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• Best way to convert a Unicode URL to ASCII (UTF-8 percent-escaped) in Python?

  - by benhoyt

  I'm wondering what's the best way -- or if there's a simple way with the standard library -- to convert a URL with Unicode chars in the domain name and path to the equivalent ASCII URL, encoded with domain as IDNA and the path %-encoded, as per RFC 3986. I get from the user a URL in UTF-8. So if they've typed in http://?.ws/? I get 'http://\xe2\x9e\xa1.ws/\xe2\x99\xa5' in Python. And what I want out is the ASCII version: 'http://xn--hgi.ws/%E2%99%A5'. What I do at the moment is split the URL up into parts via a regex, and then manually IDNA-encode the domain, and separately encode the path and query string with different urllib.quote() calls. # url is UTF-8 here, eg: url = u'http://?.ws/?'.encode('utf-8') match = re.match(r'([a-z]{3,5})://(.+\.[a-z0-9]{1,6})' r'(:\d{1,5})?(/.*?)(\?.*)?$', url, flags=re.I) if not match: raise BadURLException(url) protocol, domain, port, path, query = match.groups() try: domain = unicode(domain, 'utf-8') except UnicodeDecodeError: return '' # bad UTF-8 chars in domain domain = domain.encode('idna') if port is None: port = '' path = urllib.quote(path) if query is None: query = '' else: query = urllib.quote(query, safe='=&?/') url = protocol + '://' + domain + port + path + query # url is ASCII here, eg: url = 'http://xn--hgi.ws/%E3%89%8C' Is this correct? Any better suggestions? Is there a simple standard-library function to do this?

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• XML-RPC over SSL with Ruby: end of file reached (EOFError)

  - by Michael Conigliaro

  Hello, I have some very simple Ruby code that is attempting to do XML-RPC over SSL: require 'xmlrpc/client' require 'pp' server = XMLRPC::Client.new2("https://%s:%d/" % [ 'api.ultradns.net', 8755 ]) pp server.call2('UDNS_OpenConnection', 'sponsor', 'username', 'password') The problem is that it always results in the following EOFError exception: /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/net/protocol.rb:135:in `sysread': end of file reached (EOFError) So it appears that after doing the POST, I don't get anything back. Interestingly, this is the behavior I would expect if I tried to make an HTTP connection on the HTTPS port (or visa versa), and I actually do get the same exact exception if I change the protocol. Everything I've looked at indicates that using "https://" in the URL is enough to enable SSL, but I'm starting wonder if I've missed something. Note that Even though the credentials I'm using in the RPC are made up, I'm expecting to at least get back an XML error page (similar to if you access https://api.ultradns.net:8755/ with a web browser). I've tried running this code on OSX and Linux with the exact same result, so I have to conclude that I'm just doing something wrong here. Does anyone have any examples of doing XML-RPC over SSL with Ruby?

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• Choosing a method for a webservice

  - by Wrikken

  I'm asked to set up a new webservice which should be easily usable in whatever language (php, .NET, Java, etc.) possible. Of course rolling my own can be done, accepting different content-types (xml / x-www-form-urlencoded (normal post) / json / etc.), but an existing method or mechanism would of course be prefered, cutting down time spent on development for the consumers of the service. The webservice does accept modifications / sets (it is not only simply data retrieval), but those will most likely be quite a lot less then gets (we estimate about 2.5% sets, 97.5 gets). The term webservice here indicates the protocol should go over HTTP, not being able to implement it totally client sided (javascript in the end-users browser etc.), as it needs specific user authentication. Both gets and sets are pretty light on the parameter count (usually 1 to 4). Methods like REST (which I'd prefer for only gets), XML-RPC & SOAP (might be a bit overkill, but has the advantage of explicitly defined methods and returns) are the usual suspects. What in your opinion / experience is the most widely 'spoken' and most easily implementable protocol in different languages (seen from the consumers' viewpoint) which could fullfill this need?

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• Linux network stack : adding protocols with an LKM and dev_add_pack

  - by agent0range

  Hello, I have recently been trying to familiarize myself with the Linux Networking stack and device drivers (have both similarly named O'Reilly books) with the eventual goal of offloading UDP. I have already implemented UDP on the NIC but now the hard part... Rather than ask for assistance on this larger goal I was hoping someone could clarify for me a particular snippet I found that is part of a LKM which registeres a new protocol (OTP) that acts as a filter between the device driver and network stack. http://www.phrack.org/archives/55/p55_0x0c_Building%20Into%20The%20Linux%20Network%20Layer_by_lifeline%20&%20kossak.txt (Note: this Phrack article contains three different modules, code for the OTP is at the bottom of the page) In the init function of his example he has: otp_proto.type = htons(ETH_P_ALL); otp_proto.func = otp_func; dev_add_pack(&otp_proto); which (if I understand correctly) should register otp_proto as a packet sniffer and put it into the ptype_all data structure. My question is about the dev_add_pack. Is it the case that the protocol being registered as a filter will always be placed at this layer between L2 and the device driver? Or, for instance could I make such a filtering occur between the application and transport layers (analyze socket parameters) using the same process? I apologize if this is confusing - I am having some trouble wrapping my head around the bigger picture when it comes to modules altering kernel stack functionality. Thanks

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• Can anyone share a code snippet to Update Google Documents

  - by Sana

  Hi, I am relentlessly trying to update an existing google doc with the Google Protocol Data API, but the contents do not get updated, even though the PUT runs perfectly fine with a return response code of 200. Here is the code that I am using try { HttpRequest requestPost = transport.buildPutRequest(); requestPost.url = DocsUrl.forUploadingFile(editLink); ((GoogleHeaders) requestPost.headers).setSlugFromFileName("books1.xml"); InputStreamContent content = new InputStreamContent(); File file = new File("//sdcard/books.xml"); content.setFileInput(file); content.type = "text/plain"; content.length = file.length(); System.out.println("Length of the file = "+content.length); requestPost.content = content; HttpResponse responseUpload = requestPost.execute(); System.out.println("Uploading code = "+responseUpload.statusCode); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (ClientProtocolException e) { System.out.println("Client Protocol Exception"); } catch (IOException e) { handleException(e); } where editLink is the editLink edit-media link returned from google doc feeds.

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• SQL Server 2005 - Enabling both Named Pipes & TCP/IP protocols?

  - by Clinemi

  We have a SQL Server 2005 database, and currently all our users are connecting to the database via the TCP/IP protocol. The SQL Server Configuration Manager allows you to "enable" both Named Pipes, and TCP/IP connections at the same time. Is this a good idea? My question is not whether we should use named pipes instead of TCP/IP, but are there problems associated with enabling both? One of our client's IT guys, says that enabling database communication with both protocols will limit the bandwidth that either protocol can use - to like 50% of the total. I would think that the bandwidth that TCP/IP could use would be directly tied (inversely) to the amount of traffic that Named Pipes (or any of the other types of traffic) were occupying on the network at that moment. However, this IT person is indicating that the fact that we have enabled two protocols on the server, artificially limits the bandwidth that TCP/IP can use. Is this correct? I did Google searches but could not come up with an answer to this question. Any help would be appreciated.

