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  • Memory management, and async operations: when does an object become nil?

    - by Kenny Winker
    I have a view that will be displaying downloaded images and text. I'd like to handle all the downloading asynchronously using ASIHTTPRequest, but I'm not sure how to go about notifying the view when downloads are finished... If I pass my view controller as the delegate of the ASIHTTPRequest, and then my view is destroyed (user navigates away) will it fail gracefully when it tries to message my view controller because the delegate is now nil? i.e. if i do this: UIViewController *myvc = [[UIViewController alloc] init]; request.delegate = myvc; [myvc release]; Do myvc, and request.delegate now == a pointer to nil? This is the problem with being self-taught... I'm kinda fuzzy on some basic concepts. Other ideas of how to handle this are welcome.

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  • TVirtualStringTree - resetting non-visual nodes and memory comsumption

    - by Remy Lebeau - TeamB
    I have an app that loads records from a binary log file and displays them in a virtual TListView. There are potentially millions of records in a file, and the display can be filtered by the user, so I do not load all of the records in memory at one time, and the ListView item indexes are not a 1-to-1 relation with the file record offsets (List item 1 may be file record 100, for instance). I use the ListView's OnDataHint event to load records for just the items the ListView is actually interested in. As the user scrolls around, the range specified by OnDataHint changes, allowing me to free records that are not in the new range, and allocate new records as needed. This works fine, speed is tolerable, and the memory footprint is very low. I am currently evaluating TVirtualStringTree as a replacement for the TListView, mainly because I want to add the ability to expand/collapse records that span multiple lines (I can fudge it with the TListView by incrementing/decrementing the item count dynamically, but this is not as straight forward as using a real tree). For the most part, I have been able to port the TListView logic and have everything work as I need. I notice that TVirtualStringTree's virtual paridigm is vastly different, though. It does not have the same kind of OnDataHint functionality that TListView does (I can use the OnScroll event to fake it, which allows my memory buffer logic to continue working), and I can use the OnInitializeNode event to associate nodes with records that are allocated. However, once a tree node is initialized, it sees that it remains initialized for the lifetime of the tree. That is not good for me. As the user scrolls around and I remove records from memory, I need to reset those non-visual nodes without removing them from the tree completely, or losing their expand/collapse states. When the user scrolls them back into view, I can re-allocate the records and re-initialize the nodes. Basically, I want to make TVirtualStringTree act as much like TListView as possible, as far as its virtualization is concerned. I have seen that TVirtualStringTree has a ResetNode() method, but I encounter various errors whenever I try to use it. I must be using it wrong. I also thought of just storing a data pointer inside each node to my record buffers, and I allocate and free memory, update those pointers accordingly. The end effect does not work so well, either. Worse, my largest test log file has ~5 million records in it. If I initialize the TVirtualStringTree with that many nodes at one time (when the log display is unfiltered), the tree's internal overhead for its nodes takes up a whopping 260MB of memory (without any records being allocated yet). Whereas with the TListView, loading the same log file and all the memory logic behind it, I can get away with using just a few MBs. Any ideas?

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  • How long should it take for someone to be able to type code from memory?

    - by LordSnoutimus
    Hi, I understand that this question could be answered with a simple sentence and that it may be viewed as subjective, however, I am a young student who is interested in pursuing a career in programming and wondered how long it took some of you to get to the level of experience you are now?. I ask this because I am currently working on building an application in Java on the Android platform and it bothers me that I am constantly having to look up how to write a certain section of code in my application such as writing to a database, or how the if loop should be structured. My question really is, how long did it take for you to become experienced enough to actually know exactly how your next line of code was going to look, before you even wrote it?

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  • Removing a view from it's superview causes memory error - why?

    - by mystify
    Xcode is throwing an error at me: malloc: * error for object 0x103f000: pointer being freed was not allocated * set a breakpoint in malloc_error_break to debug I tracked down the code until a line where I do this: - (void)inputValueCommitted:(NSString *)animationID finished:(BOOL)finished context:(void *)context { // retainCount of myView is 2! (one for the retain-property, one for beeing a subview) [self.myView removeFromSuperview]; // ERROR-LINE !! self.myView = nil; } When I remove that errorful line, the error is gone. So in conclusion: I can't get rid of my view! It's an UIImageView with nothing else inside, just showing an image. What I do is this: I create an UIView Animation Block, create that UIImageView, assign it to an retain-property with self.myView = ..., and after the animation is done, I just want to get rid of that view. So I remove it from it's superview and then set my property to nil, which lets it go away - in theory. Did anyone else encounter such issues? iPhone SDK 3.0.

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  • How to solve Memory leaks in Lib Xml Parser in objective-C where the list is returned?

