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• How would I handle input with a Game Component?

  - by Aufziehvogel

  I am currently having problems from finding my way into the component-oriented XNA design. I read an overview over the general design pattern and googled a lot of XNA examples. However, they seem to be right on the opposite site. In the general design pattern, an object (my current player) is passed to InputComponent::update(Player). This means the class will know what to do and how this will affect the game (e.g. move person vs. scroll text in a menu). Yet, in XNA GameComponent::update(GameTime) is called automatically without a reference to the current player. The only XNA examples I found built some sort of higher-level Keyboard engine into the game component like this: class InputComponent: GameComponent { public void keyReleased(Keys); public void keyPressed(Keys); public bool keyDown(Keys); public void override update(GameTime gameTime) { // compare previous state with current state and // determine if released, pressed, down or nothing } } Some others went a bit further making it possible to use a Service Locator by a design like this: interface IInputComponent { public void downwardsMovement(Keys); public void upwardsMovement(Keys); public bool pausedGame(Keys); // determine which keys pressed and what that means // can be done for different inputs in different implementations public void override update(GameTime); } Yet, then I am wondering if it is possible to design an input class to resolve all possible situations. Like in a menu a mouse click can mean "click that button", but in game play it can mean "shoot that weapon". So if I am using such a modular design with game components for input, how much logic is to be put into the InputComponent / KeyboardComponent / GamepadComponent and where is the rest handled? What I had in mind, when I heard about Game Components and Service Locator in XNA was something like this: use Game Components to run the InputHandler automatically in the loop use Service Locator to be able to switch input at runtime (i.e. let player choose if he wants to use a gamepad or a keyboard; or which shall be player 1 and which player 2). However, now I cannot see how this can be done. First code example does not seem flexible enough, as on a game pad you could require some combination of buttons for something that is possible on keyboard with only one button or with the mouse) The second code example seems really hard to implement, because the InputComponent has to know in which context we are currently. Moreover, you could imagine your application to be multi-layered and let the key-stroke go through all layers to the bottom-layer which requires a different behaviour than the InputComponent would have guessed from the top-layer. The general design pattern with passing the Player to update() does not have a representation in XNA and I also cannot see how and where to decide which class should be passed to update(). At most time of course the player, but sometimes there could be menu items you have to or can click I see that the question in general is already dealt with here, but probably from a more elobate point-of-view. At least, I am not smart enough in game development to understand it. I am searching for a rather code-based example directly for XNA. And the answer there leaves (a noob like) me still alone in how the object that should receive the detected event is chosen. Like if I have a key-up event, should it go to the text box or to the player?

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• Seperation of project responsibilities in new project

  - by dreza

  We have very recently started a new project (MVC 3.0) and some of our early discussion has been around how the work and development will be split amongst the team members to ensure we get the least amount of overlap of work and so help make it a bit easier for each developer to get on and do their work. The project is expected to take about 6 months - 1 year (although not all developers are likely to be on and might filter off towards the end), Our team is going to be small so this will help out a bit I believe. The team will essentially consist of: 3 x developers (1 a slightly more experienced and will be the lead) 1 x project manager / product owner / tester An external company responsbile for doing our design work General project/development decisions so far have included: Develop in an Agile way using SCRUM techniques (We are still very much learning this approach as a company) Use MVVM archectecture Use Ninject and DI where possible Attempt to use as TDD as much as possible to drive development. Keep our controllers as skinny as possible Keep our views as simple as possible During our discussions two approaches have been broached as too how to seperate the workload given our objectives outlined above. OPTION 1: A framework seperation where each person is responsible for conceptual areas with overlap and discussion primarily in the integration areas. The integration areas would the responsibily of both developers as required. View prototypes (**Graphic designer**) | - Mockups | Views (Razor and view helpers etc) & Javascript (**Developer 1**) | - View models (Integration point) | Controllers and Application logic (**Developer 2**) | - Models (Integration point) | Domain model and persistence (**Developer 3**) PROS: Integration points are quite clear and so developers can work without dependencies on others fairly easily Code practices such as naming conventions and style is more easily managed in regards to consistancy as primarily only one developer will be handling an area CONS: Completion of an entire feature becomes a bit grey as no single person is responsible for an entire feature (story?) A person might not have a full appreciation for all areas of the project and so code overlap might be lacking if suddenly that person left. OPTION 2: A more task orientated approach where each person is responsible for the completion of the entire task from view - controller - model. PROS: A person is responsible for one entire feature so it's "complete" state can be clearly defined Code overlap into different areas will occur so each individual has good coverage over the entire application CONS: Overlap of development will occur in all the modules and developers can develop/extend without a true understanding of what the original code owner was intending. This could potentially lead more easily to code bloat? Following a convention might be harder as developers are adding to all areas of the project If a developer sets up a way of doing things would it be harder to enforce the other developers to follow that convention or even build on it (or even discuss it?). Dunno.. Bugs could more easily be introduced into areas not thought about by the developer It's easier to possibly to carry a team member in so far as one member just hacks code together to complete a task whilst another takes time to build a foundation that could be used by others and so help make future tasks easier i.e. starts building a framework? QUESTION: As it might appear I'm more in favor of option 1, however I'm interested to see how others might have approached this or what is the standard or best or preferred way of undertaking a project. Or indeed any different approach to handling this?

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• The Minimalist Approach to Content Governance - Request Phase

  - by Kellsey Ruppel

  Originally posted by John Brunswick. For each project, regardless of size, it is critical to understand the required ownership, business purpose, prerequisite education / resources needed to execute and success criteria around it. Without doing this, there is no way to get a handle on the content life-cyle, resulting in a mass of orphaned material. This lowers the quality of end user experiences.     The good news is that by using a simple process in this request phase - we will not have to revisit this phase unless something drastic changes in the project. For each of the elements mentioned above in this stage, the why, how (technically focused) and impact are outlined with the intent of providing the most value to a small team. 1. Ownership Why - Without ownership information it will not be possible to track and manage any of the content and take advantage of many features of enterprise content management technology. To hedge against this, we need to ensure that both a individual and their group or department within the organization are associated with the content. How - Apply metadata that indicates the owner and department or group that has responsibility for the content. Impact - It is possible to keep the content system optimized by running native reports against the meta-data and acting on them based on what has been outlined for success criteria. This will maximize end user experience, as content will be faster to locate and more relevant to the user by virtue of working through a smaller collection. 2. Business Purpose Why - This simple step will weed out requests that have tepid justification, as users will most likely not spend the effort to request resources if they do not have a real need. How - Use a simple online form to collect and workflow the request to management native to the content system. Impact - Minimizes the amount user generated content that is of low value to the organization. 3. Prerequisite Education Resources Needed Why - If a project cannot be properly staffed the probability of its success is going to be low. By outlining the resources needed - in both skill set and duration - it will cause the requesting party to think critically about the commitment needed to complete their project and what gap must be closed with regard to education of those resources. How - In the simple request form outlined above, resources and a commitment to fulfilling any needed education should be included with a brief acceptance clause that outlines the requesting party's commitment. Impact - This stage acts as a formal commitment to ensuring that resources are able to execute on the vision for the project. 4. Success Criteria Why - Similar to the business purpose, this is a key element in helping to determine if the project and its respective content should continue to exist if it does not meet its intended goal. How - Set a review point for the project content that will check the progress against the originally outlined success criteria and then determine the fate of the content. This can even include logic that will tell the content system to remove items that have not been opened by any users in X amount of time. Impact - This ensures that projects and their contents do not live past their useful lifespans. Just as with orphaned content, non-relevant information will slow user's access to relevant materials for the jobs. Request Phase Summary With a simple form that outlines the ownership of a project and its content, business purpose, education and resources, along with success criteria, we can ensure that an enterprise content management system will stay clean and relevant to end users - allowing it to deliver the most value possible. The key here is to make it straightforward to make the request and let the content management technology manage as much as possible through metadata, retention policies and workflow. Doing these basic steps will allow project content to get off to a great start in the enterprise! Stay tuned for the next installment - the "Create Phase" - covering security access and workflow involved in content creation, enabling a practical layer of governance over our enterprise content repository.

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• Password Cracking Windows Accounts

  - by Kevin

  At work we have laptops with encrypted harddrives. Most developers here (on occasion I have been guilty of it too) leave their laptops in hibernate mode when they take them home at night. Obviously, Windows (i.e. there is a program running in the background which does it for windows) must have a method to unencrypt the data on the drive, or it wouldn't be able to access it. That being said, I always thought that leaving a windows machine on in hibernate mode in a non-secure place (not at work on a lock) is a security threat, because someone could take the machine, leave it running, hack the windows accounts and use it to encrypt the data and steal the information. When I got to thinking about how I would go about breaking into the windows system without restarting it, I couldn't figure out if it was possible. I know it is possible to write a program to crack windows passwords once you have access to the appropriate file(s). But is it possible to execute a program from a locked Windows system that would do this? I don't know of a way to do it, but I am not a Windows expert. If so, is there a way to prevent it? I don't want to expose security vulnerabilities about how to do it, so I would ask that someone wouldn't post the necessary steps in details, but if someone could say something like "Yes, it's possible the USB drive allows arbitrary execution," that would be great! EDIT: The idea being with the encryption is that you can't reboot the system, because once you do, the disk encryption on the system requires a login before being able to start windows. With the machine being in hibernate, the system owner has already bypassed the encryption for the attacker, leaving windows as the only line of defense to protect the data.

