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  • ASP.net file operations delay

    - by mtranda
    Ok, so here's the problem: I'm reading the stream from a FileUpload control, reading in chunks of n bytes and writing the array in a loop until I reach the stream's end. Now the reason I do this is because I need to check several things while the upload is still going on (rather than doing a Save(); which does the whole thing in one go). Here's the problem: when doing this from the local machine, I can see the file just fine as it's uploading and its size increases (had to add a Sleep(); clause in the loop to actually get to see the file being written). However, when I upload the file from a remote machine, I don't get to see it until the the file has completed uploading. Also, I've added another call to write the progress to a text file as the progress is going on, and I get the same thing. Local: the file updates as the upload goes on, remote: the token file only appears after the upload's done (which is somewhat useless since I need it while the upload's still happening). Is there some sort of security setting in (or ASP.net) that maybe saves files in a temporary location for remote machines as opposed to the local machine and then moves them to the specified destination? I would liken this with ASP.net displaying error messages when browsing from the local machine (even on the public hostname) as opposed to the generic compilation error page/generic exception page that is shown when browsing from a remote machine (and customErrors are not off) Any clues on this? Thanks in advance.

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  • Multiple calls to preg_replace alters result

    - by Hurpe
    I have a bunch of files that were named in a somewhat standard format. The standard form is basically this: [integer]_word1_word2_word3_ ... _wordn where a word could really be anything, but all words are separated by an underscore. There is really only 3 things I want to do to the text: 1.) I want to modify the integer, which is always at the beginning, so that something like "200" would become $ 200.00. 2.) replace any "words" of the form "with", "With", "w/", or "W/" with "with". 3.) Replace all underscores with a space. I wrote three different preg_replace calls to do the trick. They are as follows: 1.) $filename = preg_replace("/(^[0-9]+)/","$ $1.00",$filename) 2.) $filename = preg_replace("/_([wW]|[wW]ith)_/"," with ",$filename) 3.) $filename = preg_replace("/_/"," ",$filename); Each replacement works as expected when run individually, but when all three are run, the 2nd replacement is ignored. Why would something like that occur? Thanks for the help!

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  • ArrayAccess multidimensional (un)set?

    - by anomareh
    I have a class implementing ArrayAccess and I'm trying to get it to work with a multidimensional array. exists and get work. set and unset are giving me a problem though. class ArrayTest implements ArrayAccess { private $_arr = array( 'test' => array( 'bar' => 1, 'baz' => 2 ) ); public function offsetExists($name) { return isset($this->_arr[$name]); } public function offsetSet($name, $value) { $this->_arr[$name] = $value; } public function offsetGet($name) { return $this->_arr[$name]; } public function offsetUnset($name) { unset($this->_arr[$name]); } } $arrTest = new ArrayTest(); isset($arrTest['test']['bar']); // Returns TRUE echo $arrTest['test']['baz']; // Echo's 2 unset($arrTest['test']['bar']; // Error $arrTest['test']['bar'] = 5; // Error I know $_arr could just be made public so you could access it directly, but for my implementation it's not desired and is private. The last 2 lines throw an error: Notice: Indirect modification of overloaded element. I know ArrayAccess just generally doesn't work with multidimensional arrays, but is there anyway around this or any somewhat clean implementation that will allow the desired functionality? The best idea I could come up with is using a character as a separator and testing for it in set and unset and acting accordingly. Though this gets really ugly really fast if you're dealing with a variable depth. Does anyone know why exists and get work so as to maybe copy over the functionality? Thanks for any help anyone can offer.

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  • are projects with high developer turn over rate really a bad thing?

    - by John
    I've inherited a lot of web projects that experienced high developer turn over rates. Sometimes these web projects are a horrible patchwork of band aid solutions. Other times they can be somewhat maintainable mozaics of half-done features each built with a different architectural style. Everytime I inherit these projects, I wish the previous developers could explain to me why things got so bad. What puzzles me is the reaction of the owners (either a manager, a middle man company, or a client). They seem to think, "Well, if you leave, I'll just find another developer." Or they think, "Oh, it costs that much money to refactor the system? I know another developer who can do it at half the price. I'll hire him if I can't afford you." I'm guessing that the high developer turn over rate is related to the owner's mentality of "If you think it's a bad idea to build this, I'll just find another (possibly cheaper) developer to do what I want". For the owners, the approach seems to work because their business is thriving. Unfortunately, it's no fun for the developers that go AWOL 3-4 months after working with poor code, strict timelines, and little feedback. So my question is the following: Are the following symptoms of a project really such a bad thing for business? high developer turn over rate poorly built technology - often a patchwork of different and inappropriately used architectural styles owners without a clear roadmap for their web project, and they request features on a whim I've seen numerous businesses prosper while experiencing the symptoms above. So as a programmer, even though my instincts tell me the above points are terrible, I'm forced to take a step back and ask, "are things really that bad in the grand scheme of things?" If not, I will re-evaluate my approach to these projects.

