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  • Need an explanation on this code - c#

    - by ltech
    I am getting familiar with C# day by day and I came across this piece of code public static void CopyStreamToStream( Stream source, Stream destination, Action<Stream,Stream,Exception> completed) { byte[] buffer = new byte[0x1000]; AsyncOperation asyncOp = AsyncOperationManager.CreateOperation(null); Action<Exception> done = e => { if (completed != null) asyncOp.Post(delegate { completed(source, destination, e); }, null); }; AsyncCallback rc = null; rc = readResult => { try { int read = source.EndRead(readResult); if (read > 0) { destination.BeginWrite(buffer, 0, read, writeResult => { try { destination.EndWrite(writeResult); source.BeginRead( buffer, 0, buffer.Length, rc, null); } catch (Exception exc) { done(exc); } }, null); } else done(null); } catch (Exception exc) { done(exc); } }; source.BeginRead(buffer, 0, buffer.Length, rc, null); } From this article Article What I fail to follow is that how does the delegate get notified that the copy is done? Say after the copy is done I want to perform an operation on the copied file.

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  • What makes people think that NNs have more computational power than existing models?

    - by Bubba88
    I've read in Wikipedia that neural-network functions defined on a field of arbitrary real/rational numbers (along with algorithmic schemas, and the speculative `transrecursive' models) have more computational power than the computers we use today. Of course it was a page of russian wikipedia (ru.wikipedia.org) and that may be not properly proven, but that's not the only source of such.. rumors Now, the thing that I really do not understand is: How can a string-rewriting machine (NNs are exactly string-rewriting machines just as Turing machines are; only programming language is different) be more powerful than a universally capable U-machine? Yes, the descriptive instrument is really different, but the fact is that any function of such class can be (easily or not) turned to be a legal Turing-machine. Am I wrong? Do I miss something important? What is the cause of people saying that? I do know that the fenomenum of undecidability is widely accepted today (though not consistently proven according to what I've read), but I do not really see a smallest chance of NNs being able to solve that particular problem. Add-in: Not consistently proven according to what I've read - I meant that you might want to take a look at A. Zenkin's (russian mathematician) papers after mid-90-s where he persuasively postulates the wrongness of G. Cantor's concepts, including transfinite sets, uncountable sets, diagonalization method (method used in the proof of undecidability by Turing) and maybe others. Even Goedel's incompletness theorems were proven in right way in only 21-st century.. That's all just to plug Zenkin's work to the post cause I don't know how widespread that knowledge is in CS community so forgive me if that did look stupid. Thank you!

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  • Trap SIGPIPE when trying to write without reader

    - by Matt
    I am trying to implement a named-pipe communication solution in BASH between two processes. The first process runs a script which echo something in a named-pipe: send(){ echo 'something' > $NAMEDPIPE } And the second script is supposed to read the named-pipe via another script which contains: while true;do if read line < $NAMEDPIPE;do someCommands fi done Not that the named pipe has been previously created using the traditional command mkfifo $NAMEDPIPE My problem is that the reader script is not always running so that if the writer script try to write in the named-pipe it stay blocked until a reader connect the pipe. I want to avoid this behavior, and a solution would be to trap a SIGPIPE signal. Indeed, according to man 7 signal is supposed to be send when trying to write in a pipe with no reader. So I changed my red function by: read(){ trap 'echo "SIGPIPE received"' SIGPIPE echo 'something' > $NAMEDPIPE } But when I run the reader script, the script stay blocked, and not "SIGPIPE received" appears... Am I mistaking on the signal mechanism or is there any better solution to my problem ? Thank you for your help.

