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• Erlang, SSH and authorized_keys

  - by Roberto Aloi

  Playing with the ssh and public_key application in Erlang, I've discovered a nice feature. I was trying to connect to my running Erlang SSH daemon by using a rsa key, but the authentication was failing and I was prompted for a password. After some debugging and tracing (and a couple of coffees), I've realized that, for some weird reason, a non valid key for my user was there. The authorized_keys file contained two keys. The wrong one was at some point in the file, while the correct one was appended at the end of the file. Now, the Erlang SSH application, when diffing the provided key with the ones contained in the authorized_keys, it was finding the first entry (completely ignoring the second on - the correct one). Then, it was switching to different authentication mechanism (at first it was trying dsa instead of rsa and then it was prompting for a password). The question is: Is this behavior intended or should the SSH server check for multiple entries for the same user in the *authorized_keys* file? Is this a generic SSH behaviour or it's just specific to the Erlang implementation?

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• Setting style on first and last visible TabItem of TabControl

  - by Donnelle

  I want to set a style on the first and last TabItems in a TabControl, and have them updated as the visibility of the TabItems is changed. I can't see a way to do so with triggers. What we're after looks like this: | | And the visibility of TabItems are determined by binding. I do have it working in code. On TabItem visibility changed, enumerate through TabItems until you find the first visible one. Set the style on that one. For all other visible TabItems, set them to the pointy style (so that the previously first visible one is now pointy). Then start from the end until you find a visible TabItem and set the last style on that one. (This also lets us address an issue with TabControl where it will display the content of a non-visible TabItem if none of the visible TabItems are selected.) There's undoubtably improvements I could make to my method, but I'm not convinced that it IS the right approach. How would you approach this?

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• Elegantly handling constraint violations in EJB/JPA environment?

  - by hallidave

  I'm working with EJB and JPA on a Glassfish v3 app server. I have an Entity class where I'm forcing one of the fields to be unique with a @Column annotation. @Entity public class MyEntity implements Serializable { private String uniqueName; public MyEntity() { } @Column(unique = true, nullable = false) public String getUniqueName() { return uniqueName; } public void setUniqueName(String uniqueName) { this.uniqueName = uniqueName; } } When I try to persist an object with this field set to a non-unique value I get an exception (as expected) when the transaction managed by the EJB container commits. I have two problems I'd like to solve: 1) The exception I get is the unhelpful "javax.ejb.EJBException: Transaction aborted". If I recursively call getCause() enough times, I eventually reach the more useful "java.sql.SQLIntegrityConstraintViolationException", but this exception is part of the EclipseLink implementation and I'm not really comfortable relying on it's existence. Is there a better way to get detailed error information with JPA? 2) The EJB container insists on logging this error even though I catch it and handle it. Is there a better way to handle this error which will stop Glassfish from cluttering up my logs with useless exception information? Thanks.

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• Kerberos and/or other authentication systems - One time logon for all PHP scripts

  - by devviedev

  I'm managing a set of web apps, almost exclusively written in PHP, and would like to find an authentication platform to build a role-based authorization system on top of. Also, I'd like the authentication system to be extensible to use for, for example, system services (SSH, etc.) Here are some of the main characteristics I'm looking for, in order of importance: Easy PHP implementation (storing/reading easily roles, etc.). Redundant, if possible. If an auth system goes down everyone is not locked out. Has clients for Windows and Mac. Easy web-based administration (adding/removing users/roles, changing passwords). If not, I can build an administration system without too much effort. One-time log on. I'd also like, when an auth token is issued, to store the user's IP address and use that to authorize the user for some non web-based applications. For that reason, I'd like a desktop client to issue the token and revoke tokens when, for example, the user becomes idle at their workstation. I'm thinking Kerberos might be a solution, but what are other options?

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• Using MD5 to generate an encryption key from password?