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  • how to display my list with n amount on each line in Python

    - by user1786698
    im trying to display my list with 7 states on each line here is what i have so far, but it displays as one long string of all the states with quotes around each state. I forgot to mention that this is for my CS class and we havent learned iter yet so we not allowed to use it. the only hint i was given was to to turn STATE_LIST into a string then use '\n' to break it up state = str(STATE_LIST) displaystates = Text(Point(WINDOW_WIDTH/2, WINDOW_HEIGHT/2), state.split('\n')) displaystates.draw(win) and STATE_LIST looks like this STATE_VOTES = { "AL" : 9, # Alabama "AK" : 3, # Alaska "AZ" : 11, # Arizona "AR" : 6, # Arkansas "CA" : 55, # California "CO" : 9, # Colorado "CT" : 7, # Connecticut "DE" : 3, # Delaware "DC" : 3, # Washington DC "FL" : 29, # Florida "GA" : 16, # Georgia "HI" : 4, # Hawaii "ID" : 4, # Idaho "IL" : 20, # Illinois "IN" : 11, # Indiana "IA" : 6, # Iowa "KS" : 6, # Kansas "KY" : 8, # Kentucky "LA" : 8, # Louisiana "ME" : 4, # Maine "MD" : 10, # Maryland "MA" : 11, # Massachusetts "MI" : 16, # Michigan "MN" : 10, # Minnesota "MS" : 6, # Mississippi "MO" : 10, # Missouri "MT" : 3, # Montana "NE" : 5, # Nebraska "NV" : 6, # Nevada "NH" : 4, # New Hampshire "NJ" : 14, # New Jersey "NM" : 5, # New Mexico "NY" : 29, # New York "NC" : 15, # North Carolina "ND" : 3, # North Dakota "OH" : 18, # Ohio "OK" : 7, # Oklahoma "OR" : 7, # Oregon "PA" : 20, # Pennsylvania "RI" : 4, # Rhode Island "SC" : 9, # South Carolina "SD" : 3, # South Dakota "TN" : 11, # Tennessee "TX" : 38, # Texas "UT" : 6, # Utah "VT" : 3, # Vermont "VA" : 13, # Virginia "WA" : 12, # Washington "WV" : 5, # West Virginia "WI" : 10, # Wisconsin "WY" : 3 # Wyoming } STATE_LIST = sorted(list(STATE_VOTES.keys())) I am trying to get it to look somewhat like this

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  • Keep Hibernate Initializer from Crashing Program

    - by manyxcxi
    I have a Java program using a basic Hibernate session factory. I had an issue with a hibernate hbm.xml mapping file and it crashed my program even though I had the getSessionFactory() call in a try catch try { session = SessionFactoryUtil.getSessionFactory().openStatelessSession(); session.beginTransaction(); rh = getRunHistoryEntry(session); if(rh == null) { throw new Exception("No run history information found in the database for run id " + runId_ + "!"); } } catch(Exception ex) { logger.error("Error initializing hibernate"); } It still manages to break out of this try/catch and crash the main thread. How do I keep it from doing this? The main issue is I have a bunch of cleanup commands that NEED to be run before the main thread shuts down and need to be able to guarantee that even after a failure it still cleans up and goes down somewhat gracefully. The session factory looks like this: public class SessionFactoryUtil { private static final SessionFactory sessionFactory; static { try { // Create the SessionFactory from hibernate.cfg.xml sessionFactory = new Configuration().configure().buildSessionFactory(); } catch (Throwable ex) { // Make sure you log the exception, as it might be swallowed System.err.println("Initial SessionFactory creation failed." + ex); throw new ExceptionInInitializerError(ex); } } public static SessionFactory getSessionFactory() { try { return sessionFactory; } catch(Exception ex) { return null; } } }

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  • Are there any configurable parameters to the gpsd?

