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  • Base 128 or 256 Encoding for the Binary Lexical Octet Adhoc Transport Protocol?

    - by Randolpho
    I'm in the process of implementing a network driver for the Binary Lexical Octet Adhoc Transport (BLOAT) protocols in the hopes of replacing the TCP/UDP/IP stack with a much more flexible XML structure. BLOAT is detailed in RFC 3252, so if you're unfamiliar with the protocol I highly recommend you read the entire RFC before providing any comments. Don't worry, it's short and sweet; you might even enjoy it. Anyway, my problem is this: BLOAT requires that the payload be Base64 encoded which doesn't make sense to me. I mean, sure, it's the internet standard for binary payloads, but there are better, more efficient encodings available: Base128 and Base256, for example. That the RFC requires Base64 and doesn't allow for any other payload encoding really bothers me. To that end, I'm considering a small optional change to the protocol. Embrace and extend, right? Anyway, I'd like to modify the payload element to accept an encoding attribute, which can extend the encoding to Base128 or Base256, or even to other encodings I can't conceive of at the moment. If the encoding attribute isn't present, Base64 would be assumed. So my question is this: should I? I mean, BLOAT is an accepted standard, even if it isn't exactly omnipresent. If I make this change, will there be compatibility issues? I don't foresee any, but perhaps you, oh great Stack Overflow Community, can? If I do implement this change, should I contact the original RFC author? Should I offer a supplemental RFC?

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  • Subset a data.frame by list and apply function on each part, by rows

    - by aL3xa
    This may seem as a typical plyr problem, but I have something different in mind. Here's the function that I want to optimize (skip the for loop). # dummy data set.seed(1985) lst <- list(a=1:10, b=11:15, c=16:20) m <- matrix(round(runif(200, 1, 7)), 10) m <- as.data.frame(m) dfsub <- function(dt, lst, fun) { # check whether dt is `data.frame` stopifnot (is.data.frame(dt)) # check if vectors in lst are "whole" / integer # vector elements should be column indexes is.wholenumber <- function(x, tol = .Machine$double.eps^0.5) abs(x - round(x)) < tol # fall if any non-integers in list idx <- rapply(lst, is.wholenumber) stopifnot(idx) # check for list length stopifnot(ncol(dt) == length(idx)) # subset the data subs <- list() for (i in 1:length(lst)) { # apply function on each part, by row subs[[i]] <- apply(dt[ , lst[[i]]], 1, fun) } # preserve names names(subs) <- names(lst) # convert to data.frame subs <- as.data.frame(subs) # guess what =) return(subs) } And now a short demonstration... actually, I'm about to explain what I primarily intended to do. I wanted to subset a data.frame by vectors gathered in list object. Since this is a part of code from a function that accompanies data manipulation in psychological research, you can consider m as a results from personality questionnaire (10 subjects, 20 vars). Vectors in list hold column indexes that define questionnaire subscales (e.g. personality traits). Each subscale is defined by several items (columns in data.frame). If we presuppose that the score on each subscale is nothing more than sum (or some other function) of row values (results on that part of questionnaire for each subject), you could run: > dfsub(m, lst, sum) a b c 1 46 20 24 2 41 24 21 3 41 13 12 4 37 14 18 5 57 18 25 6 27 18 18 7 28 17 20 8 31 18 23 9 38 14 15 10 41 14 22 I took a glance at this function and I must admit that this little loop isn't spoiling the code at all... BUT, if there's an easier/efficient way of doing this, please, let me know!

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  • Eclipse RAP - Firefox doesn't forget session

    - by Fritz H
    We've got an Eclipse RAP application that's behaving a bit strangely in Firefox - two distinct problems. When you browse around, you can click on a button in one part of the system. This opens a popup window like so: IWorkbenchBrowserSupport bs; bs = PlatformUI.getWorkbench().getBrowserSupport(); int style = IWorkbenchBrowserSupport.AS_EXTERNAL; IWebBrowser b = bs.createBrowser(style, getRandomID(), "Hello world", ""); b.openURL(new URL(...)); where the URL is another servlet in the application. This servlet is in the same runtime, but has nothing to do with RAP - it takes a binary blob from in-memory storage and dumps it in the output stream. Problem 1: This causes the HTTP session to die in firefox, and shows the "session expired" RAP error page with a link to restart the session. Problem 2: Now, when you click on the link to restart the session, it shows the application's dialog again, but the session expired error is shown again the moment you do anything. This prevents the user from using the system again, unless Firefox is closed down completely and restarted. A quick peek with FireBug reveals that the JSESSIONID passed by Firefox does not change. Has anyone seen this before?

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  • Django custom managers - how do I return only objects created by the logged-in user?