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• Generating all unique combinations for "drive ya nuts" puzzle

  - by Yuval A

  A while back I wrote a simple python program to brute-force the single solution for the drive ya nuts puzzle. The puzzle consists of 7 hexagons with the numbers 1-6 on them, and all pieces must be aligned so that each number is adjacent to the same number on the next piece. The puzzle has ~1.4G non-unique possibilities: you have 7! options to sort the pieces by order (for example, center=0, top=1, continuing in clockwise order...). After you sorted the pieces, you can rotate each piece in 6 ways (each piece is a hexagon), so you get 6**7 possible rotations for a given permutation of the 7 pieces. Totalling: 7!*(6**7)=~1.4G possibilities. The following python code generates these possible solutions: def rotations(p): for i in range(len(p)): yield p[i:] + p[:i] def permutations(l): if len(l)<=1: yield l else: for perm in permutations(l[1:]): for i in range(len(perm)+1): yield perm[:i] + l[0:1] + perm[i:] def constructs(l): for p in permutations(l): for c in product(*(rotations(x) for x in p)): yield c However, note that the puzzle has only ~0.2G unique possible solutions, as you must divide the total number of possibilities by 6 since each possible solution is equivalent to 5 other solutions (simply rotate the entire puzzle by 1/6 a turn). Is there a better way to generate only the unique possibilities for this puzzle?

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• Graph colouring algorithm: typical scheduling problem

  - by newba

  Hi, I'm training code problems like UvA and I have this one in which I have to, given a set of n exams and k students enrolled in the exams, find whether it is possible to schedule all exams in two time slots. Input Several test cases. Each one starts with a line containing 1 < n < 200 of different examinations to be scheduled. The 2nd line has the number of cases k in which there exist at least 1 student enrolled in 2 examinations. Then, k lines will follow, each containing 2 numbers that specify the pair of examinations for each case above. (An input with n = 0 will means end of the input and is not to be processed). Output: You have to decide whether the examination plan is possible or not for 2 time slots. Example: Input: 3 3 0 1 1 2 2 0 9 8 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 Ouput: NOT POSSIBLE. POSSIBLE. I think the general approach is graph colouring, but I'm really a newb and I may confess that I had some trouble understanding the problem. Anyway, I'm trying to do it and then submit it. Could someone please help me doing some code for this problem? I will have to handle and understand this algo now in order to use it later, over and over. I prefer C or C++, but if you want, Java is fine to me ;) Thanks in advance

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• Compile and optimize for different target architectures

  - by Peter Smit

  Summary: I want to take advantage of compiler optimizations and processor instruction sets, but still have a portable application (running on different processors). Normally I could indeed compile 5 times and let the user choose the right one to run. My question is: how can I can automate this, so that the processor is detected at runtime and the right executable is executed without the user having to chose it? I have an application with a lot of low level math calculations. These calculations will typically run for a long time. I would like to take advantage of as much optimization as possible, preferably also of (not always supported) instruction sets. On the other hand I would like my application to be portable and easy to use (so I would not like to compile 5 different versions and let the user choose). Is there a possibility to compile 5 different versions of my code and run dynamically the most optimized version that's possible at execution time? With 5 different versions I mean with different instruction sets and different optimizations for processors. I don't care about the size of the application. At this moment I'm using gcc on Linux (my code is in C++), but I'm also interested in this for the Intel compiler and for the MinGW compiler for compilation to Windows. The executable doesn't have to be able to run on different OS'es, but ideally there would be something possible with automatically selecting 32 bit and 64 bit as well. Edit: Please give clear pointers how to do it, preferably with small code examples or links to explanations. From my point of view I need a super generic solution, which is applicable on any random C++ project I have later. Edit I assigned the bounty to ShuggyCoUk, he had a great number of pointers to look out for. I would have liked to split it between multiple answers but that is not possible. I'm not having this implemented yet, so the question is still 'open'! Please, still add and/or improve answers, even though there is no bounty to be given anymore. Thanks everybody!

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• How to customize RESTful Routes in Rails (basics)

  - by viatropos

  I have read through the Rails docs for Routing, Restful Resources, and the UrlHelper, and still don't understand best practices for creating complex/nested routes. The example I'm working on now is for events, which has_many rsvps. So a user's looking through a list of events, and clicks register, and goes through a registration process, etc. I want the urls to look like this: /events /events/123 # possible without title, like SO /events/123/my-event-title # canonical version /events/my-category/123/my-event-title # also possible like this /events/123/my-event-title/registration/new ... and all the restful nested resouces. Question is, how do I accomplish this with the minimal amount of code? Here's what I currently have: map.resources :events do |event| event.resources :rsvps, :as => "registration" end That gets me this: /events/123/registration What's the best way to accomplish the other 2 routes? /events/123/my-event-title # canonical version /events/my-category/123/my-event-title # also possible like this Where my-category is just an array of 10 possible types the event can be. I've modified Event#to_param to return "#{self.id.to_s}-#{self.title.parameterize}", but I'd prefer to have /id/title with the whole canonical-ness

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• Something like jQuery's .resizable but without the div's inside

  - by Brendon Muir

  Hi everyone, this is just a quick probe to see if this is technically possible. I'm wanting to enable the resizing of an image in the browser (also within a contentEditable area). Firefox and IE already allow this to be done with their inbuilt handles and it works fine. I'm wanting to implement something for Safari however because it doesn't support this natively. I've had a go with jQuery's resizable method and it does a very good job, however it relies on inserting a bunch of div's along with the image and wrapping that in a big div. This would normally be fine if we weren't concerned with the code generated in the contentEditable area, but we are because it's going to be saved back to the server. I could strip this extra stuff out on save, but I was thinking, is it technically possible to create a resizing script for images that doesn't rely on adding extra div's? Even if we decide to go without handles for now, and just concentrate on detecting when a user is close to the edge of the image, change the mouse cursor to a resizing one, and detect clicks and drags in the 5px's around the edge of the image, is this possible? If it's possible, I'm assuming (hoping) that perhaps it's already been done, but my searching hasn't turned up anything so far. Keen to hear any ideas :)

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• How 'terse' is too terse? -- Practical guidelines for expressing as much intent in as few characters

  - by Christopher Altman

  First, I love writing as little code as possible. I think, and please correct me, one of the golden rules of programming is to express your code in as few of character as possible while maintaining human readability. But I can get a little carried away. I can pack three or four lines into one statement, something like $startDate = $dateTime > time() ? mktime(0,0,0,date('m',time()-86400),date('d',time()*2),2011) : time(); (Note: this is a notional example) I can comprehend the above code when reading it. I prefer 'mushing' it all together because having less lines per page is a good thing to me. So my question: When writing code and thinking about how compact or terse you can express yourself, what are some guidelines you use? Do you write multiple lines because you think it helps other people? Do you write as little as possible, but use comments? Or do you always look for the way to write as little code as possible and enjoy the rewards of compact statements? (Just one slightly off topic comment: I love the Perl one-liners, but that is not what I am talking about here)

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• Pear HTML BBcode Hyperlink

  - by rrrfusco

  Has anyone used the PEAR HTML BBcode Package? I don't really understand why hyperlink target _blank does not open a new tab in firefox. INSERT Snippet [url=http://site.com t=_blank]Link[/url] PHP Require PEAR require_once 'HTML/BBCodeParser.php'; $options = @parse_ini_file('BBCodeParser.ini'); $parser = new HTML_BBCodeParser($options); $parser->setText($text); $parser->parse(); echo $parser->getParsed(); BBCodeParser.ini [HTML_BBCodeParser] ; http://articles.sitepoint.com/article/bb-code-php-application/ ; possible values: single|double ; use single or double quotes for attributes quotestyle = double ; possible values: all|nothing|strings ; quote all attribute values, none, or only the strings quotewhat = all ; the opening tag character open = "[" ; the closing tag character close = "]" ; possible values: true|false ; use xml style closing tags for single html tags (<img> or <img />) xmlclose = true ; possible values: a comma seperated list of filters ; comma seperated list of filters to use filters = Basic,Extended,Links,Images,Lists ; filters = Basic,Extended,Links,Images,Lists,Email,MyBB

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• shielding #include within namespace { } block?

  - by Jeff

  Edit: I know that method 1 is essentially invalid and will probably use method 2, but I'm looking for the best hack or a better solution to mitigate rampant, mutable namespace proliferation. I have multiple class or method definitions in one namespace that have different dependencies, and would like to use the fewest namespace blocks or explicit scopings possible but while grouping #include directives with the definitions that require them as best as possible. I've never seen any indication that any preprocessor could be told to exclude namespace {} scoping from #include contents, but I'm here to ask if something similar to this is possible: (see bottom for explanation of why I want something dead simple) // NOTE: apple.h, etc., contents are *NOT* intended to be in namespace Foo! // would prefer something most this: namespace Foo { #include "apple.h" B *A::blah(B const *x) { /* ... */ } #include "banana.h" int B::whatever(C const &var) { /* ... */ } #include "blueberry.h" void B::something() { /* ... */ } } // namespace Foo ... // over this: #include "apple.h" #include "banana.h" #include "blueberry.h" namespace Foo { B *A::blah(B const *x) { /* ... */ } int B::whatever(C const &var) { /* ... */ } void B::something() { /* ... */ } } // namespace Foo ... // or over this: #include "apple.h" namespace Foo { B *A::blah(B const *x) { /* ... */ } } // namespace Foo #include "banana.h" namespace Foo { int B::whatever(C const &var) { /* ... */ } } // namespace Foo #include "blueberry.h" namespace Foo { void B::something() { /* ... */ } } // namespace Foo My real problem is that I have projects where a module may need to be branched but have coexisting components from the branches in the same program. I have classes like FooA, etc., that I've called Foo::A in the hopes being able to branch less painfully as Foo::v1_2::A, where some program may need both a Foo::A and a Foo::v1_2::A. I'd like "Foo" or "Foo::v1_2" to show up only really once per file, as a single namespace block, if possible. Moreover, I tend to prefer to locate blocks of #include directives immediately above the first definition in the file that requires them. What's my best choice, or alternatively, what should I be doing instead of hijacking the namespaces?

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• Analyze log files from many languages using a single tool. And recommendations of logging frameworks

  - by Binary255

  We have a system build on lots of languages. The ones we are interested in logging, in order of priority, are: C/C++ PHP C# Bash Java Wish list: If it is possible, we would like logging to be achieved from the above languages in such a way that we may use a single log viewing tool for all of them. Ideally they would be in the same format, but next to that in as few formats as possible and readable from as many log file viewers as possible. If it is possible logging to a single log file or a set of log files would be nice. With a possibility to filter based on the source language that is being logged. We would like to copy the log files (or should be log to a database and copy it instead?) from multiple servers to a single location. So that we can analyze the log files from many servers at the same time (to see if any of our servers execute a certain piece legacy code for example). Being able to change logging level at runtime would be nice. Thank you for reading! It's quite a complex problem, I hope someone has wrestled with it before and has some valuable information!

