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• Performing regex on a stream

  - by takoi

  I have some large text files which im going to preform consecutive matching on (just capturing, not replacing). Im thinking its not such a good idea to keep the whole file in memory, but rather use a Reader. What i know about the input is that if there's a match, its not going to span more than 5 lines. So my idea was to have some sort of buffer which just keeps these 5 lines, or so, do the first search, and continue. But it has to "know" where the regex match ended for this to work. e.g if the match ends at line 2 it should start the next search from here. Is it possible to do something like this in an efficient way?

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• small string optimization for vector?

  - by BuschnicK

  I know several (all?) STL implementations implement a "small string" optimization where instead of storing the usual 3 pointers for begin, end and capacity a string will store the actual character data in the memory used for the pointers if sizeof(characters) <= sizeof(pointers). I am in a situation where I have lots of small vectors with an element size <= sizeof(pointer). I cannot use fixed size arrays, since the vectors need to be able to resize dynamically and may potentially grow quite large. However, the median (not mean) size of the vectors will only be 4-12 bytes. So a "small string" optimization adapted to vectors would be quite useful to me. Does such a thing exist? I'm thinking about rolling my own by simply brute force converting a vector to a string, i.e. providing a vector interface to a string. Good idea?

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• Bitmap.Save problems

  - by user284026

  Hello, can anyone tell me if you know to be a problem with Bitmap and steganography for WM 6? I am working on a project and i have to hide a digital signature in a bitmap. The algorithm works perfect, as in untill i have the image on the memory the bitmap contains the modified bytes. But after i save the image (Bitmap.Save()) and I reopen the image, than those bytes are lost. When i say lost i mean they are the orriginal bytes from when the picture was taken. Thank you.

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• Reading a memorystream

  - by user1842828

  Using several examples here on StackOverflow I thought the following code would decompress a gzip file then read the memory-stream and write it's content to the console. No errors occur but I get no output. public static void Decompress(FileInfo fileToDecompress) { using (FileStream originalFileStream = fileToDecompress.OpenRead()) { string currentFileName = fileToDecompress.FullName; string newFileName = currentFileName.Remove(currentFileName.Length - fileToDecompress.Extension.Length); using (FileStream decompressedFileStream = File.Create(newFileName)) { using (GZipStream decompressionStream = new GZipStream(originalFileStream, CompressionMode.Decompress)) { MemoryStream memStream = new MemoryStream(); memStream.SetLength(decompressedFileStream.Length); decompressedFileStream.Read(memStream.GetBuffer(), 0, (int)decompressedFileStream.Length); memStream.Position = 0; var sr = new StreamReader(memStream); var myStr = sr.ReadToEnd(); Console.WriteLine("Stream Output: " + myStr); } } } }

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• reading specific lines from a file

  - by MacUsers

  What's the best way of reading only the specific lines (based on matching text) from a file? This is what I'm doing now: match_txt = "lhcb" for inFile in os.listdir('.'): readFile = open(inFile, 'r') lines = readFile.readlines() readFile.close() for line in lines: if line.find(match_txt)==0: #< do stuff here > i.e. I'm reading the lines, only with "lhcb" in it, from all the files in the present directory one by one. Is it the best way of doing that? Can it be done without loading the whole file in the memory in the first place?

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• How do I write a Java text file viewer for big log files

  - by Hannes de Jager

  I am working on a software product with an integrated log file viewer. Problem is, its slow and unstable for really large files because it reads the whole file into memory when you view a log file. I'm wanting to write a new log file viewer that addresses this problem. What are the best practices for writing viewers for large text files? How does editors like notepad++ and VIM acomplish this? I was thinking of using a buffered Bi-directional text stream reader together with Java's TableModel. Am I thinking along the right lines and are such stream implementations available for Java?

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• How can I disable Java garbage collector ?

  - by Nelson

  Hi, we have a PHP webapp that calls a java binary to produce a pdf report (with jasperreport), the java binary outpus pdf to standart output and exits, the php then send the pdf to browser. This java command lasts about 3 to 6 seconds, I think when it lasts 6 second it's because the GC kicks in, so I would like to disable it because anyway when the command exits all memory is returned.. I would like to know how to disable it for Java 1.4.2 and for Java 1.6.0 because we are currently testing both JVM to see which performs faster.. Thanks

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• delete & new in c++

  - by singh

  Hi This may be very simple question,But please help me. i wanted to know what exactly happens when i call new & delete , For example in below code char * ptr=new char [10]; delete [] ptr; call to new returns me memory address. Does it allocate exact 10 bytes on heap, Where information about size is stored.When i call delete on same pointer,i see in debugger that there are a lot of byte get changed before and after the 10 Bytes. Is there any header for each new which contain information about number of byte allocated by new. Thanks a lot

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• C++'s unordered_map / hash_map / Google's dense_hash - how to input binary data (buf+len) and insert

