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• ssh_exchange_identification: Connection closed by remote host under Git bash

  - by MoreFreeze

  I work at win7 and set up git server with sshd. I git --bare init myapp.git, and clone ssh://git@localhost/home/git/myapp.git in Cywgin correctly. But I need config git of Cygwin again, I want to git clone in Git Bash. I run "git clone ssh://git@localhost/home/git/myapp.git" and get following message ssh_exchange_identification: Connection closed by remote host then I run "ssh -vvv git@localhost" in Git Bash and get message debug2: ssh_connect: needpriv 0 debug1: Connecting to localhost [127.0.0.1] port 22. debug1: Connection established. debug1: identity file /c/Users/MoreFreeze/.ssh/identity type -1 debug3: Not a RSA1 key file /c/Users/MoreFreeze/.ssh/id_rsa. debug2: key_type_from_name: unknown key type '-----BEGIN' debug3: key_read: missing keytype debug3: key_read: missing whitespace // above it repeats 24 times debug2: key_type_from_name: unknown key type '-----END' debug3: key_read: missing keytype debug1: identity file /c/Users/MoreFreeze/.ssh/id_rsa type 1 debug1: identity file /c/Users/MoreFreeze/.ssh/id_dsa type -1 ssh_exchange_identification: Connection closed by remote host it seems my private keys has wrong format? And I find that there are exactly 25 line in private keys without "BEGIN" and "END". I'm confused why it said NOT RSA1 key, I totally ensure it is RSA 2 key. Any advises are welcome. btw, I have read first 3 pages on google about this problem.

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• PHP: How to copy elements from an associative array and place them at the beginning of the array?

  - by Andrew

  I have an array of countries that I will be using in a select menu: array( [0] => " -- Select -- " [1] => "Afghanistan" [3] => "Albania" [4] => "Algeria" [39] => "Canada" [47] => "USA" ) //etc... I want to copy create copies of the Canada and USA entries and place them at the front of my array. So the array should end up looking like this: array( [0] => " -- Select -- " [47] => "USA" [39] => "Canada" [1] => "Afghanistan" [3] => "Albania" [4] => "Algeria" [39] => "Canada" [47] => "USA" ) //etc... The array keys correspond to their ID in the database, so I can't change the keys. How can I achieve this?

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• object datasource problems in visual studio 2008,

  - by kamal

  After going to the process of adding the various attributes like insert,delete and update.But when i run it through the browser ,editing works but updating and deleting doesn't !(for the update and shows the same thing for delete,my friends think i need to use codes to repair the problems,can you help me please.it shows this: Server Error in '/WebSite3' Application. ObjectDataSource 'ObjectDataSource1' could not find a non-generic method 'Update' that has parameters: First_name, Surname, Original_author_id, First name, original_author id. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.InvalidOperationException: ObjectDataSource 'ObjectDataSource1' could not find a non-generic method 'Update' that has parameters: First_name, Surname, Original_author_id, First name, original_author id. Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Stack Trace: [InvalidOperationException: ObjectDataSource 'ObjectDataSource1' could not find a non-generic method 'Update' that has parameters: First_name, Surname, Original_author_id, First name, original_author id.] System.Web.UI.WebControls.ObjectDataSourceView.GetResolvedMethodData(Type type, String methodName, IDictionary allParameters, DataSourceOperation operation) +1119426 System.Web.UI.WebControls.ObjectDataSourceView.ExecuteUpdate(IDictionary keys, IDictionary values, IDictionary oldValues) +1008 System.Web.UI.DataSourceView.Update(IDictionary keys, IDictionary values, IDictionary oldValues, DataSourceViewOperationCallback callback) +92 System.Web.UI.WebControls.GridView.HandleUpdate(GridViewRow row, Int32 rowIndex, Boolean causesValidation) +907 System.Web.UI.WebControls.GridView.HandleEvent(EventArgs e, Boolean causesValidation, String validationGroup) +704 System.Web.UI.WebControls.GridView.OnBubbleEvent(Object source, EventArgs e) +95 System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +37 System.Web.UI.WebControls.GridViewRow.OnBubbleEvent(Object source, EventArgs e) +123 System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +37 System.Web.UI.WebControls.LinkButton.OnCommand(CommandEventArgs e) +118

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• Java many to many association map

  - by Raphael Jolivet

  Hi, I have to classes, ClassA and ClassB and a "many to many" AssociationClass. I want to use a structure to hold the associations between A and B such as I can know, for each instance of A or B, which are their counterparts. I thought of using a Hashmap, with pair keys: Hasmap<Pair<ClassA, ClassB>, AssociationClass> associations; This way, I can add and remove an association between two instances of ClassA and ClassB, and I can query a relation for two given instances. However, I miss the feature of getting all associations defined for a given instance of ClassA or ClassB. I could do it by brute force and loop over all keys of the map to search for associations between a given instance, but this is inefficient and not elegant. Do you know of any data structure / free library that enables this ? I don't want to reinvent the wheel. Thanks in advance for your help, Raphael NB: This is not a "database" question. These objects are pure POJO used for live computation, I don't need persistence stuff.

