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• Handling close-to-impossible collisions on should-be-unique values

  - by balpha

  There are many systems that depend on the uniqueness of some particular value. Anything that uses GUIDs comes to mind (eg. the Windows registry or other databases), but also things that create a hash from an object to identify it and thus need this hash to be unique. A hash table usually doesn't mind if two objects have the same hash because the hashing is just used to break down the objects into categories, so that on lookup, not all objects in the table, but only those objects in the same category (bucket) have to be compared for identity to the searched object. Other implementations however (seem to) depend on the uniqueness. My example (that's what lead me to asking this) is Mercurial's revision IDs. An entry on the Mercurial mailing list correctly states The odds of the changeset hash colliding by accident in your first billion commits is basically zero. But we will notice if it happens. And you'll get to be famous as the guy who broke SHA1 by accident. But even the tiniest probability doesn't mean impossible. Now, I don't want an explanation of why it's totally okay to rely on the uniqueness (this has been discussed here for example). This is very clear to me. Rather, I'd like to know (maybe by means of examples from your own work): Are there any best practices as to covering these improbable cases anyway? Should they be ignored, because it's more likely that particularly strong solar winds lead to faulty hard disk reads? Should they at least be tested for, if only to fail with a "I give up, you have done the impossible" message to the user? Or should even these cases get handled gracefully? For me, especially the following are interesting, although they are somewhat touchy-feely: If you don't handle these cases, what do you do against gut feelings that don't listen to probabilities? If you do handle them, how do you justify this work (to yourself and others), considering there are more probable cases you don't handle, like a supernonva?

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• How to convert Big Endian and how to flip the highest bit?

  - by Robert Frank

  I am using a TStream to read binary data (thanks to this post: http://stackoverflow.com/questions/2878180/how-to-use-a-tfilestream-to-read-2d-matrices-into-dynamic-array). My next problem is that the data is Big Endian. From my reading, the Swap() method is seemingly deprecated. How would I swap the types below? 16-bit two's complement binary integer 32-bit two's complement binary integer 64-bit two's complement binary integer IEEE single precision floating-point - Are IEEE affected by Big Endian? And, finally, since the data is unsigned, the creators of this dataset have stored the unsigned values as signed integers (excluding the IEEE). They instruct that one need only add an offset (2^15, 2^31, and 2^63) to recover the unsigned data. But, they note that flipping the most significant bit is the fastest way to do that. How does one efficiently flip the most significant bit of a 16, 32, or 64-bit integer? So, if the data on disk (16-bit) is "85 FB" - the desired result after reading the data and swapping and bit flipping would be 1531. Is there a way to accomplish the swapping and bit flipping with generics so it fits into the generic answer at the link above? Yes, kids, THIS is how scientific astronomical data is stored by NASA, ESO, and all professional astronomers. This FITS standard is considered by some to be one of the most successful standards ever created in its proliferation and flexibility!

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• Cocoa - calling a VIEW method from the CONTROLLER

  - by eemerge

  Hello everyone, Got a little problem i asked about it before but maybe i didnt ask properly. I have a cocoa application, which amongst other things, must do the following task: - load some images from the disk, store them in an array and display them in a custom view. In the Interface Builder i have a CustomView and an OBJECT that points to TexturesController.h The custom view is a custom class, TextureBrowser. Below is the code for the controller and view: TexturesController #import <Cocoa/Cocoa.h> @class TextureBrowser; @interface TexturesController : NSObject { IBOutlet NSTextField *logWindow; IBOutlet TextureBrowser *textureView; NSMutableArray *textureList; } @property textureView; -(IBAction)loadTextures:(id)sender; -(IBAction)showTexturesInfo:(id)sender; @end TextureBrowser @interface TextureBrowser : NSView { NSMutableArray *textures; } @property NSMutableArray *textures; -(void)loadTextureList:(NSMutableArray *)source; @end These are just the headers. Now , what i need to do is: when loadTextures from the TexturesController is called, after i load the images i want to send this data to the view (TextureBrowser), for example, store it in the NSMutableArray *textures. I tried using the -(void)loadTextureList:(NSMutableArray*)source method from the view, but in the TextureController.m i get a warning : No -loadTextureList method found This is how i call the method : [textureView loadTextureList: textureList]; And even if i run it with the warning left there, the array in the view class doesnt get initialised. Maybe im missing something...maybe someone can give a simple example of what i need to do and how to do it (code). Thanks in advance.