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• git rebase without changing commit timestamps

  - by Olivier

  Would it make sense to perform git rebase while preserving the commit timestamps? I believe a consequence would be that the new branch will not necessarily have commit dates chronologically. Is that theoretically possible at all? (e.g. using plumbing commands; just curious here) If it is theoretically possible, then is it possible in practice with rebase, not to change the timestamps? For example, assume I have the following tree: master <jun 2010> | : : : oldbranch <feb 1984> : / oldcommit <jan 1984> Now, if I rebase oldbranch on master, the date of the commit changes from feb 1984 to jun 2010. Is it possible to change that behaviour so that the commit timestamp is not changed? In the end I would thus obtain: oldbranch <feb 1984> / master <jun 2010> | : Would that make sense at all? Is it even allowed in git to have a history where an old commit has a more recent commit as a parent? Edit A crucial question of Von C helped me understand what is going on: when your rebase, the committer's timestamp changes, but not the author's timestamp, which suddenly all makes sense. So my question was actually not precise enough. The answer is that rebase actually doesn't change the author's timestamps (you don't need to do anything for that), which suits me perfectly.

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• alternative to #include within namespace { } block

  - by Jeff

  Edit: I know that method 1 is essentially invalid and will probably use method 2, but I'm looking for the best hack or a better solution to mitigate rampant, mutable namespace proliferation. I have multiple class or method definitions in one namespace that have different dependencies, and would like to use the fewest namespace blocks or explicit scopings possible but while grouping #include directives with the definitions that require them as best as possible. I've never seen any indication that any preprocessor could be told to exclude namespace {} scoping from #include contents, but I'm here to ask if something similar to this is possible: (see bottom for explanation of why I want something dead simple) // NOTE: apple.h, etc., contents are *NOT* intended to be in namespace Foo! // would prefer something most this: namespace Foo { #include "apple.h" B *A::blah(B const *x) { /* ... */ } #include "banana.h" int B::whatever(C const &var) { /* ... */ } #include "blueberry.h" void B::something() { /* ... */ } } // namespace Foo ... // over this: #include "apple.h" #include "banana.h" #include "blueberry.h" namespace Foo { B *A::blah(B const *x) { /* ... */ } int B::whatever(C const &var) { /* ... */ } void B::something() { /* ... */ } } // namespace Foo ... // or over this: #include "apple.h" namespace Foo { B *A::blah(B const *x) { /* ... */ } } // namespace Foo #include "banana.h" namespace Foo { int B::whatever(C const &var) { /* ... */ } } // namespace Foo #include "blueberry.h" namespace Foo { void B::something() { /* ... */ } } // namespace Foo My real problem is that I have projects where a module may need to be branched but have coexisting components from the branches in the same program. I have classes like FooA, etc., that I've called Foo::A in the hopes being able to branch less painfully as Foo::v1_2::A, where some program may need both a Foo::A and a Foo::v1_2::A. I'd like "Foo" or "Foo::v1_2" to show up only really once per file, as a single namespace block, if possible. Moreover, I tend to prefer to locate blocks of #include directives immediately above the first definition in the file that requires them. What's my best choice, or alternatively, what should I be doing instead of hijacking the namespaces?

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• How to generate a number in arbitrary range using random()={0..1} preserving uniformness and density?

  - by psihodelia

  Generate a random number in range [x..y] where x and y are any arbitrary floating point numbers. Use function random(), which returns a random floating point number in range [0..1] from P uniformly distributed numbers (call it "density"). Uniform distribution must be preserved and P must be scaled as well. I think, there is no easy solution for such problem. To simplify it a bit, I ask you how to generate a number in interval [-0.5 .. 0.5], then in [0 .. 2], then in [-2 .. 0], preserving uniformness and density? Thus, for [0 .. 2] it must generate a random number from P*2 uniformly distributed numbers. The obvious simple solution random() * (x - y) + y will generate not all possible numbers because of the lower density for all abs(x-y)>1.0 cases. Many possible values will be missed. Remember, that random() returns only a number from P possible numbers. Then, if you multiply such number by Q, it will give you only one of P possible values, scaled by Q, but you have to scale density P by Q as well.

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• Permuting a binary tree without the use of lists

  - by Banang

  I need to find an algorithm for generating every possible permutation of a binary tree, and need to do so without using lists (this is because the tree itself carries semantics and restraints that cannot be translated into lists). I've found an algorithm that works for trees with the height of three or less, but whenever I get to greater hights, I loose one set of possible permutations per height added. Each node carries information about its original state, so that one node can determine if all possible permutations have been tried for that node. Also, the node carries information on weather or not it's been 'swapped', i.e. if it has seen all possible permutations of it's subtree. The tree is left-centered, meaning that the right node should always (except in some cases that I don't need to cover for this algorithm) be a leaf node, while the left node is always either a leaf or a branch. The algorithm I'm using at the moment can be described sort of like this: if the left child node has been swapped swap my right node with the left child nodes right node set the left child node as 'unswapped' if the current node is back to its original state swap my right node with the lowest left nodes' right node swap the lowest left nodes two childnodes set my left node as 'unswapped' set my left chilnode to use this as it's original state set this node as swapped return null return this; else if the left child has not been swapped if the result of trying to permute left child is null return the permutation of this node else return the permutation of the left child node if this node has a left node and a right node that are both leaves swap them set this node to be 'swapped' The desired behaviour of the algoritm would be something like this: branch / | branch 3 / | branch 2 / | 0 1 branch / | branch 3 / | branch 2 / | 1 0 <-- first swap branch / | branch 3 / | branch 1 <-- second swap / | 2 0 branch / | branch 3 / | branch 1 / | 0 2 <-- third swap branch / | branch 3 / | branch 0 <-- fourth swap / | 1 2 and so on... Sorry for the ridiculisly long and waddly explanation, would really, really apreciate any sort of help you guys could offer me. Thanks a bunch!

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• Namespace constraint with generic class decleration

  - by SomeGuy

  Good afternoon people, I would like to know if (and if so how) it is possible to define a namespace as a constraint parameter in a generic class declaration. What I have is this: namespace MyProject.Models.Entities <-- Contains my classes to be persisted in db namespace MyProject.Tests.BaseTest <-- Obvious i think Now the decleration of my 'BaseTest' class looks like so; public class BaseTest<T> This BaseTest does little more (at the time of writing) than remove all entities that were added to the database during testing. So typically I will have a test class declared as: public class MyEntityRepositoryTest : BaseTest<MyEntity> What i would LIKE to do is something similar to the following: public class BaseTest<T> where T : <is of the MyProject.Models.Entities namespace> Now i am aware that it would be entirely possible to simply declare a 'BaseEntity' class from which all entities created within the MyProject.Models.Entities namespace will inherit from; public class BaseTest<T> where T : MyBaseEntity but...I dont actually need to, or want to. Plus I am using an ORM and mapping entities with inheritance, although possible, adds a layer of complexity that is not required. So, is it possible to constrain a generic class parameter to a namespace and not a specific type ? Thank you for your time.

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• C# expression tree for ordinary code

  - by rwallace

  It's possible to create an expression tree, if you declare it as such. But is it possible to get an expression tree for an ordinary chunk of code such as a method or property getter? What I'm trying to do is, let's say for an order processing system, I have a class for order items: class Item : Entity { [Cascade] public Document document { get; set; } public int line { get; set; } public Product product { get; set; } public string description { get; set; } public decimal qty { get; set; } public decimal price { get; set; } public decimal net { get { return qty * price; } } public VatCode vat_code { get; set; } } where the net value equals qty * price, so I'd like to declare it as such, either with a property or method, and then also have the framework introspect that expression so it can generate appropriate SQL for defining a corresponding calculated column in a corresponding database view. The most obvious way to do this would be to get the expression tree for a property getter or a method, but I can't find any indication how to do this, or that it is possible. (I have found a way to get a method body as a byte stream, but that's not what's desired here.) If that isn't possible, I suppose the recommended solution would be to declare something like a static field that is an expression tree, and compile/run it at run time for internal use, and also introspect as normal for SQL generation?

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• Generics in a bidirectional association

  - by Verhoevenv

  Let's say I have two classes A and B, with B a subtype of A. This is only part of a richer type hierarchy, obviously, but I don't think that's relevant. Assume A is the root of the hierarchy. There is a collection class C that keeps track of a list of A's. However, I want to make C generic, so that it is possible to make an instance that only keeps B's and won't accept A's. class A(val c: C[A]) { c.addEntry(this) } class B(c: C[A]) extends A(c) class C[T <: A]{ val entries = new ArrayBuffer[T]() def addEntry(e: T) { entries += e } } object Generic { def main(args : Array[String]) { val c = new C[B]() new B(c) } } The code above obviously give the error 'type mismatch: found C[B], required C[A]' on the new B(c) line. I'm not sure how this can be fixed. It's not possible to make C covariant in T (like C[+T <: A]) because the ArrayBuffer is non-variantly typed in T. It's not possible to make the constructor of B require a C[B] because C can't be covariant. Am I barking up the wrong tree here? I'm a complete Scala newbie, so any ideas and tips might be helpful. Thank you! EDIT: Basically, what I'd like to have is that the compiler accepts both val c = new C[B]() new B(c) and val c = new C[A]() new B(c) but would reject val c = new C[B]() new A(c) It's probably possible to relax the typing of the ArrayBuffer in C to be A instead of T, and thus in the addEntry method as well, if that helps.