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• Problem detecting installed application on Win Svr 2003 x64

  - by PD

  I have an x86 Windows application that consists of a couple of services and a client ui. Due to various issues with persuading the various MSIs to upgrade properly, the installation process is now governed by a wizard-style program that detects what is currently installed and handles upgrades by storing the user's current settings, uninstalling the existing software and installing the new version(s). The basic process is: Look in HKLM\Software\Classes\Installer\Products Loop through the GUID keys therein looking for ProductName="(my app name)" If not found, repeat starting from HKCU\Software\Microsoft\Installer\Products instead If found, offer the user an upgrade (as described earlier) else a clean install (i.e. user is asked various questions by the wizard) Now, this works just fine on pretty much any Windows platform you care to mention, from XP up. It fails only on Windows Server 2003 x64, in that an existing installation is not detected by the wizard - despite the exact same registry keys being present as are on any other platform I test on. It's fine on: XP x32 Vista x32, x64 Server 2003 x86 Server 2008 x86, x64 Server 2008 R2 x64 Windows 7 x86, x64 It's only Server 2003 x64 that seems to exhibit this issue.

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• Protecting an Application's Memory From Tampering

  - by Changeling

  We are adding AES 256 bit encryption to our server and client applications for encrypting the TCP/IP traffic containing sensitive information. We will be rotating the keys daily. Because of that, the keys will be stored in memory with the applications. Key distribution process: Each server and client will have a list of initial Key Encryption Key's (KEK) by day If the client has just started up or the server has just started up, the client will request the daily key from the server using the initial key. The server will respond with the daily key, encrypted with the initial key. The daily key is a randomly generated set of alphanumeric characters. We are using AES 256 bit encryption. All subsequent communications will be encrypted using that daily key. Nightly, the client will request the new daily key from the server using the current daily key as the current KEK. After the client gets the new key, the new daily key will replace the old daily key. Is it possible for another bad application to gain access to this memory illegally or is this protected in Windows? The key will not be written to a file, only stored in a variable in memory. If an application can access the memory illegally, how can you protect the memory from tampering? We are using C++ and XP (Vista/7 may be an option in the future so I don't know if that changes the answer).

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• heterogeneous comparisons in python3

  - by Matt Anderson

  I'm 99+% still using python 2.x, but I'm trying to think ahead to the day when I switch. So, I know that using comparison operators (less/greater than, or equal to) on heterogeneous types that don't have a natural ordering is no longer supported in python3.x -- instead of some consistent (but arbitrary) result we raise TypeError instead. I see the logic in that, and even mostly think its a good thing. Consistency and refusing to guess is a virtue. But what if you essentially want the python2.x behavior? What's the best way to go about getting it? For fun (more or less) I was recently implementing a Skip List, a data structure that keeps its elements sorted. I wanted to use heterogeneous types as keys in the data structure, and I've got to compare keys to one another as I walk the data structure. The python2.x way of comparing makes this really convenient -- you get an understandable ordering amongst elements that have a natural ordering, and some ordering amongst those that don't. Consistently using a sort/comparison key like (type(obj).__name__, obj) has the disadvantage of not interleaving the objects that do have a natural ordering; you get all your floats clustered together before your ints, and your str-derived class separates from your strs. I came up with the following: import operator def hetero_sort_key(obj): cls = type(obj) return (cls.__name__+'_'+cls.__module__, obj) def make_hetero_comparitor(fn): def comparator(a, b): try: return fn(a, b) except TypeError: return fn(hetero_sort_key(a), hetero_sort_key(b)) return comparator hetero_lt = make_hetero_comparitor(operator.lt) hetero_gt = make_hetero_comparitor(operator.gt) hetero_le = make_hetero_comparitor(operator.le) hetero_ge = make_hetero_comparitor(operator.gt) Is there a better way? I suspect one could construct a corner case that this would screw up -- a situation where you can compare type A to B and type A to C, but where B and C raise TypeError when compared, and you can end up with something illogical like a > b, a < c, and yet b > c (because of how their class names sorted). I don't know how likely it is that you'd run into this in practice.

