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  • implementing UIActivityIndicatorView while NSData dataWithContentsOfURL is downloading

    - by padatronic
    Hi people, I am downloading an mp3 using NSData dataWithContentsOfURL:url. This takes a while and while the file is downloading the application hangs. I want to handle well and ideal would like to show the download progress but can't find methods for this. It is in a UIViewController and I have made a first attempt by putting in a UIActivityIndicatorView and start it spinning before I start the download, then stop it spinning after but nothing appears. So my question really is please could someone tell me what the best way to handle this is? Thanks so much

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  • Help needed implementing a web based file management system with a file hierarchy system, help neede

    - by molleman
    Hello i am trying to create a web application that will allow users to upload files online, i am using gwt while using hibernate for database communication, i am able to upload file to a server , and store them on the server. but what i want is to associate the files with a user. i want the user to be able to create folders and store a file in sub folders. my logic was to use the composite pattern to store folders and fileLocations with a user but i am am finding it difficult to implement this so i can show the files and folders within a gwt tree. what would be the best way to implement a hierarchy of folders and information of the location of a file so it could be displayed in a gwt tree? what i did have was a User would hold a reference to a root folder and then each sub folder could hold folders or fileLocations. i used the composite pattern to implement the file hierarchy, but when i want to display a the contents of a folder i need a for loop for each list. so i could a folder within a folder within a folder that would need 3 for loops to show the contents of my folders. What is the best way to implement this file management system. so what do you guys think?

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  • Implementing Naïve Bayes algorithm in Java - Need some guidance

    - by techventure
    hello stackflow people As a School assignment i'm required to implement Naïve Bayes algorithm which i am intending to do in Java. In trying to understand how its done, i've read the book "Data Mining - Practical Machine Learning Tools and Techniques" which has a section on this topic but am still unsure on some primary points that are blocking my progress. Since i'm seeking guidance not solution in here, i'll tell you guys what i thinking in my head, what i think is the correct approach and in return ask for correction/guidance which will very much be appreciated. please note that i am an absolute beginner on Naïve Bayes algorithm, Data mining and in general programming so you might see stupid comments/calculations below: The training data set i'm given has 4 attributes/features that are numeric and normalized(in range[0 1]) using Weka (no missing values)and one nominal class(yes/no) 1) The data coming from a csv file is numeric HENCE * Given the attributes are numeric i use PDF (probability density function) formula. + To calculate the PDF in java i first separate the attributes based on whether they're in class yes or class no and hold them into different array (array class yes and array class no) + Then calculate the mean(sum of the values in row / number of values in that row) and standard divination for each of the 4 attributes (columns) of each class + Now to find PDF of a given value(n) i do (n-mean)^2/(2*SD^2), + Then to find P( yes | E) and P( no | E) i multiply the PDF value of all 4 given attributes and compare which is larger, which indicates the class it belongs to In temrs of Java, i'm using ArrayList of ArrayList and Double to store the attribute values. lastly i'm unsure how to to get new data? Should i ask for input file (like csv) or command prompt and ask for 4 values? I'll stop here for now (do have more questions) but I'm worried this won't get any responses given how long its got. I will really appreciate for those that give their time reading my problems and comment.

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  • Benefit for implementing OAuth

    - by zfranciscus
    Hi, I am just wondering from a webservice provider point of view what is the benefit of asking users to create an account or login using 3rd party web service provider e.g: Twitter or facebook. Wouldn't it be easier to ask the user to provide their twitter or facebook login and use that to pull the user's twitter or facebook data. I can understand the benefit of using From user point of view using OAuth provide security. It is safer to use OAuth than giving some one the internet our twitter or facebook login credential. But some how I can't figure out the benefit from the web service point of view. Thank you. Cheers

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  • Implementing an async "read all currently available data from stream" operation