  - by Charles

  I'm writing a simple program for file encryption. Mostly as an academic exercise but possibly for future serious use. All of the heavy lifting is done with third-party libraries, but putting the pieces together in a secure manner is still quite a challenge for the non-cryptographer. Basically, I've got just about everything working the way I think it should. I'm using 128-bit AES for the encryption with a 128-bit key length. I want users to be able to enter in variable-length passwords, so I decided to hash the password with MD5 and then use the hash as the key. I figured this was acceptable--the key is always supposed to be a secret, so there's no reason to worry about collision attacks. Now that I've implemented this, I ran across a couple articles indicating that this is a bad idea. My question is: why? If a good password is chosen, the cipher is supposed to be strong enough on its own to never reveal the key except via an extraordinary (read: currently infeasible) brute-force effort, right? Should I be using something like PBKDF2 to generate the key or is that just overkill for all but the most extreme cryptographic applications?

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• Blocking on DBCP connection pool (open and close connnection). Is database connection pooling in OpenEJB pluggable?

  - by topchef

  We use OpenEJB on Tomcat (used to run on JBoss, Weblogic, etc.). While running load tests we experience significant performance problems with handling JMS messages (queues). Problem was localized to blocking on database connection pool getting or releasing connection to the pool. Blocking prevented concurrent MDB instances (threads) from running hence performance suffered 10-fold and worse. The same code used to run on application servers (with their respective connection pool implementations) with no blocking at all. Example of thread blocked: Name: JMS Resource Adapter-worker-23 State: BLOCKED on org.apache.commons.pool.impl.GenericObjectPool@1ea6b4a owned by: JMS Resource Adapter-worker-19 Total blocked: 18,426 Total waited: 0 Stack trace: org.apache.commons.pool.impl.GenericObjectPool.returnObject(GenericObjectPool.java:916) org.apache.commons.dbcp.PoolableConnection.close(PoolableConnection.java:91) - locked org.apache.commons.dbcp.PoolableConnection@1bcba8 org.apache.commons.dbcp.managed.ManagedConnection.close(ManagedConnection.java:147) com.xxxxx.persistence.DbHelper.closeConnection(DbHelper.java:290) .... Couple of questions. I am almost certain that some transactional attributes and properties contribute to this blocking, but MDBs are defined as non-transactional (we use both annotations and ejb-jar.xml). Some EJBs do use container-managed transactions though (and we can observe blocking there as well). Are there any DBCP configurations that may fix blocking? Is DBCP connection pool implementation replaceable in OpenEJB? How easy (difficult) to replace it with another library? Just in case this is how we define data source in OpenEJB (openejb.xml): <Resource id="MyDataSource" type="DataSource"> JdbcDriver oracle.jdbc.driver.OracleDriver JdbcUrl ${oracle.jdbc} UserName ${oracle.user} Password ${oracle.password} JtaManaged true InitialSize 5 MaxActive 30 ValidationQuery SELECT 1 FROM DUAL TestOnBorrow true </Resource>

