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• Advice on logic circuits and serial communications

  - by Spencer Ruport

  As far as I understand the serial port so far, transferring data is done over pin 3. As shown here: There are two things that make me uncomfortable about this. The first is that it seems to imply that the two connected devices agree on a signal speed and the second is that even if they are configured to run at the same speed you run into possible synchronization issues... right? Such things can be handled I suppose but it seems like there must be a simpler method. What seems like a better approach to me would be to have one of the serial port pins send a pulse that indicates that the next bit is ready to be stored. So if we're hooking these pins up to a shift register we basically have: (some pulse pin)-clk, tx-d Is this a common practice? Is there some reason not to do this? EDIT Mike shouldn't have deleted his answer. This I2C (2 pin serial) approach seems fairly close to what I did. The serial port doesn't have a clock you're right nobugz but that's basically what I've done. See here: private void SendBytes(byte[] data) { int baudRate = 0; int byteToSend = 0; int bitToSend = 0; byte bitmask = 0; byte[] trigger = new byte[1]; trigger[0] = 0; SerialPort p; try { p = new SerialPort(cmbPorts.Text); } catch { return; } if (!int.TryParse(txtBaudRate.Text, out baudRate)) return; if (baudRate < 100) return; p.BaudRate = baudRate; for (int index = 0; index < data.Length * 8; index++) { byteToSend = (int)(index / 8); bitToSend = index - (byteToSend * 8); bitmask = (byte)System.Math.Pow(2, bitToSend); p.Open(); p.Parity = Parity.Space; p.RtsEnable = (byte)(data[byteToSend] & bitmask) > 0; s = p.BaseStream; s.WriteByte(trigger[0]); p.Close(); } } Before anyone tells me how ugly this is or how I'm destroying my transfer speeds my quick answer is I don't care about that. My point is this seems much much simpler than the method you described in your answer nobugz. And it wouldn't be as ugly if the .Net SerialPort class gave me more control over the pin signals. Are there other serial port APIs that do?

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• Fixing Robocopy for SQL Server Jobs

  - by Most Valuable Yak (Rob Volk)

  Robocopy is one of, if not the, best life-saving/greatest-thing-since-sliced-bread command line utilities ever to come from Microsoft.  If you're not using it already, what are you waiting for? Of course, being a Microsoft product, it's not exactly perfect. ;)  Specifically, it sets the ERRORLEVEL to a non-zero value even if the copy is successful.  This causes a problem in SQL Server job steps, since non-zero ERRORLEVELs report as failed. You can work around this by having your SQL job go to the next step on failure, but then you can't determine if there was a genuine error.  Plus you still see annoying red X's in your job history.  One way I've found to avoid this is to use a batch file that runs Robocopy, and I add some commands after it (in red): robocopy d:\backups \\BackupServer\BackupFolder *.bak rem suppress successful robocopy exit statuses, only report genuine errors (bitmask 16 and 8 settings)set/A errlev="%ERRORLEVEL% & 24" rem exit batch file with errorlevel so SQL job can succeed or fail appropriatelyexit/B %errlev% (The REM statements are simply comments and don't need to be included in the batch file) The SET command lets you use expressions when you use the /A switch.  So I set an environment variable "errlev" to a bitwise AND with the ERRORLEVEL value. Robocopy's exit codes use a bitmap/bitmask to specify its exit status.  The bits for 1, 2, and 4 do not indicate any kind of failure, but 8 and 16 do.  So by adding 16 + 8 to get 24, and doing a bitwise AND, I suppress any of the other bits that might be set, and allow either or both of the error bits to pass. The next step is to use the EXIT command with the /B switch to set a new ERRORLEVEL value, using the "errlev" variable.  This will now return zero (unless Robocopy had real errors) and allow your SQL job step to report success. This technique should also work for other command-line utilities.  The only issues I've found is that it requires the commands to be part of a batch file, so if you use Robocopy directly in your SQL job step you'd need to place it in a batch.  If you also have multiple Robocopy calls, you'll need to place the SET/A command ONLY after the last one.  You'd therefore lose any errors from previous calls, unless you use multiple "errlev" variables and AND them together. (I'll leave this as an exercise for the reader) The SET/A syntax also permits other kinds of expressions to be calculated.  You can get a full list by running "SET /?" on a command prompt.