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• Python: two loops at once

  - by Stephan Meijer

  I've got a problem: I am new to Python and I want to do multiple loops. I want to run a WebSocket client (Autobahn) and I want to run a loop which shows the filed which are edited in a specific folder (pyinotify or else Watchdog). Both are running forever, Great. Is there a way to run them at once and send a message via the WebSocket connection while I'm running the FileSystemWatcher, like with callbacks, multithreading, multiprocessing or just separate files? factory = WebSocketClientFactory("ws://localhost:8888/ws", debug=False) factory.protocol = self.webSocket connectWS(factory) reactor.run() If we run this, it will have success. But if we run this: factory = WebSocketClientFactory("ws://localhost:8888/ws", debug=False) factory.protocol = self.webSocket connectWS(factory) reactor.run() # Websocket client running now,running the filewatcher wm = pyinotify.WatchManager() mask = pyinotify.IN_DELETE | pyinotify.IN_CREATE # watched events class EventHandler(pyinotify.ProcessEvent): def process_IN_CREATE(self, event): print "Creating:", event.pathname def process_IN_DELETE(self, event): print "Removing:", event.pathname handler = EventHandler() notifier = pyinotify.Notifier(wm, handler) wdd = wm.add_watch('/tmp', mask, rec=True) notifier.loop() This will create 2 loops, but since we already have a loop, the code after 'reactor.run()' will not run at all.. For your information: this project is going to be a sync client. Thanks a lot!

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• delegate method throws runtime "unrecognized selector" error when switching back from one UIViewCont

  - by chimgrrl

  Ok, I've spend like half day on this and it's killing me. So I've got 3 view controllers transitioning from one another, something like this: I call the UploadDecisionViewController after destroying the previous View Controller: [self dismissModalViewControllerAnimated:YES]; [self performSelector:@selector(showUDModalView) withObject:nil afterDelay:0.5]; In my showUDModalView method: - (void)showUDModalView { UploadDecisionViewController *udcontroller = [[UploadDecisionViewController alloc] initWithNibName:@"UploadDecisionViewController" bundle:nil]; udcontroller.delegate = self; [self presentModalViewController:udcontroller animated:YES]; [udcontroller release]; } The UploadDecisionViewController shows up no problem. The UploadDecisionViewController has a button, which when clicked I want it to transition to the FileUploadViewController. I setup a UploadDecisionDelegate, threw a method in there to handle the button clicking: Inside UploadDecisionDelegate protocol (UploadDecisionViewController.h): @protocol UploadDecisionDelegate //let UOnliveViewController know that a button was selected - (void)UploadDecisionViewController:(UploadDecisionViewController *)controller madeChoice:(NSString *)whichDirection; @end Then inside my IBAction method when the button is clicked, I have this: - (IBAction)decisionSelected:(id)sender { [delegate UploadDecisionViewController:self madeChoice:@"upload"];//crashing at this line } When I run this, at this line above it is throwing a runtime exception: 2010-06-09 12:48:59.561 UOnlive[4735:207] *** -[UIView UploadDecisionViewController:madeChoice:]: unrecognized selector sent to instance 0x3b65420 2010-06-09 12:48:59.562 UOnlive[4735:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[UIView UploadDecisionViewController:madeChoice:]: unrecognized selector sent to instance 0x3b65420' 2010-06-09 12:48:59.563 UOnlive[4735:207] Stack: ( 33502299, 2495698185, 33884219, 33453686, 33306306, 20618, 2982917, 3390286, 3399023, 3394235, 3087839, 2996168, 3022945, 40156505, 33287040, 33283144, 40150549, 40150746, 3026863, 11700, 11554 ) Let me throw in the delegate method implemented also: - (void)UploadDecisionViewController:(UploadDecisionViewController *)controller madeChoice:(NSString *)whichDirection { NSLog(@"it got to here 245"); [self dismissModalViewControllerAnimated:YES]; if (yesOrNo) { //open up the FileUploadViewController and proceed to upload [self performSelector:@selector(showFUModalView) withObject:nil afterDelay:0.5]; } } Can someone tell me what the heck is going on? Thanks a bunch for the help...

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• Dynamically invoke web service at runtime

  - by Ulrik Rasmussen

  So, our application needs support for dynamically calling web services which are unknown at compile time. The user should therefore be able to specify a URL to a WSDL, and specify some data bindings for the request and reply parameters. When Googling for answers, it seems like the way to do this is by actually compiling a web service proxy class at runtime, loading it, and invoking the methods using reflection. I think this seems like a rather clunky approach, given that I don't really need a strongly typed set of classes when I'm going to cast my data dynamically anyway. Dynamically compiling code for doing something that simple also just seems like The Wrong Way To Do It. Restricting ourself to the SOAP protocol, is there any library for C# that implements this protocol for dynamic use? I can imagine that it would be possible to generate runtime key/value data structures from the WSDL, which could be used to specify the request messages, as well as reading the replies. The library should then be able to send well-formed SOAP messages to the server, and parse the replies, without the programmer having to generate the XML manually (at least not the headers and other plumbing). I can't seem to find any library that actually does this. Is what I want to do really that esoteric, or have I just searched the wrong places? Thanks, Ulrik

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• trouble setting up anonymous login in ejabberd

  - by sofia

  Hi, In ejabberd.cfg I have the following {host_config, "thisislove-MacBook-2.local", [{auth_method, [internal, anonymous]}, {allow_multiple_connections, false}, {anonymous_protocol, both}]}. but when using speeqe javascript client (speeqe.com) to connect, I see it sends <body rid='1366284187' xmlns='http://jabber.org/protocol/httpbind' to='thisislove-macbook-2.local' xml:lang='en' wait='60' hold='1' window='5' content='text/xml; charset=utf-8' ver='1.6' xmpp:version='1.0' xmlns:xmpp='urn:xmpp:xbosh'/> and the server responds with <body xmlns='http://jabber.org/protocol/httpbind' sid='f89bf034b02fa6b884bb0c55be3f1f69e45e3866' wait='60' requests='2' inactivity='30' maxpause='120' polling='2' ver='1.8' from='thisislove-macbook-2.local' secure='true' authid='353072658' xmlns:xmpp='urn:xmpp:xbosh' xmlns:stream='http://etherx.jabber.org/streams' xmpp:version='1.0'><stream:features xmlns:stream='http://etherx.jabber.org/streams'><mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'><mechanism>DIGEST-MD5</mechanism><mechanism>PLAIN</mechanism></mechanisms><register xmlns='http://jabber.org/features/iq-register'/></stream:features></body> Notice the mechanisms, DIGEST-MD5 & PLAIN. If I'm not mistaken it should have ANONYMOUS as a mechanism as well. So what happens is that speeqe simply terminates the connection. As such I'm thinking i must be missing something in the anonymous configuration or the muc config. In the mod_muc configg, I have {mod_muc, [ %%{host, "conference.@HOST@"}, {access, muc}, {access_create, muc}, {access_persistent, muc}, {access_admin, muc_admin}, {max_room_name, 190}, {max_room_desc, 190}, {max_users, 500} ]} So what am I missing? Thanks

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• NSNotification vs. Delegate Protocols?

