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• Which of FILE* or ifstream has better memory usage?

  - by Viet

  I need to read fixed number of bytes from files, whose sizes are around 50MB. To be more precise, read a frame from YUV 4:2:0 CIF/QCIF files (~25KB to ~100KB per frame). Not very huge number but I don't want whole file to be in the memory. I'm using C++, in such a case, which of FILE* or ifstream has better (less/minimal) memory usage? Please kindly advise. Thanks! EDIT: I read fixed number of bytes: 25KB or 100KB (depending on QCIF/CIF format). The reading is in binary mode and forward-only. No seeking needed. No writing needed, only reading. EDIT: If identifying better of them is hard, which one does not require loading the whole file into memory?

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• JQuery selector value escaping

  - by user53794

  I have a dropdown list that contains a series of options: <select id=SomeDropdown> <option value="a'b]&lt;p>">a'b]&lt;p></option> <option value="easy">easy</option> <select> Notice that the option value/text contains some nasty stuff: single quotes closing square bracket escaped html I need to remove the a'b]<p option but I'm having no luck writing the selector. Neither: $("#SomeDropdown >option[value='a''b]&lt;p>']"); or $("#SomeDropdown >option[value='a\'b]&lt;p>']"); are returning the option. What is the correct way to escape values when using the "value=" selector?

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• Forcibly clear memory in java

  - by MBennett

  I am writing an application in java that I care about being secure. After encrypting a byte array, I want to forcibly remove from memory anything potentially dangerous such as the key used. In the following snippet key is a byte[], as is data. SecretKeySpec secretKeySpec = new SecretKeySpec(key, "AES"); Cipher cipher = Cipher.getInstance("AES"); cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec); byte[] encData = cipher.doFinal(data, 0, data.length); Arrays.fill(key, (byte)0); As far as I understand, the last line above overwrites the key with 0s so that it no longer contains any dangerous data, but I can't find a way to overwrite or evict secretKeySpec or cipher similarly. Is there any way to forcibly overwrite the memory held by secretKeySpec and cipher, so that if someone were to be able to view the current memory state (say, via a cold boot attack), they would not get access to this information?

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• natural sort of text and numbers, JavaScript

  - by ptrn

  I'm looking for the easiest way to sort an array that consists of numbers and text, and a combination of these. E.g. '123asd' '19asd' '12345asd' 'asd123' 'asd12' turns into '19asd' '123asd' '12345asd' 'asd12' 'asd123' This is going to be used in combination with the solution to another question I've asked here. The sorting function in itself works, what I need is a function that can say that that '19asd' is smaller than '123asd'. I'm writing this in JavaScript. Edit: as adormitu pointed out, what I'm looking for is a function for natural sorting

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• How to implement copy protection of content in an open source application?

  - by Lococo

  I have an idea for an open source app -- the app would be free, but I would charge a small fee for data that a customer would order. For instance, let's say I'm writing a map application. I'd give the app away, make it open-source, but I would like to sell various maps to individual users. Is there a way to protect the data in such a way that makes it very difficult for someone to simply take the map they bought and distribute it to others? Is this feasible for an open source app?

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• How to include named capture groups in java regex?

  - by jrummell

  I'm new to regex in Java and I can't figure out how to include named capture groups in an expression. I'm writing a ScrewTurn Image Converter for Confluence's Universal Wiki Converter. This is what I have: String image = "\\[image(?<align>auto)?\\|\\|{UP\\(((?<namespace>\\w+)\\.)?(?<pagename>[\\w-]+)\\)}(?<filename>[\\w- ]+\\.[\\w]+)\\]"; Pattern imagePattern = Pattern.compile(image, Pattern.CASE_INSENSITIVE); It's throwing this exception in Pattern.comiple(): java.util.regex.PatternSyntaxException: Unknown look-behind group near index 19 \[image(?<align>auto)?\|\|{UP\(((?<namespace>\w+)\.)?(?<pagename>[\w-]+)\)}(?<filename>[\w- ]+\.[\w]+)\] ^ I've used named capture groups like this before in C# (?<namedgroup>asdf), but not in Java. What am I missing?