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• Is it possible to De-Serialize a new Derived class using Old Binary?

  - by Anand

  In my project I have a class which I Serialize in Binary format to the disk. Due to some new requirement I need to create a new class which is derived from the original class. eg [Serializable] public class Sample { String someString; int someInt; public Sample() { } public Sample(String _someString, int _someInt) { this.someInt = _someInt; this.someString = _someString; } public String SomeString { get { return someString; } } public int SomeInt { get { return someInt; } } } [Serializable] public class DerivedSample : Sample { String someMoreString; int someMoreInt; public DerivedSample () : base() { } public DerivedSample (String _someString, int _someInt, String _someMoreString, int _someMoreInt) : base(_someString, _someInt) { this.someMoreString = _someMoreString; this.someMoreInt = _someMoreInt; } public String SomeMoreString { get { return someMoreString; } } public int SomeMoreInt { get { return someMoreInt; } } } When I try to De serialize an old file which contains only object of Sample it works fine, in the current assembly. That means backward compatibility is there. But when I try to deserialize the file which contains object of DerivedSample using the previous version of the assembly application crashes. Which means forward compatibilty needs to be taken care off... It it possible to say read only the base class part of the object from new version of the file?

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• Ideal HTTP cache control headers for different types of resources

  - by chris_l

  I want to find a minimal set of headers, that work with "all" caches and browsers (also when using HTTPS!) On my (GWT-based) web site, I'll have three kinds of resources: 1. Forever cacheable (public / equal for all users) These files don't ever change, and they get a filename based on the MD5 of their contents (this is GWT's approach). They should get cached as much as possible, even when using HTTPS (so I assume, I should set Cache-Control: public, especially for Firefox?) 2. Changing for every new version of the site (public / equal for all users) These files can be cached, but probably need to be revalidated every time. 3. Individual for each request (private / user specific) These resources (e. g. JSON responses) should never be cached unencrypted to disk under no circumstances. (Maybe I'll have a few specific requests that could be cached.) I have a general idea on which headers I would probably use for each type, but there's always something I could be missing.

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• ASP.NET Image Upload Parameter Not Valid. Exception

  - by pennylane

  Hi Guys, Im just trying to save a file to disk using a posted stream from jquery uploadify I'm also getting Parameter not valid. On adding to the error message so i can tell where it blew up in production im seeing it blow up on: var postedBitmap = new Bitmap(postedFileStream) any help would be most appreciated public string SaveImageFile(Stream postedFileStream, string fileDirectory, string fileName, int imageWidth, int imageHeight) { string result = ""; string fullFilePath = Path.Combine(fileDirectory, fileName); string exhelp = ""; if (!File.Exists(fullFilePath)) { try { using (var postedBitmap = new Bitmap(postedFileStream)) { exhelp += "got past bmp creation" + fullFilePath; using (var imageToSave = ImageHandler.ResizeImage(postedBitmap, imageWidth, imageHeight)) { exhelp += "got past resize"; if (!Directory.Exists(fileDirectory)) { Directory.CreateDirectory(fileDirectory); } result = "Success"; postedBitmap.Dispose(); imageToSave.Save(fullFilePath, GetImageFormatForFile(fileName)); } exhelp += "got past save"; } } catch (Exception ex) { result = "Save Image File Failed " + ex.Message + ex.StackTrace; Global.SendExceptionEmail("Save Image File Failed " + exhelp, ex); } } return result; }

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• Can I use Eclipse JDT to create new 'working copies' of source files in memory only?

