacket[3] = "\n"; $headerPacket[4] = ord($n / 256); $headerPacket[5] = ord($n + 255); $headerPacket[6] = ord($orglen); for ($i = 0; $i < $orglen; $i++) { $headerPacket[$i + 7] = ord($origin[$i]); } for ($i = 0; $i < $len; $i++) { $cmdPacket[$i] = ord($cmd[$i]); } fwrite($fp, implode($headerPacket)); while (!feof($fp)) { echo fgets($fp, 1024); } Any thoughts on where I'm going wrong? I'd much appreciate it if anyone could point me toward some code to do this, days of googling and searching here on SO has only lead me to examples in other languages. Of course, if you know C (or Java or Perl as linked below in my comment to bypass the spam filter), PHP, and socket programming fairly well, you could probably rewrite the whole of the code in an hour, maybe a few minutes. You'd have my eternal thanks for that.

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• Remove never-run call to templated function, get allocation error on run-time

  - by Narfanator

  First off, I'm a bit at a loss as to how to ask this question. So I'm going to try throwing lots of information at the problem. Ok, so, I went to completely redesign my test project for my experimental core library thingy. I use a lot of template shenanigans in the library. When I removed the "user" code, the tests gave me a memory allocation error. After quite a bit of experimenting, I narrowed it down to this bit of code (out of a couple hundred lines): void VOODOO(components::switchBoard &board){ board.addComponent<using_allegro::keyInputs<'w'> >(); } Fundementally, what's weirding me out is that it appears that the act of compiling this function (and the template function it then uses, and the template functions those then use...), makes this bug not appear. This code is not being run. Similar code (the same, but for different key vals) occurs elsewhere, but is within Boost TDD code. I realize I certainly haven't given enough information for you to solve it for me; I tried, but it more-or-less spirals into most of the code base. I think I'm most looking for "here's what the problem could be", "here's where to look", etc. There's something that's happening during compile because of this line, but I don't know enough about that step to begin looking. Sooo, how can a (presumably) compilied, but never actually run, bit of templated code, when removed, cause another part of code to fail? Error: Unhandled exceptionat 0x6fe731ea (msvcr90d.dll) in Switchboard.exe: 0xC0000005: Access violation reading location 0xcdcdcdc1. Callstack: operator delete(void * pUser Data) allocator< class name related to key inputs callbacks ::deallocate vector< same class ::_Insert_n(...) vector< " " ::insert(...) vector<" "::push_back(...) It looks like maybe the vector isn't valid, because _MyFirst and similar data members are showing values of 0xcdcdcdcd in the debugger. But the vector is a member variable...

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• PHP running as a FastCGI application (php-cgi) - how to issue concurrent requests?

  - by Sbm007

  Some background information: I'm writing my own webserver in Java and a couple of days ago I asked on SO how exactly Apache interfaces with PHP, so I can implement PHP support. I learnt that FastCGI is the best approach (since mod_php is not an option). So I have looked at the FastCGI protocol specification and have managed to write a working FastCGI wrapper for my server. I have tested phpinfo() and it works, in fact all PHP functions seem to work just fine (posting data, sessions, date/time, etc etc). My webserver is able to serve requests concurrently (ie user1 can retrieve file1.html at the same time as user2 requesting some_large_binary_file.zip), it does this by spawning a new Java thread for each user request (terminating when completed or user connection with client is cancelled). However, it cannot deal with 2 (or more) FastCGI requests at the same time. What it does is, it queues them up, so when request 1 is completed immediately thereafter it starts processing request 2. I tested this with 2 PHP pages, one contains sleep(10) and the other phpinfo(). How would I go about dealing with multiple requests as I know it can be done (PHP under IIS runs as FastCGI and it can deal with multiple requests just fine). Some more info: I am coding under windows and my batch file used to execute php-cgi.exe contains: set PHP_FCGI_CHILDREN=8 set PHP_FCGI_MAX_REQUESTS=500 php-cgi.exe -b 9000 But it does not spawn 8 children, the service simply terminates after 500 requests. I have done research and from Wikipedia: Processing of multiple requests simultaneously is achieved either by using a single connection with internal multiplexing (ie. multiple requests over a single connection) and/or by using multiple connections Now clearly the multiple connections isn't working for me, as everytime a client requests something that involves FastCGI it creates a new socket to the FastCGI application, but it does not work concurrently (it queues them up instead). I know that internal multiplexing of FastCGI requests under the same connection is accomplished by issuing each unique FastCGI request with a different request ID. (also see the last 3 paragraphs of 'The Communication Protocol' heading in this article). I have not tested this, but how would I go about implementing that? I take it I need some kind of FastCGI Java thread which contains a Map of some sort and a static function which I can use to add requests to. Then in the Thread's run() function it would have a while loop and for every cycle it would check whether the Map contains new requests, if so it would assign them a request ID and write them to the FastCGI stream. And then wait for input etc etc, As you can see this becomes too complicated. Does anyone know the correct way of doing this? Or any thoughts at all? Thanks very much. Note, if required I can supply the code for my FastCGI wrapper.