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• How to migrate primary key generation from "increment" to "hi-lo"?

  - by Bevan

  I'm working with a moderate sized SQL Server 2008 database (around 120 tables, backups are around 4GB compressed) where all the table primary keys are declared as simple int columns. At present, primary key values are generated by NHibernate with the increment identity generator, which has worked well thus far, but precludes moving to a multiprocessing environment. Load on the system is growing, so I'm evaluating the work required to allow the use of multiple servers accessing a common database backend. Transitioning to the hi-lo generator seems to be the best way forward, but I can't find a lot of detail about how such a migration would work. Will NHibernate automatically create rows in the hi-lo table for me, or do I need to script these manually? If NHibernate does insert rows automatically, does it properly take account of existing key values? If NHibernate does take care of thing automatically, that's great. If not, are there any tools to help? Update NHibernate's increment identifier generator works entirely in-memory. It's seeded by selecting the maximum value of used identifiers from the table, but from that point on allocates new values by a simple increment, without reference back to the underlying database table. If any other process adds rows to the table, you end up with primary key collisions. You can run multiple threads within the one process just fine, but you can't run multiple processes. For comparison, the NHibernate identity generator works by configuring the database tables with identity columns, putting control over primary key generation in the hands of the database. This works well, but compromises the unit of work pattern. The hi-lo algorithm sits inbetween these - generation of primary keys is coordinated through the database, allowing for multiprocessing, but actual allocation can occur entirely in memory, avoiding problems with the unit of work pattern.

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• jquery keypress iterate through each loop?

  - by user239831

  hey guys, probably a simpel question, however couldn't find anything online. i have a list with search results and i want to be able to navigate through the list with my up and down keys. if (e.keyCode == 40) { //down //alert('down'); $('#searchresults ul li').each(function() { }); } if (e.keyCode == 38) { //up //alert('up'); } if (e.keyCode == 13) { //enter //alert('enter'); } the searchresults look like this: <ul> <li class="matched"><a href="link1">link1</a></li> <li class="matched"><a href="link2">link2</a></li> <li class="matched"><a href="link3">link3</a></li> </ul> So basically i just want to be able to navigate through my searchresults with the up and down keys. the selection of the current element should maybe just change the background color and when i press enter the linked and matched element is fired. any idea how i can iterate through the searchresults? thank you

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• InstallExecuteSequence cache interferes with custom action operation

  - by Dima G

  I need to upgrade a product that could be installed in per-user context to a new version that is always in per-machine context. The requirements are: Whether the old version was installed in a Per-User (no matter who) or Per-Machine context should be completely seamless to an administrator user that performs the upgrade. The MSI upgrade should succeed without the need to know the password of the user that originally installed the previous version of the product in a Per-User context. The installation should be performed from a single .msi file (no setup.exe is allowed). The installation should be able to run in a silent (non-UI) mode. No reboots are allowed during installation. My strategy is to find in the beginning of the installation whether the product is already installed in per-user context, and if so, to transform the registry keys manually to Per-Machine context (I checked: no additional changes such as file system changes etc. are needed except this transform). I figured out how to move all appropriate keys in the registry from the user settings to the machine settings (pre-loaded appropriate user hive in case it didn't appear in HKEY_USERS) and created custom action that does it - and it does work when I run it as a stand-alone executable before running the MSI. The problem, however, is that when Windows Installer runs InstallExecuteSequence it first creates a 'cached product context' for all products. So when my custom action runs in the course of InstallExecuteSequence, this cache has already been created. Thus FindRelatedProducts action that determines if older product with same upgrade code exists looks on that cache and ignores the changes that my custom action applied. If before running the MSI the previous product was in per-user context, FindRelatedProducts will look at the cache and not apply the upgrade and remove the previous version, because the new product is in per-machine context, even though the previous product version is already configured to per-machine context in the registry by that time by my custom action. What can be done to solve this problem without violating the requirements stated above?

