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• Comparing large strings in JavaScript with a hash

  - by user4815162342

  I have a form with a textarea that can contain large amounts of content (say, articles for a blog) edited using one of a number of third party rich text editors. I'm trying to implement something like an autosave feature, which should submit the content through ajax if it's changed. However, I have to work around the fact that some of the editors I have as options don't support an "isdirty" flag, or an "onchange" event which I can use to see if the content has changed since the last save. So, as a workaround, what I'd like to do is keep a copy of the content in a variable (let's call it lastSaveContent), as of the last save, and compare it with the current text when the "autosave" function fires (on a timer) to see if it's different. However, I'm worried about how much memory that could take up with very large documents. Would it be more efficient to store some sort of hash in the lastSaveContent variable, instead of the entire string, and then compare the hash values? If so, can you recommend a good javascript library/jquery plugin that implements an appropriate hash for this requirement?

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• GCC compiler -- bug or unspecified behavior?

  - by Jared P

  When I have conflicting definitions of the ivars of a class in objective-c (not redeclaring the class in the same file, but rather naming the same class with diff ivars, no warnings or better yet errors are issued by the compiler. However, both sets of ivars are useable by the appropriate methods in the respective files. For instance Foo.m: @interface foo { int a; } - (int)method; @end @implementation foo - (int)method { return a; } @end Bar.m: @interface foo { float baz; } @end @implementation foo (category) - (float)blah { return baz; } @end compiles without warnings or errors. Is this intentional? Is this an unchecked error? (for the record, a and baz are actually the same memory location.)

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• C++ MFC how to compare LPCTSTR in a if statement?

  - by user1078510

  I have the following code: LPCTSTR strPermission = Method(); if (strPermission == L"0") { return true; } else { return false; } While debugging I can see that strPermission does equal "0", yet when I compare it like in the if statement it always returns false. The only thing I can think of is that it is comparing the memory address of the variable rather than the variable value. How do I compare strPermission to L"0" so that it would return true if strPermission equals "0". Thank you!

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• Zend_Soap with attachments (server)

  - by Tom

  i'm trying to build a SOAP service with Zend_Soap. Everything is working great but the client needs the ability to send attachments to the service (not base64 encoded strings, as this service will be called multiple times a day with various file sizes so processing all that in memory is not possible. So I'd like to handle a normal SOAP attachment (DIME/MIME) with the SOAP server in Zend Framework however I'm unable to find documentation about it. Can I access it with $_FILES[] or any other way? Is it even possible in Zend_Soap (as there's not that much info available). SOAP is a must - so thanks for the advice but it has to be SOAP, not REST.

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• Should I put a try-finally block after every Object.Create?

  - by max

  I have a general question about best practice in OO Delphi. Currently, I put try-finally blocks anywhere I create an object to free that object after usage (to avoid memory leaks). E.g.: aObject := TObject.Create; try aOBject.AProcedure(); ... finally aObject.Free; end; instead of: aObject := TObject.Create; aObject.AProcedure(); .. aObject.Free; Do you think it is good practice, or too much overhead? And what about the performance?

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• Flipping an image using a one dimensional array of characters.

  - by Jeff

  I have the data of an image loaded into memory as a one dimensional array. Since I'm trying to use OpenGL to draw it, and since it reads from the bottom up, I want to try and flip the elements of the array before they're sent to OpenGL. Maybe there's a way to tell OpenGL to read from the top to the bottom? Anyways, I tried using a few methods of sorting arrays and they also flip the image horizontally, which is very much like the original problem. So can I flip the data only one way?

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• Mootools event leak

  - by user572263

  The example to demonstrate the issue can be found here: link text The test shows a basic Mootools class that contains an element variable with a click event attached. There’s also a “cleanup” function to remove the event and nullify the element variable. My problem is that when I loop a thousand times to create the “LeakClass” instance and clean it up, it causes a major memory leak like there’s no tomorrow. I tested this on IE8 and Chrome. On the other hand what I’ve noticed is that if I comment out the line that adds the “click” event, the code doesn’t leak. Can somebody please help me structure the class/event in a manner that it doesn’t leak. Thanks in advance.