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• Lift session valid ajax callback from a static javascript

  - by ChrisJamesC

  I am currently implementing a graph visualisation tool using lift on the server side and d3 ( a javascript visualisation framework) for all the visualisation. The problem I have is that in the script I want to get session dependent data from the server. So basically, my objective is to write lift-valid ajax callbacks in a static js script. Here is what I tried so far: What I have tried so far If you feel that the best solution is one that I already tried feel free to post a detailed answer telling me how to use it exactly and how it completely solves my problem. REST interface Usually what one would do to get data from a javascript function in lift is to create a REST interface. However this interface will not be linked to any session. This is the solution I got from my previous question: Get json data in d3 from lift snippet Give function as argument of script Another solution would be to give the ajaxcallback as an argument of the main script called to generate my graph. However I expect to have a lot of callbacks and I don't want to have to mess with the arguments of my script. Write the ajax callback in another script using lift and call it from the main script This solution, which is similar to a hidden text input is probably the more likely to work. However it is not elegant and it would mean that I would have to load a lot of scripts on load, which is not really conveniant. Write the whole script in lift and then serve it to the client This solution can be elegant, however my script is very long and I would really prefer that it remainss static. What I want On client side While reviewing the source code of my webpage I found that the callback for an ajaxSelect is: <select onchange="liftAjax.lift_ajaxHandler('F966066257023LYKF4=' + encodeURIComponent(this.value), null, null, null)" name="F96606625703QXTSWU" id="node_delete" class="input"> Moreover, there is a variable containing the state of the page in the end of the webpage: var lift_page = "F96606625700QRXLDO"; So, I am wondering if it is possible to simulate that my ajaxcall is valid using this liftAjax.lift_ajaxHandler function. However I don't know the exact synthax to use. On server side Since I "forged" a request on client side, I would now like to get the request on client side and to dispatch it to the correct function. This is where the LiftRules.dispatch object seems the best solution: when it is called, all the session management has been made (the request is authentified and linked to a session), however I don't know how to write the correct piece of code in the append function. Remark In lift all names of variables are changed to a random string in order to increase the security, I would like to have the same behavior in my application even if that will probably mean that I will have to "give" the javascript these values. However an array of 15 string values is still a better tradeoff than 15 functions as argument of a javascript function.

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• Why do we have reinterpret_cast in C++ when two chained static_cast can do it's job?

  - by Nawaz

  Say I want to cast A* to char* and vice-versa, we have two choices (I mean, many of us think we've two choices, because both seems to work! Hence the confusion!): struct A { int age; char name[128]; }; A a; char *buffer = static_cast<char*>(static_cast<void*>(&a)); //choice 1 char *buffer = reinterpret_cast<char*>(&a); //choice 2 Both work fine. //convert back A *pA = static_cast<A*>(static_cast<void*>(buffer)); //choice 1 A *pA = reinterpret_cast<A*>(buffer); //choice 2 Even this works fine! So why do we have reinterpret_cast in C++ when two chained static_cast can do it's job? Some of you might think this topic is a duplicate of the previous topics such as listed at the bottom of this post, but it's not. Those topics discuss only theoretically, but none of them gives even a single example demonstrating why reintepret_cast is really needed, and two static_cast would surely fail. I agree, one static_cast would fail. But how about two? If the syntax of two chained static_cast looks cumbersome, then we can write a function template to make it more programmer-friendly: template<class To, class From> To any_cast(From v) { return static_cast<To>(static_cast<void*>(v)); } And then we can use this, as: char *buffer = any_cast<char*>(&a); //choice 1 char *buffer = reinterpret_cast<char*>(&a); //choice 2 //convert back A *pA = any_cast<A*>(buffer); //choice 1 A *pA = reinterpret_cast<A*>(buffer); //choice 2 Also, see this situation where any_cast can be useful: Proper casting for fstream read and write member functions. So my question basically is, Why do we have reinterpret_cast in C++? Please show me even a single example where two chained static_cast would surely fail to do the same job? Which cast to use; static_cast or reinterpret_cast? Cast from Void* to TYPE* : static_cast or reinterpret_cast

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• C++ string sort like a human being?

  - by Walter Nissen

  I would like to sort alphanumeric strings the way a human being would sort them. I.e., "A2" comes before "A10", and "a" certainly comes before "Z"! Is there any way to do with without writing a mini-parser? Ideally it would also put "A1B1" before "A1B10". I see the question "Natural (human alpha-numeric) sort in Microsoft SQL 2005" with a possible answer, but it uses various library functions, as does "Sorting Strings for Humans with IComparer". Below is a test case that currently fails: #include <set> #include <iterator> #include <iostream> #include <vector> #include <cassert> template <typename T> struct LexicographicSort { inline bool operator() (const T& lhs, const T& rhs) const{ std::ostringstream s1,s2; s1 << toLower(lhs); s2 << toLower(rhs); bool less = s1.str() < s2.str(); std::cout<<s1.str()<<" "<<s2.str()<<" "<<less<<"\n"; return less; } inline std::string toLower(const std::string& str) const { std::string newString(""); for (std::string::const_iterator charIt = str.begin(); charIt!=str.end();++charIt) { newString.push_back(std::tolower(*charIt)); } return newString; } }; int main(void) { const std::string reference[5] = {"ab","B","c1","c2","c10"}; std::vector<std::string> referenceStrings(&(reference[0]), &(reference[5])); //Insert in reverse order so we know they get sorted std::set<std::string,LexicographicSort<std::string> > strings(referenceStrings.rbegin(), referenceStrings.rend()); std::cout<<"Items:\n"; std::copy(strings.begin(), strings.end(), std::ostream_iterator<std::string>(std::cout, "\n")); std::vector<std::string> sortedStrings(strings.begin(), strings.end()); assert(sortedStrings == referenceStrings); }

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• C# xml Class to substitute ini files