  - by jr

  I have an iPhone application which basically is getting information from an API (in XML, but maybe JSON eventually). The result objects are typically displayed in view controllers (tables mainly). Here is the architecture right now. I have NSOperation classes which fetch the different objects from the remote server. Each of these NSOperation classes, will take a custom delegate method which will fire back the resulting objects as they are parsed, and then finally a method when no more results are available. So, the protocol for the delegates will be something like: (void) ObjectTypeResult:(ObjectType *)result; (void) ObjectTypeNoMoreResults; I think the solution works well, but I do end up with a bunch of delegate protocols around and then my view controllers have to implement all these delegate methods. I don't think its that bad, but I'm always on the lookout for a better design. So, I'm thinking about using NSNotifications to remove the use of the delegates. I could include the object in the userInfo part of the notification and just post objects as received, and then a final event when no more are available. Then I could just have one method in each view controller to receive all the data, even when using multiple objects in one controller.† So, can someone share with me some pros/cons of each approach. Should I consider refactoring my code to use Events rather then the delegates? Is one better then the other in certain situations? In my scenario I'm really not looking to receive notifications in multiple places, so maybe the protocol based delegates are the way to go. Thanks!

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• @selector and return value

  - by user320926

  The idea it's very easy, i have an http download class, this class must support the http authentication but it's basically a background thread so i would like to avoid to prompt directly to the screen, i would like to use a delegate method to require from outside of the class, like a viewController. But i don't know if is possible or if i have to use a different syntax. This class use this delegate protocol: //Updater.h @protocol Updater <NSObject> -(NSDictionary *)authRequired; @optional -(void)statusUpdate:(NSString *)newStatus; -(void)downloadProgress:(int)percentage; @end @interface Updater : NSThread { ... } This is the call to the delegate method: //Updater.m // This check always fails :( if ([self.delegate respondsToSelector:@selector(authRequired:)]) { auth = [delegate authRequired]; } This is the implementation of the delegate method //rootViewController.m -(NSDictionary *)authRequired; { // TODO: some kind of popup or modal view NSMutableDictionary *ret=[[NSMutableDictionary alloc] init]; [ret setObject:@"utente" forKey:@"user"]; [ret setObject:@"password" forKey:@"pass"]; return ret; }

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• Best practices for encrypting continuous/small UDP data

  - by temp

  Hello everyone, I am having an application where I have to send several small data per second through the network using UDP. The application need to send the data in real-time (no waiting). I want to encrypt these data and insure that what I am doing is as secure as possible. Since I am using UDP, there is no way to use SSL/TLS, so I have to encrypt each packet alone since the protocol is connectionless/unreliable/unregulated. Right now, I am using a 128-bit key derived from a passphrase from the user, and AES in CBC mode (PBE using AES-CBC). I decided to use a random salt with the passphrase to derive the 128-bit key (prevent dictionary attack on the passphrase), and of course use IVs (to prevent statistical analysis for packets). However I am concerned about few things: Each packet contains small amount of data (like a couple of integer values per packet) which will make the encrypted packets vulnerable to known-plaintext attacks (which will result in making it easier to crack the key). Also, since the encryption key is derived from a passphrase, this will make the key space way less (I know the salt will help, but I have to send the salt through the network once and anyone can get it). Given these two things, anyone can sniff and store the sent data, and try to crack the key. Although this process might take some time, once the key is cracked all the stored data will be decrypted, which will be a real problem for my application. So my question is, what is the best practices for sending/encrypting continuous small data using a connectionless protocol (UDP)? Is my way the best way to do it? ...flowed? ...Overkill? ... Please note that I am not asking for a 100% secure solution, as there is no such thing. Cheers

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• multiple clients - one server connection with sockets tcp/ip c# .net

  - by jagse

  Hello guys, I need to develop a client server system where I can have multiple clients communicating with one server at the same time. I want to communicate xml serialized objects and also need to send and receive other commands to invoke methods. Now, I am just starting with socket programming in C# and .Net and found that the asynchronous I/O is the way to go so that the methods dont block the execution of code. Also there are many examples of how to make a simple client server system. So I have a basic understanding of how that works. Anyway, what still is not clear to me is how I can set up a server which can manage connections to multiple clients? Can I just create a new socket per connection and then store those in some kind of list? Do I need some kind of multiplexing to achieve this? Do I have to listen at multiple ports? What`s the best way here? And the other thing is if I need to develop my own protocol to differentiate between what I am actually sending over the network -- xml serialized object or a command which might be just a string encoded in ascII or something. Or would I develop my own protocol just to send these commands? Any kind of help is apreciated! If someone knows a good book which covers this sort of stuff, let me know. Cheers I forgot to mention that some of my clients which are supposed to communicate with my server will be pda and I therefore use the compact framework... So this might bring in some restrictions...

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• Best practices for encrytping continuous/small UDP data

  - by temp

  Hello everyone, I am having an application where I have to send several small data per second through the network using UDP. The application need to send the data in real-time (on waiting). I want to encrypt these data and insure that what I am doing is as secure as possible. Since I am using UDP, there is no way to use SSL/TLS, so I have to encrypt each packet alone since the protocol is connectionless/unreliable/unregulated. Right now, I am using a 128-bit key derived from a passphrase from the user, and AES in CBC mode (PBE using AES-CBC). I decided to use a random salt with the passphrase to derive the 128-bit key (prevent dictionary attack on the passphrase), and of course use IVs (to prevent statistical analysis for packets). However I am concerned about few things: Each packet contains small amount of data (like a couple of integer values per packet) which will make the encrypted packets vulnerable to known-plaintext attacks (which will result in making it easier to crack the key). Also, since the encryption key is derived from a passphrase, this will make the key space way less (I know the salt will help, but I have to send the salt through the network once and anyone can get it). Given these two things, anyone can sniff and store the sent data, and try to crack the key. Although this process might take some time, once the key is cracked all the stored data will be decrypted, which will be a real problem for my application. So my question is, what is the best practices for sending/encrypting continuous small data using a connectionless protocol (UDP)? Is my way the best way to do it? ...flowed? ...Overkill? ... Please note that I am not asking for a 100% secure solution, as there is no such thing. Cheers

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• Are there any downsides in using C++ for network daemons?