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• Doctrine Default Primary Key Problem (Again)

  - by 01010011

  Hi, Should I change all of my uniquely-named MySQL database primary keys to 'id' to avoid getting errors related to Doctrine's default primary key set in the plugin 'doctrine_pi.php'? To further elaborate, I am getting the following reoccurring error, this time after trying to login to my login page: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'u.book_id' in 'field list'' in... I suspect the problem resides at a MySQL table used for my login, of which has a primary key called id Marc B originally solved an identical problem for me in this post http://stackoverflow.com/questions/2702229/doctrine-codeigniter-mysql-crud-errors when I had the same problem with a different table within the same database. Following his suggestion, I changed the default primary key located at system/application/plugins/doctrine_pi.php from 'id' to 'book_id': <?php // system/application/plugins/doctrine_pi.php ... // set the default primary key to be named 'id', integer, 4 bytes Doctrine_Manager::getInstance()->setAttribute( Doctrine::ATTR_DEFAULT_IDENTIFIER_OPTIONS, array('name' => 'book_id', 'type' => 'integer', 'length' => 4)); and that solved my previous problem. However, my login page stopped working. So what is the safe thing to do? Change all of my primary keys to 'id' (will that solve the problem without causing some other problem I am not aware of). Or should I add some lines of code in doctrine_pi.php?

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• php -Merging an Array

  - by Vidhu Shresth Bhatnagar

  I have two array which i want to merge in a specific way in php. So i need your help in helping me with it as i tried and failed. So say i have two arrays: $array1= array( "foo" => 3, "bar" => 2, "random1" => 4, ); $array2= array( "random2" => 3, "random3" => 4, "foo" => 6, ); Now when during merging i would like the common key's values to be added. So like foo exists in array1 and in array2 so when merging array1 with array 2 i should get "foo" => "9" I better illustration would be the final array which looks like this: $array1= array( "foo" => 9, "bar" => 2, "random1" => 4, "random2" => 3, "random3" => 4, ); So again i would like the values of the common keys to be added together and non common keys to be added to array or a new array I hope i was clear enough Thanks, Vidhu

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• Decoding the IE9 user agent

  - by Portman

  I installed IE9 in a Windows 7 virtual machine, and was surprised to see this user agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0; BOIE9;ENUSMSNIP) In particular, the last two keys BOIE9 and ENUSMSNIP look very spammy. I'm used to seeing toolbars and add-ins register themselves at the end of the user agent like that, but this is on a virgin install of Windows 7 with no other software. They're defined in the registry here: HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\5.0\User Agent\PostPlatform That key has a value of IEAK, which is apparently the Internet Explorer Administrators Kit which according to Microsoft sends a custom user agent string. But why? I'm guessing that BOIE9 is stands for "Bing on IE9". It's the only active Add-On: As for ENUSMSNIP, I'm at a loss. My guesses are: ENUS = Locale, which for me is EN-US ("US English") MS = Microsoft NIP = ??? I tried changing my locale to EN-GB, but the user agent didn't update nor did the registry. So it appears it's only at the time of install that it matters (if I'm even right about ENUS). Does anyone know what these two user agent keys represent? Or, care to share what your IE9 user agent is, and maybe we can piece it together ourselves?

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• Using Python to get a CSV output for the following example.

  - by Az

  Hi there, I'm back again with my ongoing saga of Student-Project Allocation questions. Thanks to Moron (who does not match his namesake) I've got a bit of direction for an evaluation portion of my project. Going with the idea of the Assignment Problem and Hungarian Algorithm I would like to express my data in the form of a .csv file which would end up looking like this in spreadsheet form. This is based on the structure I saw here. | | Project 1 | Project 2 | Project 3 | |----------|-----------|-----------|-----------| |Student1 | | 2 | 1 | |----------|-----------|-----------|-----------| |Student2 | 1 | 2 | 3 | |----------|-----------|-----------|-----------| |Student3 | 1 | 3 | 2 | |----------|-----------|-----------|-----------| To make it less cryptic: the rows are the Students/Agents and the columns represent Projects/Task. Obviously ONE project can be assigned to ONE student. That, in short, is what my project is about. The fields represent the preference weights the students have placed upon the projects (ranging from 1 to 10). If blank, that student does not want that project and there's no chance of him/her being assigned such. Anyway, my data is stored within dictionaries. Specifically the students and projects dictionaries such that: students[student_id] = Student(student_id, student_name, alloc_proj, alloc_proj_rank, preferences) where preferences is in the form of a dictionary such that preferences[rank] = {project_id} and projects[project_id] = Project(project_id, project_name) I'm aware that sorted(students.keys()) will give me a sorted list of all the student IDs which will populate the row labels and sorted(projects.keys()) will give me the list I need to populate the column labels. Thus for each student, I'd go into their preferences dictionary and match the applicable projects to ranks. I can do that much. Where I'm failing is understanding how to create a .csv file. Any help, pointers or good tutorials will be highly appreciated.

