static block - Page 143

Extension Methods in Dot Net 2.0

- by Tom Hines

Not that anyone would still need this, but in case you have a situation where the code MUST be .NET 2.0 compliant and you want to use a cool feature like Extension methods, there is a way. I saw this article when looking for ways to create extension methods in C++, C# and VB: http://msdn.microsoft.com/en-us/magazine/cc163317.aspx The author shows a simple way to declare/define the ExtensionAttribute so it's available to 2.0 .NET code. Please read the article to learn about the when and why and use the content below to learn HOW. In the next post, I'll demonstrate cross-language calling of extension methods. Here is a version of it in C# First, here's the project showing there's no VOODOO included: using System; namespace System.Runtime.CompilerServices { [ AttributeUsage( AttributeTargets.Assembly | AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = false) ] class ExtensionAttribute : Attribute{} } namespace TestTwoDotExtensions { public static class Program { public static void DoThingCS(this string str) { Console.WriteLine("2.0\t{0:G}\t2.0", str); } static void Main(string[] args) { "asdf".DoThingCS(); } } } Here is the C++ version: // TestTwoDotExtensions_CPP.h #pragma once using namespace System; namespace System { namespace Runtime { namespace CompilerServices { [ AttributeUsage( AttributeTargets::Assembly | AttributeTargets::Class | AttributeTargets::Method, AllowMultiple = false, Inherited = false) ] public ref class ExtensionAttribute : Attribute{}; } } } using namespace System::Runtime::CompilerServices; namespace TestTwoDotExtensions_CPP { public ref class CTestTwoDotExtensions_CPP { public: [ExtensionAttribute] // or [Extension] static void DoThingCPP(String^ str) { Console::WriteLine("2.0\t{0:G}\t2.0", str); } }; }

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Apache 2.2 Present rss http 410 pages as application/rss+xml content type

- by Mark Bakker

I have a problem sending http-410 for very old rss feeds. Functional this can happen in one Very old rss feeds where content is not updated anymore / subject could not move to another feed Migration from 3th party site to our site where the rss feed is not longer functional supported I tried several things in my site config see below; <VirtualHost *:80> DocumentRoot /opt/tomcat/webapps/ROOT/ ErrorDocument 500 /error/static/error-500.html ErrorDocument 503 /error/static/error-500.html ErrorDocument 404 /error/static/rss/error-404.html ErrorDocument 410 /error/static/rss/error-410.html # When error pages need to be served by apache, # exclude the files to serve as below (in comment) SetEnvIf Request_URI "/error/static/*" no-jk # force all files to be image/gif: <Location *.rss> #<Location *> #ForceType application/rss+xml </Location> #AddType application/rss+xml .rss #AddType application/rss+xml .xml #AddType application/rss+xml .html JkMount /* rss;use_server_errors=402 # JkMount /* rss RewriteEngine on JkMount /news.rss rss JkMount /documenten-en-publicaties.rss rss RewriteEngine on RewriteRule ^/news.rss$ - [NC,T=application/rss+xml,G,L] RewriteRule ^/documenten-en-publicaties.rss$ - [NC,G,L] # Possible values include: debug, info, notice, warn, error, crit, # alert, emerg. LogLevel warn ErrorLog "|/usr/bin/logger -s -p local3.err -t 'Apache'" CustomLog "|/usr/bin/logger -s -p local2.info -t 'Apache'" combined ServerSignature Off </VirtualHost> The desired end result should be on /news.rss and /documenten-en-publicaties.rss a 410 page with content in the error page with a content type 'application/rss+xml'

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Understanding C# async / await (2) Awaitable / Awaiter Pattern

- by Dixin

What is awaitable Part 1 shows that any Task is awaitable. Actually there are other awaitable types. Here is an example: Task<int> task = new Task<int>(() => 0); int result = await task.ConfigureAwait(false); // Returns a ConfiguredTaskAwaitable<TResult>. The returned ConfiguredTaskAwaitable<TResult> struct is awaitable. And it is not Task at all: public struct ConfiguredTaskAwaitable<TResult> { private readonly ConfiguredTaskAwaiter m_configuredTaskAwaiter; internal ConfiguredTaskAwaitable(Task<TResult> task, bool continueOnCapturedContext) { this.m_configuredTaskAwaiter = new ConfiguredTaskAwaiter(task, continueOnCapturedContext); } public ConfiguredTaskAwaiter GetAwaiter() { return this.m_configuredTaskAwaiter; } } It has one GetAwaiter() method. Actually in part 1 we have seen that Task has GetAwaiter() method too: public class Task { public TaskAwaiter GetAwaiter() { return new TaskAwaiter(this); } } public class Task<TResult> : Task { public new TaskAwaiter<TResult> GetAwaiter() { return new TaskAwaiter<TResult>(this); } } Task.Yield() is a another example: await Task.Yield(); // Returns a YieldAwaitable. The returned YieldAwaitable is not Task either: public struct YieldAwaitable { public YieldAwaiter GetAwaiter() { return default(YieldAwaiter); } } Again, it just has one GetAwaiter() method. In this article, we will look at what is awaitable. The awaitable / awaiter pattern By observing different awaitable / awaiter types, we can tell that an object is awaitable if It has a GetAwaiter() method (instance method or extension method); Its GetAwaiter() method returns an awaiter. An object is an awaiter if: It implements INotifyCompletion or ICriticalNotifyCompletion interface; It has an IsCompleted, which has a getter and returns a Boolean; it has a GetResult() method, which returns void, or a result. This awaitable / awaiter pattern is very similar to the iteratable / iterator pattern. Here is the interface definitions of iteratable / iterator: public interface IEnumerable { IEnumerator GetEnumerator(); } public interface IEnumerator { object Current { get; } bool MoveNext(); void Reset(); } public interface IEnumerable<out T> : IEnumerable { IEnumerator<T> GetEnumerator(); } public interface IEnumerator<out T> : IDisposable, IEnumerator { T Current { get; } } In case you are not familiar with the out keyword, please find out the explanation in Understanding C# Covariance And Contravariance (2) Interfaces. The “missing” IAwaitable / IAwaiter interfaces Similar to IEnumerable and IEnumerator interfaces, awaitable / awaiter can be visualized by IAwaitable / IAwaiter interfaces too. This is the non-generic version: public interface IAwaitable { IAwaiter GetAwaiter(); } public interface IAwaiter : INotifyCompletion // or ICriticalNotifyCompletion { // INotifyCompletion has one method: void OnCompleted(Action continuation); // ICriticalNotifyCompletion implements INotifyCompletion, // also has this method: void UnsafeOnCompleted(Action continuation); bool IsCompleted { get; } void GetResult(); } Please notice GetResult() returns void here. Task.GetAwaiter() / TaskAwaiter.GetResult() is of such case. And this is the generic version: public interface IAwaitable<out TResult> { IAwaiter<TResult> GetAwaiter(); } public interface IAwaiter<out TResult> : INotifyCompletion // or ICriticalNotifyCompletion { bool IsCompleted { get; } TResult GetResult(); } Here the only difference is, GetResult() return a result. Task<TResult>.GetAwaiter() / TaskAwaiter<TResult>.GetResult() is of this case. Please notice .NET does not define these IAwaitable / IAwaiter interfaces at all. As an UI designer, I guess the reason is, IAwaitable interface will constraint GetAwaiter() to be instance method. Actually C# supports both GetAwaiter() instance method and GetAwaiter() extension method. Here I use these interfaces only for better visualizing what is awaitable / awaiter. Now, if looking at above ConfiguredTaskAwaitable / ConfiguredTaskAwaiter, YieldAwaitable / YieldAwaiter, Task / TaskAwaiter pairs again, they all “implicitly” implement these “missing” IAwaitable / IAwaiter interfaces. In the next part, we will see how to implement awaitable / awaiter. Await any function / action In C# await cannot be used with lambda. This code: int result = await (() => 0); will cause a compiler error: Cannot await 'lambda expression' This is easy to understand because this lambda expression (() => 0) may be a function or a expression tree. Obviously we mean function here, and we can tell compiler in this way: int result = await new Func<int>(() => 0); It causes an different error: Cannot await 'System.Func<int>' OK, now the compiler is complaining the type instead of syntax. With the understanding of the awaitable / awaiter pattern, Func<TResult> type can be easily made into awaitable. GetAwaiter() instance method, using IAwaitable / IAwaiter interfaces First, similar to above ConfiguredTaskAwaitable<TResult>, a FuncAwaitable<TResult> can be implemented to wrap Func<TResult>: internal struct FuncAwaitable<TResult> : IAwaitable<TResult> { private readonly Func<TResult> function; public FuncAwaitable(Func<TResult> function) { this.function = function; } public IAwaiter<TResult> GetAwaiter() { return new FuncAwaiter<TResult>(this.function); } } FuncAwaitable<TResult> wrapper is used to implement IAwaitable<TResult>, so it has one instance method, GetAwaiter(), which returns a IAwaiter<TResult>, which wraps that Func<TResult> too. FuncAwaiter<TResult> is used to implement IAwaiter<TResult>: public struct FuncAwaiter<TResult> : IAwaiter<TResult> { private readonly Task<TResult> task; public FuncAwaiter(Func<TResult> function) { this.task = new Task<TResult>(function); this.task.Start(); } bool IAwaiter<TResult>.IsCompleted { get { return this.task.IsCompleted; } } TResult IAwaiter<TResult>.GetResult() { return this.task.Result; } void INotifyCompletion.OnCompleted(Action continuation) { new Task(continuation).Start(); } } Now a function can be awaited in this way: int result = await new FuncAwaitable<int>(() => 0); GetAwaiter() extension method As IAwaitable shows, all that an awaitable needs is just a GetAwaiter() method. In above code, FuncAwaitable<TResult> is created as a wrapper of Func<TResult> and implements IAwaitable<TResult>, so that there is a GetAwaiter() instance method. If a GetAwaiter() extension method can be defined for Func<TResult>, then FuncAwaitable<TResult> is no longer needed: public static class FuncExtensions { public static IAwaiter<TResult> GetAwaiter<TResult>(this Func<TResult> function) { return new FuncAwaiter<TResult>(function); } } So a Func<TResult> function can be directly awaited: int result = await new Func<int>(() => 0); Using the existing awaitable / awaiter - Task / TaskAwaiter Remember the most frequently used awaitable / awaiter - Task / TaskAwaiter. With Task / TaskAwaiter, FuncAwaitable / FuncAwaiter are no longer needed: public static class FuncExtensions { public static TaskAwaiter<TResult> GetAwaiter<TResult>(this Func<TResult> function) { Task<TResult> task = new Task<TResult>(function); task.Start(); return task.GetAwaiter(); // Returns a TaskAwaiter<TResult>. } } Similarly, with this extension method: public static class ActionExtensions { public static TaskAwaiter GetAwaiter(this Action action) { Task task = new Task(action); task.Start(); return task.GetAwaiter(); // Returns a TaskAwaiter. } } an action can be awaited as well: await new Action(() => { }); Now any function / action can be awaited: await new Action(() => HelperMethods.IO()); // or: await new Action(HelperMethods.IO); If function / action has parameter(s), closure can be used: int arg0 = 0; int arg1 = 1; int result = await new Action(() => HelperMethods.IO(arg0, arg1)); Using Task.Run() The above code is used to demonstrate how awaitable / awaiter can be implemented. Because it is a common scenario to await a function / action, so .NET provides a built-in API: Task.Run(): public class Task2 { public static Task Run(Action action) { // The implementation is similar to: Task task = new Task(action); task.Start(); return task; } public static Task<TResult> Run<TResult>(Func<TResult> function) { // The implementation is similar to: Task<TResult> task = new Task<TResult>(function); task.Start(); return task; } } In reality, this is how we await a function: int result = await Task.Run(() => HelperMethods.IO(arg0, arg1)); and await a action: await Task.Run(() => HelperMethods.IO());