  - by badcat

  Hey guys! I've been writing a number of network daemons in different languages over the past years, and now I'm about to start a new project which requires a new custom implementation of a properitary network protocol. The said protocol is pretty simple - some basic JSON formatted messages which are transmitted in some basic frame wrapping to have clients know that a message arrived completely and is ready to be parsed. The daemon will need to handle a number of connections (about 200 at the same time) and do some management of them and pass messages along, like in a chat room. In the past I've been using mostly C++ to write my daemons. Often with the Qt4 framework (the network parts, not the GUI parts!), because that's what I also used for the rest of the projects and it was simple to do and very portable. This usually worked just fine, and I didn't have much trouble. Being a Linux administrator for a good while now, I noticed that most of the network daemons in the wild are written in plain C (of course some are written in other languages, too, but I get the feeling that 80% of the daemons are written in plain C). Now I wonder why that is. Is this due to a pure historic UNIX background (like KISS) or for plain portability or reduction of bloat? What are the reasons to not use C++ or any "higher level" languages for things like daemons? Thanks in advance! Update 1: For me using C++ usually is more convenient because of the fact that I have objects which have getter and setter methods and such. Plain C's "context" objects can be a real pain at some point - especially when you are used to object oriented programming. Yes, I'm aware that C++ is a superset of C, and that C code is basically C++. But that's not the point. ;)

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• What is the best way to include Javascript?

  - by Paul Tarjan

  Many of the big players recommend slightly different techniques. Mostly on the placement of the new <script>. Google Anayltics: (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Facebook: (function() { var e = document.createElement('script'); e.async = true; e.src = document.location.protocol + '//connect.facebook.net/en_US/all.js'; document.getElementById('fb-root').appendChild(e); }());: Disqus: (function() { var dsq = document.createElement('script'); dsq.type = 'text/javascript'; dsq.async = true; dsq.src = 'http://' + disqus_shortname + '.disqus.com/embed.js'; (document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(dsq); })(); (post others and I'll add them) Is there any rhyme or reason for these choices or does it not matter at all?

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• Cocoa NSTextField Drag & Drop Requires Subclass... Really?

  - by ipmcc

  Until today, I've never had occasion to use anything other than an NSWindow itself as an NSDraggingDestination. When using a window as a one-size-fits-all drag destination, the NSWindow will pass those messages on to its delegate, allowing you to handle drops without subclassing NSWindow. The docs say: Although NSDraggingDestination is declared as an informal protocol, the NSWindow and NSView subclasses you create to adopt the protocol need only implement those methods that are pertinent. (The NSWindow and NSView classes provide private implementations for all of the methods.) Either a window object or its delegate may implement these methods; however, the delegate’s implementation takes precedence if there are implementations in both places. Today, I had a window with two NSTextFields on it, and I wanted them to have different drop behaviors, and I did not want to allow drops anywhere else in the window. The way I interpret the docs, it seems that I either have to subclass NSTextField, or make some giant spaghetti-conditional drop handlers on the window's delegate that hit-checks the draggingLocation against each view in order to select the different drop-area behaviors for each field. The centralized NSWindow-delegate-based drop handler approach seems like it would be onerous in any case where you had more than a small handful of drop destination views. Likewise, the subclassing approach seems onerous regardless of the case, because now the drop handling code lives in a view class, so once you accept the drop you've got to come up with some way to marshal the dropped data back to the model. The bindings docs warn you off of trying to drive bindings by setting the UI value programmatically. So now you're stuck working your way back around that too. So my question is: "Really!? Are those the only readily available options? Or am I missing something straightforward here?" Thanks.

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• How to Refresh / Reload a KML layer in OpenLayers. Dynamic KML Layer.

  - by Ozaki

  TLDR See my answer below on how to refresh the layer. So far I have tried action function as follows: function RefreshKMLData(layer) { layer.loaded = false; layer.setVisibility(true); layer.redraw({ force: true }); } set interval of the function: window.setInterval(RefreshKMLData, 5000, KMLLAYER); the layer itself: var KMLLAYER = new OpenLayers.Layer.Vector("MYKMLLAYER", { projection: new OpenLayers.Projection("EPSG:4326"), strategies: [new OpenLayers.Strategy.Fixed()], protocol: new OpenLayers.Protocol.HTTP({ url: MYKMLURL, format: new OpenLayers.Format.KML({ extractStyles: true, extractAttributes: true }) }) }); the url for KMLLAYER with Math random so it doesnt cache: var MYKMLURL = var currentanchorpositionurl = 'http://' + host + '/data?_salt=' + Math.random(); I would have thought that this would Refresh the layer. As by setting its loaded to false unloads it. Visibility to true reloads it and with the Math random shouldn't allow it to cache? So has anyone done this before or know how I can get this to work? TLDR See my answer below on how to refresh the layer.

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• How to understand the BODYSTRUCTURE information returned by IMAP servers?

  - by Tony

  I'm using python's IMAPClient to retrieve email messages from IMAP server. One of the attributes I retrieve is BODYSTRUCTURE. However, I can't find any documentation on how to interpret the return values. Here's the body structure that IMAP server returns 16:12.679978 < FLAGS (NotJunk $NotJunk \Seen) BODYSTRUCTURE ((("TEXT" "PLAIN" ("CHARSET" "us-ascii") NIL NIL "QUOTED-PRINTABLE" 4888 170 NIL NIL NIL)("TEXT" "HTML" ("CHARSET" "us-ascii") NIL NIL "QUOTED-PRINTABLE" 32407 479 NIL NIL NIL) "ALTERNATIVE" ("BOUNDARY" "Apple-Mail=_3AAA7CD7-3B07-406A-83CB-2C7762C3306E") NIL NIL)("APPLICATION" "PKCS7-SIGNATURE" ("NAME" "smime.p7s") NIL NIL "BASE64" 2414 NIL ("ATTACHMENT" ("FILENAME" "smime.p7s")) NIL) "SIGNED" ("BOUNDARY" "Apple-Mail=_DF4FE6BB-F796-46D7-A593-9723F4315DD2" "MICALG" "sha1" "PROTOCOL" "application/pkcs7-signature") NIL NIL)) Here's the same body structure parsed to python type. "BODYSTRUCTURE": [ [ [ [ "TEXT", "PLAIN", [ "CHARSET", "us-ascii" ], null, null, "QUOTED-PRINTABLE", 4888, 170, null, null, null ], [ "TEXT", "HTML", [ "CHARSET", "us-ascii" ], null, null, "QUOTED-PRINTABLE", 32407, 479, null, null, null ], "ALTERNATIVE", [ "BOUNDARY", "Apple-Mail=_3AAA7CD7-3B07-406A-83CB-2C7762C3306E" ], null, null ], [ "APPLICATION", "PKCS7-SIGNATURE", [ "NAME", "smime.p7s" ], null, null, "BASE64", 2414, null, [ "ATTACHMENT", [ "FILENAME", "smime.p7s" ] ], null ] ], "SIGNED", [ "BOUNDARY", "Apple-Mail=_DF4FE6BB-F796-46D7-A593-9723F4315DD2", "MICALG", "sha1", "PROTOCOL", "application/pkcs7-signature" ], null, null ], The arrays don't seems to be constant length. What each element of the array stand for?