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• Add new types to Go

  - by nevalu

  I'm trying add new types for that been managed/used as in Go core types. To create new types is anything very interesting to validate data before of send it to a non-SQL DBMS or to check data from a form. Go uses univeral constants to define them at global level: var DateType = universe.DefineType("date", universePos, &dateType{}) In this case they're defined to be called from a package like types: var Date = &dateType{} I get these errors: test.go:58: o.lit undefined (cannot refer to unexported field lit) test.go:62: *dateType is not Type missing Pos() token.Position The code is based on: http://github.com/tav/go/blob/master/src/pkg/exp/eval/value.go http://github.com/tav/go/blob/master/src/pkg/exp/eval/type.go package main import ( "exp/eval" "fmt" // "go/token" ) // http://github.com/tav/go/blob/master/src/pkg/exp/eval/value.go type DateValue interface { eval.Value Get(*eval.Thread) string Set(*eval.Thread, string) } /* Date */ type dateV string func (v *dateV) String() string { return fmt.Sprint(*v) } func (v *dateV) Assign(t *eval.Thread, o eval.Value) { *v = dateV(o.(DateValue).Get(t)) } func (v *dateV) Get(*eval.Thread) string { return string(*v) } func (v *dateV) Set(t *eval.Thread, x string) { *v = dateV(x) } // http://github.com/tav/go/blob/master/src/pkg/exp/eval/type.go type Type interface { eval.Type // isDate returns true if this is a date type. isDate() bool } /* Common type */ type commonType struct{} // added func (commonType) isDate() bool { return false } /* Date */ type dateType struct { commonType } // * It should not be an universal constant //var universePos = token.Position{"<universe>", 0, 0, 0} // added //var DateType = universe.DefineType("date", universePos, &dateType{}) var Date = &dateType{} func (t *dateType) compat(o Type, conv bool) bool { t2, ok := o.lit().(*dateType) return ok && t == t2 } func (t *dateType) lit() Type { return t } func (t *dateType) isDate() bool { return true } func (t *dateType) String() string { return "<date>" } func (t *dateType) Zero() eval.Value { res := dateV("") return &res } /* Named types */ /* type NamedType struct { eval.NamedType Def Type }*/ type NamedType struct { // added // token.Position Name string // Underlying type. If incomplete is true, this will be nil. // If incomplete is false and this is still nil, then this is // a placeholder type representing an error. Def Type // True while this type is being defined. incomplete bool methods map[string]eval.Method } func (t *NamedType) isDate() bool { return t.Def.isDate() } /* *********************** */ func main() { print("foo") }

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• How to access this data in PHP?

  - by George Edison

  Okay. Now I give up. I have been playing with this for hours. I have a variable name $data. The variable contains these contents: array ( 'headers' => array ( 'content-type' => 'multipart/alternative; boundary="_689e1a7d-7a0a-442a-bd6c-a1fb1dc2993e_"', ), 'ctype_parameters' => array ( 'boundary' => '_689e1a7d-7a0a-442a-bd6c-a1fb1dc2993e_', ), 'parts' => array ( 0 => stdClass::__set_state(array( 'headers' => array ( 'content-type' => 'text/plain; charset="iso-8859-1"', 'content-transfer-encoding' => 'quoted-printable', ), 'ctype_primary' => 'text', )), ), ) I removed some non-essential data. I want to access the headers value (on the second line above) - simple: $data->headers I want to access the headers value (on the fourteenth line after the stdClass:: stuff) - how? How can I possibly access the values within the stdClass::__set_state section? I tried var_export($data->parts); but all I get is NULL

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• Tips on managing dependencies for a release?

  - by Andrew Murray

  Our system comprises many .NET websites, class libraries, and a MSSQL database. We use SVN for source control and TeamCity to automatically build to a Test server. Our team is normally working on 4 or 5 projects at a time. We try to lump many changes into a largish rollout every 2-4 weeks. My problem is with keeping track of all the dependencies for a rollout. Example: Website A cannot go live until we've rolled out Branch X of Class library B, built in turn against the Trunk of Class library C, which needs Config Updates Y and Z and Database Update D, which needs Migration Script E... It gets even more complex - like making sure each developer's project is actually compatible with the others and are building against the same versions. Yes, this is a management issue as much as a technical issue. Currently our non-optimal solution is: a whiteboard listing features that haven't gone live yet relying on our memory and intuition when planning the rollout, until we're pretty sure we've thought of everything... a dry-run on our Staging environment. It's a good indication but we're often not sure if Staging is 100% in sync with Live - part of the problem I'm hoping to solve. some amount of winging it on rollout day. So far so good, minus a few close calls. But as our system grows, I'd like a more scientific release management system allowing for more flexibility, like being able to roll out a single change or bugfix on it's own, safe in the knowledge that it won't break anything else. I'm guessing the best solution involves some sort of version numbering system, and perhaps using a project management tool. We're a start-up, so we're not too hot on religiously sticking to rigid processes, but we're happy to start, providing it doesn't add more overhead than it's worth. I'd love to hear advice from other teams who have solved this problem.

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• Which PHP library I should choose to work with CouchDB?