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C#/.NET – Finding an Item’s Index in IEnumerable<T>

- by James Michael Hare

Sorry for the long blogging hiatus. First it was, of course, the holidays hustle and bustle, then my brother and his wife gave birth to their son, so I’ve been away from my blogging for two weeks. Background: Finding an item’s index in List<T> is easy… Many times in our day to day programming activities, we want to find the index of an item in a collection. Now, if we have a List<T> and we’re looking for the item itself this is trivial: 1: // assume have a list of ints: 2: var list = new List<int> { 1, 13, 42, 64, 121, 77, 5, 99, 132 }; 3: 4: // can find the exact item using IndexOf() 5: var pos = list.IndexOf(64); This will return the position of the item if it’s found, or –1 if not. It’s easy to see how this works for primitive types where equality is well defined. For complex types, however, it will attempt to compare them using EqualityComparer<T>.Default which, in a nutshell, relies on the object’s Equals() method. So what if we want to search for a condition instead of equality? That’s also easy in a List<T> with the FindIndex() method: 1: // assume have a list of ints: 2: var list = new List<int> { 1, 13, 42, 64, 121, 77, 5, 99, 132 }; 3: 4: // finds index of first even number or -1 if not found. 5: var pos = list.FindIndex(i => i % 2 == 0); Problem: Finding an item’s index in IEnumerable<T> is not so easy... This is all well and good for lists, but what if we want to do the same thing for IEnumerable<T>? A collection of IEnumerable<T> has no indexing, so there’s no direct method to find an item’s index. LINQ, as powerful as it is, gives us many tools to get us this information, but not in one step. As with almost any problem involving collections, there are several ways to accomplish the same goal. And once again as with almost any problem involving collections, the choice of the solution somewhat depends on the situation. So let’s look at a few possible alternatives. I’m going to express each of these as extension methods for simplicity and consistency. Solution: The TakeWhile() and Count() combo One of the things you can do is to perform a TakeWhile() on the list as long as your find condition is not true, and then do a Count() of the items it took. The only downside to this method is that if the item is not in the list, the index will be the full Count() of items, and not –1. So if you don’t know the size of the list beforehand, this can be confusing. 1: // a collection of extra extension methods off IEnumerable<T> 2: public static class EnumerableExtensions 3: { 4: // Finds an item in the collection, similar to List<T>.FindIndex() 5: public static int FindIndex<T>(this IEnumerable<T> list, Predicate<T> finder) 6: { 7: // note if item not found, result is length and not -1! 8: return list.TakeWhile(i => !finder(i)).Count(); 9: } 10: } Personally, I don’t like switching the paradigm of not found away from –1, so this is one of my least favorites. Solution: Select with index Many people don’t realize that there is an alternative form of the LINQ Select() method that will provide you an index of the item being selected: 1: list.Select( (item,index) => do something here with the item and/or index... ) This can come in handy, but must be treated with care. This is because the index provided is only as pertains to the result of previous operations (if any). For example: 1: // assume have a list of ints: 2: var list = new List<int> { 1, 13, 42, 64, 121, 77, 5, 99, 132 }; 3: 4: // you'd hope this would give you the indexes of the even numbers 5: // which would be 2, 3, 8, but in reality it gives you 0, 1, 2 6: list.Where(item => item % 2 == 0).Select((item,index) => index); The reason the example gives you the collection { 0, 1, 2 } is because the where clause passes over any items that are odd, and therefore only the even items are given to the select and only they are given indexes. Conversely, we can’t select the index and then test the item in a Where() clause, because then the Where() clause would be operating on the index and not the item! So, what we have to do is to select the item and index and put them together in an anonymous type. It looks ugly, but it works: 1: // extensions defined on IEnumerable<T> 2: public static class EnumerableExtensions 3: { 4: // finds an item in a collection, similar to List<T>.FindIndex() 5: public static int FindIndex<T>(this IEnumerable<T> list, Predicate<T> finder) 6: { 7: // if you don't name the anonymous properties they are the variable names 8: return list.Select((item, index) => new { item, index }) 9: .Where(p => finder(p.item)) 10: .Select(p => p.index + 1) 11: .FirstOrDefault() - 1; 12: } 13: } So let’s look at this, because i know it’s convoluted: First Select() joins the items and their indexes into an anonymous type. Where() filters that list to only the ones matching the predicate. Second Select() picks the index of the matches and adds 1 – this is to distinguish between not found and first item. FirstOrDefault() returns the first item found from the previous clauses or default (zero) if not found. Subtract one so that not found (zero) will be –1, and first item (one) will be zero. The bad thing is, this is ugly as hell and creates anonymous objects for each item tested until it finds the match. This concerns me a bit but we’ll defer judgment until compare the relative performances below. Solution: Convert ToList() and use FindIndex() This solution is easy enough. We know any IEnumerable<T> can be converted to List<T> using the LINQ extension method ToList(), so we can easily convert the collection to a list and then just use the FindIndex() method baked into List<T>. 1: // a collection of extension methods for IEnumerable<T> 2: public static class EnumerableExtensions 3: { 4: // find the index of an item in the collection similar to List<T>.FindIndex() 5: public static int FindIndex<T>(this IEnumerable<T> list, Predicate<T> finder) 6: { 7: return list.ToList().FindIndex(finder); 8: } 9: } This solution is simplicity itself! It is very concise and elegant and you need not worry about anyone misinterpreting what it’s trying to do (as opposed to the more convoluted LINQ methods above). But the main thing I’m concerned about here is the performance hit to allocate the List<T> in the ToList() call, but once again we’ll explore that in a second. Solution: Roll your own FindIndex() for IEnumerable<T> Of course, you can always roll your own FindIndex() method for IEnumerable<T>. It would be a very simple for loop which scans for the item and counts as it goes. There’s many ways to do this, but one such way might look like: 1: // extension methods for IEnumerable<T> 2: public static class EnumerableExtensions 3: { 4: // Finds an item matching a predicate in the enumeration, much like List<T>.FindIndex() 5: public static int FindIndex<T>(this IEnumerable<T> list, Predicate<T> finder) 6: { 7: int index = 0; 8: foreach (var item in list) 9: { 10: if (finder(item)) 11: { 12: return index; 13: } 14: 15: index++; 16: } 17: 18: return -1; 19: } 20: } Well, it’s not quite simplicity, and those less familiar with LINQ may prefer it since it doesn’t include all of the lambdas and behind the scenes iterators that come with deferred execution. But does having this long, blown out method really gain us much in performance? Comparison of Proposed Solutions So we’ve now seen four solutions, let’s analyze their collective performance. I took each of the four methods described above and run them over 100,000 iterations of lists of size 10, 100, 1000, and 10000 and here’s the performance results. Then I looked for targets at the begining of the list (best case), middle of the list (the average case) and not in the list (worst case as must scan all of the list). Each of the times below is the average time in milliseconds for one execution as computer over the 100,000 iterations: Searches Matching First Item (Best Case) 10 100 1000 10000 TakeWhile 0.0003 0.0003 0.0003 0.0003 Select 0.0005 0.0005 0.0005 0.0005 ToList 0.0002 0.0003 0.0013 0.0121 Manual 0.0001 0.0001 0.0001 0.0001 Searches Matching Middle Item (Average Case) 10 100 1000 10000 TakeWhile 0.0004 0.0020 0.0191 0.1889 Select 0.0008 0.0042 0.0387 0.3802 ToList 0.0002 0.0007 0.0057 0.0562 Manual 0.0002 0.0013 0.0129 0.1255 Searches Where Not Found (Worst Case) 10 100 1000 10000 TakeWhile 0.0006 0.0039 0.0381 0.3770 Select 0.0012 0.0081 0.0758 0.7583 ToList 0.0002 0.0012 0.0100 0.0996 Manual 0.0003 0.0026 0.0253 0.2514 Notice something interesting here, you’d think the “roll your own” loop would be the most efficient, but it only wins when the item is first (or very close to it) regardless of list size. In almost all other cases though and in particular the average case and worst case, the ToList()/FindIndex() combo wins for performance, even though it is creating some temporary memory to hold the List<T>. If you examine the algorithm, the reason why is most likely because once it’s in a ToList() form, internally FindIndex() scans the internal array which is much more efficient to iterate over. Thus, it takes a one time performance hit (not including any GC impact) to create the List<T> but after that the performance is much better. Summary If you’re concerned about too many throw-away objects, you can always roll your own FindIndex() method, but for sheer simplicity and overall performance, using the ToList()/FindIndex() combo performs best on nearly all list sizes in the average and worst cases. Technorati Tags: C#,.NET,Litte Wonders,BlackRabbitCoder,Software,LINQ,List