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• two view controllers and reusability with delegate

  - by netcharmer

  Newbie question about design patterns in objC. I'm writing a functionality for my iphone app which I plan to use in other apps too. The functionality is written over two classes - Viewcontroller1 and Viewcontroller2. Viewcontroller1 is the root view of a navigation controller and it can push Viewcontroller2. Rest of the app will use only ViewController1 and will never access Viewcontroller2 directly. However, triggered by user events, Viewcontroller2 has to send a message to the rest of the app. My question is what is the best way of achieving it? Currently, I use two level of delegation to send the message out from Viewcontroller2. First send it to Viewcontroller1 and then let Viewcontroller1 send it to rest of the app or the application delegate. So my code looks like - //Viewcontroller1.h @protocol bellDelegate -(int)bellRang:(int)size; @end @interface Viewcontroller1 : UITableViewController <dummydelegate> { id <bellDelegate> delegate; @end //Viewcontroller1.m @implementation Viewcontroller1 -(void)viewDidLoad { //some stuff here Viewcontroller2 *vc2 = [[Viewcontroller2 alloc] init]; vc2.delegate = self; [self.navigationController pushViewController:vc2 animated:YES]; } -(int)dummyBell:(int)size { return([self.delegate bellRang:size]); } //Viewcontroller2.h @protocol dummyDelegate -(int)dummyBell:(int)size; @end @interface Viewcontroller2 : UITableViewController { id <dummyDelegate> delegate; @end //Viewcontroller2.m @implementation Viewcontroller2 -(int)eventFoo:(int)size { rval = [self.delegate dummyBell:size]; } @end

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• The SSIS tuning tip that everyone misses

  - by Rob Farley

  I know that everyone misses this, because I’m yet to find someone who doesn’t have a bit of an epiphany when I describe this. When tuning Data Flows in SQL Server Integration Services, people see the Data Flow as moving from the Source to the Destination, passing through a number of transformations. What people don’t consider is the Source, getting the data out of a database. Remember, the source of data for your Data Flow is not your Source Component. It’s wherever the data is, within your database, probably on a disk somewhere. You need to tune your query to optimise it for SSIS, and this is what most people fail to do. I’m not suggesting that people don’t tune their queries – there’s plenty of information out there about making sure that your queries run as fast as possible. But for SSIS, it’s not about how fast your query runs. Let me say that again, but in bolder text: The speed of an SSIS Source is not about how fast your query runs. If your query is used in a Source component for SSIS, the thing that matters is how fast it starts returning data. In particular, those first 10,000 rows to populate that first buffer, ready to pass down the rest of the transformations on its way to the Destination. Let’s look at a very simple query as an example, using the AdventureWorks database: We’re picking the different Weight values out of the Product table, and it’s doing this by scanning the table and doing a Sort. It’s a Distinct Sort, which means that the duplicates are discarded. It'll be no surprise to see that the data produced is sorted. Obvious, I know, but I'm making a comparison to what I'll do later. Before I explain the problem here, let me jump back into the SSIS world... If you’ve investigated how to tune an SSIS flow, then you’ll know that some SSIS Data Flow Transformations are known to be Blocking, some are Partially Blocking, and some are simply Row transformations. Take the SSIS Sort transformation, for example. I’m using a larger data set for this, because my small list of Weights won’t demonstrate it well enough. Seven buffers of data came out of the source, but none of them could be pushed past the Sort operator, just in case the last buffer contained the data that would be sorted into the first buffer. This is a blocking operation. Back in the land of T-SQL, we consider our Distinct Sort operator. It’s also blocking. It won’t let data through until it’s seen all of it. If you weren’t okay with blocking operations in SSIS, why would you be happy with them in an execution plan? The source of your data is not your OLE DB Source. Remember this. The source of your data is the NCIX/CIX/Heap from which it’s being pulled. Picture it like this... the data flowing from the Clustered Index, through the Distinct Sort operator, into the SELECT operator, where a series of SSIS Buffers are populated, flowing (as they get full) down through the SSIS transformations. Alright, I know that I’m taking some liberties here, because the two queries aren’t the same, but consider the visual. The data is flowing from your disk and through your execution plan before it reaches SSIS, so you could easily find that a blocking operation in your plan is just as painful as a blocking operation in your SSIS Data Flow. Luckily, T-SQL gives us a brilliant query hint to help avoid this. OPTION (FAST 10000) This hint means that it will choose a query which will optimise for the first 10,000 rows – the default SSIS buffer size. And the effect can be quite significant. First let’s consider a simple example, then we’ll look at a larger one. Consider our weights. We don’t have 10,000, so I’m going to use OPTION (FAST 1) instead. You’ll notice that the query is more expensive, using a Flow Distinct operator instead of the Distinct Sort. This operator is consuming 84% of the query, instead of the 59% we saw from the Distinct Sort. But the first row could be returned quicker – a Flow Distinct operator is non-blocking. The data here isn’t sorted, of course. It’s in the same order that it came out of the index, just with duplicates removed. As soon as a Flow Distinct sees a value that it hasn’t come across before, it pushes it out to the operator on its left. It still has to maintain the list of what it’s seen so far, but by handling it one row at a time, it can push rows through quicker. Overall, it’s a lot more work than the Distinct Sort, but if the priority is the first few rows, then perhaps that’s exactly what we want. The Query Optimizer seems to do this by optimising the query as if there were only one row coming through: This 1 row estimation is caused by the Query Optimizer imagining the SELECT operation saying “Give me one row” first, and this message being passed all the way along. The request might not make it all the way back to the source, but in my simple example, it does. I hope this simple example has helped you understand the significance of the blocking operator. Now I’m going to show you an example on a much larger data set. This data was fetching about 780,000 rows, and these are the Estimated Plans. The data needed to be Sorted, to support further SSIS operations that needed that. First, without the hint. ...and now with OPTION (FAST 10000): A very different plan, I’m sure you’ll agree. In case you’re curious, those arrows in the top one are 780,000 rows in size. In the second, they’re estimated to be 10,000, although the Actual figures end up being 780,000. The top one definitely runs faster. It finished several times faster than the second one. With the amount of data being considered, these numbers were in minutes. Look at the second one – it’s doing Nested Loops, across 780,000 rows! That’s not generally recommended at all. That’s “Go and make yourself a coffee” time. In this case, it was about six or seven minutes. The faster one finished in about a minute. But in SSIS-land, things are different. The particular data flow that was consuming this data was significant. It was being pumped into a Script Component to process each row based on previous rows, creating about a dozen different flows. The data flow would take roughly ten minutes to run – ten minutes from when the data first appeared. The query that completes faster – chosen by the Query Optimizer with no hints, based on accurate statistics (rather than pretending the numbers are smaller) – would take a minute to start getting the data into SSIS, at which point the ten-minute flow would start, taking eleven minutes to complete. The query that took longer – chosen by the Query Optimizer pretending it only wanted the first 10,000 rows – would take only ten seconds to fill the first buffer. Despite the fact that it might have taken the database another six or seven minutes to get the data out, SSIS didn’t care. Every time it wanted the next buffer of data, it was already available, and the whole process finished in about ten minutes and ten seconds. When debugging SSIS, you run the package, and sit there waiting to see the Debug information start appearing. You look for the numbers on the data flow, and seeing operators going Yellow and Green. Without the hint, I’d sit there for a minute. With the hint, just ten seconds. You can imagine which one I preferred. By adding this hint, it felt like a magic wand had been waved across the query, to make it run several times faster. It wasn’t the case at all – but it felt like it to SSIS.