    - by danatel
    I use the gpsd daemon with my application. Sometimes, the gpsd ceases to work with no apparent reason (clean sky). Even the gpsmon monitor shows no fix. Are there any parameters which must be set? Or is it a hardware problem? I am surprissed that many satellites are visible but the "Stat" bitmap does not contain the bit 7 - ephemeris data available. Should i somewhat pre-configure my position to allow for correct ephemeris data? Here is my gpsmon screen: 127.0.0.1:2947:/dev/ttyS3 SiRF binary> ^[[4~ -¦¦¦¦¦¦¦¦¦¦¦ X ¦¦¦¦¦¦ Y ¦¦¦¦¦¦ Z ¦¦¦¦¦¦¦¦¦¦ North ¦¦¦¦ East ¦¦¦¦¦ Alt ¦¦¦¦¦¦¦¦¦¬ -Pos: 3949260 1166016 4856299 m 49.89411° 16.44920° 1379 m - -Vel: 0.0 0.0 0.0 m/s 0.0 0.0 0.0 climb m/s- -Week+TOW:1578+224837.06 Day: 2 14:27:17.06 Heading: 0.0° 0.0 speed m/s- -Skew: -13.025817 TZ: -7200 HDOP: 0.0 M1:00 M2: 00 - -Fix: 0 = - L¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦ Packet type 2 (0x02) ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦- -¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¬-¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¬ -Ch PRN Az El Stat C/N ? A --Version: - - 0 2 243 19 003f 40.4 -L¦¦¦¦¦¦¦ Packet Type 6 (0x06) ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦- - 1 10 249 68 003f 43.0 --¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¬ - 2 13 90 30 003f 40.9 --SVs: 0 Drift: 96506 Bias: 135976716 - - 3 7 66 67 003f 39.8 --Estimated GPS Time: 224837059 - - 4 5 295 49 003d 39.7 -L¦¦¦¦¦¦¦ Packet type 7 (0x07) ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦- - 5 8 210 69 003f 41.0 --¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¬ - 6 23 96 5 002d 28.0 --Max: 167.570Lat: 132.129Time: 0.075 MS: 02 - - 7 6 43 3 002d 23.1 -L¦¦¦¦¦¦¦ Packet type 9 (0x09) ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦- - 8 28 163 16 003f 39.8 --¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¬ - 9 0 0 0 0000 0.0 --SVs: 11 = 8 10 7 5 13 2 28 23 3 6 4 - -10 3 55 4 002d 24.7 -L¦¦¦¦¦¦¦ Packet type 13 (0x0D) ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦- -11 0 0 0 0000 0.0 --¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¬ L¦¦¦ Packet Type 4 (0x04) ¦¦¦--DGPS source: 1 (SBAS) Corrections: 12 - L¦¦¦¦¦¦¦ Packet type 27 (0x1B) ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦-q

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  • Fastest way to modify a decimal-keyed table in MySQL?

    - by javanix
    I am dealing with a MySQL table here that is keyed in a somewhat unfortunate way. Instead of using an auto increment table as a key, it uses a column of decimals to preserve order (presumably so its not too difficult to insert new rows while preserving a primary key and order). Before I go through and redo this table to something more sane, I need to figure out how to rekey it without breaking everything. What I would like to do is something that takes a list of doubles (the current keys) and outputs a list of integers (which can be cast down to doubles for rekeying). For example, input {1.00, 2.00, 2.50, 2.60, 3.00} would give output {1, 2, 3, 4, 5). Since this is a database, I also need to be able to update the rows nicely: UPDATE table SET `key`='3.00' WHERE `key`='2.50'; Can anyone think of a speedy algorithm to do this? My current thought is to read all of the doubles into a vector, take the size of the vector, and output a new vector with values from 1 => doubleVector.size. This seems pretty slow, since you wouldn't want to read every value into the vector if, for instance, only the last n/100 elements needed to be modified. I think there is probably something I can do in place, since only values after the first non-integer double need to be modified, but I can't for the life of me figure anything out that would let me update in place as well. For instance, setting 2.60 to 3.00 the first time you see 2.50 in the original key list would result in an error, since the key value 3.00 is already used for the table.

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  • Is there such a thing as IMAP for podcasts?