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• Opinions about Dabo

  - by driverate

  Has anyone used Dabo lately? How does it rate vs Boa Constructor, etc? I'm writing a new Python database app and Dabo looks promising, but what's the real-world scoop on it? Is it used by many developers? It's not talked about very much here on SO, or anywhere, as far as I can tell. I'm just a little concerned that the support community might be too small, or the possibility that writers might decide to throw in the towel. What is your assessment of Dabo?

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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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• C# filter results quarterly

  - by user339067

  Hello! I am writing a simple C# application that is handling bank savings. I want to be able to show the results on either, yearly, monthly or quarterly basic how can this be done? How can I loop through a set of results and only show every third post (if I am using quarterly) for example. In Python I can use range(1,31,3) but how is it done in C#? UPDATE 1 I want to loop 12 times (annually) and calculate the interest each loop but I only want to print the results every third loop (quarterly). How can I achieve this? Please help!

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• Scaling a ruby script by launching multiple processes instead of using threads.

  - by Zombies

  I want to increase the throughput of a script which does net I/O (a scraper). Instead of making it multithreaded in ruby (I use the default 1.9.1 interpreter), I want to launch multiple processes. So, is there a system for doing this to where I can track when one finishes to re-launch it again so that I have X number running at any time. ALso some will run with different command args. I was thinking of writing a bash script but it sounds like a potentially bad idea if there already exists a method for doing something like this on linux.

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• WCF interoperability with WSDL proxy and performance consideration advise.

  - by user194917

  I'm essentially writing a broker service. The requirement is that I write an API that acts as an intermediary broker between our in-house developed services and a 3rd party provided API. The intention being that my API abstract the actual communication with the 3rd party API from our internal systems. The architect on the project chose WCF as the communication framework. The problem is that 70 percent of our subscriber applications are written in .Net 2 and as such have no access to the class libraries required to implement a WCF proxy. The end result being that our proxy classes are loosely based on the code auto generated by the WSDL tool as opposed to the SvcUtil tool. My question is, although I have no issues implementing the required proxy classes using basicHttp as the actual binding and using the WSDL tool, are there any special considerations that I need to take into account in this scenario? I.E proxy optimizations and the like. Thanks in advance.

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• Group and count in Rails

  - by alamodey

  I have this bit of code and I get an empty object. @results = PollRoles.find( :all, :select => 'option_id, count(*) count', :group => 'option_id', :conditions => ["poll_id = ?", @poll.id]) Is this the correct way of writing the query? I want a collection of records that have an option id and the number of times that option id is found in the PollRoles model. EDIT: This is how I''m iterating through the results: <% @results.each do |result| %> <% @option = Option.find_by_id(result.option_id) %> <%= @option.question %> <%= result.count %> <% end %>

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• How can a language be interpreted by itself (like Rubinius)?

  - by japancheese

  I've been programming in Ruby for a while now with just the standard MRI implementation of Ruby, but I've always been curious about the other implementations I hear so much about. I was reading about Rubinius the other day, a Ruby interpreter written in Ruby. I tried looking it up in various places, but I was having a hard time figuring out exactly how something like this works. I've never had much experience in compilers or language writing but I'm really interested to figure it out. How exactly can a language be interpreted by itself? Is there a basic step in compiling that I don't understand where this makes sense? Can someone explain this to me like I'm an idiot (because that wouldn't be too far off base anyways)

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• C++ Adding 2 arrays together quickly

  - by Tom Gullen

  Hello! Given the arrays: int canvas[10][10]; int addon[10][10]; Where all the values range from 0 - 100, what is the fastest way in C++ to add those two arrays so each cell in canvas equals itself plus the corresponding cell value in addon. IE, I want to achieve something like: canvas += another; So if canvas[0][0] =3 and addon[0][0] = 2 then canvas[0][0] = 5 Speed is essential here as I am writing a very simple program to brute force a knapsack type problem and there will be tens of millions of combinations.