  - by shlomif

  Hi all, I have two questions about Google's dense_hash_map, which can be used instead of the more standard unordered_map or hash_map: How do I use an arbitrary binary data memory segment as a key: I want a buffer+length pair, which may still contain some NUL (\0) characters. I can see how I use a NUL-terminated char * string , but that's not what I want. How do I implement an operation where I look if a key exists, and if not - insert it and if it does return the pointer to the existing key and let me know what actually happened. I'd appreciate it if anyone can shed any light on this subject. Regards, -- Shlomi Fish

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• How can one use multi threading in php applications

  - by Steve Obbayi

  Is there a realistic way of implementing a multi-threaded model in php whether truly or just simulating it. Some time back it was suggested that you can force the operating system to load another instance of the php executable and handle other simultaneous processes. The problem with this is that when the php code finished executing the php instance remains in memory because there is no way to kill it from within php. so if you are simulating several threads you can imagine whats going to happen. So am still looking for a way multi-threading can be done or simulated effectively from within php. Any ideas?

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• Problems opening large csv file

  - by John Tyler

  I have a csv file that is 100mb in size. I need to parse some data out of it into a new format. I tried PHP, but keep running into memory issues. After around the first 150 "rows" or so, the script poops out. This is even on the localhost, and doing everything I can to tune the PHP settings, including max_memory and script_execution_time. Now before I continue, I'd like to know if Python will poop out on me too. Or if I will have to use C++. Can someone name good csv libraries for for these programmin langueage? The file is quoted csv. I mean scheiza I can't even open this text file in OpenOffice without it dying on me. (then again, Java sux as bad as PHP)

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• How do I bind a key to "the function represented by the following key sequence"?

  - by katrielalex

  I'm just starting to learn emacs (woohoo!) and I've been mucking around in my .emacs quite happily. Unfortunately, I don't know Lisp yet, so I'm having issues with the basics. I've already remapped a few keys until I fix my muscle memory: (global-set-key (kbd "<f9>") 'recompile) That's fine. But how can I tell a key to 'simulate pressing several keys'? For instance, I don't know, make <f1> do the same as C-u 2 C-x } (widen buffer by two chars). One way is to look up that C-x } calls shrink-window-horizontally, and do some sort of lambda thing. This is of course the neat and elegant way (how do you do this?). But surely there's a way to define <f1> to send the keystrokes C-u 2 C-x }?

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• Is a full list returned first and then filtered when using linq to sql to filter data from a databas

  - by RJ

  This is probably a very simple question that I am working through in an MVC project. Here's an example of what I am talking about. I have an rdml file linked to a database with a table called Users that has 500,000 rows. But I only want to find the Users who were entered on 5/7/2010. So let's say I do this in my UserRepository: from u in db.GetUsers() where u.CreatedDate = "5/7/2010" select u (doing this from memory so don't kill me if my syntax is a little off, it's the concept I am looking for) Does this statement first return all 500,000 rows and then filter it or does it only bring back the filtered list?

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• Firefox: how to apply XSLT from plugin to opened XML document? (how to replace document with another

  - by aloispaulin

  Hi! I've developed a plug-in for Firefox, that can read and manipulate the content of the currently opened document. I would like to apply a XLST to the document in case it is XML. I have no problem to read the XML document and apply a XSLT to it in memory, however, I have no idea of how to replace the existing document with the newly created one. Thus, I see two possible scenarios: a) I replace the document with the result of the transformation b) I apply the XSLT directly to the XML All my attempts to realize one of both possible solutions have failed... Hoping the community can provide help! Many tnx in advance! Alois

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• How do stream rows from a MSSQL table into a .NET app, in 10000 row chunks?

  - by Gravitas

  I have a table with 300 million rows in Microsoft SQL Server 2008 R2. There is a clustered index on the date column [DataDate] which means that the entire table is ordered by the date column. How do I stream out the data from this table, into my .NET application, in 10000 row chunks? Environment: Using C#. Have to be able to pause the data stream at any point, to allow the client to process the rows. Unfortunately, cannot use a select * from as this will select the entire table (its 50GB - it won't fit into memory).

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• Is it a good idea to define a variable in a local block for a case of a switch statement?

  - by Paperflyer

  I have a rather long switch-case statement. Some of the cases are really short and trivial. A few are longer and need some variables that are never used anywhere else, like this: switch (action) { case kSimpleAction: // Do something simple break; case kComplexAction: { int specialVariable = 5; // Do something complex with specialVariable } break; } The alternative would be to declare that variable before going into the switch like this: int specialVariable = 5; switch (action) { case kSimpleAction: // Do something simple break; case kComplexAction: // Do something complex with specialVariable break; } This can get rather confusing since it is not clear to which case the variable belongs and it uses some unnecessary memory. However, I have never seen this usage anywhere else. Do you think it is a good idea to declare variables locally in a block for a single case?

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• Is it a good practice to create a reference to application context and use it anywhere?

  - by kknight

  I have to use context in many places of my code such as database operations, preference operations, etc. I don't want to pass in context for every method. Is it a good practice to create a reference to application context at the main Activity and use it anywhere such as database operations? So, I don't need some many context in method parameters, and the code can avoid position memory leak due to use of Activity Context. public class MainActivity extends Activity { public static Context s_appContext; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); s_appContext = this.getApplicationContext();

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• UITableView with contact image problems.