    - by Jon
    I recently provided an answer to this question: C# - Realtime console output redirection. As often happens, explaining stuff (here "stuff" was how I tackled a similar problem) leads you to greater understanding and/or, as is the case here, "oops" moments. I realized that my solution, as implemented, has a bug. The bug has little practical importance, but it has an extremely large importance to me as a developer: I can't rest easy knowing that my code has the potential to blow up. Squashing the bug is the purpose of this question. I apologize for the long intro, so let's get dirty. I wanted to build a class that allows me to receive input from a console's standard output Stream. Console output streams are of type FileStream; the implementation can cast to that, if needed. There is also an associated StreamReader already present to leverage. There is only one thing I need to implement in this class to achieve my desired functionality: an async "read all the data available this moment" operation. Reading to the end of the stream is not viable because the stream will not end unless the process closes the console output handle, and it will not do that because it is interactive and expecting input before continuing. I will be using that hypothetical async operation to implement event-based notification, which will be more convenient for my callers. The public interface of the class is this: public class ConsoleAutomator { public event EventHandler<ConsoleOutputReadEventArgs> StandardOutputRead; public void StartSendingEvents(); public void StopSendingEvents(); } StartSendingEvents and StopSendingEvents do what they advertise; for the purposes of this discussion, we can assume that events are always being sent without loss of generality. The class uses these two fields internally: protected readonly StringBuilder inputAccumulator = new StringBuilder(); protected readonly byte[] buffer = new byte[256]; The functionality of the class is implemented in the methods below. To get the ball rolling: public void StartSendingEvents(); { this.stopAutomation = false; this.BeginReadAsync(); } To read data out of the Stream without blocking, and also without requiring a carriage return char, BeginRead is called: protected void BeginReadAsync() { if (!this.stopAutomation) { this.StandardOutput.BaseStream.BeginRead( this.buffer, 0, this.buffer.Length, this.ReadHappened, null); } } The challenging part: BeginRead requires using a buffer. This means that when reading from the stream, it is possible that the bytes available to read ("incoming chunk") are larger than the buffer. Remember that the goal here is to read all of the chunk and call event subscribers exactly once for each chunk. To this end, if the buffer is full after EndRead, we don't send its contents to subscribers immediately but instead append them to a StringBuilder. The contents of the StringBuilder are only sent back whenever there is no more to read from the stream. private void ReadHappened(IAsyncResult asyncResult) { var bytesRead = this.StandardOutput.BaseStream.EndRead(asyncResult); if (bytesRead == 0) { this.OnAutomationStopped(); return; } var input = this.StandardOutput.CurrentEncoding.GetString( this.buffer, 0, bytesRead); this.inputAccumulator.Append(input); if (bytesRead < this.buffer.Length) { this.OnInputRead(); // only send back if we 're sure we got it all } this.BeginReadAsync(); // continue "looping" with BeginRead } After any read which is not enough to fill the buffer (in which case we know that there was no more data to be read during the last read operation), all accumulated data is sent to the subscribers: private void OnInputRead() { var handler = this.StandardOutputRead; if (handler == null) { return; } handler(this, new ConsoleOutputReadEventArgs(this.inputAccumulator.ToString())); this.inputAccumulator.Clear(); } (I know that as long as there are no subscribers the data gets accumulated forever. This is a deliberate decision). The good This scheme works almost perfectly: Async functionality without spawning any threads Very convenient to the calling code (just subscribe to an event) Never more than one event for each time data is available to be read Is almost agnostic to the buffer size The bad That last almost is a very big one. Consider what happens when there is an incoming chunk with length exactly equal to the size of the buffer. The chunk will be read and buffered, but the event will not be triggered. This will be followed up by a BeginRead that expects to find more data belonging to the current chunk in order to send it back all in one piece, but... there will be no more data in the stream. In fact, as long as data is put into the stream in chunks with length exactly equal to the buffer size, the data will be buffered and the event will never be triggered. This scenario may be highly unlikely to occur in practice, especially since we can pick any number for the buffer size, but the problem is there. Solution? Unfortunately, after checking the available methods on FileStream and StreamReader, I can't find anything which lets me peek into the stream while also allowing async methods to be used on it. One "solution" would be to have a thread wait on a ManualResetEvent after the "buffer filled" condition is detected. If the event is not signaled (by the async callback) in a small amount of time, then more data from the stream will not be forthcoming and the data accumulated so far should be sent to subscribers. However, this introduces the need for another thread, requires thread synchronization, and is plain inelegant. Specifying a timeout for BeginRead would also suffice (call back into my code every now and then so I can check if there's data to be sent back; most of the time there will not be anything to do, so I expect the performance hit to be negligible). But it looks like timeouts are not supported in FileStream. Since I imagine that async calls with timeouts are an option in bare Win32, another approach might be to PInvoke the hell out of the problem. But this is also undesirable as it will introduce complexity and simply be a pain to code. Is there an elegant way to get around the problem? Thanks for being patient enough to read all of this. Update: I definitely did not communicate the scenario well in my initial writeup. I have since revised the writeup quite a bit, but to be extra sure: The question is about how to implement an async "read all the data available this moment" operation. My apologies to the people who took the time to read and answer without me making my intent clear enough.