    - by Gerrit
    Is there such a thing as IMAP for podcasts? I own a desktop, laptop, iPod, smartphone and a web-client all downloading StackOverflow Podcasts. (among others) They all tell me which episodes are available and which are already played. Everything is a horrible mess, ofcourse. My iPod is somewhat in sync with my desktop, but everything else is a random jungle. The same problem with e-mail is solved by IMAP. Every device gets content and meta-information from one server, and stays in sync with it. Per device, I can set preferences (do or do not download the complete archive including junkmail). Can we implement the IMAP approach for podcasts? Or is there a better metaphore/standard to solve this problem? How will the adoption-strategy look like? (by the way: except for the Windows smartphone, I own a full Apple-stack of products. Even then, I run into this problem) UPDATE The RSS-to-Imap link to sourceforge looks promesting, but very alpha/experimental. UPDATE 2 The one thing RSS is missing is the command/method/parameter/attribute to delete/unread items. RSS can only add, not remove. If RSS(N+1) (3?) could add a value for unread="true|false", it would be solved. If I cache all my RSS-feeds on my own server, and add the attribute myself, I only would have to convince iTunes and every other client to respect that.

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  • Practical refactoring using unit tests

    - by awhite
    Having just read the first four chapters of Refactoring: Improving the Design of Existing Code, I embarked on my first refactoring and almost immediately came to a roadblock. It stems from the requirement that before you begin refactoring, you should put unit tests around the legacy code. That allows you to be sure your refactoring didn't change what the original code did (only how it did it). So my first question is this: how do I unit-test a method in legacy code? How can I put a unit test around a 500 line (if I'm lucky) method that doesn't do just one task? It seems to me that I would have to refactor my legacy code just to make it unit-testable. Does anyone have any experience refactoring using unit tests? And, if so, do you have any practical examples you can share with me? My second question is somewhat hard to explain. Here's an example: I want to refactor a legacy method that populates an object from a database record. Wouldn't I have to write a unit test that compares an object retrieved using the old method, with an object retrieved using my refactored method? Otherwise, how would I know that my refactored method produces the same results as the old method? If that is true, then how long do I leave the old deprecated method in the source code? Do I just whack it after I test a few different records? Or, do I need to keep it around for a while in case I encounter a bug in my refactored code? Lastly, since a couple people have asked...the legacy code was originally written in VB6 and then ported to VB.NET with minimal architecture changes.

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  • Passing data structures to different threads

    - by Robb
    I have an application that will be spawning multiple threads. However, I feel there might be an issue with threads accessing data that they shouldn't be. I'm relatively new to threading so bare with me. Here is the structure of the threaded application (sorry for the crudeness): MainThread / \ / \ / \ Thread A Thread B / \ / \ / \ / \ / \ / \ Thread A_1 Thread A_2 Thread B_1 Thread B_2 Under each lettered thread (which could be many), there will only be two threads and they are fired of sequentially. The issue i'm having is I'm not entirely sure how to pass in a datastructure into these threads. So, the datastructure is created in MainThread, will be modified in the lettered thread (Thread A, etc) specific to that thread and then a member variable from that datastructure is sent to Letter_Numbered threads. Currently, the lettered thread class has a member variable and when the class is constructed, the datastructure from mainthread is passed in by reference, invoking the copy constructor so the lettered thread has it's own copy to play with. The lettered_numbered thread simply takes in a string variable from the data structure within the lettered thread. My question is, is this accceptable? Is there a much better way to ensure each lettered thread gets its own data structure to play with? Sorry for the somewhat poor explanation, please leave comments and i'll try to clarify.

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  • Helpful advice on developing a professional MS Word add-on

    - by Dan Tao
    A few months back I put together a simple proof-of-concept piece of software for a small firm with an idea for a document editing tool. The company wanted this tool to be integrated into Microsoft Word, understandably, to maximize its accessibility to the average user. I essentially wrote the underlying library with all of the core functionality as a C# project, and then used VSTO to get it running inside of Word. It felt like a bit of a duct tape solution, really; but then, I have (practically) zero experience developing tools for integration with MS Office, and it was only a proof of concept anyway. Well, the firm was quite pleased with my work overall, and they're looking to move from "proof of concept" to the real deal. Fortunately, as I said, the core functionality is all there and will only need to be somewhat tweaked and enhanced. My main concern is figuring out how to put together an application that will integrate with MS Word in a clean and polished way, and which can be deployed easily in accordance with a regular user's expectations (i.e., simply running an install program and voila, it's there in Word). I seem to remember reading somewhere that nobody uses VSTO for real professional projects. Is this true? False? What are the alternatives? And what are the tips and gotchas that I should be aware of before getting started on this issue of MS Word integration?

