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  • ActionResult - Service

    - by cem
    I bored, writing same code for service and ui. Then i tried to write a converter for simple actions. This converter, converting Service Results to MVC result, seems like good solution for me but anyway i think this gonna opposite MVC pattern. So here, I need help, what you think about algorithm - is this good or not? Thanks ServiceResult - Base: public abstract class ServiceResult { public static NoPermissionResult Permission() { return new NoPermissionResult(); } public static SuccessResult Success() { return new SuccessResult(); } public static SuccessResult<T> Success<T>(T result) { return new SuccessResult<T>(result); } protected ServiceResult(ServiceResultType serviceResultType) { _resultType = serviceResultType; } private readonly ServiceResultType _resultType; public ServiceResultType ResultType { get { return _resultType; } } } public class SuccessResult<T> : ServiceResult { public SuccessResult(T result) : base(ServiceResultType.Success) { _result = result; } private readonly T _result; public T Result { get { return _result; } } } public class SuccessResult : SuccessResult<object> { public SuccessResult() : this(null) { } public SuccessResult(object o) : base(o) { } } Service - eg. ForumService: public ServiceResult Delete(IVUser user, int id) { Forum forum = Repository.GetDelete(id); if (!Permission.CanDelete(user, forum)) { return ServiceResult.Permission(); } Repository.Delete(forum); return ServiceResult.Success(); } Controller: public class BaseController { public ActionResult GetResult(ServiceResult result) { switch (result.ResultType) { case ServiceResultType.Success: var successResult = (SuccessResult)result; return View(successResult.Result); break; case ServiceResultType.NoPermission: return View("Error"); break; default: return View(); break; } } } [HandleError] public class ForumsController : BaseController { [ValidateAntiForgeryToken] [Transaction] [AcceptVerbs(HttpVerbs.Post)] public ActionResult Delete(int id) { ServiceResult result = ForumService.Delete(WebUser.Current, id); /* Custom result */ if (result.ResultType == ServiceResultType.Success) { TempData[ControllerEnums.GlobalViewDataProperty.PageMessage.ToString()] = "The forum was successfully deleted."; return this.RedirectToAction(ec => Index()); } /* Custom result */ /* Execute Permission result etc. */ TempData[ControllerEnums.GlobalViewDataProperty.PageMessage.ToString()] = "A problem was encountered preventing the forum from being deleted. " + "Another item likely depends on this forum."; return GetResult(result); } }

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  • How to Load Dependent Files on Demand + Check if They're Loaded or Not?

    - by br4inwash3r
    I'm trying to implement an assets/dependency loader that i've found from an old article at 24Ways.org. most of you might be familiar with it. it's from this article by Christian Heilmann: http://24ways.org/2007/keeping-javascript-dependencies-at-bay i've modified the script to load CSS files as well. and it's now quite close to what i want. but i still need to do some checking to see wether an asset have been completely loaded or not. just wondering if you guys have any ideas :) here's what my script currently looked like: var assetLoader = { assets: { products: { js: 'products.js', css: 'products.css', loaded: false }, articles: { js: 'articles.js', css: 'articles.css', loaded: false }, [...] cycle: { js: 'jquery.cycle.min.js', loaded: false }, swfobject: { js: 'jquery.swfobject.min.js', loaded: false } }, add: function(asset) { var comp = assetLoader.assets[asset]; var path = '/path/to/assets/'; if (comp && comp.loaded == false) { if (comp.js) { // load js var js = document.createElement('script'); js.src = path + 'js/' + comp.js; js.type = 'text/javascript'; js.charset = 'utf-8'; // append to document document.getElementsByTagName('body')[0].appendChild(js); } if (comp.css) { // load css var css = document.createElement('link'); css.rel = 'stylesheet'; css.href = path + 'css/' + comp.css; css.type = 'text/css'; css.media = 'screen, projection'; css.charset = 'utf-8'; // append to document document.getElementsByTagName('head')[0].appendChild(css); } } }, check: function(asset) { assetLoader.assets[asset].loaded = true; } } Christian explains this method in his article in great detail. I don't want to confuse you guys anymore with my bad english :P and here's an example of how i run the script: ... // load jquery cycle plugin if (page=='tvc' || page=='products') { if (!assetLoader.assets.cycle.loaded) { assetLoader.add('cycle'); } } // load products page assets if (!assetLoader.assets.products.loaded) { assetLoader.add('products'); } ... this kind of approach is very problematic though. coz assets loads asynchronously, which means some of the code inside products.js that depends on jquery.cycle.js might continue running before jquery.cycle.js is even loaded resulting in errors. while i'm quite aware that scripts can be attached with an onload event, i'm just not really sure how to implement it to my script. anyone care to help me? please... :P

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  • SSL Authentication with Certificates: Should the Certificates have a hostname?

    - by sixtyfootersdude
    Summary JBoss allows clients and servers to authenticate using certificates and ssl. One thing that seems strange is that you are not required to give your hostname on the certificate. I think that this means if Server B is in your truststore, Sever B can pretend to be any server that they want. (And likewise: if Client B is in your truststore...) Am I missing something here? Authentication Steps (Summary of Wikipeida Page) Client Server ================================================================================================= 1) Client sends Client Hello ENCRIPTION: None - highest TLS protocol supported - random number - list of cipher suites - compression methods 2) Sever Hello ENCRIPTION: None - highest TLS protocol supported - random number - choosen cipher suite - choosen compression method 3) Certificate Message ENCRIPTION: None - 4) ServerHelloDone ENCRIPTION: None 5) Certificate Message ENCRIPTION: None 6) ClientKeyExchange Message ENCRIPTION: server's public key => only server can read => if sever can read this he must own the certificate - may contain a PreMasterSecerate, public key or nothing (depends on cipher) 7) CertificateVerify Message ENCRIPTION: clients private key - purpose is to prove to the server that client owns the cert 8) BOTH CLIENT AND SERVER: - use random numbers and PreMasterSecret to compute a common secerate 9) Finished message - contains a has and MAC over previous handshakes (to ensure that those unincripted messages did not get broken) 10) Finished message - samething Sever Knows The client has the public key for the sent certificate (step 7) The client's certificate is valid because either: it has been signed by a CA (verisign) it has been self-signed BUT it is in the server's truststore It is not a replay attack because presumably the random number (step 1 or 2) is sent with each message Client Knows The server has the public key for the sent certificate (step 6 with step 8) The server's certificate is valid because either: it has been signed by a CA (verisign) it has been self-signed BUT it is in the client's truststore It is not a replay attack because presumably the random number (step 1 or 2) is sent with each message Potential Problem Suppose the client's truststore has certs in it: Server A Server B (malicous) Server A has hostname www.A.com Server B has hostname www.B.com Suppose: The client tries to connect to Server A but Server B launches a man in the middle attack. Since server B: has a public key for the certificate that will be sent to the client has a "valid certificate" (a cert in the truststore) And since: certificates do not have a hostname feild in them It seems like Server B can pretend to be Server A easily. Is there something that I am missing?