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  • ClassNotFoundException error in implementing Bayesian algorithm in Apache Mahout on Hadoop

    - by Shweta
    Hi, I have a problem in executing the Bayesian algorithm in Mahout. I built it with Maven and the job file is in target directory. When run from terminal using hadoop, I'm getting the ClassNotFoundException error. What should be done? $HADOOP_HOME/bin/hadoop jar mahout-core-0.3-SNAPSHOT.job org.apache.mahout.classifier.bayes.mapreduce.bayes.bayesdriver -i test -o output Exception in thread "main" java.lang.ClassNotFoundException: org.apache.mahout.classifier.bayes.mapreduce.bayes.bayesdriver at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:307) at java.lang.ClassLoader.loadClass(ClassLoader.java:252) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:247) at org.apache.hadoop.util.RunJar.main(RunJar.java:149)

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  • Java Implementing htonl

    - by Hamza Yerlikaya
    I am communicating with a server, each message sent to the server has to be padded with the length of the message, unsigned int len = htonl(msg.size()); In C running the length through htonl and padding the message works, in Java AFAIK byte order is already in network order so I assumed all I have to do is write the string length before the message to the stream, but this does not work am I missing something? stream.write(msg.length()); stream.write(msg.getBytes()); Stream is an OutputStream.

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  • Need help implementing simple socket server using GIOService (GLib, Glib-GIO)

    - by Mark Renouf
    I'm learning the basics of writing a simple, efficient socket server using GLib. I'm experimenting with GSocketService. So far I can only seem to accept connections but then they are immediately closed. From the docs I can't figure out what step I am missing. I'm hoping someone can shed some light on this for me. When running the following: # telnet localhost 4000 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. Connection closed by foreign host. # telnet localhost 4000 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. Connection closed by foreign host. # telnet localhost 4000 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. Connection closed by foreign host. Output from the server: # ./server New Connection from 127.0.0.1:36962 New Connection from 127.0.0.1:36963 New Connection from 127.0.0.1:36965 Current code: /* * server.c * * Created on: Mar 10, 2010 * Author: mark */ #include <glib.h> #include <gio/gio.h> gchar *buffer; gboolean network_read(GIOChannel *source, GIOCondition cond, gpointer data) { GString *s = g_string_new(NULL); GError *error; GIOStatus ret = g_io_channel_read_line_string(source, s, NULL, &error); if (ret == G_IO_STATUS_ERROR) g_error ("Error reading: %s\n", error->message); else g_print("Got: %s\n", s->str); } gboolean new_connection(GSocketService *service, GSocketConnection *connection, GObject *source_object, gpointer user_data) { GSocketAddress *sockaddr = g_socket_connection_get_remote_address(connection, NULL); GInetAddress *addr = g_inet_socket_address_get_address(G_INET_SOCKET_ADDRESS(sockaddr)); guint16 port = g_inet_socket_address_get_port(G_INET_SOCKET_ADDRESS(sockaddr)); g_print("New Connection from %s:%d\n", g_inet_address_to_string(addr), port); GSocket *socket = g_socket_connection_get_socket(connection); gint fd = g_socket_get_fd(socket); GIOChannel *channel = g_io_channel_unix_new(fd); g_io_add_watch(channel, G_IO_IN, (GIOFunc) network_read, NULL); return TRUE; } int main(int argc, char **argv) { g_type_init(); GSocketService *service = g_socket_service_new(); GInetAddress *address = g_inet_address_new_from_string("127.0.0.1"); GSocketAddress *socket_address = g_inet_socket_address_new(address, 4000); g_socket_listener_add_address(G_SOCKET_LISTENER(service), socket_address, G_SOCKET_TYPE_STREAM, G_SOCKET_PROTOCOL_TCP, NULL, NULL, NULL); g_object_unref(socket_address); g_object_unref(address); g_socket_service_start(service); g_signal_connect(service, "incoming", G_CALLBACK(new_connection), NULL); GMainLoop *loop = g_main_loop_new(NULL, FALSE); g_main_loop_run(loop); }

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  • Error in Implementing WS Security web service in WebLogic 10.3