  - by RYates

  I'm using Eclipse JDT to build a Java refactoring platform, for exploring different refactorings in memory before choosing one and saving it. I can create collections of working copies of the source files, edit them in memory, and commit the changes to disk using the JDT framework. However, I also want to generate new 'working copy' source files in memory as part of refactorings, and only create the corresponding real source file if I commit the working copy. I have seen various hints that this is possible, e.g. http://www.jarvana.com/jarvana/view/org/eclipse/jdt/doc/isv/3.3.0-v20070613/isv-3.3.0-v20070613.jar!/guide/jdt%5Fapi%5Fmanip.htm says "Note that the compilation unit does not need to exist in the Java model in order for a working copy to be created". So far I have only been able to create a new real file, i.e. ICompilationUnit newICompilationUnit = myPackage.createCompilationUnit(newName, "package piffle; public class Baz{private int i=0;}", false, null); This is not what I want. Does anyone know how to create a new 'working copy' source file, that does not appear in my file system until I commit it? Or any other mechanism to achieve the same thing?

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• How to keep windows from paging block of memory

  - by photo_tom

  We are working on a Vista/Windows 7 applicaiton that will be running in 64 bit mode using VS2008/C++. We will be needing to cache hundreds of 2-3 mb blobs of data in RAM for performance reasons up to some memory limit. Our usage profile is such that we cannot read the data in fast enough if it is all on the the disk. Cached Memory usage will be larger than 1gb memory used. For this to work well, we need to ensure that Windows does not page this memory out as it will defeat the purpose of why we are doing this. I've done a fair amount of research and cannot find documenation that states exactly how to do this. I've seen several references that infer memory mapped files work this way. Is there an expert who can clarify this for me? I'm aware there are other programs that we could adapt to do this, for example, splitting the blobs and loading into memcache or inmemory databases, but they all have too many problems with performance or code complexity. Suggestions?

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• How to check a file saving is complete using Python?

  - by indrajithk

  I am trying to automate a downloading process. In this I want to know, whether a particular file's save is completed or not. The scenario is like this. Open a site address using either Chrome or Firefox (any browser) Save the page to disk using 'Crtl + S' (I work on windows) Now if the page is very big, then it takes few seconds to save. I want to parse the html once the save is complete. Since I don't have control on the browser save functionality, I don't know whether the save has completed or not. One idea I thought, is to get the md5sum of the file using a while loop, and check against the previous one calculated, and continue the while loop till the md5 sum from the previous and current one matches. This doesn't works I guess, as it seems browser first attempts to save the file in a tmp file and then copies the content to the specified file (or just renames the file). Any ideas? I use python for the automation, hence any idea which can be implemented using python is welcome. Thanks Indrajith

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• How can I use a meter-style progress bar?

  - by Yadyn

  In Vista/7, the Windows Explorer shell window makes use of a special kind of static progress bar to display hard drive space. With default styles, this bar is blue colored and non-animated. It also turns red colored when it gets close to being full (low disk space). Using messaging, I can tell the Windows Forms ProgressBar control to update its state to Paused and Error (yellow and red colored, respectively), which works fine, but these are still specific to progress. In the Windows User Experience Guidelines, it specifically points out this "meter" variant of the Progress Bar: This pattern isn't a progress bar, but it is implemented using the progress bar control. Meters have a distinct look to differentiate them from true progress bars. They say it "is implemented using the progress bar control", so... how? What message could I send to the control to have it behave this way? I've seen that you can send messages for setting the bar color, but the documentation says these calls are ignored when visual styles are enabled. Nothing else in the Windows API documentation for raw ProgressBar controls seemed to suggest a way to do this. Am I just stuck making a custom drawn bar? I'd really like to utilize the OS whenever possible so that the application will appear consistent throughout different OS versions. I realize that pre-Vista versions probably won't support this, though. I'm looking for a Windows Forms solution, but I wonder if it is even exposed at all via Win32 API.

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• How to speed up a slow UPDATE query