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• Using Lambda Statements for Event Handlers

  - by lush

  I currently have a page which is declared as follows: public partial class MyPage : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { //snip MyButton.Click += (o, i) => { //snip } } } I've only recently moved to .NET 3.5 from 1.1, so I'm used to writing event handlers outside of the Page_Load. My question is; are there any performance drawbacks or pitfalls I should watch out for when using the lambda method for this? I prefer it, as it's certainly more concise, but I do not want to sacrifice performance to use it. Thanks.

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• C# Unit Testing - Generating Mock DataContexts / LINQ -> SQL classes

  - by gav

  Hi All, I am loving the new world that is C#, I've come to a point with my toy programs where I want to start writing some unit tests. My code currently uses a database via a DatabaseDataContext object (*.dbml file), what's the best way to create a mock for this object? Given how easy it is to generate the database LINQ - SQL code and how common a request this must be I'm hoping that VS2010 has built in functionality to help with testing. If I'm way off and this must be done manually could you please enlighten me as to your preferred approach? Many Thanks, Gavin

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• Can one class generate a signal and handled by another class?

  - by rashid

  Hello, I have a buffer in class 'bufferClass' that will generate a signal to tell 'fileClass' that buffer is full and now write data to file? And when 'fileClass' is done writing to file, it will generate a signal to tell 'guiClass' that data can be read from file. Is this possible? I have been reading http://www.gnu.org/s/libc/manual/html_node/Signal-Handling.html but not too sure how to generate such a signal? I don't need the exact code, just an idea. Much appreciated. i am using mac os X, x-code.

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• Generate MySQL data dump in SQL from PHP

  - by Álvaro G. Vicario

  I'm writing a PHP script to generate SQL dumps from my database for version control purposes. It already dumps the data structure by means of running the appropriate SHOW CREATE .... query. Now I want to dump data itself but I'm unsure about the best method. My requirements are: I need a record per row Rows must be sorted by primary key SQL must be valid and exact no matter the data type (integers, strings, binary data...) Dumps should be identical when data has not changed I can detect and run mysqldump as external command but that adds an extra system requirement and I need to parse the output in order to remove headers and footers with dump information I don't need (such as server version or dump date). I'd love to keep my script as simple as I can so it can be hold in an standalone file. What are my alternatives?

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• Strange pattern matching with functions instancing Show

  - by Sean D

  So I'm writing a program which returns a procedure for some given arithmetic problem, so I wanted to instance a couple of functions to Show so that I can print the same expression I evaluate when I test. The trouble is that the given code matches (-) to the first line when it should fall to the second. {-# OPTIONS_GHC -XFlexibleInstances #-} instance Show (t -> t-> t) where show (+) = "plus" show (-) = "minus" main = print [(+),(-)] returns [plus,plus] Am I just committing a motal sin printing functions in the first place or is there some way I can get it to match properly? edit:I realise I am getting the following warning: Warning: Pattern match(es) are overlapped In the definition of `show': show - = ... I still don't know why it overlaps, or how to stop it.

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• (C++) What's the difference between these overloaded operator functions?

  - by cv3000

  What is the difference between these two ways of overloading the != operator below. Which is consider better? Class Test { ...// private: int iTest public: BOOL operator==(const &Test test) const; BOOL operator!=(const &Test test) const; } BOOL operator==(const &Test test) const { return (iTest == test.iTest); } //overload function 1 BOOL Test::operator!=(const &Test test) const { return !operator==(test); } //overload function 2 BOOL Test::operator!=(const &Test test) const { return (iTest != test.iTest); } I've just recently seen function 1's syntax for calling a sibling operator function and wonder if writing it that way provides any benefits.