    - by Tom Tom
    I want to overwrite the custom objects model manager to only return objects a specific user created. Admin users should still return all objects using the objects model manager. Now I have found an approach that could work. They propose to create your own middleware looking like this: #### myproject/middleware/threadlocals.py try: from threading import local except ImportError: # Python 2.3 compatibility from django.utils._threading_local import local _thread_locals = local() def get_current_user(): return getattr(_thread_locals, 'user', None) class ThreadLocals(object): """Middleware that gets various objects from the request object and saves them in thread local storage.""" def process_request(self, request): _thread_locals.user = getattr(request, 'user', None) #### end And in the Custom manager you could call the get_current_user() method to return only objects a specific user created. class UserContactManager(models.Manager): def get_query_set(self): return super(UserContactManager, self).get_query_set().filter(creator=get_current_user()) Is this a good approach to this use-case? Will this work? Or is this like "using a sledgehammer to crack a nut" ? ;-) Just using: Contact.objects.filter(created_by= user) in each view doesn`t look very neat to me. EDIT Do not use this middleware approach !!! use the approach stated by Jack M. below After a while of testing this approach behaved pretty strange and with this approach you mix up a global-state with a current request. Use the approach presented below. It is really easy and no need to hack around with the middleware. create a custom manager in your model with a function that expects the current user or any other user as an input. #in your models.py class HourRecordManager(models.Manager): def for_user(self, user): return self.get_query_set().filter(created_by=user) class HourRecord(models.Model): #Managers objects = HourRecordManager() #in vour view you can call the manager like this and get returned only the objects from the currently logged-in user. hr_set = HourRecord.objects.for_user(request.user)

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  • Javascript functional inheritance with prototypes

    - by cdmckay
    In Douglas Crockford's JavaScript: The Good Parts he recommends that we use functional inheritance. Here's an example: var mammal = function(spec, my) { var that = {}; my = my || {}; // Protected my.clearThroat = function() { return "Ahem"; }; that.getName = function() { return spec.name; }; that.says = function() { return my.clearThroat() + ' ' + spec.saying || ''; }; return that; } var cat = function(spec, my) { var that = {}; my = my || {}; spec.saying = spec.saying || 'meow'; that = mammal(spec, my); that.purr = function() { return my.clearThroat() + " purr"; }; that.getName = function() { return that.says() + ' ' + spec.name + ' ' + that.says(); }; return that; }; var kitty = cat({name: "Fluffy"}); The main issue I have with this is that every time I make a mammal or cat the JavaScript interpreter has to re-compile all the functions in it. That is, you don't get to share the code between instances. My question is: how do I make this code more efficient? For example, if I was making thousands of cat objects, what is the best way to modify this pattern to take advantage of the prototype object?

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  • Nonblocking Tcp server

    - by hoodoos
    It's not a question really, i'm just looking for some guidelines :) I'm currently writing some abstract tcp server which should use as low number of threads as it can. Currently it works this way. I have a thread doing listening and some worker threads. Listener thread is just sits and wait for clients to connect I expect to have a single listener thread per server instance. Worker threads are doing all read/write/processing job on clients socket. So my problem is in building efficient worker process. And I came to some problem I can't really solve yet. Worker code is something like that(code is really simple just to show a place where i have my problem): List<Socket> readSockets = new List<Socket>(); List<Socket> writeSockets = new List<Socket>(); List<Socket> errorSockets = new List<Socket>(); while( true ){ Socket.Select( readSockets, writeSockets, errorSockets, 10 ); foreach( readSocket in readSockets ){ // do reading here } foreach( writeSocket in writeSockets ){ // do writing here } // POINT2 and here's the problem i will describe below } it works all smothly accept for 100% CPU utilization because of while loop being cycling all over again, if I have my clients doing send-receive-disconnect routine it's not that painful, but if I try to keep alive doing send-receive-send-receive all over again it really eats up all CPU. So my first idea was to put a sleep there, I check if all sockets have their data send and then putting Thread.Sleep in POINT2 just for 10ms, but this 10ms later on produces a huge delay of that 10ms when I want to receive next command from client socket.. For example if I don't try to "keep alive" commands are being executed within 10-15ms and with keep alive it becomes worse by atleast 10ms :( Maybe it's just a poor architecture? What can be done so my processor won't get 100% utilization and my server to react on something appear in client socket as soon as possible? Maybe somebody can point a good example of nonblocking server and architecture it should maintain?

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  • Java EE suitablity for a social network using Cassandra datastore ??

    - by Marcos
    We are in the process of making some important technology decisions for a social networking application. We're planning to have Cassandra(a NoSQL database to support efficient data storage). We would be using Hector(a Java client) to interact with Cassandra. 1.) Would Java EE be a good choice over PHP for a social networking application in terms of performance, scalabilty & complexities? 2.) Another possible implementation strategy, Is it suitable to have backend alone in Java and rest in PHP? 3.) What differences(as compared to PHP) it makes in terms of costs at various stages of application development, deployment and maintenance ? 4.) What are the things to keep in mind as we move along with Java development& deployment(as we are relatively new to the Java background) ? 5.) If you could list some major production deployments of similar type(social network) applications in Java. Thank you!