  - by Guss

  I want to try playing with CouchDB for a new project I'm writing (as a hobby, not part of my job). I'm well versed in PHP, but I haven't programmed with CouchDB at all, and also I have little experience with non-SQL databases. From looking at CouchDB's "Getting Started with PHP" document they recommend using a third-party library or writing your own client using their RESTful HTTP API. I think I'd rather not mess with writing protocol implementations myself at this point, but what is your experience with writing PHP to work with CouchDB? I haven't tested any of the alternatives yet, but I looked at: PHPillow : I'm interested in the way they implement ORM. I wasn't planning to do ORM, but my problem domain probably map well to that method. PHP Object Freezer: seems like a poor man's ORM - I can use it to implement an actual ORM, or just as an easy store/retrieve document API but it seems too primitive. PHP-on-Couch : Also a bit simple, but they have an interesting API for views and from the documentation it looks usable enough. PHP CouchDB Extension : From the listed options this looks like it has the best chance of making it into the PHP mainline itself, and also has the most complete API. Any opinion one wish to share on each library is welcome.

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• EPIPE blocks server

  - by timn

  I have written a single-threaded asynchronous server in C running on Linux: The socket is non-blocking and as for polling, I am using epoll. Benchmarks show that the server performs fine and according to Valgrind, there are no memory leaks or other problems. The only problem is that when a write() command is interrupted (because the client closed the connection), the server will encounter a SIGPIPE. I am doing the interrupted artifically by running the benchmarking utility "siege" with the parameter -b. It does lots of requests in a row which all work perfectly. Now I press CTRL-C and restart the "siege". Sometimes I am lucky and the server does not manage to send the full response because the client's fd is invalid. As expected errno is set to EPIPE. I handle this situation, execute close() on the fd and then free the memory related to the connection. Now the problem is that the server blocks and does not answer properly anymore. Here is the strace output: accept(3, {sa_family=AF_INET, sin_port=htons(50611), sin_addr=inet_addr("127.0.0.1")}, [16]) = 5 fcntl64(5, F_GETFD) = 0 fcntl64(5, F_SETFL, O_RDONLY|O_NONBLOCK) = 0 epoll_ctl(4, EPOLL_CTL_ADD, 5, {EPOLLIN|EPOLLERR|EPOLLHUP|EPOLLET, {u32=158310248, u64=158310248}}) = 0 epoll_wait(4, {{EPOLLIN, {u32=158310248, u64=158310248}}}, 128, -1) = 1 read(5, "GET /user/register HTTP/1.1\r\nHos"..., 4096) = 161 write(5, "HTTP/1.1 200 OK\r\nContent-Type: t"..., 106) = 106 <<<<< write(5, "00001000\r\n", 10) = -1 EPIPE (Broken pipe) <<<<< Why did the previous write() work fine but not this one? --- SIGPIPE (Broken pipe) @ 0 (0) --- As you can see, the client establishes a new connection which consequently is accepted. Then, it's added to the EPOLL queue. epoll_wait() signalises that the client sent data (EPOLLIN). The request is parsed and and a response is composed. Sending the headers works fine but when it comes to the body, write() results in an EPIPE. It is not a bug in "siege" because it blocks any incoming connections, no matter from which client.

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• scheme struct question

  - by qzar

  ;; definition of the structure "book" ;; author: string - the author of the book ;; title: string - the title of the book ;; genre: symbol - the genre (define-struct book (author title genre)) (define lotr1 (make-book "John R. R. Tolkien" "The Fellowship of the Ring" 'Fantasy)) (define glory (make-book "David Brin" "Glory Season" 'ScienceFiction)) (define firstFamily (make-book "David Baldacci" "First Family" 'Thriller)) (define some-books (list lotr1 glory firstFamily)) ;; count-books-for-genre: symbol (list of books) -> number ;; the procedure takes a symbol and a list of books and produces the number ;; of books from the given symbol and genre ;; example: (count-books-for-genre 'Fantasy some-books) should produce 1 (define (count-books-for-genre genre lob) (if (empty? lob) 0 (if (symbol=? (book-genre (first lob)) genre) (+ 1 (count-books-for-genre (rest lob) genre)) (count-books-for-genre (rest lob) genre) ) ) ) (count-books-for-genre 'Fantasy some-books) It produce following exception first: expected argument of type non-empty list; given 'Fantasy, I don't understand whats the problem. Can somebody give me some explanation ? Thank you very much !