  - by Eduardo

  Hi guys, I am learning Windows Forms in C#.NET 2008 and i want to build a class to work with SIMPLE xml files (config file like INI files), but i just need a simple class (open, getvalue, setvalue, creategroup, save and close functions), to substitute of ini files. I already did something and it is working but I am having trouble when I need to create different groups, something like this: <?xml version="1.0" encoding="utf-8"?> <CONFIG> <General> <Field1>192.168.0.2</Field1> </General> <Data> <Field1>Joseph</Field1> <Field2>Locked</Field2> </Data> </CONFIG> how can i specify that i want to read the field1 of [data] group? note that i have same field name in both groups (Field1)! I am using System.Linq, something like this: To open document: XmlDocument xmlDoc = new XmlDocument(); xmlDoc.Load(FilePath); To save document: xmlDoc.Save(FilePath); To get value: public string getValue(string Field) { string result = ""; try { XmlNodeList xmlComum = xmlDoc.GetElementsByTagName(Field); if (xmlComum.Item(0) == null) result = ""; else result = xmlComum.Item(0).InnerText; } catch (Exception ex) { return ""; } return result; } To set value: public void setValue(string Group, string Field, string FieldValue) { try { XmlNodeList xmlComum = xmlDoc.GetElementsByTagName(Field); if (xmlComum.Item(0) == null) { xmlComum = xmlDoc.GetElementsByTagName(Group); if (xmlComum.Item(0) == null) { // create group createGroup(Group); xmlComum = xmlDoc.GetElementsByTagName(Group); } XmlElement xmlE = xmlDoc.CreateElement(Field); XmlText xmlT = xmlDoc.CreateTextNode(FieldValue); xmlE.AppendChild(xmlT); xmlComum.Item(0).AppendChild(xmlE); } else { // item already exists, just change its value xmlComum.Item(0).InnerText = Value; } xmlDoc.Save(FilePath); } catch (Exception ex) { } } The CreateGroup code: public void createGroup(string Group) { try { XmlElement xmlComum = xmlDoc.CreateElement(Group); xmlDoc.DocumentElement.AppendChild(xmlComum); xmlDoc.Save(FilePath); } catch (Exception ex) { } } Thank You!

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• is it possible that a greasemonkey script can work on one computer but not on another?

  - by plastic cloud

  i'm writing an greasemonkey script for somebody else. he is a moderator and i am not. and the script will help him do some moderating things. now the script works for me. as far as it can work for me.(as i am not a mod) but even those things that work for me are not working for him.. i checked his version of greasemonkey plugin and firefox and he is up to date. only thing that's really different is that i'm on a mac and he is pc, but i wouldn't think that would be any problem. this is one of the functions that is not working for him. he does gets the first and third GM_log message. but not the second one ("got some(1) .."). kmmh.trackNames = function(){ GM_log("starting to get names from the first "+kmmh.topAmount+" page(s) from leaderboard."); kmmh.leaderboardlist = []; for (var p=1; p<=(kmmh.topAmount); p++){ var page = "http://www.somegamesite.com/leaderboard?page="+ p; var boardHTML = ""; dojo.xhrGet({ url: page, sync: true, load: function(response){ boardHTML = response; GM_log("got some (1) => "+boardHTML.length); }, handleAs: "text" }); GM_log("got some (2) => "+boardHTML.length); //create dummy div and place leaderboard html in there var dummy = dojo.create('div', { innerHTML: boardHTML }); //search through it var searchN = dojo.query('.notcurrent', dummy).forEach(function(node,index){ if(index >= 10){ kmmh.leaderboardlist.push(node.textContent); // add names to array } }); } GM_log("all names from "+ kmmh.topAmount +" page(s) of leaderboard ==> "+ kmmh.leaderboardlist); does anyone have any idea what could be causing this ?? EDIT: i know i had to write according to what he would see on his mod screen. so i asked him to copy paste source of pages and so on. and besides that, this part of the script is not depending on being a mod or not. i got everything else working for him. just this function still doesn't on neither of his pc's.

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• python object to native c++ pointer

  - by Lodle

  Im toying around with the idea to use python as an embedded scripting language for a project im working on and have got most things working. However i cant seem to be able to convert a python extended object back into a native c++ pointer. So this is my class: class CGEGameModeBase { public: virtual void FunctionCall()=0; virtual const char* StringReturn()=0; }; class CGEPYGameMode : public CGEGameModeBase, public boost::python::wrapper<CGEPYGameMode> { public: virtual void FunctionCall() { if (override f = this->get_override("FunctionCall")) f(); } virtual const char* StringReturn() { if (override f = this->get_override("StringReturn")) return f(); return "FAILED TO CALL"; } }; Boost wrapping: BOOST_PYTHON_MODULE(GEGameMode) { class_<CGEGameModeBase, boost::noncopyable>("CGEGameModeBase", no_init); class_<CGEPYGameMode, bases<CGEGameModeBase> >("CGEPYGameMode", no_init) .def("FunctionCall", &CGEPYGameMode::FunctionCall) .def("StringReturn", &CGEPYGameMode::StringReturn); } and the python code: import GEGameMode def Ident(): return "Alpha" def NewGamePlay(): return "NewAlpha" def NewAlpha(): import GEGameMode import GEUtil class Alpha(GEGameMode.CGEPYGameMode): def __init__(self): print "Made new Alpha!" def FunctionCall(self): GEUtil.Msg("This is function test Alpha!") def StringReturn(self): return "This is return test Alpha!" return Alpha() Now i can call the first to functions fine by doing this: const char* ident = extract< const char* >( GetLocalDict()["Ident"]() ); const char* newgameplay = extract< const char* >( GetLocalDict()["NewGamePlay"]() ); printf("Loading Script: %s\n", ident); CGEPYGameMode* m_pGameMode = extract< CGEPYGameMode* >( GetLocalDict()[newgameplay]() ); However when i try and convert the Alpha class back to its base class (last line above) i get an boost error: TypeError: No registered converter was able to extract a C++ pointer to type class CGEPYGameMode from this Python object of type Alpha I have done alot of searching on the net but cant work out how to convert the Alpha object into its base class pointer. I could leave it as an object but rather have it as a pointer so some non python aware code can use it. Any ideas?