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• retrieve value from hashtable with clone of key; C#

  - by Johnny

  I would like to know if there is any possible way to retrieve an item from a hashtable using a key that is identical to the actual key, but a different object. I understand why it is probably not possible, but I would like to see if there is any tricky way to do it. My problem arises from the fact that, being as stupid as I am, I created hashtables with int[] as the keys, with the integer arrays containing indices representing spatial position. I somehow knew that I needed to create a new int[] every time I wanted to add a new entry, but neglected to think that when I generated spatial coordinate arrays later they would be worthless in retrieving the values from my hashtables. Now I am trying to decide whether to rearrange things so that I can store my values in ArrayLists, or whether to search through the list of keys in the Hashtable for the one I need every time I want to get a value, neither of the options being very cool. Unless of course there is a way to get //1 to work like //2! Thanks in advance. static void Main(string[] args) { Hashtable dog = new Hashtable(); //1 int[] man = new int[] { 5 }; dog.Add(man, "hello"); int[] cat = new int[] { 5 }; Console.WriteLine(dog.ContainsKey(cat)); //false //2 int boy = 5; dog.Add(boy, "wtf"); int kitten = 5; Console.WriteLine(dog.ContainsKey(kitten)); //true; }

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• sqlite3 crashes for second insert statement

  - by Ayaz Alavi

  My App is crashing on statement (sqlite3_step(insertAlert) == SQLITE_DONE) when executed for i = 1. Can anybody tell me why it is crashing? sqlite3_stmt *insertAlert; textmeAppDelegate *textme = (textmeAppDelegate *)[[UIApplication sharedApplication] delegate]; NSString *insert = @"INSERT INTO alerts (alert_id, email_address, messege_text, when_to_send, how_often_send, recipient_phone_number) VALUES(?, ?, ?, ?, ?, ?)"; if(sqlite3_prepare_v2(textme.dbConn, [insert UTF8String], -1, &insertAlert, NULL) == SQLITE_OK) { NSDictionary *tmpDictionary; NSString *alertId; for(int i=0; i<[keys count]; i++) { alertId = [NSString stringWithFormat:@"%@", [keys objectAtIndex:i]]; tmpDictionary = [NSDictionary dictionaryWithDictionary:[dictionary2 objectForKey:alertId]]; sqlite3_bind_text(insertAlert, 1, [NSString stringWithFormat:@"%@", [tmpDictionary objectForKey:@"alert_id"]], -1, SQLITE_TRANSIENT); sqlite3_bind_text(insertAlert, 2, [NSString stringWithFormat:@"%@", [tmpDictionary objectForKey:@"email_address"]], -1, SQLITE_TRANSIENT); sqlite3_bind_text(insertAlert, 3, [NSString stringWithFormat:@"%@", [tmpDictionary objectForKey:@"messege_text"]], -1, SQLITE_TRANSIENT); sqlite3_bind_text(insertAlert, 4, [NSString stringWithFormat:@"%@", [tmpDictionary objectForKey:@"when_to_send"]], -1, SQLITE_TRANSIENT); sqlite3_bind_text(insertAlert, 5, [NSString stringWithFormat:@"%@", [tmpDictionary objectForKey:@"how_often_send"]], -1, SQLITE_TRANSIENT); sqlite3_bind_text(insertAlert, 6, [NSString stringWithFormat:@"%@", [tmpDictionary objectForKey:@"recipient_phone_number"]], -1, SQLITE_TRANSIENT); if (sqlite3_step(insertAlert) == SQLITE_DONE) { sqlite3_finalize(insertAlert); sqlite3_clear_bindings(insertAlert); } else { NSAssert1(0, @"Error while creating add statement. '%s'", sqlite3_errmsg(textme.dbConn)); //[textme showError:@"Device Error" errMsg:sqlite3_errmsg(textme.dbConn)]; return FALSE; } } sqlite3_finalize(insertAlert); }

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• Problems with objectatasource,giving attributes like delete insert and update