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  • Powerpoint displays a "can't start the application" error when an Excel Chart object is embedded in

    - by A9S6
    This is a very common problem when Excel Worksheet or Chart is embedded into Word or Powerpoint. I am seeing this problem in both Word and Powerpoint and the reason it seems is the COM addin attached to Excel. The COM addin is written in C# (.NET). See the attached images for error dialogs. I debugged the addin and found a very strange behavior. The OnConnection(...), OnDisConnection(...) etc methods in the COM addin works fine until I add an event handler to the code. i.e. handle the Worksheet_SheetChange, SelectionChange or any similar event available in Excel. As soon as I add even a single event handler (though my code has several), Word and Powerpoint start complaining and do not Activate the embedded object. On some of the posts on the internet, people have been asked to remove the anti-virus addins for office (none in my case) so this makes me believe that the problem is somewhat related to COM addins which are loaded when the host app activates the object. Does anyone have any idea of whats happening here?

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  • Distributing a bundle of files across an extranet

    - by John Zwinck
    I want to be able to distribute bundles of files, about 500 MB per bundle, to all machines on a corporate "extranet" (which is basically a few LANs connected using various private mechanisms, including leased lines and VPN). The total number of hosts is roughly 100, and the goal is to get a copy of the bundle from one host onto all the other hosts reliably, quickly, and efficiently. One important issue is that some hosts are grouped together on single fast LANs in which case the network I/O should be done once from one group to the next and then within each group between all the peers. This is as opposed to a strict central server system where multiple hosts might each fetch the same bundle over a slow link, rather than once via the slow link and then between each other quickly. A new bundle will be produced every few days, and occasionally old bundles will be deleted (but that problem can be solved separately). The machines in question happen to run recent Linuxes, but bonus points will go to solutions which are at least somewhat cross-platform (in which case the bundle might differ per platform but maybe the same mechanism can be used). That's pretty much it. I'm not opposed to writing some code to handle this, but it would be preferable if it were one of bash, Python, Ruby, Lua, C, or C++.

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  • How to genrate a monochrome bit mask for a 32bit bitmap

    - by Mordachai
    Under Win32, it is a common technique to generate a monochrome bitmask from a bitmap for transparency use by doing the following: SetBkColor(hdcSource, clrTransparency); VERIFY(BitBlt(hdcMask, 0, 0, bm.bmWidth, bm.bmHeight, hdcSource, 0, 0, SRCCOPY)); This assumes that hdcSource is a memory DC holding the source image, and hdcMask is a memory DC holding a monochrome bitmap of the same size (so both are 32x32, but the source is 4 bit color, while the target is 1bit monochrome). However, this seems to fail for me when the source is 32 bit color + alpha. Instead of getting a monochrome bitmap in hdcMask, I get a mask that is all black. No bits get set to white (1). Whereas this works for the 4bit color source. My search-foo is failing, as I cannot seem to find any references to this particular problem. I have isolated that this is indeed the issue in my code: i.e. if I use a source bitmap that is 16 color (4bit), it works; if I use a 32 bit image, it produces the all-black mask. Is there an alternate method I should be using in the case of 32 bit color images? Is there an issue with the alpha channel that overrides the normal behavior of the above technique? Thanks for any help you may have to offer! ADDENDUM: I am still unable to find a technique that creates a valid monochrome bitmap for my GDI+ produced source bitmap. I have somewhat alleviated my particular issue by simply not generating a monochrome bitmask at all, and instead I'm using TransparentBlt(), which seems to get it right (but I don't know what they're doing internally that's any different that allows them to correctly mask the image). It might be useful to have a really good, working function: HBITMAP CreateTransparencyMask(HDC hdc, HBITMAP hSource, COLORREF crTransparency); Where it always creates a valid transparency mask, regardless of the color depth of hSource. Ideas?