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  • Selectively disabling WebControl elements

    - by NeilD
    I have an ASP.Net MasterPage with a PlaceHolder element. The contents of the PlaceHolder can be viewed in two modes: read-write, and read-only. To implement read only, I wanted to disable all inputs inside the PlaceHolder. I decided to do this by recursively looping through the controls collection of the PlaceHolder, finding all the ones which inherit from WebControl, and setting control.Enabled = false;. Here's what I originally wrote: private void DisableControls(Control c) { if (c.GetType().IsSubclassOf(typeof(WebControl))) { WebControl wc = c as WebControl; wc.Enabled = false; } //Also disable all child controls. foreach (Control child in c.Controls) { DisableControls(child); } } This worked fine, and all controls are disabled... But then the requirement changed ;) NOW, we want to disable all controls except ones which have a certain CssClass. So, my first attempt at the new version: private void DisableControls(Control c) { if (c.GetType().IsSubclassOf(typeof(WebControl))) { WebControl wc = c as WebControl; if (!wc.CssClass.ToLower().Contains("someclass")) wc.Enabled = false; } //Also disable all child controls. foreach (Control child in c.Controls) { DisableControls(child); } } Now I've hit a problem. If I have (for example) an <ASP:Panel> which contains an <ASP:DropDownList>, and I want to keep the DropDownList enabled, then this isn't working. I call DisableControls on the Panel, and it gets disabled. It then loops through the children, and calls DisableControls on the DropDownList, and leaves it enabled (as intended). However, because the Panel is disabled, when the page renders, everything inside the <div> tag is disabled! Can you think of a way round this? I've thought about changing c.GetType().IsSubclassOf(typeof(WebControl)) to c.GetType().IsSubclassOf(typeof(SomeParentClassThatAllInputElementsInheritFrom)), but I can't find anything appropriate!

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  • NES Programming - Nametables?

    - by Jeffrey Kern
    Hello everyone, I'm wondering about how the NES displays its graphical muscle. I've researched stuff online and read through it, but I'm wondering about one last thing: Nametables. Basically, from what I've read, each 8x8 block in a NES nametable points to a location in the pattern table, which holds graphic memory. In addition, the nametable also has an attribute table which sets a certain color palette for each 16x16 block. They're linked up together like this: (assuming 16 8x8 blocks) Nametable, with A B C D = pointers to sprite data: ABBB CDCC DDDD DDDD Attribute table, with 1 2 3 = pointers to color palette data, with < referencing value to the left, ^ above, and ' to the left and above: 1<2< ^'^' 3<3< ^'^' So, in the example above, the blocks would be colored as so 1A 1B 2B 2B 1C 1D 2C 2C 3D 3D 3D 3D 3D 3D 3D 3D Now, if I have this on a fixed screen - it works great! Because the NES resolution is 256x240 pixels. Now, how do these tables get adjusted for scrolling? Because Nametable 0 can scroll into Nametable 1, and if you keep scrolling Nametable 0 will wrap around again. That I get. But what I don't get is how to scroll the attribute table wraps around as well. From what I've read online, the 16x16 blocks it assigns attributes for will cause color distortions on the edge tiles of the screen (as seen when you scroll left to right and vice-versa in SMB3). The concern I have is that I understand how to scroll the nametables, but how do you scroll the attribute table? For intsance, if I have a green block on the left side of the screen, moving the screen to right should in theory cause the tiles to the right to be green as well until they move more into frame, to which they'll revert to their normal colors.

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  • No transperancy in Bitmap loading from MemoryStream

    - by Jogi Joseph George
    Please see the C# code. When i am writing a Bitmap to a file and read from the file, i am getting the transperancy correctly. using (Bitmap bmp = new Bitmap(2, 2)) { Color col = Color.FromArgb(1, 2, 3, 4); bmp.SetPixel(0, 0, col); bmp.Save("J.bmp"); } using (Bitmap bmp = new Bitmap("J.bmp")) { Color col = bmp.GetPixel(0, 0); // ------------------------------ // Here col.A is 1. This is right. // ------------------------------ } But if I write the Bitmap to a MemoryStream and read from that MemoryStream, the transperancy has been removed. All Alpha values become 255. MemoryStream ms = new MemoryStream(); using (Bitmap bmp = new Bitmap(2, 2)) { Color col = Color.FromArgb(1, 2, 3, 4); bmp.SetPixel(0, 0, col); bmp.Save(ms, ImageFormat.Bmp); } using (Bitmap bmp = new Bitmap(ms)) { Color col = bmp.GetPixel(0, 0); // ------------------------------ // But here col.A is 255. Why? i am expecting 1 here. // ------------------------------ } I wish to save the Bitmap to a MemoryStream and read it back with transperancy. Could you please help me?

