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• Git for beginners: The definitive practical guide

  - by Adam Davis

  Ok, after seeing this post by PJ Hyett, I have decided to skip to the end and go with git. So what I need is a beginners practical guide to git. "Beginner" being defined as someone who knows how to handle their compiler, understands to some level what a makefile is, and has touched source control without understanding it very well. "Practical" being defined as this person doesn't want to get into great detail regarding what git is doing in the background, and doesn't even care (or know) that it's distributed. Your answers might hint at the possibilities, but try to aim for the beginner that wants to keep a 'main' repository on a 'server' which is backed up and secure, and treat their local repository as merely a 'client' resource. Procedural note: PLEASE pick one and only one of the below topics and answer it clearly and concisely in any given answer. Don't try to jam a bunch of information into one answer. Don't just link to other resources - cut and paste with attribution if copyright allows, otherwise learn it and explain it in your own words (ie, don't make people leave this page to learn a task). Please comment on, or edit, an already existing answer unless your explanation is very different and you think the community is better served with a different explanation rather than altering the existing explanation. So: Installation/Setup How to install git How do you set up git? Try to cover linux, windows, mac, think 'client/server' mindset. Setup GIT Server with Msysgit on Windows How do you create a new project/repository? How do you configure it to ignore files (.obj, .user, etc) that are not really part of the codebase? Working with the code How do you get the latest code? How do you check out code? How do you commit changes? How do you see what's uncommitted, or the status of your current codebase? How do you destroy unwanted commits? How do you compare two revisions of a file, or your current file and a previous revision? How do you see the history of revisions to a file? How do you handle binary files (visio docs, for instance, or compiler environments)? How do you merge files changed at the "same time"? How do you undo (revert or reset) a commit? Tagging, branching, releases, baselines How do you 'mark' 'tag' or 'release' a particular set of revisions for a particular set of files so you can always pull that one later? How do you pull a particular 'release'? How do you branch? How do you merge branches? How do you resolve conflicts and complete the merge? How do you merge parts of one branch into another branch? What is rebasing? How do I track remote branches? How can I create a branch on a remote repository? Other Describe and link to a good gui, IDE plugin, etc that makes git a non-command line resource, but please list its limitations as well as its good. msysgit - Cross platform, included with git gitk - Cross platform history viewer, included with git gitnub - OS X gitx - OS X history viewer smartgit - Cross platform, commercial, beta tig - console GUI for Linux qgit - GUI for Windows, Linux Any other common tasks a beginner should know? Git Status tells you what you just did, what branch you have, and other useful information How do I work effectively with a subversion repository set as my source control source? Other git beginner's references git guide git book git magic gitcasts github guides git tutorial Progit - book by Scott Chacon Git - SVN Crash Course Delving into git Understanding git conceptually I will go through the entries from time to time and 'tidy' them up so they have a consistent look/feel and it's easy to scan the list - feel free to follow a simple "header - brief explanation - list of instructions - gotchas and extra info" template. I'll also link to the entries from the bullet list above so it's easy to find them later.

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• Streaming a webcam from Silverlight 4 (Beta)

  - by Ken Smith

  The new webcam stuff in Silverlight 4 is darned cool. By exposing it as a brush, it allows scenarios that are way beyond anything that Flash has. At the same time, accessing the webcam locally seems like it's only half the story. Nobody buys a webcam so they can take pictures of themselves and make funny faces out of them. They buy a webcam because they want other people to see the resulting video stream, i.e., they want to stream that video out to the Internet, a lay Skype or any of the dozens of other video chat sites/applications. And so far, I haven't figured out how to do that with It turns out that it's pretty simple to get a hold of the raw (Format32bppArgb formatted) bytestream, as demonstrated here. But unless we want to transmit that raw bytestream to a server (which would chew up way too much bandwidth), we need to encode that in some fashion. And that's more complicated. MS has implemented several codecs in Silverlight, but so far as I can tell, they're all focused on decoding a video stream, not encoding it in the first place. And that's apart from the fact that I can't figure out how to get direct access to, say, the H.264 codec in the first place. There are a ton of open-source codecs (for instance, in the ffmpeg project here), but they're all written in C, and they don't look easy to port to C#. Unless translating 10000+ lines of code that look like this is your idea of fun :-) const int b_xy= h->mb2b_xy[left_xy[i]] + 3; const int b8_xy= h->mb2b8_xy[left_xy[i]] + 1; *(uint32_t*)h->mv_cache[list][cache_idx ]= *(uint32_t*)s->current_picture.motion_val[list][b_xy + h->b_stride*left_block[0+i*2]]; *(uint32_t*)h->mv_cache[list][cache_idx+8]= *(uint32_t*)s->current_picture.motion_val[list][b_xy + h->b_stride*left_block[1+i*2]]; h->ref_cache[list][cache_idx ]= s->current_picture.ref_index[list][b8_xy + h->b8_stride*(left_block[0+i*2]>>1)]; h->ref_cache[list][cache_idx+8]= s->current_picture.ref_index[list][b8_xy + h->b8_stride*(left_block[1+i*2]>>1)]; The mooncodecs folder within the Mono project (here) has several audio codecs in C# (ADPCM and Ogg Vorbis), and one video codec (Dirac), but they all seem to implement just the decode portion of their respective formats, as do the java implementations from which they were ported. I found a C# codec for Ogg Theora (csTheora, http://www.wreckedgames.com/forum/index.php?topic=1053.0), but again, it's decode only, as is the jheora codec on which it's based. Of course, it would presumably be easier to port a codec from Java than from C or C++, but the only java video codecs that I found were decode-only (such as jheora, or jirac). So I'm kinda back at square one. It looks like our options for hooking up a webcam (or microphone) through Silverlight to the Internet are: (1) Wait for Microsoft to provide some guidance on this; (2) Spend the brain cycles porting one of the C or C++ codecs over to Silverlight-compatible C#; (3) Send the raw, uncompressed bytestream up to a server (or perhaps compressed slightly with something like zlib), and then encode it server-side; or (4) Wait for someone smarter than me to figure this out and provide a solution. Does anybody else have any better guidance? Have I missed something that's just blindingly obvious to everyone else? (For instance, does Silverlight 4 somewhere have some classes I've missed that take care of this?)

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• Hyper-V File Server Clustering - at my wit’s end

  - by René Kåbis

  I am at my wit’s end with File Server clustering under Hyper-V. I am hoping that someone might be able to help me figure out this Gordian Knot of a technology that seems to have dead ends (like forcing cluster VMs to use iSCSI drives where normally-attached VHDX drives could suffice) where logic and reason would normally provide a logical solution. My hardware: I will be running three servers (in the end), but right now everything is taking place on one server. One of the secondary servers will exist purely as a witness/quorum, and another slightly more powerful one will be acting as an emergency backup (with additional storage, just not redundant) to hold the secondary AD VM and the other halves of a set of clustered VMs: the SQL VM and the file system VM. Please note, these each are the depreciated nodes of a cluster, the main nodes will be on the most powerful first machine. My heavy lifter is a machine that also contains all of the truly redundant storage on the network. If this gives anyone the heebie-geebies, too bad. It has a 6TB (usable) RAID-10 array, and will (in the end) hold the primary nodes of both aforementioned clusters, but is right now holding all VMs. This is, right now: DC01, DC02, SQL01, SQL02, FS01 & FS02. Eventually, I will be adding additional VMs to handle Exchange, Sharepoint and Lync, but only to this main server (the secondary server won't be able to handle more than three or four VMs, so why burden it? The AD, SQL & FS VMs are the most critical for the business). If anyone is now saying, “wait, what about a SAN or a NAS for the file servers?”, well too bad. What exists on the main machine is what I have to deal with. I followed these instructions, but I seem to be unable to get things to work. In order to make the file server truly redundant, I cannot trust any one machine to hold the only data store on the network. Therefore, I have created a set of iSCSI drives on the VM-host of the main machine, and attached one to each file server VM. The end result is that I want my FS01 to sit on the heavy lifter, along with its iSCSI “drive”, and FS02 will sit on the secondary machine with its own iSCSI “drive” there as well. That is, neither iSCSI drive will end up sitting on the same machine as the other. As such, the clustered FS will utterly duplicate the contents of the iSCSI drives between each other, so that if one physical machine (or the FS VM) goes toes-up, the other has got a full copy of the data on its own iSCSI drive. My problem occurs when I try to apply the file server role within the failover cluster manager. Actually, it is even before that -- it occurs when adding the disks. Since I have added each disk preferentially to a specific VM (by limiting the initiator by DNS hostname, and by adding two-way CHAP authentication), this forces each VM to be in control of its own iSCSI disk. However, when I try to add the disks to the Disks section of Storage within Failover Cluster Manager, the entire process fails for a random disk of the pair. That is, one will get online, but the other will remain offline because it does not have the correct “owner node”. I mean, really -- WTF? Of course it doesn’t have the right owner node, both drives are showing the same node name!! I cannot seem to have one drive show up with one node name as owner, and the other drive show up with the other node name as owner. And because both drives are not “online”, I cannot create a pool to apply to a cluster role. Talk about getting stuck between a rock and a hard place! I’ve got more to add, but my work is closing for the day and I have to wrap things up. I will try to add more tomorrow morning when I get in. My main objective is to have a file server VM on each machine, the storage on each machine, but a transparent failover in case one physical machine fails. Essentially, a failover FS that doesn’t care which machine fails -- the storage contents are replicated equally on each machine. Am I even heading in the right direction?