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  • Assistance with building an inverted-index

    - by tipu
    It's part of an information retrieval thing I'm doing for school. The plan is to create a hashmap of words using the the first two letters of the word as a key and any words with the two letters saved as a string value. So, hashmap["ba"] = "bad barley base" Once I'm done tokenizing a line I take that hashmap, serialize it, and append it to the text file named after the key. The idea is that if I take my data and spread it over hundreds of files I'll lessen the time it takes to fulfill a search by lessening the density of each file. The problem I am running into is when I'm making 100+ files in each run it happens to choke on creating a few files for whatever reason and so those entries are empty. Is there any way to make this more efficient? Is it worth continuing this, or should I abandon it? I'd like to mention I'm using PHP. The two languages I know relatively intimately are PHP and Java. I chose PHP because the front end will be very simple to do and I will be able to add features like autocompletion/suggested search without a problem. I also see no benefit in using Java. Any help is appreciated, thanks.

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  • Updating the value of a math equation with YUI slider and simple radio buttons.

    - by dj lewis
    I have a form that is used to show a price for a product. I have a YUI slider setup that changes the price, and it works perfectly. Now I'm trying to add in radio buttons that also should update that same price value. The price displayed should take into account all 3 fields, and update dynamically as any are updated. This is the code I have, but I don't have any radio buttons for cpanelPrice yet as I'm still just trying to get the IPs to work. <script type="text/javascript"> (function() { var Event = YAHOO.util.Event, Dom = YAHOO.util.Dom, lang = YAHOO.lang, slider, bg="slider-bg", thumb="slider-thumb", orderlink="order-link", monthlyprice="monthly-price", dram="ram", stor="storage",dcpu="cpu",bandw="bandwidth",slid="sliderbg" // The slider can move 0 pixels up var topConstraint = 0; // The slider can move 200 pixels down var bottomConstraint = 585; // Custom scale factor for converting the pixel offset into a real value var scaleFactor = 1; // The amount the slider moves when the value is changed with the arrow // keys var keyIncrement = 65; var tickSize = 65; Event.onDOMReady(function() { slider = YAHOO.widget.Slider.getHorizSlider(bg, thumb, topConstraint, bottomConstraint, tickSize); slider.setValue(1, true); slider.animate = true; slider.getRealValue = function() { return Math.round(this.getValue() * scaleFactor); } slider.subscribe("change", function(offsetFromStart) { var ordnode = Dom.get(orderlink); var prinode = Dom.get(monthlyprice); var ramnode = Dom.get(dram); var stornode = Dom.get(stor); var cpunode = Dom.get(dcpu); var bwnode = Dom.get(bandw); var slidnode = Dom.get(slid); var actualValue = slider.getRealValue(); if (actualValue < 0) { var actualValue = 0; } if (actualValue > -1 && actualValue < 5) { basePrice = 15; var pid = "7"; var ram = "128 MB"; stornode.innerHTML = "5"; cpunode.innerHTML = ".5"; bwnode.innerHTML = "50"; slidnode.innerHTML = "<img src=\"/images/sliderbg1.png\" alt=\"\" />"; } else if (actualValue > 60 && actualValue < 70) { basePrice = 25; var pid = "8"; var ram = "256 MB"; stornode.innerHTML = "10"; cpunode.innerHTML = ".5"; bwnode.innerHTML = "100"; slidnode.innerHTML = "<img src=\"/images/sliderbg2.png\" alt=\"\" />"; } else if (actualValue > 125 && actualValue < 135) { basePrice = 40; var pid = "9"; var ram = "512 MB"; stornode.innerHTML = "20"; cpunode.innerHTML = "1"; bwnode.innerHTML = "200"; slidnode.innerHTML = "<img src=\"/images/sliderbg3.png\" alt=\"\" />"; } else if (actualValue > 190 && actualValue < 200) { basePrice = 60; var pid = "10"; var ram = "1 GB"; stornode.innerHTML = "40"; cpunode.innerHTML = "1"; bwnode.innerHTML = "400"; slidnode.innerHTML = "<img src=\"/images/sliderbg4.png\" alt=\"\" />"; } else if (actualValue> 255 && actualValue < 265) { basePrice = 80; var pid = "11"; var ram = "1.5 GB"; stornode.innerHTML = "60"; cpunode.innerHTML = "1"; bwnode.innerHTML = "600"; slidnode.innerHTML = "<img src=\"/images/sliderbg5.png\" alt=\"\" />"; } else if (actualValue > 320 && actualValue < 330) { basePrice = 110; var pid = "12"; var ram = "2 GB"; stornode.innerHTML = "80"; cpunode.innerHTML = "2"; bwnode.innerHTML = "800"; slidnode.innerHTML = "<img src=\"/images/sliderbg6.png\" alt=\"\" />"; } else if (actualValue > 385 && actualValue < 395) { basePrice = 140; var pid = "13"; var ram = "2.5 GB"; stornode.innerHTML = "100"; cpunode.innerHTML = "2"; bwnode.innerHTML = "1000"; slidnode.innerHTML = "<img src=\"/images/sliderbg7.png\" alt=\"\" />"; } else if (actualValue > 450 && actualValue < 460) { basePrice = 170; var pid = "14"; var ram = "3 GB"; stornode.innerHTML = "120"; cpunode.innerHTML = "3"; bwnode.innerHTML = "1200"; slidnode.innerHTML = "<img src=\"/images/sliderbg8.png\" alt=\"\" />"; } else if (actualValue > 515 && actualValue < 525) { basePrice = 200; var pid = "15"; var ram = "3.5 GB"; stornode.innerHTML = "140"; cpunode.innerHTML = "3"; bwnode.innerHTML = "1400"; slidnode.innerHTML = "<img src=\"/images/sliderbg9.png\" alt=\"\" />"; } else if (actualValue > 580 && actualValue < 590) { basePrice = 240; var pid = "16"; var ram = "4 GB"; stornode.innerHTML = "160"; cpunode.innerHTML = "4"; bwnode.innerHTML = "1600"; slidnode.innerHTML = "<img src=\"/images/sliderbg10.png\" alt=\"\" />"; } // Setup the order link ordnode.innerHTML = "<a href=\"https://account.hostingbeast.com/cart.php?a=add&pid=" + pid + "\"><img src=\"/images/blank.gif\" alt=\"Order VPS Hosting\" height=\"100\" width=\"100\" /></a>"; ramnode.innerHTML = ram; ipPrice = 0; function setIpPrice(ips) { ipPrice = ips.value; } cpanelPrice = 0; prinode.innerHTML = basePrice + ipPrice + cpanelPrice; }); // Use setValue to reset the value to white: Event.on("putval", "click", function(e) { slider.setValue(100, false); //false here means to animate if possible }); setTimeout(function () { slider.setValue(10); },0); }); })(); </script> <div style="width: 649px; margin:auto"> <span id="sliderbg"></span> <div class="yui-skin-sam"> <div id="slider-bg" class="yui-h-slider" tabindex="-1"> <div id="slider-thumb" class="yui-slider-thumb"><img src="/images/thumb-bar.png"></div> </div> </div> </div> <div class="vpsdetails"> <div id="vpsprod"><span id="cpu"></span></div> <div id="vpsram"><span id="ram"></span></div> <div id="vpsstor"><span id="storage"></span> GB</div> <div id="vpsbw"><span id="bandwidth"></span> GB</div> <div id="slideprice">$ <span id="monthly-price"></span></div> </div> <input type="radio" name="ips" value="2" onclick="setIpPrice(this.value - 2 * 2);" checked="checked" /> 2 <input type="radio" name="ips" value="4" onclick="setIpPrice(this.value - 2 * 2);" /> 4