  - by Mike Christensen

  I have the following UPDATE query: UPDATE Indexer.Pages SET LastError=NULL where LastError is not null; Right now, this query takes about 93 minutes to complete. I'd like to find ways to make this a bit faster. The Indexer.Pages table has around 506,000 rows, and about 490,000 of them contain a value for LastError, so I doubt I can take advantage of any indexes here. The table (when uncompressed) has about 46 gigs of data in it, however the majority of that data is in a text field called html. I believe simply loading and unloading that many pages is causing the slowdown. One idea would be to make a new table with just the Id and the html field, and keep Indexer.Pages as small as possible. However, testing this theory would be a decent amount of work since I actually don't have the hard disk space to create a copy of the table. I'd have to copy it over to another machine, drop the table, then copy the data back which would probably take all evening. Ideas? I'm using Postgres 9.0.0. UPDATE: Here's the schema: CREATE TABLE indexer.pages ( id uuid NOT NULL, url character varying(1024) NOT NULL, firstcrawled timestamp with time zone NOT NULL, lastcrawled timestamp with time zone NOT NULL, recipeid uuid, html text NOT NULL, lasterror character varying(1024), missingings smallint, CONSTRAINT pages_pkey PRIMARY KEY (id ), CONSTRAINT indexer_pages_uniqueurl UNIQUE (url ) ); I also have two indexes: CREATE INDEX idx_indexer_pages_missingings ON indexer.pages USING btree (missingings ) WHERE missingings > 0; and CREATE INDEX idx_indexer_pages_null ON indexer.pages USING btree (recipeid ) WHERE NULL::boolean; There are no triggers on this table, and there is one other table that has a FK constraint on Pages.PageId.

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• What is the fastest way to get a DataTable into SQL Server?

  - by John Gietzen

  I have a DataTable in memory that I need to dump straight into a SQL Server temp table. After the data has been inserted, I transform it a little bit, and then insert a subset of those records into a permanent table. The most time consuming part of this operation is getting the data into the temp table. Now, I have to use temp tables, because more than one copy of this app is running at once, and I need a layer of isolation until the actual insert into the permanent table happens. What is the fastest way to do a bulk insert from a C# DataTable into a SQL Temp Table? I can't use any 3rd party tools for this, since I am transforming the data in memory. My current method is to create a parameterized SqlCommand: INSERT INTO #table (col1, col2, ... col200) VALUES (@col1, @col2, ... @col200) and then for each row, clear and set the parameters and execute. There has to be a more efficient way. I'm able to read and write the records on disk in a matter of seconds...

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• Gradual memory leak and slowdown in loop

  - by Benji XVI

  I have a simple foundation tool that exports every frame of a movie as a .tiff file. Here is the relevant code: NSString* movieLoc = [NSString stringWithCString:argv[1]]; QTMovie *sourceMovie = [QTMovie movieWithFile:movieLoc error:nil]; int i=0; while (QTTimeCompare([sourceMovie currentTime], [sourceMovie duration]) != NSOrderedSame) { // save image of movie to disk NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSString *filePath = [NSString stringWithFormat:@"/somelocation_%d.tiff", i++]; NSData *currentImageData = [[sourceMovie currentFrameImage] TIFFRepresentation]; [currentImageData writeToFile:filePath atomically:NO]; NSLog(@"%@", filePath); [sourceMovie stepForward]; [arp release]; } [pool drain]; return 0; As you can see, in order to prevent very large memory buildups with the various transparently-autoreleased variables in the loop, we create, and flush, an autoreleasepool with every run through the loop. However, over the course of stepping through a movie, the amount of memory used by the program still gradually increases, and the speed at which frames are processed drops precipitously. (From ~0.5 seconds per frame at the start, to ~2 seconds per frame by the 250th frame.) The only thing I can think can be causing the gradual memory leak is a buildup of the NSAutoreleasePool objects themselves. Am I right in thinking they will only be deallocated when the outer pool is released? If so, is there a better memory management solution here? Creating a pool every run through the loop seems a little hacky. And if not, what is causing the slow memory leak? (It is not NSStrings, and much too slow to be NSImages or NSDatas.) And what could be causing the slowdown?

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• How to rename an private file of my application?

  - by Ungureanu Liviu

  Hi! I want to rename an context private file created with openFileOutput() but I don't know how... I tried that: File file = getFileStreamPath(optionsMenuView.getPlaylistName()); // this file already exists try { FileOutputStream outStream = openFileOutput(newPlaylistName, Context.MODE_WORLD_READABLE); // i create a new file with the new name outStream.close(); } catch (FileNotFoundException e) { Log.e(TAG, "file not found!"); e.printStackTrace(); } catch (IOException e) { Log.e(TAG, "IO exception"); e.printStackTrace(); } Log.e(TAG, "rename status: " + file.renameTo(getFileStreamPath(newPlaylistName))); //it return true This code throw FileNotFoundException but the documentation said "Open a private file associated with this Context's application package for writing. Creates the file if it doesn't already exist." so the new file should be created on disk. The problem: When I try to read from the new renamed file I got FileNotFoundException! Thank you!

