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• Are there Windows API binaries for Subversion or do I have to build SVN to call the API from Windows

  - by JeffH

  I want to call a Subversion API from a Visual Studio 2003 C++ project. I know there are threads here, here, here, and here that tell how to get started with C#.NET on Windows (the consensus seems to be SharpSvn, which I've used easily and successfully on another project) but that's not what I want. I've read the chapter on using APIs in the red-bean book which says: Subversion is primarily a set of C libraries, with header (.h) files that live in the subversion/include directory of the source tree. These headers are copied into your system locations (e.g., /usr/local/include) when you build and install Subversion itself from source. These headers represent the entirety of the functions and types meant to be accessible by users of the Subversion libraries. I'd like to use CollabNet Subversion but there doesn't seem to be API binary downloads, and I'd just as soon not build the whole thing if I can avoid it. Considering another approach, I found RapidSVN's C++ API, but it doesn't appear to offer Windows API binaries either and seems to require building SVN (which I would be willing to do as a last choice if RapidSVN's API is higher-level than the stock SVN offering.) Does calling the API from C++ in Windows have to be this much more work compared to using SharpSvn under .NET, or is there something I haven't found that would help me achieve my goal?

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• Imlpementations of an Interface with Different Types?

  - by b3njamin

  Searched as best I could but unfortunately I've learned nothing relevant; basically I'm trying to work around the following problem in C#... For example, I have three possible references (refA, refB, refC) and I need to load the correct one depending on a configuration option. So far however I can't see a way of doing it that doesn't require me to use the name of said referenced object all through the code (the referenced objects are provided, I can't change them). Hope the following code makes more sense: public ??? LoadedClass; public Init() { /* load the object, according to which version we need... */ if (Config.Version == "refA") { Namespace.refA LoadedClass = new refA(); } else if (Config.Version == "refB") { Namespace.refB LoadedClass = new refB(); } else if (Config.Version == "refC") { Namespace.refC LoadedClass = new refC(); } Run(); } private void Run(){ { LoadedClass.SomeProperty... LoadedClass.SomeMethod(){ etc... } } As you can see, I need the Loaded class to be public, so in my limited way I'm trying to change the type 'dynamically' as I load in which real class I want. Each of refA, refB and refC will implement the same properties and methods but with different names. Again, this is what I'm working with, not by my design. All that said, I tried to get my head around Interfaces (which sound like they're what I'm after) but I'm looking at them and seeing strict types - which makes sense to me, even if it's not useful to me. Any and all ideas and opinions are welcome and I'll clarify anything if necessary. Excuse any silly mistakes I've made in the terminology, I'm learning all this for the first time. I'm really enjoying working with an OOP language so far though - coming from PHP this stuff is blowing my mind :-)

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• Best Practice: Protecting Personally Identifiable Data in a ASP.NET / SQL Server 2008 Environment

  - by William

  Thanks to a SQL injection vulnerability found last week, some of my recommendations are being investigated at work. We recently re-did an application which stores personally identifiable information whose disclosure could lead to identity theft. While we read some of the data on a regular basis, the restricted data we only need a couple of times a year and then only two employees need it. I've read up on SQL Server 2008's encryption function, but I'm not convinced that's the route I want to go. My problem ultimately boils down to the fact that we're either using symmetric keys or assymetric keys encrypted by a symmetric key. Thus it seems like a SQL injection attack could lead to a data leak. I realize permissions should prevent that, permissions should also prevent the leaking in the first place. It seems to me the better method would be to asymmetrically encrypt the data in the web application. Then store the private key offline and have a fat client that they can run the few times a year they need to access the restricted data so the data could be decrypted on the client. This way, if the server get compromised, we don't leak old data although depending on what they do we may leak future data. I think the big disadvantage is this would require re-writing the web application and creating a new fat application (to pull the restricted data). Due to the recent problem, I can probably get the time allocated, so now would be the proper time to make the recommendation. Do you have a better suggestion? Which method would you recommend? More importantly why?

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• Proper API Design for Version Independence?