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  • When should one use the following: Amazon EC2, Google App Engine, Microsoft Azure and Salesforce.com

    - by vicky21
    I am asking this in very general sense. Both from cloud provider and cloud consumer's perspective. Also the question is not for any specific kind of application (in fact the intention is to know which type of applications/domains can fit into which of the cloud slab -SaaS PaaS IaaS). My understanding so far is: IaaS: Raw Hardware (Processors, Networks, Storage). PaaS: OS, System Softwares, Development Framework, Virtual Machines. SaaS: Software Applications. It would be great if Stackoverflower's can share their understanding and experiences of cloud computing concept. EDIT: Ok, I will put it in more specific way - Amazon EC2: You don't have control over hardware layer. But you can take your choice of OS image, Dev Framework (.NET, J2EE, LAMP) and Application and put it on EC2 hardware. Can you deploy an applications built with Google App Engine or Azure on EC2? Google App Engine: You don't have control over hardware and OS and you get a specific Dev Framework to build your application. Can you take any existing Java or Python application and port it to GAE? Or vice versa, can applications that were built on GAE be taken out of GAE and ported to any Application Server like Websphere or Weblogic? Azure: You don't have control over hardware and OS and you get a specific Dev Framework to build your application. Can you take any existing .NET application and port it to Azure? Or vice versa, can applications that were built on Azure be taken out of Azure and ported to any Application Server like Biztalk?