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• mysqld crashes on any statement

  - by ??iu

  I restarted my slave to change configuration settings to skip reverse hostname lookup on connecting and to enable the slow query log. I edited /etc/my.cnf making only these changes, then restarted mysqld with /etc/init.d/mysql restart All appeared to be well but when I connect to msyqld remotely or locally though it connects okay a slight problem is that mysqld crashes whenever you try to issue any kind of statement. The client looks like: Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 3 Server version: 5.1.31-1ubuntu2-log Type 'help;' or '\h' for help. Type '\c' to clear the buffer. mysql> show tables; ERROR 2006 (HY000): MySQL server has gone away No connection. Trying to reconnect... Connection id: 1 Current database: mydb ERROR 2006 (HY000): MySQL server has gone away No connection. Trying to reconnect... ERROR 2003 (HY000): Can't connect to MySQL server on 'xx.xx.xx.xx' (61) ERROR: Can't connect to the server ERROR 2006 (HY000): MySQL server has gone away No connection. Trying to reconnect... ERROR 2003 (HY000): Can't connect to MySQL server on 'xx.xx.xx.xx' (61) ERROR: Can't connect to the server ERROR 2006 (HY000): MySQL server has gone away Bus error The mysqld error log looks like: 101210 16:35:51 InnoDB: Error: (1500) Couldn't read the MAX(job_id) autoinc value from the index (PRIMARY). 101210 16:35:51 InnoDB: Assertion failure in thread 140245598570832 in file handler/ha_innodb.cc line 2595 InnoDB: Failing assertion: error == DB_SUCCESS InnoDB: We intentionally generate a memory trap. InnoDB: Submit a detailed bug report to http://bugs.mysql.com. InnoDB: If you get repeated assertion failures or crashes, even InnoDB: immediately after the mysqld startup, there may be InnoDB: corruption in the InnoDB tablespace. Please refer to InnoDB: http://dev.mysql.com/doc/refman/5.1/en/forcing-recovery.html InnoDB: about forcing recovery. 101210 16:35:51 - mysqld got signal 6 ; This could be because you hit a bug. It is also possible that this binary or one of the libraries it was linked against is corrupt, improperly built, or misconfigured. This error can also be caused by malfunctioning hardware. We will try our best to scrape up some info that will hopefully help diagnose the problem, but since we have already crashed, something is definitely wrong and this may fail. key_buffer_size=16777216 read_buffer_size=131072 max_used_connections=3 max_threads=600 threads_connected=3 It is possible that mysqld could use up to key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 1328077 K bytes of memory Hope that's ok; if not, decrease some variables in the equation. thd: 0x18209220 Attempting backtrace. You can use the following information to find out where mysqld died. If you see no messages after this, something went terribly wrong... stack_bottom = 0x7f8d791580d0 thread_stack 0x20000 /usr/sbin/mysqld(my_print_stacktrace+0x29) [0x8b4f89] /usr/sbin/mysqld(handle_segfault+0x383) [0x5f8f03] /lib/libpthread.so.0 [0x7f902a76a080] /lib/libc.so.6(gsignal+0x35) [0x7f90291f8fb5] /lib/libc.so.6(abort+0x183) [0x7f90291fabc3] /usr/sbin/mysqld(ha_innobase::open(char const*, int, unsigned int)+0x41b) [0x781f4b] /usr/sbin/mysqld(handler::ha_open(st_table*, char const*, int, int)+0x3f) [0x6db00f] /usr/sbin/mysqld(open_table_from_share(THD*, st_table_share*, char const*, unsigned int, unsigned int, unsigned int, st_table*, bool)+0x57a) [0x64760a] /usr/sbin/mysqld [0x63f281] /usr/sbin/mysqld(open_table(THD*, TABLE_LIST*, st_mem_root*, bool*, unsigned int)+0x626) [0x641e16] /usr/sbin/mysqld(open_tables(THD*, TABLE_LIST**, unsigned int*, unsigned int)+0x5db) [0x6429cb] /usr/sbin/mysqld(open_normal_and_derived_tables(THD*, TABLE_LIST*, unsigned int)+0x1e) [0x642b0e] /usr/sbin/mysqld(mysqld_list_fields(THD*, TABLE_LIST*, char const*)+0x22) [0x70b292] /usr/sbin/mysqld(dispatch_command(enum_server_command, THD*, char*, unsigned int)+0x146d) [0x60dc1d] /usr/sbin/mysqld(do_command(THD*)+0xe8) [0x60dda8] /usr/sbin/mysqld(handle_one_connection+0x226) [0x601426] /lib/libpthread.so.0 [0x7f902a7623ba] /lib/libc.so.6(clone+0x6d) [0x7f90292abfcd] Trying to get some variables. Some pointers may be invalid and cause the dump to abort... thd->query at 0x18213c70 = thd->thread_id=3 thd->killed=NOT_KILLED The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains information that should help you find out what is causing the crash. 101210 16:35:51 mysqld_safe Number of processes running now: 0 101210 16:35:51 mysqld_safe mysqld restarted InnoDB: The log sequence number in ibdata files does not match InnoDB: the log sequence number in the ib_logfiles! 101210 16:35:54 InnoDB: Database was not shut down normally! InnoDB: Starting crash recovery. InnoDB: Reading tablespace information from the .ibd files... InnoDB: Restoring possible half-written data pages from the doublewrite InnoDB: buffer... 101210 16:35:56 InnoDB: Started; log sequence number 456 143528628 101210 16:35:56 [Warning] 'user' entry 'root@PSDB102' ignored in --skip-name-resolve mode. 101210 16:35:56 [Warning] Neither --relay-log nor --relay-log-index were used; so replication may break when this MySQL server acts as a slave and has his hostname changed!! Please use '--relay-log=mysqld-relay-bin' to avoid this problem. 101210 16:35:56 [Note] Event Scheduler: Loaded 0 events 101210 16:35:56 [Note] /usr/sbin/mysqld: ready for connections. Version: '5.1.31-1ubuntu2-log' socket: '/var/run/mysqld/mysqld.sock' port: 3306 (Ubuntu) 101210 16:36:11 InnoDB: Error: (1500) Couldn't read the MAX(job_id) autoinc value from the index (PRIMARY). 101210 16:36:11 InnoDB: Assertion failure in thread 139955151501648 in file handler/ha_innodb.cc line 2595 InnoDB: Failing assertion: error == DB_SUCCESS InnoDB: We intentionally generate a memory trap. InnoDB: Submit a detailed bug report to http://bugs.mysql.com. InnoDB: If you get repeated assertion failures or crashes, even InnoDB: immediately after the mysqld startup, there may be InnoDB: corruption in the InnoDB tablespace. Please refer to InnoDB: http://dev.mysql.com/doc/refman/5.1/en/forcing-recovery.html InnoDB: about forcing recovery. 101210 16:36:11 - mysqld got signal 6 ; This could be because you hit a bug. It is also possible that this binary or one of the libraries it was linked against is corrupt, improperly built, or misconfigured. This error can also be caused by malfunctioning hardware. We will try our best to scrape up some info that will hopefully help diagnose the problem, but since we have already crashed, something is definitely wrong and this may fail. key_buffer_size=16777216 read_buffer_size=131072 max_used_connections=1 max_threads=600 threads_connected=1 It is possible that mysqld could use up to key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 1328077 K bytes of memory Hope that's ok; if not, decrease some variables in the equation. thd: 0x18588720 Attempting backtrace. You can use the following information to find out where mysqld died. If you see no messages after this, something went terribly wrong... stack_bottom = 0x7f49d916f0d0 thread_stack 0x20000 /usr/sbin/mysqld(my_print_stacktrace+0x29) [0x8b4f89] /usr/sbin/mysqld(handle_segfault+0x383) [0x5f8f03] /lib/libpthread.so.0 [0x7f4c8a73f080] /lib/libc.so.6(gsignal+0x35) [0x7f4c891cdfb5] /lib/libc.so.6(abort+0x183) [0x7f4c891cfbc3] /usr/sbin/mysqld(ha_innobase::open(char const*, int, unsigned int)+0x41b) [0x781f4b] /usr/sbin/mysqld(handler::ha_open(st_table*, char const*, int, int)+0x3f) [0x6db00f] /usr/sbin/mysqld(open_table_from_share(THD*, st_table_share*, char const*, unsigned int, unsigned int, unsigned int, st_table*, bool)+0x57a) [0x64760a] /usr/sbin/mysqld [0x63f281] /usr/sbin/mysqld(open_table(THD*, TABLE_LIST*, st_mem_root*, bool*, unsigned int)+0x626) [0x641e16] /usr/sbin/mysqld(open_tables(THD*, TABLE_LIST**, unsigned int*, unsigned int)+0x5db) [0x6429cb] /usr/sbin/mysqld(open_normal_and_derived_tables(THD*, TABLE_LIST*, unsigned int)+0x1e) [0x642b0e] /usr/sbin/mysqld(mysqld_list_fields(THD*, TABLE_LIST*, char const*)+0x22) [0x70b292] /usr/sbin/mysqld(dispatch_command(enum_server_command, THD*, char*, unsigned int)+0x146d) [0x60dc1d] /usr/sbin/mysqld(do_command(THD*)+0xe8) [0x60dda8] /usr/sbin/mysqld(handle_one_connection+0x226) [0x601426] /lib/libpthread.so.0 [0x7f4c8a7373ba] /lib/libc.so.6(clone+0x6d) [0x7f4c89280fcd] Trying to get some variables. Some pointers may be invalid and cause the dump to abort... thd->query at 0x18599950 = thd->thread_id=1 thd->killed=NOT_KILLED The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains information that should help you find out what is causing the crash. 101210 16:36:11 mysqld_safe Number of processes running now: 0 101210 16:36:11 mysqld_safe mysqld restarted The config is [mysqld_safe] socket = /var/run/mysqld/mysqld.sock nice = 0 [mysqld] innodb_file_per_table innodb_buffer_pool_size=10G innodb_log_buffer_size=4M innodb_flush_log_at_trx_commit=2 innodb_thread_concurrency=8 skip-slave-start server-id=3 # # * IMPORTANT # If you make changes to these settings and your system uses apparmor, you may # also need to also adjust /etc/apparmor.d/usr.sbin.mysqld. # user = mysql pid-file = /var/run/mysqld/mysqld.pid socket = /var/run/mysqld/mysqld.sock port = 3306 basedir = /usr datadir = /DB2/mysql tmpdir = /tmp skip-external-locking # # Instead of skip-networking the default is now to listen only on # localhost which is more compatible and is not less secure. #bind-address = 127.0.0.1 # # * Fine Tuning # key_buffer = 16M max_allowed_packet = 16M thread_stack = 128K thread_cache_size = 8 # This replaces the startup script and checks MyISAM tables if needed # the first time they are touched myisam-recover = BACKUP max_connections = 600 #table_cache = 64 #thread_concurrency = 10 # # * Query Cache Configuration # query_cache_limit = 1M query_cache_size = 32M # skip-federated slow-query-log skip-name-resolve Update: I followed the instructions as per http://dev.mysql.com/doc/refman/5.1/en/forcing-innodb-recovery.html and set innodb_force_recovery = 4 and the logs are showing a different error but the behavior is still the same: 101210 19:14:15 mysqld_safe mysqld restarted 101210 19:14:19 InnoDB: Started; log sequence number 456 143528628 InnoDB: !!! innodb_force_recovery is set to 4 !!! 101210 19:14:19 [Warning] 'user' entry 'root@PSDB102' ignored in --skip-name-resolve mode. 101210 19:14:19 [Warning] Neither --relay-log nor --relay-log-index were used; so replication may break when this MySQL server acts as a slave and has his hostname changed!! Please use '--relay-log=mysqld-relay-bin' to avoid this problem. 101210 19:14:19 [Note] Event Scheduler: Loaded 0 events 101210 19:14:19 [Note] /usr/sbin/mysqld: ready for connections. Version: '5.1.31-1ubuntu2-log' socket: '/var/run/mysqld/mysqld.sock' port: 3306 (Ubuntu) 101210 19:14:32 InnoDB: error: space object of table mydb/__twitter_friend, InnoDB: space id 1602 did not exist in memory. Retrying an open. 101210 19:14:32 InnoDB: error: space object of table mydb/access_request, InnoDB: space id 1318 did not exist in memory. Retrying an open. 101210 19:14:32 InnoDB: error: space object of table mydb/activity, InnoDB: space id 1595 did not exist in memory. Retrying an open. 101210 19:14:32 - mysqld got signal 11 ; This could be because you hit a bug. It is also possible that this binary or one of the libraries it was linked against is corrupt, improperly built, or misconfigured. This error can also be caused by malfunctioning hardware. We will try our best to scrape up some info that will hopefully help diagnose the problem, but since we have already crashed, something is definitely wrong and this may fail. key_buffer_size=16777216 read_buffer_size=131072 max_used_connections=1 max_threads=600 threads_connected=1 It is possible that mysqld could use up to key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 1328077 K bytes of memory Hope that's ok; if not, decrease some variables in the equation. thd: 0x1753c070 Attempting backtrace. You can use the following information to find out where mysqld died. If you see no messages after this, something went terribly wrong... stack_bottom = 0x7f7a0b5800d0 thread_stack 0x20000 /usr/sbin/mysqld(my_print_stacktrace+0x29) [0x8b4f89] /usr/sbin/mysqld(handle_segfault+0x383) [0x5f8f03] /lib/libpthread.so.0 [0x7f7cbc350080] /usr/sbin/mysqld(ha_innobase::innobase_get_index(unsigned int)+0x46) [0x77c516] /usr/sbin/mysqld(ha_innobase::innobase_initialize_autoinc()+0x40) [0x77c640] /usr/sbin/mysqld(ha_innobase::open(char const*, int, unsigned int)+0x3f3) [0x781f23] /usr/sbin/mysqld(handler::ha_open(st_table*, char const*, int, int)+0x3f) [0x6db00f] /usr/sbin/mysqld(open_table_from_share(THD*, st_table_share*, char const*, unsigned int, unsigned int, unsigned int, st_table*, bool)+0x57a) [0x64760a] /usr/sbin/mysqld [0x63f281] /usr/sbin/mysqld(open_table(THD*, TABLE_LIST*, st_mem_root*, bool*, unsigned int)+0x626) [0x641e16] /usr/sbin/mysqld(open_tables(THD*, TABLE_LIST**, unsigned int*, unsigned int)+0x5db) [0x6429cb] /usr/sbin/mysqld(open_normal_and_derived_tables(THD*, TABLE_LIST*, unsigned int)+0x1e) [0x642b0e] /usr/sbin/mysqld(mysqld_list_fields(THD*, TABLE_LIST*, char const*)+0x22) [0x70b292] /usr/sbin/mysqld(dispatch_command(enum_server_command, THD*, char*, unsigned int)+0x146d) [0x60dc1d] /usr/sbin/mysqld(do_command(THD*)+0xe8) [0x60dda8] /usr/sbin/mysqld(handle_one_connection+0x226) [0x601426] /lib/libpthread.so.0 [0x7f7cbc3483ba] /lib/libc.so.6(clone+0x6d) [0x7f7cbae91fcd] Trying to get some variables. Some pointers may be invalid and cause the dump to abort... thd->query at 0x1754d690 = thd->thread_id=1 thd->killed=NOT_KILLED The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains information that should help you find out what is causing the crash.