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  • Starting and stopping firefox from c#

    - by Lucas Meijer
    When I start /Applications/Firefox.app/Contents/MacOS/firefox-bin on MacOSX using Process.Start() using Mono, the id of the process that gets returned does not match the process that firefox ends up running under. It looks like firefox quickly decides to start another process, and kill the current one. This makes it difficult to stop firefox, and to detect if it is still running. I've tried starting firefox using the -no-remote flag, to no avail. Is there a way to start firefox in such a way that it doesn't do this "I'll quickly make a new process for you" dance? The situation can somewhat be detected by making sure Firefox keeps on running for at least 3 seconds after its start, and when it does not, scan for other firefox processes. However, this technique is shaky at best, as on slow days it might take a bit more than 3 seconds, and then all tests depending on this behaviour fail. It turns out, that this behaviour only happens when asking firefox to start a specific profile using -P MyProfile. (Which I need to do, as I need to start firefox with specific proxyserver settings) If I start firefox "normally" it does stick to its process.

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  • Why do case class companion objects extend FunctionN?

    - by retronym
    When you create a case class, the compiler creates a corresponding companion object with a few of the case class goodies: an apply factory method matching the primary constructor, equals, hashCode, and copy. Somewhat oddly, this generated object extends FunctionN. scala> case class A(a: Int) defined class A scala> A: (Int => A) res0: (Int) => A = <function1> This is only the case if: There is no manually defined companion object There is exactly one parameter list There are no type arguments The case class isn't abstract. Seems like this was added about two years ago. The latest incarnation is here. Does anyone use this, or know why it was added? It increases the size of the generated bytecode a little with static forwarder methods, and shows up in the #toString() method of the companion objects: scala> case class A() defined class A scala> A.toString res12: java.lang.String = <function0>

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  • MySQL LEFT JOIN, INNER JOIN etc, complicated query, PHP + MySQL for a forum

    - by Sven Eriksson
    So I've got a little forum I'm trying to get data for, there are 4 tables, forum, forum_posts, forum_threads and users. What i'm trying to do is to get the latest post for each forum and giving the user a sneak peek of that post, i want to get the number of posts and number of threads in each forum aswell. Also, i want to do this in one query. So here's what i came up with: SELECT lfx_forum_posts.*, lfx_forum.*, COUNT(lfx_forum_posts.pid) as posts_count, lfx_users.username, lfx_users.uid, lfx_forum_threads.tid, lfx_forum_threads.parent_forum as t_parent, lfx_forum_threads.text as t_text, COUNT(lfx_forum_threads.tid) as thread_count FROM lfx_forum LEFT JOIN (lfx_forum_threads INNER JOIN (lfx_forum_posts INNER JOIN lfx_users ON lfx_users.uid = lfx_forum_posts.author) ON lfx_forum_threads.tid = lfx_forum_posts.parent_thread AND lfx_forum_posts.pid = (SELECT MAX(lfx_forum_posts.pid) FROM lfx_forum_posts WHERE lfx_forum_posts.parent_forum = lfx_forum.fid GROUP BY lfx_forum_posts.parent_forum) ) ON lfx_forum.fid = lfx_forum_posts.parent_forum GROUP BY lfx_forum.fid ORDER BY lfx_forum.fid ASC This get the latest post in each forum and gives me a sneakpeek of it, the problem is that lfx_forum_posts.pid = (SELECT MAX(lfx_forum_posts.pid) FROM lfx_forum_posts WHERE lfx_forum_posts.parent_forum = lfx_forum.fid GROUP BY lfx_forum_posts.parent_forum) Makes my COUNT(lfx_forum_posts.pid) go to one (aswell as the COUNT(lfx_forum_threads.tid) which isn't how i would like it to work. My question is: is there some somewhat easy way to make it show the correct number and at the same time fetch the correct post info (the latest one that is)? If something is unclear please tell and i'll try to explain my issue further, it's my first time posting something here.

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  • Password hashing, salt and storage of hashed values