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  • My iPhone app ran fine in simulator but crashed on device (iPod touch 3.1.2) test, I got the followi

    - by Mickey Shine
    I was running myapp on an iPod touch and I noticed it missed some libraries. Is that the reason? [Session started at 2010-03-19 15:57:04 +0800.] GNU gdb 6.3.50-20050815 (Apple version gdb-1128) (Fri Dec 18 10:08:53 UTC 2009) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "--host=i386-apple-darwin --target=arm-apple-darwin".tty /dev/ttys007 Loading program into debugger… Program loaded. target remote-mobile /tmp/.XcodeGDBRemote-237-78 Switching to remote-macosx protocol mem 0x1000 0x3fffffff cache mem 0x40000000 0xffffffff none mem 0x00000000 0x0fff none run Running… [Switching to thread 11779] [Switching to thread 11779] sharedlibrary apply-load-rules all (gdb) continue warning: Unable to read symbols for "/Library/MobileSubstrate/MobileSubstrate.dylib" (file not found). 2010-03-19 15:57:18.892 myapp[2338:207] MS:Notice: Installing: com.yourcompany.myapp [myapp] (478.52) 2010-03-19 15:57:19.145 myapp[2338:207] MS:Notice: Loading: /Library/MobileSubstrate/DynamicLibraries/Backgrounder.dylib warning: Unable to read symbols for "/Library/MobileSubstrate/DynamicLibraries/Backgrounder.dylib" (file not found). warning: Unable to read symbols for "/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS3.1.2.sdk/usr/lib/libsubstrate.dylib" (file not found). MS:Warning: message not found [myappAppDelegate applicationWillResignActive:] MS:Warning: message not found [myappAppDelegate applicationDidBecomeActive:] 2010-03-19 15:57:19.550 myapp[2338:207] in FirstViewController 2010-03-19 15:57:20.344 myapp[2338:207] in load table view 2010-03-19 15:57:20.478 myapp[2338:207] in loading splash view 2010-03-19 15:57:22.793 myapp[2338:207] in set interface Program received signal: “0”. warning: check_safe_call: could not restore current frame

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  • Check if TIFF file is complete

    - by Davi
    I have a FileSystemWatcher monitoring a directory that receives TIF files from a scanning device. Its necessary to check if the scanning process is done and then read a multipage TIF file, otherwise, the FileSystemWatcher will raise the event before the file be fully scanned. I have something like: private void OnFileCreated(...) { while(IsFileLocked(path)) Thread.Sleep(time); // OK to read } This is what is happening: - Scanner creates the file - FileSystemWatcher detects the file, but its in use - Scanner reads the first page to the file - Scanner releases the file - My code leaves the while(FileInUse(path)) - My code reads the incomplete file (problem) - Scanner adds more pages to the file Let's say the scanner is scanning 100 pages, then, when "OK to read", the file will be incomplete (99 pages left). So, its necessary to know if the file is complete or not. Maybe waiting some time to see if the file is modified, but this time span can be up to hours, because the scanner can get idle scanning the same TIF. Other solution would be checking some flag in the TIF file that indicates that the file is not complete(I've looked for this but don't found anything).

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  • Parse a CSV file using python (to make a decision tree later)

    - by Margaret
    First off, full disclosure: This is going towards a uni assignment, so I don't want to receive code. :). I'm more looking for approaches; I'm very new to python, having read a book but not yet written any code. The entire task is to import the contents of a CSV file, create a decision tree from the contents of the CSV file (using the ID3 algorithm), and then parse a second CSV file to run against the tree. There's a big (understandable) preference to have it capable of dealing with different CSV files (I asked if we were allowed to hard code the column names, mostly to eliminate it as a possibility, and the answer was no). The CSV files are in a fairly standard format; the header row is marked with a # then the column names are displayed, and every row after that is a simple series of values. Example: # Column1, Column2, Column3, Column4 Value01, Value02, Value03, Value04 Value11, Value12, Value13, Value14 At the moment, I'm trying to work out the first part: parsing the CSV. To make the decisions for the decision tree, a dictionary structure seems like it's going to be the most logical; so I was thinking of doing something along these lines: Read in each line, character by character If the character is not a comma or a space Append character to temporary string If the character is a comma Append the temporary string to a list Empty string Once a line has been read Create a dictionary using the header row as the key (somehow!) Append that dictionary to a list However, if I do things that way, I'm not sure how to make a mapping between the keys and the values. I'm also wondering whether there is some way to perform an action on every dictionary in a list, since I'll need to be doing things to the effect of "Everyone return their values for columns Column1 and Column4, so I can count up who has what!" - I assume that there is some mechanism, but I don't think I know how to do it. Is a dictionary the best way to do it? Would I be better off doing things using some other data structure? If so, what?