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• Testing a wide variety of computers with a small company

  - by Tom the Junglist

  Hello everyone, I work for a small dotcom which will soon be launching a reasonably-complicated Windows program. We have uncovered a number of "WTF?" type scenarios that have turned up as the program has been passed around to the various not-technical-types that we've been unable to replicate. One of the biggest problems we're facing is that of testing: there are a total of three programmers -- only one working on this particular project, me -- no testers, and a handful of assorted other staff (sales, etc). We are also geographically isolated. The "testing lab" consists of a handful of VMWare and VPC images running sort-of fresh installs of Windows XP and Vista, which runs on my personal computer. The non-technical types try to be helpful when problems arise, we have trained them on how to most effectively report problems, and the software itself sports a wide array of diagnostic features, but since they aren't computer nerds like us their reporting is only so useful, and arranging remote control sessions to dig into the guts of their computers is time-consuming. I am looking for resources that allow us to amplify our testing abilities without having to put together an actual lab and hire beta testers. My boss mentioned rental VPS services and asked me to look in to them, however they are still largely very much self-service and I was wondering if there were any better ways. How have you, or any other companies in a similar situation handled this sort of thing? EDIT: According to the lingo, our goal here is to expand our systems testing capacity via an elastic computing platform such as Amazon EC2. At this point I am not sure suggestions of beefing up our unit/integration testing are going to help very much as we are consistently hitting walls at the systems testing phase. Has anyone attempted to do this kind of software testing on a cloud-type service like EC2? Tom

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• Providing File permissions in Installshield

  - by Pawan Kumar

  I have created an installer in Installshield X. I want to give 'write permissions' to few files when the installation is done in Non-Admin Windows accounts ( by default it will have only 'read' permission). If I select individual file and go to properties (inside Installshield),i have permissions tab where they have provided options like Domain , Readonly, Full Control, Modify etc. I have tested these options but it doesn't effect the msi file.(specific files doesn't have write permission). Is there something wrong I am doing? There is another way of doing this, writing the script Set objShell=CreateObject("WScript.Shell") installDir = Session.Property("INSTALLDIR.5A884667_3CC4_41EC_B0F2_BEEAB457BB8C") supportDir = Session.Property("SUPPORTDIR") length = Len(installDir) lastChar = Right(installDir, 1) if (lastChar = "\") Then installDir = Left(installDir, length - 1) end if 'MsgBox supportDir & "\setacl.exe """ & installDir & """ /dir /set S-1-5-32-545 /full /p:yes /sid /silent" objshell.Run supportDir & "\setacl.exe """ & installDir & """ /dir /set S-1-5-32-545 /full /p:yes /sid /silent",0,true Can someone please explain me what is going on here? those last set s-1-5-32-545. Thanks

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• Does JAXWS client make difference between an empty collection and a null collection value as returne

  - by snowflake

  Since JAX-WS rely on JAXB, and since I observed the code that unpack the XML bean in JAX-B Reference Implementation, I guess the difference is not made and that a JAXWS client always return an empty collection, even the webservice result was a null element: public T startPacking(BeanT bean, Accessor<BeanT, T> acc) throws AccessorException { T collection = acc.get(bean); if(collection==null) { collection = ClassFactory.create(implClass); if(!acc.isAdapted()) acc.set(bean,collection); } collection.clear(); return collection; } I agree that for best interoperability service contracts should be non ambiguous and avoid such differences, but it seems that the JAX-WS service I'm invoking (hosted on a Jboss server with Jbossws implementation) is returning as expected either null either empty collection (tested with SoapUI). I used for my test code generated by wsimport. Return element is defined as: @XmlElement(name = "return", nillable = true) protected List<String> _return; I even tested to change the Response class getReturn method from : public List<String> getReturn() { if (_return == null) { _return = new ArrayList<String>(); } return this._return; } to public List<String> getReturn() { return this._return; } but without success. Any helpful information/comment regarding this problem is welcome !