    - by Madan Mohan
    Hi Guys, I got leaks in Lib Xml Parser while retrieving the data from the net, Here in the below code, I have allocated the list - (void)getCustomersList { // make an operation so we can push it into the queue SEL method = @selector(parseForData); NSInvocationOperation *op = [[NSInvocationOperation alloc] initWithTarget:self selector:method object:nil]; customersTempList = [[NSMutableArray alloc] initWithCapacity:20];// allocated list [self.retrieverQueue addOperation:op]; [op release]; } // return each recode // in parser .m class one of the condition in endElement where it shows a leak. else if(0 == strncmp((const char *)localname, kCustomerElement, kCustomerElementLength)) { [customersTempList addObject:customer]; printf("\n no of objects in temp list:%d", [customersTempList count]); if ([customersTempList count] == 20) { NSMutableArray* argsList = [customersTempList copy];//////////////////////here it is showing leak. printf("\n Calling reload data with %d new objects", [argsList count]); SEL selector = @selector(parser:addCustomerObject:); NSMethodSignature *sig = [(id)self.delegate methodSignatureForSelector:selector]; if(nil != sig && [self.delegate respondsToSelector:selector]) { NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:sig]; [invocation retainArguments]; [invocation setTarget:self.delegate]; [invocation setSelector:selector]; [invocation setArgument:&self atIndex:2]; [invocation setArgument:&argsList atIndex:3]; [invocation performSelectorOnMainThread:@selector(invoke) withObject:NULL waitUntilDone:NO]; } [customersTempList removeAllObjects]; } } // returned the list after all the records are stored in the list else if(0 == strncmp((const char *)localname, kCustomersElement, kCustomersElementLength)) { printf("\n Calling reload data with %d new objects", [customersTempList count]); NSMutableArray* argsList = [customersTempList copy]; printf("\n Calling reload data with %d new objects", [argsList count]); SEL selector = @selector(parser:addCustomerObject:); NSMethodSignature *sig = [(id)self.delegate methodSignatureForSelector:selector]; if(nil != sig && [self.delegate respondsToSelector:selector]) { NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:sig]; [invocation retainArguments]; [invocation setTarget:self.delegate]; [invocation setSelector:selector]; [invocation setArgument:&self atIndex:2]; [invocation setArgument:&argsList atIndex:3]; [invocation performSelectorOnMainThread:@selector(invoke) withObject:NULL waitUntilDone:NO]; } [customersTempList removeAllObjects]; } } please help me out of this, Thanks, Madan.

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  • Why can't I reclaim my dynamically allocated memory using the "delete" keyword?

    - by synaptik
    I have the following class: class Patient { public: Patient(int x); ~Patient(); private: int* RP; }; Patient::Patient(int x) { RP = new int [x]; } Patient::~Patient() { delete [] RP; } I create an instance of this class on the stack as follows: void f() { Patient p(10); } Now, when f() returns, I get a "double free or corruption" error, which signals to me that something is attempted to be deleted more than once. But I don't understand why that would be so. The space for the array is created on the heap, and just because the function from inside which the space was allocated returns, I wouldn't expect the space to be reclaimed. I thought that if I allocate space on the heap (using the new keyword), then the only way to reclaim that space is to use the delete keyword. Help! :)

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  • Huge Graph Structure

    - by Harph
    I'm developing an application in which I need a structure for represent a huge graph (between 1000000 and 6000000 nodes and 100 or 600 edges) in memory. The edges representation will contain some attribute of the relation. I have tried a memory map representation, arrays, dictionaries and string for represent that structure in memory, but this always crash because the memory limit. I would to get an advice of how can I represent this, or something similar. By the way, I'm using python.

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  • Concatenating a string and byte array in to unmanaged memory.

    - by Scott Chamberlain
    This is a followup to my last question. I now have a byte[] of values for my bitmap image. Eventually I will be passing a string to the print spooler of the format String.Format("GW{0},{1},{2},{3},", X, Y, stride, _Bitmap.Height) + my binary data; I am using the SendBytesToPrinter command from here. Here is my code so far to send it to the printer public static bool SendStringPlusByteBlockToPrinter(string szPrinterName, string szString, byte[] bytes) { IntPtr pBytes; Int32 dwCount; // How many characters are in the string? dwCount = szString.Length; // Assume that the printer is expecting ANSI text, and then convert // the string to ANSI text. pBytes = Marshal.StringToCoTaskMemAnsi(szString); pBytes = Marshal.ReAllocCoTaskMem(pBytes, szString.Length + bytes.Length); Marshal.Copy(bytes,0, SOMTHING GOES HERE,bytes.Length); // this is the problem line // Send the converted ANSI string + the concatenated bytes to the printer. SendBytesToPrinter(szPrinterName, pBytes, dwCount); Marshal.FreeCoTaskMem(pBytes); return true; } My issue is I do not know how to make my data appended on to the end of the string. Any help would be greatly appreciated, and if I am doing this totally wrong I am fine in going a entirely different way (for example somehow getting the binary data concatenated on to the string before the move to unmanaged space. P.S. As a second question, will ReAllocCoTaskMem move the data that is sitting in it before the call to the new location?