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• How do I assign a value from params, or session, whichever exists?

  - by irkenInvader

  What is the "Rails-way" or the "Ruby-way" of doing the following: In my controller, I'm creating and instance of an Options class. It will be initialized with information in the params hash if the params hash exists. Otherwise, it will check the sessions hash for the information. Finally, it will initialize with defaults if neither params nor session has the data it needs. Here is how I'm doing it now (it works fine, but it seems a little ugly): if params[:cust_options] @options = CustomOptions.new( params[:cust_options] ) else if session[:cust_options @options = CustomOptions.new( session[:cust_options] ) else @options = CustomOptions.new end end session[:cust_options] = @options.to_hash Like I said, everything is working fine, I'm just looking for a more idiomatically Ruby way of writing this block of code.

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• I need HTML help. I am using the FRAMESET tag and its getting complicated.

  - by Jordan

  You will need to download a 4Shared file so that I can give you all the information necessary. Problem: I am using the FRAMESET tab and I have links put in the left hand column and when clicked, they only open in that column when I want them to open up the full screen, not with a new tab though. Here is where you can get a word file with all the writing that I put in notepad for my pages. Each Word page is a different Notepad file, and there are pictures on the bottom to help understand. www.4shared.com/get/299858562/2f5cf7dd/2_HTML_help.html THANK YOU!

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• Reusing an anonymous parameter in a prepared statement

  - by Chris Lieb

  I am customizing the insert SQL generated by hibernate and have hit an issue. When Hibernate generates the query by itself, it inserts data into the first two columns of the table, but this causes a database error since all four columns of the table are non-nullable. For the insert to be performed properly, it must insert the same data into two columns of the new record. This means that I need Hibernate to bind the same data to two different parameters in the query (prepared statement) that I am writing. Is there some SQL syntax that allows me to refer to anonymous parameters bound to a prepared statement in an order different from which they are bound? Details REF_USER_PAGE_XREF ---------------------------------------- PK FK1 | NETWORK_ID | VARCHAR2(100) PK FK1 | PAGE_PATH | VARCHAR2(1000) | USER_LAST_UPDT | VARCHAR2(100) | TMSP_LAST_UPDT | DATE insert into REF_USER_ROLE_XREF( NETWORK_ID, PAGE_PATH, TMSP_LAST_UPDT, USER_LAST_UPDT) values ( ?, /* want to insert the same data here */ ?, ?, /* and here */ (select to_char(sysdate, 'DD-MON-YY') from dual) I want to insert the same data into the first and third anonymous parameters.

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• Native arrays and computing hashvalues (VB, C#)

  - by Jeffrey Kern

  I feel bad asking this question but I am currently not able to program and test this as I'm writing this on my cell-phone and not on my dev machine :P (Easy rep points if someone answers! XD ) Anyway, I've had experience with using hashvalues from String objects. E.g., if I have StringA and StringB both equal to "foo", they'll both compute out the same hashvalue, because they're set to equal values. Now what if I have a List, with T being a native data type. If I tried to compute the hashvalue of ListA and ListB, assuming that they'd both be the same size and contain the same information, wouldn't they have equal hashvalues as well?

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• WPF> Using RadioButtonList style. I want to display user friendly enum strings. how?

  - by Saghar

  Hi WPF lovers, I want to display all the possible enum values as Radio buttons. I am using popular RadioButtonList style to display the radiobutton from my enum using DataProvider in a Listcontrol. I can get all the radio buttons but the text appear with the radio button is not user friendly. I am using the following method. http://social.msdn.microsoft.com/forums/en-US/wpf/thread/5137aabc-bb3a-478a-9438-bc93dd9cc0ac/ I want to show "A ball" instead of "a" and "B ball" instead of "b" I thought about using converter. But where to use convert. Or any other way to display user friendly values? As this style is very common, thats why I am not writing whole code. If anything not clear, please ask. I have already invested about 5 hours on this problem.

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