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• Need to call original function from detoured function

  - by peachykeen

  I'm using Detours to hook into an executable's message function, but I need to run my own code and then call the original code. From what I've seen in the Detours docs, it definitely sounds like that should happen automatically. The original function prints a message to the screen, but as soon as I attach a detour it starts running my code and stops printing. The original function code is roughly: void CGuiObject::AppendMsgToBuffer(classA, unsigned long, unsigned long, int, classB); My function is: void CGuiObject_AppendMsgToBuffer( [same params, with names] ); I know the memory position the original function resides in, so using: DWORD OrigPos = 0x0040592C; DetourAttach( (void*)OrigPos, CGuiObject_AppendMsgToBuffer); gets me into the function. This code works almost perfectly: my function is called with the proper parameters. However, execution leaves my function and the original code is not called. I've tried jmping back in, but that crashes the program (I'm assuming the code Detours moved to fit the hook is responsible for the crash). Edit: I've managed to fix the first issue, with no returning to program execution. By calling the OrigPos value as a function, I'm able to go to the "trampoline" function and from there on to the original code. However, somewhere along the lines the registers are changing and that is causing the program to crash with a segfault as soon as I get back into the original code.

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• Load Spikes on a Apache MySQL Server with Wordpress MU

  - by Vikram Goyal

  Hi there, I am trying to investigate the reasons for some mysterious load spikes on a Linux Apache server (2.2.14) running PHP 5.2.9 on a dedicated server with enough processing power and memory. My primary web application is a Wordpress MU (2.9.2) installation. I have investigated and ruled out DOS attack, MySQL or Apache configuration issues. The log files don't give me anything of interest, except to tell me that there is severe load. The load (which can go up to 100) just seems to come and go. It helps that I have a script that checks every 3 minutes for the load, and restarts Apache. Restarting it helps, and the server comes back, till it happens again. There seems to be no set time frame, or visitor numbers on the site that can trigger this. Even a low number of concurrent visitors (20) can trigger it. I am almost convinced that there is a rewrite loop somewhere that is causing Apache to go mad. Apache is trying to serve something that is causing it to spawn more and more processes till it keels over. My question is: Given that I am convinced that this is a rewrite issue or something similar, how can I try and figure out what the issue is? What should I monitor? Apache logs are voluminous, and not very helpful. Of course, if this is not the issue, then at least knowing what to look for will help me eliminate this as an issue and look for something else. Thanks! Vikram

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• Maintaining a pool of DAO Class instances vs doing new operator

  - by Fazal

  we have been trying to benchmark our application performance in multiple way for sometime now. I always believed that object creation in java using Class.newInstance() was not slow (at least after 1.4 version of java). But we anyways did a test to use newInstance method vs mainitain an object pool of 1000 objects. We did about 200K iterations of loading data from DB using JDBC and populating these objects. I was amazed (even shocked) to see that newInstance code compared to object pool code was almost 10 times slower. These objects represent tables with about 50 fields and all string type. Can someone share there thoughts on this issue as now I am more confused if object pooling of atleast some DAO instances is a better option. The pool size as I see right now should be large enough to meet size of average requests. There is a flip side as my memory footprint will go up but I am beginning to wonder if this kind of idea makes sense atleast for some of the DAO entities representing tables of about 50 or more columns Please share your ideas and let me know if this has been tried by someone or am I missing some point here

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• ASP.NET MVC Paging for a search form

  - by James Alexander

  I've read several different posts on paging w/ in MVC but none describe a scenario where I have something like a search form and then want to display the results of the search criteria (with paging) beneath the form once the user clicks submit. My problem is that, the paging solution I'm using will create <a href="..."> links that will pass the desired page like so: http://mysite.com/search/2/ and while that's all fine and dandy, I don't have the results of the query being sent to the db in memory or anything so I need to query the DB again. If the results are handled by the POST controller action for /Search and the first page of the data is rendered as such, how do I get the same results (based on the form criteria specified by the user) when the user clicks to move to page 2? Some javascript voodoo? Leverage Session State? Make my GET controller action have the same variables expected by the search criteria (but optional), when the GET action is called, instantiate a FormCollection instance, populate it and pass it to the POST action method (there-by satisfying DRY)? Can someone point me in the right direction for this scenario or provide examples that have been implemented in the past? Thanks!