  - by Justavian

  I've inherited an enormous .NET solution of about 200 projects. There are now some developers who wish to start adding their own components into our application, which will require that we begin exposing functionality via an API. The major problem with that, of course, is that the solution we've got on our hands contains such a spider web of dependencies that we have to be careful to avoid sabotaging the API every time there's a minor change somewhere in the app. We'd also like to be able to incrementally expose new functionality without destroying any previous third party apps. I have a way to solve this problem, but i'm not sure it's the ideal way - i was looking for other ideas. My plan would be to essentially have three dlls. APIServer_1_0.dll - this would be the dll with all of the dependencies. APIClient_1_0.dll - this would be the dll our developers would actual refer to. No references to any of the mess in our solution. APISupport_1_0.dll - this would contain the interfaces which would allow the client piece to dynamically load the "server" component and perform whatever functions are required. Both of the above dlls would depend upon this. It would be the only dll that the "client" piece refers to. I initially arrived at this design, because the way in which we do inter process communication between windows services is sort of similar (except that the client talks to the server via named pipes, rather than dynamically loading dlls). While i'm fairly certain i can make this work, i'm curious to know if there are better ways to accomplish the same task.

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• What's the best Linux backup solution?

  - by Jon Bright

  We have a four Linux boxes (all running Debian or Ubuntu) on our office network. None of these boxes are especially critical and they're all using RAID. To date, I've therefore been doing backups of the boxes by having a cron job upload tarballs containing the contents of /etc, MySQL dumps and other such changing, non-packaged data to a box at our geographically separate hosting centre. I've realised, however that the tarballs are sufficient to rebuild from, but it's certainly not a painless process to do so (I recently tried this out as part of a hardware upgrade of one of the boxes) long-term, the process isn't sustainable. Each of the boxes is currently producing a tarball of a couple of hundred MB each day, 99% of which is the same as the previous day partly due to the size issue, the backup process requires more manual intervention than I want (to find whatever 5GB file is inflating the size of the tarball and kill it) again due to the size issue, I'm leaving stuff out which it would be nice to include - the contents of users' home directories, for example. There's almost nothing of value there that isn't in source control (and these aren't our main dev boxes), but it would be nice to keep them anyway. there must be a better way So, my question is, how should I be doing this properly? The requirements are: needs to be an offsite backup (one of the main things I'm doing here is protecting against fire/whatever) should require as little manual intervention as possible (I'm lazy, and box-herding isn't my main job) should continue to scale with a couple more boxes, slightly more data, etc. preferably free/open source (cost isn't the issue, but especially for backups, openness seems like a good thing) an option to produce some kind of DVD/Blu-Ray/whatever backup from time to time wouldn't be bad My first thought was that this kind of incremental backup was what tar was created for - create a tar file once each month, add incrementally to it. rsync results to remote box. But others probably have better suggestions.

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• Screenscraping and reverse engineering health based web tool

  - by ArbInv

  Hi There is a publicly available free tool which has been built to help people understand the impact of various risk factors on their health / life expectancy. I am interested in understanding the data that sits behind the tool. To get this out it would require putting in a range of different socio-demographic factors and analyzing the resulting outputs. This would need to be done across many thousand different individual profiles. The tool was probably built on some standard BI platorm. I have no interest in how the tool was built but do want to get to the data within it. The site has a Terms of Use Agreement which includes: Not copying, distribute, adapt, create derivative works of, translate, or otherwise modify the said tool Not decompile, disassemble, reverse assemble, or otherwise reverse engineer the tool. The said institution retains all rights, title and interest in and to the Tool, and any and all modifications thereof, including all copyright, copyright registrations, trade secrets, trademarks, goodwill and confidential and proprietary information related thereto. Would i be in effect breaking the law if i were to point a screen scraping tool which downloaded the data that sits behind the tool in question?? Any advice welcomed? THANKS

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• Help dealing with data dependency between two registration forms

  - by franko75

  I have a tricky issue here with a registration of both a user and his/her pet. Both the user and the pet are treated as separate entities and both require separate registration forms. However, the user's pet has to be linked to the user via a foreign key in the database. The process is basically that when a new user joins the site, firstly they register their pet, then they register themselves. The reason for this order is to check their pet's eligibility for the site (there are some criteria to be met) first, instead of getting the user to sign up only to then find out their pet is ineligible. It is this ordering of the form submissions which is causing me a bit of a headache, as follows... The site is being developed with an MVC framework, and the User registration process is managed via a method in a User_form controller, while the pet registration process is managed via a method in the Pet_form controller. The pet registration form happens first, and the pet data can be saved without the owner_id at this stage, with the user id possibly being added (e.g by retrieving pet's id from session) following user registration. However, doing it this way could potentially result in redundant data, where pet records would be created in the database, but if the user doesn't actually register themselves too, then the pets will be ownerless records in the DB. Other option is to serialize the new pet's data at the pet registration stage, don't save it to the DB until the user fills out their registration form. Once the user is created, i can pass serialised data AND the owner_id to a method in the Pet Model which can update the DB. However, I also need to set the newly created $pet to $this-pet which I then access for a sequence of other related forms. Should I just set the session variable in the model method? Then in the Pet controller constructor, do a check for pet stored in session, if yes, assign to $this-pet... If this makes any sense to anybody and you have some advice, i'd be grateful to hear it!