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• C# thread safety for class instances

  - by Steveng

  I am learning C# and I am confused with the thread safety of the copies of the class instances as below: eg: classA objA; classA objB = objA; objA.field1 = value2; //do I need lock around modification of field1? //let say we pass the objB to another thread objB.field1 = value1 //do I need a lock for objB because of the modification of field1? I am confused because coming from the background of C++, the class in C# is the reference type. If both objA and objB refer to the same memory underlying, then I would need a lock to protect the simultaneous writing to the field1. Could someone confirm with this or am I missing something? Thanks.

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• Load big XML files to mySQL database (PHP)

  - by Kees

  Hello There, For a new project I need to load big XML files (200MB+) to a mySQL database. There are +- 20 feeds i need to match with that (not all fields are the same). Now when i want to catch the XML I get this error: Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 171296569 bytes) in E:\UsbWebserver\Root\****\application\libraries\MY_xml.php on line 21 Is there an easy solution for this? It's not possible to get te feed in parts of a few MB's each. Thank you very much! P.s. has somebody an idea to match xml-feeds easy?

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• pointers for getting elements of an array in C

  - by Manolo

  I am a newbie in C and I would like to get the elements of an array with a function, I have tried different options, but I still do not get the elements. My function is: void getelements(int *a, int cl) { int *p; for (p=&a[0];p<&a[cl];p++) { printf("%d\n",*p); } } I know that the solution should work like that, but it only prints the first element and then memory positions. I am calling my function with: int v={10,12,20,34,45}; getelements(&v,5); Any help? I need to use arithmetic of pointers. Thanks

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• How should I store this information?

  - by 5YrsLaterDBA

  I have a PrivilegeGroup table, a Privileges table and a link table because the PrivilegeGroup table and the Privileges table is a many to many relationship. I am thinking about load all contents of PrivilegeGroup table and Privilege table into memory from database at beginning when application started. I want to save them in a form easily to look up. Usually we will look up the PrivilegeCode via GroupId. Which structure is good for this purpose? array of list? dictionary?

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• a macro question for c language (#define)

  - by Daniel

  I am reading source code of hoard memory allocator, and in the file of gnuwrapper.cpp, there are the following code #define CUSTOM_MALLOC(x) CUSTOM_PREFIX(malloc)(x) What's the meaning of CUSTOM_PREFIX(malloc)(x)? is CUSTOM_PREFIX a function? But as a function it didn't defined anywhere. If it's variable, then how can we use variable like var(malloc)(x)? more code: #ifndef __GNUC__ #error "This file requires the GNU compiler." #endif #include <string.h> #include <stdlib.h> #include <stdio.h> #include <malloc.h> #ifndef CUSTOM_PREFIX ==> here looks like it's a variable, so if it doesn't define, then define here. #define CUSTOM_PREFIX #endif #define CUSTOM_MALLOC(x) CUSTOM_PREFIX(malloc)(x) ===> what's the meaning of this? #define CUSTOM_FREE(x) CUSTOM_PREFIX(free)(x) #define CUSTOM_REALLOC(x,y) CUSTOM_PREFIX(realloc)(x,y) #define CUSTOM_MEMALIGN(x,y) CUSTOM_PREFIX(memalign)(x,y)

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• Deleting a element from a vector of pointers in C++.