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  • C++ - Breaking code implementation into different parts

    - by Kotti
    Hi! The question plot (a bit abstract, but answering this question will help me in my real app): So, I have some abstract superclass for objects that can be rendered on the screen. Let's call it IRenderable. struct IRenderable { // (...) virtual void Render(RenderingInterface& ri) = 0; virtual ~IRenderable() { } }; And suppose I also have some other objects that derive from IRenderable, e.g. Cat and Dog. So far so good. I add some Cat and Dog specific methods, like SeekForWhiskas(...) and Bark(...). After that I add specific Render(...) method for them, so my code looks this way: class Cat : public IRenderable { public: void SeekForWhiskas(...) { // Implementation could be here or moved // to a source file (depends on me wanting // to inline it or not) } virtual void Render(...) { // Here comes the rendering routine, that // is specific for cats SomehowDrawAppropriateCat(...); } }; class Dog : public IRenderable { public: void Bark(...) { // Same as for 'SeekForWhiskas(...)' } virtual void Render(...) { // Here comes the rendering routine, that // is specific for dogs DrawMadDog(...); } }; And then somewhere else I can do drawing the way that an appropriate rendering routine is called: IRenderable* dog = new Dog(); dog->Render(...); My question is about logical wrapping of such kind of code. I want to break apart the code, that corresponds to rendering of the current object and it's own methods (Render and Bark in this example), so that my class implementation doesn't turn into a mess (imagine that I have 10 methods like Bark and of course my Render method doesn't fit in their company and would be hard to find). Two ways of making what I want to (as far as I know) are: Making appropriate routines that look like RenderCat(Cat& cat, RenderInterface* ri), joining them to render namespace and then the functions inside a class would look like virtual void Render(...) { RenderCat(*this, ...); }, but this is plain stupid, because I'll lose access to Cat's private members and friending these functions looks like a total design disaster. Using visitor pattern, but this would also mean I have to rebuild my app's design and looks like an inadequate way to make my code complicated from the very beginning. Any brilliant ideas? :)

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  • SQL Server architecture guidance

    - by Liam
    Hi, We are designing a new version of our existing product on a new schema. Its an internal web application with possibly 100 concurrent users (max)This will run on a SQL Server 2008 database. On of the discussion items recently is whether we should have a single database of split the database for performance reasons across 2 separate databases. The database could grow anywhere from 50-100GB over 5 years. We are Developers and not DBAs so it would be nice to get some general guidance. [I know the answer is not simple as it depends on the schema, archiving policy, amount of data etc. ] Option 1 Single Main Database [This is my preferred option]. The plan would be to have all the tables in a single database and possibly to use file groups and partitioning to separate the data if required across multiple disks. [Use schema if appropriate]. This should deal with the performance concerns One of the comments wrt this was that the a single server instance would still be processing this data so there would still be a processing bottle neck. For reporting we could have a separate reporting DB but this is still being discussed. Option 2 Split the database into 2 separate databases DB1 - Customers, Accounts, Customer resources etc DB2 - This would contain the bulk of the data [i.e. Vehicle tracking data, financial transaction tables etc]. These tables would typically contain a lot of data. [It could reside on a separate server if required] This plan would involve keeping the main data in a smaller database [DB1] and retaining the [mainly] read only transaction type data in a separate DB [DB2]. The UI would mainly read from DB1 and thus be more responsive. [I'm aware that this option makes it harder for Referential Integrity to be enforced.] Points for consideration As we are at the design stage we can at least make proper use of indexes to deal performance issues so thats why option 1 to me is attractive and its more of a standard approach. For both options we are considering implementing an archiving database. Apologies for the long Question. In summary the question is 1 DB or 2? Thanks in advance, Liam

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  • Dynamic Dispatch without Virtual Functions

    - by Kristopher Johnson
    I've got some legacy code that, instead of virtual functions, uses a kind field to do dynamic dispatch. It looks something like this: // Base struct shared by all subtypes // Plain-old data; can't use virtual functions struct POD { int kind; int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); }; enum Kind { Kind_Derived1, Kind_Derived2, Kind_Derived3 }; struct Derived1: POD { Derived1(): kind(Kind_Derived1) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; struct Derived2: POD { Derived2(): kind(Kind_Derived2) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; struct Derived3: POD { Derived3(): kind(Kind_Derived3) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; and then the POD class's function members are implemented like this: int POD::GetFoo() { // Call kind-specific function switch (kind) { case Kind_Derived1: { Derived1 *pDerived1 = static_cast<Derived1*>(this); return pDerived1->GetFoo(); } case Kind_Derived2: { Derived2 *pDerived2 = static_cast<Derived2*>(this); return pDerived2->GetFoo(); } case Kind_Derived3: { Derived3 *pDerived3 = static_cast<Derived3*>(this); return pDerived3->GetFoo(); } default: throw UnknownKindException(kind, "GetFoo"); } } POD::GetBar(), POD::GetBaz(), POD::GetXyzzy(), and other members are implemented similarly. This example is simplified. The actual code has about a dozen different subtypes of POD, and a couple dozen methods. New subtypes of POD and new methods are added pretty frequently, and so every time we do that, we have to update all these switch statements. The typical way to handle this would be to declare the function members virtual in the POD class, but we can't do that because the objects reside in shared memory. There is a lot of code that depends on these structs being plain-old-data, so even if I could figure out some way to have virtual functions in shared-memory objects, I wouldn't want to do that. So, I'm looking for suggestions as to the best way to clean this up so that all the knowledge of how to call the subtype methods is centralized in one place, rather than scattered among a couple dozen switch statements in a couple dozen functions. What occurs to me is that I can create some sort of adapter class that wraps a POD and uses templates to minimize the redundancy. But before I start down that path, I'd like to know how others have dealt with this.

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  • Strange lifecycle behaviour with f:ajax and valueChangedListener

    - by gerry
    I want to use the f:ajax tag to update a part of a page with a editor gui, which style depends on a selectOneMenu and its selected item. The problem is, that if the ajax is called the server first renders the editor and then executes the valueChangedListener method. In my JSF2.0 / Facelets app I've the following code: ... <h:selectOneMenu id="typeSelect" validator="#{addEntityBean.checkType}" value="#{addEntityBean.selectedTypeAsString}" valueChangeListener="#{addEntityBean.selectedTypeChanged}"> <f:ajax render="editorGrid"/> <f:selectItems value="#{addEntityBean.entityTypeListAsString}"/> </h:selectOneMenu> ... <h:panelGrid id="editorGrid" columns="2" binding="#{addEntityBean.dynamicEditorGrid}" /> The BackingBean code looks like this: public String getSelectedTypeAsString() { return selectedTypeAsString; } public void setSelectedTypeAsString(String selectedType) { this.selectedTypeAsString = selectedType; } public Class<? extends Entity> getSelectedType() { log.severe("getSelectedType"); Class<? extends Entity> res = null; if(selectedTypeAsString != null){ int index = entityTypeListAsString.indexOf(selectedTypeAsString); res = entityTypeList.get(index); } return res; } public void selectedTypeChanged(ValueChangeEvent event){ setSelectedTypeAsString((String)event.getNewValue()); Class<? extends Entity> clazz = getSelectedType(); if(clazz != null){ try { setEntity(clazz.newInstance()); } catch (Exception e) { log.severe(e); } } else{ setEntity(null); } } public HtmlPanelGrid getDynamicEditorGrid() { HtmlPanelGrid grid = DynamicHtmlComponentCreator.createHtmlPanelGrid(); Entity entity = getEntity(); if(entity != null){ log.severe("getEntity() -->"+entity.getClassName()); grid = (HtmlPanelGrid)buildGui(grid, entity, "entityBean.entity", false); } else log.severe("getEntity() --> null"); return grid; } The problem is, that the server logs show that at first the getDynamicEditorGrid() is executed. And later the selectedTypeChanged()-listener-method. So everytime the selected editor style type is update one selection later. I.e. after a page reload (the type is initally null) the user selects the A, now the getDynamicEditorGrid() is executed again with type null and after that the type is changed to A. Again the user selects now B (after A) and now the getDynamicEditorGrid() is executed with the type A and after that the type is changed to B. What is wrong with my code? How can I fix this really strange behavior...