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• Simple JPG/HTML Not Showing Up in iPhone

  - by Jascha

  I'm not familiar with iPhones wants and needs, nor do I have one, but a client wants a screen cap of his site to show up when an iPhone user comes around so I created an .htaccess redirect to an iPhone specific page with this bit of code... RewriteEngine on RewriteCond %{HTTP_USER_AGENT} iPhone RewriteCond %{REQUEST_URI} !^/iPhone/ RewriteRule .* /iPhone/ [R] And the html of the iPhone page... <html> <head> <title>Eatamadedia</title> </head> <body style="background-color:#858384;margin:0 auto;"> <img src="../images/iPhonePage.jpg"> </body> </html> The page redirects just fine, but the .jpg doesn't show up. I can't imagine a simpler page. Anyone know what could be preventing the image from displaying? Does the iPhone require headers? The site in question is http://eatamedida.com Thank you in advance for your input. -J

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• Dictionaries with more than one key per value in Python

  - by nickname

  I am attempting to create a nice interface to access a data set where each value has several possible keys. For example, suppose that I have both a number and a name for each value in the data set. I want to be able to access each value using either the number OR the name. I have considered several possible implementations: Using two separate dictionaries, one for the data values organized by number, and one for the data values organized by name. Simply assigning two keys to the same value in a dictionary. Creating dictionaries mapping each name to the corresponding number, and vice versa Attempting to create a hash function that maps each name to a number, etc. (related to the above) Creating an object to encapsulate all three pieces of data, then using one key to map dictionary keys to the objects and simply searching the dictionary to map the other key to the object. None of these seem ideal. The first seems ugly and unmaintainable. The second also seems fragile. The third/fourth seem plausible, but seem to require either much manual specification or an overly complex implementation. Finally, the fifth loses constant-time performance for one of the lookups. In C/C++, I believe that I would use pointers to reference the same piece of data from different keys. I know that the problem is rather similar to a database lookup problem by a non-key column, however, I would like (if possible), to maintain the approximate O(1) performance of Python dictionaries. What is the most Pythonic way to achieve this data structure?

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• 2D Histogram in R: Converting from Count to Frequency within a Column

  - by Jac

  Would appreciate help with generating a 2D histogram of frequencies, where frequencies are calculated within a column. My main issue: converting from counts to column based frequency. Here's my starting code: # expected packages library(ggplot2) library(plyr) # generate example data corresponding to expected data input x_data = sample(101:200,10000, replace = TRUE) y_data = sample(1:100,10000, replace = TRUE) my_set = data.frame(x_data,y_data) # define x and y interval cut points x_seq = seq(100,200,10) y_seq = seq(0,100,10) # label samples as belonging within x and y intervals my_set$x_interval = cut(my_set$x_data,x_seq) my_set$y_interval = cut(my_set$y_data,y_seq) # determine count for each x,y block xy_df = ddply(my_set, c("x_interval","y_interval"),"nrow") # still need to convert for use with dplyr # convert from count to frequency based on formula: freq = count/sum(count in given x interval) ################ TRYING TO FIGURE OUT ################# # plot results fig_count <- ggplot(xy_df, aes(x = x_interval, y = y_interval)) + geom_tile(aes(fill = nrow)) # count fig_freq <- ggplot(xy_df, aes(x = x_interval, y = y_interval)) + geom_tile(aes(fill = freq)) # frequency I would appreciate any help in how to calculate the frequency within a column. Thanks! jac EDIT: I think the solution will require the following steps 1) Calculate and store overall counts for each x-interval factor 2) Divide the individual bin count by its corresponding x-interval factor count to obtain frequency. Not sure how to carry this out though. .

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• so i got an econ degree...computing science or software systems (software engineering) degree ?