  - by kamal

  After going to the process of adding the various attributes like insert,delete and update.But when i run it through the browser ,editing works but updating and deleting doesn't !(for the update and shows the same thing for delete,my friends think i need to use codes to repair the problems,can you help me please.it shows this: Server Error in '/WebSite3' Application. ObjectDataSource 'ObjectDataSource1' could not find a non-generic method 'Update' that has parameters: First_name, Surname, Original_author_id, First name, original_author id. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.InvalidOperationException: ObjectDataSource 'ObjectDataSource1' could not find a non-generic method 'Update' that has parameters: First_name, Surname, Original_author_id, First name, original_author id. Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Stack Trace: [InvalidOperationException: ObjectDataSource 'ObjectDataSource1' could not find a non-generic method 'Update' that has parameters: First_name, Surname, Original_author_id, First name, original_author id.] System.Web.UI.WebControls.ObjectDataSourceView.GetResolvedMethodData(Type type, String methodName, IDictionary allParameters, DataSourceOperation operation) +1119426 System.Web.UI.WebControls.ObjectDataSourceView.ExecuteUpdate(IDictionary keys, IDictionary values, IDictionary oldValues) +1008 System.Web.UI.DataSourceView.Update(IDictionary keys, IDictionary values, IDictionary oldValues, DataSourceViewOperationCallback callback) +92 System.Web.UI.WebControls.GridView.HandleUpdate(GridViewRow row, Int32 rowIndex, Boolean causesValidation) +907 System.Web.UI.WebControls.GridView.HandleEvent(EventArgs e, Boolean causesValidation, String validationGroup) +704 System.Web.UI.WebControls.GridView.OnBubbleEvent(Object source, EventArgs e) +95 System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +37 System.Web.UI.WebControls.GridViewRow.OnBubbleEvent(Object source, EventArgs e) +123 System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +37 System.Web.UI.WebControls.LinkButton.OnCommand(CommandEventArgs e) +118

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• how to model a follower stream in appengine?

  - by molicule

  I am trying to design tables to buildout a follower relationship. Say I have a stream of 140char records that have user, hashtag and other text. Users follow other users, and can also follow hashtags. I am outlining the way I've designed this below, but there are two limitaions in my design. I was wondering if others had smarter ways to accomplish the same goal. The issues with this are The list of followers is copied in for each record If a new follower is added or one removed, 'all' the records have to be updated. The code class HashtagFollowers(db.Model): """ This table contains the followers for each hashtag """ hashtag = db.StringProperty() followers = db.StringListProperty() class UserFollowers(db.Model): """ This table contains the followers for each user """ username = db.StringProperty() followers = db.StringListProperty() class stream(db.Model): """ This table contains the data stream """ username = db.StringProperty() hashtag = db.StringProperty() text = db.TextProperty() def save(self): """ On each save all the followers for each hashtag and user are added into a another table with this record as the parent """ super(stream, self).save() hfs = HashtagFollowers.all().filter("hashtag =", self.hashtag).fetch(10) for hf in hfs: sh = streamHashtags(parent=self, followers=hf.followers) sh.save() ufs = UserFollowers.all().filter("username =", self.username).fetch(10) for uf in ufs: uh = streamUsers(parent=self, followers=uf.followers) uh.save() class streamHashtags(db.Model): """ The stream record is the parent of this record """ followers = db.StringListProperty() class streamUsers(db.Model): """ The stream record is the parent of this record """ followers = db.StringListProperty() Now, to get the stream of followed hastags indexes = db.GqlQuery("""SELECT __key__ from streamHashtags where followers = 'myusername'""") keys = [k,parent() for k in indexes[offset:numresults]] return db.get(keys) Is there a smarter way to do this?

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• Hashtable with int array as key in java

  - by Niels Hansen

  Hey! I'm trying to make a hashtable in java where the keys are int[], but it dosen't work. I have made a little test program to show my problem: public class test{ public static void main(String[] args){ int[] test0 = {1,1}; int[] test1 = {1,1}; Hashtable<int[], String> ht = new Hashtable<int[], String>(); String s0 = "foo"; ht.put(test0, s0); System.out.println("the result from ht.get(test1)"); System.out.println(ht.get(test1)); System.out.println("the result from ht.get(test0)"); System.out.println(ht.get(test0)); } } My intention is that both ht.get calles should return the same result, since the two arrays are equal, but they dont. Here is the result from running the code: the result from ht.get(test1) null the result from ht.get(test0) foo Am I missing something here or is it just impossible to use int[] as keys in a hastable?

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• Time complexity to fill hash table (homework)?

