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• Self referential type

  - by pythonic metaphor

  What type T makes the following code compilable? T f(){ return &f; } I'd prefer a C answer, but I marked the question as C and C++ in case there is only an answer using templates.

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• Model self referential collections in Rails

  - by Najitaka

  I have written an application for an online clothing store in Rails 2.3.5. I want to show related Products when a customer views the Product Detail page. For example, if the customer views the detail page for a suit, I'd like to display the accessory products that match the dress such as a vest, shoes, and belt. I have named the related products an Ensemble. However, the vest, shoes, and belts are also Products which is what has me struggling. I have it working as follows but I know it's not the Rails way. I have a Products table for all of the products. Not important here but I also have a ProductDetails table. I have an Ensembles table that has the following columns: product_id - the main or origination product, the one displayed on the detail page outfit_id - the related or accessory product In setting up the data, on the Products list, for each Product I have an Ensemble link. This link takes you to the index action in the Ensembles controller. Using the id from the "main" Product, I find all of the associated Ensemble rows by product_id or I create a new ensemble and assign the id from the main product as the product_id. I'd like to just be able to do @product.related_products to get an Ensemble collection. Also on the index page I list the columns of the main product so the user can be sure their main product was the one they selected from the list. I also have a select list of the other products, with an Add to Ensemble action. Finally on the same index page, I have a table that displays the products that are already in the ensemble and in that list each row has a destroy link to remove a particular product from the ensemble. It would be nice if given a single Ensemble row @ensemble I could do @ensemble.product to get the Product related to the outfit_id of the ensemble row. I've got it working without associations but I have to run queries in the controller to build my own @product, @ensemble, and @ensembles collections. Also the only way I found to destroy an ensemble row is by Ensemble.connection.delete(sql to delete), simple @ensemble.destroy doesn't work. Anyone know how I would set up the associations or have a link to a site explaining a similar setup. None of the examples I found use the same table. They have A related to B through C. I want A related to other A through B.

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• Sampler referencing in HLSL - Sampler parameter must come from a literal expression

  - by user1423893

  The following method works fine when referencing a sampler in HLSL float3 P = lightScreenPos; sampler ShadowSampler = DPFrontShadowSampler; float depth; if (alpha >= 0.5f) { // Reference the correct sampler ShadowSampler = DPFrontShadowSampler; // Front hemisphere 'P0' P.z = P.z + 1.0; P.x = P.x / P.z; P.y = P.y / P.z; P.z = lightLength / LightAttenuation.z; // Rescale viewport to be [0, 1] (texture coordinate space) P.x = 0.5f * P.x + 0.5f; P.y = -0.5f * P.y + 0.5f; depth = tex2D(ShadowSampler, P.xy).x; depth = 1.0 - depth; } else { // Reference the correct sampler ShadowSampler = DPBackShadowSampler; // Back hemisphere 'P1' P.z = 1.0 - P.z; P.x = P.x / P.z; P.y = P.y / P.z; P.z = lightLength / LightAttenuation.z; // Rescale viewport to be [0, 1] (texture coordinate space) P.x = 0.5f * P.x + 0.5f; P.y = -0.5f * P.y + 0.5f; depth = tex2D(ShadowSampler, P.xy).x; depth = 1.0 - depth; } // [Standard Depth Calculation] float mydepth = P.z; shadow = depth + Bias.x < mydepth ? 0.0f : 1.0f; If I try and do anything with the sampler reference outside the if statement then I get the following error: Sampler parameter must come from a literal expression This code demonstrates that float3 P = lightScreenPos; sampler ShadowSampler = DPFrontShadowSampler; if (alpha >= 0.5f) { // Reference the correct sampler ShadowSampler = DPFrontShadowSampler; // Front hemisphere 'P0' P.z = P.z + 1.0; P.x = P.x / P.z; P.y = P.y / P.z; P.z = lightLength / LightAttenuation.z; } else { // Reference the correct sampler ShadowSampler = DPBackShadowSampler; // Back hemisphere 'P1' P.z = 1.0 - P.z; P.x = P.x / P.z; P.y = P.y / P.z; P.z = lightLength / LightAttenuation.z; } // Rescale viewport to be [0, 1] (texture coordinate space) P.x = 0.5f * P.x + 0.5f; P.y = -0.5f * P.y + 0.5f; // [Standard Depth Calculation] float depth = tex2D(ShadowSampler, P.xy).x; depth = 1.0 - depth; float mydepth = P.z; shadow = depth + Bias.x < mydepth ? 0.0f : 1.0f; How can I reference the sampler in this manner without triggering the error?

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• Referencing a picture in another DLL in Silverlight and Windows Phone 7