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  • MS Access 07 - Q re lookup column vs many-to-many; Q re checkboxes in many-to-many forms

    - by TBinLondon
    Hello, I'm creating a database with Access. This is just a test database, similar to my requirements, so I can get my skills up before creating one for work. I've created a database for a fictional school as this is a good playground and rich data (many students have many subjects have many teachers, etc). Question 1 What is the difference, if any, between using a Lookup column and a many-to-many associate table? Example: I have Tables 'Teacher' and 'Subject'. Many teachers have many subjects. I can, and have, created a table 'Teacher_Subject' and run queries with this. I have then created a lookup column in teachers table with data from subjects. The lookup column seems to take the place of the teacher_subject table. (though the data on relationships is obviously duplicated between lookup table and teacher_subject and may vary). Which one is the 'better' option? Is there a snag with using lookup tables? (I realize that this is a very 'general' question. Links to other resources and answers saying 'that depends...' are appreciated) Question 2 What attracts me to lookup tables is the following: When creating a form for entering subjects for teachers, with lookup I can simply create checkboxes and click a subject for a teacher 'on' or 'off'. Each click on/off creates/removes a record in the lookup column (which replaces teacher_subject). If I use a form from a query from teacher subject with teacher as main form and subject as subform I run into this problem: In the subform I can either select each subject that teacher has in a bombo box, i.e. click, scroll down, select, go to next row, click, scroll down, etc. (takes too long) OR I can create a list box listing all available subjects in each row but allowing me to select only one. (takes up too much space). Is it possible to have a click on/off list box for teacher_subject, creating/removing a record there with each click? Note - I know zero SQL or VB. If the correct answer is "you need to know SQL for this" then that's cool. I just need to know. Thanks!

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  • PHP & MySQL - saving and looping problems.

    - by R.I.P.coalMINERS
    I'm new to PHP and MySQL I want a user to be able to store multiple names and there meanings in a MySQL database tables named names using PHP I will dynamically create form fields with JQuery every time a user clicks on a link so a user can enter 1 to 1,000,000 different names and there meanings which will be stored in a table called names. Since I asked my last question I figured out how to store my values from my form using the for loop but every time I loop my values when I add one or more dynamic fields the second form field named meaning will not save the value entered also my dynamic form fields keep looping doubling, tripling and so on the entered values into the database it all depends on how many form fields are added dynamically. I was wondering how can I fix these problems? On a side note I replaced the query with echo's to see the values that are being entered. Here is the PHP code. <?php if(isset($_POST['submit'])) { $mysqli = mysqli_connect("localhost", "root", "", "site"); $dbc = mysqli_query($mysqli,"SELECT * FROM names WHERE userID='$userID'"); $name = $_POST['name']; $meaning = $_POST['meaning']; if(isset($name['0']) && mysqli_num_rows($dbc) == 0 && trim($name['0'])!=='' && trim($meaning['0'])!=='') { for($n = 0; $n < count($name); $n++) { for($m = 0; $m < count($meaning); $m++) { echo $name[$n] . '<br />'; echo $meaning[$m] . '<br /><br />'; break; } } } } ?> And here is the HTML code. <form method="post" action="index.php"> <ul> <li><label for="name">Name: </label><input type="text" name="name[]" id="name" /></li> <li><label for="meaning">Meaning: </label><input type="text" name="meaning[]" id="meaning" /></li> <li><input type="submit" name="submit" value="Save" /></li> </ul> </form> If needed I will place the JQuery code.

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  • Mutable objects and hashCode

    - by robert
    Have the following class: public class Member { private int x; private long y; private double d; public Member(int x, long y, double d) { this.x = x; this.y = y; this.d = d; } @Override public int hashCode() { final int prime = 31; int result = 1; result = prime * result + x; result = (int) (prime * result + y); result = (int) (prime * result + Double.doubleToLongBits(d)); return result; } @Override public boolean equals(Object obj) { if (this == obj) { return true; } if (obj instanceof Member) { Member other = (Member) obj; return other.x == x && other.y == y && Double.compare(d, other.d) == 0; } return false; } public static void main(String[] args) { Set<Member> test = new HashSet<Member>(); Member b = new Member(1, 2, 3); test.add(b); System.out.println(b.hashCode()); b.x = 0; System.out.println(b.hashCode()); Member first = test.iterator().next(); System.out.println(test.contains(first)); System.out.println(b.equals(first)); System.out.println(test.add(first)); } } It produces the following results: 30814 29853 false true true Because the hashCode depends of the state of the object it can no longer by retrieved properly, so the check for containment fails. The HashSet in no longer working properly. A solution would be to make Member immutable, but is that the only solution? Should all classes added to HashSets be immutable? Is there any other way to handle the situation? Regards.

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  • How can I represent a line of music notes in a way that allows fast insertion at any index?

    - by chairbender
    For "fun", and to learn functional programming, I'm developing a program in Clojure that does algorithmic composition using ideas from this theory of music called "Westergaardian Theory". It generates lines of music (where a line is just a single staff consisting of a sequence of notes, each with pitches and durations). It basically works like this: Start with a line consisting of three notes (the specifics of how these are chosen are not important). Randomly perform one of several "operations" on this line. The operation picks randomly from all pairs of adjacent notes that meet a certain criteria (for each pair, the criteria only depends on the pair and is independent of the other notes in the line). It inserts 1 or several notes (depending on the operation) between the chosen pair. Each operation has its own unique criteria. Continue randomly performing these operations on the line until the line is the desired length. The issue I've run into is that my implementation of this is quite slow, and I suspect it could be made faster. I'm new to Clojure and functional programming in general (though I'm experienced with OO), so I'm hoping someone with more experience can point out if I'm not thinking in a functional paradigm or missing out on some FP technique. My current implementation is that each line is a vector containing maps. Each map has a :note and a :dur. :note's value is a keyword representing a musical note like :A4 or :C#3. :dur's value is a fraction, representing the duration of the note (1 is a whole note, 1/4 is a quarter note, etc...). So, for example, a line representing the C major scale starting on C3 would look like this: [ {:note :C3 :dur 1} {:note :D3 :dur 1} {:note :E3 :dur 1} {:note :F3 :dur 1} {:note :G3 :dur 1} {:note :A4 :dur 1} {:note :B4 :dur 1} ] This is a problematic representation because there's not really a quick way to insert into an arbitrary index of a vector. But insertion is the most frequently performed operation on these lines. My current terrible function for inserting notes into a line basically splits the vector using subvec at the point of insertion, uses conj to join the first part + notes + last part, then uses flatten and vec to make them all be in a one-dimensional vector. For example if I want to insert C3 and D3 into the the C major scale at index 3 (where the F3 is), it would do this (I'll use the note name in place of the :note and :dur maps): (conj [C3 D3 E3] [C3 D3] [F3 G3 A4 B4]), which creates [C3 D3 E3 [C3 D3] [F3 G3 A4 B4]] (vec (flatten previous-vector)) which gives [C3 D3 E3 C3 D3 F3 G3 A4 B4] The run time of that is O(n), AFAIK. I'm looking for a way to make this insertion faster. I've searched for information on Clojure data structures that have fast insertion but haven't found anything that would work. I found "finger trees" but they only allow fast insertion at the start or end of the list. Edit: I split this into two questions. The other part is here.

