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  • Writing a VM - well formed bytecode?

    - by David Titarenco
    Hi, I'm writing a virtual machine in C just for fun. Lame, I know, but luckily I'm on SO so hopefully no one will make fun :) I wrote a really quick'n'dirty VM that reads lines of (my own) ASM and does stuff. Right now, I only have 3 instructions: add, jmp, end. All is well and it's actually pretty cool being able to feed lines (doing it something like write_line(&prog[1], "jmp", regA, regB, 0); and then running the program: while (machine.code_pointer <= BOUNDS && DONE != true) { run_line(&prog[machine.cp]); } I'm using an opcode lookup table (which may not be efficient but it's elegant) in C and everything seems to be working OK. My question is more of a "best practices" question but I do think there's a correct answer to it. I'm making the VM able to read binary files (storing bytes in unsigned char[]) and execute bytecode. My question is: is it the VM's job to make sure the bytecode is well formed or is it just the compiler's job to make sure the binary file it spits out is well formed? I only ask this because what would happen if someone would edit a binary file and screw stuff up (delete arbitrary parts of it, etc). Clearly, the program would be buggy and probably not functional. Is this even the VM's problem? I'm sure that people much smarter than me have figured out solutions to these problems, I'm just curious what they are!

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  • jQuery.keypad Performance Issues

    - by John Duff
    I am working on a Kiosk Touch Screen application and using the JQuery.keypad plugin and noticing some major performance issues. If you click a number of buttons in rapid succession the CPU gets pegged, the button clicks don't keep up with the clicking and some button presses even get lost. On my dev machine this isn't as noticeable, but on the Kiosk itself with 1 gig of ram it's painful. Trying the demo keypad at http://keith-wood.name/keypad.html#inline the one with multiple targets (which is the case with mine) has the exact same issues. Does anyone have any suggestions on how we might be able to improve this? The Kiosk runs in Firefox only so something specific to that would work. I'm using v1.2.1 of jquery.keypad and just upgraded to v1.4.2 of jquery.

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  • C++ Passing `this` into method by reference

    - by David
    I have a class constructor that expects a reference to another class object to be passed in as an argument. I understand that references are preferable to pointers when no pointer arithmetic will be performed or when a null value will not exist. This is the header declaration of the constructor: class MixerLine { private: MIXERLINE _mixerLine; public: MixerLine(const MixerDevice& const parentMixer, DWORD destinationIndex); ~MixerLine(); } This is the code that calls the constructor (MixerDevice.cpp): void MixerDevice::enumerateLines() { DWORD numLines = getDestinationCount(); for(DWORD i=0;i<numLines;i++) { MixerLine mixerLine( this, i ); // other code here removed } } Compilation of MixerDevice.cpp fails with this error: Error 3 error C2664: 'MixerLine::MixerLine(const MixerDevice &,DWORD)' : cannot convert parameter 1 from 'MixerDevice *const ' to 'const MixerDevice &' But I thought pointer values could be assigned to pointers, e.g. Foo* foo = new Foo(); Foo& bar = foo;

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  • php push 2d array into mysql

    - by john
    Hay All, I cant seem to get my head around this dispite the number to examples i read. Basically I have a 2d array and want to insert it into MySQL. The array contains a few strings. I cant get the following to work... $value = addslashes(serialize($temp3));//temp3 is my 2d array, do i need to use keys? (i am not at the moment) $query = "INSERT INTO table sip (id,keyword,data,flags) VALUES(\"$value\")"; mysql_query($query) or die("Failed Query"); Thanks Guys,

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  • Oracle SQL CMD Line!!!