  - by Heathcliff

  This is a homework question, but I think there's something missing from it. It asks: Provide a sequence of m keys to fill a hash table implemented with linear probing, such that the time to fill it is minimum. And then Provide another sequence of m keys, but such that the time fill it is maximum. Repeat these two questions if the hash table implements quadratic probing I can only assume that the hash table has size m, both because it's the only number given and because we have been using that letter to address a hash table size before when describing the load factor. But I can't think of any sequence to do the first without knowing the hash function that hashes the sequence into the table. If it is a bad hash function, such that, for instance, it hashes every entry to the same index, then both the minimum and maximum time to fill it will take O(n) time, regardless of what the sequence looks like. And in the average case, where I assume the hash function is OK, how am I suppossed to know how long it will take for that hash function to fill the table? Aren't these questions linked to the hash function stronger than they are to the sequence that is hashed? As for the second question, I can assume that, regardless of the hash function, a sequence of size m with the same key repeated m-times will provide the maximum time, because it will cause linear probing from the second entry on. I think that will take O(n) time. Is that correct? Thanks

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• Simple encryption - Sum of Hashes in C

  - by Dogbert

  I am attempting to demonstrate a simple proof of concept with respect to a vulnerability in a piece of code in a game written in C. Let's say that we want to validate a character login. The login is handled by the user choosing n items, (let's just assume n=5 for now) from a graphical menu. The items are all medieval themed: eg: _______________________________ | | | | | Bow | Sword | Staff | |-----------|-----------|-------| | Shield | Potion | Gold | |___________|___________|_______| The user must click on each item, then choose a number for each item. The validation algorithm then does the following: Determines which items were selected Drops each string to lowercase (ie: Bow becomes bow, etc) Calculates a simple string hash for each string (ie: `bow = b=2, o=15, w=23, sum = (2+15+23=40) Multiplies the hash by the value the user selected for the corresponding item; This new value is called the key Sums together the keys for each of the selected items; this is the final validation hash IMPORTANT: The validator will accept this hash, along with non-zero multiples of it (ie: if the final hash equals 1111, then 2222, 3333, 8888, etc are also valid). So, for example, let's say I select: Bow (1) Sword (2) Staff (10) Shield (1) Potion (6) The algorithm drops each of these strings to lowercase, calculates their string hashes, multiplies that hash by the number selected for each string, then sums these keys together. eg: Final_Validation_Hash = 1*HASH(Bow) + 2*HASH(Sword) + 10*HASH(Staff) + 1*HASH(Shield) + 6*HASH(Potion) By application of Euler's Method, I plan to demonstrate that these hashes are not unique, and want to devise a simple application to prove it. in my case, for 5 items, I would essentially be trying to calculate: (B)(y) = (A_1)(x_1) + (A_2)(x_2) + (A_3)(x_3) + (A_4)(x_4) + (A_5)(x_5) Where: B is arbitrary A_j are the selected coefficients/values for each string/category x_j are the hash values for each string/category y is the final validation hash (eg: 1111 above) B,y,A_j,x_j are all discrete-valued, positive, and non-zero (ie: natural numbers) Can someone either assist me in solving this problem or point me to a similar example (ie: code, worked out equations, etc)? I just need to solve the final step (ie: (B)(Y) = ...). Thank you all in advance.

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• How to index a table with a Type 2 slowly changing dimension for optimal performance

  - by The Lazy DBA

  Suppose you have a table with a Type 2 slowly-changing dimension. Let's express this table as follows, with the following columns: * [Key] * [Value1] * ... * [ValueN] * [StartDate] * [ExpiryDate] In this example, let's suppose that [StartDate] is effectively the date in which the values for a given [Key] become known to the system. So our primary key would be composed of both [StartDate] and [Key]. When a new set of values arrives for a given [Key], we assign [ExpiryDate] to some pre-defined high surrogate value such as '12/31/9999'. We then set the existing "most recent" records for that [Key] to have an [ExpiryDate] that is equal to the [StartDate] of the new value. A simple update based on a join. So if we always wanted to get the most recent records for a given [Key], we know we could create a clustered index that is: * [ExpiryDate] ASC * [Key] ASC Although the keyspace may be very wide (say, a million keys), we can minimize the number of pages between reads by initially ordering them by [ExpiryDate]. And since we know the most recent record for a given key will always have an [ExpiryDate] of '12/31/9999', we can use that to our advantage. However... what if we want to get a point-in-time snapshot of all [Key]s at a given time? Theoretically, the entirety of the keyspace isn't all being updated at the same time. Therefore for a given point-in-time, the window between [StartDate] and [ExpiryDate] is variable, so ordering by either [StartDate] or [ExpiryDate] would never yield a result in which all the records you're looking for are contiguous. Granted, you can immediately throw out all records in which the [StartDate] is greater than your defined point-in-time. In essence, in a typical RDBMS, what indexing strategy affords the best way to minimize the number of reads to retrieve the values for all keys for a given point-in-time? I realize I can at least maximize IO by partitioning the table by [Key], however this certainly isn't ideal. Alternatively, is there a different type of slowly-changing-dimension that solves this problem in a more performant manner?