    - by Jonathan Leffler
    Suppose you were at liberty to decide how hashed passwords were to be stored in a DBMS. Are there obvious weaknesses in a scheme like this one? To create the hash value stored in the DBMS, take: A value that is unique to the DBMS server instance as part of the salt, And the username as a second part of the salt, And create the concatenation of the salt with the actual password, And hash the whole string using the SHA-256 algorithm, And store the result in the DBMS. This would mean that anyone wanting to come up with a collision should have to do the work separately for each user name and each DBMS server instance separately. I'd plan to keep the actual hash mechanism somewhat flexible to allow for the use of the new NIST standard hash algorithm (SHA-3) that is still being worked on. The 'value that is unique to the DBMS server instance' need not be secret - though it wouldn't be divulged casually. The intention is to ensure that if someone uses the same password in different DBMS server instances, the recorded hashes would be different. Likewise, the user name would not be secret - just the password proper. Would there be any advantage to having the password first and the user name and 'unique value' second, or any other permutation of the three sources of data? Or what about interleaving the strings? Do I need to add (and record) a random salt value (per password) as well as the information above? (Advantage: the user can re-use a password and still, probably, get a different hash recorded in the database. Disadvantage: the salt has to be recorded. I suspect the advantage considerably outweighs the disadvantage.) There are quite a lot of related SO questions - this list is unlikely to be comprehensive: Encrypting/Hashing plain text passwords in database Secure hash and salt for PHP passwords The necessity of hiding the salt for a hash Clients-side MD5 hash with time salt Simple password encryption Salt generation and Open Source software I think that the answers to these questions support my algorithm (though if you simply use a random salt, then the 'unique value per server' and username components are less important).

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  • ASP.NET, C#: timeout when trying to Transaction.Commit() to database; potential deadlock?

    - by user1843921
    I have a web page that has coding structured somewhat as follows: SqlConnection conX =new SqlConnection(blablabla); conX.Open(); SqlTransaction tran=conX.BeginTransaction(); try{ SqlCommand cmdInsert =new SqlCommand("INSERT INTO Table1(ColX,ColY) VALUES @x,@y",conX); cmdInsert.Transaction=tran; cmdInsert.ExecuteNonQuery(); SqlCommand cmdSelect=new SqlCOmmand("SELECT * FROM Table1",conX); cmdSelect.Transaction=tran; SqlDataReader dtr=cmdSelect.ExecuteReader(); //read stuff from dtr dtr.Close(); cmdInsert=new SqlCommand("UPDATE Table2 set ColA=@a",conX); cmdInsert.Transaction=tran; cmdInsert.ExecuteNonQuery(); //display MiscMessage tran.Commit(); //display SuccessMessage } catch(Exception x) { tran.Rollback(); //display x.Message } finally { conX.Close(); } So, everything seems to work until MiscMessage. Then, after a while (maybe 15-ish seconds?) x.Message pops up, saying that: "Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding." So something wrong with my trans.Commit()? The database is not updated so I assume the trans.Rollback works... I have read that deadlocks can cause timeouts...is this problem cause by my SELECT statement selecting from Table1, which is being used by the first INSERT statement? If so, what should I do? If that ain't the problem, what is?

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  • Thread-safe data structure design

    - by Inso Reiges
    Hello, I have to design a data structure that is to be used in a multi-threaded environment. The basic API is simple: insert element, remove element, retrieve element, check that element exists. The structure's implementation uses implicit locking to guarantee the atomicity of a single API call. After i implemented this it became apparent, that what i really need is atomicity across several API calls. For example if a caller needs to check the existence of an element before trying to insert it he can't do that atomically even if each single API call is atomic: if(!data_structure.exists(element)) { data_structure.insert(element); } The example is somewhat awkward, but the basic point is that we can't trust the result of "exists" call anymore after we return from atomic context (the generated assembly clearly shows a minor chance of context switch between the two calls). What i currently have in mind to solve this is exposing the lock through the data structure's public API. This way clients will have to explicitly lock things, but at least they won't have to create their own locks. Is there a better commonly-known solution to these kinds of problems? And as long as we're at it, can you advise some good literature on thread-safe design? EDIT: I have a better example. Suppose that element retrieval returns either a reference or a pointer to the stored element and not it's copy. How can a caller be protected to safely use this pointer\reference after the call returns? If you think that not returning copies is a problem, then think about deep copies, i.e. objects that should also copy another objects they point to internally. Thank you.

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  • Segmentation in Linux : Segmentation & Paging are redundant?

    - by claws
    Hello, I'm reading "Understanding Linux Kernel". This is the snippet that explains how Linux uses Segmentation which I didn't understand. Segmentation has been included in 80 x 86 microprocessors to encourage programmers to split their applications into logically related entities, such as subroutines or global and local data areas. However, Linux uses segmentation in a very limited way. In fact, segmentation and paging are somewhat redundant, because both can be used to separate the physical address spaces of processes: segmentation can assign a different linear address space to each process, while paging can map the same linear address space into different physical address spaces. Linux prefers paging to segmentation for the following reasons: Memory management is simpler when all processes use the same segment register values that is, when they share the same set of linear addresses. One of the design objectives of Linux is portability to a wide range of architectures; RISC architectures in particular have limited support for segmentation. All Linux processes running in User Mode use the same pair of segments to address instructions and data. These segments are called user code segment and user data segment , respectively. Similarly, all Linux processes running in Kernel Mode use the same pair of segments to address instructions and data: they are called kernel code segment and kernel data segment , respectively. Table 2-3 shows the values of the Segment Descriptor fields for these four crucial segments. I'm unable to understand 1st and last paragraph.