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• use startActivityForResult from non-activity

  - by rayman

  Hi, I have MainActivity which is an Activity and other class(which is a simple java class), we`ll call it "SimpleClass". now i want to run from that class the command startActivityForResult. now i though that i could pass that class(SimpleClass), only MainActivity's context, problem is that, u cant run context.startActivityForResult(...); so the only way making SimpleClass to use 'startActivityForResult; is to pass the reference of MainActivity as an Activity variable to the SimpleClass something like that: inside the MainActivity class i create the instance of SimpleClass this way: SimpleClass simpleClass=new SimpleClass(MainActivity.this); now this is how SimpleClass looks like: public Class SimpleClass { Activity myMainActivity; public SimpleClass(Activity mainActivity) { super(); this.myMainActivity=mainActivity; } .... } public void someMethod(...) { myMainActivity.startActivityForResult(...); } now its working, but isnt a proper way of doing this? I`am afraid i could have some memory leaks in the future. thanks. ray.

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• Automatic .NET code, nhibernate session, and LINQ datacontext clean-up?

  - by AverageJoe719

  Hi all, in my goal to adopt better coding practices I have a few questions in general about automatic handling of code. I have heard different answers both from online and talking with other developers/programmers at my work. I am not sure if I should have split them into 3 questions, but they all seem sort of related: 1) How does .NET handle instances of classes and other code things that take up memory? I recently found out about using the factory pattern for certain things like service classes so that they are only instantiated once in the entire application, but then I was told that '.NET handles a lot of that stuff automatically when mentioning it.' 2) How does Nhibernate's session handle automatic clean-up of un-used things? I've seen some say that it is great at handling things automatically and you should just use a session factory and that's it, no need to close it. But I have also read and seem many examples where people close the hibernate session. 3) How does LINQ's datacontext handle this? Most of the time I never .disposed my datacontext's and the app didn't see to take a performance hit (though I am not running anything super intensively), but it seems like most people recommend disposing of your datacontext after you are done with it. However, I have seen many many code examples where the dispose method is never called. Also in general I found it kind of annoying that you couldn't access even one-deep child related objects after disposing of the datacontext unless you explicity also grabbed them in the query. Thanks all. I am loving this site so far, I kind of get lost and spend hours just reading things on here. =)

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• Is there a fast alternative to creating a Texture2D from a Bitmap object in XNA?

  - by Matthew Bowen

  I've looked around a lot and the only methods I've found for creating a Texture2D from a Bitmap are: using (MemoryStream s = new MemoryStream()) { bmp.Save(s, System.Drawing.Imaging.ImageFormat.Png); s.Seek(0, SeekOrigin.Begin); Texture2D tx = Texture2D.FromFile(device, s); } and Texture2D tx = new Texture2D(device, bmp.Width, bmp.Height, 0, TextureUsage.None, SurfaceFormat.Color); tx.SetData<byte>(rgbValues, 0, rgbValues.Length, SetDataOptions.NoOverwrite); Where rgbValues is a byte array containing the bitmap's pixel data in 32-bit ARGB format. My question is, are there any faster approaches that I can try? I am writing a map editor which has to read in custom-format images (map tiles) and convert them into Texture2D textures to display. The previous version of the editor, which was a C++ implementation, converted the images first into bitmaps and then into textures to be drawn using DirectX. I have attempted the same approach here, however both of the above approaches are significantly too slow. To load into memory all of the textures required for a map takes for the first approach ~250 seconds and for the second approach ~110 seconds on a reasonable spec computer. If there is a method to edit the data of a texture directly (such as with the Bitmap class's LockBits method) then I would be able to convert the custom-format images straight into a Texture2D and hopefully save processing time. Any help would be very much appreciated. Thanks