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  • Reading bmp file for encrypting and decrypting txt file into it

    - by Shantanu Gupta
    I am trying to read a bmp file in C++(Turbo). But i m not able to print binary stream. I want to encode txt file into it and decrypt it. How can i do this. I read that bmp file header is of 54 byte. But how and where should i append txt file in bmp file. ? I know only Turbo C++, so it would be helpfull for me if u provide solution or suggestion related to topic for the same. int main() { ifstream fr; //reads ofstream fw; // wrrites to file char c; int random; clrscr(); char file[2][100]={"s.bmp","s.txt"}; fr.open(file[0],ios::binary);//file name, mode of open, here input mode i.e. read only if(!fr) cout<<"File can not be opened."; fw.open(file[1],ios::app);//file will be appended if(!fw) cout<<"File can not be opened"; while(!fr) cout<<fr.get(); // error should be here. but not able to find out what error is it fr.close(); fw.close(); getch(); } This code is running fine when i pass txt file in binary mode

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  • Crystal Reports.NET problems accessing FieldObject for page count

    - by Stuart A
    Hi, We're using Crystal Reports.NET that was bundled with VS2005. We have a confirmation booking form letter report that we want to batch print. Generally this prints one page per person on letterhead paper, however occasionally if they've booked lots of courses the letter rolls over to two pages. The second page should not be printed to letterhead paper. Basically, because it's a rare occurance I was just going to print the lot and pause if a particular letter went over 1 page. I.e. Load the report, grab the page count, hollah at the user if it's more than one page otherwise carry on regardless. I have dropped a TotalPageCount on the footer of my report (Which I would supress if it worked!) and then try and read it in my application. Once I've loaded the document I am trying to call report.ReportDefinition.ReportObjects("TotalPageCount1") Which is of type CrystalDecisions.CrystalReports.Engine.FieldObject I cannot seem to get the value out of this for love nor money (nor any amount of cursing and swearing!) I can read any items of type TextObject, but if I append the TotalPageCount to a text field, it shows correctly in the report but then returns "Page count: TotalPageCount" rather than "Page count: 1" for example. Soo, short of going out of my mind, does anyone have any suggestions? Either a way to read the value or a way round it. The printer doesn't have multiple trays, though even if we got one, I'm not sure how to convince crystal to print different pages to different trays. Best regards, Stuart P.S. - is it a sign that the "crystal-reports" tag has a count of 666? :O(

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  • Fake serial communication under Linux

    - by kigurai
    I have an application where I want to simulate the connection between a device and a "modem". The device will be connected to a serial port and will talk to the software modem through that. For testing purposes I want to be able to use a mock software device to test send and receive data. Example Python code device = Device() modem = Modem() device.connect(modem) device.write("Hello") modem_reply = device.read() Now, in my final app I will just pass /dev/ttyS1 or COM1 or whatever for the application to use. But how can I do this in software? I am running Linux and application is written in Python. I have tried making a FIFO (mkfifo ~/my_fifo) and that does work, but then I'll need one FIFO for writing and one for reading. What I want is to open ~/my_fake_serial_port and read and write to that. I have also lpayed with the ptymodule, but can't get that to work either. I can get a master and slave file descriptor from pty.openpty() but trying to read or write to them only causes IOError Bad File Descriptor error message.

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  • How to use data receive event in Socket class?