  - by Laurent Bugnion

  This one has burned me a few times, so here is how it works for future reference: Usually, when I add an Image control into a Silverlight application, and the picture it shows is local (as opposed to loaded from the web), I set the picture’s Build Action to Content, and the Copy to Output Directory to Copy if Newer. What the compiler does then is to copy the picture to the bin\Debug folder, and then to pack it into the XAP file. In XAML, the syntax to refer to this local picture is: <Image Source="/Images/mypicture.jpg" Width="100" Height="100" /> And in C#: return new BitmapImage(new Uri( "/Images/mypicture.jpg", UriKind.Relative)); One of the features of Silverlight is to allow referencing content (pictures, resource dictionaries, sound files, movies etc…) located in a DLL directly. This is very handy because just by using the right syntax in the URI, you can do this in XAML directly, for example with: <Image Source="/MyApplication;component/Images/mypicture.jpg" Width="100" Height="100" /> In C#, this becomes: return new BitmapImage(new Uri( "/MyApplication;component/Images/mypicture.jpg", UriKind.Relative)); Side note: This kind of URI is called a pack URI and they have been around since the early days of WPF. There is a good tutorial about pack URIs on MSDN. Even though it refers to WPF, it also applies to Silverlight Side note 2: With the Build Action set to Content, you can rename the XAP file to ZIP, extract all the files, change the picture (but keep the same name), rezip the whole thing and rename again to XAP. This is not possible if the picture is embedded in an assembly! So what’s the catch? Well the catch is that this does not work if you set the Build Action to Content. It’s actually pretty simple to explain: The pack URI above tells the Silverlight runtime to look within an assembly named MyOtherAssembly for a file named MyPicture.jpg in the Images folder. If the file is included as Content, however, it is not in the assembly. Silverlight does not find it, and silently returns nothing. The image is not displayed. And the fix? The fix, for class libraries, is to set the Build Action to Resource. With this, the picture will gets packed into the DLL itself. Of course, this will increase the size of the DLL, and any change to the picture will require recompiling the class library, which is not ideal. But in the cases where you want to distribute pictures (icons etc) together with a plug-in assembly, well, this is a good way to have everything in the same place Happy coding, Laurent   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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• JSP/Struts2/Hibernate: loop through a self-referencing table.

  - by TBW

  Hello everyone, Let's say we have a self-referencing table called PERSON, with the following columns: ID, PARENT, where PARENT is a foreign key to the ID column of another element in the PERSON table. Of course, many persons can have the same parent. I use Hibernate 3 in lazy fetching mode to deal with the database. Hibernate fetches a person element from the database, which is then put in the ValueStack by the Struts2 action, to be used on the result JSP page. Now the question is : In JSP, how can I do to display all the child (and the child's child, and so on, like a family tree) of this person element? Of course, for the n+1 children I can use the < s:iterator tag over the person.person. I can also nest another < s:iterator tag over person.person.person to get the n+2 children. But what if I want to do this in an automated manner, up to the last n+p child, displaying in the process all the children of all the n+1..n+p elements? I hope I have been clear enough. Thank you all for your time. -- TBW.

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• How to stop a QDialog from executing while still in the __init__ statement(or immediatly after)?

  - by Jonathan

  I am wondering how I can go about stopping a dialog from opening if certain conditions are met in its __init__ statement. The following code tries to call the 'self.close()' function and it does, but (I'm assuming) since the dialog has not yet started its event loop, that it doesn't trigger the close event? So is there another way to close and/or stop the dialog from opening without triggering an event? Example code: from PyQt4 import QtCore, QtGui class dlg_closeInit(QtGui.QDialog): ''' Close the dialog if a certain condition is met in the __init__ statement ''' def __init__(self): QtGui.QDialog.__init__(self) self.txt_mytext = QtGui.QLineEdit('some text') self.btn_accept = QtGui.QPushButton('Accept') self.myLayout = QtGui.QVBoxLayout(self) self.myLayout.addWidget(self.txt_mytext) self.myLayout.addWidget(self.btn_accept) self.setLayout(self.myLayout) # Connect the button self.connect(self.btn_accept,QtCore.SIGNAL('clicked()'), self.on_accept) self.close() def on_accept(self): # Get the data... self.mydata = self.txt_mytext.text() self.accept() def get_data(self): return self.mydata def closeEvent(self, event): print 'Closing...' if __name__ == '__main__': import sys app = QtGui.QApplication(sys.argv) dialog = dlg_closeInit() if dialog.exec_(): print dialog.get_data() else: print "Failed"

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• Python Locking Implementation (with threading module)

  - by Matty

  This is probably a rudimentary question, but I'm new to threaded programming in Python and am not entirely sure what the correct practice is. Should I be creating a single lock object (either globally or being passed around) and using that everywhere that I need to do locking? Or, should I be creating multiple lock instances in each of the classes where I will be employing them. Take these 2 rudimentary code samples, which direction is best to go? The main difference being that a single lock instance is used in both class A and B in the second, while multiple instances are used in the first. Sample 1 class A(): def __init__(self, theList): self.theList = theList self.lock = threading.Lock() def poll(self): while True: # do some stuff that eventually needs to work with theList self.lock.acquire() try: self.theList.append(something) finally: self.lock.release() class B(threading.Thread): def __init__(self,theList): self.theList = theList self.lock = threading.Lock() self.start() def run(self): while True: # do some stuff that eventually needs to work with theList self.lock.acquire() try: self.theList.remove(something) finally: self.lock.release() if __name__ == "__main__": aList = [] for x in range(10): B(aList) A(aList).poll() Sample 2 class A(): def __init__(self, theList,lock): self.theList = theList self.lock = lock def poll(self): while True: # do some stuff that eventually needs to work with theList self.lock.acquire() try: self.theList.append(something) finally: self.lock.release() class B(threading.Thread): def __init__(self,theList,lock): self.theList = theList self.lock = lock self.start() def run(self): while True: # do some stuff that eventually needs to work with theList self.lock.acquire() try: self.theList.remove(something) finally: self.lock.release() if __name__ == "__main__": lock = threading.Lock() aList = [] for x in range(10): B(aList,lock) A(aList,lock).poll()

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• Manager Self Service at your Fingertips