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• Multiple "pages" in GWT with human friendly URLs

  - by Andreas Borglin

  Hi. I'm playing with a GWT/GAE project which will have three different "pages", although it is not really pages in a GWT sense. The top views (one for each page) will have completely different layouts, but some of the widgets will be shared. One of the pages is the main page which is loaded by the default url (http://www.site.com), but the other two needs additional URL information to differentiate the page type. They also need a name parameter, (like http://www.site.com/project/project-name. There are at least two solutions to this that I'm aware of. Use GWT history mechanism and let page type and parameters (such as project name) be part of the history token. Use servlets with url-mapping patterns (like /project/*) The first choice might seem obvious at first, but it has several drawbacks. First, a user should be able to easily remember and type URL directly to a project. It is hard to produce a human friendly URL with history tokens. Second, I'm using gwt-presenter and this approach would mean that we need to support subplaces in one token, which I'd rather avoid. Third, a user will typically stay at one page, so it makes more sense that the page information is part of the "static" URL. Using servlets solves all these problems, but also creates other ones. So my first questions is, what is the best solution here? If I would go for the servlet solution, new questions pop up. It might make sense to split the GWT app into three separate modules, each with an entry point. Each servlet that is mapped to a certain page would then simply forward the request to the GWT module that handles that page. Since a user typically stays at one page, the browser only needs to load the js for that page. Based on what I've read, this solution is not really recommended. I could also stick with one module, but then GWT needs to find out which page it should display. It could either query the server or parse the URL itself. If I stick with one GWT module, I need to keep the page information stored on server side. Naturally I thought about sessions, but I'm not sure if its a good idea to mix page information with user data. A session usually lives between user login and logout, but in this case it would need different behavior. Would it be bad practise to handle this via sessions? The one GWT module + servlet solution also leads to another problem. If a user goes from a project page to the main page, how will GWT know that this has happened? The app will not be reloaded, so it will be treated as a simple state change. It seems rather ineffecient to have to check page info for every state change. Anyone care to guide me out of the foggy darkness that surrounds me? :-)

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• Architecture for a business objects / database access layer

  - by gregmac

  For various reasons, we are writing a new business objects/data storage library. One of the requirements of this layer is to separate the logic of the business rules, and the actual data storage layer. It is possible to have multiple data storage layers that implement access to the same object - for example, a main "database" data storage source that implements most objects, and another "ldap" source that implements a User object. In this scenario, User can optionally come from an LDAP source, perhaps with slightly different functionality (eg, not possible to save/update the User object), but otherwise it is used by the application the same way. Another data storage type might be a web service, or an external database. There are two main ways we are looking at implementing this, and me and a co-worker disagree on a fundamental level which is correct. I'd like some advice on which one is the best to use. I'll try to keep my descriptions of each as neutral as possible, as I'm looking for some objective view points here. Business objects are base classes, and data storage objects inherit business objects. Client code deals with data storage objects. In this case, common business rules are inherited by each data storage object, and it is the data storage objects that are directly used by the client code. This has the implication that client code determines which data storage method to use for a given object, because it has to explicitly declare an instance to that type of object. Client code needs to explicitly know connection information for each data storage type it is using. If a data storage layer implements different functionality for a given object, client code explicitly knows about it at compile time because the object looks different. If the data storage method is changed, client code has to be updated. Business objects encapsulate data storage objects. In this case, business objects are directly used by client application. Client application passes along base connection information to business layer. Decision about which data storage method a given object uses is made by business object code. Connection information would be a chunk of data taken from a config file (client app does not really know/care about details of it), which may be a single connection string for a database, or several pieces connection strings for various data storage types. Additional data storage connection types could also be read from another spot - eg, a configuration table in a database that specifies URLs to various web services. The benefit here is that if a new data storage method is added to an existing object, a configuration setting can be set at runtime to determine which method to use, and it is completely transparent to the client applications. Client apps do not need to be modified if data storage method for a given object changes. Business objects are base classes, data source objects inherit from business objects. Client code deals primarily with base classes. This is similar to the first method, but client code declares variables of the base business object types, and Load()/Create()/etc static methods on the business objects return the appropriate data source-typed objects. The architecture of this solution is similar to the first method, but the main difference is the decision about which data storage object to use for a given business object is made by the business layer, not the client code. I know there are already existing ORM libraries that provide some of this functionality, but please discount those for now (there is the possibility that a data storage layer is implemented with one of these ORM libraries) - also note I'm deliberately not telling you what language is being used here, other than that it is strongly typed. I'm looking for some general advice here on which method is better to use (or feel free to suggest something else), and why.

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• What are ProductCode & UpgradeCode & GUID? How to detect if certain application/library is already i

  - by claws

  I've already gone through: http://stackoverflow.com/questions/211192/check-if-the-application-is-already-installed http://stackoverflow.com/questions/488717/detecting-if-a-program-is-already-installed-with-nsis http://nsis.sourceforge.net/Add_uninstall_information_to_Add/Remove_Programs My questions are little more in depth and little more general. So, as you understood my problem is that I want to check if "Certain Applications" are already installed on the user's machine? I'm generating the installer using Advanced Installer. First few questions: What is Upgrade Code? Advanced installer has option, Product Version (identify by Upgrade Code) What is Product Code? Advanced installer Product Version (identify by Product Code) Component is installed : GUID. What is GUID? All the above three has values like this: {49EB7A6A-1CEF-4A1E-9E89-B9A4993963E3} I don't know what these values are but it seems that computer is recognizing software using this kind of strange ID. My required applications are MySQL DBMS MySQL .NET Connector One fact that I discovered is Upgrade Code & Product Code can be extracted from its "msi installer". MySQL Server Installer = mysql-5.1.43-win32.msi Upgrade Code = {49EB7A6A-1CEF-4A1E-9E89-B9A4993963E3} Product Code = {0ECED7D8-FF53-4DC9-958E-C2177F528DE4} GUID (for component Installed) = ???? Uninstall Path = HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{0ECED7D8-FF53-4DC9-958E-C2177F528DE4} Installer = mysql-5.1.46-win32.msi Upgrade Code = {49EB7A6A-1CEF-4A1E-9E89-B9A4993963E3} Product Code = {EA8FDE5A-2B33-4EDD-B7E7-8D179DF731A5} GUID (for component Installed) = ???? Uninstall Path = HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{EA8FDE5A-2B33-4EDD-B7E7-8D179DF731A5} Installer = mysql-essential-5.1.46-win32.msi Upgrade Code = {49EB7A6A-1CEF-4A1E-9E89-B9A4993963E3} Product Code = {AD33AF2C-6485-4106-B012-1D9CDC88A454} GUID (for component Installed) = ???? Uninstall Path = HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{AD33AF2C-6485-4106-B012-1D9CDC88A454} Installer = mysql-essential-5.1.46-win32.msi Upgrade Code = {49EB7A6A-1CEF-4A1E-9E89-B9A4993963E3} Product Code = {9A4DA7EF-A7B9-4282-90AD-10976AA24E69} GUID (for component Installed) = ???? Uninstall Path = HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{9A4DA7EF-A7B9-4282-90AD-10976AA24E69} Observation from above data: UpgradeCode of a software is constant & is irrespective of its version. ProductCode is version specific & it is used by the MSI internally which is actually reasonable because. MSI allows applications of different versions to be installed side by side. I don't know how to find GUID. MySQL ADO .NET Driver Installer = mysql.data.5.2.5.msi Upgrade Code = --- Product Code = {5FD88490-011C-4DF1-B886-F298D955171B} GUID (for component Installed) = ???? Installer = mysql.data.6.2.2.msi Upgrade Code = --- Product Code = {5FD88490-011C-4DF1-B886-F298D955171B} GUID (for component Installed) = ???? UninstallPath =HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{5FD88490-011C-4DF1-B886-F298D955171B} Installer = mysql.data.6.2.3.msi Upgrade Code = --- Product Code = {5FD88490-011C-4DF1-B886-F298D955171B} GUID (for component Installed) = ???? Observations from above data: - surprisingly, it couldn't find UpgradeCode from installer of mysql.data.*.msi. I wonder why? This contradicts with my above observation. - ProductCode for all different versions is same here. This again contradicts my above observations. -I still don't know how to find GUID. Now, What exactly are these ProductCode & UpgradeCode & GUID. Which denotes what? Why are above observations contradicting? I don't care about versions. I don't want to depend on Application Name then how do I check if MySQL driver & MySQL ADO .NET. Does detection become simple if they are .NET assemblies? How to do then? I don't want to ship the assemblies with my deployed files.

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• nsdata to nsstring to nsdata

  - by Jayshree

  Hello everybody. I am calling the webservices. The web service returns data in xml format. Now the problem is the xml data is not being received in proper format. In place of "<", "" it returns in html format like-(<) and (>) . So i assigned the xmldata to a NsMutableString and replaced the escape characters so that the format of xml data is proper. Then i reassigned the NSMutableString to NSData so that i can parse the tags. but the problem is the xmlparser stops right where the xml data is. Where i replaced the tags. it doesnt go further. can anybody make me understand what is going on???? This is the xml response from webservice that i called. <?xml version="1.0" encoding="ISO-8859-1"?><SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/"> <SOAP-ENV:Body> <ns1:GetCustomerInfoResponse xmlns:ns1="http://aa.somewebservice.com/phpwebservice"> <return xsi:type="xsd:string"> &lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;&lt;customer&gt;&lt;id&gt;1&lt;/id&gt;&lt;customername&gt;Hitesh&lt;/customername&gt;&lt;phonenumber&gt;98989898&lt;/phonenumber&gt;&lt;/customer&gt; </return> </ns1:GetCustomerInfoResponse> </SOAP-ENV:Body> </SOAP-ENV:Envelope> And this is after i replaced the tags. <?xml version="1.0" encoding="ISO-8859-1"?><SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/"> <SOAP-ENV:Body> <ns1:GetCustomerInfoResponse xmlns:ns1="http://a.somewebservice.com/phpwebservice"> <return xsi:type="xsd:string"> <?xml version="1.0" encoding="utf-8"?> <customer><id>1</id><customername>Hitesh</customername><phonenumber>98989898</phonenumber></customer> </return> </ns1:GetCustomerInfoResponse> </SOAP-ENV:Body></SOAP-ENV:Envelope> Now the problem is while parsing the parser only goes upto return tag. And then it is stuck there. It doesnt go any further. So wat do i do? anybody care to help me?