  - by Kranar

  I remember hearing that the following code is not C++ compliant and was hoping someone with much more C++ legalese than me would be able to confirm or deny it. std::vector<int*> intList; intList.push_back(new int(2)); intList.push_back(new int(10)); intList.push_back(new int(17)); for(std::vector<int*>::iterator i = intList.begin(); i != intList.end(); ++i) { delete *i; } intList.clear() The rationale was that it is illegal for a vector to contain pointers to invalid memory. Now obviously my example will compile and it will even work on all compilers I know of, but is it standard compliant C++ or am I supposed to do the following, which I was told is in fact the standard compliant approach: while(!intList.empty()) { int* element = intList.back(); intList.pop_back(); delete element; }

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• Reading a bmp file and inverting it in C

  - by user1763396

  I have an assignment that deals with reading a bmp file into memory, inverts the pixels, and then saves the inverted image to a new file. From this description it seems fairly easy, however I don't think my professor did a great job in explaining the necessary steps to go about doing so. He taught us about fread and fwrite but there is so much more. Can anyone explain the process in going about this problem (I'm no looking for a direct answer just an explanation). Here is the link to the problem's description: https://engineering.purdue.edu/OOSD/F2012/Exercises/ex5.html Thanks in advance for any sort of help. NOTE: I actually have looked into this problem but since I don't have a good standing on this info it's not quite "clicking".

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• ordering a collection by an association's property

  - by neiled

  class Person belongs_to :team class Status #has last_updated property class Team has_many :members, :class => "Person" Ok, so I have a Team class which has many People in it and each of those people has a status and each status has a last_updated property. I'm currently rendering a partial with a collection similar to: =render :partial => "user", :collection => current_user.team.members Now how do I go about sorting the collection by the last_updated property of the Status class? Thanks in advance! p.s. I've just written the ruby code from memory, it's just an example, it's not meant to compile but I hope you get the idea!

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• Can JQuery/JavaScript be used to write a substantial client side application?

  - by Ian

  I have an unusual situation - I have an embedded video streaming device with a complicated UI, and I need to use an embedded web server to reproduce that UI through a web browser. I'm thinking of using JavaScript/JQuery on a C++ backend (I am NOT coding all this myself, I need to hire people for the grunt work). The embedded web server is much less powerful than a PC, so I want to write an application that runs the entire UI in the browser, and only communicates with the server to pass new program settings back and forth, get status updates from the device, and control video playback. In other words, the client gets one big page or a small number of big pages (effectively downloading the application), the application maintains significant local memory storage, and once the pages are first loaded the server never sends anything layout-related. The application has two rows of tabs to navigate ~40 menu pages, drag-and-select controls to pick cells in a grid, sorted lists, lots of standard data entry options, and it should be able to control up to 16 embedded video players at once (preferably VLC). Is this possible in JavaScript/JQuery with a C++ backend?

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• Java SWT - dissolve (fade) from one image to the next.

  - by carillonator

  I'm pretty new to Java and SWT, hoping to have one image dissolve into the next. I have one image now in a Label (relevant code): Device dev = shell.getDisplay(); try { Image photo = new Image(dev, "photo.jpg"); } catch(Exception e) { } Label label = new Label(shell, SWT.IMAGE_JPEG); label.setImage(photo); Now I'd like photo to fade into a different image at a speed that I specify. Is this possible as set up here, or do I need to delve more into the org.eclipse.swt.graphics api? Also, this will be a slide show that may contain hundreds of photos, only ever moving forward (never back to a previous image)---considering this, is there something I explicitly need to do in order to remove the old images from memory? Thanks!!

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• Difficulty understanding behavior of free()

  - by Rasmi Ranjan Nayak

  int main() { int *ptr, **ptr1; ptr = (int*)malloc(sizeof(int)); ptr1 = (int**)malloc(sizeof(int)); free(ptr); *ptr = 12345; ptr1 = &ptr; //free(ptr); //**ptr1 = 23456; printf("%d \n", **ptr1); system("pause"); return 0; } How does *ptr store the value 12345, when the memory has already been freed? So, now ptr should be pointing to garbage. Why is this happening?

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• used structdelete and now Elementemployee.id is undefined in SESSION.