  - by Elaine Clement

  Last week we released new and improved Manager Self Service capabilities in PeopleSoft HCM 9.1. We delivered a new Manager Dashboard, streamlined many Manager Self Service transactions, provided new Pivot Grid capabilities, and implemented one-click Related Actions accessible from multiple places – all with the goal of improving every Manager’s self service experience. Manager Dashboard These new capabilities have the potential to significantly impact an organization’s bottom line, and here is why. Increased Efficiency The Manager Dashboard provides a ‘one-stop shop’ for your Managers with all of the key data they need consolidated into a single view. Alerts notifying managers of important tasks are immediately viewable and actionable. Administrators can configure the dashboard to include the most important pagelets needed for their organization, and Managers can personalize it to fit within their personal way of conducting their tasks. The Related Actions feature further improves the ease with which Managers get their work done by providing one-click access to Manager Self Service transactions.  Increased Job Satisfaction The streamlined Manager transactions, related actions, and the new Manager Dashboard provide an enhanced user experience. Managers are able to quickly get in, get the information they need, complete their transactions, and get out. Managers can spend their time focusing on getting the business results they need instead of their day to day HR tasks. Enhanced Decision Support Administrators can ensure the information and analytics they want their Managers to use are available from the Manager Dashboard, establishing best business practices. Additional pivot grids relevant to your own organization can be added to the Manager Dashboard. With this easy access to the relevant information in an easily understood format, Managers can make the right business decisions needed to improve their team and their team’s productivity. For more details on the Manager Dashboard and some of the other newly posted features, such as a new Talent Summary, check out this video and others: Oracle PeopleSoft Webcasts

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• custom tabbars and make them circulate

  - by pengwang

  i want to custom tabbars and want to circulate slide,default tab bar only have 5 items show at the same time,it not meet me,i have 11 items,so i want to make 3 tabbars ,every have 5 items,for example A(0-4)--B(5-9)--C(10)--A--B--C--A. at print i only finish A(0-4)--B(5-9)--C(10),how to make them circulate? my code : .h file #import <UIKit/UIKit.h> @protocol InfiniTabBarDelegate; @interface InfiniTabBar : UIScrollView <UIScrollViewDelegate, UITabBarDelegate> { __weak id <InfiniTabBarDelegate> infiniTabBarDelegate; NSMutableArray *tabBars; UITabBar *aTabBar; UITabBar *bTabBar; } @property (nonatomic, weak) id infiniTabBarDelegate; @property (strong,nonatomic) NSMutableArray *tabBars; @property (strong,nonatomic) UITabBar *aTabBar; @property (strong,nonatomic) UITabBar *bTabBar; - (id)initWithItems:(NSArray *)items; - (void)setBounces:(BOOL)bounces; // Don't set more items than initially - (void)setItems:(NSArray *)items animated:(BOOL)animated; - (int)currentTabBarTag; - (int)selectedItemTag; - (BOOL)scrollToTabBarWithTag:(int)tag animated:(BOOL)animated; - (BOOL)selectItemWithTag:(int)tag; @end @protocol InfiniTabBarDelegate <NSObject> - (void)infiniTabBar:(InfiniTabBar *)tabBar didScrollToTabBarWithTag:(int)tag; - (void)infiniTabBar:(InfiniTabBar *)tabBar didSelectItemWithTag:(int)tag; @end .m file @implementation InfiniTabBar @synthesize infiniTabBarDelegate; @synthesize tabBars; @synthesize aTabBar; @synthesize bTabBar; - (id)initWithItems:(NSArray *)items { self = [super initWithFrame:CGRectMake(0.0, 411.0, 320.0, 49.0)]; // TODO: //self = [super initWithFrame:CGRectMake(self.superview.frame.origin.x + self.superview.frame.size.width - 320.0, self.superview.frame.origin.y + self.superview.frame.size.height - 49.0, 320.0, 49.0)]; // Doesn't work. self is nil at this point. if (self) { self.pagingEnabled = YES; self.delegate = self; self.tabBars = [[NSMutableArray alloc] init]; float x = 0.0; for (double d = 0; d < ceil(items.count / 5.0); d ++) { UITabBar *tabBar = [[UITabBar alloc] initWithFrame:CGRectMake(x, 0.0, 320.0, 49.0)]; tabBar.delegate = self; int len = 0; for (int i = d * 5; i < d * 5 + 5; i ++) if (i < items.count) len ++; tabBar.items = [items objectsAtIndexes:[NSIndexSet indexSetWithIndexesInRange:NSMakeRange(d * 5, len)]]; // NSLog(@"####%@",NSMakeRange(d * 5, len)); [self.tabBars addObject:tabBar]; [self addSubview:tabBar]; x += 320.0; } self.contentSize = CGSizeMake(x, 49.0); } return self; } - (void)setBounces:(BOOL)bounces { if (bounces) { int count = self.tabBars.count; if (count > 0) { if (self.aTabBar == nil) self.aTabBar = [[UITabBar alloc] initWithFrame:CGRectMake(-320.0, 0.0, 320.0, 49.0)]; [self addSubview:self.aTabBar]; if (self.bTabBar == nil) self.bTabBar = [[UITabBar alloc] initWithFrame:CGRectMake(count * 320.0, 0.0, 320.0, 49.0)]; [self addSubview:self.bTabBar]; } } else { [self.aTabBar removeFromSuperview]; [self.bTabBar removeFromSuperview]; } [super setBounces:bounces]; } - (void)setItems:(NSArray *)items animated:(BOOL)animated { for (UITabBar *tabBar in self.tabBars) { int len = 0; for (int i = [self.tabBars indexOfObject:tabBar] * 5; i < [self.tabBars indexOfObject:tabBar] * 5 + 5; i ++) if (i < items.count) len ++; [tabBar setItems:[items objectsAtIndexes:[NSIndexSet indexSetWithIndexesInRange:NSMakeRange([self.tabBars indexOfObject:tabBar] * 5, len)]] animated:animated]; } self.contentSize = CGSizeMake(ceil(items.count / 5.0) * 320.0, 49.0); } - (int)currentTabBarTag { return self.contentOffset.x / 320.0; } - (int)selectedItemTag { for (UITabBar *tabBar in self.tabBars) if (tabBar.selectedItem != nil) return tabBar.selectedItem.tag; // No item selected return 0; } - (BOOL)scrollToTabBarWithTag:(int)tag animated:(BOOL)animated { for (UITabBar *tabBar in self.tabBars) if ([self.tabBars indexOfObject:tabBar] == tag) { UITabBar *tabBar = [self.tabBars objectAtIndex:tag]; [self scrollRectToVisible:tabBar.frame animated:animated]; if (animated == NO) [self scrollViewDidEndDecelerating:self]; return YES; } return NO; } - (BOOL)selectItemWithTag:(int)tag { for (UITabBar *tabBar in self.tabBars) for (UITabBarItem *item in tabBar.items) if (item.tag == tag) { tabBar.selectedItem = item; [self tabBar:tabBar didSelectItem:item]; return YES; } return NO; } - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView { [infiniTabBarDelegate infiniTabBar:self didScrollToTabBarWithTag:scrollView.contentOffset.x / 320.0]; } - (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView { [self scrollViewDidEndDecelerating:scrollView]; } - (void)tabBar:(UITabBar *)cTabBar didSelectItem:(UITabBarItem *)item { // Act like a single tab bar for (UITabBar *tabBar in self.tabBars) if (tabBar != cTabBar) tabBar.selectedItem = nil; [infiniTabBarDelegate infiniTabBar:self didSelectItemWithTag:item.tag]; } @end