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  • Java parsing XML document gives "Content not allowed in prolog." error

    - by thechiman
    I am writing a program in Java that takes a custom XML file and parses it. I'm using the XML file for storage. I am getting the following error in Eclipse. [Fatal Error] :1:1: Content is not allowed in prolog. org.xml.sax.SAXParseException: Content is not allowed in prolog. at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:239) at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:283 ) at javax.xml.parsers.DocumentBuilder.parse(DocumentBuilder.java:208) at me.ericso.psusoc.RequirementSatisfier.parseXML(RequirementSatisfier.java:61) at me.ericso.psusoc.RequirementSatisfier.getCourses(RequirementSatisfier.java:35) at me.ericso.psusoc.programs.RequirementSatisfierProgram.main(RequirementSatisfierProgram.java:23 ) The beginning of the XML file is included: <?xml version="1.0" ?> <PSU> <Major id="IST"> <name>Information Science and Technology</name> <degree>B.S.</degree> <option> Information Systems: Design and Development Option</option> <requirements> <firstlevel type="General_Education" credits="45"> <component type="Writing_Speaking">GWS</component> <component type="Quantification">GQ</component> The program is able to read in the XML file but when I call DocumentBuilder.parse(XMLFile) to get a parsed org.w3c.dom.Document, I get the error above. It doesn't seem to me that I have invalid content in the prolog of my XML file. I can't figure out what is wrong. Please help. Thanks.

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  • Problem with messages framework in Django 1.2

    - by Konstantin
    Hello! I'm running Django 1.2 beta and trying out the new feature: message framework. http://docs.djangoproject.com/en/dev/ref/contrib/messages/ Everything seems to work, but when I try to output the messages, I get nothing. Seems that messages variable is empty. I double checked all the settings, they seem to be just like in the manual. What could be wrong? settings.py MIDDLEWARE_CLASSES = ( 'django.middleware.common.CommonMiddleware', 'django.contrib.sessions.middleware.SessionMiddleware', 'django.contrib.messages.middleware.MessageMiddleware', #send messages to users 'django.middleware.locale.LocaleMiddleware', 'django.contrib.auth.middleware.AuthenticationMiddleware', #debug tool 'debug_toolbar.middleware.DebugToolbarMiddleware', ) TEMPLATE_CONTEXT_PROCESSORS = ( 'django.contrib.messages.context_processors.messages', #send messages to users 'django.core.context_processors.auth', ) #Store messages in sessions MESSAGE_STORAGE = 'django.contrib.messages.storage.session.SessionStorage'; INSTALLED_APPS = ( 'django.contrib.auth', 'django.contrib.contenttypes', 'django.contrib.sessions', #'django.contrib.sites', 'django.contrib.admin', 'django.contrib.messages', 'debug_toolbar', #my apps #... ) views.py def myview(request): from django.contrib import messages messages.error(request, 'error test'); messages.success(request, 'success test'); return render_to_response('mytemplate.html', locals()); mytemplate.html {% for message in messages %} {{ message }}<br /> {% endfor %} In template nothing is outputted.

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  • Speed up bitstring/bit operations in Python?

    - by Xavier Ho
    I wrote a prime number generator using Sieve of Eratosthenes and Python 3.1. The code runs correctly and gracefully at 0.32 seconds on ideone.com to generate prime numbers up to 1,000,000. # from bitstring import BitString def prime_numbers(limit=1000000): '''Prime number generator. Yields the series 2, 3, 5, 7, 11, 13, 17, 19, 23, 29 ... using Sieve of Eratosthenes. ''' yield 2 sub_limit = int(limit**0.5) flags = [False, False] + [True] * (limit - 2) # flags = BitString(limit) # Step through all the odd numbers for i in range(3, limit, 2): if flags[i] is False: # if flags[i] is True: continue yield i # Exclude further multiples of the current prime number if i <= sub_limit: for j in range(i*3, limit, i<<1): flags[j] = False # flags[j] = True The problem is, I run out of memory when I try to generate numbers up to 1,000,000,000. flags = [False, False] + [True] * (limit - 2) MemoryError As you can imagine, allocating 1 billion boolean values (1 byte 4 or 8 bytes (see comment) each in Python) is really not feasible, so I looked into bitstring. I figured, using 1 bit for each flag would be much more memory-efficient. However, the program's performance dropped drastically - 24 seconds runtime, for prime number up to 1,000,000. This is probably due to the internal implementation of bitstring. You can comment/uncomment the three lines to see what I changed to use BitString, as the code snippet above. My question is, is there a way to speed up my program, with or without bitstring?