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• Getting minimum - Min() - for DateTime column in a DataTable using LINQ to DataSets?

  - by Jay Stevens

  I need to get the minimum DateTime value of a column in a DataTable. The DataTable is generated dynamically from a CSV file, therefore I don't know the name of that column until runtime. Here is code I've got that doesn't work... private DateTime GetStartDateFromCSV(string inputFile, string date_attr) { EnumerableRowCollection<DataRow> table = CsvStreamReader.GetDataTableFromCSV(inputFile, "input", true).AsEnumerable(); DateTime dt = table.Select(record => record.Field<DateTime>(date_attr)).Min(); return dt; } The variable table is broken out just for clarity. I basically need to find the minimum value as a DateTime for one of the columns (to be chosen at runtime and represented by date_attr). I have tried several solutions from SO (most deal with known columns and/or non-DateTime fields). What I've got throws an error at runtime telling me that it can't do the DateTime conversion (that seems to be a problem with Linq?) I've confirmed that the data for the column name that is in the string date_attr is a date value.

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• Declaration of arrays before "normal" variables in c?

  - by bjarkef

  Hi We are currently developing an application for a msp430 MCU, and are running into some weird problems. We discovered that declaring arrays withing a scope after declaration of "normal" variables, sometimes causes what seems to be undefined behavior. Like this: foo(int a, int *b); int main(void) { int x = 2; int arr[5]; foo(x, arr); return 0; } foo sometimes is passed a pointer as the second variable, that does not point to the arr array. We verify this by single stepping through the program, and see that the value of the arr variable in the main scope is not the same as the value of the b pointer variable in the foo scope. And no, this is not really reproduceable, we have just observed this behavior once in a while. Changing the example seems to solve the problem, like this: foo(int a, int *b); int main(void) { int arr[5]; int x = 2; foo(x, arr); return 0; } Does anybody have any input or hints as to why we experience this behavior? Or similar experiences? The MSP430 programming guide specifies that code should conform to the ANSI C89 spec. and so I was wondering if it says that arrays has to be declared before non-array variables? Any input on this would be appreciated.

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• suggestions for a 3D graph rendering library?

  - by Sandro

  Hello coders! So I'm not sure how stackoverflow friendly this question is since it doesn't have a quick clear cut answer but here we go... I have a java program that generates data for a directed graph. Now I need to render this graph. The data needs to be laid out in 3D, and I want to be able to define which plane an edge lives in. (Each edge will only need to occupy 1 plane of the 3D space). I also need the ability to navigate around the graph. Since I know that this kind of stuff is hard, I'm going shopping. So far I've looked into (In no particular order): JUNG: lacks 3D support Cytoscape: not sure how much I'll be able to define edge drawing, haven't seen a non bio-informatics application of it yet JGraph: I didn't see any 3D applications yet Perfuse: looks promising, does anyone know anything else about it? Gephi: Documentation looks scarce Processing: does this play well with java? I'm also considering doing some combination of opengl + swing rendering to create a 3D graph from multiple 2D graphs. I am also not adverse to the idea of linking from another language Any Ideas? Thank you.

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• What is the point of the logical operators in C?