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• Unit testing opaque structure based C API

  - by Nicolas Goy

  I have a library I wrote with API based on opaque structures. Using opaque structures has a lot of benefits and I am very happy with it. Now that my API are stable in term of specifications, I'd like to write a complete battery of unit test to ensure a solid base before releasing it. My concern is simple, how do you unit test API based on opaque structures where the main goal is to hide the internal logic? For example, let's take a very simple object, an array with a very simple test: WSArray a = WSArrayCreate(); int foo = 5; WSArrayAppendValue(a, &foo); int *bar = WSArrayGetValueAtIndex(a, 0); if(&foo != bar) printf("Eroneous value returned\n"); else printf("Good value returned\n"); WSRelease(a); Of course, this tests some facts, like the array actually acts as wanted with 1 value, but when I write unit tests, at least in C, I usualy compare the memory footprint of my datastructures with a known state. In my example, I don't know if some internal state of the array is broken. How would you handle that? I'd really like to avoid adding codes in the implementation files only for unit testings, I really emphasis loose coupling of modules, and injecting unit tests into the implementation would seem rather invasive to me. My first thought was to include the implementation file into my unit test, linking my unit test statically to my library. For example: #include <WS/WS.h> #include <WS/Collection/Array.c> static void TestArray(void) { WSArray a = WSArrayCreate(); /* Structure members are available because we included Array.c */ printf("%d\n", a->count); } Is that a good idea? Of course, the unit tests won't benefit from encapsulation, but they are here to ensure it's actually working.

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• error detection/correction/recovery in serial protocols

  - by Jason S

  I have some designing to do for a serial protocol and am running into some questions that I figure must have been considered elsewhere. So I'm wondering if there are some recommendations for best practices in designing serial protocols. (Please either state a fact that is easily verifiable, or cite a reputable source if you make a claim.) General recommendations for websites/books are also welcome. In particular I have to deal with issues like parsing a stream of bytes into packets verifying a packet is correct (easy with a CRC, for instance) identifying reasonable types of errors that can occur (e.g. in a point-to-point serial stream, sporadic single bit errors, and dropped series of bytes, are both likely, but extra phantom bytes are unlikely; whereas with a record stored in flash memory or on a disk drive the types of errors that predominate are different) error correction or recovery (if I detect an error in a packet, can I correct it? If not, can I resync to the boundary of the next packet?) how to make variable-length packets robust to error correction / recovery. Any suggestions?

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• Optimizing MySQL for ALTER TABLE of InnoDB

  - by schuilr

  Sometime soon we will need to make schema changes to our production database. We need to minimize downtime for this effort, however, the ALTER TABLE statements are going to run for quite a while. Our largest tables have 150 million records, largest table file is 50G. All tables are InnoDB, and it was set up as one big data file (instead of a file-per-table). We're running MySQL 5.0.46 on an 8 core machine, 16G memory and a RAID10 config. I have some experience with MySQL tuning, but this usually focusses on reads or writes from multiple clients. There is lots of info to be found on the Internet on this subject, however, there seems to be very little information available on best practices for (temporarily) tuning your MySQL server to speed up ALTER TABLE on InnoDB tables, or for INSERT INTO .. SELECT FROM (we will probably use this instead of ALTER TABLE to have some more opportunities to speed things up a bit). The schema changes we are planning to do is adding a integer column to all tables and make it the primary key, instead of the current primary key. We need to keep the 'old' column as well so overwriting the existing values is not an option. What would be the ideal settings to get this task done as quick as possible?