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• Self-signed certificates for a known community

  - by costlow

  Recently announced changes scheduled for Java 7 update 51 (January 2014) have established that the default security slider will require code signatures and the Permissions Manifest attribute. Code signatures are a common practice recommended in the industry because they help determine that the code your computer will run is the same code that the publisher created. This post is written to help users that need to use self-signed certificates without involving a public Certificate Authority. The role of self-signed certificates within a known community You may still use self-signed certificates within a known community. The difference between self-signed and purchased-from-CA is that your users must import your self-signed certificate to indicate that it is valid, whereas Certificate Authorities are already trusted by default. This works for known communities where people will trust that my certificate is mine, but does not scale widely where I cannot actually contact or know the systems that will need to trust my certificate. Public Certificate Authorities are widely trusted already because they abide by many different requirements and frequent checks. An example would be students in a university class sharing their public certificates on a mailing list or web page, employees publishing on the intranet, or a system administrator rolling certificates out to end-users. Managed machines help this because you can automate the rollout, but they are not required -- the major point simply that people will trust and import your certificate. How to distribute self-signed certificates for a known community There are several steps required to distribute a self-signed certificate to users so that they will properly trust it. These steps are: Creating a public/private key pair for signing. Exporting your public certificate for others Importing your certificate onto machines that should trust you Verify work on a different machine Creating a public/private key pair for signing Having a public/private key pair will give you the ability both to sign items yourself and issue a Certificate Signing Request (CSR) to a certificate authority. Create your public/private key pair by following the instructions for creating key pairs.Every Certificate Authority that I looked at provided similar instructions, but for the sake of cohesiveness I will include the commands that I used here: Generate the key pair.keytool -genkeypair -alias erikcostlow -keyalg EC -keysize 571 -validity 730 -keystore javakeystore_keepsecret.jks Provide a good password for this file. The alias "erikcostlow" is my name and therefore easy to remember. Substitute your name of something like "mykey." The sigalg of EC (Elliptical Curve) and keysize of 571 will give your key a good strong lifetime. All keys are set to expire. Two years or 730 days is a reasonable compromise between not-long-enough and too-long. Most public Certificate Authorities will sign something for one to five years. You will be placing your keys in javakeystore_keepsecret.jks -- this file will contain private keys and therefore should not be shared. If someone else gets these private keys, they can impersonate your signature. Please be cautious about automated cloud backup systems and private key stores. Answer all the questions. It is important to provide good answers because you will stick with them for the "-validity" days that you specified above.What is your first and last name?  [Unknown]:  First LastWhat is the name of your organizational unit?  [Unknown]:  Line of BusinessWhat is the name of your organization?  [Unknown]:  MyCompanyWhat is the name of your City or Locality?  [Unknown]:  City NameWhat is the name of your State or Province?  [Unknown]:  CAWhat is the two-letter country code for this unit?  [Unknown]:  USIs CN=First Last, OU=Line of Business, O=MyCompany, L=City, ST=CA, C=US correct?  [no]:  yesEnter key password for <erikcostlow>        (RETURN if same as keystore password): Verify your work:keytool -list -keystore javakeystore_keepsecret.jksYou should see your new key pair. Exporting your public certificate for others Public Key Infrastructure relies on two simple concepts: the public key may be made public and the private key must be private. By exporting your public certificate, you are able to share it with others who can then import the certificate to trust you. keytool -exportcert -keystore javakeystore_keepsecret.jks -alias erikcostlow -file erikcostlow.cer To verify this, you can open the .cer file by double-clicking it on most operating systems. It should show the information that you entered during the creation prompts. This is the file that you will share with others. They will use this certificate to prove that artifacts signed by this certificate came from you. If you do not manage machines directly, place the certificate file on an area that people within the known community should trust, such as an intranet page. Import the certificate onto machines that should trust you In order to trust the certificate, people within your known network must import your certificate into their keystores. The first step is to verify that the certificate is actually yours, which can be done through any band: email, phone, in-person, etc. Known networks can usually do this Determine the right keystore: For an individual user looking to trust another, the correct file is within that user’s directory.e.g. USER_HOME\AppData\LocalLow\Sun\Java\Deployment\security\trusted.certs For system-wide installations, Java’s Certificate Authorities are in JAVA_HOMEe.g. C:\Program Files\Java\jre8\lib\security\cacerts File paths for Mac and Linux are included in the link above. Follow the instructions to import the certificate into the keystore. keytool -importcert -keystore THEKEYSTOREFROMABOVE -alias erikcostlow -file erikcostlow.cer In this case, I am still using my name for the alias because it’s easy for me to remember. You may also use an alias of your company name. Scaling distribution of the import The easiest way to apply your certificate across many machines is to just push the .certs or cacerts file onto them. When doing this, watch out for any changes that people would have made to this file on their machines. Trusted.certs: When publishing into user directories, your file will overwrite any keys that the user has added since last update. CACerts: It is best to re-run the import command with each installation rather than just overwriting the file. If you just keep the same cacerts file between upgrades, you will overwrite any CAs that have been added or removed. By re-importing, you stay up to date with changes. Verify work on a different machine Verification is a way of checking on the client machine to ensure that it properly trusts signed artifacts after you have added your signing certificate. Many people have started using deployment rule sets. You can validate the deployment rule set by: Create and sign the deployment rule set on the computer that holds the private key. Copy the deployment rule set on to the different machine where you have imported the signing certificate. Verify that the Java Control Panel’s security tab shows your deployment rule set. Verifying an individual JAR file or multiple JAR files You can test a certificate chain by using the jarsigner command. jarsigner -verify filename.jar If the output does not say "jar verified" then run the following command to see why: jarsigner -verify -verbose -certs filename.jar Check the output for the term “CertPath not validated.”