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Trying to Host Server for External Access - Apache, VirtualBox & Portforwarding

- by Tspoon

Banging my head on the wall at this stage.... trying to host my Apache site on Ubuntu 12.10 with VirtualBox. Running Windows 8 host. Things I've done: Ensured Apache is listening on ports 80, 443 and 8080 (for thoroughness) tcp 0 0 0.0.0.0:443 0.0.0.0:* LISTEN 3355/httpd tcp 0 0 0.0.0.0:8080 0.0.0.0:* LISTEN 3355/httpd tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 3355/httpd tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 681/sshd VM is using bridged network connection Assigned a static IP to my Ubuntu VM, which can be accessed fine from within network. Forwarded TCP ports 80, 8080, 443 on the static IP of VM on my router Given my VM a static NAT Address Turned off Ubuntu firewall and router firewall Read on forums that my ISP (Eircom) allow port 80 to be used And I still can't access my site using the WAN/External IP (checked internally and using CanYouSeeMe.org). It says all the ports I mentioned are closed. I'm really at a loss of what to try next... Am I missing something silly here? Note: I haven't assigned a static IP address within the router, on within the VM. And DHCP server is enabled. Is that bad?

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Which Apache modules are safe to disable?

- by Gaia

Each Apache process is using about 70MB of private/rss memory, so I would like to lean them up a bit. The server runs Magento and Wordpress only. PHP is run as fcgid. Which modules would you consider safe to disable? Loaded Modules: core_module (static) mpm_prefork_module (static) http_module (static) so_module (static) auth_basic_module (shared) auth_digest_module (shared) authn_file_module (shared) authn_alias_module (shared) authn_anon_module (shared) authn_dbm_module (shared) authn_default_module (shared) authz_host_module (shared) authz_user_module (shared) authz_owner_module (shared) authz_groupfile_module (shared) authz_dbm_module (shared) authz_default_module (shared) ldap_module (shared) authnz_ldap_module (shared) include_module (shared) log_config_module (shared) logio_module (shared) env_module (shared) ext_filter_module (shared) mime_magic_module (shared) expires_module (shared) deflate_module (shared) headers_module (shared) usertrack_module (shared) setenvif_module (shared) mime_module (shared) dav_module (shared) status_module (shared) autoindex_module (shared) info_module (shared) dav_fs_module (shared) vhost_alias_module (shared) negotiation_module (shared) dir_module (shared) actions_module (shared) speling_module (shared) userdir_module (shared) alias_module (shared) substitute_module (shared) rewrite_module (shared) proxy_module (shared) proxy_balancer_module (shared) proxy_ftp_module (shared) proxy_http_module (shared) proxy_ajp_module (shared) proxy_connect_module (shared) cache_module (shared) suexec_module (shared) disk_cache_module (shared) cgi_module (shared) version_module (shared) sed_module (shared) security2_module (shared) unique_id_module (shared) fcgid_module (shared) evasive20_module (shared) perl_module (shared) php5_module (shared) ssl_module (shared) dav_svn_module (shared) authz_svn_module (shared)

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Apache2 return 404 for proxy requests before reaching WSGI

- by Alejandro Mezcua

I have a Django app running under Apache2 and mod_wsgi and, unfortunately, lots of requests trying to use the server as a proxy. The server is responding OK with 404 errors but the errors are generated by the Django (WSGI) app, which causes a high CPU usage. If I turn off the app and let Apache handle the response directly (send a 404), the CPU usage drops to almost 0 (mod_proxy is not enabled). Is there a way to configure Apache to respond directly to this kind of requests with an error before the request hits the WSGI app? I have seen that maybe mod_security would be an option, but I'd like to know if I can do it without it. EDIT. I'll explain it a bit more. In the logs I have lots of connections trying to use the server as a web proxy (e.g. connections like GET http://zzz.zzz/ HTTP/1.1 where zzz.zzz is an external domain, not mine). This requests are passed on to mod_wsgi which then return a 404 (as per my Django app). If I disable the app, as mod_proxy is disabled, Apache returns the error directly. What I'd finally like to do is prevent Apache from passing the request to the WSGI for invalid domains, that is, if the request is a proxy request, directly return the error and not execute the WSGI app. EDIT2. Here is the apache2 config, using VirtualHosts files in sites-enabled (i have removed email addresses and changed IPs to xxx, change the server alias to sample.sample.xxx). What I'd like is for Apache to reject any request that doesn't go to sample.sample.xxx with and error, that is, accept only relative requests to the server or fully qualified only to the actual ServerAlias. default: <VirtualHost *:80> ServerAdmin [email protected] ServerName X.X.X.X ServerAlias X.X.X.X DocumentRoot /var/www/default <Directory /> Options FollowSymLinks AllowOverride None </Directory> <Directory /var/www/> Options FollowSymLinks AllowOverride None Order allow,deny allow from all </Directory> ErrorDocument 404 "404" ErrorDocument 403 "403" ErrorDocument 500 "500" ErrorLog ${APACHE_LOG_DIR}/error.log LogLevel warn CustomLog ${APACHE_LOG_DIR}/access.log combined </VirtualHost> actual host: <VirtualHost *:80> ErrorDocument 404 "404" ErrorDocument 403 "403" ErrorDocument 500 "500" WSGIScriptAlias / /var/www/sample.sample.xxx/django.wsgi ServerAdmin [email protected] ServerAlias sample.sample.xxx ServerName sample.sample.xxx CustomLog /var/www/sample.sample.xxx/log/sample.sample.xxx-access.log combined Alias /robots.txt /var/www/sample.sample.xxx/static/robots.txt Alias /favicon.ico /var/www/sample.sample.xxx/static/favicon.ico AliasMatch ^/([^/]*\.css) /var/www/sample.sample.xxx/static/$1 Alias /static/ /var/www/sample.sample.xxx/static/ Alias /media/ /var/www/sample.sample.xxx/media/ <Directory /var/www/sample.sample.xxx/static/> Order deny,allow Allow from all </Directory> <Directory /var/www/sample.sample.xxx/media/> Order deny,allow Allow from all </Directory> </VirtualHost>

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Caveats with the runAllManagedModulesForAllRequests in IIS 7/8