    - by DAVID
    Hi when ever perform select statements in the command line tool it doesnt use all of the space.. ive modified buffer size and window size and it just doesnt work. here is the Screenshot http://img19.imageshack.us/img19/8954/cmdoracle.jpg

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  • Observer Design Pattern - multiple event types

    - by David
    I'm currently implementing the Observer design pattern and using it to handle adding items to the session, create error logs and write messages out to the user giving feedback on their actions (e.g. You've just logged out!). I began with a single method on the subject called addEvent() but as I added more Observers I found that the parameters required to detail all the information I needed for each listener began to grow. I now have 3 methods called addMessage(), addStorage() and addLog(). These add data into an events array that has a key related to the event type (e.g. log, message, storage) but I'm starting to feel that now the subject needs to know too much about the listeners that are attached. My alternative thought is to go back to addEvent() and pass an event type (e.g. USER_LOGOUT) along with the data associated and each Observer maintains it's own list of event handles it is looking for (possibly in a switch statement), but this feels cumbersome. Also, I'd need to check that sufficient data had also been passed along with the event type. What is the correct way of doing this? Please let me know if I can explain any parts of this further. I hope you can help and see the problem I'm battling with.

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  • Integer output in Java method not same as pre-converted char value.

    - by David
    I'm trying to parse a simple text file in an integer method and then output an integer from such file so that other parts of the program can use it. For testing purposes it also displays the character value (9 in this case). The integer value for some reason is 57. I've also tried it with another part of the text file (which in that case should be 5, but is instead 53). After looking at an ASCII chart, I see that 57 is the ASCII version of the "symbol" 9 and that 53 is the ASCII version of the "symbol" 5. Is there any simple way I can fix this? I'm getting kind of frustrated as I'm a Java newbie (I've mostly only used FreePascal before this).

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  • byte[] to wav file

    - by John
    Hi, It would be great if you could tell me how I could save a byte[] to a wav file. Sometimes I need to set different samplerate, number of bits and channels. Thanks for your help.

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  • Specializating a template function that takes a universal reference parameter

    - by David Stone
    How do I specialize a template function that takes a universal reference parameter? foo.hpp: template<typename T> void foo(T && t) // universal reference parameter foo.cpp template<> void foo<Class>(Class && class) { // do something complicated } Here, Class is no longer a deduced type and thus is Class exactly; it cannot possibly be Class &, so reference collapsing rules will not help me here. I could perhaps create another specialization that takes a Class & parameter (I'm not sure), but that implies duplicating all of the code contained within foo for every possible combination of rvalue / lvalue references for all parameters, which is what universal references are supposed to avoid. Is there some way to accomplish this? To be more specific about my problem in case there is a better way to solve it: I have a program that can connect to multiple game servers, and each server, for the most part, calls everything by the same name. However, they have slightly different versions for a few things. There are a few different categories that these things can be: a move, an item, etc. I have written a generic sort of "move string to move enum" set of functions for internal code to call, and my server interface code has similar functions. However, some servers have their own internal ID that they communicate with, some use strings, and some use both in different situations. Now what I want to do is make this a little more generic. I want to be able to call something like ServerNamespace::server_cast<Destination>(source). This would allow me to cast from a Move to a std::string or ServerMoveID. Internally, I may need to make a copy (or move from) because some servers require that I keep a history of messages sent. Universal references seem to be the obvious solution to this problem. The header file I'm thinking of right now would expose simply this: namespace ServerNamespace { template<typename Destination, typename Source> Destination server_cast(Source && source); } And the implementation file would define all legal conversions as template specializations.

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  • Lamda expression will not compile

    - by John Soer
    I am very confused I have this lamba expression tvPatientPrecriptionsEntities.Sort((p1, p2) => p1.MedicationStartDate.Value.CompareTo(p2.MedicationStartDate.Value)); Visual studio will not compile it and complains about syntax. I converted the lamba expression to an anonymous delegate as so tvPatientPrecriptionsEntities.Sort( delegate(PatientPrecriptionsEntity p1, PatientPrecriptionsEntity p2) { return p1.MedicationStartDate.Value.CompareTo(p2.MedicationStartDate.Value); } ); and it works fine. The project is uses the .net 3.5 framework and I have a reference to system.linq.

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  • Setting Scala "Platform" for NetBeans 6.8 on Ubuntu Lucid Lynx

    - by David
    I'm trying to use NetBeans 6.8 with Scala, and it can't find the "Scala Platform" (whatever that is supposed to be). I'm using Ubuntu Lucid Lynx (fully updated). The libraries are in /usr/share/java, the binaries in /usr/bin, the docs in /usr/share/doc/scala-doc/, and the sources are uninstalled. I think that NetBeans is looking for Scala to be in one single directory (with bin, lib, etc.). I created /usr/share/scala and placed links to the other directories, but it still didn't quite make it. Can someone straighten me out? (And why is it a "platform"? More needless jargon...)