  - by sofreakinghigh

  okay so here's the story. i want to work in developing software (not QA or writing tests), so although I am currently starting computing science this summer, i came across Software Systems (aka s.e.) program which is "applied" but under computing science.... so what is the difference between the 2 disciplines ? if i choose software engineering, would it require more in depth expertise with calculus (i fail at it), and more coding time ? i am looking for a way to write better and more efficient code. I want to go to school, so i wont get lazy. i want to pick a program that would directly aid me in writing and developing software. graduating with an Econ degree in last year doesn't really help in landing jobs requiring comp sci/software engineering degrees....i should've studied harder in Economics (and maybe land a job) but i was obsessed with learning how to program with various languages since day 1 at University, but i didn't think i was smart enough to pass comp sci courses (so i just relied on books + irc...) and my parents said software jobs are being outsourced to India so i thought this obsession was just a "phase" and i should keep it as a hobby. but yes, it's quite funny why i hadn't pursued this field much earlier. as Joelonsoftware.com says economics degree starts with a bang (microeconomics the only course you only need really)....predicting stock prices (ridiculous!) + realizing China's potential power to meltdown US economy and vice versa + interest rate is inversely related to bond premium which is inversely related to stock market it would absolutely awesome if there was a program that combined finance + programming.

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• Hopping from a C++ to a Perl Unix profile?

  - by rocknroll

  Hi all, I have been a C++,Linux Developer till now and I am adept in this stack. Off late I have been getting opportunities that require Perl,Unix (with knowledge of C++,shell scripting) expertise. Organisations are showing interest even thought I don't have much scripting experience to boast off. The roll is more in a Support,maintenance project involving SQL as well. Off late I am in a fix whether to forgo these offers or not. I don't know the dynamics of an IT organisation and thus on one hand I fear that my C++ experience will be nullified and on the positive side I am getting to work on a new technology stack which will only add to my skill set. I am sure, most of you at some point of time have encountered such dilemmas and would have taken some decision. I want you to share your perspectives on such a scenario where a person is required to change his/her technology stack when changing his/her job. What are the merits and demerits in going with either of the choices? Also I know that C++ isn't going anywhere in the near future. What about perl? I have no clue as to what the future holds for perl developer? Whether there are enough opportunities for a perl developer? I am asking this question here because most of my fellow programmers face this career choice dilemma. Thanks.

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• Define "Validation in the Model"

  - by sunwukung

  There have been a couple of discussions regarding the location of user input validation: http://stackoverflow.com/questions/659950/should-validation-be-done-in-form-objects-or-the-model http://stackoverflow.com/questions/134388/where-do-you-do-your-validation-model-controller-or-view These discussions were quite old, so I wanted to ask the question again to see if anyone had any fresh input. If not, I apologise in advance. If you come from the Validation in the Model camp - does Model mean OOP representation of data (i.e. Active Record/Data Mapper) as "Entity" (to borrow the DDD terminology) - in which case you would, I assume, want all Model classes to inherit common validation constraints. Or can these rules simply be part of a Service in the Model - i.e. a Validation service? For example, could you consider Zend_Form and it's validation classes part of the Model? The concept of a Domain Model does not appear to be limited to Entities, and so validation may not necessarily need to be confined to this Entities. It seems that you would require a lot of potentially superfluous handing of values and responses back and forth between forms and "Entities" - and in some instances you may not persist the data recieved from user input, or recieve it from user input at all.

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• Can I create an application using SlimDX relying on the DirectX DLLs already bundled with Vista/Win7

  - by norheim.se

  I'm working on a .NET application that requires the use of accelerated graphics, currently DirectX 9.0c. The software is quite graphics intensive and must, in addition, be launchable from a CD or by ClickOnce without the user requiring administrator's permissions. I currently use SlimDX, which works great featurewise, but the users are getting rather annoyed by having to install the DirectX redistributable. Especially since this does require elevated permissions. It is rather hard to explain to them why the version of DirectX already bundled with their OS is not sufficient. After all - DirectX 9.0c has been around since 2004, and I'm not using any new fancy features. The ability to deliver an application that "just works" in Vista or Windows 7, without any particular additional prerequisites would be a huge advantage. Therefore: Is there any way I can build an application using DirectX 9.0c based on SlimDX, that relies only on the libraries provided in the standard Windows Vista/Win7 installation? That is - without requiring the additional DirectX redistributable to be installed? If not - is there any other managed (and preferably not abandoned) DirectX wrapper that can serve this purpose? Thanks in advance!