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  • The fastest way to iterate through a collection of objects

    - by Trev
    Hello all, First to give you some background: I have some research code which performs a Monte Carlo simulation, essential what happens is I iterate through a collection of objects, compute a number of vectors from their surface then for each vector I iterate through the collection of objects again to see if the vector hits another object (similar to ray tracing). The pseudo code would look something like this for each object { for a number of vectors { do some computations for each object { check if vector intersects } } } As the number of objects can be quite large and the amount of rays is even larger I thought it would be wise to optimise how I iterate through the collection of objects. I created some test code which tests arrays, lists and vectors and for my first test cases found that vectors iterators were around twice as fast as arrays however when I implemented a vector in my code in was somewhat slower than the array I was using before. So I went back to the test code and increased the complexity of the object function each loop was calling (a dummy function equivalent to 'check if vector intersects') and I found that when the complexity of the function increases the execution time gap between arrays and vectors reduces until eventually the array was quicker. Does anyone know why this occurs? It seems strange that execution time inside the loop should effect the outer loop run time.

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  • When to choose which machine learning classifier?

    - by LM
    Suppose I'm working on some classification problem. (Fraud detection and comment spam are two problems I'm working on right now, but I'm curious about any classification task in general.) How do I know which classifier I should use? (Decision tree, SVM, Bayesian, logistic regression, etc.) In which cases is one of them the "natural" first choice, and what are the principles for choosing that one? Examples of the type of answers I'm looking for (from Manning et al.'s "Introduction to Information Retrieval book": http://nlp.stanford.edu/IR-book/html/htmledition/choosing-what-kind-of-classifier-to-use-1.html): a. If your data is labeled, but you only have a limited amount, you should use a classifier with high bias (for example, Naive Bayes). [I'm guessing this is because a higher-bias classifier will have lower variance, which is good because of the small amount of data.] b. If you have a ton of data, then the classifier doesn't really matter so much, so you should probably just choose a classifier with good scalability. What are other guidelines? Even answers like "if you'll have to explain your model to some upper management person, then maybe you should use a decision tree, since the decision rules are fairly transparent" are good. I care less about implementation/library issues, though. Also, for a somewhat separate question, besides standard Bayesian classifiers, are there 'standard state-of-the-art' methods for comment spam detection (as opposed to email spam)? [Not sure if stackoverflow is the best place to ask this question, since it's more machine learning than actual programming -- if not, any suggestions for where else?]

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  • Web Shop Schema - Document Db

    - by Maxem
    I'd like to evaluate a document db, probably mongo db in an ASP.Net MVC web shop. A little reasoning at the beginning: There are about 2 million products. The product model would be pretty bad for rdbms as there'd be many different kinds of products with unique attributes. For example, there'd be books which have isbn, authors, title, pages etc as well as dvds with play time, directors, artists etc and quite a few more types. In the end, I'd have about 9 different products with a combined column count (counting common columns like title only once) of about 70 to 100 whereas each individual product has 15 columns at most. The three commonly used ways in RDBMS would be: EAV model which would have pretty bad performance characteristics and would make it either impractical or perform even worse if I'd like to display the author of a book in a list of different products (think start page, recommended products etc.). Ignore the column count and put it all in the product table: Although I deal with somewhat bigger databases (row wise), I don't have any experience with tables with more than 20 columns as far as performance is concered but I guess 100 columns would have some implications. Create a table for each product type: I personally don't like this approach as it complicates everything else. C# Driver / Classes: I'd like to use the NoRM driver and so far I think i'll try to create a product dto that contains all properties (grouped within detail classes like book details, except for those properties that should be displayed on list views etc.). In the app I'll use BookBehavior / DvdBehaviour which are wrappers around a product dto but only expose the revelent Properties. My questions now: Are my performance concerns with the many columns approach valid? Did I overlook something and there is a much better way to do it in an RDBMS? Is MongoDb on Windows stable enough? Does my approach with different behaviour wrappers make sense?

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