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• how to implement a really efficient bitvector sorting in python

  - by xiao

  Hello guys! Actually this is an interesting topic from programming pearls, sorting 10 digits telephone numbers in a limited memory with an efficient algorithm. You can find the whole story here What I am interested in is just how fast the implementation could be in python. I have done a naive implementation with the module bitvector. The code is as following: from BitVector import BitVector import timeit import random import time import sys def sort(input_li): return sorted(input_li) def vec_sort(input_li): bv = BitVector( size = len(input_li) ) for i in input_li: bv[i] = 1 res_li = [] for i in range(len(bv)): if bv[i]: res_li.append(i) return res_li if __name__ == "__main__": test_data = range(int(sys.argv[1])) print 'test_data size is:', sys.argv[1] random.shuffle(test_data) start = time.time() sort(test_data) elapsed = (time.time() - start) print "sort function takes " + str(elapsed) start = time.time() vec_sort(test_data) elapsed = (time.time() - start) print "sort function takes " + str(elapsed) start = time.time() vec_sort(test_data) elapsed = (time.time() - start) print "vec_sort function takes " + str(elapsed) I have tested from array size 100 to 10,000,000 in my macbook(2GHz Intel Core 2 Duo 2GB SDRAM), the result is as following: test_data size is: 1000 sort function takes 0.000274896621704 vec_sort function takes 0.00383687019348 test_data size is: 10000 sort function takes 0.00380706787109 vec_sort function takes 0.0371489524841 test_data size is: 100000 sort function takes 0.0520560741425 vec_sort function takes 0.374383926392 test_data size is: 1000000 sort function takes 0.867373943329 vec_sort function takes 3.80475401878 test_data size is: 10000000 sort function takes 12.9204008579 vec_sort function takes 38.8053860664 What disappoints me is that even when the test_data size is 100,000,000, the sort function is still faster than vec_sort. Is there any way to accelerate the vec_sort function?

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• Fast Lightweight Image Comparisson Metric Algorithm

  - by gav

  Hi All, I am developing an application for the Android platform which contains 1000+ image filters that have been 'evolved'. When a user selects a photo I want to present the most relevant filters first. This 'relevance' should be dependent on previous use cases. I have already developed tools that register when a filtered image is saved; this combination of filter and image can be seen as the training data for my system. The issue is that the comparison must occur between selecting an image and the next screen coming up. From a UI point of view I need the whole process to take less that 4 seconds; select an image- obtain a metric to use for similarity - check against use cases - return 6 closest matches. I figure with 4 seconds I can use animations and progress dialogs to keep the user happy. Due to platform contraints I am fairly limited in the computational expense of the algorithm. I have implemented a technique adapted from various online tutorials for running C code on the G1 and hence this language is available Specific Constraints; Qualcomm® MSM7201A™, 528 MHz Processor 320 x 480 Pixel bitmap in 32 bit ARGB ~ 2 seconds computational time for the native method to get the metric ~ 2 seconds to compare the metric of the current image with training data This is an academic project so all ideas are welcome, anything you can think of or have heard about would be of interest to me. My ideas; I want to keep the complexity down (O(n*m)?) by using pixel data only rather than a neighbourhood function I was looking at using the Colour historgram/Greyscale histogram/Texture/Entropy of the image, combining them to make the measure. There will be an obvious loss of information but I need the resultant metric to be substantially smaller than the memory footprint of the image (~0.512 MB) As I said, any ideas to direct my research would be fantastic. Kind regards, Gavin

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• Using ember-resource with couchdb - how can i save my documents?

  - by Thomas Herrmann

  I am implementing an application using ember.js and couchdb. I choose ember-resource as database access layer because it nicely supports nested JSON documents. Since couchdb uses the attribute _rev for optimistic locking in every document, this attribute has to be updated in my application after saving the data to the couchdb. My idea to implement this is to reload the data right after saving to the database and get the new _rev back with the rest of the document. Here is my code for this: // Since we use CouchDB, we have to make sure that we invalidate and re-fetch // every document right after saving it. CouchDB uses an optimistic locking // scheme based on the attribute "_rev" in the documents, so we reload it in // order to have the correct _rev value. didSave: function() { this._super.apply(this, arguments); this.forceReload(); }, // reload resource after save is done, expire to make reload really do something forceReload: function() { this.expire(); // Everything OK up to this location Ember.run.next(this, function() { this.fetch() // Sub-Document is reset here, and *not* refetched! .fail(function(error) { App.displayError(error); }) .done(function() { App.log("App.Resource.forceReload fetch done, got revision " + self.get('_rev')); }); }); } This works for most cases, but if i have a nested model, the sub-model is replaced with the old version of the data just before the fetch is executed! Interestingly enough, the correct (updated) data is stored in the database and the wrong (old) data is in the memory model after the fetch, although the _rev attribut is correct (as well as all attributes of the main object). Here is a part of my object definition: App.TaskDefinition = App.Resource.define({ url: App.dbPrefix + 'courseware', schema: { id: String, _rev: String, type: String, name: String, comment: String, task: { type: 'App.Task', nested: true } } }); App.Task = App.Resource.define({ schema: { id: String, title: String, description: String, startImmediate: Boolean, holdOnComment: Boolean, ..... // other attributes and sub-objects } }); Any ideas where the problem might be? Thank's a lot for any suggestion! Kind regards, Thomas