- by Rick Strahl

One of the nice enhancements in IIS 7 (and now 8) is the ability to be able to intercept non-managed - ie. non ASP.NET served - requests from within ASP.NET managed modules. This opened up a ton of new functionality that could be applied across non-managed content using .NET code. I thought I had a pretty good handle on how IIS 7's Integrated mode pipeline works, but when I put together some samples last tonight I realized that the way that managed and unmanaged requests fire into the pipeline is downright confusing especially when it comes to the runAllManagedModulesForAllRequests attribute. There are a number of settings that can affect whether a managed module receives non-ASP.NET content requests such as static files or requests from other frameworks like PHP or ASP classic, and this is topic of this blog post. Native and Managed Modules The integrated mode IIS pipeline for IIS 7 and later - as the name suggests - allows for integration of ASP.NET pipeline events in the IIS request pipeline. Natively IIS runs unmanaged code and there are a host of native mode modules that handle the core behavior of IIS. If you set up a new IIS site or application without managed code support only the native modules are supported and fired without any interaction between native and managed code. If you use the Integrated pipeline with managed code enabled however things get a little more confusing as there both native modules and .NET managed modules can fire against the same IIS request. If you open up the IIS Modules dialog you see both managed and unmanaged modules. Unmanaged modules point at physical files on disk, while unmanaged modules point at .NET types and files referenced from the GAC or the current project's BIN folder. Both native and managed modules can co-exist and execute side by side and on the same request. When running in IIS 7 the IIS pipeline actually instantiates a the ASP.NET runtime (via the System.Web.PipelineRuntime class) which unlike the core HttpRuntime classes in ASP.NET receives notification callbacks when IIS integrated mode events fire. The IIS pipeline is smart enough to detect whether managed handlers are attached and if they're none these notifications don't fire, improving performance. The good news about all of this for .NET devs is that ASP.NET style modules can be used for just about every kind of IIS request. All you need to do is create a new Web Application and enable ASP.NET on it, and then attach managed handlers. Handlers can look at ASP.NET content (ie. ASPX pages, MVC, WebAPI etc. requests) as well as non-ASP.NET content including static content like HTML files, images, javascript and css resources etc. It's very cool that this capability has been surfaced. However, with that functionality comes a lot of responsibility. Because every request passes through the ASP.NET pipeline if managed modules (or handlers) are attached there are possible performance implications that come with it. Running through the ASP.NET pipeline does add some overhead. ASP.NET and Your Own Modules When you create a new ASP.NET project typically the Visual Studio templates create the modules section like this: <system.webServer> <validation validateIntegratedModeConfiguration="false" /> <modules runAllManagedModulesForAllRequests="true" > </modules> </system.webServer> Specifically the interesting thing about this is the runAllManagedModulesForAllRequest="true" flag, which seems to indicate that it controls whether any registered modules always run, even when the value is set to false. Realistically though this flag does not control whether managed code is fired for all requests or not. Rather it is an override for the preCondition flag on a particular handler. With the flag set to the default true setting, you can assume that pretty much every IIS request you receive ends up firing through your ASP.NET module pipeline and every module you have configured is accessed even by non-managed requests like static files. In other words, your module will have to handle all requests. Now so far so obvious. What's not quite so obvious is what happens when you set the runAllManagedModulesForAllRequest="false". You probably would expect that immediately the non-ASP.NET requests no longer get funnelled through the ASP.NET Module pipeline. But that's not what actually happens. For example, if I create a module like this:<add name="SharewareModule" type="HowAspNetWorks.SharewareMessageModule" /> by default it will fire against ALL requests regardless of the runAllManagedModulesForAllRequests flag. Even if the value runAllManagedModulesForAllRequests="false", the module is fired. Not quite expected. So what is the runAllManagedModulesForAllRequests really good for? It's essentially an override for managedHandler preCondition. If I declare my handler in web.config like this:<add name="SharewareModule" type="HowAspNetWorks.SharewareMessageModule" preCondition="managedHandler" /> and the runAllManagedModulesForAllRequests="false" my module only fires against managed requests. If I switch the flag to true, now my module ends up handling all IIS requests that are passed through from IIS. The moral of the story here is that if you intend to only look at ASP.NET content, you should always set the preCondition="managedHandler" attribute to ensure that only managed requests are fired on this module. But even if you do this, realize that runAllManagedModulesForAllRequests="true" can override this setting. runAllManagedModulesForAllRequests and Http Application Events Another place the runAllManagedModulesForAllRequest attribute affects is the Global Http Application object (typically in global.asax) and the Application_XXXX events that you can hook up there. So while the events there are dynamically hooked up to the application class, they basically behave as if they were set with the preCodition="managedHandler" configuration switch. The end result is that if you have runAllManagedModulesForAllRequests="true" you'll see every Http request passed through the Application_XXXX events, and you only see ASP.NET requests with the flag set to "false". What's all that mean? Configuring an application to handle requests for both ASP.NET and other content requests can be tricky especially if you need to mix modules that might require both. Couple of things are important to remember. If your module doesn't need to look at every request, by all means set a preCondition="managedHandler" on it. This will at least allow it to respond to the runAllManagedModulesForAllRequests="false" flag and then only process ASP.NET requests. Look really carefully to see whether you actually need runAllManagedModulesForAllRequests="true" in your applications as set by the default new project templates in Visual Studio. Part of the reason, this is the default because it was required for the initial versions of IIS 7 and ASP.NET 2 in order to handle MVC extensionless URLs. However, if you are running IIS 7 or later and .NET 4.0 you can use the ExtensionlessUrlHandler instead to allow you MVC functionality without requiring runAllManagedModulesForAllRequests="true": <handlers> <remove name="ExtensionlessUrlHandler-Integrated-4.0" /> <add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" /> </handlers> Oddly this is the default for Visual Studio 2012 MVC template apps, so I'm not sure why the default template still adds runAllManagedModulesForAllRequests="true" is - it should be enabled only if there's a specific need to access non ASP.NET requests. As a side note, it's interesting that when you access a static HTML resource, you can actually write into the Response object and get the output to show, which is trippy. I haven't looked closely to see how this works - whether ASP.NET just fires directly into the native output stream or whether the static requests are re-routed directly through the ASP.NET pipeline once a managed code module is detected. This doesn't work for all non ASP.NET resources - for example, I can't do the same with ASP classic requests, but it makes for an interesting demo when injecting HTML content into a static HTML page :-) Note that on the original Windows Server 2008 and Vista (IIS 7.0) you might need a HotFix in order for ExtensionLessUrlHandler to work properly for MVC projects. On my live server I needed it (about 6 months ago), but others have observed that the latest service updates have integrated this functionality and the hotfix is not required. On IIS 7.5 and later I've not needed any patches for things to just work. Plan for non-ASP.NET Requests It's important to remember that if you write a .NET Module to run on IIS 7, there's no way for you to prevent non-ASP.NET requests from hitting your module. So make sure you plan to support requests to extensionless URLs, to static resources like files. Luckily ASP.NET creates a full Request and full Response object for you for non ASP.NET content. So even for static files and even for ASP classic for example, you can look at Request.FilePath or Request.ContentType (in post handler pipeline events) to determine what content you are dealing with. As always with Module design make sure you check for the conditions in your code that make the module applicable and if a filter fails immediately exit - minimize the code that runs if your module doesn't need to process the request.© Rick Strahl, West Wind Technologies, 2005-2012Posted in IIS7 ASP.NET Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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Creating cookieless application on development machine with asp.net

- by zaladane

I am thinking about setting up a new domain to host static content on my website and have it cookieless just like Stackoverflow with their static domain. So before going ahead and buying the domain and setting it up I wanted to test it on my developement machine first under localhost (I have to mention that i am planning on having IIS running on my new domain for the static files). I therefore created a new application under IIS and disabled session state and forms authentication. When my main application needs resources like css, images and js , I use the path to the "static" application where they are hosted. The problem is that when I look at the request and the response for the requested files, they still have the session_id cookie defined as well as the asp.net authentication cookie. Is it at all possible to accomplish what i am trying to do on a development machine or do i have to just go ahead and purchase the new domain which hopefully with make things right? I tried to read about cookieless domain but can't figure out what i might be missing.

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Inverted schedctl usage in the JVM

- by Dave

The schedctl facility in Solaris allows a thread to request that the kernel defer involuntary preemption for a brief period. The mechanism is strictly advisory - the kernel can opt to ignore the request. Schedctl is typically used to bracket lock critical sections. That, in turn, can avoid convoying -- threads piling up on a critical section behind a preempted lock-holder -- and other lock-related performance pathologies. If you're interested see the man pages for schedctl_start() and schedctl_stop() and the schedctl.h include file. The implementation is very efficient. schedctl_start(), which asks that preemption be deferred, simply stores into a thread-specific structure -- the schedctl block -- that the kernel maps into user-space. Similarly, schedctl_stop() clears the flag set by schedctl_stop() and then checks a "preemption pending" flag in the block. Normally, this will be false, but if set schedctl_stop() will yield to politely grant the CPU to other threads. Note that you can't abuse this facility for long-term preemption avoidance as the deferral is brief. If your thread exceeds the grace period the kernel will preempt it and transiently degrade its effective scheduling priority. Further reading : US05937187 and various papers by Andy Tucker. We'll now switch topics to the implementation of the "synchronized" locking construct in the HotSpot JVM. If a lock is contended then on multiprocessor systems we'll spin briefly to try to avoid context switching. Context switching is wasted work and inflicts various cache and TLB penalties on the threads involved. If context switching were "free" then we'd never spin to avoid switching, but that's not the case. We use an adaptive spin-then-park strategy. One potentially undesirable outcome is that we can be preempted while spinning. When our spinning thread is finally rescheduled the lock may or may not be available. If not, we'll spin and then potentially park (block) again, thus suffering a 2nd context switch. Recall that the reason we spin is to avoid context switching. To avoid this scenario I've found it useful to enable schedctl to request deferral while spinning. But while spinning I've arranged for the code to periodically check or poll the "preemption pending" flag. If that's found set we simply abandon our spinning attempt and park immediately. This avoids the double context-switch scenario above. One annoyance is that the schedctl blocks for the threads in a given process are tightly packed on special pages mapped from kernel space into user-land. As such, writes to the schedctl blocks can cause false sharing on other adjacent blocks. Hopefully the kernel folks will make changes to avoid this by padding and aligning the blocks to ensure that one cache line underlies at most one schedctl block at any one time.

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Cisco ASA - Enable communication between same security level