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• mysqld crashes on any statement

  - by ??iu

  I restarted my slave to change configuration settings to skip reverse hostname lookup on connecting and to enable the slow query log. I edited /etc/my.cnf making only these changes, then restarted mysqld with /etc/init.d/mysql restart All appeared to be well but when I connect to msyqld remotely or locally though it connects okay a slight problem is that mysqld crashes whenever you try to issue any kind of statement. The client looks like: Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 3 Server version: 5.1.31-1ubuntu2-log Type 'help;' or '\h' for help. Type '\c' to clear the buffer. mysql> show tables; ERROR 2006 (HY000): MySQL server has gone away No connection. Trying to reconnect... Connection id: 1 Current database: mydb ERROR 2006 (HY000): MySQL server has gone away No connection. Trying to reconnect... ERROR 2003 (HY000): Can't connect to MySQL server on 'xx.xx.xx.xx' (61) ERROR: Can't connect to the server ERROR 2006 (HY000): MySQL server has gone away No connection. Trying to reconnect... ERROR 2003 (HY000): Can't connect to MySQL server on 'xx.xx.xx.xx' (61) ERROR: Can't connect to the server ERROR 2006 (HY000): MySQL server has gone away Bus error The mysqld error log looks like: 101210 16:35:51 InnoDB: Error: (1500) Couldn't read the MAX(job_id) autoinc value from the index (PRIMARY). 101210 16:35:51 InnoDB: Assertion failure in thread 140245598570832 in file handler/ha_innodb.cc line 2595 InnoDB: Failing assertion: error == DB_SUCCESS InnoDB: We intentionally generate a memory trap. InnoDB: Submit a detailed bug report to http://bugs.mysql.com. InnoDB: If you get repeated assertion failures or crashes, even InnoDB: immediately after the mysqld startup, there may be InnoDB: corruption in the InnoDB tablespace. Please refer to InnoDB: http://dev.mysql.com/doc/refman/5.1/en/forcing-recovery.html InnoDB: about forcing recovery. 101210 16:35:51 - mysqld got signal 6 ; This could be because you hit a bug. It is also possible that this binary or one of the libraries it was linked against is corrupt, improperly built, or misconfigured. This error can also be caused by malfunctioning hardware. We will try our best to scrape up some info that will hopefully help diagnose the problem, but since we have already crashed, something is definitely wrong and this may fail. key_buffer_size=16777216 read_buffer_size=131072 max_used_connections=3 max_threads=600 threads_connected=3 It is possible that mysqld could use up to key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 1328077 K bytes of memory Hope that's ok; if not, decrease some variables in the equation. thd: 0x18209220 Attempting backtrace. You can use the following information to find out where mysqld died. If you see no messages after this, something went terribly wrong... stack_bottom = 0x7f8d791580d0 thread_stack 0x20000 /usr/sbin/mysqld(my_print_stacktrace+0x29) [0x8b4f89] /usr/sbin/mysqld(handle_segfault+0x383) [0x5f8f03] /lib/libpthread.so.0 [0x7f902a76a080] /lib/libc.so.6(gsignal+0x35) [0x7f90291f8fb5] /lib/libc.so.6(abort+0x183) [0x7f90291fabc3] /usr/sbin/mysqld(ha_innobase::open(char const*, int, unsigned int)+0x41b) [0x781f4b] /usr/sbin/mysqld(handler::ha_open(st_table*, char const*, int, int)+0x3f) [0x6db00f] /usr/sbin/mysqld(open_table_from_share(THD*, st_table_share*, char const*, unsigned int, unsigned int, unsigned int, st_table*, bool)+0x57a) [0x64760a] /usr/sbin/mysqld [0x63f281] /usr/sbin/mysqld(open_table(THD*, TABLE_LIST*, st_mem_root*, bool*, unsigned int)+0x626) [0x641e16] /usr/sbin/mysqld(open_tables(THD*, TABLE_LIST**, unsigned int*, unsigned int)+0x5db) [0x6429cb] /usr/sbin/mysqld(open_normal_and_derived_tables(THD*, TABLE_LIST*, unsigned int)+0x1e) [0x642b0e] /usr/sbin/mysqld(mysqld_list_fields(THD*, TABLE_LIST*, char const*)+0x22) [0x70b292] /usr/sbin/mysqld(dispatch_command(enum_server_command, THD*, char*, unsigned int)+0x146d) [0x60dc1d] /usr/sbin/mysqld(do_command(THD*)+0xe8) [0x60dda8] /usr/sbin/mysqld(handle_one_connection+0x226) [0x601426] /lib/libpthread.so.0 [0x7f902a7623ba] /lib/libc.so.6(clone+0x6d) [0x7f90292abfcd] Trying to get some variables. Some pointers may be invalid and cause the dump to abort... thd->query at 0x18213c70 = thd->thread_id=3 thd->killed=NOT_KILLED The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains information that should help you find out what is causing the crash. 101210 16:35:51 mysqld_safe Number of processes running now: 0 101210 16:35:51 mysqld_safe mysqld restarted InnoDB: The log sequence number in ibdata files does not match InnoDB: the log sequence number in the ib_logfiles! 101210 16:35:54 InnoDB: Database was not shut down normally! InnoDB: Starting crash recovery. InnoDB: Reading tablespace information from the .ibd files... InnoDB: Restoring possible half-written data pages from the doublewrite InnoDB: buffer... 101210 16:35:56 InnoDB: Started; log sequence number 456 143528628 101210 16:35:56 [Warning] 'user' entry 'root@PSDB102' ignored in --skip-name-resolve mode. 101210 16:35:56 [Warning] Neither --relay-log nor --relay-log-index were used; so replication may break when this MySQL server acts as a slave and has his hostname changed!! Please use '--relay-log=mysqld-relay-bin' to avoid this problem. 101210 16:35:56 [Note] Event Scheduler: Loaded 0 events 101210 16:35:56 [Note] /usr/sbin/mysqld: ready for connections. Version: '5.1.31-1ubuntu2-log' socket: '/var/run/mysqld/mysqld.sock' port: 3306 (Ubuntu) 101210 16:36:11 InnoDB: Error: (1500) Couldn't read the MAX(job_id) autoinc value from the index (PRIMARY). 101210 16:36:11 InnoDB: Assertion failure in thread 139955151501648 in file handler/ha_innodb.cc line 2595 InnoDB: Failing assertion: error == DB_SUCCESS InnoDB: We intentionally generate a memory trap. InnoDB: Submit a detailed bug report to http://bugs.mysql.com. InnoDB: If you get repeated assertion failures or crashes, even InnoDB: immediately after the mysqld startup, there may be InnoDB: corruption in the InnoDB tablespace. Please refer to InnoDB: http://dev.mysql.com/doc/refman/5.1/en/forcing-recovery.html InnoDB: about forcing recovery. 