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• Reversible pseudo-random sequence generator

  - by user350651

  I would like some sort of method to create a fairly long sequence of random numbers that I can flip through backwards and forwards. Like a machine with "next" and "previous" buttons, that will give you random numbers. Something like 10-bit resolution (i.e. positive integers in a range from 0 to 1023) is enough, and a sequence of 100k numbers. It's for a simple game-type app, I don't need encryption-strength randomness or anything, but I want it to feel fairly random. I have a limited amount of memory available though, so I can't just generate a chunk of random data and go through it. I need to get the numbers in "interactive time" - I can easily spend a few ms thinking about the next number, but not comfortably much more than that. Eventually it will run on some sort of microcontroller, probably just an Arduino. I could do it with a simple linear congruential generator (LCG). Going forwards is simple, to go backwards I'd have to cache the most recent numbers and store some points at intervals so I can recreate the sequence from there. But maybe there IS some pseudo-random generator that allows you to go both forwards and forwards? It should be possible to hook up two linear feedback shift registers (LFSRs) to roll in different directions, no? Or maybe I can just get by with garbling the index number using a hash function of some sort? I'm going to try that first. Any other ideas?

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• Fixing a multi-threaded pycurl crash.

  - by Rook

  If I run pycurl in a single thread everything works great. If I run pycurl in 2 threads python will access violate. The first thing I did was report the problem to pycurl, but the project died about 3 years ago so I'm not holding my breath. My (hackish) solution is to build a 2nd version of pycurl called "pycurl_thread" which will only be used by the 2nd thread. I downloaded the pycurl module from sourceforge and I made a total of 4 line changes. But python is still crashing. My guess is that even though this is a module with a different name (import pycurl_thread), its still sharing memory with the original module (import pycurl). How should I solve this problem? Changes in pycurl.c: initpycurl(void) to initpycurl_thread(void) and m = Py_InitModule3("pycurl", curl_methods, module_doc); to m = Py_InitModule3("pycurl_thread", curl_methods, module_doc); Changes in setup.py: PACKAGE = "pycurl" PY_PACKAGE = "curl" to PACKAGE = "pycurl_thread" PY_PACKAGE = "curl_thread" Here is the seg fault i'm getting. This is happening within the C function do_curl_perform(). *** longjmp causes uninitialized stack frame ***: python2.7 terminated ======= Backtrace: ========= /lib/libc.so.6(__fortify_fail+0x37)[0x7f209421b537] /lib/libc.so.6(+0xff4c9)[0x7f209421b4c9] /lib/libc.so.6(__longjmp_chk+0x33)[0x7f209421b433] /usr/lib/libcurl.so.4(+0xe3a5)[0x7f20931da3a5] /lib/libpthread.so.0(+0xfb40)[0x7f209532eb40] /lib/libc.so.6(__poll+0x53)[0x7f20941f6203] /usr/lib/libcurl.so.4(Curl_socket_ready+0x116)[0x7f2093208876] /usr/lib/libcurl.so.4(+0x2faec)[0x7f20931fbaec] /usr/local/lib/python2.7/dist-packages/pycurl.so(+0x892b)[0x7f209342c92b] python2.7(PyEval_EvalFrameEx+0x58a1)[0x4adf81] python2.7(PyEval_EvalCodeEx+0x891)[0x4af7c1] python2.7(PyEval_EvalFrameEx+0x538b)[0x4ada6b] python2.7(PyEval_EvalFrameEx+0x65f9)[0x4aecd9]