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• Passing variables, creating instances, self, The mechanics and usage of classes: need explenation

  - by Baf

  I've been sitting over this the whole day and Im a little tired already so please excuse me being brief. Im new to python. I just rewrrote a working program, into a bunch of functions in a class and everzthings messed up. I dont know if its me but Im very surprised i couldn t find a beginners tutorial on how to handle classes on the web so I have a few questions. First of all, in the init section of the class i have declared a bunch of variables with self.variable=something. Is it correct that i should be able to access/modify these variables in every function of the class by using self.variable in that function? In other words by declaring self.variable i have made these variables, global variables in the scope of the class right? If not how do i handle self. ? Secondly how do i correctly pass arguments to the class? some example code would be cool. thirdly how do i call a function of the class outside of the class scope? some example code would be cool. fouthly how do I create an Instance of the class INITIALCLASS in another class OTHERCLASS, passing variables from OTHERCLASS to INITIALCLASS? some example code would be cool. I Want to call a function from OTHERCLASS with arguments from INITIALCLASS. What Ive done so far is. class OTHERCLASS(): def __init__(self,variable1,variable2,variable3): self.variable1=variable1 self.variable2=variable2 self.variable3=variable3 def someotherfunction(self): something=somecode(using self.variable3) self.variable2.append(something) print self.variable2 def somemorefunctions(self): self.variable2.append(variable1) class INITIALCLASS(): def __init__(self): self.variable1=value1 self.variable2=[] self.variable3='' self.DoIt=OTHERCLASS(variable1,variable2,variable3) def somefunction(self): variable3=Somecode #tried this self.DoIt.someotherfunctions() #and this DoIt.someotherfunctions() I clearly havent understood how to pass variables to classes or how to handle self, when to use it and when not, I probably also havent understood how to properly create an isntance of a class. In general i havent udnerstood the mechanics of classes So please help me and explain it to me like i have no Idea( which i dont it seems). Or point me to a thorough video, or readable tutorial. All i find on the web is super simple examples, that didnt help me much. Or just very short definitions of classes and class methods instances etc. I can send you my original code if you guys want, but its quite long. Thanks for the Help Much appreciated!

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• Loosely coupled implicit conversion

  - by ltjax

  Implicit conversion can be really useful when types are semantically equivalent. For example, imagine two libraries that implement a type identically, but in different namespaces. Or just a type that is mostly identical, except for some semantic-sugar here and there. Now you cannot pass one type into a function (in one of those libraries) that was designed to use the other, unless that function is a template. If it's not, you have to somehow convert one type into the other. This should be trivial (or otherwise the types are not so identical after-all!) but calling the conversion explicitly bloats your code with mostly meaningless function-calls. While such conversion functions might actually copy some values around, they essentially do nothing from a high-level "programmers" point-of-view. Implicit conversion constructors and operators could obviously help, but they introduce coupling, so that one of those types has to know about the other. Usually, at least when dealing with libraries, that is not the case, because the presence of one of those types makes the other one redundant. Also, you cannot always change libraries. Now I see two options on how to make implicit conversion work in user-code: The first would be to provide a proxy-type, that implements conversion-operators and conversion-constructors (and assignments) for all the involved types, and always use that. The second requires a minimal change to the libraries, but allows great flexibility: Add a conversion-constructor for each involved type that can be externally optionally enabled. For example, for a type A add a constructor: template <class T> A( const T& src, typename boost::enable_if<conversion_enabled<T,A>>::type* ignore=0 ) { *this = convert(src); } and a template template <class X, class Y> struct conversion_enabled : public boost::mpl::false_ {}; that disables the implicit conversion by default. Then to enable conversion between two types, specialize the template: template <> struct conversion_enabled<OtherA, A> : public boost::mpl::true_ {}; and implement a convert function that can be found through ADL. I would personally prefer to use the second variant, unless there are strong arguments against it. Now to the actual question(s): What's the preferred way to associate types for implicit conversion? Are my suggestions good ideas? Are there any downsides to either approach? Is allowing conversions like that dangerous? Should library implementers in-general supply the second method when it's likely that their type will be replicated in software they are most likely beeing used with (I'm thinking of 3d-rendering middle-ware here, where most of those packages implement a 3D vector).

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• Dynamically loaded jQuery with GreaseMonkey inconsistent on pages (refreshing seems to fix it)... do