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• How can I make VS2010 insert using statements in the order dictated by StyleCop rules.

  - by Hamish Grubijan

  The related default StyleCop rules are: Place using statements inside namespace. Sort using statements alphabetically. But ... System using come first (still trying to figure out if that means just using System; or using System[.*];). So, my use case: I find a bug and decide that I need to at least add an intelligible Assert to make debugging less painful for the next guy. So I start typing Debug.Assert( and intellisense marks it in Red. I hover mouse over Debug and between using System.Diagnostics; and System.Diagnostics.Debug I choose the former. This inserts using System.Diagnostics; after all other using statements. It would be nice if VS2010 did not assist me in writing code that won't build due to warnings as errors. How can I make VS2010 smarter? Is there some sort of setting, or does this require a full-fledged add-in of some sort?

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• calculating the index of an array C#

  - by Kerry G

  I want to display a list of the answers a student entered incorrectly. How do I identify the index of these questions? I am hoping to change the contents of a textbox to a list of the questions answered incorrectly, which would require calculating the index of each incorrect question. using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Windows.Forms; namespace WindowsFormsApplication5 { public partial class Form1 : Form { public Form1() { InitializeComponent(); } //return a pass/fail //return number of correct answers //return number of incorrect answers //return index figures of incorrect values public void examResults () { string[] correctAnswers = {B,D,A,A,C,A,B,A,C,D,B,C,D,A,D,C,C,B,D,A}; string[] studentResults = File.ReadAllLines("studentResults.txt"); var c = correctAnswers.Where((x, i) => x.Equals(studentResults[i])).Count(); if ( c <= 14) passFailBox.Text = "Student has failed the exam"; else passFailBox.Text = "Student has passed the exam"; numberCorrectBox.Text = "Student has answered" + c + "answers correctly"; int f; f= 21-c; numberIncorrectBox.Text = "Student has answered" + f + "answers incorrectly"; } } }

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• How can I refactor this to work without breaking the pattern horribly?

  - by SnOrfus

  I've got a base class object that is used for filtering. It's a template method object that looks something like this. public class Filter { public void Process(User u, GeoRegion r, int countNeeded) { List<account> selected = this.Select(u, r, countNeeded); // 1 List<account> filtered = this.Filter(selected, u, r, countNeeded); // 2 if (filtered.Count > 0) { /* do businessy stuff */ } // 3 if (filtered.Count < countNeeded) this.SendToSuccessor(u, r, countNeeded - filtered) // 4 } } Select(...), Filter(...) are protected abstract methods and implemented by the derived classes. Select(...) finds objects in the based on x criteria, Filter(...) filters those selected further. If the remaining filtered collection has more than 1 object in it, we do some business stuff with it (unimportant to the problem here). SendToSuccessor(...) is called if there weren't enough objects found after filtering (it's a composite where the next class in succession will also be derived from Filter but have different filtering criteria) All has been ok, but now I'm building another set of filters, which I was going to subclass from this. The filters I'm building however would require different params and I don't want to just implement those methods and not use the params or just add to the param list the ones I need and have them not used in the existing filters. They still perform the same logical process though. I also don't want to complicated the consumer code for this (which looks like this) Filter f = new Filter1(); Filter f2 = new Filter2(); Filter f3 = new Filter3(); f.Sucessor = f2; f2.Sucessor = f3; /* and so on adding filters as successors to previous ones */ foreach (User u in users) { foreach (GeoRegion r in regions) { f.Process(u, r, ##); } } How should I go about it?

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• Forwarding HTTP Request with Direct Server Return

  - by Daniel Crabtree

  I have servers spread across several data centers, each storing different files. I want users to be able to access the files on all servers through a single domain and have the individual servers return the files directly to the users. The following shows a simple example: 1) The user's browser requests http://www.example.com/files/file1.zip 2) Request goes to server A, based on the DNS A record for example.com. 3) Server A analyzes the request and works out that /files/file1.zip is stored on server B. 4) Server A forwards the request to server B. 5) Server B returns file1.zip directly to the user without going through server A. Note: steps 4 and 5 must be transparent to the user and cannot involve sending a redirect to the user as that would violate the requirement of a single domain. From my research, what I want to achieve is called "Direct Server Return" and it is a common setup for load balancing. It is also sometimes called a half reverse proxy. For step 4, it sounds like I need to do MAC Address Translation and then pass the request back onto the network and for servers outside the network of server A tunneling will be required. For step 5, I simply need to configure server B, as per the real servers in a load balancing setup. Namely, server B should have server A's IP address on the loopback interface and it should not answer any ARP requests for that IP address. My problem is how to actually achieve step 4? I have found plenty of hardware and software that can do this for simple load balancing at layer 4, but these solutions fall short and cannot handle the kind of custom routing I require. It seems like I will need to roll my own solution. Ideally, I would like to do the routing / forwarding at the web server level, i.e. in PHP or C# / ASP.net. However, I am open to doing it at a lower level such as Apache or IIS, or at an even lower level, i.e. a custom proxy service in front of everything.