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  • Performance - FunctionCall vs Event vs Action vs Delegate

    - by hwcverwe
    Currently I am using Microsoft Sync Framework to synchronize databases. I need to gather information per record which is inserted/updated/deleted by Microsoft Sync Framework and do something with this information. The sync speed can go over 50.000 records per minute. So that means my additional code need to be very lightweight otherwise it will be a huge performance penalty. Microsoft Sync Framework raises an SyncProgress event for each record. I am subscribed to that code like this: // Assembly1 SyncProvider.SyncProgress += OnSyncProgress; // .... private void OnSyncProgress(object sender, DbSyncProgressEventArgs e) { switch (args.Stage) { case DbSyncStage.ApplyingInserts: // MethodCall/Delegate/Action<>/EventHandler<> => HandleInsertedRecordInformation // Do something with inserted record info break; case DbSyncStage.ApplyingUpdates: // MethodCall/Delegate/Action<>/EventHandler<> => HandleUpdatedRecordInformation // Do something with updated record info break; case DbSyncStage.ApplyingDeletes: // MethodCall/Delegate/Action<>/EventHandler<> => HandleDeletedRecordInformation // Do something with deleted record info break; } } Somewhere else in another assembly I have three methods: // Assembly2 public class SyncInformation { public void HandleInsertedRecordInformation(...) {...} public void HandleUpdatedRecordInformation(...) {...} public void HandleInsertedRecordInformation(...) {...} } Assembly2 has a reference to Assembly1. So Assembly1 does not know anything about the existence of the SyncInformation class which need to handle the gathered information. So I have the following options to trigger this code: use events and subscribe on it in Assembly2 1.1. EventHandler< 1.2. Action< 1.3. Delegates using dependency injection: public class Assembly2.SyncInformation : Assembly1.ISyncInformation Other? I know the performance depends on: OnSyncProgress switch using a method call, delegate, Action< or EventHandler< Implementation of SyncInformation class I currently don't care about the implementation of the SyncInformation class. I am mainly focused on the OnSyncProgress method and how to call the SyncInformation methods. So my questions are: What is the most efficient approach? What is the most in-efficient approach? Is there a better way than using a switch in OnSyncProgress?

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  • Is there a way to efficiently yield every file in a directory containing millions of files?

    - by Josh Smeaton
    I'm aware of os.listdir, but as far as I can gather, that gets all the filenames in a directory into memory, and then returns the list. What I want, is a way to yield a filename, work on it, and then yield the next one, without reading them all into memory. Is there any way to do this? I worry about the case where filenames change, new files are added, and files are deleted using such a method. Some iterators prevent you from modifying the collection during iteration, essentially by taking a snapshot of the state of the collection at the beginning, and comparing that state on each move operation. If there is an iterator capable of yielding filenames from a path, does it raise an error if there are filesystem changes (add, remove, rename files within the iterated directory) which modify the collection? There could potentially be a few cases that could cause the iterator to fail, and it all depends on how the iterator maintains state. Using S.Lotts example: filea.txt fileb.txt filec.txt Iterator yields filea.txt. During processing, filea.txt is renamed to filey.txt and fileb.txt is renamed to filez.txt. When the iterator attempts to get the next file, if it were to use the filename filea.txt to find it's current position in order to find the next file and filea.txt is not there, what would happen? It may not be able to recover it's position in the collection. Similarly, if the iterator were to fetch fileb.txt when yielding filea.txt, it could look up the position of fileb.txt, fail, and produce an error. If the iterator instead was able to somehow maintain an index dir.get_file(0), then maintaining positional state would not be affected, but some files could be missed, as their indexes could be moved to an index 'behind' the iterator. This is all theoretical of course, since there appears to be no built-in (python) way of iterating over the files in a directory. There are some great answers below, however, that solve the problem by using queues and notifications. Edit: The OS of concern is Redhat. My use case is this: Process A is continuously writing files to a storage location. Process B (the one I'm writing), will be iterating over these files, doing some processing based on the filename, and moving the files to another location. Edit: Definition of valid: Adjective 1. Well grounded or justifiable, pertinent. (Sorry S.Lott, I couldn't resist). I've edited the paragraph in question above.

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  • Big O Complexity of a method

    - by timeNomad
    I have this method: public static int what(String str, char start, char end) { int count=0; for(int i=0;i<str.length(); i++) { if(str.charAt(i) == start) { for(int j=i+1;j<str.length(); j++) { if(str.charAt(j) == end) count++; } } } return count; } What I need to find is: 1) What is it doing? Answer: counting the total number of end occurrences after EACH (or is it? Not specified in the assignment, point 3 depends on this) start. 2) What is its complexity? Answer: the first loops iterates over the string completely, so it's at least O(n), the second loop executes only if start char is found and even then partially (index at which start was found + 1). Although, big O is all about worst case no? So in the worst case, start is the 1st char & the inner iteration iterates over the string n-1 times, the -1 is a constant so it's n. But, the inner loop won't be executed every outer iteration pass, statistically, but since big O is about worst case, is it correct to say the complexity of it is O(n^2)? Ignoring any constants and the fact that in 99.99% of times the inner loop won't execute every outer loop pass. 3) Rewrite it so that complexity is lower. What I'm not sure of is whether start occurs at most once or more, if once at most, then method can be rewritten using one loop (having a flag indicating whether start has been encountered and from there on incrementing count at each end occurrence), yielding a complexity of O(n). In case though, that start can appear multiple times, which most likely it is, because assignment is of a Java course and I don't think they would make such ambiguity. Solving, in this case, is not possible using one loop... WAIT! Yes it is..! Just have a variable, say, inc to be incremented each time start is encountered & used to increment count each time end is encountered after the 1st start was found: inc = 0, count = 0 if (current char == start) inc++ if (inc > 0 && current char == end) count += inc This would also yield a complexity of O(n)? Because there is only 1 loop. Yes I realize I wrote a lot hehe, but what I also realized is that I understand a lot better by forming my thoughts into words...

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  • How do I mock/fake/replace/stub a base class at unit-test time in C#?

    - by MatthewMartin
    UPDATE: I've changed the wording of the question. Previously it was a yes/no question about if a base class could be changed at runtime. I may be working on mission impossible here, but I seem to be getting close. I want to extend a ASP.NET control, and I want my code to be unit testable. Also, I'd like to be able to fake behaviors of a real Label (namely things like ID generation, etc), which a real Label can't do in an nUnit host. Here a working example that makes assertions on something that depends on a real base class and something that doesn't-- in a more realistic unit test, the test would depend on both --i.e. an ID existing and some custom behavior. Anyhow the code says it better than I can: public class LabelWrapper : Label //Runtime //public class LabelWrapper : FakeLabel //Unit Test time { private readonly LabelLogic logic= new LabelLogic(); public override string Text { get { return logic.ProcessGetText(base.Text); } set { base.Text=logic.ProcessSetText(value); } } } //Ugh, now I have to test FakeLabelWrapper public class FakeLabelWrapper : FakeLabel //Unit Test time { private readonly LabelLogic logic= new LabelLogic(); public override string Text { get { return logic.ProcessGetText(base.Text); } set { base.Text=logic.ProcessSetText(value); } } } [TestFixture] public class UnitTest { [Test] public void Test() { //Wish this was LabelWrapper label = new LabelWrapper(new FakeBase()) LabelWrapper label = new LabelWrapper(); //FakeLabelWrapper label = new FakeLabelWrapper(); label.Text = "ToUpper"; Assert.AreEqual("TOUPPER",label.Text); StringWriter stringWriter = new StringWriter(); HtmlTextWriter writer = new HtmlTextWriter(stringWriter); label.RenderControl(writer); Assert.AreEqual(1,label.ID); Assert.AreEqual("<span>TOUPPER</span>", stringWriter.ToString()); } } public class FakeLabel { virtual public string Text { get; set; } public void RenderControl(TextWriter writer) { writer.Write("<span>" + Text + "</span>"); } } //System Under Test internal class LabelLogic { internal string ProcessGetText(string value) { return value.ToUpper(); } internal string ProcessSetText(string value) { return value.ToUpper(); } }