    - by Chris
    Hi, I am trying to develop a JAX WS web service with WS-Security features in WebLogic 10.3. I have used the ant tasks WSDLC, JWSC and ClientGen to generate skeleton/stub for this web service. I have two keystores namely WSIdentity.jks and WSTrust.jks which contains the keys and certificates. One of the alias of WSIdentity.jks is "ws02p". The test client has the following code to invoke the web service: SecureSimpleService service = new SecureSimpleService(); SecureSimplePortType port = service.getSecureSimplePortType(); List credProviders = new ArrayList(); CredentialProvider cp = new ClientBSTCredentialProvider( "E:\\workspace\\SecureServiceWL103\\keystores\\WSIdentity.jks", "webservice", "ws01p","webservice"); credProviders.add(cp); string endpointURL="http://localhost:7001/SecureSimpleService/SecureSimpleService"; BindingProvider bp = (BindingProvider)port; Map requestContext = bp.getRequestContext(); requestContext.put(BindingProvider.ENDPOINT_ADDRESS_PROPERTY, endpointURL); requestContext.put(WSSecurityContext.CREDENTIAL_PROVIDER_LIST,credProviders); requestContext.put(WSSecurityContext.TRUST_MANAGER, new TrustManager() { public boolean certificateCallback(X509Certificate[] chain, int validateErr) { // Put some custom validation code in here. // Just return true for now return true; } }); SignResponse resp1 = new SignResponse(); resp1 = port.echoSignOnlyMessage("hello sign"); System.out.println("Result: " + resp1.getMessage()); When I trying to invoke this web servcie using this test client I am getting the error "Invalid signing policy" with the following stack trace: *[java] weblogic.wsee.security.wss.policy.SecurityPolicyArchitectureException: Invalid signing policy [java] at weblogic.wsee.security.wss.plan.SecurityPolicyBlueprintDesigner.verifyPolicy(SecurityPolicyBlueprintDesigner.java:786) [java] at weblogic.wsee.security.wss.plan.SecurityPolicyBlueprintDesigner.designOutboundBlueprint(SecurityPolicyBlueprintDesigner.java:136) Am I missing any configuration settings in WebLogic admin console or is it do with something else. Thanks in advance.

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  • Python: Implementing slicing in __getitem__

    - by nicotine
    I am trying to implement slice functionality for a class I am making that creates a vector representation. I have this code so far, which I believe will properly implement the slice but whenever I do a call like v[4] where v is a vector python returns an error about not having enough parameters. So I am trying to figure out how to define the getitem class to handle both plain indexes and slicing. def __getitem__(self, start, stop, step): indx = start if stop == None: end = start + 1 else: end = stop if step == None: stride = 1 else: stride = step return self.__data[indx:end:stride]

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  • Implementing Projectile Motion

    - by DMan
    I've scored the internet for sources and have found a lot of useful information, but they are math sites trying to tell me how to solve what angle an object has to be at to reach y location. However, I'm trying to run a simulation, and haven't found any solid equations that can be implemented to code to simulate a parabolic curve. Can those with some knowledge of physics help me on this?

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  • Programmatically implementing an interface that combines some instances of the same interface in var

    - by namin
    What is the best way to implement an interface that combines some instances of the same interface in various specified ways? I need to do this for multiple interfaces and I want to minimize the boilerplate and still achieve good efficiency, because I need this for a critical production system. Here is a sketch of the problem. Abstractly, I have a generic combiner class which takes the instances and specify the various combinators: class Combiner<I> { I[] instances; <T> T combineSomeWay(InstanceMethod<I,T> method) { // ... method.call(instances[i]) ... combined in some way ... } // more combinators } Now, let's say I want to implement the following interface among many others: Interface Foo { String bar(int baz); } I want to end up with code like this: class FooCombiner implements Foo { Combiner<Foo> combiner; @Override public String bar(final int baz) { return combiner.combineSomeWay(new InstanceMethod<Foo, String> { @Override public call(Foo instance) { return instance.bar(baz); } }); } } Now, this can quickly get long and winded if the interfaces have lots of methods. I know I could use a dynamic proxy from the Java reflection API to implement such interfaces, but method access via reflection is hundred times slower. So what are the alternatives to boilerplate and reflection in this case?

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  • Implementing IComparable<NotSelf>

    - by Luc Touraille
    This might be a trivial question, but I didn't find any information about this: is it "harmful" or considered bad practice to make a type T implement IComparable<S> (T and S being two different types)? Example: class Foo : IComparable<int> { public int CompareTo(int other) { if (other < i) return -1; if (other > i) return 1; return 0; } private int i; } Should this kind of code be avoided, and if yes, why?

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  • Problem with implementing removeAll for List of custom object

    - by Jay
    Hello everyone, I have a scenario in my code where I need to compare two Lists and remove from the first list, objects which are present in the second list. Akin to how the "removeAll" object works for List. Since my List is created on a custom object, the removeAll method won't work for me. I have tried various methods to make this work: - implemented equals() and hashCode for the custom object comprising the list - implemented the Comparable Interface for the custom object - implemented the Comparator Interface for the custom object I've even tried using the Apache Common's CollectionUtils and ListUtils methods (subtract, intersect, removeAll). None seem to work. I understand I will perhaps need to write some custom removal code. But not sure how to go about doing that. Any pointers helping me move in the right direction will be really appreciated. Thanks, Jay

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  • Implementing database redundancy with sharded tables

    - by ensnare
    We're looking to implement load balancing by horizontally sharding our tables across a cluster of servers. What are some options to implement live redundancy should a server fail? Would it be effective to do (2) INSERTS instead of one ... one to the target shard, and another to a secondary shard which could be accessed should the primary shard not respond? Or is there a better way? Thanks.