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• Python: nonblocking read from stdout of threaded subprocess

  - by sberry2A

  I have a script (worker.py) that prints unbuffered output in the form... 1 2 3 . . . n where n is some constant number of iterations a loop in this script will make. In another script (service_controller.py) I start a number of threads, each of which starts a subprocess using subprocess.Popen(stdout=subprocess.PIPE, ...); Now, in my main thread (service_controller.py) I want to read the output of each thread's worker.py subprocess and use it to calculate an estimate for the time remaining till completion. I have all of the logic working that reads the stdout from worker.py and determines the last printed number. The problem is that I can not figure out how to do this in a non-blocking way. If I read a constant bufsize then each read will end up waiting for the same data from each of the workers. I have tried numerous ways including using fcntl, select + os.read, etc. What is my best option here? I can post my source if needed, but I figured the explanation describes the problem well enough. Thanks for any help here. EDIT Adding sample code I have a worker that starts a subprocess. class WorkerThread(threading.Thread): def __init__(self): self.completed = 0 self.process = None self.lock = threading.RLock() threading.Thread.__init__(self) def run(self): cmd = ["/path/to/script", "arg1", "arg2"] self.process = subprocess.Popen(cmd, stdout=subprocess.PIPE, bufsize=1, shell=False) #flags = fcntl.fcntl(self.process.stdout, fcntl.F_GETFL) #fcntl.fcntl(self.process.stdout.fileno(), fcntl.F_SETFL, flags | os.O_NONBLOCK) def get_completed(self): self.lock.acquire(); fd = select.select([self.process.stdout.fileno()], [], [], 5)[0] if fd: self.data += os.read(fd, 1) try: self.completed = int(self.data.split("\n")[-2]) except IndexError: pass self.lock.release() return self.completed I then have a ThreadManager. class ThreadManager(): def __init__(self): self.pool = [] self.running = [] self.lock = threading.Lock() def clean_pool(self, pool): for worker in [x for x in pool is not x.isAlive()]: worker.join() pool.remove(worker) del worker return pool def run(self, concurrent=5): while len(self.running) + len(self.pool) > 0: self.clean_pool(self.running) n = min(max(concurrent - len(self.running), 0), len(self.pool)) if n > 0: for worker in self.pool[0:n]: worker.start() self.running.extend(self.pool[0:n]) del self.pool[0:n] time.sleep(.01) for worker in self.running + self.pool: worker.join() and some code to run it. threadManager = ThreadManager() for i in xrange(0, 5): threadManager.pool.append(WorkerThread()) threadManager.run() I have stripped out a log of the other code in hopes to try to pinpoint the issue.