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• Consuming the Amazon S3 service from a Win8 Metro Application

  - by cibrax

  As many of the existing Http APIs for Cloud Services, AWS also provides a set of different platform SDKs for hiding many of complexities present in the APIs. While there is a platform SDK for .NET, which is open source and available in C#, that SDK does not work in Win8 Metro Applications for the changes introduced in WinRT. WinRT offers a complete different set of APIs for doing I/O operations such as doing http calls or using cryptography for signing or encrypting data, two aspects that are absolutely necessary for consuming AWS. All the I/O APIs available as part of WinRT are asynchronous, and uses the TPL model for .NET applications (HTML and JavaScript Metro applications use a model based in promises, which is similar concept).  In the case of S3, the http Authorization header is used for two purposes, authenticating clients and make sure the messages were not altered while they were in transit. For doing that, it uses a signature or hash of the message content and some of the headers using a symmetric key (That's just one of the available mechanisms). Windows Azure for example also uses the same mechanism in many of its APIs. There are three challenges that any developer working for first time in Metro will have to face to consume S3, the new WinRT APIs, the asynchronous nature of them and the complexity introduced for generating the Authorization header. Having said that, I decided to write this post with some of the gotchas I found myself trying to consume this Amazon service. 1. Generating the signature for the Authorization header All the cryptography APIs in WinRT are available under Windows.Security.Cryptography namespace. Many of operations available in these APIs uses the concept of buffers (IBuffer) for representing a chunk of binary data. As you will see in the example below, these buffers are mainly generated with the use of static methods in a WinRT class CryptographicBuffer available as part of the namespace previously mentioned. private string DeriveAuthToken(string resource, string httpMethod, string timestamp) { var stringToSign = string.Format("{0}\n" + "\n" + "\n" + "\n" + "x-amz-date:{1}\n" + "/{2}/", httpMethod, timestamp, resource); var algorithm = MacAlgorithmProvider.OpenAlgorithm("HMAC_SHA1"); var keyMaterial = CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(this.secret)); var hmacKey = algorithm.CreateKey(keyMaterial); var signature = CryptographicEngine.Sign( hmacKey, CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(stringToSign)) ); return CryptographicBuffer.EncodeToBase64String(signature); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The algorithm that determines the information or content you need to use for generating the signature is very well described as part of the AWS documentation. In this case, this method is generating a signature required for creating a new bucket. A HmacSha1 hash is computed using a secret or symetric key provided by AWS in the management console. 2. Sending an Http Request to the S3 service WinRT also ships with the System.Net.Http.HttpClient that was first introduced some months ago with ASP.NET Web API. This client provides a rich interface on top the traditional WebHttpRequest class, and also solves some of limitations found in this last one. There are a few things that don't work with a raw WebHttpRequest such as setting the Host header, which is something absolutely required for consuming S3. Also, HttpClient is more friendly for doing unit tests, as it receives a HttpMessageHandler as part of the constructor that can fake to emulate a real http call. This is how the code for consuming the service with HttpClient looks like, public async Task<S3Response> CreateBucket(string name, string region = null, params string[] acl) { var timestamp = string.Format("{0:r}", DateTime.UtcNow); var auth = DeriveAuthToken(name, "PUT", timestamp); var request = new HttpRequestMessage(HttpMethod.Put, "http://s3.amazonaws.com/"); request.Headers.Host = string.Format("{0}.s3.amazonaws.com", name); request.Headers.TryAddWithoutValidation("Authorization", "AWS " + this.key + ":" + auth); request.Headers.Add("x-amz-date", timestamp); var client = new HttpClient(); var response = await client.SendAsync(request); return new S3Response { Succeed = response.StatusCode == HttpStatusCode.OK, Message = (response.Content != null) ? await response.Content.ReadAsStringAsync() : null }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You will notice a few additional things in this code. By default, HttpClient validates the values for some well-know headers, and Authorization is one of them. It won't allow you to set a value with ":" on it, which is something that S3 expects. However, that's not a problem at all, as you can skip the validation by using the TryAddWithoutValidation method. Also, the code is heavily relying on the new async and await keywords to transform all the asynchronous calls into synchronous ones. In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, public class FakeHttpMessageHandler : HttpMessageHandler { HttpResponseMessage response; public FakeHttpMessageHandler(HttpResponseMessage response) { this.response = response; } protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) { var tcs = new TaskCompletionSource<HttpResponseMessage>(); tcs.SetResult(response); return tcs.Task; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You can use this handler for injecting any response while you are unit testing the code.

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• Consuming the Amazon S3 service from a Win8 Metro Application