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• target-action uicontrolevents

  - by Fabrizio Farinelli

  I must be missing something obvious here but ... UIControl has a method - (void)addTarget:(id)target action:(SEL)action forControlEvents: (UIControlEvents)controlEvents which lets you add an action to be called when any of the given controlEvents occur. ControlEvents are a bitmask of events which tell you if a touch went down, or up inside, or was dragged etc., there's about 16 of them, you or them together and get called when any of them occur. The selector can have one of the following signatures - (void)action - (void)action:(id)sender - (void)action:(id)sender forEvent:(UIEvent *) none of those tell you what the control event bitmask was. The UIEvent is something slightly different, it's related to the actual touch event and doesn't (I think) contain the UIControlEvent. The sender (UIControl) doesn't have a way to find the control events either. I'd like to have one method which deals with a number of control events as I have some common code regardless of which event or events happened but I still need to know what the UIControlEvents were for some specific processing. Am I missing a way to find out what UIControlEvents were used when the action was called or do I really have to separate my code into -(void)actionWithUIControlEventX; -(void)actionWithUIControlEventY;

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• How to genrate a monochrome bit mask for a 32bit bitmap

  - by Mordachai

  Under Win32, it is a common technique to generate a monochrome bitmask from a bitmap for transparency use by doing the following: SetBkColor(hdcSource, clrTransparency); VERIFY(BitBlt(hdcMask, 0, 0, bm.bmWidth, bm.bmHeight, hdcSource, 0, 0, SRCCOPY)); This assumes that hdcSource is a memory DC holding the source image, and hdcMask is a memory DC holding a monochrome bitmap of the same size (so both are 32x32, but the source is 4 bit color, while the target is 1bit monochrome). However, this seems to fail for me when the source is 32 bit color + alpha. Instead of getting a monochrome bitmap in hdcMask, I get a mask that is all black. No bits get set to white (1). Whereas this works for the 4bit color source. My search-foo is failing, as I cannot seem to find any references to this particular problem. I have isolated that this is indeed the issue in my code: i.e. if I use a source bitmap that is 16 color (4bit), it works; if I use a 32 bit image, it produces the all-black mask. Is there an alternate method I should be using in the case of 32 bit color images? Is there an issue with the alpha channel that overrides the normal behavior of the above technique? Thanks for any help you may have to offer! ADDENDUM: I am still unable to find a technique that creates a valid monochrome bitmap for my GDI+ produced source bitmap. I have somewhat alleviated my particular issue by simply not generating a monochrome bitmask at all, and instead I'm using TransparentBlt(), which seems to get it right (but I don't know what they're doing internally that's any different that allows them to correctly mask the image). It might be useful to have a really good, working function: HBITMAP CreateTransparencyMask(HDC hdc, HBITMAP hSource, COLORREF crTransparency); Where it always creates a valid transparency mask, regardless of the color depth of hSource. Ideas?

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• Connecting an overloaded PyQT signal using new-style syntax

  - by Claudio

  I am designing a custom widget which is basically a QGroupBox holding a configurable number of QCheckBox buttons, where each one of them should control a particular bit in a bitmask represented by a QBitArray. In order to do that, I added the QCheckBox instances to a QButtonGroup, with each button given an integer ID: def populate(self, num_bits, parent = None): """ Adds check boxes to the GroupBox according to the bitmask size """ self.bitArray.resize(num_bits) layout = QHBoxLayout() for i in range(num_bits): cb = QCheckBox() cb.setText(QString.number(i)) self.buttonGroup.addButton(cb, i) layout.addWidget(cb) self.setLayout(layout) Then, each time a user would click on a checkbox contained in self.buttonGroup, I'd like self.bitArray to be notified so I can set/unset the corresponding bit in the array. For that I intended to connect QButtonGroup's buttonClicked(int) signal to QBitArray's toggleBit(int) method and, to be as pythonic as possible, I wanted to use new-style signals syntax, so I tried this: self.buttonGroup.buttonClicked.connect(self.bitArray.toggleBit) The problem is that buttonClicked is an overloaded signal, so there is also the buttonClicked(QAbstractButton*) signature. In fact, when the program is executing I get this error when I click a check box: The debugged program raised the exception unhandled TypeError "QBitArray.toggleBit(int): argument 1 has unexpected type 'QCheckBox'" which clearly shows the toggleBit method received the buttonClicked(QAbstractButton*) signal instead of the buttonClicked(int) one. So, the question is, how can we specify, using new-style syntax, that self.buttonGroup emits the buttonClicked(int) signal instead of the default overload - buttonClicked(QAbstractButton*)?