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  • Beginner video capture and processing/Camera selection

    - by mattbauch
    I'll soon be undertaking a research project in real-time event recognition but have no experience with the programming aspect of video capture (I'm an upperclassman undergraduate in computer engineering). I want to start off on the right foot so advice from anyone with experience would be great. The ultimate goal is to track events such as a person standing up/sitting down, entering/leaving a room, possibly even shrugging/slumping in posture, etc. from a security camera-like vantage point. First of all, which cameras/companies would you recommend? I'm looking to spend ~$100, more if necessary but not much. Great resolution isn't a must, but is desirable if affordable. What about IP network cameras vs. a USB type webcam? Webcams are less expensive, but IP cameras seem like they'd be much less work to deal with in software. What features should I look for in the camera? Once I've selected a camera, what does converting its output to a series of RGB bitmaps entail? I've never dealt with video encoding/decoding so a starting point or a tutorial that will guide me up to this point would be great if anyone has suggestions. Finally, what is the best (least complicated/most efficient) way to display video from the camera plus my own superimposed images (boxes around events in progress, for instance) in a GUI application? I can work on any operating system in any language. I have some experience with win32 GUIs and Java GUIs. The focus of the project is on the algorithm and so I'm trying to get the video capture/display portion of the app done cleanly and quickly. Thanks for any responses!!

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  • To Ajax or Not to Ajax a listing page

    - by kaivalya
    Here i am talking about product listing pages where there are multiple filters that filter the list of products appearing on the page like product types, categories price range etc. I have done such pages using both ajax and no ajax way in the past. What I like about using ajax in such page is that, when filters are selected I only update the section that contains the product list. There is no need to refresh the whole page which could end up re-loading the images on top bar, banners etc and slow down the user performance. Ajax way in my opinion becomes more compact and responsive from user experience. Down side for ajax route for me is; since filter states are not maintained in the URL I end up maintaining them on the server. This becomes complicated if I want to handle multi window scenarios and it is also costly to maintain such state on server memory for each session. Not using ajax and simply keeping all filter values on url and refreshing the page is quite simple but the luxury of refreshing only the pane that really needs to be refreshed is lost. Lately I am seeing a lot of large scale e-commerce sites that are using non-ajax approach on their listing pages and this is making me question one more time if it might be more efficient to build non-ajax listing make due to the long term maintenance ease and sacrifice a little bit from user experience. I am about to start implementing a new listing page for a product which I have the flexibility to go either way and I would appreciate your inputs.

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  • Is Berkeley DB XML a viable database backend?

    - by w00t
    Apparently, BDB-XML has been around since at least 2003 but I only recently stumbled upon it on Oracle's website: Berkeley DB XML. Here's the blurb: Oracle Berkeley DB XML is an open source, embeddable XML database with XQuery-based access to documents stored in containers and indexed based on their content. Oracle Berkeley DB XML is built on top of Oracle Berkeley DB and inherits its rich features and attributes. Like Oracle Berkeley DB, it runs in process with the application with no need for human administration. Oracle Berkeley DB XML adds a document parser, XML indexer and XQuery engine on top of Oracle Berkeley DB to enable the fastest, most efficient retrieval of data. To me it seems that the underlying ideas are technically sound and probably more mature than the newer document-based DBs like CouchDB or MongoDB. It has support for C, C++, Ruby and Perl, as far as I can determine. It even has HA-capabilities like automatic replication using a master/slave model with automatic election. However, I can't seem to find any projects that use it. Is there something fundamentally wrong with it? Is the license too onerous? Is it too complicated? Why is it not being used?

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  • Excel Regex, or export to Python? ; "Vlookup" in Python?

    - by victorhooi
    heya, We have an Excel file with a worksheet containing people records. 1. Phone Number Sanitation One of the fields is a phone number field, which contains phone numbers in the format e.g.: +XX(Y)ZZZZ-ZZZZ (where X, Y and Z are integers). There are also some records which have less digits, e.g.: +XX(Y)ZZZ-ZZZZ And others with really screwed up formats: +XX(Y)ZZZZ-ZZZZ / ZZZZ or: ZZZZZZZZ We need to sanitise these all into the format: 0YZZZZZZZZ (or OYZZZZZZ with those with less digits). 2. Fill in Supervisor Details Each person also has a supervisor, given as an numeric ID. We need to do a lookup to get the name and email address of that supervisor, and add it to the line. This lookup will be firstly on the same worksheet (i.e. searching itself), and it can then fallback to another workbook with more people. 3. Approach? For the first issue, I was thinking of using regex in Excel/VBA somehow, to do the parsing. My Excel-fu isn't the best, but I suppose I can learn...lol. Any particular points on this one? However, would I be better off exporting the XLS to a CSV (e.g. using xlrd), then using Python to fix up the phone numbers? For the second approach, I was thinking of just using vlookups in Excel, to pull in the data, and somehow, having it fall through, first on searching itself, then on the external workbook, then just putting in error text. Not sure how to do that last part. However, if I do happen to choose to export to CSV and do it in Python, what's an efficient way of doing the vlookup? (Should I convert to a dict, or just iterate? Or is there a better, or more idiomatic way?) Cheers, Victor