  - by cibrax

  As many of the existing Http APIs for Cloud Services, AWS also provides a set of different platform SDKs for hiding many of complexities present in the APIs. While there is a platform SDK for .NET, which is open source and available in C#, that SDK does not work in Win8 Metro Applications for the changes introduced in WinRT. WinRT offers a complete different set of APIs for doing I/O operations such as doing http calls or using cryptography for signing or encrypting data, two aspects that are absolutely necessary for consuming AWS. All the I/O APIs available as part of WinRT are asynchronous, and uses the TPL model for .NET applications (HTML and JavaScript Metro applications use a model based in promises, which is similar concept).  In the case of S3, the http Authorization header is used for two purposes, authenticating clients and make sure the messages were not altered while they were in transit. For doing that, it uses a signature or hash of the message content and some of the headers using a symmetric key (That's just one of the available mechanisms). Windows Azure for example also uses the same mechanism in many of its APIs. There are three challenges that any developer working for first time in Metro will have to face to consume S3, the new WinRT APIs, the asynchronous nature of them and the complexity introduced for generating the Authorization header. Having said that, I decided to write this post with some of the gotchas I found myself trying to consume this Amazon service. 1. Generating the signature for the Authorization header All the cryptography APIs in WinRT are available under Windows.Security.Cryptography namespace. Many of operations available in these APIs uses the concept of buffers (IBuffer) for representing a chunk of binary data. As you will see in the example below, these buffers are mainly generated with the use of static methods in a WinRT class CryptographicBuffer available as part of the namespace previously mentioned. private string DeriveAuthToken(string resource, string httpMethod, string timestamp) { var stringToSign = string.Format("{0}\n" + "\n" + "\n" + "\n" + "x-amz-date:{1}\n" + "/{2}/", httpMethod, timestamp, resource); var algorithm = MacAlgorithmProvider.OpenAlgorithm("HMAC_SHA1"); var keyMaterial = CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(this.secret)); var hmacKey = algorithm.CreateKey(keyMaterial); var signature = CryptographicEngine.Sign( hmacKey, CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(stringToSign)) ); return CryptographicBuffer.EncodeToBase64String(signature); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The algorithm that determines the information or content you need to use for generating the signature is very well described as part of the AWS documentation. In this case, this method is generating a signature required for creating a new bucket. A HmacSha1 hash is computed using a secret or symetric key provided by AWS in the management console. 2. Sending an Http Request to the S3 service WinRT also ships with the System.Net.Http.HttpClient that was first introduced some months ago with ASP.NET Web API. This client provides a rich interface on top the traditional WebHttpRequest class, and also solves some of limitations found in this last one. There are a few things that don't work with a raw WebHttpRequest such as setting the Host header, which is something absolutely required for consuming S3. Also, HttpClient is more friendly for doing unit tests, as it receives a HttpMessageHandler as part of the constructor that can fake to emulate a real http call. This is how the code for consuming the service with HttpClient looks like, public async Task<S3Response> CreateBucket(string name, string region = null, params string[] acl) { var timestamp = string.Format("{0:r}", DateTime.UtcNow); var auth = DeriveAuthToken(name, "PUT", timestamp); var request = new HttpRequestMessage(HttpMethod.Put, "http://s3.amazonaws.com/"); request.Headers.Host = string.Format("{0}.s3.amazonaws.com", name); request.Headers.TryAddWithoutValidation("Authorization", "AWS " + this.key + ":" + auth); request.Headers.Add("x-amz-date", timestamp); var client = new HttpClient(); var response = await client.SendAsync(request); return new S3Response { Succeed = response.StatusCode == HttpStatusCode.OK, Message = (response.Content != null) ? await response.Content.ReadAsStringAsync() : null }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You will notice a few additional things in this code. By default, HttpClient validates the values for some well-know headers, and Authorization is one of them. It won't allow you to set a value with ":" on it, which is something that S3 expects. However, that's not a problem at all, as you can skip the validation by using the TryAddWithoutValidation method. Also, the code is heavily relying on the new async and await keywords to transform all the asynchronous calls into synchronous ones. In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, public class FakeHttpMessageHandler : HttpMessageHandler { HttpResponseMessage response; public FakeHttpMessageHandler(HttpResponseMessage response) { this.response = response; } protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) { var tcs = new TaskCompletionSource<HttpResponseMessage>(); tcs.SetResult(response); return tcs.Task; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You can use this handler for injecting any response while you are unit testing the code.

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• ???Flashback Log???????Redo Log?

  - by Liu Maclean(???)