- by Conor

I have recently inherited a network with a Cisco ASA (running version 8.2). I am trying to configure it to allow communication between two interfaces configured with the same security level (DMZ-DMZ) "same-security-traffic permit inter-interface" has been set, but hosts are unable to communicate between the interfaces. I am assuming that some NAT settings are causing my issue. Below is my running config: ASA Version 8.2(3) ! hostname asa enable password XXXXXXXX encrypted passwd XXXXXXXX encrypted names ! interface Ethernet0/0 switchport access vlan 400 ! interface Ethernet0/1 switchport access vlan 400 ! interface Ethernet0/2 switchport access vlan 420 ! interface Ethernet0/3 switchport access vlan 420 ! interface Ethernet0/4 switchport access vlan 450 ! interface Ethernet0/5 switchport access vlan 450 ! interface Ethernet0/6 switchport access vlan 500 ! interface Ethernet0/7 switchport access vlan 500 ! interface Vlan400 nameif outside security-level 0 ip address XX.XX.XX.10 255.255.255.248 ! interface Vlan420 nameif public security-level 20 ip address 192.168.20.1 255.255.255.0 ! interface Vlan450 nameif dmz security-level 50 ip address 192.168.10.1 255.255.255.0 ! interface Vlan500 nameif inside security-level 100 ip address 192.168.0.1 255.255.255.0 ! ftp mode passive clock timezone JST 9 same-security-traffic permit inter-interface same-security-traffic permit intra-interface object-group network DM_INLINE_NETWORK_1 network-object host XX.XX.XX.11 network-object host XX.XX.XX.13 object-group service ssh_2220 tcp port-object eq 2220 object-group service ssh_2251 tcp port-object eq 2251 object-group service ssh_2229 tcp port-object eq 2229 object-group service ssh_2210 tcp port-object eq 2210 object-group service DM_INLINE_TCP_1 tcp group-object ssh_2210 group-object ssh_2220 object-group service zabbix tcp port-object range 10050 10051 object-group service DM_INLINE_TCP_2 tcp port-object eq www group-object zabbix object-group protocol TCPUDP protocol-object udp protocol-object tcp object-group service http_8029 tcp port-object eq 8029 object-group network DM_INLINE_NETWORK_2 network-object host 192.168.20.10 network-object host 192.168.20.30 network-object host 192.168.20.60 object-group service imaps_993 tcp description Secure IMAP port-object eq 993 object-group service public_wifi_group description Service allowed on the Public Wifi Group. Allows Web and Email. service-object tcp-udp eq domain service-object tcp-udp eq www service-object tcp eq https service-object tcp-udp eq 993 service-object tcp eq imap4 service-object tcp eq 587 service-object tcp eq pop3 service-object tcp eq smtp access-list outside_access_in remark http traffic from outside access-list outside_access_in extended permit tcp any object-group DM_INLINE_NETWORK_1 eq www access-list outside_access_in remark ssh from outside to web1 access-list outside_access_in extended permit tcp any host XX.XX.XX.11 object-group ssh_2251 access-list outside_access_in remark ssh from outside to penguin access-list outside_access_in extended permit tcp any host XX.XX.XX.10 object-group ssh_2229 access-list outside_access_in remark http from outside to penguin access-list outside_access_in extended permit tcp any host XX.XX.XX.10 object-group http_8029 access-list outside_access_in remark ssh from outside to internal hosts access-list outside_access_in extended permit tcp any host XX.XX.XX.13 object-group DM_INLINE_TCP_1 access-list outside_access_in remark dns service to internal host access-list outside_access_in extended permit object-group TCPUDP any host XX.XX.XX.13 eq domain access-list dmz_access_in extended permit ip 192.168.10.0 255.255.255.0 any access-list dmz_access_in extended permit tcp any host 192.168.10.29 object-group DM_INLINE_TCP_2 access-list public_access_in remark Web access to DMZ websites access-list public_access_in extended permit object-group TCPUDP any object-group DM_INLINE_NETWORK_2 eq www access-list public_access_in remark General web access. (HTTP, DNS & ICMP and Email) access-list public_access_in extended permit object-group public_wifi_group any any pager lines 24 logging enable logging asdm informational mtu outside 1500 mtu public 1500 mtu dmz 1500 mtu inside 1500 no failover icmp unreachable rate-limit 1 burst-size 1 no asdm history enable arp timeout 60 global (outside) 1 interface global (dmz) 2 interface nat (public) 1 0.0.0.0 0.0.0.0 nat (dmz) 1 0.0.0.0 0.0.0.0 nat (inside) 1 0.0.0.0 0.0.0.0 static (inside,outside) tcp interface 2229 192.168.0.29 2229 netmask 255.255.255.255 static (inside,outside) tcp interface 8029 192.168.0.29 www netmask 255.255.255.255 static (dmz,outside) XX.XX.XX.13 192.168.10.10 netmask 255.255.255.255 dns static (dmz,outside) XX.XX.XX.11 192.168.10.30 netmask 255.255.255.255 dns static (dmz,inside) 192.168.0.29 192.168.10.29 netmask 255.255.255.255 static (dmz,public) 192.168.20.30 192.168.10.30 netmask 255.255.255.255 dns static (dmz,public) 192.168.20.10 192.168.10.10 netmask 255.255.255.255 dns static (inside,dmz) 192.168.10.0 192.168.0.0 netmask 255.255.255.0 dns access-group outside_access_in in interface outside access-group public_access_in in interface public access-group dmz_access_in in interface dmz route outside 0.0.0.0 0.0.0.0 XX.XX.XX.9 1 timeout xlate 3:00:00 timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02 timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00 mgcp-pat 0:05:00 timeout sip 0:30:00 sip_media 0:02:00 sip-invite 0:03:00 sip-disconnect 0:02:00 timeout sip-provisional-media 0:02:00 uauth 0:05:00 absolute timeout tcp-proxy-reassembly 0:01:00 dynamic-access-policy-record DfltAccessPolicy http server enable http 192.168.0.0 255.255.255.0 inside no snmp-server location no snmp-server contact snmp-server enable traps snmp authentication linkup linkdown coldstart crypto ipsec security-association lifetime seconds 28800 crypto ipsec security-association lifetime kilobytes 4608000 telnet timeout 5 ssh 192.168.0.0 255.255.255.0 inside ssh timeout 20 console timeout 0 dhcpd dns 61.122.112.97 61.122.112.1 dhcpd auto_config outside ! dhcpd address 192.168.20.200-192.168.20.254 public dhcpd enable public ! dhcpd address 192.168.0.200-192.168.0.254 inside dhcpd enable inside ! threat-detection basic-threat threat-detection statistics host threat-detection statistics access-list no threat-detection statistics tcp-intercept ntp server 130.54.208.201 source public webvpn ! class-map inspection_default match default-inspection-traffic ! ! policy-map type inspect dns preset_dns_map parameters message-length maximum client auto message-length maximum 512 policy-map global_policy class inspection_default inspect dns preset_dns_map inspect ftp inspect h323 h225 inspect h323 ras inspect ip-options inspect netbios inspect rsh inspect rtsp inspect skinny inspect esmtp inspect sqlnet inspect sunrpc inspect tftp inspect sip inspect xdmcp !

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Clipping polygons in XNA with stencil (not using spritebatch)

- by Blau

The problem... i'm drawing polygons, in this case boxes, and i want clip children polygons with its parent's client area. // Class Region public void Render(GraphicsDevice Device, Camera Camera) { int StencilLevel = 0; Device.Clear( ClearOptions.Stencil, Vector4.Zero, 0, StencilLevel ); Render( Device, Camera, StencilLevel ); } private void Render(GraphicsDevice Device, Camera Camera, int StencilLevel) { Device.SamplerStates[0] = this.SamplerState; Device.Textures[0] = this.Texture; Device.RasterizerState = RasterizerState.CullNone; Device.BlendState = BlendState.AlphaBlend; Device.DepthStencilState = DepthStencilState.Default; Effect.Prepare(this, Camera ); Device.DepthStencilState = GlobalContext.GraphicsStates.IncMask; Device.ReferenceStencil = StencilLevel; foreach ( EffectPass pass in Effect.Techniques[Technique].Passes ) { pass.Apply( ); Device.DrawUserIndexedPrimitives<VertexPositionColorTexture>( PrimitiveType.TriangleList, VertexData, 0, VertexData.Length, IndexData, 0, PrimitiveCount ); } foreach ( Region child in ChildrenRegions ) { child.Render( Device, Camera, StencilLevel + 1 ); } Effect.Prepare( this, Camera ); // This does not works Device.BlendState = GlobalContext.GraphicsStates.NoWriteColor; Device.DepthStencilState = GlobalContext.GraphicsStates.DecMask; Device.ReferenceStencil = StencilLevel; // This should be +1, but in that case the last drrawed is blue and overlap all foreach ( EffectPass pass in Effect.Techniques[Technique].Passes ) { pass.Apply( ); Device.DrawUserIndexedPrimitives<VertexPositionColorTexture>( PrimitiveType.TriangleList, VertexData, 0, VertexData.Length, IndexData, 0, PrimitiveCount ); } } public static class GraphicsStates { public static BlendState NoWriteColor = new BlendState( ) { ColorSourceBlend = Blend.One, AlphaSourceBlend = Blend.One, ColorDestinationBlend = Blend.InverseSourceAlpha, AlphaDestinationBlend = Blend.InverseSourceAlpha, ColorWriteChannels1 = ColorWriteChannels.None }; public static DepthStencilState IncMask = new DepthStencilState( ) { StencilEnable = true, StencilFunction = CompareFunction.Equal, StencilPass = StencilOperation.IncrementSaturation, }; public static DepthStencilState DecMask = new DepthStencilState( ) { StencilEnable = true, StencilFunction = CompareFunction.Equal, StencilPass = StencilOperation.DecrementSaturation, }; } How can achieve this? EDIT: I've just relized that the NoWriteColors.ColorWriteChannels1 should be NoWriteColors.ColorWriteChannels. :) Now it's clipping right. Any other approach?

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What's up with stat on Mac OS X/Darwin? Or filesystems without names...