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  • sqlite 3 opening issue

    - by anonymous
    I'm getting my data ,with several similar methods, from sqlite3 file like in following code: -(NSMutableArray *) getCountersByID:(NSString *) championID{ NSMutableArray *arrayOfCounters; arrayOfCounters = [[NSMutableArray alloc] init]; @try { NSFileManager *fileManager = [NSFileManager defaultManager]; NSString *databasePath = [[[NSBundle mainBundle] resourcePath ]stringByAppendingPathComponent:@"DatabaseCounters.sqlite"]; BOOL success = [fileManager fileExistsAtPath:databasePath]; if (!success) { NSLog(@"cannot connect to Database! at filepath %@",databasePath); } else{ NSLog (@"SUCCESS getCountersByID!!"); } if(sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK){ NSString *tempString = [NSString stringWithFormat:@"SELECT COUNTER_ID FROM COUNTERS WHERE CHAMPION_ID = %@",championID]; const char *sql = [tempString cStringUsingEncoding:NSASCIIStringEncoding]; sqlite3_stmt *sqlStatement; int ret = sqlite3_prepare(database, sql, -1, &sqlStatement, NULL); if (ret != SQLITE_OK) { NSLog(@"Error calling sqlite3_prepare: %d", ret); } if(sqlite3_prepare_v2(database, sql, -1, &sqlStatement, NULL) == SQLITE_OK){ while (sqlite3_step(sqlStatement)==SQLITE_ROW) { counterList *CounterList = [[counterList alloc]init]; CounterList.counterID = [NSString stringWithUTF8String:(char *) sqlite3_column_text(sqlStatement,0)]; [arrayOfCounters addObject:CounterList]; } } else{ NSLog(@"problem with database prepare"); } sqlite3_finalize(sqlStatement); } else{ NSLog(@"problem with database openning %s",sqlite3_errmsg(database)); } } @catch (NSException *exception){ NSLog(@"An exception occured: %@", [exception reason]); } @finally{ sqlite3_close(database); return arrayOfCounters; } //end } then i'm getting access to data with this and other similar lines of code: myCounterList *MyCounterList = [[myCounterList alloc] init]; countersTempArray = [MyCounterList getCountersByID:"2"]; [countersArray addObject:[NSString stringWithFormat:@"%@",(((counterList *) [countersTempArray objectAtIndex:i]).counterID)]]; I'm getting a lot of data like image name and showing combination of them that depends on users input with such code: UIImage *tempImage = [UIImage imageNamed:[NSString stringWithFormat:@"%@_0.jpg",[countersArray objectAtIndex:0]]]; [championSelection setBackgroundImage:tempImage forState:UIControlStateNormal]; My problem: When i'm run my app for some time and get a lot of data it throws error: " problem with database openning unable to open database file - error = 24 (Too many open files)" My guess is that i'm opening my database every time when getCountersByID is called but not closing it. My question: Am i using right approach to open and close database that i use? Similar questions that have not helped me to solve this problem: unable to open database Sqlite Opening Error : Unable to open database UPDATE: I made assumption that error is showing up because i use this lines of code too much: NSFileManager *fileManager = [NSFileManager defaultManager]; NSString *databasePath = [[[NSBundle mainBundle] resourcePath ]stringByAppendingPathComponent:@"DatabaseCounters.sqlite"]; BOOL success = [fileManager fileExistsAtPath:databasePath]; and ending up with error 24. So i made them global but sqlite3_errmsg shows same err 24, but app runs much faster now I'll try to debug my app, see what happens

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  • jQuery getScript function with frames

    - by user210099
    Hello.. I'm a novice at Javascript/Jquery programming, so an apology if this is a simple/silly question. I am trying to use the jQuery .getScript() function to refresh part of an existing webpage. This webpage must be run on a local file system, and a large amount of the formatting is done using frames. Right now, there’s three main frames- a sidebar which displays possible “scopes” to choose from, a main frame which displays the majority of the contents of the webpage, and a footer frame. The main entry into the page is in an index.html file, which loads a sidebar.html, main.html, and footer.html file into each of the respective frames. In turn, the main.html has a number of javascript files which it loads, the main being a main.js, which contains numerous functions to format/process the contents for this main window. After loading this javascript file, main.html loads a few javascript files, which contain the data which is going to be displayed in the main frame. These files that are loaded have a fixed data structure, and are dependent on the functions that were loaded by the main.js file. Loading the webpage works fine now, but when a user tries to switch to another “scope”, the whole webpage is reloaded to make the switch. The only difference in the webpage is the content in the main.js frame, loaded in by a different set of .js files. Enough text, let’s look at some code. When the webpage loads, I tried to add a simple call to the getScript function in a .js file at the index.html level which handles switching scopes. This file, newFile, has different data definitions than the previously loaded oldFile.js which was loaded in the main.html file. $.getScript(/js/newFile.js); However this doesn’t work, since newFile.js depends on a parseData() function which is in main.js. If I open firebug up, parseData is not located in the dom tab, which I assume is related to some scoping issue with the main.html and main.js file existing in a different frame. I tried to do some targeting to the correct “frame” but I don’t think I understand jQuery enough to know what is happening. $(window.parent.frames[0]).getScript(/js/newFile.js); Any suggestions? If I were to type into firebug console “parseData” it can not find it: “ReferenceError: parseData is not defined” However, if I type in window.parent.frames[1].parseData, it can find the function. Sorry about all the rambling and poor understanding of javascript. Hopefully someone can provide some assistance! Thanks

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  • Weird seg fault problem

    - by bluedaemon
    Greetings, I'm having a weird seg fault problem. My application dumps a core file at runtime. After digging into it I found it died in this block: #include <lib1/c.h> ... x::c obj; obj.func1(); I defined class c in a library lib1: namespace x { struct c { c(); ~c(); void fun1(); vector<char *> _data; }; } x::c::c() { } x::c::~c() { for ( int i = 0; i < _data.size(); ++i ) delete _data[i]; } I could not figure it out for some time till I ran nm on the lib1.so file: there are more function definitions than I defined: x::c::c() x::c::c() x::c::~c() x::c::~c() x::c::func1() x::c::func2() After searching in code base I found someone else defined a class with same name in same namespace, but in another library lib2 as follows: namespace x { struct c { c(); ~c(); void func2(); vector<string> strs_; }; } x::c::c() { } x::c::~c() { } My application links to lib2, which has dependency on lib1. This interesting behavior brings several questions: Why would it even work? I would expect a "multiple definitions" error while linking against lib2 (which depends upon lib1) but never had such. The application seems to be doing what's defined in func1 except it dumps a core at runtime. After attaching debugger, I found my application calls the ctor of class c in lib2, then calls func1 (defined in lib1). When going out of scope it calls dtor of class c in lib2, where the seg fault occurs. Can anybody teach me how this could even occur? How can I prevent such problems from happening again? Is there any C++ syntax I can use? Forgot to mention I'm using g++ 4.1 on RHEL4, thank you very much!