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• Pixel perfect collision with paths (Android)

  - by keysersoze

  Hi I'm writing a game and I'm trying to do some pixel perfect collisions with paths. The player's character has a bitmask which looks for example like this: Currenly my code that handles player's collision with path looks like this: private boolean isTerrainCollisionDetected() { if(collisionRegion.op(player.getBounds(), terrain.getBottomPathBounds(), Region.Op.INTERSECT) || collisionRegion.op(player.getBounds(), terrain.getTopPathBounds(), Region.Op.INTERSECT)) { collisionRegion.getBounds(collisionRect); for(int i = collisionRect.left; i < collisionRect.right; i++) { for(int j = collisionRect.top; j < collisionRect.bottom; j++) { if(player.getBitmask().getPixel(i - player.getX(), j - player.getY()) != Color.TRANSPARENT) { return true; } } } } return false; } The problem is that collisions aren't pixel perfect. It detects collisions in situations like this: The question is: what can I do to improve my collision detection?

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• Which numeral systems are useful in computer science?

  - by authchir

  I am wondering which numeral system different programmers are using, or would use if their language has support for them. As an example, in C++ we can use: Octal by prefixing with 0 (e.g. 0377) Decimal by default (e.g. 255) Hexadecimal by prefixing with 0x (e.g. 0xff) When working with bitmask, I am using hexadecimal but would sometimes want to be able to express binary numbers directly. I know some programming language support it with 0b syntax (e.g. 0b11111111). Is there any other numeric system useful in some computer science domain (e.g. cryptography, codecs, 3D graphics, etc)?

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• Escaping escape Characters

  - by Alix Axel

  I'm trying to mimic the json_encode bitmask flags implemented in PHP 5.3.0, here is the string I have: $s = addslashes('O\'Rei"lly'); // O\'Rei\"lly Doing json_encode($str, JSON_HEX_APOS | JSON_HEX_QUOT) outputs the following: "O\\\u0027Rei\\\u0022lly" And I'm currently doing this in PHP versions older than 5.3.0: str_replace(array('\\"', "\\'"), array('\\u0022', '\\\u0027'), json_encode($s)) or str_replace(array('\\"', '\\\''), array('\\u0022', '\\\u0027'), json_encode($s)) Which correctly outputs the same result: "O\\\u0027Rei\\\u0022lly" I'm having trouble understanding why do I need to replace single quotes ('\\\'' or even "\\'" [surrounding quotes excluded]) with '\\\u0027' and not just '\\u0027'.

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• C# can't cast bool to int

  - by Svetlozar Angelov

  We all know that in C# we can't cast bool to int. I wanted to see what is the binary representation of true with bitmask, but I can't use (bool & int).. I think the problem is the architecture desicion "true is true, not any number != 0" (C++) and I was wondering what the benefits of such an architecture are? What is so bad with the C true/false concept?

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• How do you turn off a specific bit in a bit mask?

  - by Brian

  In TSql, how do you turn off a specific bit in a bitmask without having to check to see if the bit is set or not?

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• C/C++ efficient bit array

  - by aaa

  hi. Can you recommend efficient/clean way to manipulate arbitrary length bit array? right now I am using regular int/char bitmask, but those are not very clean when array length is greater than datatype length. std vector<bool> is not available for me. thanks

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• How to restrict windows service to X cores?

  - by Martinnj

  I'm currently trying ot figure out a decent/nice way of determening what core(s) a single service should run on, in Windows Server 2008. I'm aware that for procceses there is two ways to do it: set affinity through task manager after proccess is launched. use "start /AFFINITY 0x1" or similar bitmask However this does not seem to work very well with services. When i try to launch the exe that the service will also run (the one that needs restriction) it just spawns a new commandline (and starts the process) but the process terminates shortly after. Does anyone here know how to do a similar trick for services? It is not important what core it is running on, it just needs to be restricted to only one. And preferably it should be something that can be automated, so we do not have to interfere when there is a server restart.