- by Charles Stewart

In response to a question I asked on SO, Give the mount point of a path, one respondant suggested using stat to get the device name associated with the volume of a given path. This works nicely on Linux, but gives crazy results on Mac OS X 10.4. For my system, df and mount give: cas cas$ df Filesystem 512-blocks Used Avail Capacity Mounted on /dev/disk0s3 58342896 49924456 7906440 86% / devfs 194 194 0 100% /dev fdesc 2 2 0 100% /dev <volfs> 1024 1024 0 100% /.vol automount -nsl [166] 0 0 0 100% /Network automount -fstab [170] 0 0 0 100% /automount/Servers automount -static [170] 0 0 0 100% /automount/static /dev/disk2s1 163577856 23225520 140352336 14% /Volumes/Snapshot /dev/disk2s2 409404102 5745938 383187960 1% /Volumes/Sparse cas cas$ mount /dev/disk0s3 on / (local, journaled) devfs on /dev (local) fdesc on /dev (union) <volfs> on /.vol automount -nsl [166] on /Network (automounted) automount -fstab [170] on /automount/Servers (automounted) automount -static [170] on /automount/static (automounted) /dev/disk2s1 on /Volumes/Snapshot (local, nodev, nosuid, journaled) /dev/disk2s2 on /Volumes/Sparse (asynchronous, local, nodev, nosuid) Trying to get the devices from the mount points, though: cas cas$ df | grep -e/ | awk '{print $NF}' | while read line; do echo $line $(stat -f"%Sdr" $line); done / disk0s3r /dev ???r /dev ???r /.vol ???r /Network ???r /automount/Servers ???r /automount/static ???r /Volumes/Snapshot disk2s1r /Volumes/Sparse disk2s2r Here, I'm feeding each of the mount points scraped from df to stat, outputting the results of the "%Sdr" format string, which is supposed to be the device name: Cf. stat(1) man page: The special output specifier S may be used to indicate that the output, if applicable, should be in string format. May be used in combination with: ... dr Display actual device name. What's going on? Is it a bug in stat, or some Darwin VFS weirdness? Postscript Per Andrew McGregor, try passing "%Sd" to stat for more weirdness. It lists some apparently arbitrary subset of files from CWD...

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What's up with stat on Macos/Darwin? Or filesystems without names...

- by Charles Stewart

In response to a question I asked on SO, Give the mount point of a path, one respondant suggested using stat to get the device name associated with the volume of a given path. This works nicely on Linux, but gives crazy results on Macos 10.4. For my system, df and mount give: cas cas$ df Filesystem 512-blocks Used Avail Capacity Mounted on /dev/disk0s3 58342896 49924456 7906440 86% / devfs 194 194 0 100% /dev fdesc 2 2 0 100% /dev 1024 1024 0 100% /.vol automount -nsl [166] 0 0 0 100% /Network automount -fstab [170] 0 0 0 100% /automount/Servers automount -static [170] 0 0 0 100% /automount/static /dev/disk2s1 163577856 23225520 140352336 14% /Volumes/Snapshot /dev/disk2s2 409404102 5745938 383187960 1% /Volumes/Sparse cas cas$ mount /dev/disk0s3 on / (local, journaled) devfs on /dev (local) fdesc on /dev (union) on /.vol automount -nsl [166] on /Network (automounted) automount -fstab [170] on /automount/Servers (automounted) automount -static [170] on /automount/static (automounted) /dev/disk2s1 on /Volumes/Snapshot (local, nodev, nosuid, journaled) /dev/disk2s2 on /Volumes/Sparse (asynchronous, local, nodev, nosuid) Trying to get the devices from the mount points, though: cas cas$ df | grep -e/ | awk '{print $NF}' | while read line; do echo $line $(stat -f"%Sdr" $line); done / disk0s3r /dev ???r /dev ???r /.vol ???r /Network ???r /automount/Servers ???r /automount/static ???r /Volumes/Snapshot disk2s1r /Volumes/Sparse disk2s2r Here, I'm feeding each of the mount points scraped from df to stat, outputing the results of the "%Sdr" format string, which is supposed to be the device name: Cf. stat(1) man page: The special output specifier S may be used to indicate that the output, if applicable, should be in string format. May be used in combination with: ... dr Display actual device name. What's going on? Is it a bug in stat, or some Darwin VFS weirdness? Postscript Per Andrew McGregor, try passing "%Sd" to stat for more weirdness. It lists some apparently arbitrary subset of files from CWD...

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Tracking down rogue disk usage

- by Amadan

I found several other questions regarding the theory behind my problem (e.g. this, this), but I don't know how to apply the answers to my machine. # du -hsx / 11000283 / # df -kT / Filesystem Type 1K-blocks Used Available Use% Mounted on /dev/mapper/csisv13-root ext4 516032952 361387456 128432532 74% / There is a big difference between 11G (du) and 345G (df). Where are the remaining 334G? It's not in deleted files. There was only one, it was short, and I truncated it just in case. This is what remains: # lsof -a +L1 / COMMAND PID USER FD TYPE DEVICE SIZE/OFF NLINK NODE NAME zabbix_ag 4902 zabbix 1w REG 252,0 0 0 28836028 /var/log/zabbix-agent/zabbix_agentd.log.1 (deleted) zabbix_ag 4902 zabbix 2w REG 252,0 0 0 28836028 /var/log/zabbix-agent/zabbix_agentd.log.1 (deleted) zabbix_ag 4906 zabbix 1w REG 252,0 0 0 28836028 /var/log/zabbix-agent/zabbix_agentd.log.1 (deleted) zabbix_ag 4906 zabbix 2w REG 252,0 0 0 28836028 /var/log/zabbix-agent/zabbix_agentd.log.1 (deleted) zabbix_ag 4907 zabbix 1w REG 252,0 0 0 28836028 /var/log/zabbix-agent/zabbix_agentd.log.1 (deleted) zabbix_ag 4907 zabbix 2w REG 252,0 0 0 28836028 /var/log/zabbix-agent/zabbix_agentd.log.1 (deleted) zabbix_ag 4908 zabbix 1w REG 252,0 0 0 28836028 /var/log/zabbix-agent/zabbix_agentd.log.1 (deleted) zabbix_ag 4908 zabbix 2w REG 252,0 0 0 28836028 /var/log/zabbix-agent/zabbix_agentd.log.1 (deleted) zabbix_ag 4909 zabbix 1w REG 252,0 0 0 28836028 /var/log/zabbix-agent/zabbix_agentd.log.1 (deleted) zabbix_ag 4909 zabbix 2w REG 252,0 0 0 28836028 /var/log/zabbix-agent/zabbix_agentd.log.1 (deleted) zabbix_ag 4910 zabbix 1w REG 252,0 0 0 28836028 /var/log/zabbix-agent/zabbix_agentd.log.1 (deleted) zabbix_ag 4910 zabbix 2w REG 252,0 0 0 28836028 /var/log/zabbix-agent/zabbix_agentd.log.1 (deleted) I rebooted to see if fsck does anything. But, from /var/log/boot.log, it seems there are no issues: /dev/mapper/server-root: clean, 3936097/32768000 files, 125368568/131064832 blocks Thinking maybe someone overzealously reserved root space, I checked the master record: # tune2fs -l /dev/mapper/server-root tune2fs 1.42 (29-Nov-2011) Filesystem volume name: <none> Last mounted on: / Filesystem UUID: 86430ade-cea7-46ce-979c-41769a41ecbe Filesystem magic number: 0xEF53 Filesystem revision #: 1 (dynamic) Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize Filesystem flags: signed_directory_hash Default mount options: user_xattr acl Filesystem state: clean Errors behavior: Continue Filesystem OS type: Linux Inode count: 32768000 Block count: 131064832 Reserved block count: 6553241 Free blocks: 5696264 Free inodes: 28831903 First block: 0 Block size: 4096 Fragment size: 4096 Reserved GDT blocks: 992 Blocks per group: 32768 Fragments per group: 32768 Inodes per group: 8192 Inode blocks per group: 512 Flex block group size: 16 Filesystem created: Fri Feb 1 13:44:04 2013 Last mount time: Tue Aug 19 16:56:13 2014 Last write time: Fri Feb 1 13:51:28 2013 Mount count: 9 Maximum mount count: -1 Last checked: Fri Feb 1 13:44:04 2013 Check interval: 0 (<none>) Lifetime writes: 1215 GB Reserved blocks uid: 0 (user root) Reserved blocks gid: 0 (group root) First inode: 11 Inode size: 256 Required extra isize: 28 Desired extra isize: 28 Journal inode: 8 First orphan inode: 28836028 Default directory hash: half_md4 Directory Hash Seed: bca55ff5-f530-48d1-8347-25c004f66d43 Journal backup: inode blocks The system is: # uname -a Linux server 3.2.0-67-generic #101-Ubuntu SMP Tue Jul 15 17:46:11 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux # cat /etc/lsb-release DISTRIB_ID=Ubuntu DISTRIB_RELEASE=12.04 DISTRIB_CODENAME=precise DISTRIB_DESCRIPTION="Ubuntu 12.04.2 LTS" Does anyone have any tips on what exactly to do to find and hopefully reclaim the missing space?

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How can I simulate blocking RTMP over port 80 on Windows?

