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  • Fastest file reading in C.

    - by Jay
    Right now I am using fread() to read a file, but in other language fread() is inefficient i'v been told. Is this the same in C? If so, how would faster file reading be done?

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  • Show a Copying-files dialog/form while manually copying files in C#?

    - by Dinoo
    I am manually copying some folders and files through C#, and I want to show the user that something is actually going on. Currently, the program looks as if its frozen, but it is actually copying files. I would think there is already a built-in dialog or form that shows the process, similar to copying/moving files in windows explorer. Is there anything like that available, or will I have to create everything from scratch? Also, would this be the best method to show the user that something is actively going on? Thanks for the help!

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  • Should repeated use of the camera crash an app?

    - by Sam
    I have an app that builds a slideshow from user images. They can grab from their library or take a picture. I have found that repeated use of grabbing an image from the library is fine. But repeated use of taking a picture causes erratic behavior. I have been getting crashes but mostly what happens seems to be a reloading of the view after "didFinishPickingMediaWithInfo", which messes things up. I have no leaks and it seems to be releasing properly after each picture is taken. I am resizing the image and saving it in a data base. Is anyone else running into this situation? Was the camera not designed to be called this often?

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  • How costly performance-wise are these actions in iPhone objective-C?

    - by Alex Gosselin
    This is really a few questions in one, I'm wondering what the performance cost is for these things, as I haven't really been following a best practice of any sort for these. The answers may also be useful to other readers, if somebody knows these. (1) If I need the core data managed object context, is it bad to use #import "myAppDelegate.h" //farther down in the code: NSManagedObjectContext *context = [(myAppDelegate.h*)[[UIApplication sharedApplication] delegate] managedObjectContext]; as opposed to leaving the warning you get if you don't cast the delegate? (2) What is the cheapest way to hard-code a string? I have been using return @"myString"; on occasion in some functions where I need to pass it to a variety of places, is it better to do it this way: static NSString *str = @"myString"; return str; (3) How costly is it to subclass an object i wrote vs. making a new one, in general? (4) When I am using core data and navigating through a hierarchy of some sort, is it necessary to turn things back into faults somehow after I read some info from them? or is this done automatically? Thanks for any help.

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  • Using std::bad_alloc for C pointers

    - by otibom
    I'm using a library written in C in a C++ project. I'd like to use C++ exceptions to handle C errors. In particular, it would be nice to have an exception thrown if an allocation fails. I can do this in constructors of classes which hold C-style pointers to C structs : if (c_object == NULL) throw std::bad_alloc(); But if the class is responsible for several C objects they are no ways of free-ing all already allocated pointers since the destructor isn't called. I have a feeling I could use smart-pointers, but I don't have much experience with them. What's more, I have to have access to the original C pointers to use the C api properly. Is there an elegant solution to this ?

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  • Linking to a Large address aware DLL.

    - by Canopus
    Suppose I have a DLL which is built with LARGEADDRESSAWARE linker flag set. Now I have an application dynamically linking to this DLL. Does this make my application LARGEADDRESSAWARE? If not then, does it make sense to have this flag set for any DLL?

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  • Static variables within functions in C++ - allocated even if function doesn't run?

    - by John C
    I've been reading up on C++ on the Internet, and here's one thing that I haven't been quite able to find an answer to. I know that static variables used within functions are akin to globals, and that subsequent invocations of that function will have the static variable retain its value between calls. However, if the function is never claled, does the static variable get allocated? Thanks

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  • How much RAM used by Python dict or list?

    - by Who8MyLunch
    My problem: I am writing a simple Python tool to help me visualize my data as a function of many parameters. Each change in parameters involves a non-trivial amount of time, so I would like to cache each step's resulting imagery and supporting data in a dictionary. But then I worry that this dictionary could grow too large over time. Most of my data is in the form of Numpy arrays. My question: How would one go about computing the total number of bytes used by a Python dictionary. The dictionary itself may contain lists and other dictionaries, each of which contain data stored in Numpy arrays. Ideas?