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  • ASP .NET Added Event Handlers to buttons on Page_Load. Event handlers do not fire the first click, b

    - by John
    Background: I am customizing an existing ASP .NET / C# application. It has it's own little "framework" and conventions for developers to follow when extending/customizing its functionality. I am currently extending some of it's administrative functionality, to which the framework provides a contract to enforce implementation of the GetAdministrationInterface() method, which returns System.Web.UI.Control. This method is called during the Page_Load() method of the page hosting the GUI interface. Problem: I have three buttons in my GUI, each of which have been assigned an Event Handler. My administration GUI loads up perfectly fine, but clicking any of the buttons doesn't do what I expect them to do. However, when I click them a second time, the buttons work. I placed breakpoints at the the beginning of each event handler method and stepped through my code. On the first click, none of the event handlers are triggered. On the second click, they are triggered. Any ideas? Example of Button Definition Button btn = new Button(); btn.Text = "Click Me Locked Screen"; bth.Click += new EventHandler(Btn_Click); Example of Event Handler Method Definition void Btn_Click(object sender, EventArgs e) { // Do Something }

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  • Setup SVN/LAMP/Test Server/ on linux, where to start?

    - by John Isaacks
    I have a ubuntu machine I have setup. I installed apache2 and php5 on it. I can access the web server from other machines on the network via http://linux-server. I have subversion installed on it. I also have vsftpd installed on it so I can ftp to it from another computer on the network. Myself and other users currently use dreamweaver to checkin-checkout files directly from our live site to make changes. I want the connect to the linux server from pc. make the changes on the test server until ready and then pushed to the live site. I want to use subversion also into this workflow as well. but not sure what the best workflow is or how to set this up. I have no experience with linux, svn, or even using a test server, the checkin/out we are currently doing is the way I have always done it. I have hit many snags already just getting what I have setup because of my lack of knowledge in the area. Dreamweaver 5 has integration with subversion but I can't figure out how to get it to work. I want to setup and create the best workflow possible. I dont expect anyone to be able to give me an answer that will enlighten me enough to know everthing I need to know to do what I want to do (altough if possible that would be great) instead I am looking for maybe a knowledge path like answer. Like a general outline of what I need to do accompanied with links to learn how to do it. like read this book to learn linux, then read this article to learn svn, etc., then you should know what to do. I would be happy just getting it all setup, but I would like to know what I am actually doing while setting it up too.

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  • javascript change innerhtml

    - by David
    ok im new at javascript, but im trying to change the innerhtml of a div tag, heres my script and its not working: <head> <script type="text/javascript"> function var1() { document.getElementById('test').innerHTML = 'hi'; } window.onLoad = var1(); </script> </head> <body> <div id="test">change</div> </body> it should work but for some reason its not, any help?

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  • var in C# - Why can't it be used as a member variable?

    - by David Neale
    Why is it not possible to have implicitly-typed variables at a class level within C# for when these variables are immediately assigned? ie: public class TheClass { private var aList = new List<string>(); } Is it just something that hasn't been implemented or is there a conceptual/technical reason for why it hasn't been done?

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  • ActionScript: Determine wether superclass implements a particular interface?

    - by David Wolever
    Is there any non-hacky way to determine wether a class' superclass implements a particular interface? For example, assume I've got: class A extends EventDispatcher implements StuffHolder { private var myStuff = someKindOfStuff; public function getStuff():Array { if (super is StuffHolder) // <<< this doesn't work return super['getStuff']().concat([myStuf]); return [myStuff]; } class B extends A { private var myStuff = anotherKindOfStuff; } How could I perform that super is StuffHolder test in a way that, well, works? In this case, it always returns true.