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• Struts 2 TypeConversion problem

  - by Parhs

  Hello... i have a big problem... i have this map HashMap<Long, String> examValues; It gets populated by textboxes automatically with name="examValues[id]" Although i explicily defined the element as String , it doesnt care!!! I want everything to be a String... The result is to get a java.lang.ClassCastException: java.lang.Long cannot be cast to java.lang.String when i try to System.out.print(examValues.get(examValue.getExam().getId()).getClass().getName()); INFO: java.lang.ClassCastException: java.lang.Long cannot be cast to java.lang.String at gr.medilab.logic.action.exams.Exams.fill_edit(Exams.java:204) at gr.medilab.logic.action.exams.Exams.fill(Exams.java:95) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:441) at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:280) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:243) at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:165) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:252) at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:122) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:179) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) at org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:94) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:235) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:89) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:130) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:267) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:126) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:138) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:165) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:179) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:176) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52) at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:488) at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77) at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:256) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:215) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:277) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:188) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:641) at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:97) at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:85) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:185) at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:332) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:233) at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:165) at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:791) at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:693) at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:954) at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:170) at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:135) at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:102) at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:88) at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:76) at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:53) at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:57) at com.sun.grizzly.ContextTask.run(ContextTask.java:69) at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:330) at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:309) at java.lang.Thread.run(Thread.java:619) Any idea?

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• Oracle data warehouse design - fact table acting as a dimension?

  - by Elizabeth

  THANKS: Both answers here are very helpful, but I could only pick one. I really appreciate the advice! our datawarehouse will be used more for workflow reports than traditional analytical reports. Our users care about "current picture" far more than history. (though history matters, too.) We are a government entity that does not have costs or related calculations. Mostly just counts of people within given locations and with related history. We are using Oracle, and I have found distinct advantage in using the star join whenever possible and would like to rearchitect everything to as closely resemble the star schema as is reasonable for our business uses. Speed in this DW is vital, and a number of tests have already proven the star schema approach to me. Our "person" table is key - it contains over 4 million records and will be the most frequently used source in queries. It can be seen at the center of a star with multiple dimensions (like age, gender, affiliation, location, etc.). It is a very LONG table, particularly when I join it to the address and contact information. However, it is more like a dimension table when we start looking at history. For example, there are two different history tables that have a person key pointing to the person table. One has over 20 million records and the other has almost 50 million and grows daily. Is this table a fact table or a dimension table? Can one work as both? If so, is that going to be a big performance problem? Is it common to query more off of a dimension than a fact? What happens if a DIFFERENT fact table that uses the person table as a dimension is actually only 60,000 records (much smaller.). I think my problem is that our data and use of it does not fit with the commonly use examples of star schemas. CLARIFICATION: Some good thoughts have been added below, but perhaps I left too much out to really explain well. Here's some more info: We handle a voter database. We don't have any measures except voter counts by various groups: voter counts by party, by age, by location; voter counts by ballot type and election, by ballot status and election, etc. We do have a "voting history" log as well as an activity audit log (change of address, party, etc.). We have information on which voters are election workers and all that related information. I figure I'll get to the peripheral stuff later. For now I'm focusing on our two major "business processes": voter registration(which IS a voter.) and election turnout. In the first, voter is a fact. In the second, voter is a dimension, along with party, election, and type of ballot. (and in case anyone is worried - no we don't know HOW people vote. Just that they do. LOL ) I hope that clarifies things a bit.

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• SQLAlchemy session management in long-running process

  - by codeape

  Scenario: A .NET-based application server (Wonderware IAS/System Platform) hosts automation objects that communicate with various equipment on the factory floor. CPython is hosted inside this application server (using Python for .NET). The automation objects have scripting functionality built-in (using a custom, .NET-based language). These scripts call Python functions. The Python functions are part of a system to track Work-In-Progress on the factory floor. The purpose of the system is to track the produced widgets along the process, ensure that the widgets go through the process in the correct order, and check that certain conditions are met along the process. The widget production history and widget state is stored in a relational database, this is where SQLAlchemy plays its part. For example, when a widget passes a scanner, the automation software triggers the following script (written in the application server's custom scripting language): ' wiget_id and scanner_id provided by automation object ' ExecFunction() takes care of calling a CPython function retval = ExecFunction("WidgetScanned", widget_id, scanner_id); ' if the python function raises an Exception, ErrorOccured will be true ' in this case, any errors should cause the production line to stop. if (retval.ErrorOccured) then ProductionLine.Running = False; InformationBoard.DisplayText = "ERROR: " + retval.Exception.Message; InformationBoard.SoundAlarm = True end if; The script calls the WidgetScanned python function: # pywip/functions.py from pywip.database import session from pywip.model import Widget, WidgetHistoryItem from pywip import validation, StatusMessage from datetime import datetime def WidgetScanned(widget_id, scanner_id): widget = session.query(Widget).get(widget_id) validation.validate_widget_passed_scanner(widget, scanner) # raises exception on error widget.history.append(WidgetHistoryItem(timestamp=datetime.now(), action=u"SCANNED", scanner_id=scanner_id)) widget.last_scanner = scanner_id widget.last_update = datetime.now() return StatusMessage("OK") # ... there are a dozen similar functions My question is: How do I best manage SQLAlchemy sessions in this scenario? The application server is a long-running process, typically running months between restarts. The application server is single-threaded. Currently, I do it the following way: I apply a decorator to the functions I make avaliable to the application server: # pywip/iasfunctions.py from pywip import functions def ias_session_handling(func): def _ias_session_handling(*args, **kwargs): try: retval = func(*args, **kwargs) session.commit() return retval except: session.rollback() raise return _ias_session_handling # ... actually I populate this module with decorated versions of all the functions in pywip.functions dynamically WidgetScanned = ias_session_handling(functions.WidgetScanned) Question: Is the decorator above suitable for handling sessions in a long-running process? Should I call session.remove()? The SQLAlchemy session object is a scoped session: # pywip/database.py from sqlalchemy.orm import scoped_session, sessionmaker session = scoped_session(sessionmaker()) I want to keep the session management out of the basic functions. For two reasons: There is another family of functions, sequence functions. The sequence functions call several of the basic functions. One sequence function should equal one database transaction. I need to be able to use the library from other environments. a) From a TurboGears web application. In that case, session management is done by TurboGears. b) From an IPython shell. In that case, commit/rollback will be explicit. (I am truly sorry for the long question. But I felt I needed to explain the scenario. Perhaps not necessary?)

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• arp problems with transparent bridge on linux

  - by Mink

  I've been trying to secure my virtual machines on my esx server by putting them behind a transparent bridge with 2 interfaces, one in front, one at the back. My intention is to put all the firewall rules in one place (instead of on each virtual server). I've been using as bridge a blank new virtual machine based on arch linux (but I suspect it doesn't matter which brand of linux it is). What I have is 2 virtual switchs (thus two Virtual Network, VN_front and VN_back), each with 2 types of ports (switched/separated or promiscious/where the machine can see all packets). On my bridge machine, I've set up 2 virtual NIC, one on VN_front, one on VN_back, both in promisc mode. I've created a bridge br0 with both NIC in it: brctl addbr br0 brctl stp br0 off brctl addif br0 front_if brctl addif br0 back_if Then brought them up: ifconfig front_if 0.0.0.0 promisc ifconfig back_if 0.0.0.0 promisc ifconfig br0 0.0.0.0 (I use promisc mode, because I'm not sure I can do without, thinking that maybe the packets don't reach the NICs) Then I took one of my virtual server sitting on VN_front, and plugged it to VN_back instead (that's the nifty use case I'm thinking about, being able to move my servers around just by changing the VN they are plugged into, without changing anything in the configuration). Then I looked into the macs "seen" by my addressless bridge using brctl showmacs br0 and it did show my server from both sides: I get something that looks like this : port no mac addr is local? ageing timer 2 00:0c:29:e1:54:75 no 9.27 1 00:0c:29:fd:86:0c no 9.27 2 00:50:56:90:05:86 no 73.38 1 00:50:56:90:05:88 no 0.10 2 00:50:56:90:05:8b yes 0.00 << FRONT VN 1 00:50:56:90:05:8c yes 0.00 << BACK VN 2 00:50:56:90:19:18 no 13.55 2 00:50:56:90:3c:cf no 13.57 the thing is that the server that are plugged in front/back are not shown on the correct port. I suspect some horrible thing happening in the ARP-world... :-/ If I ping from a front virtual server to a back virtual server, I can only see the back machine if that back machine pings something in the front. As soon as I stop the ping from the back machine, the ping from the front machine stops getting through... I've noticed that if the back machine pings, then its port on the bridge is the correct one... I've tried to play with the arp_ switch of /proc/sys, but with no clear effect on the end result... /proc/sys/net/ipv4/ip_forward doesn't seem to be of any use when using a bridge (seems it's all taken care of by brctl) /proc/sys/net/ipv4/conf//arp_ don't seem to change much either... (tried arp_announce to 2 or 8 - like suggested elsewhere - and arp_ignore to 0 or 1 ) All the examples I've seen have a different subnet on either side like 10.0.1.0/24 and 10.0.2.0/24... In my case I want 10.0.1.0/24 on both side (just like a transparent switch - except it's a hidden fw ). Turning stp on/off doesn't seem to have any impact on my issue. It's as if the arp packets where getting through the bridge, corrupting the other side with false data... I've tried to use the -arp on each interface, br0, front, back... it breaks the thing altogether... I suspect it has something to do with both side being on the same subnet... I've thought about putting all my machine behind the fw, so as to have all the same subnet at the back... but I'm stuck with my provider's gateway standing at the front with part of my subnet (in fact 3 appliance to route the whole subnet), so I'll always have ips from the same subnet on both side, whatever I do... (I'm using fixed front IPs on my delegated subnet). I'm at a loss... -_-'' Thx for your help. (As anyone tried something like this? from within ESXi?) (It's not just a stunt, the idea is to have something like fail2ban running on some servers, sending their banned IP to the bridge/fw so that it too could ban them - saving all the other servers from that same attacker in one go, allowing for some honeypot that would trigger the fw from any kind of suitable response, and stuffs of the sort... I am aware I could use something like snort, but it addresses some completely different kind of problems, in a completely different way... )