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  • C#: How to implement a smart cache

    - by Svish
    I have some places where implementing some sort of cache might be useful. For example in cases of doing resource lookups based on custom strings, finding names of properties using reflection, or to have only one PropertyChangedEventArgs per property name. A simple example of the last one: public static class Cache { private static Dictionary<string, PropertyChangedEventArgs> cache; static Cache() { cache = new Dictionary<string, PropertyChangedEventArgs>(); } public static PropertyChangedEventArgs GetPropertyChangedEventArgsa(string propertyName) { if (cache.ContainsKey(propertyName)) return cache[propertyName]; return cache[propertyName] = new PropertyChangedEventArgs(propertyName); } } But, will this work well? For example if we had a whole load of different propertyNames, that would mean we would end up with a huge cache sitting there never being garbage collected or anything. I'm imagining if what is cached are larger values and if the application is a long-running one, this might end up as kind of a problem... or what do you think? How should a good cache be implemented? Is this one good enough for most purposes? Any examples of some nice cache implementations that are not too hard to understand or way too complex to implement?

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  • PHP Zip Archive sporadically creating multiple files

    - by user516558
    I have a PHP script (running PHP 5.2 on Apache 2.2) that creates a zip archive of files for a user to download. Everything seems to work just fine; the only issue I have is that periodically multiple files will be created before the ZIP archive is successfully finished. Example: archive-name.zip archive-name.zip.a09600 archive-name.zip.b09600 archive-name.zip.c09600 This does not happen every single time; only periodically - the file is still created but sometimes these extra 'files' are left on the server after it finishes. The code that creates the ZIP archive is as follows: $zip_archive = new ZipArchive(); $zip_archive->open($archiveFullName,ZIPARCHIVE::CREATE); if(!file_exists($archiveFullName)) { foreach ($completed_file_arr as $zip_file) { $isFiller = substr($zip_file,-8) == "_err.txt"; if(!$isFiller) { $zip_archive->addFile($zip_file,$localname); } else $zip_archive->addFromString ($zip_file, "The requested source file could not be found."); } } while(!$zip_archive->close()) sleep(1); //ensure that the ZIP file finishes closing

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  • Control the MultipleOutputFormat files sub-path

    - by iCode
    I need to control the sub-path of the different different files being managed by MultipleOutputFormat based on the reducer key. I basically want to set the sub path of the file based on the key given to the reducer. I can changed the file name by overwrting the generateFileNameForKeyValue method of MultipleOutputFormatbut how can I also change the sub-path of these files? I mean with just overriding the generateFileNameForKeyValue, I get mySetJobConfigOutputPath/fileNameBasedKey1.dat /fileNameBasedKey2.dat /fileNameBasedKey3.dat ... but I want to make it to be organize files like below mySetJobConfigOutputPath/path0ConfiguredInsideReducerBasedOnKey/fileNameBasedKey1.dat /path1ConfiguredInsideReducerBasedOnKey/fileNameBasedKey2.dat /fileNameBasedKey3.dat /path2ConfiguredInsideReducerBasedOnKey/fileNameBasedKey8.dat as seen, the sub-path and the file name are both figured out by the key inside the reducer. I know how to configure the file name but was wondering if I can configure the sub-path of the each file under the mySetJobConfigOutputPath folder?

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  • How does the CLR (.NET) internally allocate and pass around custom value types (structs)?