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  • Implementing a customized drawable in Android

    - by Girish
    Hi , I was trying to get hold of 2D graphics in Android. As a example i want to implement a custom drawable and show it in my Activity I have defined a customized drawable by extending from Android drawable as mentioned below myDrawable extends Drawable { private static final String TAG = myDrawable.class.getSimpleName(); private ColorFilter cf; @Override public void draw(Canvas canvas) { //First you define a colour for the outline of your rectangle Paint rectanglePaint = new Paint(); rectanglePaint.setARGB(255, 255, 0, 0); rectanglePaint.setStrokeWidth(2); rectanglePaint.setStyle(Style.FILL); //Then create yourself a Rectangle RectF rectangle = new RectF(15.0f, 50.0f, 55.0f, 75.0f); //in pixels Log.d(TAG,"On Draw method"); // TODO Auto-generated method stub Paint paintHandl = new Paint(); // paintHandl.setColor(0xaabbcc); paintHandl.setARGB(125, 234, 213, 34 ); RectF rectObj = new RectF(5,5,25,25); canvas.drawRoundRect(rectangle, 0.5f, 0.5f, rectanglePaint); } @Override public int getOpacity() { // TODO Auto-generated method stub return 100; } @Override public void setAlpha(int alpha) { // TODO Auto-generated method stub } @Override public void setColorFilter(ColorFilter cf) { // TODO Auto-generated method stub this.cf = cf; } } I am trying to get this displayed in my activity, as shown below public class custDrawable extends Activity { /** Called when the activity is first created. */ LinearLayout layObj = null; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); layObj = (LinearLayout) findViewById(R.id.parentLay); ImageView imageView = (ImageView) findViewById(R.id.icon2); myDrawable myDrawObj = new myDrawable(); imageView.setImageDrawable(myDrawObj); imageView.invalidate(); // layObj.addView(myDrawObj, params); } } But when i run the app i see no rectangle on the activity, can anyone help me out? Where am i going wrong?

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  • Implementing the outside application „openedFileView“ in c# Project

    - by case23
    I work on a application where i want to find out which files on my filesystem is used by a Process. After trying around with the System.Diagnostics.Process class, and didn´t get the resulst i wanted i find the application called OpenedFileView from Nirsoft. http://www.nirsoft.net/utils/opened_files_view.html Basically it does exactly what i want but i have some problems with the implimication in my project. The option wich “OpenedFileView” gives you is to start it with some arguments that it creates you an txt file with all the information i want. But for my case i want to whach the processes in realtime, and if i start the application repetitively i always have the hourglass at my mouse cursor. So after this i tryed some ways to get rid of it, tryed out to put it in a BackgroundWorker Thread. But this changed nothing at all. I also looked for a way to force the Process not to exit, and sending new arguments to it, but this also didn´t worked. So is there any way to use this application in the way I want, or does this didn´t work at all? I hope somebody can help me either with getting away this annoying mouse cursor hourglass, or with a better implimication of this application so i can use it in realtime! Thanks alot! private void start() { _openedFileView = new Process(); _openedFileView.StartInfo.FileName = "pathToApp\\OpenedFilesView.exe"; _openedFileView.EnableRaisingEvents = true; _openedFileView.Exited += new EventHandler(myProcess_Exited); _openedFileView.StartInfo.Arguments = "/scomma pathToOutputFile"; _openedFileView.Start(); } private void myProcess_Exited(object sender, System.EventArgs e) { start(); }

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  • Difference between implementing an interface and applying an attribute in C#

    - by RemotecUk
    This might be a stupid question but Ill ask anyway, I was reading "OOP Demystified: A Self-Teaching Guide by Jim Keogh and Mario Giannini" chapter 11 which covers interfaces. The examples in this book are C++. I noticed that C++ uses ISerializable to make a class serializable which you would implement where as in C# you just attribute the class with the [Serializable] attribute. What is the key difference here? Is it that with an interface you must provide the implementation where as if you attribute something the compiler will work out the implementation for you? I guess that with the [Serializable] attribute the .Net framework uses reflection to make the serialized object from the actual object. That said is it possible in that case to have an [Disposable] attribute or using my theory above the framework wont know how to actually dispose of an object hence you have to do it yourself? Would be grateful for a clarification. Thanks.

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