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• unbuffered I/O in Linux

  - by stuck

  I'm writing lots and lots of data that will not be read again for weeks - as my program runs the amount of free memory on the machine (displayed with 'free' or 'top') drops very quickly, the amount of memory my app uses does not increase - neither does the amount of memory used by other processes. This leads me to believe the memory is being consumed by the filesystems cache - since I do not intend to read this data for a long time I'm hoping to bypass the systems buffers, such that my data is written directly to disk. I dont have dreams of improving perf or being a super ninja, my hope is to give a hint to the filesystem that I'm not going to be coming back for this memory any time soon, so dont spend time optimizing for those cases. On Windows I've faced similar problems and fixed the problem using FILE_FLAG_NO_BUFFERING|FILE_FLAG_WRITE_THROUGH - the machines memory was not consumed by my app and the machine was more usable in general. I'm hoping to duplicate the improvements I've seen but on Linux. On Windows there is the restriction of writing in sector sized pieces, I'm happy with this restriction for the amount of gain I've measured. is there a similar way to do this in Linux?

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• Memory Leak in returning NSMutableArray from class

  - by Structurer

  Hi I am quite new to Objective C for the iPhone, so I hope you wont kill me for asking a simple question. I have made an App that works fine, except that Instruments reports memory leaks from the class below. I use it to store settings from one class and then retrieve them from another class. These settings are stored on a file so they can be retrieved every time the App is ran. What can I do do release the "setting" and is there anything that can be done to call (use) the class in a smarter way? Thanks ----- Below is Settings.m ----- import "Settings.h" @implementation Settings @synthesize settings; -(NSString *)dataFilePath // Return path for settingfile, including filename { NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0]; return [documentsDirectory stringByAppendingPathComponent:kUserSettingsFileName]; } -(NSMutableArray *)getParameters // Return settings from disk after checking if file exist (if not create with default values) { NSString *filePath = [self dataFilePath]; if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) // Getting data from file { settings = [[NSMutableArray alloc] initWithContentsOfFile:filePath]; } else // Creating default settings { settings = [[NSMutableArray alloc] initWithObjects: [NSNumber numberWithInteger:50], [NSNumber numberWithInteger:50], nil]; [settings writeToFile:[self dataFilePath] atomically:YES]; } return settings; } ----- Below is my other class from where I call my Settings class ----- // Get settings from file Settings *aSetting = [[Settings alloc] init]; mySettings = [aSetting getParameters]; [aSetting release];

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• Cross-platform build UNC share (Windows->Linux) - possible to be case-sensitive on CIFS share?

  - by holtavolt

  To optimize builds between Windows and Linux (Ubuntu 10.04), I've got a UNC share of the source tree that is shared between systems, and all build output goes to local disk on each system. This mostly works great, as source updates and changes can quickly be tested on both systems, but there's one annoying limitation I can't find a way around, which is that the Linux CIFS mount is case-insensitive. Consequently, a test compile of code that has an error like: #include "Foo.h" for a file foo.h, will not be caught by a test build (until a local compile is done on the Linux box, e.g. nightly builds) Is it possible to have case-sensitivity of the Windows UNC share on the Linux box? I've tried a variety of fstab and mount combinations with no success, as well as editing the smb.config to set "case sensitive = yes" Given what the Ubuntu man page info states on this: nocase Request case insensitive path name matching (case sensitive is the default if the server suports it). I suspect that this is a limitation from the Windows UNC side, and there's nothing to be done short of switching to some other mechanism (is NFS still viable anywhere?) If anyone has already solved this to support optimized cross-platform build environments, I'd appreciate hearing about it!