    - by stakx
    Question: Do all CLR value types, including user-defined structs, live on the evaluation stack exclusively, meaning that they will never need to be reclaimed by the garbage-collector, or are there cases where they are garbage-collected? Background: I have previously asked a question on SO about the impact that a fluent interface has on the runtime performance of a .NET application. I was particuarly worried that creating a large number of very short-lived temporary objects would negatively affect runtime performance through more frequent garbage-collection. Now it has occured to me that if I declared those temporary objects' types as struct (ie. as user-defined value types) instead of class, the garbage collector might not be involved at all if it turns out that all value types live exclusively on the evaluation stack. What I've found out so far: I did a brief experiment to see what the differences are in the CIL generated for user-defined value types and reference types. This is my C# code: struct SomeValueType { public int X; } class SomeReferenceType { public int X; } . . static void TryValueType(SomeValueType vt) { ... } static void TryReferenceType(SomeReferenceType rt) { ... } . . var vt = new SomeValueType { X = 1 }; var rt = new SomeReferenceType { X = 2 }; TryValueType(vt); TryReferenceType(rt); And this is the CIL generated for the last four lines of code: .locals init ( [0] valuetype SomeValueType vt, [1] class SomeReferenceType rt, [2] valuetype SomeValueType <>g__initLocal0, // [3] class SomeReferenceType <>g__initLocal1, // why are these generated? [4] valuetype SomeValueType CS$0$0000 // ) L_0000: ldloca.s CS$0$0000 L_0002: initobj SomeValueType // no newobj required, instance already allocated L_0008: ldloc.s CS$0$0000 L_000a: stloc.2 L_000b: ldloca.s <>g__initLocal0 L_000d: ldc.i4.1 L_000e: stfld int32 SomeValueType::X L_0013: ldloc.2 L_0014: stloc.0 L_0015: newobj instance void SomeReferenceType::.ctor() L_001a: stloc.3 L_001b: ldloc.3 L_001c: ldc.i4.2 L_001d: stfld int32 SomeReferenceType::X L_0022: ldloc.3 L_0023: stloc.1 L_0024: ldloc.0 L_0025: call void Program::TryValueType(valuetype SomeValueType) L_002a: ldloc.1 L_002b: call void Program::TryReferenceType(class SomeReferenceType) What I cannot figure out from this code is this: Where are all those local variables mentioned in the .locals block allocated? How are they allocated? How are they freed? Why are so many anonymous local variables needed and copied to-and-fro only to initialize my two local variables rt and vt?

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  • deleting unaccessed files using python

    - by damon
    My django app parses some files uploaded by the user.It is possible that the file uploaded by the user may remain in the server for a long time ,without it being parsed by the app.This can increase in size if a lot of users upload a lot of files. I need to delete those files not recently parsed by the app -say not accessed for last 24 hours.I tried like this import os import time dirname = MEDIA_ROOT+my_folder filenames = os.listdir(dirname) filenames = [os.path.join(dirname,filename) for filename in filenames] for filename in filenames: last_access = os.stat(filename).st_atime #secs since epoch rtime = time.asctime(time.localtime(last_access)) print filename+'----'+rtime This shows the last accessed times for each file..But I am not sure how I can test if the file access time was within the last 24 hours..Can somebody help me out?

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  • reading a file word by word

    - by nalbina
    I can read from a file 1 character at a time, but how do i make it go just one word at a time? So, read until there is a space and take that as a string. This gets me the characters: while (!fin.eof()){ while (fin f ){ F.push_back ( f ); }

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  • Enter custom file name to be read ?

    - by ZaZu
    Hello, I want to allow users to type the name of any .txt file to be read/written. This is my code : printf("Enter .txt file name\n"); scanf("%s",&fname); FILE *inputf; inputf=fopen(&fname,"w"); Problem is this method does not work (having &fname) as a parameter. I can imagine its because C needs "filename.txt" for it work ... even if I enter for example : "custom.txt", the program returns an error of "Storage block not big enough for this operation" What is the correct method to accomplish this ? Im using C and im pretty much using basic commands .. (not too advanced) Thanks alot !!!