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  • RESTful idempotence

    - by DutrowLLC
    I'm designing a RESTful web service utilizing ROA(Resource oriented architecture). I'm trying to work out an efficient way to guarantee idempotence for PUT requests that create new resources in cases that the server designates the resource key. From my understanding, the traditional approach is to create a type of transaction resource such as /CREATE_PERSON. The the client-server interaction for creating a new person resource would be in two parts: Step 1: Get unique transaction id for creating the new PERSON resource::: **Client request:** GET /CREATE_PERSON **Server response:** 200 OK transaction-id:"as8yfasiob" Step 2: Create the new person resource in a request guaranteed to be unique by using the transaction id::: **Client request** PUT /CREATE_PERSON/{transaction_id} first_name="Big bubba" **Server response** 201 Created // (If the request is a duplicate, it would send this PersonKey="398u4nsdf" // same response without creating a new resource. It // would perhaps send an error response if the was used // on a transaction id non-duplicate request, but I have // control over the client, so I can guarantee that this // won't happen) The problem that I see with this approach is that it requires sending two requests to the server in order to do to single operation of creating a new PERSON resource. This creates a performance issues increasing the chance that the user will be waiting around for the client to complete their request. I've been trying to hash out ideas for eliminating the first step such as pre-sending transaction-id's with each request, but most of my ideas have other issues or involve sacrificing the statelessness of the application. Is there a way to do this?

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  • 2d array, using calloc in C

    - by BigBirdy
    Hi, I'm trying to create a 2D array of chars to storage lines of chars. For Example: lines[0]="Hello"; lines[1]="Your Back"; lines[2]="Bye"; Since lines has to be dynamically cause i don't know how many lines i need at first. Here is the code i have: int i; char **lines= (char**) calloc(size, sizeof(char*)); for ( i = 0; i < size; i++ ){ lines[i] = (char*) calloc(200, sizeof(char)); } for ( i = 0; i < size; i++ ){ free(lines[i]); } free(lines); I know that each line can't go over 200 chars. I keep getting errors like "error C2059: syntax error : 'for'" and such. Any ideas of what i did wrong?

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  • How to persist options selected in AlertDialog spawned from ItemizedOverlay onTap method

    - by ahsteele
    In the description of how to add a list of options to an AlertDialog the official Android documentation alludes to saving a users preferences with one of the "data storage techniques." The examples assume the AlertDialog has been spawned within an Activity class. In my case I've created a class that extends ItemizedOverlay. This class overrides the onTap method and uses an AlertDialog to prompt the user to make a multi-choice selection. I would like to capture and persist the selections for each OverlayItem they tap on. The below code is the onTap method I've written. It functions as written but doesn't yet do what I'd hope. I'd like to capture and persist each selection made by the user to be used later. How do I do that? Is using an AlertDialog in this manner a good idea? Are there better options? protected boolean onTap(int index) { OverlayItem item = _overlays.get(index); final CharSequence[] items = { "WiFi", "BlueTooth" }; final boolean[] checked = { false, false }; AlertDialog.Builder builder = new AlertDialog.Builder(_context); builder.setTitle(item.getTitle()); builder.setMultiChoiceItems(items, checked, new DialogInterface.OnMultiChoiceClickListener() { @Override public void onClick(DialogInterface dialog, int item, boolean isChecked) { // for now just show that the user touched an option Toast.makeText(_context, items[item], Toast.LENGTH_SHORT).show(); } }); builder.setPositiveButton("Okay", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int id) { // should I be examining what was checked here? dialog.dismiss(); } }); builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int id) { dialog.cancel(); } }); AlertDialog alert = builder.create(); alert.show(); return true; }

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  • Compression algorithm for IEEE-754 data

    - by David Taylor
    Anyone have a recommendation on a good compression algorithm that works well with double precision floating point values? We have found that the binary representation of floating point values results in very poor compression rates with common compression programs (e.g. Zip, RAR, 7-Zip etc). The data we need to compress is a one dimensional array of 8-byte values sorted in monotonically increasing order. The values represent temperatures in Kelvin with a span typically under of 100 degrees. The number of values ranges from a few hundred to at most 64K. Clarifications All values in the array are distinct, though repetition does exist at the byte level due to the way floating point values are represented. A lossless algorithm is desired since this is scientific data. Conversion to a fixed point representation with sufficient precision (~5 decimals) might be acceptable provided there is a significant improvement in storage efficiency. Update Found an interesting article on this subject. Not sure how applicable the approach is to my requirements. http://users.ices.utexas.edu/~burtscher/papers/dcc06.pdf

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  • SQL Joining on a one-to-many relationship