  ????????????????????redo log?   RVWR( Recovery Writer)?3s??flashback generate buffer??block before image?????????? ?????block change???RVWR??block before image ?flashback log? ?????????,Oracle???????????before image????????,????????flashback database logs?????   ???????????,????? ??????????????????,???????????before image?????shared pool??flashback log buffer?,RVWR??????flashback log buffer??????????? ?DBWR???????????????,DBWR?????buffer header??FBA(Flashback Byte Address)?flashback log buffer?????????? ???? ?????? ??? ????????????? , RVWR???????????(flashback markers)?flashback database logs?? ????(flashback markers)?????????????Oracle??flashback ??????????  ??????????, Oracle ??????(flashback markers)????????????flashback database log???????????block image; ??Oracle ???????(forward recovery)?????????????????SCN?????? flashback markers for example: **** Record at fba: (lno 1 thr 1 seq 1 bno 4 bof 8184) **** RECORD HEADER: Type: 3 (Skip) Size: 8132 RECORD DATA (Skip): **** Record at fba: (lno 1 thr 1 seq 1 bno 4 bof 52) **** RECORD HEADER: Type: 7 (Begin Crash Recovery Record) Size: 36 RECORD DATA (Begin Crash Recovery Record): Previous logical record fba: (lno 1 thr 1 seq 1 bno 3 bof 316) Record scn: 0x0000.00000000 [0.0] **** Record at fba: (lno 1 thr 1 seq 1 bno 3 bof 8184) **** RECORD HEADER: Type: 3 (Skip) Size: 7868 RECORD DATA (Skip): **** Record at fba: (lno 1 thr 1 seq 1 bno 3 bof 316) **** RECORD HEADER: Type: 2 (Marker) Size: 300 RECORD DATA (Marker): Previous logical record fba: (lno 0 thr 0 seq 0 bno 0 bof 0) Record scn: 0x0000.00000000 [0.0] Marker scn: 0x0000.0060e024 [0.6348836] 06/13/2012 15:56:35 Flag 0x0 Flashback threads: 1, Enabled redo threads 1 Recovery Start Checkpoint: scn: 0x0000.0060e024 [0.6348836] 06/13/2012 15:56:12 thread:1 rba:(0x80.180.10) Flashback thread Markers: Thread:1 status:0 fba: (lno 1 thr 1 seq 1 bno 2 bof 8184) Redo Thread Checkpoint Info: Thread:1 rba:(0x80.180.10) **** Record at fba: (lno 1 thr 1 seq 1 bno 2 bof 8184) **** RECORD HEADER: Type: 3 (Skip) Size: 8168 RECORD DATA (Skip): End-Of-Thread reached ????????????????block change ????before image????????flashback log?? ?????block change???flashback log record ????????? redo log???!????flashback log ???????before image ? redo log??? change vector ?  Oracle?????????????????????????????????????,??????I/O??????????????: ??hot block??,Oracle???????????block image?????; Oracle ?????????(flashback barriers)???????????????,flashback barriers???????(???15??),??????????(flashback barriers)????(flashback markers)????????? ????, ??????change?????, ???????????????????????????, ?15????????????????????flashback log????????before image?????????????,?????????????????????,?????????????? ????????,??????????????(flashback barriers), flashback barriers???????,?????15????? ?????flashback barriers????????(flashback markers)???????????????,???????????????????(????barriers?????)??????block image ,????????????????????????????????? ??????????flashback log????redo log????! ????,????????????????, ?????????? SQL> select * from v$version; BANNER -------------------------------------------------------------------------------- Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production PL/SQL Release 11.2.0.3.0 - Production CORE 11.2.0.3.0 Production TNS for Linux: Version 11.2.0.3.0 - Production NLSRTL Version 11.2.0.3.0 - Production SQL> select * from global_name; GLOBAL_NAME -------------------------------------------------------------------------------- www.oracledatabase12g.com SQL> create table flash_maclean (t1 varchar2(200)) tablespace users; Table created. SQL> insert into flash_maclean values('MACLEAN LOVE HANNA'); 1 row created. SQL> commit; Commit complete. SQL> startup force; ORACLE instance started. Total System Global Area 939495424 bytes Fixed Size 2233960 bytes Variable Size 713034136 bytes Database Buffers 218103808 bytes Redo Buffers 6123520 bytes Database mounted. Database opened. SQL> update flash_maclean set t1='HANNA LOVE MACLEAN'; 1 row updated. commit; Commit complete. SQL> alter system checkpoint; System altered. SQL> select dbms_rowid.rowid_block_number(rowid),dbms_rowid.rowid_relative_fno(rowid) from flash_maclean; DBMS_ROWID.ROWID_BLOCK_NUMBER(ROWID) DBMS_ROWID.ROWID_RELATIVE_FNO(ROWID) ------------------------------------ ------------------------------------ 140431 4 datafile 4 block 140431 ??RDBA rdba: 0x0102248f (4/140431) SQL> ! ps -ef|grep rvwr|grep -v grep oracle 26695 1 0 15:56 ? 00:00:00 ora_rvwr_G11R23 SQL> oradebug setospid 26695 Oracle pid: 20, Unix process pid: 26695, image: [email protected] (RVWR) SQL> ORADEBUG DUMP FBTAIL 1; Statement processed. To dump the last 2000 flashback records , ??ORADEBUG DUMP FBTAIL 1????????2000?????? SQL> oradebug tracefile_name /s01/orabase/diag/rdbms/g11r23/G11R23/trace/G11R23_rvwr_26695.trc ? TRACE?????????block? before image **** Record at fba: (lno 1 thr 1 seq 1 bno 55 bof 2564) **** RECORD HEADER: Type: 1 (Block Image) Size: 28 RECORD DATA (Block Image): file#: 4 rdba: 0x0102248f Next scn: 0x0000.00000000 [0.0] Flag: 0x0 Block Size: 8192 BLOCK IMAGE: buffer rdba: 0x0102248f scn: 0x0000.00609044 seq: 0x01 flg: 0x06 tail: 0x90440601 frmt: 0x02 chkval: 0xc626 type: 0x06=trans data Hex dump of block: st=0, typ_found=1 Dump of memory from 0x00002B1D94183C00 to 0x00002B1D94185C00 2B1D94183C00 0000A206 0102248F 00609044 06010000 [.....$..D.`.....] 2B1D94183C10 0000C626 00000001 00014AD4 0060903A [&........J..:.`.] 2B1D94183C20 00000000 00320002 01022488 00090006 [......2..$......] 2B1D94183C30 00000CC8 00C00340 000D0542 00008000 [[email protected].......] 2B1D94183C40 006040BC 000F000A 00000920 00C002E4 [.@`..... .......] 2B1D94183C50 0017048F 00002001 00609044 00000000 [..... ..D.`.....] 2B1D94183C60 00000000 00010100 0014FFFF 1F6E1F77 [............w.n.] 2B1D94183C70 00001F6E 1F770001 00000000 00000000 [n.....w.........] 2B1D94183C80 00000000 00000000 00000000 00000000 [................] Repeat 500 times 2B1D94185BD0 00000000 00000000 2C000000 4D120102 [...........,...M] 2B1D94185BE0 454C4341 4C204E41 2045564F 4E4E4148 [ACLEAN LOVE HANN] 2B1D94185BF0 01002C41 43414D07 4E41454C 90440601 [A,...MACLEAN..D.] Block header dump: 0x0102248f Object id on Block? Y seg/obj: 0x14ad4 csc: 0x00.60903a itc: 2 flg: E typ: 1 - DATA brn: 0 bdba: 0x1022488 ver: 0x01 opc: 0 inc: 0 exflg: 0 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x0006.009.00000cc8 0x00c00340.0542.0d C--- 0 scn 0x0000.006040bc 0x02 0x000a.00f.00000920 0x00c002e4.048f.17 --U- 1 fsc 0x0000.00609044 bdba: 0x0102248f data_block_dump,data header at 0x2b1d94183c64 =============== tsiz: 0x1f98 hsiz: 0x14 pbl: 0x2b1d94183c64 76543210 flag=-------- ntab=1 nrow=1 frre=-1 fsbo=0x14 fseo=0x1f77 avsp=0x1f6e tosp=0x1f6e 0xe:pti[0] nrow=1 offs=0 0x12:pri[0] offs=0x1f77 block_row_dump: tab 0, row 0, @0x1f77 tl: 22 fb: --H-FL-- lb: 0x2 cc: 1 col 0: [18] 4d 41 43 4c 45 41 4e 20 4c 4f 56 45 20 48 41 4e 4e 41 end_of_block_dump SQL> select dump('MACLEAN LOVE HANNA',16) from dual; DUMP('MACLEANLOVEHANNA',16) -------------------------------------------------------------------- Typ=96 Len=18: 4d,41,43,4c,45,41,4e,20,4c,4f,56,45,20,48,41,4e,4e,41 ???????????????????????,??flashback log??before image????????? create table flash_maclean1 (t1 int) tablespace users; SQL> select vs.name, ms.value 2 from v$mystat ms, v$sysstat vs 3 where vs.statistic# = ms.statistic# 4 and vs.name in ('redo size','db block changes'); NAME VALUE ---------------------------------------------------------------- ---------- db block changes 0 redo size 0 SQL> select name,value from v$sysstat where name like 'flashback log%'; NAME VALUE ---------------------------------------------------------------- ---------- flashback log writes 49 flashback log write bytes 9306112 SQL> begin 2 for i in 1..5000 loop 3 update flash_maclean1 set t1=t1+1; 4 commit; 5 end loop; 6 end; 7 / PL/SQL procedure successfully completed. SQL> select vs.name, ms.value 2 from v$mystat ms, v$sysstat vs 3 where vs.statistic# = ms.statistic# 4 and vs.name in ('redo size','db block changes'); NAME VALUE ---------------------------------------------------------------- ---------- db block changes 20006 redo size 3071288 SQL> select name,value from v$sysstat where name like 'flashback log%'; NAME VALUE ---------------------------------------------------------------- ---------- flashback log writes 52 flashback log write bytes 10338304 ??????????? ??hot block,???20006 ?block changes???? ??? 3000k ?redo log ? ??1000k? flashback log ?

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