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• 500 Internal Server Error with PHP application

  - by James

  I have written a PHP application using Windows and XAMPP. I've been trying to run it on Ubuntu 10.10 with Lighttpd 1.4.26. Parts of the application work fine, but whenever I try to log in, I get a 500 - Internal Server Error page. The only thing that shows up in /var/log/lighttpd/error.log is 2011-02-25 13:43:13: (mod_fastcgi.c.2582) unexpected end-of-file (perhaps the fastcgi process died): pid: 1169 socket: unix:/tmp/php.socket-0 2011-02-25 13:43:13: (mod_fastcgi.c.3367) response not received, request sent: 1596 on socket: unix:/tmp/php.socket-0 for /~denton/customer-facing-portal/index.php?, closing connection If I had any output whatsoever from PHP, this would be a lot easier to debug. Any ideas on how to get some? Here is my /etc/lighttpd/lighttpd.conf file: # Debian lighttpd configuration file # ############ Options you really have to take care of #################### ## modules to load server.modules = ( "mod_alias", "mod_compress", # "mod_rewrite", # "mod_redirect", # "mod_usertrack", # "mod_expire", # "mod_flv_streaming", # "mod_evasive", "mod_setenv" ) ## a static document-root, for virtual-hosting take look at the ## server.virtual-* options server.document-root = "/var/www/" ## where to upload files to, purged daily. server.upload-dirs = ( "/var/cache/lighttpd/uploads" ) ## where to send error-messages to server.errorlog = "/var/log/lighttpd/error.log" ## files to check for if .../ is requested index-file.names = ( "index.php", "index.html", "index.htm", "default.htm", "index.lighttpd.html" ) ## Use the "Content-Type" extended attribute to obtain mime type if possible # mimetype.use-xattr = "enable" ## # which extensions should not be handle via static-file transfer # # .php, .pl, .fcgi are most often handled by mod_fastcgi or mod_cgi static-file.exclude-extensions = ( ".php", ".pl", ".fcgi" ) ######### Options that are good to be but not neccesary to be changed ####### ## Use ipv6 only if available. (disabled for while, check #560837) #include_shell "/usr/share/lighttpd/use-ipv6.pl" ## bind to port (default: 80) # server.port = 81 ## bind to localhost only (default: all interfaces) ## server.bind = "localhost" ## error-handler for status 404 #server.error-handler-404 = "/error-handler.html" #server.error-handler-404 = "/error-handler.php" ## to help the rc.scripts server.pid-file = "/var/run/lighttpd.pid" ## ## Format: <errorfile-prefix><status>.html ## -> ..../status-404.html for 'File not found' #server.errorfile-prefix = "/var/www/" ## virtual directory listings dir-listing.encoding = "utf-8" server.dir-listing = "enable" ### only root can use these options # # chroot() to directory (default: no chroot() ) #server.chroot = "/" ## change uid to <uid> (default: don't change) server.username = "www-data" ## change gid to <gid> (default: don't change) server.groupname = "www-data" #### compress module compress.cache-dir = "/var/cache/lighttpd/compress/" compress.filetype = ("text/plain", "text/html", "application/x-javascript", "text/css") #### url handling modules (rewrite, redirect, access) # url.rewrite = ( "^/$" => "/server-status" ) # url.redirect = ( "^/wishlist/(.+)" => "http://www.123.org/$1" ) #### expire module # expire.url = ( "/buggy/" => "access 2 hours", "/asdhas/" => "access plus 1 seconds 2 minutes") #### external configuration files ## mimetype mapping include_shell "/usr/share/lighttpd/create-mime.assign.pl" ## load enabled configuration files, ## read /etc/lighttpd/conf-available/README first include_shell "/usr/share/lighttpd/include-conf-enabled.pl" ## Set environment variables setenv.add-environment = ( "DB_URL__DEMO" => "192.168.1.231", "DB_NAME_DEMO" => "demo", "DB_USER_DEMO" => "user", "DB_PASS_DEMO" => "password", "DB_AGENCY_DEMO" => "demo" ) Here is my /etc/php5/cgi/php.ini file (sans 1641 lines of comments): [PHP] register_long_arrays = Off short_open_tag = Off engine = On short_open_tag = Off asp_tags = Off precision = 14 y2k_compliance = On output_buffering = 4096 zlib.output_compression = Off implicit_flush = Off unserialize_callback_func = serialize_precision = 100 allow_call_time_pass_reference = Off safe_mode = Off safe_mode_gid = Off safe_mode_include_dir = safe_mode_exec_dir = safe_mode_allowed_env_vars = PHP_ safe_mode_protected_env_vars = LD_LIBRARY_PATH disable_functions = disable_classes = expose_php = On max_execution_time = 30 max_input_time = 60 memory_limit = 128M error_reporting = E_ALL & ~E_DEPRECATED & ~E_STRICT display_errors = On display_startup_errors = On log_errors = On log_errors_max_len = 1024 ignore_repeated_errors = Off ignore_repeated_source = Off report_memleaks = On track_errors = On html_errors = On variables_order = "GPCS" request_order = "GP" register_globals = Off register_long_arrays = Off register_argc_argv = Off auto_globals_jit = On post_max_size = 8M magic_quotes_gpc = Off magic_quotes_runtime = Off magic_quotes_sybase = Off auto_prepend_file = auto_append_file = default_mimetype = "text/html" doc_root = user_dir = enable_dl = Off cgi.fix_pathinfo=1 file_uploads = On upload_max_filesize = 2M max_file_uploads = 20 allow_url_fopen = On allow_url_include = Off default_socket_timeout = 60 [Date] date.timezone = "America/Chicago" [filter] [iconv] [intl] [sqlite] [sqlite3] [Pcre] [Pdo] [Pdo_mysql] pdo_mysql.cache_size = 2000 pdo_mysql.default_socket= [Phar] [Syslog] define_syslog_variables = Off [mail function] SMTP = localhost smtp_port = 25 mail.add_x_header = On [SQL] sql.safe_mode = Off [ODBC] odbc.allow_persistent = On odbc.check_persistent = On odbc.max_persistent = -1 odbc.max_links = -1 odbc.defaultlrl = 4096 odbc.defaultbinmode = 1 [Interbase] ibase.allow_persistent = 1 ibase.max_persistent = -1 ibase.max_links = -1 ibase.timestampformat = "%Y-%m-%d %H:%M:%S" ibase.dateformat = "%Y-%m-%d" ibase.timeformat = "%H:%M:%S" [MySQL] mysql.allow_local_infile = On mysql.allow_persistent = On mysql.cache_size = 2000 mysql.max_persistent = -1 mysql.max_links = -1 mysql.default_port = mysql.default_socket = mysql.default_host = mysql.default_user = mysql.default_password = mysql.connect_timeout = 60 mysql.trace_mode = Off [MySQLi] mysqli.max_persistent = -1 mysqli.allow_persistent = On mysqli.max_links = -1 mysqli.cache_size = 2000 mysqli.default_port = 3306 mysqli.default_socket = mysqli.default_host = mysqli.default_user = mysqli.default_pw = mysqli.reconnect = Off [mysqlnd] mysqlnd.collect_statistics = On mysqlnd.collect_memory_statistics = Off [OCI8] [PostgresSQL] pgsql.allow_persistent = On pgsql.auto_reset_persistent = Off pgsql.max_persistent = -1 pgsql.max_links = -1 pgsql.ignore_notice = 0 pgsql.log_notice = 0 [Sybase-CT] sybct.allow_persistent = On sybct.max_persistent = -1 sybct.max_links = -1 sybct.min_server_severity = 10 sybct.min_client_severity = 10 [bcmath] bcmath.scale = 0 [browscap] [Session] session.save_handler = files session.use_cookies = 1 session.use_only_cookies = 1 session.name = PHPSESSID session.auto_start = 0 session.cookie_lifetime = 0 session.cookie_path = / session.cookie_domain = session.cookie_httponly = session.serialize_handler = php session.gc_probability = 1 session.gc_divisor = 1000 session.gc_maxlifetime = 1440 session.bug_compat_42 = Off session.bug_compat_warn = Off session.referer_check = session.entropy_length = 0 session.cache_limiter = nocache session.cache_expire = 180 session.use_trans_sid = 0 session.hash_function = 0 session.hash_bits_per_character = 5 url_rewriter.tags = "a=href,area=href,frame=src,input=src,form=fakeentry" [MSSQL] mssql.allow_persistent = On mssql.max_persistent = -1 mssql.max_links = -1 mssql.min_error_severity = 10 mssql.min_message_severity = 10 mssql.compatability_mode = Off mssql.secure_connection = Off [Assertion] [COM] [mbstring] [gd] [exif] [Tidy] tidy.clean_output = Off [soap] soap.wsdl_cache_enabled=1 soap.wsdl_cache_dir="/tmp" soap.wsdl_cache_ttl=86400 soap.wsdl_cache_limit = 5 [sysvshm] [ldap] ldap.max_links = -1 [mcrypt] [dba] Update: here is /etc/lighttpd/conf-enabled/15-fastcgi-php.conf As far as I know, it's just the default config file the Ubuntu package installed. ## FastCGI programs have the same functionality as CGI programs, ## but are considerably faster through lower interpreter startup ## time and socketed communication ## ## Documentation: /usr/share/doc/lighttpd-doc/fastcgi.txt.gz ## http://redmine.lighttpd.net/projects/lighttpd/wiki/Docs:ConfigurationOptions#mod_fastcgi-fastcgi ## Start an FastCGI server for php (needs the php5-cgi package) fastcgi.server += ( ".php" => (( "bin-path" => "/usr/bin/php-cgi", "socket" => "/tmp/php.socket", "max-procs" => 1, "idle-timeout" => 20, "bin-environment" => ( "PHP_FCGI_CHILDREN" => "4", "PHP_FCGI_MAX_REQUESTS" => "10000" ), "bin-copy-environment" => ( "PATH", "SHELL", "USER" ), "broken-scriptfilename" => "enable" )) )

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• What is the coolest thing you can do in <10 lines of simple code? Help me inspire beginners!