101210 16:36:11 - mysqld got signal 6 ; This could be because you hit a bug. It is also possible that this binary or one of the libraries it was linked against is corrupt, improperly built, or misconfigured. This error can also be caused by malfunctioning hardware. We will try our best to scrape up some info that will hopefully help diagnose the problem, but since we have already crashed, something is definitely wrong and this may fail. key_buffer_size=16777216 read_buffer_size=131072 max_used_connections=1 max_threads=600 threads_connected=1 It is possible that mysqld could use up to key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 1328077 K bytes of memory Hope that's ok; if not, decrease some variables in the equation. thd: 0x18588720 Attempting backtrace. You can use the following information to find out where mysqld died. If you see no messages after this, something went terribly wrong... stack_bottom = 0x7f49d916f0d0 thread_stack 0x20000 /usr/sbin/mysqld(my_print_stacktrace+0x29) [0x8b4f89] /usr/sbin/mysqld(handle_segfault+0x383) [0x5f8f03] /lib/libpthread.so.0 [0x7f4c8a73f080] /lib/libc.so.6(gsignal+0x35) [0x7f4c891cdfb5] /lib/libc.so.6(abort+0x183) [0x7f4c891cfbc3] /usr/sbin/mysqld(ha_innobase::open(char const*, int, unsigned int)+0x41b) [0x781f4b] /usr/sbin/mysqld(handler::ha_open(st_table*, char const*, int, int)+0x3f) [0x6db00f] /usr/sbin/mysqld(open_table_from_share(THD*, st_table_share*, char const*, unsigned int, unsigned int, unsigned int, st_table*, bool)+0x57a) [0x64760a] /usr/sbin/mysqld [0x63f281] /usr/sbin/mysqld(open_table(THD*, TABLE_LIST*, st_mem_root*, bool*, unsigned int)+0x626) [0x641e16] /usr/sbin/mysqld(open_tables(THD*, TABLE_LIST**, unsigned int*, unsigned int)+0x5db) [0x6429cb] /usr/sbin/mysqld(open_normal_and_derived_tables(THD*, TABLE_LIST*, unsigned int)+0x1e) [0x642b0e] /usr/sbin/mysqld(mysqld_list_fields(THD*, TABLE_LIST*, char const*)+0x22) [0x70b292] /usr/sbin/mysqld(dispatch_command(enum_server_command, THD*, char*, unsigned int)+0x146d) [0x60dc1d] /usr/sbin/mysqld(do_command(THD*)+0xe8) [0x60dda8] /usr/sbin/mysqld(handle_one_connection+0x226) [0x601426] /lib/libpthread.so.0 [0x7f4c8a7373ba] /lib/libc.so.6(clone+0x6d) [0x7f4c89280fcd] Trying to get some variables. Some pointers may be invalid and cause the dump to abort... thd->query at 0x18599950 = thd->thread_id=1 thd->killed=NOT_KILLED The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains information that should help you find out what is causing the crash. 101210 16:36:11 mysqld_safe Number of processes running now: 0 101210 16:36:11 mysqld_safe mysqld restarted The config is [mysqld_safe] socket = /var/run/mysqld/mysqld.sock nice = 0 [mysqld] innodb_file_per_table innodb_buffer_pool_size=10G innodb_log_buffer_size=4M innodb_flush_log_at_trx_commit=2 innodb_thread_concurrency=8 skip-slave-start server-id=3 # # * IMPORTANT # If you make changes to these settings and your system uses apparmor, you may # also need to also adjust /etc/apparmor.d/usr.sbin.mysqld. # user = mysql pid-file = /var/run/mysqld/mysqld.pid socket = /var/run/mysqld/mysqld.sock port = 3306 basedir = /usr datadir = /DB2/mysql tmpdir = /tmp skip-external-locking # # Instead of skip-networking the default is now to listen only on # localhost which is more compatible and is not less secure. #bind-address = 127.0.0.1 # # * Fine Tuning # key_buffer = 16M max_allowed_packet = 16M thread_stack = 128K thread_cache_size = 8 # This replaces the startup script and checks MyISAM tables if needed # the first time they are touched myisam-recover = BACKUP max_connections = 600 #table_cache = 64 #thread_concurrency = 10 # # * Query Cache Configuration # query_cache_limit = 1M query_cache_size = 32M # skip-federated slow-query-log skip-name-resolve Update: I followed the instructions as per http://dev.mysql.com/doc/refman/5.1/en/forcing-innodb-recovery.html and set innodb_force_recovery = 4 and the logs are showing a different error but the behavior is still the same: 101210 19:14:15 mysqld_safe mysqld restarted 101210 19:14:19 InnoDB: Started; log sequence number 456 143528628 InnoDB: !!! innodb_force_recovery is set to 4 !!! 101210 19:14:19 [Warning] 'user' entry 'root@PSDB102' ignored in --skip-name-resolve mode. 101210 19:14:19 [Warning] Neither --relay-log nor --relay-log-index were used; so replication may break when this MySQL server acts as a slave and has his hostname changed!! Please use '--relay-log=mysqld-relay-bin' to avoid this problem. 101210 19:14:19 [Note] Event Scheduler: Loaded 0 events 101210 19:14:19 [Note] /usr/sbin/mysqld: ready for connections. Version: '5.1.31-1ubuntu2-log' socket: '/var/run/mysqld/mysqld.sock' port: 3306 (Ubuntu) 101210 19:14:32 InnoDB: error: space object of table mydb/__twitter_friend, InnoDB: space id 1602 did not exist in memory. Retrying an open. 101210 19:14:32 InnoDB: error: space object of table mydb/access_request, InnoDB: space id 1318 did not exist in memory. Retrying an open. 101210 19:14:32 InnoDB: error: space object of table mydb/activity, InnoDB: space id 1595 did not exist in memory. Retrying an open. 101210 19:14:32 - mysqld got signal 11 ; This could be because you hit a bug. It is also possible that this binary or one of the libraries it was linked against is corrupt, improperly built, or misconfigured. This error can also be caused by malfunctioning hardware. We will try our best to scrape up some info that will hopefully help diagnose the problem, but since we have already crashed, something is definitely wrong and this may fail. key_buffer_size=16777216 read_buffer_size=131072 max_used_connections=1 max_threads=600 threads_connected=1 It is possible that mysqld could use up to key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 1328077 K bytes of memory Hope that's ok; if not, decrease some variables in the equation. thd: 0x1753c070 Attempting backtrace. You can use the following information to find out where mysqld died. If you see no messages after this, something went terribly wrong... stack_bottom = 0x7f7a0b5800d0 thread_stack 0x20000 /usr/sbin/mysqld(my_print_stacktrace+0x29) [0x8b4f89] /usr/sbin/mysqld(handle_segfault+0x383) [0x5f8f03] /lib/libpthread.so.0 [0x7f7cbc350080] /usr/sbin/mysqld(ha_innobase::innobase_get_index(unsigned int)+0x46) [0x77c516] /usr/sbin/mysqld(ha_innobase::innobase_initialize_autoinc()+0x40) [0x77c640] /usr/sbin/mysqld(ha_innobase::open(char const*, int, unsigned int)+0x3f3) [0x781f23] /usr/sbin/mysqld(handler::ha_open(st_table*, char const*, int, int)+0x3f) [0x6db00f] /usr/sbin/mysqld(open_table_from_share(THD*, st_table_share*, char const*, unsigned int, unsigned int, unsigned int, st_table*, bool)+0x57a) [0x64760a] /usr/sbin/mysqld [0x63f281] /usr/sbin/mysqld(open_table(THD*, TABLE_LIST*, st_mem_root*, bool*, unsigned int)+0x626) [0x641e16] /usr/sbin/mysqld(open_tables(THD*, TABLE_LIST**, unsigned int*, unsigned int)+0x5db) [0x6429cb] /usr/sbin/mysqld(open_normal_and_derived_tables(THD*, TABLE_LIST*, unsigned int)+0x1e) [0x642b0e] /usr/sbin/mysqld(mysqld_list_fields(THD*, TABLE_LIST*, char const*)+0x22) [0x70b292] /usr/sbin/mysqld(dispatch_command(enum_server_command, THD*, char*, unsigned int)+0x146d) [0x60dc1d] /usr/sbin/mysqld(do_command(THD*)+0xe8) [0x60dda8] /usr/sbin/mysqld(handle_one_connection+0x226) [0x601426] /lib/libpthread.so.0 [0x7f7cbc3483ba] /lib/libc.so.6(clone+0x6d) [0x7f7cbae91fcd] Trying to get some variables. Some pointers may be invalid and cause the dump to abort... thd->query at 0x1754d690 = thd->thread_id=1 thd->killed=NOT_KILLED The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains information that should help you find out what is causing the crash.