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• C# Toolbox: Debug-able, Self-Installable Windows Service Template Redux

  - by James Michael Hare

  I had written a pair of posts before about creating a debug-able and self-installing windows service template in C#.  This is a template I began creating to ease creating windows services and to take some of the mundane tasks out of the coding effort.  The original posts were here: C# Windows Services (1 of 2) - Debug-able Windows Services C# Windows Services (2 of 2) - Self-Installing Windows Services But at the time, though I gave the code samples I didn't have a downloadable for of the template on the blog.  After getting many requests for the actual source, I zipped it up and am posting it with this blog entry.  Click on the link below to download the archive.  The password on the archive is, imaginatively enough, password.  Hope you enjoy and please feel free to comment and suggest changes! Debug-able, Self-Installing Windows Service Template download Enjoy! Tweet Technorati Tags: C#,Windows Service,Toolbox

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• Can I avoid a threaded UDP socket in Python dropping data?

  - by 666craig

  First off, I'm new to Python and learning on the job, so be gentle! I'm trying to write a threaded Python app for Windows that reads data from a UDP socket (thread-1), writes it to file (thread-2), and displays the live data (thread-3) to a widget (gtk.Image using a gtk.gdk.pixbuf). I'm using queues for communicating data between threads. My problem is that if I start only threads 1 and 3 (so skip the file writing for now), it seems that I lose some data after the first few samples. After this drop it looks fine. Even by letting thread 1 complete before running thread 3, this apparent drop is still there. Apologies for the length of code snippet (I've removed the thread that writes to file), but I felt removing code would just prompt questions. Hope someone can shed some light :-) import socket import threading import Queue import numpy import gtk gtk.gdk.threads_init() import gtk.glade import pygtk class readFromUDPSocket(threading.Thread): def __init__(self, socketUDP, readDataQueue, packetSize, numScans): threading.Thread.__init__(self) self.socketUDP = socketUDP self.readDataQueue = readDataQueue self.packetSize = packetSize self.numScans = numScans def run(self): for scan in range(1, self.numScans + 1): buffer = self.socketUDP.recv(self.packetSize) self.readDataQueue.put(buffer) self.socketUDP.close() print 'myServer finished!' class displayWithGTK(threading.Thread): def __init__(self, displayDataQueue, image, viewArea): threading.Thread.__init__(self) self.displayDataQueue = displayDataQueue self.image = image self.viewWidth = viewArea[0] self.viewHeight = viewArea[1] self.displayData = numpy.zeros((self.viewHeight, self.viewWidth, 3), dtype=numpy.uint16) def run(self): scan = 0 try: while True: if not scan % self.viewWidth: scan = 0 buffer = self.displayDataQueue.get(timeout=0.1) self.displayData[:, scan, 0] = numpy.fromstring(buffer, dtype=numpy.uint16) self.displayData[:, scan, 1] = numpy.fromstring(buffer, dtype=numpy.uint16) self.displayData[:, scan, 2] = numpy.fromstring(buffer, dtype=numpy.uint16) gtk.gdk.threads_enter() self.myPixbuf = gtk.gdk.pixbuf_new_from_data(self.displayData.tostring(), gtk.gdk.COLORSPACE_RGB, False, 8, self.viewWidth, self.viewHeight, self.viewWidth * 3) self.image.set_from_pixbuf(self.myPixbuf) self.image.show() gtk.gdk.threads_leave() scan += 1 except Queue.Empty: print 'myDisplay finished!' pass def quitGUI(obj): print 'Currently active threads: %s' % threading.enumerate() gtk.main_quit() if __name__ == '__main__': # Create socket (IPv4 protocol, datagram (UDP)) and bind to address socketUDP = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) host = '192.168.1.5' port = 1024 socketUDP.bind((host, port)) # Data parameters samplesPerScan = 256 packetsPerSecond = 1200 packetSize = 512 duration = 1 # For now, set a fixed duration to log data numScans = int(packetsPerSecond * duration) # Create array to store data data = numpy.zeros((samplesPerScan, numScans), dtype=numpy.uint16) # Create queue for displaying from readDataQueue = Queue.Queue(numScans) # Build GUI from Glade XML file builder = gtk.Builder() builder.add_from_file('GroundVue.glade') window = builder.get_object('mainwindow') window.connect('destroy', quitGUI) view = builder.get_object('viewport') image = gtk.Image() view.add(image) viewArea = (1200, samplesPerScan) # Instantiate & start threads myServer = readFromUDPSocket(socketUDP, readDataQueue, packetSize, numScans) myDisplay = displayWithGTK(readDataQueue, image, viewArea) myServer.start() myDisplay.start() gtk.gdk.threads_enter() gtk.main() gtk.gdk.threads_leave() print 'gtk.main finished!'

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• Can I avoid a threaded UDP socket in Pyton dropping data?