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• CodePlex Daily Summary for Saturday, June 09, 2012

  CodePlex Daily Summary for Saturday, June 09, 2012Popular ReleasesARCBots API Program: ARCBots API Program v3 STABLE: Stable Release, you can find the update notes in the source code.Microsoft SQL Server Product Samples: Database: AdventureWorks Sample Reports 2008 R2: AdventureWorks Sample Reports 2008 R2.zip contains several reports include Sales Reason Comparisons SQL2008R2.rdl which uses Adventure Works DW 2008R2 as a data source reference. For more information, go to Sales Reason Comparisons report.RULI Chain Code Image Generator: RULI Chain Code BW Image Generator v. 0.4: added features: - 3x3 bitmask support - 7x7 bitmask support - app icon added some refactoring for later library-creationThe Chronicles of Asku: Alpha Test v1.1: Welcome to the Chronicles of Asku alpha test. The current state of the game is 2 tomb floors, level 10 cap, and almost all core systems in the game, excluding a store that you buy armor in. This is just a test for downloading the game, and severe bug hunts... INSTRUCTIONS: When you download the folder, right click within the folder and select EXTRACT ALL Run Setup.exe Follow any on screen instructions DO NOT TRY TO LOAD A CHARACTER IF YOU HAVE NEVER SAVED ONE BEFORE Patch 1.1 -Added a...Json.NET: Json.NET 4.5 Release 7: Fix - Fixed Metro build to pass Windows Application Certification Kit on Windows 8 Release Preview Fix - Fixed Metro build error caused by an anonymous type Fix - Fixed ItemConverter not being used when serializing dictionaries Fix - Fixed an incorrect object being passed to the Error event when serializing dictionaries Fix - Fixed decimal properties not being correctly ignored with DefaultValueHandlingLINQ Extensions Library: 1.0.3.0: New to release 1.0.3.0:Combinatronics: Combinations (unique) Combinations (with repetition) Permutations (unique) Permutations (with repetition) Convert jagged arrays to fixed multidimensional arrays Convert fixed multidimensional arrays to jagged arrays ElementAtMax ElementAtMin ElementAtAverage New set of array extension (1.0.2.8):Rotate Flip Resize (maintaing data) Split Fuse Replace Append and Prepend extensions (1.0.2.7) IndexOf extensions (1.0.2.7) Ne...Audio Pitch & Shift: Audio Pitch And Shift 4.5.0: Added Instruments tab for modules Open folder content feature Some bug fixesPython Tools for Visual Studio: 1.5 Beta 1: We’re pleased to announce the release of Python Tools for Visual Studio 1.5 Beta. Python Tools for Visual Studio (PTVS) is an open-source plug-in for Visual Studio which supports programming with the Python language. PTVS supports a broad range of features including: • Supports CPython, IronPython, Jython and PyPy • Python editor with advanced member, signature intellisense and refactoring • Code navigation: “Find all refs”, goto definition, and object browser • Local and remote debugging •...Circuit Diagram: Circuit Diagram 2.0 Beta 1: New in this release: Automatically flip components when placing Delete components using keyboard delete key Resize document Document properties window Print document Recent files list Confirm when exiting with unsaved changes Thumbnail previews in Windows Explorer for CDDX files Show shortcut keys in toolbox Highlight selected item in toolbox Zoom using mouse scroll wheel while holding down ctrl key Plugin support for: Custom export formats Custom import formats Open...Umbraco CMS: Umbraco CMS 5.2 Beta: The future of Umbracov5 represents the future architecture of Umbraco, so please be aware that while it's technically superior to v4 it's not yet on a par feature or performance-wise. What's new? For full details see our http://progress.umbraco.org task tracking page showing all items complete for 5.2. In a nutshellPackage Builder Starter Kits Dynamic Extension Methods Querying / IsHelpers Friendly alt template URLs Localization Various bug fixes / performance enhancements Gett...JayData - The cross-platform HTML5 data-management library for JavaScript: JayData 1.0.5: JayData is a unified data access library for JavaScript developers to query and update data from different sources like WebSQL, IndexedDB, OData, Facebook or YQL. See it in action in this 6 minutes video New features in JayData 1.0.5http://jaydata.org/blog/jaydata-1.0.5-is-here-with-authentication-support-and-more http://jaydata.org/blog/release-notes Sencha Touch 2 module (read-only)This module can be used to bind data retrieved by JayData to Sencha Touch 2 generated user interface. (exam...32feet.NET: 3.5: This version changes the 32feet.NET library (both desktop and NETCF) to use .NET Framework version 3.5. Previously we compiled for .NET v2.0. There are no code changes from our version 3.4. See the 3.4 release for more information. Changes due to compiling for .NET 3.5Applications should be changed to use NET/NETCF v3.5. Removal of class InTheHand.Net.Bluetooth.AsyncCompletedEventArgs, which we provided on NETCF. We now just use the standard .NET System.ComponentModel.AsyncCompletedEvent...DotNetNuke® Links: 06.02.01: Added new DNN 6.2.0 beta social feature "friends" BugfixesApplication Architecture Guidelines: Application Architecture Guidelines 3.0.7: 3.0.7Jolt Environment: Jolt v2 Stable: Many new features. Follow development here for more information: http://www.rune-server.org/runescape-development/rs-503-client-server/projects/298763-jolt-environment-v2.html Setup instructions in downloadSharePoint Euro 2012 - UEFA European Football Predictor: havivi.euro2012.wsp (1.5): New fetures:Multilingual Support Max users