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  • Starting jetty with spring xml as a background process/thread

    - by compass
    My goal is to set up a jetty test server and inject a custom servlet to test some REST classes in my project. I was able to launch the server with spring xml and run tests against that server. The issue I'm having is sometimes after the server started, the process stopped at the point before running the tests. It seems jetty didn't go to background. It works every time on my computer. But when I deployed to my CI server, it doesn't work. It also doesn't work when I'm on VPN. (Strange.) The server should be completed initialized as when the tests stuck, I was able to access the server using a browser. Here is my spring context xml: .... <bean id="servletHolder" class="org.eclipse.jetty.servlet.ServletHolder"> <constructor-arg ref="courseApiServlet"/> </bean> <bean id="servletHandler" class="org.eclipse.jetty.servlet.ServletContextHandler"/> <!-- Adding the servlet holders to the handlers --> <bean id="servletHandlerSetter" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean"> <property name="targetObject" ref="servletHandler"/> <property name="targetMethod" value="addServlet"/> <property name="arguments"> <list> <ref bean="servletHolder"/> <value>/*</value> </list> </property> </bean> <bean id="httpTestServer" class="org.eclipse.jetty.server.Server" init-method="start" destroy-method="stop" depends-on="servletHandlerSetter"> <property name="connectors"> <list> <bean class="org.eclipse.jetty.server.nio.SelectChannelConnector"> <property name="port" value="#{settings['webservice.server.port']}" /> </bean> </list> </property> <property name="handler"> <ref bean="servletHandler" /> </property> </bean> Running latest Jetty 8.1.8 server and Spring 3.1.3. Any idea?

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  • Is this a good approach to dealing with tagging?

    - by Mel
    Can this code be optimized or re-factored? Is this an optimal approach to tagging? The following code is a callback in my posts model. It creates a record that associates a tag with a post in a QuestionsTags joiner table. When necessary, if a given tag does not already exist in the tags table, the function creates it, then uses its id to create the new record in the QuestionsTags table. The difficulty with this approach is the QuestionsTags table depends on data in the tags table which may or may not exist. The function assumes the following tables: tags(id, tagName), posts(tags) // Comma delimited list questionsTags(postId, tagId) The idea is to loop over a delimited list of tags submitted with a post and check to see if each tag already exists in the tags table If tag exists: Check to see if there's already a QuestionTag record for this post and this tag in the QuestionTags table. If yes, do nothing (the association already exists) If no, create a new QuestionTag record using the id of the existing tag and the postId If tag does not already exist: Create the new tag in the tags table Use its id to create a new QuestionsTags record Code /** * @hint Sets tags for a given question. **/ private function setTags() { // Loop over the comma and space delmited list of tags for (local.i = 1; local.i LTE ListLen(this.tags, ", "); local.i = (local.i + 1)) { // Check if the tag already exists in the database local.tag = model("tag").findOneByTagName(local.i); // If the tag exists, look for an existing association between the tag and the question in the QuestionTag table if (IsObject(local.tag)) { local.questionTag = model("questionTag").findOneByPostIdAndTagId(values="#this.postId#,#local.tag.id#"); // If no assciatione exists, create a new QuestionTag record using the tagId and the postId if (! IsObject(local.questionTag)) { local.newQuestionTag = model("questionTag").new(postId = this.id, tagId = local.tag.id); // Abort if the saving the new QuestionTag is unsuccesful if (! local.newQuestionTag.save()) { return false; } } } // If the tag does not exist create it else { local.newTag = model("tag").new(tagName = local.i, userId = this.ownerUserId); // Abort if the the new tag is not saved successfully if (! local.newTag.save()) { return false; } // Otherwise create a new association in the QuestionTags table using the id of the newly created tag and the postId local.newQuestionTag = model("questionTag").new(postId = this.id, tagId = local.newTag.id); // Abort if the new QuestionTag does not save correctly if (! local.newQuestionTag.save()) { return false; } } } } FYI: I'm using CFWheels in my application, which explains the ORM functions used.

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  • Can't get MySQL to install

    - by James Marthenal
    I'd like to think I know what I'm doing in a Unix shell but maybe not. I made a mistake in a configuration file for MySQL, so I decided to just uninstall it and then reinstall it, so I did: sudo apt-get --purge remove mysql-server mysql-server-5.0 mysql-client The files were deleted, so I then tried to install it, but it didn't ask me for a root password or anything else, so I uninstalled it using the above command again and then did sudo rm -rf /etc/mysql sudo rm /etc/init.d/mysql sudo rm -rf /var/lib/mysql* I then restarted the computer then installed it again: sudo apt-get install mysql-server mysql-client It asked for a root password, and everything looked like it would work, until I saw this: $ sudo apt-get install mysql-server mysql-client Reading package lists... Done Building dependency tree Reading state information... Done The following extra packages will be installed: mysql-server-5.0 Suggested packages: tinyca The following NEW packages will be installed: mysql-client mysql-server mysql-server-5.0 0 upgraded, 3 newly installed, 0 to remove and 1 not upgraded. Need to get 0B/27.4MB of archives. After this operation, 86.7MB of additional disk space will be used. Do you want to continue [Y/n]? y WARNING: The following packages cannot be authenticated! mysql-server-5.0 mysql-client mysql-server Authentication warning overridden. Preconfiguring packages ... Can't exec "/tmp/mysql-server-5.0.config.28101": Permission denied at /usr/share/perl/5.10/IPC/Open3.pm line 168. open2: exec of /tmp/mysql-server-5.0.config.28101 configure failed at /usr/share/perl5/Debconf/ConfModule.pm line 59 mysql-server-5.0 failed to preconfigure, with exit status 255 Selecting previously deselected package mysql-server-5.0. (Reading database ... 160284 files and directories currently installed.) Unpacking mysql-server-5.0 (from .../mysql-server-5.0_5.0.51a-24+lenny5_amd64.deb) ... Selecting previously deselected package mysql-client. Unpacking mysql-client (from .../mysql-client_5.0.51a-24+lenny5_all.deb) ... Selecting previously deselected package mysql-server. Unpacking mysql-server (from .../mysql-server_5.0.51a-24+lenny5_all.deb) ... Processing triggers for man-db ... Setting up mysql-server-5.0 (5.0.51a-24+lenny5) ... Stopping MySQL database server: mysqld. /var/lib/dpkg/info/mysql-server-5.0.postinst: line 144: /etc/mysql/conf.d/old_passwords.cnf: No such file or directory dpkg: error processing mysql-server-5.0 (--configure): subprocess post-installation script returned error exit status 1 Setting up mysql-client (5.0.51a-24+lenny5) ... dpkg: dependency problems prevent configuration of mysql-server: mysql-server depends on mysql-server-5.0; however: Package mysql-server-5.0 is not configured yet. dpkg: error processing mysql-server (--configure): dependency problems - leaving unconfigured Errors were encountered while processing: mysql-server-5.0 mysql-server E: Sub-process /usr/bin/dpkg returned an error code (1) Now I can't seem to figure out what to do. I just want to get a clean MySQL installation at this point. I'm running the latest stable release of Debian. All help is appreciated—thanks! Edit: I looked at this similar question, which suggests that I uninstall mysql-common, but when I try to do so I see: The following packages will be REMOVED: apache2 apache2-mpm-prefork apache2-utils apache2.2-common git-svn libapache2-mod-php5 libapache2-mod-python libapache2-svn libaprutil1 libdbd-mysql-perl libdbd-mysql-rubygem libmysql-ruby libmysql-ruby1.8 libmysql-rubygem libmysqlclient15-dev libmysqlclient15off librdf-perl librdf0 libserf-0-0 libsvn-perl libsvn1 mysql-client-5.0 mysql-common mytop ndn-apache22-php5 ndn-apache22-svn ndn-interpreters ndn-lighttpd ndn-netsaint-plugins ndn-perl-modules ndn-php5-cgi ndn-php5-xcache ndn-php53 ndn-php53-suhosin ndn-rubygems php5 php5-mcrypt php5-mysql proftpd proftpd-mod-mysql python-django python-mysqldb python-subversion python-svn subversion subversion-tools trac zendoptimizer 0 upgraded, 0 newly installed, 48 to remove and 1 not upgraded. Eeek! Any suggestions?