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• vector::erase with pointer member

  - by matt

  I am manipulating vectors of objects defined as follow: class Hyp{ public: int x; int y; double wFactor; double hFactor; char shapeNum; double* visibleShape; int xmin, xmax, ymin, ymax; Hyp(int xx, int yy, double ww, double hh, char s): x(xx), y(yy), wFactor(ww), hFactor(hh), shapeNum(s) {visibleShape=0;shapeNum=-1;}; //Copy constructor necessary for support of vector::push_back() with visibleShape Hyp(const Hyp &other) { x = other.x; y = other.y; wFactor = other.wFactor; hFactor = other.hFactor; shapeNum = other.shapeNum; xmin = other.xmin; xmax = other.xmax; ymin = other.ymin; ymax = other.ymax; int visShapeSize = (xmax-xmin+1)*(ymax-ymin+1); visibleShape = new double[visShapeSize]; for (int ind=0; ind<visShapeSize; ind++) { visibleShape[ind] = other.visibleShape[ind]; } }; ~Hyp(){delete[] visibleShape;}; }; When I create a Hyp object, allocate/write memory to visibleShape and add the object to a vector with vector::push_back, everything works as expected: the data pointed by visibleShape is copied using the copy-constructor. But when I use vector::erase to remove a Hyp from the vector, the other elements are moved correctly EXCEPT the pointer members visibleShape that are now pointing to wrong addresses! How to avoid this problem? Am I missing something?

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• Segmentation fault on writing char to char* address

  - by Lukas Dojcak

  hi guys, i've got problem with my little C program. Maybe you could help me. char* shiftujVzorku(char* text, char* pattern, int offset){ char* pom = text; int size = 0; int index = 0; while(*(text + size) != '\0'){ size++; } while(*(pom + index) != '\0'){ if(overVzorku(pom + index, pattern)){ while(*pattern != '\0'){ //vyment *pom s *pom + offset if(pom + index + offset < text + size){ char x = *(pom + index + offset); char y = *(pom + index); int adresa = *(pom + index + offset); *(pom + index + offset) = y; <<<<<< SEGMENTATION FAULT *(pom + index) = x; //*pom = *pom - *(pom + offset); //*(pom + offset) = *(pom + offset) + *pom; //*pom = *(pom + offset) - *pom; } else{ *pom = *pom - *(pom + offset - size); *(pom + offset - size) = *(pom + offset - size) + *pom; *pom = *(pom + offset - size) - *pom; } pattern++; } break; } index++; } return text; } Isn't important what's the programm doing. Mayby there's lot of bugs. But, why do I get SEGMENTATION FAULT (for destination see code) at this line? I'm, trying to write some char value to memory space, with help of address "pom + offset + index". Thanks for everything helpful. :)

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• AS3 using PrintJob to print a MovieClip

  - by Chris Waugh

  Hello, I am currently trying to create a function which will allow me to pass in a movieclip and print it. Here is the simplified version of the function: function printMovieClip(clip:MovieClip) { var printJob:PrintJob = new PrintJob(); var numPages:int = 0; var printY:int = 0; var printHeight:Number; if ( printJob.start() ) { /* Resize movie clip to fit within page width */ if (clip.width > printJob.pageWidth) { clip.width = printJob.pageWidth; clip.scaleY = clip.scaleX; } numPages = Math.ceil(clip.height / printJob.pageHeight); /* Add pages to print job */ for (var i:int = 0; i < numPages; i++) { printJob.addPage(clip, new Rectangle(0, printY, printJob.pageWidth, printJob.pageHeight)); printY += printJob.pageHeight; } /* Send print job to printer */ printJob.send(); /* Delete job from memory */ printJob = null; } } printMovieClip( testMC ); Unfortunately this is not working as expected i.e. printing the full width of the Movieclip and doing page breaks on the length. Any help with this would be greatly appreciated. Many thanks, Chris