property in Standings Web Part Games time zone change (UTC +1) bug fix - Version 1.4 locking problem http://euro2012.codeplex.com/discussions/358262 bug fix - Field Title not found (v.1.3) German SP http://euro2012.codeplex.com/discussions/358189#post844228 Bug fix - Access is denied.for users with contribute rights Bug fix - Installing on non-English version of SharePoint Bug fix - Title Rules Installing SharePoint Euro 2012 PredictorSharePoint E...myManga: myManga v1.0.0.4: ChangeLogUpdating from Previous Version: Extract contents of Release - myManga v1.0.0.4.zip to previous version's folder. Replaces: myManga.exe BakaBox.dll CoreMangaClasses.dll Manga.dll Plugins/MangaReader.manga.dll Plugins/MangaFox.manga.dll Plugins/MangaHere.manga.dll Plugins/MangaPanda.manga.dllMVVM Light Toolkit: V4RC (binaries only) including Windows 8 RP: This package contains all the latest DLLs for MVVM Light V4 RC. It includes the DLLs for Windows 8 Release Preview. An updated Nuget package is also available at http://nuget.org/packages/MvvmLightLibsPreviewExtAspNet: ExtAspNet v3.1.7: +2012-06-03 v3.1.7 -?????????BUG，??????RadioButtonList?，AJAX????????BUG（swtseaman、????）。 +?Grid?BoundField、HyperLinkField、LinkButtonField、WindowField??HtmlEncode?HtmlEncodeFormatString（TiDi）。 -HtmlEncode?HtmlEncodeFormatString??????true，??????HTML????????。 -??????Asp.Net??GridView?BoundField?????????。 -http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.boundfield.htmlencode -?Grid?HyperLinkField、WindowField??UrlEncode??，????URL??（???true）。 -?????????????，?????????????...LiveChat Starter Kit: LCSK v1.5.2: New features: Visitor location (City - Country) from geo-location Pass configuration via javascript for the chat box New visitor identification (no more using the IP address as visitor identification) To update from 1.5.1 Run the /src/1.5.2-sql-updates.txt SQL script to update your database tables. If you have it installed via NuGet, simply update your package and the file will be included so you can run the update script. New installation The easiest way to add LCSK to your app is by...New ProjectsAdvanceWars: Advance Wars For NetARCBots API Program: This is a simple API program designed for quick use for the ARCBots API.AutoUpdaterdotNET: AutoUpdater.NET is a class library that allows .net developers to easily add auto update functionality to their project.C++ AMP Conformance Test Suite: C++ AMP Conformance Test Suite contains a set of tests to aid in verifying compiler, library, and runtime behaviors as specified in the C++ AMP open specification. DynamicObjectProxy: DOP (Dynamic Object Proxy) é uma biblioteca que permite que qualquer método de qualquer objeto possa ser interceptado através de um proxy dinâmico. Ao interceptar um método, pode-se decorar o objeto, alterando ou recuperando informações sobre o seu comportamento. Extremamente útil para logs, verificações de transações, etc. DOP (Dynamic Object Proxy) is a library that contains classes that makes it possible that any method of any object can be intercepted by a dynamic proxy. By interceptin...EAIP: ???????? Flatland: Artificial life, or A-Life, is a broad and ever emerging field that has found its applications in almost any field: economics, medicine, traffic planning, shopping habits, patterns in music. And it is evident that work with modelling logical life in artificial environments is a necessity for the future software developer. Abbots novella "Flatland: A Romance of Many Dimensions" describes the two dimensional world "Flatland", where life is geometrical shapes that have human-like emotions, but...GameAudioSystem: Simple Audio Game System written with OpenAL to be used with Ogre3D.HyperionSS2P - Simple scan to pdf solution: Simple scan to pdf solution.Issue Impala: Issue Impala is a powerful and elegant issue tracker.KoekyGL Wrapper: A .net wrapper for OpenGL aimed at making it easy to use OpenGL.Marik Sample Project: This is a sample by KitMongoDB Managment Client: Development MongoDB Web client. HTML 5 jQuery. One page web application. When Windows 8 metro is released then Metro style application To.MongoDB.Dynamic: MongoDB.Dynamic is a personal project that I’ve started when I was developing my first application targeting MongoDB as DBMS, using the “official driver” MongoDB.Driver, supported by 10gen. The objective is to provide a lightweight library with some interesting features that speed up development for desktop/web applications that accesses MongoDB databases. MongoDB.Dynamic is oriented to interfaces. You don’t need to create concrete classes of your entities, all you need to do is setup your...My Google Workspace: An easy way to create documents search at Google and read your emails and Much moreqzgfjava: git????，?android??“??”???SP Sticky Notes: SP Sticky Notes allows your users to add sticky notes to a page on your SharePoint site.Weather3: It's Metro Style AppXNA Scumm: This is a rewrite of the ScummVM engine using XNA. ScummVM is an engine that runs old school LucasArts graphical adventure games. It is written completely in C# and the first version will run on PC and Xbox 360. A Windows phone version will probably follow. Of course, you will need to own the original games in order to use it. I will start my work by The Secret of Monkey Island, more specifically the VGA CD version. Monkey Island 2: LeChuck's Revenge and Indiana Jones 4 and Fate of Atl...YoG Community Game: This project is a game, being developed by several members of the Yogscast Community Forums. It is a top-down shooter, based around the protagonist 'Joe', and his adventures through TV shows every day.