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• Run Your Tests With Any NUnit Version

  - by Alois Kraus

  I always thought that the NUnit test runners and the test assemblies need to reference the same NUnit.Framework version. I wanted to be able to run my test assemblies with the newest GUI runner (currently 2.5.3). Ok so all I need to do is to reference both NUnit versions the newest one and the official for the current project. There is a nice article form Kent Bogart online how to reference the same assembly multiple times with different versions. The magic works by referencing one NUnit assembly with an alias which does prefix all types inside it. Then I could decorate my tests with the TestFixture and Test attribute from both NUnit versions and everything worked fine except that this was ugly. After playing a little bit around to make it simpler I found that I did not need to reference both NUnit.Framework assemblies. The test runners do not require the TestFixture and Test attribute in their specific version. That is really neat since the test runners are instructed by attributes what to do in a declarative way there is really no need to tie the runners to a specific version. At its core NUnit has this little method hidden to find matching TestFixtures and Tests   public bool CanBuildFrom(Type type) {     if (!(!type.IsAbstract || type.IsSealed))     {         return false;     }     return (((Reflect.HasAttribute(type,           "NUnit.Framework.TestFixtureAttribute", true) ||               Reflect.HasMethodWithAttribute(type, "NUnit.Framework.TestAttribute"       , true)) ||               Reflect.HasMethodWithAttribute(type, "NUnit.Framework.TestCaseAttribute"   , true)) ||               Reflect.HasMethodWithAttribute(type, "NUnit.Framework.TheoryAttribute"     , true)); } That is versioning and backwards compatibility at its best. I tell NUnit what to do by decorating my tests classes with NUnit Attributes and the runner executes my intent without the need to bind me to a specific version. The contract between NUnit versions is actually a bit more complex (think of AssertExceptions) but this is also handled nicely by using not the concrete type but simply to check for the catched exception type by string. What can we learn from this? Versioning can be easy if the contract is small and the users of your library use it in a declarative way (Attributes). Everything beyond it will force you to reference several versions of the same assembly with all its consequences. Type equality is lost between versions so none of your casts will work. That means that you cannot simply use IBigInterface in two versions. You will need a wrapper to call the correct versioned one. To get out of this mess you can use one (and only one) version agnostic driver to encapsulate your business logic from the concrete versions. This is of course more work but as NUnit shows it can be easy. Simplicity is therefore not a nice thing to have but also requirement number one if you intend to make things more complex in version two and want to support any version (older and newer). Any interaction model above easy will not be maintainable. There are different approached to versioning. Below are my own personal observations how versioning works within the  .NET Framwork and NUnit.   Versioning Models 1. Bug Fixing and New Isolated Features When you only need to fix bugs there is no need to break anything. This is especially true when you have a big API surface. Microsoft did this with the .NET Framework 3.0 which did leave the CLR as is but delivered new assemblies for the features WPF, WCF and Windows Workflow Foundations. Their basic model was that the .NET 2.0 assemblies were declared as red assemblies which must not change (well mostly but each change was carefully reviewed to minimize the risk of breaking changes as much as possible) whereas the new green assemblies of .NET 3,3.5 did not have such obligations since they did implement new unrelated features which did not have any impact on the red assemblies. This is versioning strategy aimed at maximum compatibility and the delivery of new unrelated features. If you have a big API surface you should strive hard to do the same or you will break your customers code with every release. 2. New Breaking Features There are times when really new things need to be added to an existing product. The .NET Framework 4.0 did change the CLR in many ways which caused subtle different behavior although the API´s remained largely unchanged. Sometimes it is possible to simply recompile an application to make it work (e.g. changed method signature void Func() –> bool Func()) but behavioral changes need much more thought and cannot be automated. To minimize the impact .NET 2.0,3.0,3.5 applications will not automatically use the .NET 4.0 runtime when installed but they will keep using the “old” one. What is interesting is that a side by side execution model of both CLR versions (2 and 4) within one process is possible. Key to success was total isolation. You will have 2 GCs, 2 JIT compilers, 2 finalizer threads within one process. The two .NET runtimes cannot talk  (except via the usual IPC mechanisms) to each other. Both runtimes share nothing and run independently within the same process. This enables Explorer plugins written for the CLR 2.0 to work even when a CLR 4 plugin is already running inside the Explorer process. The price for isolation is an increased memory footprint because everything is loaded and running two times.   3. New Non Breaking Features It really depends where you break things. NUnit has evolved and many different Assert, Expect… methods have been added. These changes are all localized in the NUnit.Framework assembly which can be easily extended. As long as the test execution contract (TestFixture, Test, AssertException) remains stable it is possible to write test executors which can run tests written for NUnit 10 because the execution contract has not changed. It is possible to write software which executes other components in a version independent way but this is only feasible if the interaction model is relatively simple.   Versioning software is hard and it looks like it will remain hard since you suddenly work in a severely constrained environment when you try to innovate and to keep everything backwards compatible at the same time. These are contradicting goals and do not play well together. The easiest way out of this is to carefully watch what your customers are doing with your software. Minimizing the impact is much easier when you do not need to guess how many people will be broken when this or that is removed.

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• Mocking the Unmockable: Using Microsoft Moles with Gallio

  - by Thomas Weller

  Usual opensource mocking frameworks (like e.g. Moq or Rhino.Mocks) can mock only interfaces and virtual methods. In contrary to that, Microsoft’s Moles framework can ‘mock’ virtually anything, in that it uses runtime instrumentation to inject callbacks in the method MSIL bodies of the moled methods. Therefore, it is possible to detour any .NET method, including non-virtual/static methods in sealed types. This can be extremely helpful when dealing e.g. with code that calls into the .NET framework, some third-party or legacy stuff etc… Some useful collected resources (links to website, documentation material and some videos) can be found in my toolbox on Delicious under this link: http://delicious.com/thomasweller/toolbox+moles A Gallio extension for Moles Originally, Moles is a part of Microsoft’s Pex framework and thus integrates best with Visual Studio Unit Tests (MSTest). However, the Moles sample download contains some additional assemblies to also support other unit test frameworks. They provide a Moled attribute to ease the usage of mole types with the respective framework (there are extensions for NUnit, xUnit.net and MbUnit v2 included with the samples). As there is no such extension for the Gallio platform, I did the few required lines myself – the resulting Gallio.Moles.dll is included with the sample download. With this little assembly in place, it is possible to use Moles with Gallio like that: [Test, Moled] public void SomeTest() {     ... What you can do with it Moles can be very helpful, if you need to ‘mock’ something other than a virtual or interface-implementing method. This might be the case when dealing with some third-party component, legacy code, or if you want to ‘mock’ the .NET framework itself. Generally, you need to announce each moled type that you want to use in a test with the MoledType attribute on assembly level. For example: [assembly: MoledType(typeof(System.IO.File))] Below are some typical use cases for Moles. For a more detailed overview (incl. naming conventions and an instruction on how to create the required moles assemblies), please refer to the reference material above.  Detouring the .NET framework Imagine that you want to test a method similar to the one below, which internally calls some framework method:   public void ReadFileContent(string fileName) {     this.FileContent = System.IO.File.ReadAllText(fileName); } Using a mole, you would replace the call to the File.ReadAllText(string) method with a runtime delegate like so: [Test, Moled] [Description("This 'mocks' the System.IO.File class with a custom delegate.")] public void ReadFileContentWithMoles() {     // arrange ('mock' the FileSystem with a delegate)     System.IO.Moles.MFile.ReadAllTextString = (fname => fname == FileName ? FileContent : "WrongFileName");       // act     var testTarget = new TestTarget.TestTarget();     testTarget.ReadFileContent(FileName);       // assert     Assert.AreEqual(FileContent, testTarget.FileContent); } Detouring static methods and/or classes A static method like the below… public static string StaticMethod(int x, int y) {     return string.Format("{0}{1}", x, y); } … can be ‘mocked’ with the following: [Test, Moled] public void StaticMethodWithMoles() {     MStaticClass.StaticMethodInt32Int32 = ((x, y) => "uups");       var result = StaticClass.StaticMethod(1, 2);       Assert.AreEqual("uups", result); } Detouring constructors You can do this delegate thing even with a class’ constructor. The syntax for this is not all  too intuitive, because you have to setup the internal state of the mole, but generally it works like a charm. For example, to replace this c’tor… public class ClassWithCtor {     public int Value { get; private set; }       public ClassWithCtor(int someValue)     {         this.Value = someValue;     } } … you would do the following: [Test, Moled] public void ConstructorTestWithMoles() {     MClassWithCtor.ConstructorInt32 =            ((@class, @value) => new MClassWithCtor(@class) {ValueGet = () => 99});       var classWithCtor = new ClassWithCtor(3);       Assert.AreEqual(99, classWithCtor.Value); } Detouring abstract base classes You can also use this approach to ‘mock’ abstract base classes of a class that you call in your test. Assumed that you have something like that: public abstract class AbstractBaseClass {     public virtual string SaySomething()     {         return "Hello from base.";     } }      public class ChildClass : AbstractBaseClass {     public override string SaySomething()     {         return string.Format(             "Hello from child. Base says: '{0}'",             base.SaySomething());     } } Then you would set up the child’s underlying base class like this: [Test, Moled] public void AbstractBaseClassTestWithMoles() {     ChildClass child = new ChildClass();     new MAbstractBaseClass(child)         {                 SaySomething = () => "Leave me alone!"         }         .InstanceBehavior = MoleBehaviors.Fallthrough;       var hello = child.SaySomething();       Assert.AreEqual("Hello from child. Base says: 'Leave me alone!'", hello); } Setting the moles behavior to a value of  MoleBehaviors.Fallthrough causes the ‘original’ method to be called if a respective delegate is not provided explicitly – here it causes the ChildClass’ override of the SaySomething() method to be called. There are some more possible scenarios, where the Moles framework could be of much help (e.g. it’s also possible to detour interface implementations like IEnumerable<T> and such…). One other possibility that comes to my mind (because I’m currently dealing with that), is to replace calls from repository classes to the ADO.NET Entity Framework O/R mapper with delegates to isolate the repository classes from the underlying database, which otherwise would not be possible… Usage Since Moles relies on runtime instrumentation, mole types must be run under the Pex profiler. This only works from inside Visual Studio if you write your tests with MSTest (Visual Studio Unit Test). While other unit test frameworks generally can be used with Moles, they require the respective tests to be run via command line, executed through the moles.runner.exe tool. A typical test execution would be similar to this: moles.runner.exe <mytests.dll> /runner:<myframework.console.exe> /args:/<myargs> So, the moled test can be run through tools like NCover or a scripting tool like MSBuild (which makes them easy to run in a Continuous Integration environment), but they are somewhat unhandy to run in the usual TDD workflow (which I described in some detail here). To make this a bit more fluent, I wrote a ReSharper live template to generate the respective command line for the test (it is also included in the sample download – moled_cmd.xml). - This is just a quick-and-dirty ‘solution’. Maybe it makes sense to write an extra Gallio adapter plugin (similar to the many others that are already provided) and include it with the Gallio download package, if  there’s sufficient demand for it. As of now, the only way to run tests with the Moles framework from within Visual Studio is by using them with MSTest. From the command line, anything with a managed console runner can be used (provided that the appropriate extension is in place)… A typical Gallio/Moles command line (as generated by the mentioned R#-template) looks like that: "%ProgramFiles%\Microsoft Moles\bin\moles.runner.exe" /runner:"%ProgramFiles%\Gallio\bin\Gallio.Echo.exe" "Gallio.Moles.Demo.dll" /args:/r:IsolatedAppDomain /args:/filter:"ExactType:TestFixture and Member:ReadFileContentWithMoles" -- Note: When using the command line with Echo (Gallio’s console runner), be sure to always include the IsolatedAppDomain option, otherwise the tests won’t use the instrumentation callbacks! -- License issues As I already said, the free mocking frameworks can mock only interfaces and virtual methods. if you want to mock other things, you need the Typemock Isolator tool for that, which comes with license costs (Although these ‘costs’ are ridiculously low compared to the value that such a tool can bring to a software project, spending money often is a considerable gateway hurdle in real life...).  The Moles framework also is not totally free, but comes with the same license conditions as the (closely related) Pex framework: It is free for academic/non-commercial use only, to use it in a ‘real’ software project requires an MSDN Subscription (from VS2010pro on). The demo solution The sample solution (VS 2008) can be downloaded from here. It contains the Gallio.Moles.dll which provides the here described Moled attribute, the above mentioned R#-template (moled_cmd.xml) and a test fixture containing the above described use case scenarios. To run it, you need the Gallio framework (download) and Microsoft Moles (download) being installed in the default locations. Happy testing…