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• Object equality in context of hibernate / webapp

  - by bert

  How do you handle object equality for java objects managed by hibernate? In the 'hibernate in action' book they say that one should favor business keys over surrogate keys. Most of the time, i do not have a business key. Think of addresses mapped to a person. The addresses are keeped in a Set and displayed in a Wicket RefreshingView (with a ReuseIfEquals strategy). I could either use the surrogate id or use all fields in the equals() and hashCode() functions. The problem is that those fields change during the lifetime ob the object. Either because the user entered some data or the id changes due to JPA merge() being called inside the OSIV (Open Session in View) filter. My understanding of the equals() and hashCode() contract is that those should not change during the lifetime of an object. What i have tried so far: equals() based on hashCode() which uses the database id (or super.hashCode() if id is null). Problem: new addresses start with an null id but get an id when attached to a person and this person gets merged() (re-attached) in the osiv-filter. lazy compute the hashcode when hashCode() is first called and make that hashcode @Transitional. Does not work, as merge() returns a new object and the hashcode does not get copied over. What i would need is an ID that gets assigned during object creation I think. What would be my options here? I don't want to introduce some additional persistent property. Is there a way to explicitly tell JPA to assign an ID to an object? Regards

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• Using lambda expressions and linq

  - by Andy

  So I've just started working with linq as well as using lambda expressions. I've run into a small hiccup while trying to get some data that I want. This method should return a list of all projects that are open or in progress from Jira Here's the code public static List<string> getOpenIssuesListByProject(string _projectName) { JiraSoapServiceService jiraSoapService = new JiraSoapServiceService(); string token = jiraSoapService.login(DEFAULT_UN, DEFAULT_PW); string[] keys = { getProjectKey(_projectName) }; RemoteStatus[] statuses = jiraSoapService.getStatuses(token); var desiredStatuses = statuses.Where(x => x.name == "Open" || x.name == "In Progress") .Select(x=>x.id); RemoteIssue[] AllIssues = jiraSoapService.getIssuesFromTextSearchWithProject(token, keys, "", 99); IEnumerable<RemoteIssue> openIssues = AllIssues.Where(x=> { foreach (var v in desiredStatuses) { if (x.status == v) return true; else return false; } return false; }); return openIssues.Select(x => x.key).ToList(); } Right now this only select issues that are "Open", and seems to skip those that are "In Progress". My question: First, why am I only getting the "Open" Issues, and second is there a better way to do this? The reason I get all the statuses first is that the issue only stores that statuses ID, so I get all the statuses, get the ID's that match "Open" and "In Progress", and then match those ID numbers to the issues status field.

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• PHP elseif statement not executed even though initial if statement is false

  - by DarwinIcesurfer

  I am writing a recursive function to print out the differences between 2 multildimensional php arrays. The purpose of this code is to see the difference between jpeg headers to deteremine how adobe bridge cs3 is saving rating information within the jpg file. When I am single-stepping through the code using my eclipse - zend debugger ide, it appears that even though the initial if statement is false (ie both values are arrays), the subsequent elseif statements are never executed. The function is attached below. function array_diff_multi($array1,$array2,$level){ $keys = array_keys($array1); foreach($keys as $key) { $value1 = $array1[$key]; if(array_key_exists($key,$array2) ){ $value2 = $array2[$key]; // Check if they are both arrays, if so recursion is needed if (is_array($value1) && is_array($value2)){ array_diff_multi($value1,$value2,$level . "[ " . $key . " ]"); } // the values aren't both arrays *** THE CODE IN THE ELSEIF BELOW IS NOT EXECUTED *** elseif(is_array($value1) != is_array($value2)){ print "" . $level . $key ."=" . $value1 . "as array, compared to ". $value2 .""; } // the values don't match elseif($value1 != $value2){ print "" . $level . $key ."=" . $value1 ." != " . $value2 .""; } else; } else{ print "" . $level. $key . "does not exist in array2"; } } }

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