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• What should a domain object's validation cover?

  - by MarcoR88

  I'm trying to figure out how to do validation of domain objects that need external resources, such as data mappers/dao Firstly here's my code class User { const INVALID_ID = 1; const INVALID_NAME = 2; const INVALID_EMAIL = 4; int getID(); void setID(Int i); string getName(); void setName(String s); string getEmail(); void setEmail(String s); int getErrorsForInsert(); // returns a bitmask for INVALID_* constants int getErrorsForUpdate(); } My worries are about the uniqueness of the email, checking it would require the storage layer. Reading others' code seems that two solutions are equally accepted: both perform the unique validation in data mapper but some set an error state to the DO user.addError(User.INVALID_EMAIL) while others prefer to throw a totally different type of exception that covers only persistence, like: UserStorageException { const INVALID_EMAIL = 1; const INVALID_CITY = 2; } What are the pros and cons of these solutions?

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• Allowing client to select data to return via REST interface

  - by CMP

  I have a rest service that is essentially a proxy to a variety of other services. So if I call GET /users/{id} It will get their user profile, as well as order history, and contact info, etc... all from various services, and aggregates them into one nice object. My problem is that each call to a different service has the potential to add time to the original request, so we would rather not get ALL the data ALL of the time if a particular client does not care about all of the pieces. A solution I have arrived at is to do something like this: GET /users/{id}?includeOrders=true&includeX=true&includeY=true... That works, and it allow me to do only what I need to, but it is cumbersome. We have added enough different data sources that there are too many parameters for that style to be useful. I could do something similar with a single integer and a bitmask or something, but that only makes it harder to read, and it does not feel very Restful. I could break it down into multiple calls so they would need to call /users/{id}/orders and /users/{id}/profile separately, but that sort of defeats the purpose of an aggregating proxy, who's purpose is to make clients jobs easier. Are there any good patterns that can help me return just enough data for each client, without making it too difficult for them to filter and select what they want?

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• Enum.values() vs EnumSet.allOf( ). Which one is more preferable?

  - by Alexander Pogrebnyak

  I looked under the hood for EnumSet.allOf and it looks very efficient, especially for enums with less than 64 values. Basically all sets share the single array of all possible enum values and the only other piece of information is a bitmask which in case of allOf is set in one swoop. On the other hand Enum.values() seems to be a bit of black magic. Moreover it returns an array, not a collection, so in many cases it must be decorated with Arrays.asList( ) to be usable in any place that expects collection. So, should EnumSet.allOf be more preferable to Enum.values? More specifically, which form of for iterator should be used: for ( final MyEnum val: MyEnum.values( ) ); or for ( final MyEnum val: EnumSet.allOf( MyEnum.values ) );

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• Why is Read-Modify-Write necessary for registers on embedded systems?