  - by Tom Ritter

  I'm looking for the coolest thing you can do in a few lines of simple code. I'm sure you can write a Mandelbrot set in Haskell in 15 lines but it's difficult to follow. My goal is to inspire students that programming is cool. We know that programming is cool because you can create anything you imagine - it's the ultimate creative outlet. I want to inspire these beginners and get them over as many early-learning humps as I can. Now, my reasons are selfish. I'm teaching an Intro to Computing course to a group of 60 half-engineering, half business majors; all freshmen. They are the students who came from underprivileged High schools. From my past experience, the group is generally split as follows: a few rock-stars, some who try very hard and kind of get it, the few who try very hard and barely get it, and the few who don't care. I want to reach as many of these groups as effectively as I can. Here's an example of how I'd use a computer program to teach: Here's an example of what I'm looking for: a 1-line VBS script to get your computer to talk to you: CreateObject("sapi.spvoice").Speak InputBox("Enter your text","Talk it") I could use this to demonstrate order of operations. I'd show the code, let them play with it, then explain that There's a lot going on in that line, but the computer can make sense of it, because it knows the rules. Then I'd show them something like this: 4(5*5) / 10 + 9(.25 + .75) And you can see that first I need to do is (5*5). Then I can multiply for 4. And now I've created the Object. Dividing by 10 is the same as calling Speak - I can't Speak before I have an object, and I can't divide before I have 100. Then on the other side I first create an InputBox with some instructions for how to display it. When I hit enter on the input box it evaluates or "returns" whatever I entered. (Hint: 'oooooo' makes a funny sound) So when I say Speak, the right side is what to Speak. And I get that from the InputBox. So when you do several things on a line, like: x = 14 + y; You need to be aware of the order of things. First we add 14 and y. Then we put the result (what it evaluates to, or returns) into x. That's my goal, to have a bunch of these cool examples to demonstrate and teach the class while they have fun. I tried this example on my roommate and while I may not use this as the first lesson, she liked it and learned something. Some cool mathematica programs that make beautiful graphs or shapes that are easy to understand would be good ideas and I'm going to look into those. Here are some complicated actionscript examples but that's a bit too advanced and I can't teach flash. What other ideas do you have?

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• NSMutableString leaks on append or replaceOccurrencesOfString

  - by John

  Hello Folks, I know similar questions have been asked time and time again but I ask that you please bear with me as I cannot seem to find an answer that helps. My application has leaks that are driving me out of my mind. Actually, they are not reported as leaks using Leaks, but my net bytes in ObjectAlloc goes up and up and up and never stops, eventually leading to a crash if it goes on long enough (not very long). The problem occurs with NSMutableStrings. I think there is either something fundamental I don't understand about them, or I am facing another problem that I am having difficulty tracking down but keeps hiding behind the NSMutableStrings. Specifically, I am noticing that whenever I append to or perform a replace on a NSMutableString, ObjectAlloc reports what appear to be mismatches in malloc/frees behind the scene when resizing the NSMutableString. I'm sorry to say this is the second time I'm facing this problem - the first time I messed around for hours and hours and finally the problem went away (magic!) but I don't really know why. When I look at the code below (and believe me, I've stared at it for hours) I cannot see the problem. I look at the code and think to myself that I should be fine because I'm releasing the only object for which I am responsible (aString) and that NSMutableString should be taking care of cleaning up after any resizing it does. In the second example, just so you know in case it helps, the string being passed in comes from an ASIHTTPRequest object (it's the responseString) and I don't do anything at all with it. It's being called simply like so ([self DoStuff2:[request responseString]]) and I don't free the request myself either (I'm using a ASINetworkQueue and I assume that the requests are destroyed for me (I tried and caused errors because the request was already being release somewhere else). Also, I know it shouldn't do anything, but I even tried wrapping the code in autorelease pools, which of course did nothing. I should mention that this code is being run inside of an NSOperation. I thought that perhaps I am experiencing problems because NSOperations should create an autorelease pool for themselves, but I've tried that to no avail. Not related to NSMutableString, but I find I also have similar problems using the NSString componentsSeparatedByString method. Sometimes the memory used by the array that gets the separated components is never released. Hmmm...strings in general seem to be somewhat problematic for me it seems. I would appreciate ANY help anyone can provide. If you require more info, I'll be glad to add it. I do promise you that I've struggled with this (and other problems) for weeks and every problem I encounter I research hard and long until I find a solution - this is not an idle request, but a true cry for help! I've written so much code and now I'm trying to seal some small leaks etc and I notice this problem. Honestly, I cannot believe how memory management in Objective C can stump me so at times...I've read Apple's memory mgmt docs many times and I thought I thoroughly understood it and I try to be diligent about releasing objects I own, but sometimes I find myself wondering if I truly understand...I would like to put this to bed once and make sure I understand all this fully - to have this sort of question/problem after writing thousands of lines of code is more than a little scary/embarrassing/annoying. So again, if anybody has any insight, I'd be grateful. Thanks for your time and efforts. -(void)DoStuff { NSString *aString [ [[NSString alloc] initWithFormat:@"text %@ more text", self.strVariable]; [self.someMutableStringVar replaceOccurrencesOfString:@"replace" withString:aString options:NSCaseInsensitiveSearch range:NSMakeRange(0, [self.someMutableStringVar length])]; [aString release]; } -(void)DoStuff2:(NSString *)aString { [self.someMutableStringVar appendString:aString]; }

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• PHP framework question

  - by iconiK

  I'm currently working on a browser-based MMO and have chosen the LAMP stack because of the extremely low cost to start with in production (versus Windows + IIS + ASP.NET/C# + SQL Server, even though I have MSDN Universal). However I will need a PHP framework for this as it's no easy task. I am not restricted by anything other than the ability to run on Linux, as I will use a dedicated cloud hosting solution (and a VMWare image for development) and can configure it as needed. In no specific order: It has to be easily scalable; this is crucial. If the game becomes a steady success it will eventually outgrow the server beyond what the host provides and would have to be moved to several load-balanced servers. It is crucial that this can be done with minimum effort. I do know this might require following strict conventions, so if you know of any for your suggested framework please explain what would be needed. It has to provide modules for all the core tasks: authentication, ACL, database access, MVC, and so on. One or two missing modules are fine, as long as they can easily be written and integrated. It should support internationalization. I think there is no excuse for any web framework not to provide means of translating the application and switching between languages without a lot of effort from the programmer. Must have very good community support and preferably commercial support as well. Yes, I do know QCodo/QCubed is so nice, but it is not mature enough for this task. Smooth AJAX support is required. Whether the framework comes with AJAX-capable widgets or has an easy way of adding AJAX is not relevant, as long as AJAX is easily doable. I plan to use jQuery + Dojo or one of them alone - not exactly sure. Auto-magically doing stuff when it improves readability and relieves a lot of effort would be especially nice if it is generally reliable and does not interfere with other requirements. This seems to be the case of CakePHP. I have read a lot of comparisons and I know it's a really hot debate. The general answer is "try and see for yourself what suits you". However, I can't say it is easy for this task and I'm calling for your experience with building applications with similar requirements. So far I'm tied up between Zend and CakePHP by the general criteria, however, all well-known frameworks offer the same functionality in some way or another with different approaches each with it's own advantages and disadvantages. Edits: I am kinda new to MVC, however, I am willing to learn it and I don't care if a framework is easier for those new to MVC. I have lots of time to learn MVC and any other architectures (or whatever they're called) you recommend. I will use Zend as a utility "framework", even though it's just a collection of libraries (some good ones though, as I have been told). Current PHP contenders are: CakePHP, Kohana, Zend alone.

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• How to do inclusive range queries when only half-open range is supported (ala SortedMap.subMap)