    - by affan
    I have wrote a simple client that use TcpClient in dotnet to communicate. In order to wait for data messages from server i use a Read() thread that use blocking Read() call on socket. When i receive something i have to generate various events. These event occur in the worker thread and thus you cannot update a UI from it directly. Invoke() can be use but for end developer its difficult as my SDK would be use by users who may not use UI at all or use Presentation Framework. Presentation framework have different way of handling this. Invoke() on our test app as Microstation Addin take a lot of time at the moment. Microstation is single threaded application and call invoke on its thread is not good as it is always busy doing drawing and other stuff message take too long to process. I want my events to generate in same thread as UI so user donot have to go through the Dispatcher or Invoke. Now i want to know how can i be notified by socket when data arrive? Is there a build in callback for that. I like winsock style receive event without use of separate read thread. I also do not want to use window timer to for polling for data. I found IOControlCode.AsyncIO flag in IOControl() function which help says Enable notification for when data is waiting to be received. This value is equal to the Winsock 2 FIOASYNC constant. I could not found any example on how to use it to get notification. If i am write in MFC/Winsock we have to create a window of size(0,0) which was just used for listening for the data receive event or other socket events. But i don't know how to do that in dotnet application.

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  • Flushing writes in buffer of Memory Controller to DDR device

    - by Rohit
    At some point in my code, I need to push the writes in my code all the way to the DIMM or DDR device. My requirement is to ensure the write reaches the row,ban,column of the DDR device on the DIMM. I need to read what I've written to the main memory. I do not want caching to get me the value. Instead after writing I want to fetch this value from main memory(DIMM's). So far I've been using Intel's x86 instruction wbinvd(write back and invalidate cache). However this means the caches and TLB are flushed. Write-back requests go to the main memory. However, there is a reasonable amount of time this data might reside in the write buffer of the Memory Controller( Intel calls it integrated memory controller or IMC). The Memory Controller might take some more time depending on the algorithm that runs in the Memory Controller to handle writes. Is there a way I force all existing or pending writes in the write buffer of the memory controller to the DRAM devices ?? What I am looking for is something more direct and more low-level than wbinvd. If you could point me to right documents or specs that describe this I would be grateful. Generally, the IMC has a several registers which can be written or read from. From looking at the specs for that for the chipset I could not find anything useful. Thanks for taking the time to read this.

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  • Script/plugin to update web page (load next 25 comments) until page fully loaded

    - by Carl
    Brief summary: I need a script/plugin for Firefox that selects the "load next 25 comments" link at the bottom of a web page, until that link is no longer on the page. As you click that link - you get more comments - eventually all of them on the same page. See this web page for an example (there are 1,852 comments): http://www.cnn.com/2010/US/05/16/gulf.oil.spill/index.html#comment-50598247 I have a regular problem with CNN.com. I post comments there. People sometimes reply to them. I check my profile, and see the number of replies, but I can't read them there. I have to follow the link to the original article. The fist set of comments are at the bottom, with a 'load next 25' link at the bottom. There are often hundreds of comments, and sometimes a few thousand. There is no practical way for me to read the replies to my comments. If there's under around 300 hundred, I'll just click that link enough times to see what the replies to my comments are. I need a script/plugin to select that 'load next 25' link until that link is no longer present on the page. Then I could just search for my userid and read the responses.

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  • check properties of two objects for changes

    - by k-hoffmann
    Hi, i have to develop a mechanism to check two object properties for changes. All properties which are needed to check are marked with an attribute. Atm i - read all properties from acutal object via linq - read the corresponding property from old object - fill an own object with the two properties (old and new value) In Code the call to the workerclass looks like this public void CreateHistoryMap(BaseEntity actual, BaseEntity old) { CreateHistoryMap(actualEntity, oldEntity) .ForEach(mapEntry => CreateHistoryEntry(mapEntry), mapEntry => IfChangesDetected(mapEntry)); } CreateHistoryMap builds up the HistoryMapEntry which contains the two properties. CreateHistoryEntry build up the object which is saved to database, the IfChangesDetected check the object for changes. I have to handle own special application types to generate history values to database (like concatinating list values and so on). My problem is now, that i have to read the values of the properties twice - for change detection - and for the concreate CreateHistoryEntry How can i eliminate this problem or how can i implement the change tracking scenario with the nice c# 3.5 features? Thanks a lot.