  - by Adam Shiemke

  I was reading http://embeddedgurus.com/embedded-bridge/2010/03/different-bit-types-in-different-registers/, which said: With read/write bits, firmware sets and clears bits when needed. It typically first reads the register, modifies the desired bit, then writes the modified value back out and I have run into that consrtuct while maintaining some production code coded by old salt embedded guys here. I don't understand why this is necessary. When I want to set/clear a bit, I always just or/nand with a bitmask. To my mind, this solves any threadsafe problems, since I assume setting (either by assignment or oring with a mask) a register only takes one cycle. On the other hand, if you first read the register, then modify, then write, an interrupt happening between the read and write may result in writing an old value to the register. So why read-modify-write? Is it still necessary?

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• Why is it bad to use boolean flags in databases? And what should be used instead?

  - by David Chanin

  I've been reading through some of guides on database optimization and best practices and a lot of them suggest not using boolean flags at all in the DB schema (ex http://forge.mysql.com/wiki/Top10SQLPerformanceTips). However, they never provide any reason as to why this is bad. Is it a peformance issue? is it hard to index or query properly? Furthermore, if boolean flags are bad, what should you use to store boolean values in a database? Is it better to store boolean flags as an integer and use a bitmask? This seems like it would be less readable.

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• Insriting into a bitstream

  - by evilertoaster

  I'm looking for a way to efficiently insert bits into a bitstream and have it 'overflow', padding with 0's. So for example if you had a byte array with 2 bytes: 231 and 109 (11100111 01101101), and did BitInsert(byteArray,4,00) it would insert two bits at bit offset 4 making 11100001 11011011 01000000 (225,219,24). It would be ok even the method only allowed 1 bit insertions e.g. BitInsert(byteArray,4,true) or BitInsert(byteArray,4,false). I have one method of doing it, but it has to walk the stream with a bitmask bit by bit, so I'm wondering if there's a simpler approach... Answers in assembly or a C derivative would be appreciated.

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• Inserting into a bitstream

  - by evilertoaster

  I'm looking for a way to efficiently insert bits into a bitstream and have it 'overflow', padding with 0's. So for example if you had a byte array with 2 bytes: 231 and 109 (11100111 01101101), and did BitInsert(byteArray,4,00) it would insert two bits at bit offset 4 making 11100001 11011011 01000000 (225,219,24). It would be ok even the method only allowed 1 bit insertions e.g. BitInsert(byteArray,4,true) or BitInsert(byteArray,4,false). I have one method of doing it, but it has to walk the stream with a bitmask bit by bit, so I'm wondering if there's a simpler approach... Answers in assembly or a C derivative would be appreciated.

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• Algorithm for non-contiguous netmask match

  - by Gianluca

  Hi, I have to write a really really fast algorithm to match an IP address to a list of groups, where each group is defined using a notation like 192.168.0.0/252.255.0.255. As you can see, the bitmask can contain zeros even in the middle, so the traditional "longest prefix match" algorithms won't work. If an IP matches two groups, it will be assigned to the group containing most 1's in the netmask. I'm not working with many entries (let's say < 1000) and I don't want to use a data structure requiring a large memory footprint (let's say 1-2 MB), but it really has to be fast (of course I can't afford a linear search). Do you have any suggestion? Thanks guys. UPDATE: I found something quite interesting at http://www.cse.usf.edu/~ligatti/papers/grouper-conf.pdf, but it's still too memory-hungry for my utopic use case

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• Find recipes that can be cooked from provided ingridients

  - by skaurus

  Sorry for bad English :( Suppose i can preliminary organize recipes and ingredients data in any way. How can i effectively conduct search of recipes by user-provided ingredients, preferably sorted by max match - so, first going recipes that use maximum of provided ingridients and do not contain any other ingrs, after them recipes that uses less of provided set and still not any other ingrs, after them recipes with minimum additional requirements and so on? All i can think about is represent recipe ingridients like bitmasks, and compare required bitmask with all recipes, but it is obviously a bad way to go. And related things like Levenstein distance i don't see how to use here. I believe it should be quite common task...

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