  - by uprightnetizen

  Hi, I want a custom page analysis footer on every site I visit... so I've used a method to attach JQuery to unsafeWindow. I then create a floating footer on the page. I want to be able to call commands in a menu, do some processing, then put the results in the footer. Unfortunately it sometimes works, sometimes it doesn't. At least two alerts should happen in the printOutput function. Sometimes it only fires one, then it (crashes?) without error? On other pages, both alerts fire and it finds the element, but it doesn't add the extra text. (e.g. www.linode.com) Refreshing the page, then running the printOutput command again seems to always work. Does anyone know what's going on??? The userscript can be installed at: http://www.captionwizard.com/test/page_analysis.user.js // ==UserScript== // @name page_analysis // @namespace markspace // @description Page Analysis // @include http://*/* // ==/UserScript== (function() { // Add jQuery var GM_JQ = document.createElement('script'); GM_JQ.src = 'http://code.jquery.com/jquery-1.4.2.min.js'; GM_JQ.type = 'text/javascript'; document.getElementsByTagName('head')[0].appendChild(GM_JQ); var jqueryActive = false; //Check if jQuery's loaded function GM_wait() { if(typeof unsafeWindow.jQuery == 'undefined') { window.setTimeout(GM_wait,100); } else { $ = unsafeWindow.jQuery; letsJQuery(); } } GM_wait(); function letsJQuery() { jqueryActive = true; setupOutputFooter(); } /******************************* Analysis FOOTER Functions ******************************/ function printOutput(someText) { alert('printing output'); if($('div.analysis_footer').length) { alert('is here - appending'); $('div.analysis_footer').append('<br>' + someText); } else { alert('not here - trying again'); setupOutputFooter(); $('div.analysis_footer').append('<br>' + someText); } } GM_registerMenuCommand("Test Output", testOutput, "k", "control", "k" ); function testOutput() { printOutput('testing this'); } function setupOutputFooter() { $('<div class="analysis_footer">Page Analysis Footer:</div>').appendTo('body'); $('div.analysis_footer').css('position','fixed').css('bottom', '0px').css('background-color','#F8F8F8'); $('div.analysis_footer').css('width','100%').css('color','#3B3B3B').css('font-size', '0.8em'); $('div.analysis_footer').css('font-family', '"Myriad",Verdana,Arial,Helvetica,sans-serif').css('padding', '5px'); $('div.analysis_footer').css('border-top', '1px solid black').css('text-align', 'left'); } }());

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• [NHibernate and ASP.NET MVC] How can I implement a robust session-per-request pattern in my project,

  - by Guillaume Gervais

  I'm currently building an ASP.NET MVC project, with NHibernate as its persistance layer. For now, some functionnalities have been implemented, but only use local NHibernate sessions: each method that accessed the database (read or write) needs to instanciate its own NHibernate session, with the "using()" directive. The problem is that I want to leverage NHibernate's Lazy-Loading capabilities to improve the performance of my project. This implies an open NHibernate session per request until the view is rendered. Furthermore, simultaneous request must be supported (multiple Sessions at the same time). How can I achieve that as cleanly as possible? I searched the Web a little bit and learned about the session-per-request pattern. Most of the implementations I saw used some sort of Http* (HttpContext, etc.) object to store the session. Also, using the Application_BeginRequest/Application_EndRequest functions is complicated, since they get fired for each HTTP request (aspx files, css files, js files, etc.), when I only want to instanciate a session once per request. The concern that I have is that I don't want my views or controllers to have access to NHibernate sessions (or, more generally, NHibernate namespaces and code). That means that I do not want to handle sessions at the controller level nor the view one. I have a few options in mind. Which one seems the best ? Use interceptors (like in GRAILS) that get triggered before and after the controller action. These would open and close sessions/transactions. Is it possible in the ASP.NET MVC world? Use the CurrentSessionContext Singleton provided by NHibernate in a Web context. Using this page as an example, I think this is quite promising, but that still requires filters at the controller level. Use the HttpContext.Current.Items to store the request session. This, coupled with a few lines of code in Global.asax.cs, can easily provide me with a session on the request level. However, it means that dependencies will be injected between NHibernate and my views (HttpContext). Thank you very much!

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• C++ HW - defining classes - objects that have objects of other class problem in header file (out of