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  • How can I generate a FindBugs report that shows me the bugs removed between two revisions in the bug

    - by David Deschenes
    I am attempting to execute a combination of the FindBugs commands filterBugs and convertXmlToText, against a bug database that I created, to generate a report that shows me the all of the bugs removed between two revisions of the system that I am working on. Unfortunately, the resulting report does not show any bug details. It appears that the convertXmlToText throws away all bugs that are dead (aka inactive)... the exact set of bugs that I'd like to see. Below is what I see when I pass the results of the filterBugs command to the mineBugHistory command: build/findbugs/bin> ./filterBugs -before r39921 -absent r41558 -active:false ../../../mmfg/bugDB-2.xml | ./mineBugHistory seq version time classes NCSS added newCode fixed removed retained dead active 0 r39764 1271169398000 438 74069 0 64 0 0 0 0 64 1 r39921 1271186932000 441 74333 0 0 22 0 42 0 42 2 r40149 1271185876000 449 74636 0 0 3 0 39 22 39 3 r40344 1271180332000 452 74789 0 0 7 0 32 25 32 4 r40558 1271179612000 452 74806 0 0 1 0 31 32 31 5 r40793 1271178818000 464 75610 0 0 20 0 11 33 11 6 r41016 1271176154000 467 75712 0 0 4 0 7 53 7 7 r41303 1271175616000 481 76931 0 0 7 0 0 57 0 8 r41558 1271175026000 486 77793 0 0 0 0 0 64 0 What I'd like to see in the HTML report is the list of the 64 bugs that are shown as active in version r39764 (sequence # 0). Below is the command line that I am using to generate the HTML report: build/findbugs/bin> ./filterBugs -before r39921 -absent r41558 -active:false ../../../mmfg/bugDB-2.xml | ./convertXmlToText -html:fancy-hist.xsl > ../../../mmfg/bugDB-removed.html

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  • PostgreSQL: Why does this simple query not use the index?

    - by David
    I have a table t with a column c, which is an int and has a btree index on it. Why does the following query not utilize this index? explain select c from t group by c; The result I get is: HashAggregate (cost=1005817.55..1005817.71 rows=16 width=4) -> Seq Scan on t (cost=0.00..946059.84 rows=23903084 width=4) My understanding of indexes is limited, but I thought such queries were the purpose of indexes.

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  • PostgreSQL pgdb driver raises "can't rollback" exception

    - by David Parunakian
    Hello, for some reason I'm experiencing the Operational Error with "can't rollback" message when I attempt to roll back my transaction in the following context: try: cursors[instance].execute("lock revision, app, timeout IN SHARE MODE") cursors[instance].execute("insert into app (type, active, active_revision, contents, z) values ('session', true, %s, %s, 0) returning id", (cRevision, sessionId)) sAppId = cursors[instance].fetchone()[0] cursors[instance].execute("insert into revision (app_id, type) values (%s, 'active')", (sAppId,)) cursors[instance].execute("insert into timeout (app_id, last_seen) values (%s, now())", (sAppId,)) connections[instance].commit() except pgdb.DatabaseError, e: connections[instance].rollback() return "{status: 'error', errno:4, errmsg: \"%s\"}"%(str(e).replace('\"', '\\"').replace('\n', '\\n').replace('\r', '\\r')) The driver in use is PGDB. What is fundamentally wrong here?

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  • Are Dynamic Prepared Statements Bad? (with php + mysqli)

    - by John
    I like the flexibility of Dynamic SQL and I like the security + improved performance of Prepared Statements. So what I really want is Dynamic Prepared Statements, which is troublesome to make because bind_param and bind_result accept "fixed" number of arguments. So I made use of an eval() statement to get around this problem. But I get the feeling this is a bad idea. Here's example code of what I mean // array of WHERE conditions $param = array('customer_id'=>1, 'qty'=>'2'); $stmt = $mysqli->stmt_init(); $types = ''; $bindParam = array(); $where = ''; $count = 0; // build the dynamic sql and param bind conditions foreach($param as $key=>$val) { $types .= 'i'; $bindParam[] = '$p'.$count.'=$param["'.$key.'"]'; $where .= "$key = ? AND "; $count++; } // prepare the query -- SELECT * FROM t1 WHERE customer_id = ? AND qty = ? $sql = "SELECT * FROM t1 WHERE ".substr($where, 0, strlen($where)-4); $stmt->prepare($sql); // assemble the bind_param command $command = '$stmt->bind_param($types, '.implode(', ', $bindParam).');'; // evaluate the command -- $stmt->bind_param($types,$p0=$param["customer_id"],$p1=$param["qty"]); eval($command); Is that last eval() statement a bad idea? I tried to avoid code injection by encapsulating values behind the variable name $param. Does anyone have an opinion or other suggestions? Are there issues I need to be aware of?