- by Christian Nunciato

It seems like this should be so simple, but since this isn't my area of expertise, I'm having a hell of a time figuring out how to do it. Basically, I have a Flash app and I'm connecting to a Flash Media Server to stream some content. The URL I'm using to do this, for example, looks like this: rtmp://someserver.com/some/path/mp3:somefile Everything works -- but that's sort of the problem. When I'm trying to do is simulate my users attempting to play back my media under more restrictive conditions than the ones I have here (i.e., none) -- namely being stuck behind firewalls or proxy servers that block access to RTMP streams. Flash, according to Adobe, is equipped to handle proxy servers and firewalls automatically, like so (from the docs): When you do not specify a port number in an RTMP address, Flash will attempt to connect to port 1935. If it fails it will then try to connect to port 443; if that fails, it will try port 80. [And if that fails, it will attempt to connect via RTMPT (i.e., HTTP tunneling) on port 80.] So no coding is required to access ports 1935, 443, or port 80 if you do not specify a port in the RTMP address. The problem I'm having is setting up a reliable environment in which to test that this behavior actually happens. I'm on a Windows machine, for example, so with Windows Firewall, I can block certain ports and protocols (1935, 443), but I don't want to block port 80, because the final fallback protocol (RTMPT) is supposed to run on port 80, and Windows Firewall only gives me enough granularity (as far as I know, anyway) to block "all outbound TCP traffic to remote port 80" -- that is, I can't, apparently, block "all outbound RTMP traffic to port 80" while leaving RTMPT traffic to port 80 unaffected. My understanding thus far is that I'll probably need to set up a proxy server to do this. Is this correct? Or is there a simpler way (on Win 7, at least) to filter out RTMP to 1935, RTMP to 443, RTMP to 80, but still allow RTMPT to 80 (where all four hostnames are identical)? And if I do have to set up a proxy server, what's the simplest way to go on Windows? I've set up WinProxy, which seems a bit janky but apparently works -- but then what I can't figure out is how to tell Windows to force all TCP traffic (including RTMP, RTMPT and HTTO) through this proxy server so I can turn around and reject the requests for RTMP. Any help would be hugely appreciated. This isn't my realm of expertise and I've alreasdy spent more time on it than I probably should. :)

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vSphere ESX 5.5 hosts cannot connect to NFS Server

- by Gerald

Summary: My problem is I cannot use the QNAP NFS Server as an NFS datastore from my ESX hosts despite the hosts being able to ping it. I'm utilising a vDS with LACP uplinks for all my network traffic (including NFS) and a subnet for each vmkernel adapter. Setup: I'm evaluating vSphere and I've got two vSphere ESX 5.5 hosts (node1 and node2) and each one has 4x NICs. I've teamed them all up using LACP/802.3ad with my switch and then created a distributed switch between the two hosts with each host's LAG as the uplink. All my networking is going through the distributed switch, ideally, I want to take advantage of DRS and the redundancy. I have a domain controller VM ("Central") and vCenter VM ("vCenter") running on node1 (using node1's local datastore) with both hosts attached to the vCenter instance. Both hosts are in a vCenter datacenter and a cluster with HA and DRS currently disabled. I have a QNAP TS-669 Pro (Version 4.0.3) (TS-x69 series is on VMware Storage HCL) which I want to use as the NFS server for my NFS datastore, it has 2x NICs teamed together using 802.3ad with my switch. vmkernel.log: The error from the host's vmkernel.log is not very useful: NFS: 157: Command: (mount) Server: (10.1.2.100) IP: (10.1.2.100) Path: (/VM) Label (datastoreNAS) Options: (None) cpu9:67402)StorageApdHandler: 698: APD Handle 509bc29f-13556457 Created with lock[StorageApd0x411121] cpu10:67402)StorageApdHandler: 745: Freeing APD Handle [509bc29f-13556457] cpu10:67402)StorageApdHandler: 808: APD Handle freed! cpu10:67402)NFS: 168: NFS mount 10.1.2.100:/VM failed: Unable to connect to NFS server. Network Setup: Here is my distributed switch setup (JPG). Here are my networks. 10.1.1.0/24 VM Management (VLAN 11) 10.1.2.0/24 Storage Network (NFS, VLAN 12) 10.1.3.0/24 VM vMotion (VLAN 13) 10.1.4.0/24 VM Fault Tolerance (VLAN 14) 10.2.0.0/24 VM's Network (VLAN 20) vSphere addresses 10.1.1.1 node1 Management 10.1.1.2 node2 Management 10.1.2.1 node1 vmkernel (For NFS) 10.1.2.2 node2 vmkernel (For NFS) etc. Other addresses 10.1.2.100 QNAP TS-669 (NFS Server) 10.2.0.1 Domain Controller (VM on node1) 10.2.0.2 vCenter (VM on node1) I'm using a Cisco SRW2024P Layer-2 switch (Jumboframes enabled) with the following setup: LACP LAG1 for node1 (Ports 1 through 4) setup as VLAN trunk for VLANs 11-14,20 LACP LAG2 for my router (Ports 5 through 8) setup as VLAN trunk for VLANs 11-14,20 LACP LAG3 for node2 (Ports 9 through 12) setup as VLAN trunk for VLANs 11-14,20 LACP LAG4 for the QNAP (Ports 23 and 24) setup to accept untagged traffic into VLAN 12 Each subnet is routable to another, although, connections to the NFS server from vmk1 shouldn't need it. All other traffic (vSphere Web Client, RDP etc.) goes through this setup fine. I tested the QNAP NFS server beforehand using ESX host VMs atop of a VMware Workstation setup with a dedicated physical NIC and it had no problems. The ACL on the NFS Server share is permissive and allows all subnet ranges full access to the share. I can ping the QNAP from node1 vmk1, the adapter that should be used to NFS: ~ # vmkping -I vmk1 10.1.2.100 PING 10.1.2.100 (10.1.2.100): 56 data bytes 64 bytes from 10.1.2.100: icmp_seq=0 ttl=64 time=0.371 ms 64 bytes from 10.1.2.100: icmp_seq=1 ttl=64 time=0.161 ms 64 bytes from 10.1.2.100: icmp_seq=2 ttl=64 time=0.241 ms Netcat does not throw an error: ~ # nc -z 10.1.2.100 2049 Connection to 10.1.2.100 2049 port [tcp/nfs] succeeded! The routing table of node1: ~ # esxcfg-route -l VMkernel Routes: Network Netmask Gateway Interface 10.1.1.0 255.255.255.0 Local Subnet vmk0 10.1.2.0 255.255.255.0 Local Subnet vmk1 10.1.3.0 255.255.255.0 Local Subnet vmk2 10.1.4.0 255.255.255.0 Local Subnet vmk3 default 0.0.0.0 10.1.1.254 vmk0 VM Kernel NIC info ~ # esxcfg-vmknic -l Interface Port Group/DVPort IP Family IP Address Netmask Broadcast MAC Address MTU TSO MSS Enabled Type vmk0 133 IPv4 10.1.1.1 255.255.255.0 10.1.1.255 00:50:56:66:8e:5f 1500 65535 true STATIC vmk0 133 IPv6 fe80::250:56ff:fe66:8e5f 64 00:50:56:66:8e:5f 1500 65535 true STATIC, PREFERRED vmk1 164 IPv4 10.1.2.1 255.255.255.0 10.1.2.255 00:50:56:68:f5:1f 1500 65535 true STATIC vmk1 164 IPv6 fe80::250:56ff:fe68:f51f 64 00:50:56:68:f5:1f 1500 65535 true STATIC, PREFERRED vmk2 196 IPv4 10.1.3.1 255.255.255.0 10.1.3.255 00:50:56:66:18:95 1500 65535 true STATIC vmk2 196 IPv6 fe80::250:56ff:fe66:1895 64 00:50:56:66:18:95 1500 65535 true STATIC, PREFERRED vmk3 228 IPv4 10.1.4.1 255.255.255.0 10.1.4.255 00:50:56:72:e6:ca 1500 65535 true STATIC vmk3 228 IPv6 fe80::250:56ff:fe72:e6ca 64 00:50:56:72:e6:ca 1500 65535 true STATIC, PREFERRED Things I've tried/checked: I'm not using DNS names to connect to the NFS server. Checked MTU. Set to 9000 for vmk1, dvSwitch and Cisco switch and QNAP. Moved QNAP onto VLAN 11 (VM Management, vmk0) and gave it an appropriate address, still had same issue. Changed back afterwards of course. Tried initiating the connection of NAS datastore from vSphere Client (Connected to vCenter or directly to host), vSphere Web Client and the host's ESX Shell. All resulted in the same problem. Tried a path name of "VM", "/VM" and "/share/VM" despite not even having a connection to server. I plugged in a linux system (10.1.2.123) into a switch port configured for VLAN 12 and tried mounting the NFS share 10.1.2.100:/VM, it worked successfully and I had read-write access to it I tried disabling the firewall on the ESX host esxcli network firewall set --enabled false I'm out of ideas on what to try next. The things I'm doing differently from my VMware Workstation setup is the use of LACP with a physical switch and a virtual distributed switch between the two hosts. I'm guessing the vDS is probably the source of my troubles but I don't know how to fix this problem without eliminating it.

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RPi and Java Embedded GPIO: Using Java to read input

- by hinkmond

Now that we've learned about using Java code to control the output of the Raspberry Pi GPIO ports (by lighting up LEDs from a Java app on the RPi for now and noting in the future the same Java code can be used to drive industrial automation or medical equipment, etc.), let's move on to learn about reading input from the RPi GPIO using Java code. As before, we need to start out with the necessary hardware. For this exercise we will connect a Static Electricity Detector to the RPi GPIO port and read the value of that sensor using Java code. The circuit we'll use is from William J. Beaty and is described at this Web link. See: Static Electricity Detector He calls it an "Electric Charge" detector, which is a bit misleading. A Field Effect Transistor is subject to nearby electro-magnetic fields, such as a static charge on a nearby object, not really an electric charge. So, this sensor will detect static electricity (or ghosts if you are into paranormal activity ). Take a look at the circuit and in the next blog posts we'll step through how to connect it to the GPIO port of your RPi and then how to write Java code to access this fun sensor. Hinkmond

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What do you think of the EntLib 5.0 configuration tool?