  - by kitfuntastik

  This is my first time with much of this code. With this instancepool.h file below I get errors saying I can't use vector (line 14) or have instance& as a return type (line 20). It seems it can't use the instance objects despite the fact that I have included them. #ifndef _INSTANCEPOOL_H #define _INSTANCEPOOL_H #include "instance.h" #include <iostream> #include <string> #include <vector> #include <stdlib.h> using namespace std; class InstancePool { private: unsigned instances;//total number of instance objects vector<instance> ipp;//the collection of instance objects, held in a vector public: InstancePool();//Default constructor. Creates an InstancePool object that contains no Instance objects InstancePool(const InstancePool& original);//Copy constructor. After copying, changes to original should not affect the copy that was created. ~InstancePool();//Destructor unsigned getNumberOfInstances() const;//Returns the number of Instance objects the the InstancePool contains. const instance& operator[](unsigned index) const; InstancePool& operator=(const InstancePool& right);//Overloading the assignment operator for InstancePool. friend istream& operator>>(istream& in, InstancePool& ip);//Overloading of the >> operator. friend ostream& operator<<(ostream& out, const InstancePool& ip);//Overloading of the << operator. }; #endif Here is the instance.h : #ifndef _INSTANCE_H #define _INSTANCE_H ///////////////////////////////#include "instancepool.h" #include <iostream> #include <string> #include <stdlib.h> using namespace std; class Instance { private: string filenamee; bool categoryy; unsigned featuress; unsigned* featureIDD; unsigned* frequencyy; string* featuree; public: Instance (unsigned features = 0);//default constructor unsigned getNumberOfFeatures() const; //Returns the number of the keywords that the calling Instance object can store. Instance(const Instance& original);//Copy constructor. After copying, changes to the original should not affect the copy that was created. ~Instance() { delete []featureIDD; delete []frequencyy; delete []featuree;}//Destructor. void setCategory(bool category){categoryy = category;}//Sets the category of the message. Spam messages are represented with true and and legit messages with false.//easy bool getCategory() const;//Returns the category of the message. void setFileName(const string& filename){filenamee = filename;}//Stores the name of the file (i.e. “spam/spamsga1.txt”, like in 1st assignment) in which the message was initially stored.//const string& trick? string getFileName() const;//Returns the name of the file in which the message was initially stored. void setFeature(unsigned i, const string& feature, unsigned featureID,unsigned frequency) {//i for array positions featuree[i] = feature; featureIDD[i] = featureID; frequencyy[i] = frequency; } string getFeature(unsigned i) const;//Returns the keyword which is located in the ith position.//const string unsigned getFeatureID(unsigned i) const;//Returns the code of the keyword which is located in the ith position. unsigned getFrequency(unsigned i) const;//Returns the frequency Instance& operator=(const Instance& right);//Overloading of the assignment operator for Instance. friend ostream& operator<<(ostream& out, const Instance& inst);//Overloading of the << operator for Instance. friend istream& operator>>(istream& in, Instance& inst);//Overloading of the >> operator for Instance. }; #endif Also, if it is helpful here is instance.cpp: // Here we implement the functions of the class apart from the inline ones #include "instance.h" #include <iostream> #include <string> #include <stdlib.h> using namespace std; Instance::Instance(unsigned features) { //Constructor that can be used as the default constructor. featuress = features; if (features == 0) return; featuree = new string[featuress]; // Dynamic memory allocation. featureIDD = new unsigned[featuress]; frequencyy = new unsigned[featuress]; return; } unsigned Instance::getNumberOfFeatures() const {//Returns the number of the keywords that the calling Instance object can store. return featuress;} Instance::Instance(const Instance& original) {//Copy constructor. filenamee = original.filenamee; categoryy = original.categoryy; featuress = original.featuress; featuree = new string[featuress]; for(unsigned i = 0; i < featuress; i++) { featuree[i] = original.featuree[i]; } featureIDD = new unsigned[featuress]; for(unsigned i = 0; i < featuress; i++) { featureIDD[i] = original.featureIDD[i]; } frequencyy = new unsigned[featuress]; for(unsigned i = 0; i < featuress; i++) { frequencyy[i] = original.frequencyy[i];} } bool Instance::getCategory() const { //Returns the category of the message. return categoryy;} string Instance::getFileName() const { //Returns the name of the file in which the message was initially stored. return filenamee;} string Instance::getFeature(unsigned i) const { //Returns the keyword which is located in the ith position.//const string return featuree[i];} unsigned Instance::getFeatureID(unsigned i) const { //Returns the code of the keyword which is located in the ith position. return featureIDD[i];} unsigned Instance::getFrequency(unsigned i) const { //Returns the frequency return frequencyy[i];} Instance& Instance::operator=(const Instance& right) { //Overloading of the assignment operator for Instance. if(this == &right) return *this; delete []featureIDD; delete []frequencyy; delete []featuree; filenamee = right.filenamee; categoryy = right.categoryy; featuress = right.featuress; featureIDD = new unsigned[featuress]; frequencyy = new unsigned[featuress]; featuree = new string[featuress]; for(unsigned i = 0; i < featuress; i++) { featureIDD[i] = right.featureIDD[i]; } for(unsigned i = 0; i < featuress; i++) { frequencyy[i] = right.frequencyy[i]; } for(unsigned i = 0; i < featuress; i++) { featuree[i] = right.featuree[i]; } return *this; } ostream& operator<<(ostream& out, const Instance& inst) {//Overloading of the << operator for Instance. out << endl << "<message file=" << '"' << inst.filenamee << '"' << " category="; if (inst.categoryy == 0) out << '"' << "legit" << '"'; else out << '"' << "spam" << '"'; out << " features=" << '"' << inst.featuress << '"' << ">" <<endl; for (int i = 0; i < inst.featuress; i++) { out << "<feature id=" << '"' << inst.featureIDD[i] << '"' << " freq=" << '"' << inst.frequencyy[i] << '"' << "> " << inst.featuree[i] << " </feature>"<< endl; } out << "</message>" << endl; return out; } istream& operator>>(istream& in, Instance& inst) { //Overloading of the >> operator for Instance. string word; string numbers = ""; string filenamee2 = ""; bool categoryy2 = 0; unsigned featuress2; string featuree2; unsigned featureIDD2; unsigned frequencyy2; unsigned i; unsigned y; while(in >> word) { if (word == "<message") {//if at beginning of message in >> word;//grab filename word for (y=6; word[y]!='"'; y++) {//pull out filename from between quotes filenamee2 += word[y];} in >> word;//grab category word if (word[10] == 's') categoryy2 = 1; in >> word;//grab features word for (y=10; word[y]!='"'; y++) { numbers += word[y];} featuress2 = atoi(numbers.c_str());//convert string of numbers to integer Instance tempp2(featuress2);//make a temporary Instance object to hold values read in tempp2.setFileName(filenamee2);//set temp object to filename read in tempp2.setCategory(categoryy2); for (i=0; i<featuress2; i++) {//loop reading in feature reports for message in >> word >> word >> word;//skip two words numbers = "";//reset numbers string for (int y=4; word[y]!='"'; y++) {//grab feature ID numbers += word[y];} featureIDD2 = atoi(numbers.c_str()); in >> word;// numbers = ""; for (int y=6; word[y]!='"'; y++) {//grab frequency numbers += word[y];} frequencyy2 = atoi(numbers.c_str()); in >> word;//grab actual feature string featuree2 = word; tempp2.setFeature(i, featuree2, featureIDD2, frequencyy2); }//all done reading in and setting features in >> word;//read in last part of message : </message> inst = tempp2;//set inst (reference) to tempp2 (tempp2 will be destroyed at end of function call) return in; } } } and instancepool.cpp: // Here we implement the functions of the class apart from the inline ones #include "instancepool.h" #include "instance.h" #include <iostream> #include <string> #include <vector> #include <stdlib.h> using namespace std; InstancePool::InstancePool()//Default constructor. Creates an InstancePool object that contains no Instance objects { instances = 0; ipp.clear(); } InstancePool::~InstancePool() { ipp.clear();} InstancePool::InstancePool(const InstancePool& original) {//Copy constructor. instances = original.instances; for (int i = 0; i<instances; i++) { ipp.push_back(original.ipp[i]); } } unsigned InstancePool::getNumberOfInstances() const {//Returns the number of Instance objects the the InstancePool contains. return instances;} const Instance& InstancePool::operator[](unsigned index) const {//Overloading of the [] operator for InstancePool. return ipp[index];} InstancePool& InstancePool::operator=(const InstancePool& right) {//Overloading the assignment operator for InstancePool. if(this == &right) return *this; ipp.clear(); instances = right.instances; for(unsigned i = 0; i < instances; i++) { ipp.push_back(right.ipp[i]); } return *this; } istream& operator>>(istream& in, InstancePool& ip) {//Overloading of the >> operator. ip.ipp.clear(); string word; string numbers; int total;//int to hold total number of messages in collection while(in >> word) { if (word == "<messagecollection"){ in >> word;//reads in total number of all messages for (int y=10; word[y]!='"'; y++){ numbers = ""; numbers += word[y]; } total = atoi(numbers.c_str()); for (int x = 0; x<total; x++) {//do loop for each message in collection in >> ip.ipp[x];//use instance friend function and [] operator to fill in values and create Instance objects and read them intot he vector } } } } ostream& operator<<(ostream& out, const InstancePool& ip) {//Overloading of the << operator. out << "<messagecollection messages=" << '"' << '>' << ip.instances << '"'<< endl << endl; for (int z=0; z<ip.instances; z++) { out << ip[z];} out << endl<<"</messagecollection>\n"; } This code is currently not writing to files correctly either at least, I'm sure it has many problems. I hope my posting of so much is not too much, and any help would be very much appreciated. Thanks!