  - by prathumca

  As par my app requirement, I'm showing the contact images in a UITableView as shown below. ABRecordRef contact = [self getContact]; if(contact && ABPersonHasImageData(contact)) { UIImage *contactImage = [UIImage imageWithData:(NSData*)ABPersonCopyImageData(contact)]; callImage.image = contactImage; } I've two problems if I use the above code segment. Table Scrolling is too slow. If comment the above code, then UITable responds very fast. Memory Management. My app started using 25 - 30 MB of RAM. Is there any better way to avoid the above two problems?

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• Image gets slightly erased on SWT/Windows

  - by zvikico

  I have an Eclipse plugin which includes a view. The view has several icons in the toolbar. I'm experiencing a very strange problem: on Windows, in some occasions (after prolonged use), one of the icons gets slightly erased. This does not happen on other platforms. This looks like a memory leak or some other resource misuse, but I just can't figure out where. The rest of the icons, which are initialized and used in the exact same manner are not affected. I tried working with Sleak, but I really don't see anything out of the ordinary. Any help would be appreciated.

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• Is there a way to cause a new C++ class instance to fail, if certain conditions in the contructor ar

  - by Jim Fell

  As I understand it, when a new class is instantiated in C++, a pointer to the new class is returned, or NULL, if there is insufficient memory. I am writing a class that initializes a linked list in the constructor. If there is an error while initializing the list, I would like the class instantiator to return NULL. For example: MyClass * pRags = new MyClass; If the linked list in the MyClass constructor fails to initialize properly, I would like pRags to equal NULL. I know that I can use flags and additional checks to do this, but I would like to avoid that, if possible. Does anyone know of a way to do this? Thanks.

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• Is there any conflict between NFS and calling getFD().sync()?

  - by Dr.Dredel

  My boss is worried that our NFS file system will not be happy with the jboss run java process calling getFD().sync on the files we are writing. We have noticed that frequently the time stamp on the created file is minutes (sometimes as many as 15 minutes) after the log claims the file was finished writing. My only guess is that the NFS is hanging on to the file in memory and not writing it till it feels like it. sync should solve that probelm, right? I also noticed that there is never a close() called on the file. Wondering if that could have been the cause as well? any thoughts appreciated.

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• Windows equivalent of inb(), outb(), low level i/o

  - by Sebastian Dwornik

  I have some Linux code that monitors our hardware by collecting temperatures, voltages, and fan speeds, from the motherboard using inb(), outb(), inl(), etc. low level i/o functions. My challenge is to port that code over to run under Windows as a simple console app. But am puzzled in what functions Win32 (or .NET) provide that allow me permission to access direct memory mapped ports. I don't want to code a system driver either. My Windows tool preference is VS2008. (fyi) Is this possible?

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• What is the correct way of handling a reloaded view after it was dismissed?

  - by favo

  Hi, I have the same problem as the guy here: http://stackoverflow.com/questions/2682844/uiimagepickercontroller-reloads-view-after-its-dismissed I have a UIView with a UIDatePicker within a Popover. When the Popover is dismissed and presented again, it sometimes resets the Picker in the view because hidden views are unloaded when a memory warning occurs. This is the part displaying the view: endCompareDateTimePicker.picker.maximumDate = [NSDate dateWithTimeIntervalSinceNow:0]; [endCompareDateTimePopover presentPopoverFromRect:sender.frame inView:self.view permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES]; The picker (IBOutlet UIDatePicker) does not stay initiated. Adding a [endCompareDateTimePicker loadView] helped out and got me the picker initiated to set the correct date values before displaying the view. While this is working, I dont think this is the proper way doing this. What would be the correct way to handle this situation?

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• iPhone xcode array losing state after load

  - by Frames84

  Right i've had a search around and can't find anything. @synthesize list; // this is an NSArry -(void) viewDidLoad { NSArray *arr = [self getJSONFeed]; self.List = [arr retain]; // if i copy the access code into here it works fine. } -(void) tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { NSUInteger row = [indexPath row]; NSArray *vals = [list objectAtIndex:row] retain]; NSString *id = [vals valueForKey:@"id"]; // ERROR } right i've taken some of the code to try and provide it as simple as possible, ignore typo's and memory leaks this is sorted. Basically when I select a row I can't get data out of my 'list' array object. Please can anyone help me out?

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• what mysql table structure is better

  - by Sergey

  I have very complicated search algorithm on my site, so i decided to make a table with cache or maybe all possible results. I wanna ask what structure would be better, or maybe not the one of them? (mySQL) 1) word VARCHAR, results TEXT or BLOB where i'll store ids of found objects (for example 6 chars for each id) 2) word VARCHAR, result INT, but words are not unique now i think i'll have about 200 000 rows in 1) with 1000-10000 ids each row or 200 000 000+ rows in 2) First way takes more storage memory but i think it would be much faster to find 1 unique row among 200 000, than 1000 rows among 200 mln non unique rows i think about index on word column and no sphinx. So that do YOU think? p.s. as always, sorry for my english if it's not very good.

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