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  • Do the 'up to date' guarantees provided by final field in Java's memory model extend to indirect ref

    - by mattbh
    The Java language spec defines semantics of final fields in section 17.5: The usage model for final fields is a simple one. Set the final fields for an object in that object's constructor. Do not write a reference to the object being constructed in a place where another thread can see it before the object's constructor is finished. If this is followed, then when the object is seen by another thread, that thread will always see the correctly constructed version of that object's final fields. It will also see versions of any object or array referenced by those final fields that are at least as up-to-date as the final fields are. My question is - does the 'up-to-date' guarantee extend to the contents of nested arrays, and nested objects? An example scenario: Thread A constructs a HashMap of ArrayLists, then assigns the HashMap to final field 'myFinal' in an instance of class 'MyClass' Thread B sees a (non-synchronized) reference to the MyClass instance and reads 'myFinal', and accesses and reads the contents of one of the ArrayLists In this scenario, are the members of the ArrayList as seen by Thread B guaranteed to be at least as up to date as they were when MyClass's constructor completed?

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  • Running out of memory when getting a bitmap from a server?

    - by ikky
    Hi! I'm making an application which uses MANY images. The application gets the images from a server, and downloads them one at a time. After many images the creation of a bitmap returns an exception, but i don't know how to solve this. Here is my function for downloading the images: public static Bitmap getImageFromWholeURL(String sURL) { HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create(sURL); myRequest.Method = "GET"; // If it does not exist anything on the url, then return null try { HttpWebResponse myResponse = (HttpWebResponse)myRequest.GetResponse(); System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(myResponse.GetResponseStream()); myResponse.Close(); return bmp; } catch (Exception e) { return null; } } Can anyone help me out here? Thanks in advance!

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  • pointer to preallocated memory as an input parameter and have the function fill it

    - by djones2010
    test code: void modify_it(char * mystuff) { char test[7] = "123456"; //last element is null i presume for c style strings here. //static char test[] = "123123"; //when i do this i thought i should be able to gain access to this bit of memory when the function is destroyed but that does not seem to be the case. //char * test = new char[7]; //this is also creating memory on stack and not the heap i reckon and gets destroyed once the function is done with. strcpy_s(mystuff,7,test); //this does the job as long as memory for mystuff has been allocated outside the function. mystuff = test; //this does not work. I know with c style strings you can't just do string assignments they have to be actually copied. in this case I was using this in conjunction with static char test thinking by having it as static the memory would not get destroyed and i can then simply point mystuff to test and be done with it. i would later have address the memory cleanup in the main function. but anyway this never worked. } int main(void) { char * mystuff = new char [7]; //allocate memory on heap where the pointer will point cool(mystuff); std::string test_case(mystuff); std::cout<<test_case.c_str(); //this is the only way i know how to use cout by making it into a string c++ string. delete [] mystuff; return 0; } in the case, of a static array in the function why would it not work. in the case, when i allocated memory using new in the function does it get created on the stack or heap? in the case, i have string which needs to be copied into a char * form. everything i see usually requires const char* instead of just char*. I know i could use reference to take care of this easy. Or char ** to send in the pointer and do it that way. But i just wanted to know if I could do it with just char *. Anyway your thoughts and comments plus any examples would be very helpful.

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  • What's in-memory database technology that do realtime materialized view?

    - by KA100
    What I'm looking for is something like materialized views in front-end that shows my data in diffident ways without full recalculation. let's say I have stock watcher with many front-end views and dashborads some based on aggregation, order by or just filter with different criteria defined realtime by user. Now, I receive online record updates from some webservice and it's not like "data warehouse" every single record can be updated any time and it actually happens every second. Is there any technology can help me in such I create something like materialized view and it's update it without doing full recalculation every time data changed. Thank you.

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  • Iterating over a large data set in long running Python process - memory issues?

    - by user1094786
    I am working on a long running Python program (a part of it is a Flask API, and the other realtime data fetcher). Both my long running processes iterate, quite often (the API one might even do so hundreds of times a second) over large data sets (second by second observations of certain economic series, for example 1-5MB worth of data or even more). They also interpolate, compare and do calculations between series etc. What techniques, for the sake of keeping my processes alive, can I practice when iterating / passing as parameters / processing these large data sets? For instance, should I use the gc module and collect manually? Any advice would be appreciated. Thanks!

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  • Developing online invoicing and inventory application.