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  • Calculating moving average/stdev in SAS?

    - by John
    Hye guys, I included a screenshot to help clarify my problem: http://i40.tinypic.com/mcrnmv.jpg. I'm trying to calculate some kind of moving average and moving standard deviation. The thing is I want to calculate the coefficients of variation (stdev/avg) for the actual value. Normally this is done by calculating the stdev and avg for the past 5 years. However sometimes there will be observations in my database for which I do not have the information of the past 5 years (maybe only 3, 2 etc). That's why i want a code that will calculate the avg and stdev even if there is no information for the whole 5 years. Also, as you see in the observations, sometimes I have information over more than 5 years, when this is the case I need some kind of moving average which allows me to calculate the avg and stdev for the past 5 year. So if a company has information for 7 years I need some kind of code that will calculate the avg and stdev for, lets say, 1997 (by 1991-1996), 1998 (by 1992-1997) and 1999 (1993-1998). As i'm not very familiar with sas commands it should look (very very roughly) like: set var if year = i then stdev=stdev(year(i-6) untill year(i-1)) and average = avg(year(i-6) untill year(i-1)) Or something like this, I really have no clue, I'm gonna try and figure it out but it's worth posting it if I won't find it myself. Thanks!

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  • PropertyPlaceholderConfigurer vs Filters -- Spring Beans

    - by John
    Hi there. I've got a question regarding the difference between PropertyPlaceholderConfigurer (org.springframework.beans.factory.config.PropertyPlaceholderConfigurer) and normal filters defined in my pom.xml. I've been looking at examples, and it seems that even though filters are defined and marked to be active by default in the pom.xml they still make use of PropertyPlaceholderConfigurer in Spring's applicationContext.xml. This means that the pom.xml has a reference to a filter-LOCAL.properties while applicationContext.xml has a reference to application.properties and they both contain the same settings. Why is that? Is that how it is supposed to be done? I'm able to run the goal mvn jetty:run without the application.properties present, but if I add settings to the application.properties that differ from the filter-LOCAL.properties they don't seem to override. Here's an example of what I mean: pom.xml <profiles <profile <idLOCAL <activation <activeByDefaulttrue </activation <properties <envLOCAL </properties </profile </profiles applicationContext.xml <bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer" <property name="locations" <list <valueclasspath:application.properties </list </property <property name="ignoreResourceNotFound" value="true"/ </bean <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close" <property name="driverClassName" value="${jdbc.driver}"/ <property name="url" value="${jdbc.url}"/ <property name="username" value="${jdbc.username}"/ <property name="password" value="${jdbc.password}"/ </bean an example of the content of application.properties and filters-LOCAL.properties jdbc.driver=org.postgresql.Driver jdbc.url=jdbc:postgresql://localhost/shoutbox_dev jdbc.username=tester jdbc.password=tester Can I remove the propertyConfigurer from the applicationContext, create a PROD filter and disregard the application.properties file, or will that give me issues when deploying to the production server?

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  • Is there a Firebug console -vsdoc.js?

    - by David Murdoch
    If not, does anyone care to write one? I would do it myself...but I don't have time right now...maybe next week (unless someone beats me to it). If you are bored and want to compile the vsdoc: Here is the Firebug API. Here is a blog post about the format for VS doc comments for intellisense. Here is an example vsdoc (jquery-1.4.1-vsdoc.js). I created the following because I kept typing cosnole instead of console. You can use it as a starting point (ish). console = { /// <summary> /// 1: The javascript console /// </summary> /// <returns type="Object" /> }; console.log = function (object) { /// <summary> /// Write to the console's log /// </summary> /// <returns type="null" /> /// <param name="object" type="Object"> /// Write the object to the console's log /// </param> };

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