Hello again! Its been a while, I know. Ive been busy over the last few months with several projects, some of them software related, and one of them human my son Jesse was born on 26 February 2010. Fun times! Meanwhile, back in Redmond, the p&p team has been busy working on Enterprise Library 5.0 see Grigoris announcement for details on the beta. Theres a ton of new stuff in this release, but theres one big new feature that hasnt received a lot of attention that Im keen to hear your perspectives on. The change is the biggest overhaul to the configuration tool since Enterprise Library was launched. If you havent yet grabbed the EntLib 5.0 beta, heres a before and after shot of the config tool: Enterprise Library 4.1 config tool Enterprise Library 5.0 (beta 1) config tool The tool has been rebuilt from the ground up in response to some feedback and usability studies from the previous version of the tool. But is this a step in the right direction? Id love to hear what you think. If youve downloaded EntLib 5.0 and tried out the tool, please share your thoughts on: First impressions. Is the tool easy to understand? Easy to find what youre looking for? Easy to read existing configuration? Pretty? Ease of use for real life tasks. Rather than make up your own tasks, here are a few sample scenarios you might want to try: Configure the data access block with a SQL Server connection called Audit that points to a database called Audit on a server called DB Configure the logging block so that any log entries in the Audit category are written to both the Event Log and the Audit database (see above) Configure the validation block with a ruleset called Email Address that uses an appropriate regular expression for e-mail addresses Configure the policy injection block such that any calls to classes in the MyCompany.Security namespace are logged before and after the call using the Audit category (see above) Comparison with the old config tool. What do you like better in the new tool? What did you like better in the old tool? How do you rate your level of expertise using the old tool? Keep in mind that I no longer work in the p&p team, so I cant say how any of this feedback will be used (although Im sure the team is listening!). However since Ive invested so much time in Enterprise Library, both in leading the team and using the product on real projects Im very interested to hear what you all think of the tools new direction.Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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Adding operation in middle of complex sequence diagram in visio 2003

- by James

I am using Microsoft Visio 2003 to define static classes with operations/methods and a sequence diagrams referring to these classes. The sequence diagram is almost done, but i realized that i missed one operation in middle of the diagram. When i try to move rest of the sequences down by selecting it as a block, all the operations in the block loose link with static diagrams. ( Methods which were referred to static classes as fun(), became fun, which means that now they no longer refer to static diagrams and any future changes would not be reflected in dynamic sequence diagrams automatically.) The sequence diagrams have grown to A3 size paper and i have many of such diagrams which needs correction. Manually moving the operations one by one would involve lots of effort. Could someone kindly suggest a way to overcome this problem?

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Design guideline for saving big byte stream in c# [migrated]

- by Praveen

I have an application where I am receiving big byte array very fast around per 50 miliseconds. The byte array contains some information like file name etc. The data (byte array ) may come from several sources. Each time I receive the data, I have to find the file name and save the data to that file name. I need some guide lines to how should I design it so that it works efficient. Following is my code... public class DataSaver { private static Dictionary<string, FileStream> _dictFileStream; public static void SaveData(byte[] byteArray) { string fileName = GetFileNameFromArray(byteArray); FileStream fs = GetFileStream(fileName); fs.Write(byteArray, 0, byteArray.Length); } private static FileStream GetFileStream(string fileName) { FileStream fs; bool hasStream = _dictFileStream.TryGetValue(fileName, out fs); if (!hasStream) { fs = new FileStream(fileName, FileMode.Append); _dictFileStream.Add(fileName, fs); } return fs; } public static void CloseSaver() { foreach (var key in _dictFileStream.Keys) { _dictFileStream[key].Close(); } } } How can I improve this code ? I need to create a thread maybe to do the saving.

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Restrictive routing best practices for Google App Engine with python?

- by Aleksandr Makov

Say I have a simple structure: app = webapp2.WSGIApplication([ (r'/', 'pages.login'), (r'/profile', 'pages.profile'), (r'/dashboard', 'pages.dash'), ], debug=True) Basically all pages require authentication except for the login. If visitor tries to reach a restrictive page and he isn't authorized (or lacks privileges) then he gets redirected to the login view. The question is about the routing design. Should I check the auth and ACL privs in each of the modules (pages.profile and pages.dash from example above), or just pass all requests through the single routing mechanism: app = webapp2.WSGIApplication([ (r'/', 'pages.login'), (r'/.+', 'router') ], debug=True) I'm still quite new to the GAE, but my app requires authentication as well as ACL. I'm aware that there's login directive on the server config level, but I don't know how it works and how I can tight it with my ACL logic and what's worse I cannot estimate time needed to get it running. Besides, it looks only to provide only 2 user groups: admin and user. In any case, that's the configuration I use: handlers: - url: /favicon.ico static_files: static/favicon.ico upload: static/favicon.ico - url: /static/* static_dir: static - url: .* script: main.app secure: always Or I miss something here and ACL can be set in the config file? Thanks.

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How to switch off wifi on startup or from the console

- by mit

I have installed ubuntu 10.04 on a laptop. Wifi is switched on by default on startup. I can disable it rightclicking the network manager icon in the gnome bar. How can I set it to have wifi switched off as default? Alternatively, how can I switch off wifi on the console? I tried already the rfkill command but it does not list any devices and it does not switch off wifi, I tried different parameters. This is a standard install of the Ubuntu 10.04 i386 Desktop Live CD on an IBM T40 Laptop. EDIT A: This is the output of some rfkill commands on my system, and it does not affect the wifi of the laptop: $ rfkill --help Usage: rfkill [options] command Options: --version show version (0.4) Commands: help event list [IDENTIFIER] block IDENTIFIER unblock IDENTIFIER where IDENTIFIER is the index no. of an rfkill switch or one of: <idx> all wifi wlan bluetooth uwb ultrawideband wimax wwan gps fm $ rfkill list $ rfkill list wifi $ rfkill list all $ rfkill list wlan $ sudo rfkill list all $ sudo rfkill block all $ sudo rfkill block wlan $ sudo rfkill block wifi $ EDIT B: Now I found out that sudo ifconfig eth1 down turns it off. And I can turn it on through the gnome network applet again. But the applet does not reflect the change from the commandline, it stills believes wifi is switched on. I have to switch it off and on again on the applet to switch it on again, when I switched it off from the console. Is there a better way? This is what the syslog looks like when I switch wireless off and on again from the network manager: NetworkManager: <info> (eth1): device state change: 3 -> 2 (reason 0) NetworkManager: <info> (eth1): deactivating device (reason: 0). NetworkManager: <info> Policy set '24' (eth0) as default for routing and DNS. NetworkManager: <info> (eth1): taking down device. avahi-daemon[660]: Withdrawing address record for fe80::202:8aff:feba:d798 on eth1. kernel: [ 971.472116] airo(eth1): cmd:3 status:7f03 rsp0:0 rsp1:0 rsp2:0 NetworkManager: <info> (eth1): bringing up device. NetworkManager: <info> (eth1): supplicant interface state: starting -> ready NetworkManager: <info> (eth1): device state change: 2 -> 3 (reason 42) avahi-daemon[660]: Registering new address record for fe80::202:8aff:feba:d798 on eth1.*. kernel: [ 965.512048] eth1: no IPv6 routers present

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The best way to have a pointer to several methods - critique requested

- by user827992

I'm starting with a short introduction of what i know from the C language: a pointer is a type that stores an adress or a NULL the * operator reads the left value of the variable on its right and use this value as address and reads the value of the variable at that address the & operator generate a pointer to the variable on its right so i was thinking that in C++ the pointers can work this way too, but i was wrong, to generate a pointer to a static method i have to do this: #include <iostream> class Foo{ public: static void dummy(void){ std::cout << "I'm dummy" << std::endl; }; }; int main(){ void (*p)(); p = Foo::dummy; // step 1 p(); p = &(Foo::dummy); // step 2 p(); p = Foo; // step 3 p->dummy(); return(0); } now i have several questions: why step 1 works why step 2 works too, looks like a "pointer to pointer" for p to me, very different from step 1 why step 3 is the only one that doesn't work and is the only one that makes some sort of sense to me, honestly how can i write an array of pointers or a pointer to pointers structure to store methods ( static or non-static from real objects ) what is the best syntax and coding style for generating a pointer to a method?

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Creating smooth lighting transitions using tiles in HTML5/JavaScript game

- by user12098

I am trying to implement a lighting effect in an HTML5/JavaScript game using tile replacement. What I have now is kind of working, but the transitions do not look smooth/natural enough as the light source moves around. Here's where I am now: Right now I have a background map that has a light/shadow spectrum PNG tilesheet applied to it - going from darkest tile to completely transparent. By default the darkest tile is drawn across the entire level on launch, covering all other layers etc. I am using my predetermined tile sizes (40 x 40px) to calculate the position of each tile and store its x and y coordinates in an array. I am then spawning a transparent 40 x 40px "grid block" entity at each position in the array The engine I'm using (ImpactJS) then allows me to calculate the distance from my light source entity to every instance of this grid block entity. I can then replace the tile underneath each of those grid block tiles with a tile of the appropriate transparency. Currently I'm doing the calculation like this in each instance of the grid block entity that is spawned on the map: var dist = this.distanceTo( ig.game.player ); var percentage = 100 * dist / 960; if (percentage < 2) { // Spawns tile 64 of the shadow spectrum tilesheet at the specified position ig.game.backgroundMaps[2].setTile( this.pos.x, this.pos.y, 64 ); } else if (percentage < 4) { ig.game.backgroundMaps[2].setTile( this.pos.x, this.pos.y, 63 ); } else if (percentage < 6) { ig.game.backgroundMaps[2].setTile( this.pos.x, this.pos.y, 62 ); } // etc... (sorry about the weird spacing, I still haven't gotten the hang of pasting code in here properly) The problem is that like I said, this type of calculation does not make the light source look very natural. Tile switching looks too sharp whereas ideally they would fade in and out smoothly using the spectrum tilesheet (I copied the tilesheet from another game that manages to do this, so I know it's not a problem with the tile shades. I'm just not sure how the other game is doing it). I'm thinking that perhaps my method of using percentages to switch out tiles could be replaced with a better/more dynamic proximity forumla of some sort that would allow for smoother transitions? Might anyone have any ideas for what I can do to improve the visuals here, or a better way of calculating proximity with the information I'm collecting about each tile? (PS: I'm reposting this from Stack Overflow at someone's suggestion, sorry about the duplicate!)

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