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• How to handle error with content-disposition

  - by František Žiacik

  Hi, how should I handle an exception that occurs after sending a Content-Disposition header for an attachment? I'm trying to generate a report at server and send it as a file, but if an exception occurs during the report generation, the error message itself is sent to browser which still takes it as a content of a file and shows a Save As dialog. User cannot know there was an error generating report, saves the file which is in wrong format now. Is there a way to cancel the response with this header and redirect to an error page? Or what else can I do to inform user about the error? Probably I could generate the report first and only if there was no error send the headers, but I want the report render directly to the Response output stream so that it does not need to stay in memory. Here is my code: this.Response.ContentType = "application/octet-stream"; this.Response.AddHeader("Content-Disposition", @"attachment; filename=""" + item.Name + @""""); this.Response.Flush(); GenerateReportTo(this.Response.OutputStream); // Exception occurs Thanks for any suggestions

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• Passing data between ViewControllers versus doing local Fetch in each VC

  - by Tofrizer

  Hi All, I'm developing an iPhone app using Core Data and I'm looking for some general advice and recommendations on whether its acceptable to pass data between ViewControllers versus doing a local fetch in each ViewController as you navigate to it. Ordinarily I would say it all depends on various factors (e.g. performance etc) but the passing data approach is so prevalent in my app and I'm spooked by all the stories about Apple rejecting apps because of not conforming to their standard guidelines. So let me put another way -- is it non-standard to pass data between VC's? The reason I pass data so much is because each ViewController is just another view on to data present in my object model / graph. Once I have a handle on my first object in the first view controller (which I of course do have to fetch), I can use the existing object composition / relationships to drill down into the next level of detail into data and so I just pass these objects to the next VC. Separately, one possible downside with this passing-data-to-each-VC approach is I don't benefit from (what I perceive to be) the optimisation/benefits that NSFetchedResultsController provides in terms of efficient memory usage and section handling. My app is read-only but I do have one table with 5000 rows and I'm curious if I am missing out on NSFetchedResultsController benefits. Any thoughts on this as well? Can I somehow still benefit from NSFetchedResultsController goodness without having to do a full fetch (as I would have already passed in the data from my previous VC)? Thanks a lot.

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• Is there a way to get number of connections in Signalr hub group?

  - by pajo

  Here is my problem, I want to track if user is online or offline and notify other clients about it. I'm using hubs and implemented both IConnected and IDisconnect interfaces. My idea was to send notification to all clients when hub detects connect or disconnect. By default when user refreshes page he will get new connection id and eventually previous connection will call disconnect notifying other clients user is offline even though he's actually online. I tired to use my own ConnectionIdFactory returning username for connection id but with multiple tabs opened at some point it will detect user connectionid disconnected and after that client side hub will try to unsuccessfully connect to the hub in endless loop wasting memory and cpu making browser almost unusable. I needed to fix it fast so I removed my factory and now I add every new connection to the group using username, so I can easily notify single user on all connections, but then I have problem of detecting if user is online or offline as I don't know how many active connection user is having. So I'm wondering is there a way to get number of connections in one group? Or if anybody has some better idea how to track when user goes offline? I'm using Signalr 0.4

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• Our Flash Streaming Player Occasionally Stutters like a Skipping CD after a Period of Time

  - by Jonathan Fritz

  We offer a streaming player for a number of our clients, who are responsible for their providing us with their own audio streams. We have written a very simple flash player that can play all of the streams that we support (icecast/shoutcast/live365/mp3 over http/etc). Unfortunately, we have found that when listening, our player sometimes begins to stutter (like a skipping cd), sometimes after only 10 minutes, and sometimes after an hour of listening. We have noticed this behaviour in firefox on both linux and windows. Does anybody know anything about this problem? We know that flash isn't ideal for infinite streams of audio, but it's about all that we can find that's on every platform out there. If anybody can suggest a solution to our problem, I'll be your friend forever. Here is a link to the live player: http://cr-jf.jfritz.02.dev.wecreate.com/streaming/player_v5/ Note that you'll need to test in a browser that isn't IE, because we use WMP in IE, and that the JavaScript on the page will cause the player to unload and re-load once an hour because of memory issues. Because I can only put one hyperlink in a post, I'll add a link to the player source code as a comment. Thanks all!