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• Exploring the Excel Services REST API

  - by jamiet

  Over the last few years Analysis Services guru Chris Webb and I have been on something of a crusade to enable better access to data that is locked up in countless Excel workbooks that litter the hard drives of enterprise PCs. The most prominent manifestation of that crusade up to now has been a forum thread that Chris began on Microsoft Answers entitled Excel Web App API? Chris began that thread with: I was wondering whether there was an API for the Excel Web App? Specifically, I was wondering if it was possible (or if it will be possible in the future) to expose data in a spreadsheet in the Excel Web App as an OData feed, in the way that it is possible with Excel Services? Up to recently the last 10 words of that paragraph "in the way that it is possible with Excel Services" had completely washed over me however a comment on my recent blog post Thoughts on ExcelMashup.com (and a rant) by Josh Booker in which Josh said: Excel Services is a service application built for sharepoint 2010 which exposes a REST API for excel documents. We're looking forward to pros like you giving it a try now that Office365 makes sharepoint more easily accessible.  Can't wait for your future blog about using REST API to load data from Excel on Offce 365 in SSIS. made me think that perhaps the Excel Services REST API is something I should be looking into and indeed that is what I have been doing over the past few days. And you know what? I'm rather impressed with some of what Excel Services' REST API has to offer. Unfortunately Excel Services' REST API also has one debilitating aspect that renders this blog post much less useful than it otherwise would be; namely that it is not publicly available from the Excel Web App on SkyDrive. Therefore all I can do in this blog post is show you screenshots of what the REST API provides in Sharepoint rather than linking you directly to those REST resources; that's a great shame because one of the benefits of a REST API is that it is easily and ubiquitously demonstrable from a web browser. Instead I am hosting a workbook on Sharepoint in Office 365 because that does include Excel Services' REST API but, again, all I can do is show you screenshots. N.B. If anyone out there knows how to make Office-365-hosted spreadsheets publicly-accessible (i.e. without requiring a username/password) please do let me know (because knowing which forum on which to ask the question is an exercise in futility). In order to demonstrate Excel Services' REST API I needed some decent data and for that I used the World Tourism Organization Statistics Database and Yearbook - United Nations World Tourism Organization dataset hosted on Azure Datamarket (its free, by the way); this dataset "provides comprehensive information on international tourism worldwide and offers a selection of the latest available statistics on international tourist arrivals, tourism receipts and expenditure" and you can explore the data for yourself here. If you want to play along at home by viewing the data as it exists in Excel then it can be viewed here. Let's dive in.   The root of Excel Services' REST API is the model resource which resides at: http://server/_vti_bin/ExcelRest.aspx/Documents/TourismExpenditureInMillionsOfUSD.xlsx/model Note that this is true for every workbook hosted in a Sharepoint document library - each Excel workbook is a RESTful resource. (Update: Mark Stacey on Twitter tells me that "It's turned off by default in onpremise Sharepoint (1 tickbox to turn on though)". Thanks Mark!) The data is provided as an ATOM feed but I have Firefox's feed reading ability turned on so you don't see the underlying XML goo. As you can see there are four top level resources, Ranges, Charts, Tables and PivotTables; exploring one of those resources is where things get interesting. Let's take a look at the Tables Resource: http://server/_vti_bin/ExcelRest.aspx/Documents/TourismExpenditureInMillionsOfUSD.xlsx/model/Tables Our workbook contains only one table, called ‘Table1’ (to reiterate, you can explore this table yourself here). Viewing that table via the REST API is pretty easy, we simply append the name of the table onto our previous URI: http://server/_vti_bin/ExcelRest.aspx/Documents/TourismExpenditureInMillionsOfUSD.xlsx/model/Tables('Table1') As you can see, that quite simply gives us a representation of the data in that table. What you cannot see from this screenshot is that this is pure HTML that is being served up; that is all well and good but actually we can do more interesting things. If we specify that the data should be returned not as HTML but as: http://server/_vti_bin/ExcelRest.aspx/Documents/TourismExpenditureInMillionsOfUSD.xlsx/model/Tables('Table1')?$format=image then that data comes back as a pure image and can be used in any web page where you would ordinarily use images. This is the thing that I really like about Excel Services’ REST API – we can embed an image in any web page but instead of being a copy of the data, that image is actually live – if the underlying data in the workbook were to change then hitting refresh will show a new image. Pretty cool, no? The same is true of any Charts or Pivot Tables in your workbook - those can be embedded as images too and if the underlying data changes, boom, the image in your web page changes too. There is a lot of data in the workbook so the image returned by that previous URI is too large to show here so instead let’s take a look at a different resource, this time a range: http://server/_vti_bin/ExcelRest.aspx/Documents/TourismExpenditureInMillionsOfUSD.xlsx/model/Ranges('Data!A1|C15') That URI returns cells A1 to C15 from a worksheet called “Data”: And if we ask for that as an image again: http://server/_vti_bin/ExcelRest.aspx/Documents/TourismExpenditureInMillionsOfUSD.xlsx/model/Ranges('Data!A1|C15')?$format=image Were this image resource not behind a username/password then this would be a live image of the data in the workbook as opposed to one that I had to copy and upload elsewhere. Nonetheless I hope this little wrinkle doesn't detract from the inate value of what I am trying to articulate here; that an existing image in a web page can be changed on-the-fly simply by inserting some data into an Excel workbook. I for one think that that is very cool indeed! I think that's enough in the way of demo for now as this shows what is possible using Excel Services' REST API. Of course, not all features work quite how I would like and here is a bulleted list of some of my more negative feedback: The URIs are pig-ugly. Are "_vti_bin" & "ExcelRest.aspx" really necessary as part of the URI? Would this not be better: http://server/Documents/TourismExpenditureInMillionsOfUSD.xlsx/Model/Tables(‘Table1’) That URI provides the necessary addressability and is a lot easier to remember. Discoverability of these resources is not easy, we essentially have to handcrank a URI ourselves. Take the example of embedding a chart into a blog post - would it not be better if I could browse first through the document library to an Excel workbook and THEN through the workbook to the chart/range/table that I am interested in? Call it a wizard if you like. That would be really cool and would, I am sure, promote this feature and cut down on the copy-and-paste disease that the REST API is meant to alleviate. The resources that I demonstrated can be returned as feeds as well as images or HTML simply by changing the format parameter to ?$format=atom however for some inexplicable reason they don't return OData and no-one on the Excel Services team can tell me why (believe me, I have asked). $format is an OData parameter however other useful parameters such as $top and $filter are not supported. It would be nice if they were. Although I haven't demonstrated it here Excel Services' REST API does provide a makeshift way of altering the data by changing the value of specific cells however what it does not allow you to do is add new data into the workbook. Google Docs allows this and was one of the motivating factors for Chris Webb's forum post that I linked to above. None of this works for Excel workbooks hosted on SkyDrive This blog post is as long as it needs to be for a short introduction so I'll stop now. If you want to know more than I recommend checking out a few links: Excel Services REST API documentation on MSDNSo what does REST on Excel Services look like??? by Shahar PrishExcel Services in SharePoint 2010 REST API Syntax by Christian Stich. Any thoughts? Let's hear them in the comments section below! @Jamiet 

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