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• AsyncTask never finishes when other tasks are running

  - by rebeccamaher

  In my app, I show a menu screen immediately to the user and then use an AsyncTask to load some data from disk. Loading takes about 3 seconds if that's all the app had to do. When the user hits a menu option and the data hasn't loaded yet, a "Please wait, loading" screen appears. I have two problems: I recently added ads to my app and have found this is making my app hang sometimes because the AsyncTask never finishes loading. What seems to be happening is that the ad banner (I'm using admob and this happens when adsense ads are shown which admob do occasionally) is using resources by playing a simple animation and the AsyncTask never gets a chance to finish. I want to play a simple looping animation (e.g. making a view rotate) on my menu screen and this makes the AsyncTask take about 5 times longer to finish which renders the background loading pointless. How can I avoid situations where my background data never finishes loading or has such a low priority it takes a long time? I can't seem to find a way to increase the priority of an AsyncTask.

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• SQLite DB open time really long Problem

  - by sxingfeng

  I am using sqlite in c++ windows, And I have a db size about 60M, When I open the sqlite db, It takes about 13 second. sqlite3* mpDB; nRet = sqlite3_open16(szFile, &mpDB); And if I closed my application and reopen it again. It takse only less then 1 second. First, I thought It is because of disk cache. So I preload the 60M db file before sqlite open, and read the file using CFile, However, after preloading, the first time is still very slow. BOOL CQFilePro::PreLoad(const CString& strPath) { boost::shared_array<BYTE> temp = boost::shared_array<BYTE>(new BYTE[PRE_LOAD_BUFFER_LENGTH]); int nReadLength; try { CFile file; if (file.Open(strPath, CFile::modeRead) == FALSE) { return FALSE; } do { nReadLength = file.Read(temp.get(), PRE_LOAD_BUFFER_LENGTH); } while (nReadLength == PRE_LOAD_BUFFER_LENGTH); file.Close(); } catch(...) { } return TRUE; } My question is what is the difference between first open and second open. How can I accelerate the sqlite open-process.

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• Images won't load if they are of high size

  - by Fahim Parkar

  I have created web-application using JSF 2.0 and mysql. I am storing images in DB using MEDIUMBLOB. When I try to load image, I am able to see those images. However if the image size is big (1 MB or more), I can see half or 3/4th image on the browser. Any idea how to overcome this issue? Do I need to set any variable in JSF or MySQL? I know I should have saved the images over disk instead of DB, however this was client requirement. Client wanted to backup data and provide it to someone else and client don't want to backup DB and images also. Edit 1 Do I need to set any variables on mysql like query_cache. Edit 2 When I download same image and put below code it works perfectly. <h:graphicImage value="images/myImage4.png" width="50%" /> Edit 3 code is as below. <h:graphicImage value="DisplayImage?mainID=drawing" /> DisplayImage.java String imgLen = rs1.getString(1); int len = imgLen.length(); byte[] rb = new byte[len]; InputStream readImg = rs1.getBinaryStream(1); InputStream inputStream = readImg; int index = readImg.read(rb, 0, len); response.reset(); response.setHeader("Content-Length", String.valueOf(len)); response.setHeader("Content-disposition", "inline;filename=/file.png"); response.setContentType("image/png"); response.getOutputStream().write(rb, 0, len); response.getOutputStream().flush(); When I print len I get value as len=1548432

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• Actionscript: How Can I Know When The Source Property Of An Image Is Completely Updated

  - by Joshua

  var I:Image=new Image(); I.source='C:\\Abc.png'; var H:int=I.height; H is always Zero! I am presuming this is because the image hasn't finished reading the png file off the disk yet. What event can I monitor to know when it's width and height will have the right values? The 'Complete' event only seems to work for DOWNLOADED images. The 'Render' event happens EVERY FRAME. The (undocumented?) 'sourceChanged', happens as soon as source changes, and has the same problem! What event do I watch that will let me know when the image's width and height properties will have valid values? Or is there some Synchronous version of I.source='xxx.png', that I don't know about? P.S. Yes, I know I shouldn't use "C:\" in an Air Program. This was just for illustrative purposes, so that you won't suggest I use "Complete", which never even seems to fire when the file indicated by source is local.