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  • I need help on this data file to be edited in SOM_PAK format

    - by Mola
    Hi Experts, I am working on Self Organizing Map (SOM) Implementation and i have a microarray dataset which i am trying to read in using some_read_data function, but i keep having an errors when i edit it to have it in SOM_PAK form which is recognise by SOM for reading such as ??? Error using == somtoolbox\som_read_data.m Only 69 vector components on input file data line 1 (dimension is 70) Error in == SomMainFunction at 3 sD = som_read_data('B_r2.txt'); but when i try to read the data without editing which is the original file as shown here: http://rapidshare.com/files/376239367/DLBCL.txt.html It indicates "Data read OK", but i have the following error ??? Error using == unknown Out of memory. Type HELP MEMORY for your options. Error in == somtoolbox\som_bmus.m at 189 Bmus = zeros(dlen,length(which_bmus)); Error in == somvis\somvis_p_matrix.m at 41 [dummy dists] = som_bmus (dat, dat, 2:datlen); Error in == SomMainFunction at 16 [pheight rad_real perc] = somvis_p_matrix(sM,sD); You can get the datafile from here:http://rapidshare.com/files/376239367/DLBCL.txt.html I need someone to help me correct this data for me and put it in SOM_PAK format. I have tried getting it in SOM_PAK format, but it still giving me errors:

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  • gl_FragColor and glReadPixels

    - by chun0216
    I am still trying to read pixels from fragment shader and I have some questions. I know that gl_FragColor returns with vec4 meaning RGBA, 4 channels. After that, I am using glReadPixels to read FBO and write it in data GLubyte *pixels = new GLubyte[640*480*4]; glReadPixels(0, 0, 640,480, GL_RGBA, GL_UNSIGNED_BYTE, pixels); This works fine but it really has speed issue. Instead of this, I want to just read RGB so ignore alpha channels. I tried: GLubyte *pixels = new GLubyte[640*480*3]; glReadPixels(0, 0, 640,480, GL_RGB, GL_UNSIGNED_BYTE, pixels); instead and this didn't work though. I guess it's because gl_FragColor returns 4 channels and maybe I should do something before this? Actually, since my returned image (gl_FragColor) is grayscale, I did something like float gray = 0.5 //or some other values gl_FragColor = vec4(gray,gray,gray,1.0); So is there any efficient way to use glReadPixels instead of using the first 4 channels method? Any suggestion? By the way, this is on opengl es 2.0 code.

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  • How can I handle unread push notifications in iOS?

    - by Bartserk
    I have a iOS 5.1 application that registers to the APNS service to receive notifications. The register is successful and I receive the notifications correctly. The problem comes when I try to handle the notifications. Once the application is running, the method didReceiveRemoteNotification in the AppDelegate is called correctly and so the notification is handled as intended. This, however, only happens when the application is running on the foreground. However, when the application is running on the background or is simply stopped, that method is not called. I've read that you should add some lines to the method didFinishLaunchingWithOptions method to obtain the notification from the userInfo dictionary, and handle it. This works just fine, but ONLY when the application is opened by clicking on the notification at the Notification Center. This means that if you open the application by clicking on its badge, or simply by changing context if you were running it on the background, the app never realises that a notification came in. Additionally, if more than one notification was received, we can only handle one of them at once by clicking on the Notification Center, which is a pain :-) Is there any way to read the pending notifications in the Notification Center? I know there is a way to flush them using the method cancelAllLocalNotifications but I haven't found a way to just read them. And I really need to handle all of them. I thought of implementing a communication protocol with the third-party notification server to retrieve the information again when the application comes to the foreground, but since the information is already in the operating system I would find it strange if it's impossible to access it somehow. So, does anybody know a way to do it? Thanks in advance.

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  • how does MySQL implement the "group by"?

    - by user188916
    I read from the MySQL Reference Manual and find that when it can take use of index,it just do index scan,other it will create tmp tables and do things like filesort. And I also read from other article that the "Group By" result will sort by group by columns by default,if "order by null" clause added,it won't don filesort. The difference can be found from the "explain ..." clause. so my problem is:what is the difference between "group by" clause that with "order by null" and which doesn't have? I try to use profiling to see what mysql do on the background,and only see result like: result for group clause without order by null: |preparing | 0.000016 | | Creating tmp table | 0.000048 | | executing | 0.000009 | | Copying to tmp table | 0.000109 | **| Sorting result | 0.000023 |** | Sending data | 0.000027 | result for clause with "order by null": preparing | 0.000016 | | Creating tmp table | 0.000052 | | executing | 0.000009 | | Copying to tmp table | 0.000114 | | Sending data | 0.000028 | So I guess what MySQL do when the "order by null" added,it does not use filesort algorithm,maybe when it creates the tmp table,it uses index as well,and then use the index to do group by operation,when completed,it just read result from the table rows and does not sort the result. But my original opinion is that MySQL can use quicksort to sort the items and then do group by,so the result will be sorted as well. Any opinion appreciated,thanks.