  - by 666craig

  First off, I'm new to Python and learning on the job, so be gentle! I'm trying to write a threaded Python app for Windows that reads data from a UDP socket (thread-1), writes it to file (thread-2), and displays the live data (thread-3) to a widget (gtk.Image using a gtk.gdk.pixbuf). I'm using queues for communicating data between threads. My problem is that if I start only threads 1 and 3 (so skip the file writing for now), it seems that I lose some data after the first few samples. After this drop it looks fine. Even by letting thread 1 complete before running thread 3, this apparent drop is still there. Apologies for the length of code snippet (I've removed the thread that writes to file), but I felt removing code would just prompt questions. Hope someone can shed some light :-) import socket import threading import Queue import numpy import gtk gtk.gdk.threads_init() import gtk.glade import pygtk class readFromUDPSocket(threading.Thread): def __init__(self, socketUDP, readDataQueue, packetSize, numScans): threading.Thread.__init__(self) self.socketUDP = socketUDP self.readDataQueue = readDataQueue self.packetSize = packetSize self.numScans = numScans def run(self): for scan in range(1, self.numScans + 1): buffer = self.socketUDP.recv(self.packetSize) self.readDataQueue.put(buffer) self.socketUDP.close() print 'myServer finished!' class displayWithGTK(threading.Thread): def __init__(self, displayDataQueue, image, viewArea): threading.Thread.__init__(self) self.displayDataQueue = displayDataQueue self.image = image self.viewWidth = viewArea[0] self.viewHeight = viewArea[1] self.displayData = numpy.zeros((self.viewHeight, self.viewWidth, 3), dtype=numpy.uint16) def run(self): scan = 0 try: while True: if not scan % self.viewWidth: scan = 0 buffer = self.displayDataQueue.get(timeout=0.1) self.displayData[:, scan, 0] = numpy.fromstring(buffer, dtype=numpy.uint16) self.displayData[:, scan, 1] = numpy.fromstring(buffer, dtype=numpy.uint16) self.displayData[:, scan, 2] = numpy.fromstring(buffer, dtype=numpy.uint16) gtk.gdk.threads_enter() self.myPixbuf = gtk.gdk.pixbuf_new_from_data(self.displayData.tostring(), gtk.gdk.COLORSPACE_RGB, False, 8, self.viewWidth, self.viewHeight, self.viewWidth * 3) self.image.set_from_pixbuf(self.myPixbuf) self.image.show() gtk.gdk.threads_leave() scan += 1 except Queue.Empty: print 'myDisplay finished!' pass def quitGUI(obj): print 'Currently active threads: %s' % threading.enumerate() gtk.main_quit() if __name__ == '__main__': # Create socket (IPv4 protocol, datagram (UDP)) and bind to address socketUDP = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) host = '192.168.1.5' port = 1024 socketUDP.bind((host, port)) # Data parameters samplesPerScan = 256 packetsPerSecond = 1200 packetSize = 512 duration = 1 # For now, set a fixed duration to log data numScans = int(packetsPerSecond * duration) # Create array to store data data = numpy.zeros((samplesPerScan, numScans), dtype=numpy.uint16) # Create queue for displaying from readDataQueue = Queue.Queue(numScans) # Build GUI from Glade XML file builder = gtk.Builder() builder.add_from_file('GroundVue.glade') window = builder.get_object('mainwindow') window.connect('destroy', quitGUI) view = builder.get_object('viewport') image = gtk.Image() view.add(image) viewArea = (1200, samplesPerScan) # Instantiate & start threads myServer = readFromUDPSocket(socketUDP, readDataQueue, packetSize, numScans) myDisplay = displayWithGTK(readDataQueue, image, viewArea) myServer.start() myDisplay.start() gtk.gdk.threads_enter() gtk.main() gtk.gdk.threads_leave() print 'gtk.main finished!'

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• I'm making a simulated tv

  - by Jam

  I need to make a tv that shows the user the channel and the volume, and shows whether or not the television is on. I have the majority of the code made, but for some reason the channels won't switch. I'm fairly unfamiliar with how properties work, and I think that's what my problem here is. Help please. class Television(object): def __init__(self, __channel=1, volume=1, is_on=0): self.__channel=__channel self.volume=volume self.is_on=is_on def __str__(self): if self.is_on==1: print "The tv is on" print self.__channel print self.volume else: print "The television is off." def toggle_power(self): if self.is_on==1: self.is_on=0 return self.is_on if self.is_on==0: self.is_on=1 return self.is_on def get_channel(self): return channel def set_channel(self, choice): if self.is_on==1: if choice>=0 and choice<=499: channel=self.__channel else: print "Invalid channel!" else: print "The television isn't on!" channel=property(get_channel, set_channel) def raise_volume(self, up=1): if self.is_on==1: self.volume+=up if self.volume>=10: self.volume=10 print "Max volume!" else: print "The television isn't on!" def lower_volume(self, down=1): if self.is_on==1: self.volume-=down if self.volume<=0: self.volume=0 print "Muted!" else: print "The television isn't on!" def main(): tv=Television() choice=None while choice!="0": print \ """ Television 0 - Exit 1 - Toggle Power 2 - Change Channel 3 - Raise Volume 4 - Lower Volume """ choice=raw_input("Choice: ") print if choice=="0": print "Good-bye." elif choice=="1": tv.toggle_power() tv.__str__() elif choice=="2": change=raw_input("What would you like to change the channel to?") tv.set_channel(change) tv.__str__() elif choice=="3": tv.raise_volume() tv.__str__() elif choice=="4": tv.lower_volume() tv.__str__() else: print "\nSorry, but", choice, "isn't a valid choice." main() raw_input("Press enter to exit.")

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• What are the disadvantages of self-encapsulation?