    - by Harley
    Ok, here was my original question; Table one contains ID|Name 1 Mary 2 John Table two contains ID|Color 1 Red 1 Blue 2 Blue 2 Green 2 Black I want to end up with is ID|Name|Red|Blue|Green|Black 1 Mary Y Y 2 John Y Y Y It seems that because there are 11 unique values for color and 1000's upon 1000's of records in table one that there is no 'good' way to do this. So, two other questions. Is there an efficient way to query to get this result? I can then create a crosstab in my application to get the desired result. ID|Name|Color 1 Mary Red 1 Mary Blue 2 John Blue 2 John Green 2 John Black If I wanted to limit the number of records returned how could I do a query to do something like this? Where ((color='blue') AND (color<>'red' OR color<>'green')) So using the above example I would then get back ID|Name|Color 1 Mary Blue 2 John Blue 2 John Black I connect to Visual FoxPro tables via ADODB to use SQL. Thanks!

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  • Querying a self referencing join with NHibernate Linq

    - by Ben
    In my application I have a Category domain object. Category has a property Parent (of type category). So in my NHibernate mapping I have: <many-to-one name="Parent" column="ParentID"/> Before I switched to NHibernate I had the ParentId property on my domain model (mapped to the corresponding database column). This made it easy to query for say all top level categories (ParentID = 0): where(c => c.ParentId == 0) However, I have since removed the ParentId property from my domain model (because of NHibernate) so I now have to do the same query (using NHibernate.Linq) like so: public IList<Category> GetCategories(int parentId) { if (parentId == 0) return _catalogRepository.Categories.Where(x => x.Parent == null).ToList(); else return _catalogRepository.Categories.Where(x => x.Parent.Id == parentId).ToList(); } The real impact that I can see, is the sql generated. Instead of a simple 'select x,y,z from categories where parentid = 0' NHibernate generates a left outer join: SELECT this_.CategoryId as CategoryId4_1_, this_.ParentID as ParentID4_1_, this_.Name as Name4_1_, this_.Slug as Slug4_1_, parent1_.CategoryId as CategoryId4_0_, parent1_.ParentID as ParentID4_0_, parent1_.Name as Name4_0_, parent1_.Slug as Slug4_0_ FROM Categories this_ left outer join Categories parent1_ on this_.ParentID = parent1_.CategoryId WHERE this_.ParentID is null Which doesn't seems much less efficient that what I had before. Is there a better way of querying these self referencing joins as it's very tempting to drop the ParentID back onto my domain model for this reason. Thanks, Ben

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  • Best practices to develop and maintaing code for complex JQuery/JQueryUI based applications

    - by dafi
    I'm working on my first very complex JQuery based application. A single web page can contain hundreds of JQuery related code for example to JQueryUI dialogs. Now I want to organize code in separated files. For example I'm moving all initialization dialogs code $("#dialog-xxx").dialog({...}) in separated files and due to reuse I wrap them on single function call like dialogs.js function initDialog_1() { $("#dialog-1").dialog({}); } function initDialog_2() { $("#dialog-2").dialog({}); } This simplifies function code and make caller page clear $(function() { // do some init stuff initDialog_1(); initTooltip_2(); }); Is this the correct pattern? Are you using more efficient techniques? I know that splitting code in many js files introduces an ugly band-bandwidth usage so. Does exist some good practice or tool to 'join' files for production environments? I imagine some tool that does more work than simply minimize and/or compress JS code.

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  • COM access to classic ASP intrinsic objects

    - by wrench
    I'm converting a VB6 COM object that works with classic ASP to a c# .Net COM Object Interop_COMSVCS.ObjectContext objContext; Interop_COMSVCS.AppServer objAppServer; objAppServer = null; // need to initialize before using objAppServer = new Interop_COMSVCS.AppServer(); objContext = objAppServer.GetObjectContext(); oApplication = (Interop_ASP.Application)objContext["Application"]; oSession = (Interop_ASP.Session)objContext["Session"]; oResponse = (Interop_ASP.Response)objContext["Response"]; oRequest = (Interop_ASP.Request)objContext["Request"]; oSession works to store local information to.from ASP storage oResponse can do simple writes to the browser BUT any code like oRequest.Cookies["sessionId"] or oResponse.Cookies["sessionId"] doesn't provide any sort of read or write access. Any cast or conversion I trry to do tells me I'm dealing with an empty or null System Object. There doesn't seem to be any sort of syntax to get/set the cookie collection. With COM+ I've seesn soem articles that indcate a switch for Access to ASP Intrinsic Objects -- that seesm to describe my issue, but I'd rather not use COM+. There are also some articles that indicate if I was using ASP.NET I could use HttpContext and HttpRequest/Response, but that's a completely different set of data objects that don't seem to be available with classic ASP. I've been stuck on this fopr a few days. Any help appreciated.

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