  - by reubensammut

  I was just wondering if there is an XOR logical operator in C (something like && for AND but for XOR). I know I can split an XOR into ANDs, NOTs and ORs but a simple XOR would be much better. Then it occurred to me that if I use the normal XOR bitwise operator between two conditions, it might just work. And for my tests it did. Consider: int i = 3; int j = 7; int k = 8; Just for the sake of this rather stupid example, if I need k to be either greater than i or greater than j but not both, XOR would be quite handy. if ((k > i) XOR (k > j)) printf("Valid"); else printf("Invalid"); or printf("%s",((k > i) XOR (k > j)) ? "Valid" : "Invalid"); I put the bitwise XOR ^ and it produced "Invalid". Putting the results of the two comparisons in two integers resulted in the 2 integers to contain a 1, hence the XOR produced a false. I've then tried it with the & and | bitwise operators and both gave the expected results. All this makes sense knowing that true conditions have a non zero value, whilst false conditions have zero values. I was wondering, is there a reason to use the logical && and || when the bitwise operators &, | and ^ work just the same? Thanks Reuben

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• Printing an invisible NSView

  - by Rodger Wilson

  Initially I created a simple program with a custom NSView. I drew a picture (certificate) and printed it! beautiful! Everything worked great! I them moved my custom NSView to an existing application. My hope was that when a user hit print it would print this certificate. Simple enough. I figured a could have a NSView pointer in my controller code. Then at initialization I would populate the pointer. Then when someone wanted to print the certificate it would print. The problem is that all of my drawing code is in the "drawRect" method. This method doesn't get called because this view is never displayed in a window. I have heart that others use non-visible NSView objects just for printing. What do I need to do. I really don't want to show this view to the screen. Rodger

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• Why is it assumed that send may return with less than requested data transmitted on a blocking socke

  - by Ernelli

  The standard method to send data on a stream socket has always been to call send with a chunk of data to write, check the return value to see if all data was sent and then keep calling send again until the whole message has been accepted. For example this is a simple example of a common scheme: int send_all(int sock, unsigned char *buffer, int len) { int nsent; while(len 0) { nsent = send(sock, buffer, len, 0); if(nsent == -1) // error return -1; buffer += nsent; len -= nsent; } return 0; // ok, all data sent } Even the BSD manpage mentions that ...If no messages space is available at the socket to hold the message to be transmitted, then send() normally blocks... Which indicates that we should assume that send may return without sending all data. Now I find this rather broken but even W. Richard Stevens assumes this in his standard reference book about network programming, not in the beginning chapters, but the more advanced examples uses his own writen (write all data) function instead of calling write. Now I consider this still to be more or less broken, since if send is not able to transmit all data or accept the data in the underlying buffer and the socket is blocking, then send should block and return when the whole send request has been accepted. I mean, in the code example above, what will happen if send returns with less data sent is that it will be called right again with a new request. What has changed since last call? At max a few hundred CPU cycles have passed so the buffer is still full. If send now accepts the data why could'nt it accept it before? Otherwise we will end upp with an inefficient loop where we are trying to send data on a socket that cannot accept data and keep trying, or else? So it seems like the workaround, if needed, results in heavily inefficient code and in those circumstances blocking sockets should be avoided at all an non blocking sockets together with select should be used instead.

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• Where are the real risks in network security?

  - by Barry Brown

  Anytime a username/password authentication is used, the common wisdom is to protect the transport of that data using encryption (SSL, HTTPS, etc). But that leaves the end points potentially vulnerable. Realistically, which is at greater risk of intrusion? Transport layer: Compromised via wireless packet sniffing, malicious wiretapping, etc. Transport devices: Risks include ISPs and Internet backbone operators sniffing data. End-user device: Vulnerable to spyware, key loggers, shoulder surfing, and so forth. Remote server: Many uncontrollable vulnerabilities including malicious operators, break-ins resulting in stolen data, physically heisting servers, backups kept in insecure places, and much more. My gut reaction is that although the transport layer is relatively easy to protect via SSL, the risks in the other areas are much, much greater, especially at the end points. For example, at home my computer connects directly to my router; from there it goes straight to my ISPs routers and onto the Internet. I would estimate the risks at the transport level (both software and hardware) at low to non-existant. But what security does the server I'm connected to have? Have they been hacked into? Is the operator collecting usernames and passwords, knowing that most people use the same information at other websites? Likewise, has my computer been compromised by malware? Those seem like much greater risks. What do you think?