  - by polygenelubricants

  On SortedMap.subMap This is the API for SortedMap<K,V>.subMap: SortedMap<K,V> subMap(K fromKey, K toKey) : Returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive. This inclusive lower bound, exclusive upper bound combo ("half-open range") is something that is prevalent in Java, and while it does have its benefits, it also has its quirks, as we shall soon see. The following snippet illustrates a simple usage of subMap: static <K,V> SortedMap<K,V> someSortOfSortedMap() { return Collections.synchronizedSortedMap(new TreeMap<K,V>()); } //... SortedMap<Integer,String> map = someSortOfSortedMap(); map.put(1, "One"); map.put(3, "Three"); map.put(5, "Five"); map.put(7, "Seven"); map.put(9, "Nine"); System.out.println(map.subMap(0, 4)); // prints "{1=One, 3=Three}" System.out.println(map.subMap(3, 7)); // prints "{3=Three, 5=Five}" The last line is important: 7=Seven is excluded, due to the exclusive upper bound nature of subMap. Now suppose that we actually need an inclusive upper bound, then we could try to write a utility method like this: static <V> SortedMap<Integer,V> subMapInclusive(SortedMap<Integer,V> map, int from, int to) { return (to == Integer.MAX_VALUE) ? map.tailMap(from) : map.subMap(from, to + 1); } Then, continuing on with the above snippet, we get: System.out.println(subMapInclusive(map, 3, 7)); // prints "{3=Three, 5=Five, 7=Seven}" map.put(Integer.MAX_VALUE, "Infinity"); System.out.println(subMapInclusive(map, 5, Integer.MAX_VALUE)); // {5=Five, 7=Seven, 9=Nine, 2147483647=Infinity} A couple of key observations need to be made: The good news is that we don't care about the type of the values, but... subMapInclusive assumes Integer keys for to + 1 to work. A generic version that also takes e.g. Long keys is not possible (see related questions) Not to mention that for Long, we need to compare against Long.MAX_VALUE instead Overloads for the numeric primitive boxed types Byte, Character, etc, as keys, must all be written individually A special check need to be made for toInclusive == Integer.MAX_VALUE, because +1 would overflow, and subMap would throw IllegalArgumentException: fromKey > toKey This, generally speaking, is an overly ugly and overly specific solution What about String keys? Or some unknown type that may not even be Comparable<?>? So the question is: is it possible to write a general subMapInclusive method that takes a SortedMap<K,V>, and K fromKey, K toKey, and perform an inclusive-range subMap queries? Related questions Are upper bounds of indexed ranges always assumed to be exclusive? Is it possible to write a generic +1 method for numeric box types in Java? On NavigableMap It should be mentioned that there's a NavigableMap.subMap overload that takes two additional boolean variables to signify whether the bounds are inclusive or exclusive. Had this been made available in SortedMap, then none of the above would've even been asked. So working with a NavigableMap<K,V> for inclusive range queries would've been ideal, but while Collections provides utility methods for SortedMap (among other things), we aren't afforded the same luxury with NavigableMap. Related questions Writing a synchronized thread-safety wrapper for NavigableMap On API providing only exclusive upper bound range queries Does this highlight a problem with exclusive upper bound range queries? How were inclusive range queries done in the past when exclusive upper bound is the only available functionality?

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• Two network interfaces and two IP addresses on the same subnet in Linux

  - by Scott Duckworth

  I recently ran into a situation where I needed two IP addresses on the same subnet assigned to one Linux host so that we could run two SSL/TLS sites. My first approach was to use IP aliasing, e.g. using eth0:0, eth0:1, etc, but our network admins have some fairly strict settings in place for security that squashed this idea: They use DHCP snooping and normally don't allow static IP addresses. Static addressing is accomplished by using static DHCP entries, so the same MAC address always gets the same IP assignment. This feature can be disabled per switchport if you ask and you have a reason for it (thankfully I have a good relationship with the network guys and this isn't hard to do). With the DHCP snooping disabled on the switchport, they had to put in a rule on the switch that said MAC address X is allowed to have IP address Y. Unfortunately this had the side effect of also saying that MAC address X is ONLY allowed to have IP address Y. IP aliasing required that MAC address X was assigned two IP addresses, so this didn't work. There may have been a way around these issues on the switch configuration, but in an attempt to preserve good relations with the network admins I tried to find another way. Having two network interfaces seemed like the next logical step. Thankfully this Linux system is a virtual machine, so I was able to easily add a second network interface (without rebooting, I might add - pretty cool). A few keystrokes later I had two network interfaces up and running and both pulled IP addresses from DHCP. But then the problem came in: the network admins could see (on the switch) the ARP entry for both interfaces, but only the first network interface that I brought up would respond to pings or any sort of TCP or UDP traffic. After lots of digging and poking, here's what I came up with. It seems to work, but it also seems to be a lot of work for something that seems like it should be simple. Any alternate ideas out there? Step 1: Enable ARP filtering on all interfaces: # sysctl -w net.ipv4.conf.all.arp_filter=1 # echo "net.ipv4.conf.all.arp_filter = 1" >> /etc/sysctl.conf From the file networking/ip-sysctl.txt in the Linux kernel docs: arp_filter - BOOLEAN 1 - Allows you to have multiple network interfaces on the same subnet, and have the ARPs for each interface be answered based on whether or not the kernel would route a packet from the ARP'd IP out that interface (therefore you must use source based routing for this to work). In other words it allows control of which cards (usually 1) will respond to an arp request. 0 - (default) The kernel can respond to arp requests with addresses from other interfaces. This may seem wrong but it usually makes sense, because it increases the chance of successful communication. IP addresses are owned by the complete host on Linux, not by particular interfaces. Only for more complex setups like load- balancing, does this behaviour cause problems. arp_filter for the interface will be enabled if at least one of conf/{all,interface}/arp_filter is set to TRUE, it will be disabled otherwise Step 2: Implement source-based routing I basically just followed directions from http://lartc.org/howto/lartc.rpdb.multiple-links.html, although that page was written with a different goal in mind (dealing with two ISPs). Assume that the subnet is 10.0.0.0/24, the gateway is 10.0.0.1, the IP address for eth0 is 10.0.0.100, and the IP address for eth1 is 10.0.0.101. Define two new routing tables named eth0 and eth1 in /etc/iproute2/rt_tables: ... top of file omitted ... 1 eth0 2 eth1 Define the routes for these two tables: # ip route add default via 10.0.0.1 table eth0 # ip route add default via 10.0.0.1 table eth1 # ip route add 10.0.0.0/24 dev eth0 src 10.0.0.100 table eth0 # ip route add 10.0.0.0/24 dev eth1 src 10.0.0.101 table eth1 Define the rules for when to use the new routing tables: # ip rule add from 10.0.0.100 table eth0 # ip rule add from 10.0.0.101 table eth1 The main routing table was already taken care of by DHCP (and it's not even clear that its strictly necessary in this case), but it basically equates to this: # ip route add default via 10.0.0.1 dev eth0 # ip route add 130.127.48.0/23 dev eth0 src 10.0.0.100 # ip route add 130.127.48.0/23 dev eth1 src 10.0.0.101 And voila! Everything seems to work just fine. Sending pings to both IP addresses works fine. Sending pings from this system to other systems and forcing the ping to use a specific interface works fine (ping -I eth0 10.0.0.1, ping -I eth1 10.0.0.1). And most importantly, all TCP and UDP traffic to/from either IP address works as expected. So again, my question is: is there a better way to do this? This seems like a lot of work for a seemingly simple problem.

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• Const references when dereferencing iterator on set, starting from Visual Studio 2010

  - by Patrick

  Starting from Visual Studio 2010, iterating over a set seems to return an iterator that dereferences the data as 'const data' instead of non-const. The following code is an example of something that does compile on Visual Studio 2005, but not on 2010 (this is an artificial example, but clearly illustrates the problem we found on our own code). In this example, I have a class that stores a position together with a temperature. I define comparison operators (not all them, just enough to illustrate the problem) that only use the position, not the temperature. The point is that for me two instances are identical if the position is identical; I don't care about the temperature. #include <set> class DataPoint { public: DataPoint (int x, int y) : m_x(x), m_y(y), m_temperature(0) {} void setTemperature(double t) {m_temperature = t;} bool operator<(const DataPoint& rhs) const { if (m_x==rhs.m_x) return m_y<rhs.m_y; else return m_x<rhs.m_x; } bool operator==(const DataPoint& rhs) const { if (m_x!=rhs.m_x) return false; if (m_y!=rhs.m_y) return false; return true; } private: int m_x; int m_y; double m_temperature; }; typedef std::set<DataPoint> DataPointCollection; void main(void) { DataPointCollection points; points.insert (DataPoint(1,1)); points.insert (DataPoint(1,1)); points.insert (DataPoint(1,2)); points.insert (DataPoint(1,3)); points.insert (DataPoint(1,1)); for (DataPointCollection::iterator it=points.begin();it!=points.end();++it) { DataPoint &point = *it; point.setTemperature(10); } } In the main routine I have a set to which I add some points. To check the correctness of the comparison operator, I add data points with the same position multiple times. When writing the contents of the set, I can clearly see there are only 3 points in the set. The for-loop loops over the set, and sets the temperature. Logically this is allowed, since the temperature is not used in the comparison operators. This code compiles correctly in Visual Studio 2005, but gives compilation errors in Visual Studio 2010 on the following line (in the for-loop): DataPoint &point = *it; The error given is that it can't assign a "const DataPoint" to a [non-const] "DataPoint &". It seems that you have no decent (= non-dirty) way of writing this code in VS2010 if you have a comparison operator that only compares parts of the data members. Possible solutions are: Adding a const-cast to the line where it gives an error Making temperature mutable and making setTemperature a const method But to me both solutions seem rather 'dirty'. It looks like the C++ standards committee overlooked this situation. Or not? What are clean solutions to solve this problem? Did some of you encounter this same problem and how did you solve it? Patrick

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• NSXMLParser not parsing attributes. No NSXMLParser Error.