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• need an empty XML while unmarshalling a JAXB annotated class

  - by sswdeveloper

  I have a JAXB annotated class Customer as follows @XmlRootElement(namespace = "http://www.abc.com/customer") public class Customer{ private String name; private Address address; @XmlTransient private HashSet set = new HashSet<String>(); public String getName(){ return name; } @XmlElement(name = "Name", namespace = "http://www.abc.com/customer" ) public void setName(String name){ this.name = name; set.add("name"); } public String getAddress(){ return address; } @XmlElement(name = "Address", namespace = "http://www.abc.com/customer") public void setAddress(Address address){ this.address = address; set.add("address"); } public HashSet getSet(){ return set; } } I need to return an empty XML representing this to the user, so that he may fill the necesary values in the XML and send a request So what I require is : <Customer> <Name></Name> <Address></Address> </Customer> If i simply create an empty object Customer cust = new Customer() ; marshaller.marshall(cust,sw); all I get is the toplevel element since the other fields of the class are unset. What can I do to get such an empty XML? I tried adding the nillable=true annotation to the elements however, this returns me an XML with the xsi:nil="true" which then causes my unmarshaller to ignore this. How do I achieve this?

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• finding N contiguous zero bits in an integer to the left of the MSB from another

  - by James Morris

  First we find the MSB of the first integer, and then try to find a region of N contiguous zero bits within the second number which is to the left of the MSB from the first integer. Here is the C code for my solution: typedef unsigned int t; unsigned const t_bits = sizeof(t) * CHAR_BIT; _Bool test_fit_within_left_of_msb( unsigned width, t val1, t val2, unsigned* offset_result) { unsigned offbit = 0; unsigned msb = 0; t mask; t b; while(val1 >>= 1) ++msb; while(offbit + width < t_bits - msb) { mask = (((t)1 << width) - 1) << (t_bits - width - offbit); b = val2 & mask; if (!b) { *offset_result = offbit; return true; } if (offbit++) /* this conditional bothers me! */ b <<= offbit - 1; while(b <<= 1) offbit++; } return false; } Aside from faster ways of finding the MSB of the first integer, the commented test for a zero offbit seems a bit extraneous, but necessary to skip the highest bit of type t if it is set. I have also implemented similar algorithms but working to the right of the MSB of the first number, so they don't require this seemingly extra condition. How can I get rid of this extra condition, or even, are there far more optimal solutions?

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• Callbacks on GUI Thread

  - by miguel

  We have an external data provider which, in its construtor, takes a callback thread for returning data upon. There are some issues in the system which I am suspicious are related to threading, however, in theory they cannot be, due to the fact that the callbacks should all be returned on the same thread. My question is, does code like this require thread synchronisation? class Foo { ExternalDataProvider _provider; public Foo() { // This is the c'tor for the xternal data provider, taking a callback loop as param _provider = new ExternalDataProvider(UILoop); _provider.DataArrived += ExternalProviderCallbackMethod; } public ExternalProviderCallbackMethod() { var itemArray[] = new String[4] { "item1", "item2", "item3", "item4" }; for (int i = 0; i < itemArray.Length; i++) { string s = itemArray[i]; switch(s) { case "item1": DoItem1Action(); break; case "item2": DoItem2Action(); break; default: DoDefaultAction(); break; } } } } The issue is that, very infrequently, DoItem2Action is executingwhen DoItem1Action should be exectuing. Is it at all possible threading is at fault here? In theory, as all callbacks are arriving on the same thread, they should be serialized, right? So there should be no need for thread sync here?

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• Legacy application creates dialogs in non-ui thread.