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  • Can't install MySQL

    - by James Marthenal
    I have a Debian machine that I have previously installed MySQL on. In an attempt to delete it, I stupidly deleted the directories/files /etc/mysql/, /etc/init.d/mysql, /usr/lib/mysql/, /var/lib/mysql/. I then later did sudo apt-get purge mysql-server mysql-server-5.0. Now, when I try to install mysql-server, I get: $ sudo apt-get install mysql-server Reading package lists... Done Building dependency tree Reading state information... Done The following extra packages will be installed: mysql-server-5.0 The following NEW packages will be installed: mysql-server mysql-server-5.0 0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded. Need to get 0B/27.4MB of archives. After this operation, 86.6MB of additional disk space will be used. Do you want to continue [Y/n]? y WARNING: The following packages cannot be authenticated! mysql-server-5.0 mysql-server Authentication warning overridden. Preconfiguring packages ... Can't exec "/tmp/mysql-server-5.0.config.122781": Permission denied at /usr/share/perl/5.10/IPC/Open3.pm line 168. open2: exec of /tmp/mysql-server-5.0.config.122781 configure failed at /usr/share/perl5/Debconf/ConfModule.pm line 59 mysql-server-5.0 failed to preconfigure, with exit status 255 Selecting previously deselected package mysql-server-5.0. (Reading database ... 158138 files and directories currently installed.) Unpacking mysql-server-5.0 (from .../mysql-server-5.0_5.0.51a-24+lenny5_amd64.deb) ... Selecting previously deselected package mysql-server. Unpacking mysql-server (from .../mysql-server_5.0.51a-24+lenny5_all.deb) ... Processing triggers for man-db ... Setting up mysql-server-5.0 (5.0.51a-24+lenny5) ... Stopping MySQL database server: mysqld. 110206 19:31:13 [ERROR] /usr/sbin/mysqld: Can't find file: './mysql/user.frm' (errno: 13) 110206 19:31:13 [ERROR] /usr/sbin/mysqld: Can't find file: './mysql/user.frm' (errno: 13) ERROR: 1017 Can't find file: './mysql/user.frm' (errno: 13) 110206 19:31:13 [ERROR] Aborting 110206 19:31:13 [Note] /usr/sbin/mysqld: Shutdown complete /etc/init.d/mysql: WARNING: /etc/mysql/my.cnf cannot be read. See README.Debian.gz (warning). Starting MySQL database server: mysqld . . . . . . . . . . . . . . failed! invoke-rc.d: initscript mysql, action "start" failed. dpkg: error processing mysql-server-5.0 (--configure): subprocess post-installation script returned error exit status 1 dpkg: dependency problems prevent configuration of mysql-server: mysql-server depends on mysql-server-5.0; however: Package mysql-server-5.0 is not configured yet. dpkg: error processing mysql-server (--configure): dependency problems - leaving unconfigured Errors were encountered while processing: mysql-server-5.0 mysql-server E: Sub-process /usr/bin/dpkg returned an error code (1) I have tried to search for a solution via Google and have found lots of suggestions for this problem, but ultimately it seems like the problem is that by deleting the files manually, I messed up the mysql-common package. I have tried to do sudo apt-get install --reinstall mysql-common followed by installing mysql-server, but it does the exact same thing. I previously had MySQL working great, I just want to get it back to that state. Thanks so much for your help.

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  • What are the pitfalls of hardlinked files on my desktop PC?

    - by MountainX
    All the identical-content files on my PC are now hardlinked. (My data is completely de-duplicated. It is a consequence of the way I copied my data from my old computer.) What pitfalls do I need to be aware of now that certain actions on one file could silently affect a number of other files? I know that deleting the file I'm working on is not a problem (assuming I deleted it on purpose). It doesn't affect any of the other hardlinked files and I don't see that the delete action would lead to unexpected side effects. Moving or renaming the file is not a problem. I don't see any unexpected consequences. I don't think copying hardlinked files is a problem, but I'm not as confident about any unexpected consequences in this regard. What I have seen is that making a copy (to the same disk) of a hardlinked file with cp keeps the copy hardlinked (i.e., inode number doesn't change in the copy). Copying to another filesystem obviously breaks the hardlink. (I guess one pitfall is forgetting this fact, given that my PC has 3 hard disks.) Changing permissions does affect all linked files. So far this has proven handy. (I made a large number of the hardlinked files read-only.) None of the operations above seem to produce any major unexpected consequences. However, as was pointed out to me by Daniel Beck in a comment, editing or modifying a file can sometimes be a problem. It depends on the tool and maybe the type of edit. (For example, editing small text files using sed seems to always break the link while using nano doesn't.) This introduces the chance that editing one file could affect all the hardlinked files (i.e., alter the original inode). My proposed solution to this is to make all hardlinked files read-only (and that is already mostly the case). If I can't do that for some files, I will unlink those particular files. Is there any problem with this read-only approach? I'm assuming that if I go to edit a file and find it to be read-only, I'll remember to unlink that filename while making it writable. So one pitfall might be forgetting this rule. In that case, I'll have to rely on my backups. Am I correct in the above statements? And what else do I need to know? BTW, I'm running Kubuntu 12.04. I'm also using btrfs. (I have 2 SSD's and 1 HDD in the PC. I will also be adding an external USB HDD. I'm also connected to a network and I mount some NFS shares. I don't assume any of these last bits are relevant to the question, but I'm adding them just in case.) BTW, since I have more than one drive (with separate file systems), to unlink any file all I have to do is copy it to another drive, then move it back. However, using sed also works (in my testing). Here's my script: sed -i 's/\(.\)/\1/' file1 Surprisingly, this even unlinks zero byte files. In my testing it also appears to work on non-text files without any special options. (But I understand that the --binary option might be needed on Windows, MS-DOS and Cygwin.) However, copying to another disk and moving back may be the best way to unlink. For my use-case, unlink command doesn't really "unlink", rather it "removes".