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• codeIgniter: pass parameter to a select query from previous query

  - by krike

  I'm creating a little management tool for the browser game travian. So I select all the villages from the database and I want to display some content that's unique to each of the villages. But in order to query for those unique details I need to pass the id of the village. How should I do this? this is my code (controller): function members_area() { global $site_title; $this->load->model('membership_model'); if($this->membership_model->get_villages()) { $data['rows'] = $this->membership_model->get_villages(); $id = 1;//this should be dynamic, but how? if($this->membership_model->get_tasks($id)): $data['tasks'] = $this->membership_model->get_tasks($id); endif; } $data['title'] = $site_title." | Your account"; $data['main_content'] = 'account'; $this->load->view('template', $data); } and this is the 2 functions I'm using in the model: function get_villages() { $q = $this->db->get('villages'); if($q->num_rows() > 0) { foreach ($q->result() as $row) { $data[] = $row; } return $data; } } function get_tasks($id) { $this->db->select('name'); $this->db->from('tasks'); $this->db->where('villageid', $id); $q = $this->db->get(); if($q->num_rows() > 0) { foreach ($q->result() as $task) { $data[] = $task; } return $data; } } and of course the view: <?php foreach($rows as $r) : ?> <div class="village"> <h3><?php echo $r->name; ?></h3> <ul> <?php foreach($tasks as $task): ?> <li><?php echo $task->name; ?></li> <?php endforeach; ?> </ul> <?php echo anchor('site/add_village/'.$r->id.'', '+ add new task'); ?> </div> <?php endforeach; ?> ps: please do not remove the comment in the first block of code!

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• Specializing a template on a lambda in C++0x

  - by Tony A.

  I've written a traits class that lets me extract information about the arguments and type of a function or function object in C++0x (tested with gcc 4.5.0). The general case handles function objects: template <typename F> struct function_traits { template <typename R, typename... A> struct _internal { }; template <typename R, typename... A> struct _internal<R (F::*)(A...)> { // ... }; typedef typename _internal<decltype(&F::operator())>::<<nested types go here>>; }; Then I have a specialization for plain functions at global scope: template <typename R, typename... A> struct function_traits<R (*)(A...)> { // ... }; This works fine, I can pass a function into the template or a function object and it works properly: template <typename F> void foo(F f) { typename function_traits<F>::whatever ...; } int f(int x) { ... } foo(f); What if, instead of passing a function or function object into foo, I want to pass a lambda expression? foo([](int x) { ... }); The problem here is that neither specialization of function_traits<> applies. The C++0x draft says that the type of the expression is a "unique, unnamed, non-union class type". Demangling the result of calling typeid(...).name() on the expression gives me what appears to be gcc's internal naming convention for the lambda, main::{lambda(int)#1}, not something that syntactically represents a C++ typename. In short, is there anything I can put into the template here: template <typename R, typename... A> struct function_traits<????> { ... } that will allow this traits class to accept a lambda expression?

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• How can I append and execute a script inside an iframe in a cross browser way (specifically IE!)?