  - by Frater

  I've been working support for a while on a legacy application and I've noticed a bit of a problem. The system is an incredibly complex client/server with standard and custom frameworks. One of the custom frameworks built into the application involves validating workflow actions. It finds potential errors, separates them into warnings and errors, and passes the results back to the client. The main difference between warnings and errors is that warnings ask the user if they wish to ignore the error. The issue I have is that the dialog for this prompt is created on a non-ui thread, and thus we get cross-threading issues when the dialog is shown. I have attempted to invoke the showing of the dialog, however this fails because the window handle has not been created. (InvokeRequired returns false, which I assume in this case means it cannot find a decent handle in its parent tree, rather than that it doesn't require it.) Does anyone have any suggestions for how I can create this dialog and get the UI thread to set it up and call it?

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• typedef struct, circular dependency, forward definitions

  - by BlueChip

  The problem I have is a circular dependency issue in C header files ...Having looked around I suspect the solution will have something to do with Forward Definitions, but although there are many similar problems listed, none seem to offer the information I require to resolve this one... I have the following 5 source files: // fwd1.h #ifndef __FWD1_H #define __FWD1_H #include "fwd2.h" typedef struct Fwd1 { Fwd2 *f; } Fwd1; void fwd1 (Fwd1 *f1, Fwd2 *f2) ; #endif // __FWD1_H . // fwd1.c #include "fwd1.h" #include "fwd2.h" void fwd1 (Fwd1 *f1, Fwd2 *f2) { return; } . // fwd2.h #ifndef __FWD2_H #define __FWD2_H #include "fwd1.h" typedef struct Fwd2 { Fwd1 *f; } Fwd2; void fwd2 (Fwd1 *f1, Fwd2 *f2) ; #endif // __FWD2_H . // fwd2.c #include "fwd1.h" #include "fwd2.h" void fwd2 (Fwd1 *f1, Fwd2 *f2) { return; } . // fwdMain.c #include "fwd1.h" #include "fwd2.h" int main (int argc, char** argv, char** env) { Fwd1 *f1 = (Fwd1*)0; Fwd2 *f2 = (Fwd2*)0; fwd1(f1, f2); fwd2(f1, f2); return 0; } Which I am compiling with the command: gcc fwdMain.c fwd1.c fwd2.c -o fwd -Wall I have tried several ideas to resolve the compile errors, but have only managed to replace the errors with other errors ...How do I resolve the circular dependency issue with the least changes to my code? ...Ideally, as a matter of coding style, I would like to avoid putting the word "struct" all over my code.

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• what's the performance difference between int and varchar for primary keys

  - by user568576

  I need to create a primary key scheme for a system that will need peer to peer replication. So I'm planning to combine a unique system ID and a sequential number in some way to come up with unique ID's. I want to make sure I'll never run out of ID's, so I'm thinking about using a varchar field, since I could always add another character if I start running out. But I've read that integers are better optimized for this. So I have some questions... 1) Are integers really better optimized? And if they are, how much of a performance difference is there between varchars and integers? I'm going to use firebird for now. But I may switch later. Or possibly support multiple db's. So I'm looking for generalizations, if that's possible. 2) If integers are significantly better optimized, why is that? And is it likely that varchars will catch up in the future, so eventually it won't matter anyway? My varchar keys won't have any meaning, except for the unique system ID part. But I may want to obscure that somehow. Also, I plan to efficiently use all the bits of each character. I don't, for example, plan to code the integer 123 as the character string "123". So I don't think varchars will require more space than integers.

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• Returning C++ objects from Windows DLL

  - by R Samuel Klatchko

  Due to how Microsoft implements the heap in their non-DLL versions of the runtime, returning a C++ object from a DLL can cause problems: // dll.h DLL_EXPORT std::string somefunc(); and: // app.c - not part of DLL but in the main executable void doit() { std::string str(somefunc()); } The above code runs fine provided both the DLL and the EXE are built with the Multi-threaded DLL runtime library. But if the DLL and EXE are built without the DLL runtime library (either the single or multi-threaded versions), the code above fails (with a debug runtime, the code aborts immediately due to the assertion _CrtIsValidHeapPointer(pUserData) failing; with a non-debug runtime the heap gets corrupted and the program eventually fails elsewhere). Two questions: Is there a way to solve this other then requiring that all code use the DLL runtime? For people who distribute their libraries to third parties, how do you handle this? Do you not use C++ objects in your API? Do you require users of your library to use the DLL runtime? Something else?

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