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  • Using child visitor in C#

    - by Thomas Matthews
    I am setting up a testing component and trying to keep it generic. I want to use a generic Visitor class, but not sure about using descendant classes. Example: public interface Interface_Test_Case { void execute(); void accept(Interface_Test_Visitor v); } public interface Interface_Test_Visitor { void visit(Interface_Test_Case tc); } public interface Interface_Read_Test_Case : Interface_Test_Case { uint read_value(); } public class USB_Read_Test : Interface_Read_Test_Case { void execute() { Console.WriteLine("Executing USB Read Test Case."); } void accept(Interface_Test_Visitor v) { Console.WriteLine("Accepting visitor."); } uint read_value() { Console.WriteLine("Reading value from USB"); return 0; } } public class USB_Read_Visitor : Interface_Test_Visitor { void visit(Interface_Test_Case tc) { Console.WriteLine("Not supported Test Case."); } void visit(Interface_Read_Test_Case rtc) { Console.WriteLine("Not supported Read Test Case."); } void visit(USB_Read_Test urt) { Console.WriteLine("Yay, visiting USB Read Test case."); } } // Code fragment USB_Read_Test test_case; USB_Read_Visitor visitor; test_case.accept(visitor); What are the rules the C# compiler uses to determine which of the methods in USB_Read_Visitor will be executed by the code fragment? I'm trying to factor out dependencies of my testing component. Unfortunately, my current Visitor class contains visit methods for classes not related to the testing component. Am I trying to achieve the impossible?

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  • visual studio 2008 (VB)

    - by Ousman
    hello guys, Am writing a programming with visual basic 2008 and i want the programme to be able to read and loop through a text file line by line and showing the event of the loop on a textbox or label until a button is press and the loop will stop on any number that happend to be at the loop event and when a button is press again the loop will continue from where it starts. this is my codes below and having problem with it and any help will be really great. tanks ==========================my codes======================= Imports System.IO '========================================================================================== Public Class Form1 '====================================================================================== 'Dim nFileNum As Integer = FreeFile() ' Get a free file number Dim strFileName As String = "C:\scb.txt" Dim objFilename As FileStream = New FileStream(strFileName, FileMode.Open, FileAccess.Read, FileShare.Read) Dim objFileRead As StreamReader = New StreamReader(objFilename) 'Dim lLineCount As Long 'Dim sNextLine As String '====================================================================================== '======================================================================================== Private Sub btStart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btStart.Click Try If objFileRead.ReadLine = Nothing Then MsgBox("No Accounts Available to show!", MsgBoxStyle.Information, MsgBoxStyle.DefaultButton2 = MsgBoxStyle.OkOnly) Return Else Do While (objFileRead.Peek() > -1) Loop lblAccounts.Text = objFileRead.ReadLine() 'objFileRead.Close() 'objFilename.Close() End If Catch ex As Exception MessageBox.Show(ex.Message) Finally 'objFileRead.Close() 'objFilename.Close() End Try End Sub Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load End Sub End Class

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  • While loop not reading in the last item