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• PHPUnit and autoloaders: Determining whether code is running in test-scope?

  - by pinkgothic

  Premise I know that writing code to act differently when a test is run is hilariously bad practise, but I may've actually come across a scenario in which it may be necessary. Specifically, I'm trying to test a very specific wrapper for HTML Purifier in the Zend framework - a View Helper, to be exact. The HTML Purifier autoloader is necessary because it uses a different logic to the autoloaders we otherwise have. Problem require()-ing the autoloader at the top of my View Helper class, gives me the following in test-scope: HTML Purifier autoloader registrar is not compatible with non-static object methods due to PHP Bug #44144; Please do not use HTMLPurifier.autoload.php (or any file that includes this file); instead, place the code: spl_autoload_register(array('HTMLPurifier_Bootstrap', 'autoload')) after your own autoloaders. Replacing the require() with spl_autoload_register(array('HTMLPurifier_Bootstrap', 'autoload')) as advertised means the test runs fine, but the View Helper dies a terrible death claiming: Zend_Log[3707]: ErrorController caught LogicException "Passed array does not specify an existing static method (class 'HTMLPurifier_Bootstrap' not found)" (Our test folder structure is slightly different to our Zend folder structure by necessity.) Question(s) After tinkering with it, I'm thinking I'll need to pick an autoloader-loading depending on whether things are in the test scope or not. Do I have another option to include HTMLPurifier's autoloading routine in both cases that I'm not seeing due to tunnel vision? If not, do I have to find a means to differentiate between test-environment and production-environment this with my own code (e.g. APPLICATION_ENV) - or does PHPUnit support this godawful hackery of mine natively by setting a constant that I could check whether its been defined(), or similar shenanigans? (My Google-fu here is weak! I'm probably just doing it wrong.)

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• Does NHibernate LINQ support ToLower() in Where() clauses?

  - by Daniel T.

  I have an entity and its mapping: public class Test { public virtual int Id { get; set; } public virtual string Name { get; set; } public virtual string Description { get; set; } } public class TestMap : EntityMap<Test> { public TestMap() { Id(x => x.Id); Map(x => x.Name); Map(x => x.Description); } } I'm trying to run a query on it (to grab it out of the database): var keyword = "test" // this is coming in from the user keyword = keyword.ToLower(); // convert it to all lower-case var results = session.Linq<Test> .Where(x => x.Name.ToLower().Contains(keyword)); results.Count(); // execute the query However, whenever I run this query, I get the following exception: Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index Am I right when I say that, currently, Linq to NHibernate does not support ToLower()? And if so, is there an alternative that allows me to search for a string in the middle of another string that Linq to NHibernate is compatible with? For example, if the user searches for kap, I need it to match Kapiolani, Makapuu, and Lapkap.

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• average case running time of linear search algorithm

  - by Brahadeesh

  Hi all. I am trying to derive the average case running time for deterministic linear search algorithm. The algorithm searches an element x in an unsorted array A in the order A[1], A[2], A[3]...A[n]. It stops when it finds the element x or proceeds until it reaches the end of the array. I searched on wikipedia and the answer given was (n+1)/(k+1) where k is the number of times x is present in the array. I approached in another way and am getting a different answer. Can anyone please give me the correct proof and also let me know whats wrong with my method? E(T)= 1*P(1) + 2*P(2) + 3*P(3) ....+ n*P(n) where P(i) is the probability that the algorithm runs for 'i' time (i.e. compares 'i' elements). P(i)= (n-i)C(k-1) * (n-k)! / n! Here, (n-i)C(k-1) is (n-i) Choose (k-1). As the algorithm has reached the ith step, the rest of k-1 x's must be in the last n-i elements. Hence (n-i)C(k-i). (n-k)! is the total number of ways of arranging the rest non x numbers, and n! is the total number of ways of arranging the n elements in the array. I am not getting (n+1)/(k+1) on simplifying.

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