  - by agmin

  Background: I need to load ad scripts after the DOM has loaded. Because many of the scripts use document.write() and other potentially bad functions to run after the DOM has loaded, I want to load the scripts inside an iframe. So when the ad needs to be shown, an event is triggered which does the following: var iframe = document.createElement('iframe'); iframe.setAttribute('id', 'iframeId'); iframe.setAttribute('src', 'about:blank'); var adContainer = document.getElementById('AdContainer'); adContainer.appendChild(iframe); var val = '<html><head></head><body>'; val += '<scr' + 'ipt type="text/javascript" src="' + url + '"></scr' + 'ipt>'; val += '</body></html>'; If I don't assign the html and body tags to val, the script automatically gets appended to the head of the iframe and fails to execute in FF. In IE, the script doesn't execute with or without the head/body/html tags. var doc = iframe.contentWindow || iframe.contentDocument; if (doc.document){ doc = doc.document } doc.open(); doc.write(val); doc.close(); I found this last bit of code here: http://stackoverflow.com/questions/1591135/why-does-appending-a-script-to-a-dynamically-created-iframe-seem-to-run-the-s. I do NOT want to load jquery in the iframe though, I just want to append a script and have it execute. My current solution seems to work great in FF and Webkit. However, IE doesn't execute the script. The script is written to the page, but doesn't start running. Is there a better way to append the script to the iframe so it will run cross browser? Or is it possible to tell IE to run the script? I know that I could load an external document with the ad script via the iframe, but I don't want to make the extra call to my server if I can do this dynamically. Also, I've tried using appendChild() on the iframe's body to insert the script, but since the script element is created outside the iframe's DOM this doesn't seem to work.

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• C - How to use both aio_read() and aio_write().

  - by Slav

  I implement game server where I need to both read and write. So I accept incoming connection and start reading from it using aio_read() but when I need to send something, I stop reading using aio_cancel() and then use aio_write(). Within write's callback I resume reading. So, I do read all the time but when I need to send something - I pause reading. It works for ~20% of time - in other case call to aio_cancel() fails with "Operation now in progress" - and I cannot cancel it (even within permanent while cycle). So, my added write operation never happens. How to use these functions well? What did I missed? EDIT: Used under Linux 2.6.35. Ubuntu 10 - 32 bit. Example code: void handle_read(union sigval sigev_value) { /* handle data or disconnection */ } void handle_write(union sigval sigev_value) { /* free writing buffer memory */ } void start() { const int acceptorSocket = socket(AF_INET, SOCK_STREAM, 0); struct sockaddr_in addr; memset(&addr, 0, sizeof(struct sockaddr_in)); addr.sin_family = AF_INET; addr.sin_addr.s_addr = INADDR_ANY; addr.sin_port = htons(port); bind(acceptorSocket, (struct sockaddr*)&addr, sizeof(struct sockaddr_in)); listen(acceptorSocket, SOMAXCONN); struct sockaddr_in address; socklen_t addressLen = sizeof(struct sockaddr_in); for(;;) { const int incomingSocket = accept(acceptorSocket, (struct sockaddr*)&address, &addressLen); if(incomingSocket == -1) { /* handle error ... */} else { //say socket to append outcoming messages at writing: const int currentFlags = fcntl(incomingSocket, F_GETFL, 0); if(currentFlags < 0) { /* handle error ... */ } if(fcntl(incomingSocket, F_SETFL, currentFlags | O_APPEND) == -1) { /* handle another error ... */ } //start reading: struct aiocb* readingAiocb = new struct aiocb; memset(readingAiocb, 0, sizeof(struct aiocb)); readingAiocb->aio_nbytes = MY_SOME_BUFFER_SIZE; readingAiocb->aio_fildes = socketDesc; readingAiocb->aio_buf = mySomeReadBuffer; readingAiocb->aio_sigevent.sigev_notify = SIGEV_THREAD; readingAiocb->aio_sigevent.sigev_value.sival_ptr = (void*)mySomeData; readingAiocb->aio_sigevent.sigev_notify_function = handle_read; if(aio_read(readingAiocb) != 0) { /* handle error ... */ } } } } //called at any time from server side: send(void* data, const size_t dataLength) { //... some thread-safety precautions not needed here ... const int cancellingResult = aio_cancel(socketDesc, readingAiocb); if(cancellingResult != AIO_CANCELED) { //this one happens ~80% of the time - embracing previous call to permanent while cycle does not help: if(cancellingResult == AIO_NOTCANCELED) { puts(strerror(aio_return(readingAiocb))); // "Operation now in progress" /* don't know what to do... */ } } //otherwise it's okay to send: else { aio_write(...); } }

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• jquery in ajax loaded content

  - by Kim Gysen

  My application is supposed to be a single page application and I have the following code that works fine: home.php: <div id="container"> </div> accordion.php: //Click functions: load content $('#parents').click(function(){ //Load parent in container $('#container').load('http://www.blabla.com/entities/parents/parents.php'); }); parents.php: <div class="entity_wrapper"> Some divs and selectors </div> <script type="text/javascript"> $(document).ready(function(){ //Some jQuery / javascript }); </script> So the content loads fine, while the scripts dynamically loaded execute fine as well. I apply this system repetitively and it continues to work smoothly. I've seen that there are a lot of frameworks available on SPA's (such as backbone.js) but I don't understand why I need them if this works fine. From the backbone.js website: When working on a web application that involves a lot of JavaScript, one of the first things you learn is to stop tying your data to the DOM. It's all too easy to create JavaScript applications that end up as tangled piles of jQuery selectors and callbacks, all trying frantically to keep data in sync between the HTML UI, your JavaScript logic, and the database on your server. For rich client-side applications, a more structured approach is often helpful. Well, I totally don't have the feeling that I'm going through the stuff they mention. Adding the javascript per page works really well for me. They are html containers with clear scope and the javascript is just related to that part. More over, the front end doesn't do that much, most of the logic is managed based on Ajax calls to external PHP scripts. Sometimes the js can be a bit more extended for some functionalities, but all just loads as smooth in less than a second. If you think that this is bad coding, please tell me why I cannot do this and more importantly, what is the alternative I should apply. At the moment, I really don't see a reason on why I would change this approach as it just works too well. I'm kinda stuck on this question because it just worries me sick as it seems to easy to be true. Why would people go through hard times if it would be as easy as this...

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