    - by Gandalf StormCrow
    I'm trying to read in a multi line string then split it then print it .. here is the string : 1T1b5T!1T2b1T1b2T!1T1b1T2b2T!1T3b1T1b1T!3T3b1T!1T3b1T1b1T!5T1*1T 11X21b1X 4X1b1X When I split the string with ! I get this without the last line string : 1T1b5T 1T1b5T1T2b1T1b2T 1T2b1T1b2T1T1b1T2b2T 1T1b1T2b2T1T3b1T1b1T 1T3b1T1b1T3T3b1T 3T3b1T1T3b1T1b1T 1T3b1T1b1T5T1*1T 5T1*1T11X21b1X 11X21b1X Here is my code : import java.io.BufferedInputStream; import java.util.Scanner; public class Main { public static void main(String args[]) { Scanner stdin = new Scanner(new BufferedInputStream(System.in)); while (stdin.hasNext()) { for (String line : stdin.next().split("!")) { System.out.println(line); for (int i = 0; i < line.length(); i++) { System.out.print(line.charAt(i)); } } } } } Where did I make the mistake, why is not reading in the last line? After I read in all lines properly I should go trough each line if I encounter number I should print the next char the n times the number I just read, but that is long way ahead first I need help with this. Thank you UPDATE : Here is how the output should look like : 1T1b5T 1T2b1T1b2T 1T1b1T2b2T 1T3b1T1b1T 3T3b1T 1T3b1T1b1T 5T1*1T 11X21b1X 4X1b1X Here is a solution in C(my friend solved it not me), but I'd stil wanted to do it in JAVA : #include <stdio.h> int main (void) { char row[134]; for (;fgets (row,134,stdin)!=NULL;) { int i,j=0; for (i=0;row[i]!='\0';i++) { if (row[i]<='9'&&row[i]>='1') j+=(row[i]-'0'); else if ((row[i]<='Z'&&row[i]>='A')||row[i]=='*') for (;j;j--) printf ("%c",row[i]); else if (row[i]=='b') for (;j;j--) printf (" "); else if (row[i]=='!'||row[i]=='\n') printf ("\n"); } } return 0; }

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  • Simple binary File I/O problem with cstdio(c++)

    - by Atilla Filiz
    The c++ program below fails to read the file. I know using cstdio is not good practice but that what I am used to and it should work anyway. $ ls -l l.uyvy -rw-r--r-- 1 atilla atilla 614400 2010-04-24 18:11 l.uyvy $ ./a.out l.uyvy Read 0 bytes out of 614400, possibly wrong file code: #include<cstdio> int main(int argc, char* argv[]) { FILE *fp; if(argc<2) { printf("usage: %s <input>\n",argv[0]); return 1; } fp=fopen(argv[1],"rb"); if(!fp) { printf("erör, cannot open %s for reading\n",argv[1]); return -1; } int bytes_read=fread(imgdata,1,2*IMAGE_SIZE,fp); //2bytes per pixel fclose(fp); if(bytes_read < 2*IMAGE_SIZE) { printf("Read %d bytes out of %d, possibly wrong file\n", bytes_read, 2*IMAGE_SIZE); return -1; } return 0; }

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  • IndexOutOfRangeException when a stream is a multiple of the buffer size

    - by dnord
    I don't have a lot of experience with streams and buffers, but I'm having to do it for a project, and I'm stuck on an exception being thrown when the stream I'm reading is a multiple of the buffer size I've chosen. Let me show you: My code starts by reading bufferSize (100, let's say) bytes from the stream: numberOfBytesRead = DataReader.GetBytes(0, index, output, 0, bufferSize); Then, I loop through a while loop: while (numberOfBytesRead == bufferSize) { BufferWriter.Write(output); BufferWriter.Flush(); index += bufferSize; numberOfBytesRead = DataReader.GetBytes(0, index, output, 0, bufferSize); } ... and, once we get to a non-bufferSize read, we know we've hit the end of the stream and can move on. But if the bufferSize is 100, and the stream is 200, we'll read positions 0-99, 100-199, and then the attempt to read 200-299 errors out. I'd like it if it returned 0, but it throws an error. What I'm doing to handle that is, well, a try-catch: catch (System.IndexOutOfRangeException) numberOfBytesRead = 0; ...which ends the loop, and successfully finishes the thing, but we all know I don't want to control code flow with error handling. Is there a better (more standard?) way to handle stream reading when the stream length is unknown? This seems like a small wrinkle in a fairly reasonable strategy for reading streams, but I just don't know if I've got it wrong or what. The specifics of this (which I've cleaned up a little bit for posting) are a MySqlDataReader hitting a LARGEBLOB column. It's working whenever the buffer is larger than the number of returned bytes, or when the number of returned bytes is not a multiple of bufferSize. Because we don't, in that case, throw an IndexOutOfRangeException.

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