  - by Dave Jarvis

  Background Tony Hoare's billion dollar mistake was the invention of null. Subsequently, a lot of code has become riddled with null pointer exceptions (segfaults) when software developers try to use (dereference) uninitialized variables. In 1989, Wirfs-Brock and Wikerson wrote: Direct references to variables severely limit the ability of programmers to re?ne existing classes. The programming conventions described here structure the use of variables to promote reusable designs. We encourage users of all object-oriented languages to follow these conventions. Additionally, we strongly urge designers of object-oriented languages to consider the effects of unrestricted variable references on reusability. Problem A lot of software, especially in Java, but likely in C# and C++, often uses the following pattern: public class SomeClass { private String someAttribute; public SomeClass() { this.someAttribute = "Some Value"; } public void someMethod() { if( this.someAttribute.equals( "Some Value" ) ) { // do something... } } public void setAttribute( String s ) { this.someAttribute = s; } public String getAttribute() { return this.someAttribute; } } Sometimes a band-aid solution is used by checking for null throughout the code base: public void someMethod() { assert this.someAttribute != null; if( this.someAttribute.equals( "Some Value" ) ) { // do something... } } public void anotherMethod() { assert this.someAttribute != null; if( this.someAttribute.equals( "Some Default Value" ) ) { // do something... } } The band-aid does not always avoid the null pointer problem: a race condition exists. The race condition is mitigated using: public void anotherMethod() { String someAttribute = this.someAttribute; assert someAttribute != null; if( someAttribute.equals( "Some Default Value" ) ) { // do something... } } Yet that requires two statements (assignment to local copy and check for null) every time a class-scoped variable is used to ensure it is valid. Self-Encapsulation Ken Auer's Reusability Through Self-Encapsulation (Pattern Languages of Program Design, Addison Wesley, New York, pp. 505-516, 1994) advocated self-encapsulation combined with lazy initialization. The result, in Java, would resemble: public class SomeClass { private String someAttribute; public SomeClass() { setAttribute( "Some Value" ); } public void someMethod() { if( getAttribute().equals( "Some Value" ) ) { // do something... } } public void setAttribute( String s ) { this.someAttribute = s; } public String getAttribute() { String someAttribute = this.someAttribute; if( someAttribute == null ) { setAttribute( createDefaultValue() ); } return someAttribute; } protected String createDefaultValue() { return "Some Default Value"; } } All duplicate checks for null are superfluous: getAttribute() ensures the value is never null at a single location within the containing class. Efficiency arguments should be fairly moot -- modern compilers and virtual machines can inline the code when possible. As long as variables are never referenced directly, this also allows for proper application of the Open-Closed Principle. Question What are the disadvantages of self-encapsulation, if any? (Ideally, I would like to see references to studies that contrast the robustness of similarly complex systems that use and don't use self-encapsulation, as this strikes me as a fairly straightforward testable hypothesis.)

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• Rejuvenated: Script Creates and Drops for Candidate Keys and Referencing Foreign Keys

  - by Adam Machanic

  Once upon a time it was 2004, and I wrote what I have to say was a pretty cool little script . (Yes, I know the post is dated 2006, but that's because I dropped the ball and failed to back-date the posts when I moved them over here from my prior blog space.) The impetus for creating this script was (and is) simple: Changing keys can be a painful experience. Sometimes you want to make a clustered key nonclustered, or a nonclustered key clustered. Or maybe you want to add a column to the key. Or remove...(read more)

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• Atom feed validator keeps showing Self reference doesn't match document location

  - by Dino

  I am creating an atom feed, but when I validate it I keep getting: Self reference doesn't match document location and the specific line that is causing the error is: <link rel="self" type="application/atom+xml" href="http://www.example.com/test.rss"/> Please can anyone advise what the error is? Ps. I noticed an up arrow just at the end of that line. (presumably something to do with that bbut not sure)

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• Referencing environment variables *in* /etc/environment?

  - by Stefan Kendall

  I recently discovered /etc/environment, which seems a more standard way to setup simple environment variables than scripts, but I was wondering if there was a way to back-reference environment variables in the /etc/environment file. That is, I have this: JAVA_HOME="/tools/java" GRAILS_HOME="/tools/grails" GROOVY_HOME="/tools/groovy" GRADLE_HOME="/tools/gradle" PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games" If I try to add $JAVA_HOME/bin to the PATH definition, however, I get $JAVA_HOME/bin, and not the interpolated variable. To remedy this, I'm creating environment.sh in profile.d to add the /bin entries to the path, but this seems sloppy and disorganized. Is there a way to backreference the environment variables in /etc/environment?

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• rhythmbox plugin code for hot key not working

  - by Bunny Rabbit

  def activate(self,shell): self.shell = shell self.copy_selected() self.action = gtk.Action ('foo','bar','baz',None) self.activate_id = self.action.connect ('activate', self.call_bk_fn,self.shell) self.action_group = gtk.ActionGroup ('hot_key_action_group') self.action_group.add_action_with_accel (self.action, "<control>E") uim = shell.get_ui_manager () uim.insert_action_group (self.action_group, 0) uim.ensure_update () def call_bk_fn(): print('hello world') i am using the above code in a plugin for rhythmbox ,and here i am trying to register the key ctr+e so that the call_bk_fn gets called whenever the key combination is pressed , but its not working why is that so ?

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• Referencing External Configuration Files in .NET

  Use two separate configuration files to represent settings for development and production environments.

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• Referencing External Configuration Files in .NET

  Use two separate configuration files to represent settings for development and production environments.

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• Referencing External Configuration Files in .NET

  Use two separate configuration files to represent settings for development and production environments.

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• Referencing External Configuration Files in .NET

  Use two separate configuration files to represent settings for development and production environments....Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Good practice about Javascript referencing

  - by AngeloBad

  I am fighting about a web application script optimization. I have an ASP.NET web app that reference jQuery in the master page, and in every child page can reference other library or JavaScript extension. I would like to optimize the application with YUI for .NET. The question is, I should put all the libraries reference in the master page or to compress all the JavaScript code in a single file, or I should create a file for every page that contains only the code useful to the page? Is there any guidance to follow? Thanks!

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