    - by Rohit
    My clients are using a desktop version of my inventory solution that I developed using .NET. I want to make an online version so that data is available centrally and clients can work from any location. I searched using Google to find similar tools and found few. I want to know what type of security considerations to take while designing such an application? Some clients can't afford dedicated server cost. What if I use shared hosting only? What are the risks of shared hosting?

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  • Developing online invoicing and inventory application.

    - by Rohit
    My clients are using a desktop version of my inventory solution that I developed using .NET. I want to make an online version so that data is available centrally and clients can work from any location. I searched using Google to find similar tools and found few. I want to know what type of security considerations to take while designing such an application? Some clients can't afford dedicated server cost. What if I use shared hosting only? What are the risks of shared hosting?

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  • IIS7 web farm - local or shared content?

    - by rbeier
    We're setting up an IIS7 web farm with two servers. Should each server have its own local copy of the content, or should they pull content directly from a UNC share? What are the pros and cons of each approach? We currently have a single live server WEB1, with content stored locally on a separate partition. A job periodically syncs WEB1 to a standby server WEB2, using robocopy for content and msdeploy for config. If WEB1 goes down, Nagios notifies us, and we manually run a script to move the IP addresses to WEB2's network interface. Both servers are actually VMs running on separate VMWare ESX 4 hosts. The servers are domain-joined. We have around 50-60 live sites on WEB1 - mostly ASP.NET, with a few that are just static HTML. Most are low-traffic "microsites". A few have moderate traffic, but none are massive. We'd like to change this so both WEB1 and WEB2 are actively serving content. This is mainly for reliability - if WEB1 goes down, we don't want to have to manually intervene to fail things over. Spreading the load is also nice, but the load is not high enough right now for us to need this. We're planning to configure our firewall to balance traffic across the two servers. It will detect when a server goes down and will send all the traffic to the remaining live server. We're planning to use sticky sessions for now... eventually we may move to SQL Server session state and stateless load balancing. But we need a way for the servers to share content. We were originally planning to move all the content to a UNC share. Our storage provider says they can set up a highly available SMB share for us. So if we go the UNC route, the storage shouldn't be a single point of failure. But we're wondering about the downsides to this approach: We'll need to change the physical paths for each site and virtual directory. There are also some projects that have absolute paths in their web.config files - we'll have to update those as well. We'll need to create a domain user for the web servers to access the share, and grant that user appropriate permissions. I haven't looked into this yet - I'm not sure if the application pool identity needs to be changed to this user, or if there's another way to tell IIS to use this account when connecting to the share. Sites will no longer be able to access their content if there's ever an Active Directory problem. In general, it just seems a lot more complicated, with more moving parts that could break. Our storage provider would create a volume for us on their redundant SAN. If I understand correctly, this SAN volume would be mounted on a VM running in their redundant VMWare environment; this VM would then expose the SMB share to our web servers. On the other hand, a benefit of the shared content approach is that we'd only need to deploy code to one place, and there would never be a temporary inconsistency between multiple copies of the content. This thread is pretty interesting, though some of these people are working at a much larger scale. I've just been discussing content so far, but we also need to think about configuration. I don't know if we can just use DFS replication for the applicationHost.config and other files, or if it's best to use the shared configuration feature with the config on a UNC share. What do you think? Thanks for your help, Richard

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  • Website Content via remote mysql or API for clients

    - by Kannan
    I would like to know whether there will be problem for shared hosting/vps/dedicated users if they request content via remote mysql or via http API. ? What will be issues if they make every request to production server for delivery of the website articles along with image urls etc. Will it cause disk wait on shared/vps/dedicated hosting users ? Will both remotemysql or http api or curl cause high CPU usage, I/O wait or Memory usage ? What should be best for speed remote mysql or http web api ? or any alternatives ? Thanku Kannan

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  • Oracle Database In-Memory Launch Featuring Larry Ellison – June 10

    - by Roxana Babiciu
    For more than three-and-a-half decades, Oracle has defined database innovation. With our market-leading technologies, customers have been able to out-think and out-perform their competition. Soon they will be able to do that even faster. At a live launch event and simultaneous webcast, Larry Ellison will reveal the future of the database. Promote this strategic event to customers. Registration for the live event begins at 9am PT.

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  • Oracle Database In-Memory Launch Featuring Larry Ellison – June 10

    - by Cinzia Mascanzoni
    For more than three-and-a-half decades, Oracle has defined database innovation. With our market-leading technologies, customers have been able to out-think and out-perform their competition. Soon they will be able to do that even faster. At a live launch event and simultaneous webcast, Larry Ellison will reveal the future of the database. Promote this strategic event to partners and customers. Registration for the live event begins at 5pm GMT, 6pm CET.

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