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  • Broken cups installation on a ubuntu server 64

    - by user67046
    Hi, I am having trouble with an cups installation. It seems to be in a broken state. When i try to reinstall it it stalls, the same if i try to remove it completely. I am running the server version 64 bit of Ubuntu 10.10 with kernel Linux version 2.6.35-22-server. When i try to start the cups daemon with the following command sudo service cups start It just stays there and nothing happens. I have tried to remove it, to be able to reinstall it, with the following command sudo apt-get purge cups It finally stalls with the following message Removing cups ... After that nothing happens. The process tree for the apt-get command looks like this. 1404 1404 1404 ? 00:00:00 sshd 26495 26495 26495 ? 00:00:00 sshd 26581 26495 26495 ? 00:00:00 sshd 26582 26582 26582 pts/4 00:00:00 bash 27158 27158 26582 pts/4 00:00:00 apt-get 27172 27172 27172 pts/2 00:00:00 dpkg 27176 27172 27172 pts/2 00:00:00 cups.prerm 27178 27172 27172 pts/2 00:00:00 stop I have tried to leave the process running for a while to see if i get any error messages but without success. To get out of it I have to kill the processes. sudo dpkg --configure cups dpkg: error processing cups (--configure): package cups is already installed and configured Errors were encountered while processing: cups sudo dpkg --status cups Package: cups Status: purge ok installed Priority: optional Section: net Installed-Size: 8292 Maintainer: Ubuntu Developers <[email protected]> Architecture: amd64 Version: 1.4.4-6ubuntu2.3 Replaces: cupsddk-drivers (<< 1.4.0) Provides: cupsddk-drivers Depends: libavahi-client3 (>= 0.6.16), libavahi-common3 (>= 0.6.16), libc6 (>= 2.7), libcups2 (>= 1.4.4-3~), libcupscgi1 (>= 1.4.2), libcupsdriver1 (>= 1.4.0), libcupsimage2 (>= 1.4.0), libcupsmime1 (>= 1.4.0), libcupsppdc1 (>= 1.4.0), libdbus-1-3 (>= 1.0.2), libgcc1 (>= 1:4.1.1), libgnutls26 (>= 2.7.14-0), libgssapi-krb5-2 (>= 1.8+dfsg), libijs-0.35, libkrb5-3 (>= 1.6.dfsg.2), libldap-2.4-2 (>= 2.4.7), libpam0g (>= 0.99.7.1), libpaper1, libpoppler7, libslp1, libstdc++6 (>= 4.1.1), libusb-0.1-4 (>= 2:0.1.12), zlib1g (>= 1:1.1.4), debconf (>= 1.2.9) | debconf-2.0, upstart-job, poppler-utils (>= 0.12), procps, ghostscript, lsb-base (>= 3), cups-common (>= 1.4.4), cups-client (>= 1.4.4-6ubuntu2.3), ssl-cert (>= 1.0.11), adduser, bc, ttf-freefont, cups-ppdc Recommends: foomatic-filters (>= 4.0), cups-driver-gutenprint, ghostscript-cups Suggests: cups-bsd, foomatic-db-compressed-ppds | foomatic-db, hplip, xpdf-korean | xpdf-japanese | xpdf-chinese-traditional | xpdf-chinese-simplified, cups-pdf, smbclient (>= 3.0.9), udev Breaks: foomatic-filters (<< 4.0) Conflicts: cupsddk-drivers (<< 1.4.0) Conffiles: /etc/fonts/conf.d/99pdftoopvp.conf a5221cfad70a981c80864229ef56586d /etc/logrotate.d/cups 5bb41fa9900f0d1c565954405a2bd7c4 /etc/default/cups 2b436fbb1a32b82b6aba45a76a1d7e40 /etc/pam.d/cups ff2488324854f7b1e892bb0df062d5f0 /etc/init/cups.conf 1a3cd022e8474e3d2b44640f33ce68e3 /etc/ufw/applications.d/cups 29e98a6d850da251e180c3d68dec2bd3 /etc/apparmor.d/usr.sbin.cupsd 60c4b26bfd5c033baa3dd48a3b2e9911 /etc/cups/cupsd.conf e2c7ec15835ea0939e5e86f7c6efcc03 /etc/cups/snmp.conf 2326a8af1e112676d55245bc5eb459ca /etc/cups/cupsd.conf.default a68d54d76021e857dd1d64edf57d36c5 Description: Common UNIX Printing System(tm) - server The Common UNIX Printing System (or CUPS(tm)) is a printing system and general replacement for lpd and the like. It supports the Internet Printing Protocol (IPP), and has its own filtering driver model for handling various document types. . This package provides the CUPS scheduler/daemon and related files. Original-Maintainer: Debian CUPS Maintainers <[email protected]> Would be greatful if someone could provide some help on how to solve this issue.

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  • Varnish cached 'MISS status' object?

    - by Hesey
    My site uses nginx, varnish, jboss. And some url will be cached by varnish, it depends a response header from jboss. The first time, jboss tells varnish doesn't cache this url. Then the second request, jboss tells varnish to cache, but varnish won't cache it. I used varnishstat and found that 1 object is cached in Varnish, is that the 'MISS status' object? I remove grace code and the problem still exists. When I PURGE this url, varnish works fine and cache the url then. But I can't PURGE so much urls every startup time, how can I fix this? The configuration: acl local { "localhost"; } backend default { .host = "localhost"; .port = "8080"; .probe = { .url = "/preload.htm"; .interval = 3s; .timeout = 1s; .window = 5; .threshold = 3; } } sub vcl_deliver { if (req.request == "PURGE") { remove resp.http.X-Varnish; remove resp.http.Via; remove resp.http.Age; remove resp.http.Content-Type; remove resp.http.Server; remove resp.http.Date; remove resp.http.Accept-Ranges; remove resp.http.Connection; set resp.http.keeplive="true"; } else { if (obj.hits > 0) { set resp.http.X-Cache = "HIT"; } else { set resp.http.X-Cache = "MISS"; } } } sub vcl_recv { if(req.url ~ "/check.htm"){ error 404 "N"; } if( req.http.host ~ "store." || req.request == "POST"){ return (pipe); } if (req.backend.healthy) { set req.grace = 30s; } else { set req.grace = 10m; } set req.http.x-cacheKey = "0"; if(req.url ~ "/shop/view_shop.htm" || req.url ~ "/shop/viewShop.htm" || req.url ~ "/index.htm"){ if(req.url ~ "search=y"){ set req.http.x-cacheKey = req.http.host + "/search.htm"; }else if(req.url !~ "bbs=y" && req.url !~ "shopIntro=y" && req.url !~ "shop_intro=y"){ set req.http.x-cacheKey = req.http.host + "/index.htm"; } }else if(req.url ~ "/search"){ set req.http.x-cacheKey = req.http.host + "/search.htm"; } if( req.http.x-cacheKey == "0" && req.url !~ "/i/"){ return (pipe); } if (req.request == "PURGE") { if (client.ip ~ local) { return (lookup); } else { error 405 "Not allowed."; } } if (req.url ~ "/i/") { set req.http.x-shop-url = req.original_url; }else { unset req.http.cookie; } } sub vcl_fetch { set beresp.grace = 10m; #unset beresp.http.x-cacheKey; if (req.url ~ "/i/" || req.url ~ "status" ){ set beresp.ttl = 0s; /* ttl=0 for dynamic content */ } else if(beresp.http.x-varnish-cache != "1"){ set beresp.do_esi = true; /* Do ESI processing */ set beresp.ttl = 0s; unset beresp.http.set-cookie; } else { set beresp.do_esi = true; /* Do ESI processing */ set beresp.ttl = 1800s; unset beresp.http.set-cookie; } } sub vcl_hash { hash_data(req.http.x-cacheKey); return (hash); } sub vcl_error { if (req.request == "PURGE") { return (deliver); } else { set obj.http.Content-Type = "text/html; charset=gbk"; synthetic {"<!--ve-->"}; return (deliver); } } sub vcl_hit { if (req.request == "PURGE") { set obj.ttl = 0s; error 200 "Purged."; } } sub vcl_miss { if (req.request == "PURGE") { error 404 "N"; } }

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