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• "Downloading" a computed value form JavaScript

  - by Travis Jensen

  I'm hoping you can prove me wrong here (please, please, please! ;). I have a situation where I need to download encrypted data from a Server D (for "Data"). Server K (for "Key") has the encryption key. For security sake, I would really prefer that Server D never know the key that Server K knows. What I want is my client (e.g. your browser) to connect to Server D for the data and Server K for the key and doe the decryption locally so the unencrypted stuff never leaves your computer. I can do this fine for text areas in the dom by replacing the contents of the HTML. However, sometimes, I would like to do larger files that I stream to the file system. For instance, perhaps I want to encrypt a movie and decrypt it and stream the contents to the my video player. I am not a JavaScript guru by any stretch, especially when it comes to the edge cases of things like the security sandbox. For Small D, I can handle the decryption, but I don't know how to save the decrypted file. Large D seems problematic as memory runs out. Anybody have any ideas that don't involve native plugins? Thanks!

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• Can I load a UIImage from a URL?

  - by progrmr

  I have a URL for an image (got it from UIImagePickerController) but I no longer have the image in memory (the URL was saved from a previous run of the app). Can I reload the UIImage from the URL again? I see that UIImage has a imageWithContentsOfFile: but I have a URL. Can I use NSData's dataWithContentsOfURL: to read the URL? EDIT based on @Daniel's answer I tried the following code but it doesn't work... NSLog(@"%s %@", __PRETTY_FUNCTION__, photoURL); if (photoURL) { NSURL* aURL = [NSURL URLWithString:photoURL]; NSData* data = [[NSData alloc] initWithContentsOfURL:aURL]; self.photoImage = [UIImage imageWithData:data]; [data release]; } When I ran it the console shows: -[PhotoBox willMoveToWindow:] file://localhost/Users/gary/Library/Application%20Support/iPhone%20Simulator/3.2/Media/DCIM/100APPLE/IMG_0004.JPG *** -[NSURL length]: unrecognized selector sent to instance 0x536fbe0 *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[NSURL length]: unrecognized selector sent to instance 0x536fbe0' Looking at the call stack, I'm calling URLWithString, which calls URLWithString:relativeToURL:, then initWithString:relativeToURL:, then _CFStringIsLegalURLString, then CFStringGetLength, then forwarding_prep_0, then forwarding, then -[NSObject doesNotRecognizeSelector]. Any ideas why my NSString (photoURL's address is 0x536fbe0) doesn't respond to length? Why does it say it doesn't respond to -[NSURL length]? Doesn't it know that param is an NSString, not a NSURL?

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• Convert asp.net webforms logic to asp.net MVC

  - by gmcalab

  I had this code in an old asp.net webforms app to take a MemoryStream and pass it as the Response showing a PDF as the response. I am now working with an asp.net MVC application and looking to do this this same thing, but how should I go about showing the MemoryStream as PDF using MVC? Here's my asp.net webforms code: private void ShowPDF(MemoryStream ms) { try { //get byte array of pdf in memory byte[] fileArray = ms.ToArray(); //send file to the user Page.Response.Cache.SetCacheability(HttpCacheability.NoCache); Page.Response.Buffer = true; Response.Clear(); Response.ClearContent(); Response.ClearHeaders(); Response.Charset = string.Empty; Response.ContentType = "application/pdf"; Response.AddHeader("content-length", fileArray.Length.ToString()); Response.AddHeader("Content-Disposition", "attachment;filename=TID.pdf;"); Response.BinaryWrite(fileArray); Response.Flush(); Response.Close(); } catch { // and boom goes the dynamite... } }

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