  - by Robert

  using coldfuion 9 I used structdelete(session,"Elementemployee.id") in one of my .cfm display files.Also in my application.cfc it defined as is <cfset tArray[1][2] = "#session.employee_id#"> and the error is `Elementemployee.id is undefined in SESSION.` Is there a way that i can reset it without following the method shown below Navigate to the page Server Settings => Memory Variablesin the Coldfusion Administrator. Uncheck the option Use J2EE session variables and check the options Enable Application Variables and Enable Session Variables. Click the button to submit the changes.

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• java virtual machine - how does it allocate resources?

  - by Will

  I am testing the performance of a data streaming system that supports continuous queries. This is how it works: - There is a polling service which sends data to my system. - As data passes into the system, each query evaluates based on a window of the stream at the current time. - The window slides as data passes in. My problem is this, when I add more queries to the system, I should expect the throughput to decrease because it can't cope the data rate. However, I actually observe an increase in throughput. I can't understand why this is the case and I am guessing that it's something to do with the way the JVM allocates CPU, memory etc. Can anyone shed any light to my problem?

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• I want to crop an image, draw a smaller size image without caching the images.... What is the best w

  - by rkbang

  Hello all, I am storing the images in database. I get the NSData and create an image from it. Now I want to crop or draw a smaller image of the existing image in database which I am getting from the querry. I dont want to cache the images since I am using them in bulk and want to release them as soon as the view being displayed where the images are used is popped up. Is there any efficient solution to make sure that images dont consume memory at the background once their use is over... I will appreciate the lines of code for this. Tnx in advance.

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• Using temporary arrays to cut down on code - inefficient?

  - by tommaisey

  I'm new to c++ (and SO) so sorry if this is obvious. I've started using temporary arrays in my code to cut down on repetition and to make it easier to do the same thing to multiple objects. So instead of: MyObject obj1, obj2, obj3, obj4; obj1.doSomming(arg); obj2.doSomming(arg); obj3.doSomming(arg); obj4.doSomming(arg); I'm doing: MyObject obj1, obj2, obj3, obj4; MyObject* objs[] = {&obj1, &obj2, &obj3, &obj4}; for (int i = 0; i !=4; ++i) objs[i]->doSomming(arg); Is this detrimental to performance? Like, does it cause unnecessary memory allocation? Is it good practice? Thanks.

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• Why don't hardware failures show up at the programming language level?

  - by Julian Cienfuegos

  I am wondering if anyone can give my a good answer, or at least point me in the direction of a good reference to the following question: How come I have never heard of a computer breaking in a very fundamental way? How come when I declare x to be a double it stays as a double? How come there is never a short circuit that robs it of some bytes and makes it an integer? Why do we have faith that when we initialize x to 10, there will never be a power surge that will cause it to become 11, or something similar? I think I need a better understanding of memory. Thanks, and please don't bash me over the head for such a simple/abstract question.

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• construct a unique number for a string in java

  - by praveen

  We have a requirement of reading/writing more than 10 million strings into a file. Also we do not want duplicates in the file. Since the strings would be flushed to a file as soon as they are read we are not maintaining it in memory. We cannot use hashcode because of collisions in the hash code due to which we might miss a string as duplicate. Two other approaches i found in my googling: 1.Use a message digest algorithm like MD5 - but it might be too costly to calculate and store. 2.Use a checksum algorithm. [i am not sure if this produces a unique key for a string- can someone please confirm] Is there any other approach avaiable. Thanks.

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• Annotation retention policy: what real benefit is there in declaring `SOURCE` or `CLASS`?

  - by watery

  I know there are three retention policies for Java annotations: CLASS: Annotations are to be recorded in the class file by the compiler but need not be retained by the VM at run time. RUNTIME: Annotations are to be recorded in the class file by the compiler and retained by the VM at run time, so they may be read reflectively. SOURCE: Annotations are to be discarded by the compiler. And although I understand their usage scenarios, I don't get why it is such an important thing to specify the retention policy that retention policies exist at all. I mean, why aren't all the annotations just kept at runtime? Do they generate so much bytecode / occupy so much memory that stripping those undeclared as RUNTIME does make that much difference?

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