  - by Iris

  I am trying to parse the XML located at this URL: http://www.iglooseat.com/gis_iphone_xml.php?zip=06488 // 1) This method gets invoked when the user presses a button on the Iphone to retrieve the xml data (IBAction)getLocations:(id)sender { NSString *msg=nil; NSString *urlString= [[NSString alloc] initWithFormat:@"http://www.iglooseat.com/gis_iphone_xml.php?zip=%@",zipField.text]; // send the URL NSError *error; [siteList updateLocationsFromURL:urlString parseError:&error]; WPSite *w = [siteList siteAtIndex:0]; // alert user what's in the zipField msg = [[NSString alloc] initWithFormat: @"url to send: %@\n site name: %@" , urlString , w.name]; UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Debug" message:msg delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil]; [urlString release]; [alert show]; [alert release]; [msg release]; } // 2) This function takes the URL and performs XML parsing on the data at that URL. (void)updateLocationsFromURL:(NSString )urlString parseError:(NSError *)error{ /* NSURL class that inherits from NSObject class that provides a way to manipulate URLs and the resources they reference. */ NSURL *url = [[NSURL alloc] initWithString:urlString]; /* initWithContentsOfURL: initializes a newly allocated data object initialized with the data from the location specified by a URL. */ NSXMLParser *parser = [[NSXMLParser alloc] initWithContentsOfURL:url]; // init bool to NO errorConnecting = NO; // release from mem the NSURfile://localhost/Users/icheung/Desktop/WPMap/Classes/WPSite.mL [url release]; // set parser delgate to self [parser setDelegate:self]; // don't process namespace [parser setShouldProcessNamespaces:YES]; // or namespace prefixes [parser setShouldReportNamespacePrefixes:NO]; /* don't care 'bout external (ex. don't perform I/O op's to load external DTD's (Document Type Definitions)) */ [parser setShouldResolveExternalEntities:NO]; // start the event-driven parsing operation [parser parse]; // get NSError object if an error occured during parsing NSError *parseError = [parser parserError]; if(parseError && error) { *error = parseError; NSLog(@"Error code:%d %@", parseError.code, parseError.domain); errorConnecting = YES; } // relase from mem the parser [parser release]; } // 3) In the parser:didStartElement:namespaceURI:qualifiedName:attributes: I attempt to extract the 'state' attribute from a 'marker' element in my xml. When I use the gdb debugger to inspect the contents of attributeDict it is empty and I'm not sure why. (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict { if(self.parserContentOfCurrentProperty == nil) { NSMutableString *tmp = [[NSMutableString alloc] init]; self.parserContentOfCurrentProperty = tmp; [tmp release]; } [self.parserContentOfCurrentProperty setString:@""]; self.parserNameOfCurrentProperty = elementName; if ([elementName isEqualToString:@"markers"]) { WPSite *tmp = [WPSite alloc]; self.parserCurrentSite = tmp; // retrive value for attribute NSString *stateAttribute = [attributeDict valueForKey:@"state"]; if (stateAttribute) { [self.parserCurrentSite setState:stateAttribute]; } // add this site to the site list [siteList addObject:self.parserCurrentSite]; return; } }

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• Custom links in RichTextBox

  - by IVlad

  Suppose I want every word starting with a # to generate an event on double click. For this I have implemented the following test code: private bool IsChannel(Point position, out int start, out int end) { if (richTextBox1.Text.Length == 0) { start = end = -1; return false; } int index = richTextBox1.GetCharIndexFromPosition(position); int stop = index; while (index >= 0 && richTextBox1.Text[index] != '#') { if (richTextBox1.Text[index] == ' ') { break; } --index; } if (index < 0 || richTextBox1.Text[index] != '#') { start = end = -1; return false; } while (stop < richTextBox1.Text.Length && richTextBox1.Text[stop] != ' ') { ++stop; } --stop; start = index; end = stop; return true; } private void richTextBox1_MouseMove(object sender, MouseEventArgs e) { textBox1.Text = richTextBox1.GetCharIndexFromPosition(new Point(e.X, e.Y)).ToString(); int d1, d2; if (IsChannel(new Point(e.X, e.Y), out d1, out d2) == true) { if (richTextBox1.Cursor != Cursors.Hand) { richTextBox1.Cursor = Cursors.Hand; } } else { richTextBox1.Cursor = Cursors.Arrow; } } This handles detecting words that start with # and making the mouse cursor a hand when it hovers over them. However, I have the following two problems: If I try to implement a double click event for richTextBox1, I can detect when a word is clicked, however that word is highlighted (selected), which I'd like to avoid. I can deselect it programmatically by selecting the end of the text, but that causes a flicker, which I would like to avoid. What ways are there to do this? The GetCharIndexFromPosition method returns the index of the character that is closest to the cursor. This means that if the only thing my RichTextBox contains is a word starting with a # then the cursor will be a hand no matter where on the rich text control it is. How can I make it so that it is only a hand when it hovers over an actual word or character that is part of a word I'm interested in? The implemented URL detection also partially suffers from this problem. If I enable detection of URLs and only write www.test.com in the rich text editor, the cursor will be a hand as long as it is on or below the link. It will not be a hand if it's to the right of the link however. I'm fine even with this functionality if making the cursor a hand if and only if it's on the text proves to be too difficult. I'm guessing I'll have to resort to some sort of Windows API calls, but I don't really know where to start. I am using Visual Studio 2008 and I would like to implement this myself. Update: The flickering problem would be solved if I could make it so that no text is selectable through double clicking, only through dragging the mouse cursor. Is this easier to achieve? Because I don't really care if one can select text or not by double clicking in this case.

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• multiple valgrind errors: Conditional jump or move depends on uninitialised value(s)

  - by Hristo

  I'm running valgrind and I'm getting the following error (this is not the only one): ==21743== Conditional jump or move depends on uninitialised value(s) ==21743== at 0x4A06509: index (mc_replace_strmem.c:164) ==21743== by 0x33B7CBB3CD: gaih_inet (in /lib64/libc-2.5.so) ==21743== by 0x33B7CBD629: getaddrinfo (in /lib64/libc-2.5.so) ==21743== by 0x401A5F: tunnelURL (proxy.c:336) ==21743== by 0x40142A: client_thread (proxy.c:194) ==21743== by 0x33B8806616: start_thread (in /lib64/libpthread-2.5.so) ==21743== by 0x33B7CD3C2C: clone (in /lib64/libc-2.5.so) My tunnelURL() function looks like this: char * tunnelURL(char *url) { char * a = strstr(url, "//"); a += 2; char * path = strstr(a, "/"); char host[256]; strncpy (host, a, strlen(a)-strlen(path)); /* * The following is courtesy of Beej's Guide */ int status; int proxySocketFD; struct addrinfo hints; struct addrinfo *servinfo; // will point to the results memset(&hints, 0, sizeof(hints)); // make sure the struct is empty hints.ai_family = AF_INET; // don't care IPv4 or IPv6 hints.ai_socktype = SOCK_STREAM; // TCP stream sockets hints.ai_flags = AI_PASSIVE; // fill in my IP for me if ((status = getaddrinfo(host, "80", &hints, &servinfo)) != 0) { perror("getaddrinfo() fail"); exit(1); } // create socket if ((proxySocketFD = socket(servinfo->ai_family, servinfo->ai_socktype, servinfo->ai_protocol)) == -1) { perror("proxy socket() fail"); exit(1); } // connect if (connect(proxySocketFD, servinfo->ai_addr, servinfo->ai_addrlen) != 0) { printf("connect() fail"); exit(1); } // construct request char request[strlen(path) + strlen(host) + 26]; sprintf(request, "GET %s HTTP/1.1\r\nHost: %s\r\n\r\n", path, host); printf("%s", request); // send request send(proxySocketFD, request, strlen(request), 0); // receive response int i = 0; int amntRecvd = 0; char *pageContentBuffer = (char*) malloc(4096 * sizeof(char)); while ((amntRecvd = recv(proxySocketFD, pageContentBuffer + i, 4096, 0)) > 0) { i += amntRecvd; realloc(pageContentBuffer, i * 4096 * sizeof(char)); } // close proxy socket close(proxySocketFD); // deallocate memory freeaddrinfo(servinfo); return pageContentBuffer; } Line 336 corresponds to the if statement with the getaddrinfo() function call. I'm not really sure what I haven't initialized. The string I'm passing in "should" be already set... I'm printing it out just fine. I also get another error corresponding to the same line of code: ==21743== Use of uninitialised value of size 8 ==21743== at 0x33B7D05816: __nscd_cache_search (in /lib64/libc-2.5.so) ==21743== by 0x33B7D0438B: nscd_gethst_r (in /lib64/libc-2.5.so) ==21743== by 0x33B7D04B26: __nscd_gethostbyname2_r (in /lib64/libc-2.5.so) ==21743== by 0x33B7CE9F5E: gethostbyname2_r@@GLIBC_2.2.5 (in /lib64/libc-2.5.so) ==21743== by 0x33B7CBC522: gaih_inet (in /lib64/libc-2.5.so) ==21743== by 0x33B7CBD629: getaddrinfo (in /lib64/libc-2.5.so) ==21743== by 0x401A5F: tunnelURL (proxy.c:336) ==21743== by 0x40142A: client_thread (proxy.c:194) ==21743== by 0x33B8806616: start_thread (in /lib64/libpthread-2.5.so) ==21743== by 0x33B7CD3C2C: clone (in /lib64/libc-2.5.so) Any ideas as to what might becausing this? This is written in C btw... Thanks, Hristo

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• In Ruby, how to I read memory values from an external process?

  - by grg-n-sox

  So all I simply want to do is make a Ruby program that reads some values from known memory address in another process's virtual memory. Through my research and basic knowledge of hex editing a running process's x86 assembly in memory, I have found the base address and offsets for the values in memory I want. I do not want to change them; I just want to read them. I asked a developer of a memory editor how to approach this abstract of language and assuming a Windows platform. He told me the Win32API calls for OpenProcess, CreateProcess, ReadProcessMemory, and WriteProcessMemory were the way to go using either C or C++. I think that the way to go would be just using the Win32API class and mapping two instances of it; One for either OpenProcess or CreateProcess, depending on if the user already has th process running or not, and another instance will be mapped to ReadProcessMemory. I probably still need to find the function for getting the list of running processes so I know which running process is the one I want if it is running already. This would take some work to put all together, but I am figuring it wouldn't be too bad to code up. It is just a new area of programming for me since I have never worked this low level from a high level language (well, higher level than C anyways). I am just wondering of the ways to approach this. I could just use a bunch or Win32API calls, but that means having to deal with a bunch of string and array pack and unpacking that is system dependant I want to eventually make this work cross-platform since the process I am reading from is produced from an executable that has multiple platform builds, (I know the memory address changes from system to system. The idea is to have a flat file that contains all memory mappings so the Ruby program can just match the current platform environment to the matching memory mapping.) but from the looks of things I'll just have to make a class that wraps whatever is the current platform's system shared library memory related function calls. For all I know, there could already exist a Ruby gem that takes care of all of this for me that I am just not finding. I could also possibly try editing the executables for each build to make it so whenever the memory values I want to read from are written to by the process, it also writes a copy of the new value to a space in shared memory that I somehow have Ruby make an instance of a class that is a pointer under the hood to that shared memory address and somehow signal to the Ruby program that the value was updated and should be reloaded. Basically a interrupt based system would be nice, but since the purpose of reading these values is just to send to a scoreboard broadcasted from a central server, I could just stick to a polling based system that sends updates at fixed time intervals. I also could just abandon Ruby altogether and go for C or C++ but I do not know those nearly as well. I actually know more x86 than C++ and I only know C as far as system independent ANSI C and have never dealt with shared system libraries before. So is there a gem or lesser known module available that has already done this? If not, then any additional information as to how to accomplish this would be nice. I guess, long story short, how do I do all this? Thanks in advance, Grg PS: Also a confirmation that those Win32API calls should be aimed at the kernel32.dll library would be nice.