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• Memory mapping of files and system cache behavior in WinXP

  - by Canopus

  Our application is memory intensive and deals with reading a large number of disk files. The total load can be more than 3 GB. There is a custom memory manager that uses memory mapped files to achieve reading of such a huge data. The files are mapped into the process memory space only when needed and with this the process memory is well under control. But what is observed is, with memory mapping, the system cache keeps on increasing until it occupies the available physical memory. This leads to the slowing down of the entire system. My question is how to prevent system cache from hogging the physical memory? I attempted to remove the file buffering (by using FILE_FLAG_NO_BUFFERING ), but with this, the read operations take considerable amount of time and slows down the application performance. How to achieve the scalability without sacrificing much on performance. What are the common techniques used in such cases? I dont have a good understanding of the WinXP OS caching behavior. Any good links explaining the same would also be helpful.

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• Optimize INSERT / UPDATE / DELETE operation

  - by clime

  I wonder if the following script can be optimized somehow. It does write a lot to disk because it deletes possibly up-to-date rows and reinserts them. I was thinking about applying something like "insert ... on duplicate key update" and found some possibilities for single-row updates but I don't know how to apply it in the context of INSERT INTO ... SELECT query. CREATE OR REPLACE FUNCTION update_member_search_index() RETURNS VOID AS $$ DECLARE member_content_type_id INTEGER; BEGIN member_content_type_id := (SELECT id FROM django_content_type WHERE app_label='web' AND model='member'); DELETE FROM watson_searchentry WHERE content_type_id = member_content_type_id; INSERT INTO watson_searchentry (engine_slug, content_type_id, object_id, object_id_int, title, description, content, url, meta_encoded) SELECT 'default', member_content_type_id, web_member.id, web_member.id, web_member.name, '', web_user.email||' '||web_member.normalized_name||' '||web_country.name, '', '{}' FROM web_member INNER JOIN web_user ON (web_member.user_id = web_user.id) INNER JOIN web_country ON (web_member.country_id = web_country.id) WHERE web_user.is_active=TRUE; END; $$ LANGUAGE plpgsql; EDIT: Schemas of web_member, watson_searchentry, web_user, web_country: http://pastebin.com/3tRVPPVi. (content_type_id, object_id_int) in watson_searchentry is unique pair in the table but atm the index is not present (there is no use for it). This script should be run at most once a day for full rebuilds of search index.

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• c++ and visual studio 08, how to develop the following web extracting application. folloow up of las

  - by user287745

  the purpose is to use c++ in a useful way. i have just started programming and have made a few small applications in c and c#. my understanding is that programming for web and thing related to web is now a days a very easy task. please note this is for personnel learning not for rent a coder or any money making. an application which can run on any windows platform even win98. the application should start automatically at a scheduled time and do the following. connect to a site which displays stock prices summary (high low current open ). captures the data (excluding the other things in the site) and saves it to disk ( a sql database) please note:- internet connection is assumed to be there always. do not want to know how to make database schema or database. the stock exchange has no law prohibiting the use of the data provided on its site, but i do not want to mention the name in case i am wrong, but its for personnel private use only. the data of summary of pricing is arranged in a table such that when copied pasted to ms excel it automatically forms a table. guidance needed thank u.

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• best practices question: How to save a collection of images and a java object in a single file? File

  - by Richard

  Hi all, I am making a java program that has a collection of flash-card like objects. I store the objects in a jtree composed of defaultmutabletreenodes. Each node has a user object attached to it with has a few string/native data type parameters. However, i also want each of these objects to have an image (typical formats, jpg, png etc). I would like to be able to store all of this information, including the images and the tree data to the disk in a single file so the file can be transferred between users and the entire tree, including the images and parameters for each object, can be reconstructed. I had not approached a problem like this before so I was not sure what the best practices were. I found XLMEncoder (http://java.sun.com/j2se/1.4.2/docs/api/java/beans/XMLEncoder.html) to be a very effective way of storing my tree and the native data type information. However I couldn't figure out how to save the image data itself inside of the XML file, and I'm not sure it is possible since the data is binary (so restricted characters would be invalid). My next thought was to associate a hash string instead of an image within each user object, and then gzip together all of the images, with the hash strings as the names and the XMLencoded tree in the same compmressed file. That seemed really contrived though. Does anyone know a good approach for this type of issue? THanks! Thanks!

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