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  • How to replace same text in a text file

    - by user1688220
    i created a c# windows login form and i am saving username or password to a text file but every time i use same username or password that i have saved before it takes new place in that text file. But What i want is to replace the same username or password that is already saved in that text file. this is my code: private void button1_Click(object sender, EventArgs e) { try { FileStream fs = new FileStream("data.txt", FileMode.Append, FileAccess.Write); StreamWriter sw = new StreamWriter(fs); sw.Write("Email ID: "); sw.WriteLine(textBox1.Text); sw.Write("Password: "); sw.Write(textBox2.Text); sw.WriteLine(); sw.WriteLine(); sw.Flush(); sw.Close(); fs.Close(); } catch (Exception) { MessageBox.Show("Error", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); this.Close(); } MessageBox.Show("DONE", "Done", MessageBoxButtons.OK, MessageBoxIcon.Information); textBox1.Clear(); textBox2.Clear(); }

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  • C: theory on how to extract files from an archived file

    - by donok
    In C I have created a program which can archive multiple files into an archive file via the command line. e.g. $echo 'file1/2' > file1/2.txt $./archive file1.txt file2.txt arhivedfile $cat archivedfile file1 file2 How do I create a process so that in my archivedfile I have: header file1 end header file2 end They are all stored in the archive file one after another after another. I know that perhaps a header file is needed(containing filename, size of filename, start and end of file) for extracting these files back out into their original form, but how would I go about doing this. I am stuck on where and how to start. Please could someone help me on some logic as to how to approach extracting files back out of an archived file.

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  • Android Static Variable Scope and Lifetime

    - by Edison
    I have an application that has a Service uses a ArrayList to store in the background for a very long time, the variable is initialized when the service started. The service is in the background and there will be frequent access to the variable (that's why i don't want to use file management or settings since it will be very expensive for a file I/O for the sake of battery life). The variable will likely to be ~1MB-2MB over its life tie. Is it safe to say that it will never be nulled by GC or the system or is there any way to prevent it? Thanks.

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  • open program once with multiple files as arguments from explorer

    - by Jonathan
    I have a program that works when, a file is opened with it using the right click menu in explorer. But if I select multiple files and then right click and open with my program then it opens multiple instances of my program, instead of just passing the multiple files as arguments to a single instance. The program is written in vb.net but is not a windows form, it is just a module, so I can to tick the Single instance option in the properties in Visual Studio. So how do I open multiple files from explorer context menu in a single instance.

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  • Programmatically find maximum static array size in C++

    - by GuyGreer
    I am curious whether it is possible to determine the maximum size that an array can have in C++. #include <iostream> using namespace std; #define MAX 2000000 int main() { long array[MAX]; cout << "Message" << endl; return 0; } This compiles just fine, but then segfaults as soon as I run it (even though array isn't actually referenced). I know it's the array size too because if I change it to 1000000 it runs just fine. So, is there some define somewhere or some way of having #define MAX MAX_ALLOWED_ARRAY_SIZE_FOR_MY_MACHINE_DEFINED_SOMEWHERE_FOR_ME? I don't actually need this for anything, this question is for curiosity's sake.

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  • Windows XP batch file concat

    - by dls
    I'm trying to accomplish the following ridiculous task: I have a text file containing a set of fully qualified filesnames. I want to iterate through the file and append each line to a common variable, that can be passed to a command line tool. For example, the file might be: C:\dir\test.txt C:\WINDOWS\test2.txt C:\text3.txt and I'd like to assign them to some variable 'a' such that: a = "C:\dir\test.txt C:\WINDOWS\test2.txt C:\text2.txt" A secondary question is - what is a good batch file reference? I'm finding some stuff in the Windows material, and a lot of home-grown websites, but nothing particularly complete. Thanks!

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  • How to move many files in multiple different directories (on Linux)

    - by user1335982
    My problem is that I have too many files in single directory. I cannot "ls" the directory, cos is too large. I need to move all files in better directory structure. I'm using the last 3 digits from ID as folders in reverse way. For example ID 2018972 will gotta go in /2/7/9/img_2018972.jpg. I've created the directories, but now I need help with bash script. I know the IDs, there are in range 1,300,000 - 2,000,000. But I can't handle regular expressions. I wan't to move all files like this: /images/folder/img_2018972.jpg -> /images/2/7/9/img_2018972.jpg I will appreciate any help on this subject. Thanks!

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