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• How to reduce Entity Framework 4 query compile time?

  - by Rup

  Summary: We're having problems with EF4 query compilation times of 12+ seconds. Cached queries will only get us so far; are there any ways we can actually reduce the compilation time? Is there anything we might be doing wrong we can look for? Thanks! We have an EF4 model which is exposed over the WCF services. For each of our entity types we expose a method to fetch and return the whole entity for display / edit including a number of referenced child objects. For one particular entity we have to .Include() 31 tables / sub-tables to return all relevant data. Unfortunately this makes the EF query compilation prohibitively slow: it takes 12-15 seconds to compile and builds a 7,800-line, 300K query. This is the back-end of a web UI which will need to be snappier than that. Is there anything we can do to improve this? We can CompiledQuery.Compile this - that doesn't do any work until first use and so helps the second and subsequent executions but our customer is nervous that the first usage shouldn't be slow either. Similarly if the IIS app pool hosting the web service gets recycled we'll lose the cached plan, although we can increase lifetimes to minimise this. Also I can't see a way to precompile this ahead of time and / or to serialise out the EF compiled query cache (short of reflection tricks). The CompiledQuery object only contains a GUID reference into the cache so it's the cache we really care about. (Writing this out it occurs to me I can kick off something in the background from app_startup to execute all queries to get them compiled - is that safe?) However even if we do solve that problem, we build up our search queries dynamically with LINQ-to-Entities clauses based on which parameters we're searching on: I don't think the SQL generator does a good enough job that we can move all that logic into the SQL layer so I don't think we can pre-compile our search queries. This is less serious because the search data results use fewer tables and so it's only 3-4 seconds compile not 12-15 but the customer thinks that still won't really be acceptable to end-users. So we really need to reduce the query compilation time somehow. Any ideas? Profiling points to ELinqQueryState.GetExecutionPlan as the place to start and I have attempted to step into that but without the real .NET 4 source available I couldn't get very far, and the source generated by Reflector won't let me step into some functions or set breakpoints in them. The project was upgraded from .NET 3.5 so I have tried regenerating the EDMX from scratch in EF4 in case there was something wrong with it but that didn't help. I have tried the EFProf utility advertised here but it doesn't look like it would help with this. My large query crashes its data collector anyway. I have run the generated query through SQL performance tuning and it already has 100% index usage. I can't see anything wrong with the database that would cause the query generator problems. Is there something O(n^2) in the execution plan compiler - is breaking this down into blocks of separate data loads rather than all 32 tables at once likely to help? Setting EF to lazy-load didn't help. I've bought the pre-release O'Reilly Julie Lerman EF4 book but I can't find anything in there to help beyond 'compile your queries'. I don't understand why it's taking 12-15 seconds to generate a single select across 32 tables so I'm optimistic there's some scope for improvement! Thanks for any suggestions! We're running against SQL Server 2008 in case that matters and XP / 7 / server 2008 R2 using RTM VS2010.

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• Clear data at serial port in Linux in C?

  - by ipkiss

  Hello guys, I am testing the sending and receiving programs with the code as The main() function is below: include include include include include include include "read_write.h" int fd; int initport(int fd) { struct termios options; // Get the current options for the port... tcgetattr(fd, &options); // Set the baud rates to 19200... cfsetispeed(&options, B9600); cfsetospeed(&options, B9600); // Enable the receiver and set local mode... options.c_cflag |= (CLOCAL | CREAD); options.c_cflag &= ~PARENB; options.c_cflag &= ~CSTOPB; options.c_cflag &= ~CSIZE; options.c_cflag |= CS8; // Set the new options for the port... tcsetattr(fd, TCSANOW, &options); return 1; } int main(int argc, char **argv) { fd = open("/dev/pts/2", O_RDWR | O_NOCTTY | O_NDELAY); if (fd == -1) { perror("open_port: Unable to open /dev/pts/1 - "); return 1; } else { fcntl(fd, F_SETFL, 0); } printf("baud=%d\n", getbaud(fd)); initport(fd); printf("baud=%d\n", getbaud(fd)); char sCmd[254]; sCmd[0] = 0x41; sCmd[1] = 0x42; sCmd[2] = 0x43; sCmd[3] = 0x00; if (!writeport(fd, sCmd)) { printf("write failed\n"); close(fd); return 1; } printf("written:%s\n", sCmd); usleep(500000); char sResult[254]; fcntl(fd, F_SETFL, FNDELAY); if (!readport(fd,sResult)) { printf("read failed\n"); close(fd); return 1; } printf("readport=%s\n", sResult); close(fd); return 0; } read_write.h: #include <stdio.h> /* Standard input/output definitions */ include /* String function definitions */ include /* UNIX standard function definitions */ include /* File control definitions */ include /* Error number definitions */ include /* POSIX terminal control definitions */ int writeport(int fd, char *chars) { int len = strlen(chars); chars[len] = 0x0d; // stick a after the command chars[len+1] = 0x00; // terminate the string properly int n = write(fd, chars, strlen(chars)); if (n < 0) { fputs("write failed!\n", stderr); return 0; } return 1; } int readport(int fd, char *result) { int iIn = read(fd, result, 254); result[iIn-1] = 0x00; if (iIn < 0) { if (errno == EAGAIN) { printf("SERIAL EAGAIN ERROR\n"); return 0; } else { printf("SERIAL read error %d %s\n", errno, strerror(errno)); return 0; } } return 1; } and got the issue: In order to test with serial port, I used the socat (https://help.ubuntu.com/community/VirtualSerialPort ) to create a pair serial ports on Linux and test my program with these port. The first time the program sends the data and the program receives data is ok. However, if I read again or even re-write the new data into the serial port, the return data is always null until I stop the virtual serial port and start it again, then the write and read data is ok, but still, only one time. (In the real case, the sending part will be done by another device, I am just taking care of the reading data from the serial port. I wrote both parts just to test my reading code.) Does anyone have any ideas? Thanks a lot.

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• Getting the constructor of an Interface Type through reflection, is there a better approach than loo

  - by Will Marcouiller

  I have written a generic type: IDirectorySource<T> where T : IDirectoryEntry, which I'm using to manage Active Directory entries through my interfaces objects: IGroup, IOrganizationalUnit, IUser. So that I can write the following: IDirectorySource<IGroup> groups = new DirectorySource<IGroup>(); // Where IGroup implements `IDirectoryEntry`, of course.` foreach (IGroup g in groups.ToList()) { listView1.Items.Add(g.Name).SubItems.Add(g.Description); } From the IDirectorySource<T>.ToList() methods, I use reflection to find out the appropriate constructor for the type parameter T. However, since T is given an interface type, it cannot find any constructor at all! Of course, I have an internal class Group : IGroup which implements the IGroup interface. No matter how hard I have tried, I can't figure out how to get the constructor out of my interface through my implementing class. [DirectorySchemaAttribute("group")] public interface IGroup { } internal class Group : IGroup { internal Group(DirectoryEntry entry) { NativeEntry = entry; Domain = NativeEntry.Path; } // Implementing IGroup interface... } Within the ToList() method of my IDirectorySource<T> interface implementation, I look for the constructor of T as follows: internal class DirectorySource<T> : IDirectorySource<T> { // Implementing properties... // Methods implementations... public IList<T> ToList() { Type t = typeof(T) // Let's assume we're always working with the IGroup interface as T here to keep it simple. // So, my `DirectorySchema` property is already set to "group". // My `DirectorySearcher` is already instantiated here, as I do it within the DirectorySource<T> constructor. Searcher.Filter = string.Format("(&(objectClass={0}))", DirectorySchema) ConstructorInfo ctor = null; ParameterInfo[] params = null; // This is where I get stuck for now... Please see the helper method. GetConstructor(out ctor, out params, new Type() { DirectoryEntry }); SearchResultCollection results = null; try { results = Searcher.FindAll(); } catch (DirectoryServicesCOMException ex) { // Handling exception here... } foreach (SearchResult entry in results) entities.Add(ctor.Invoke(new object() { entry.GetDirectoryEntry() })); return entities; } } private void GetConstructor(out ConstructorInfo constructor, out ParameterInfo[] parameters, Type paramsTypes) { Type t = typeof(T); ConstructorInfo[] ctors = t.GetConstructors(BindingFlags.CreateInstance | BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.InvokeMethod); bool found = true; foreach (ContructorInfo c in ctors) { parameters = c.GetParameters(); if (parameters.GetLength(0) == paramsTypes.GetLength(0)) { for (int index = 0; index < parameters.GetLength(0); ++index) { if (!(parameters[index].GetType() is paramsTypes[index].GetType())) found = false; } if (found) { constructor = c; return; } } } // Processing constructor not found message here... } My problem is that T will always be an interface, so it never finds a constructor. Is there a better way than looping through all of my assembly types for implementations of my interface? I don't care about rewriting a piece of my code, I want to do it right on the first place so that I won't need to come back again and again and again. EDIT #1 Following Sam's advice, I will for now go with the IName and Name convention. However, is it me or there's some way to improve my code? Thanks! =)

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