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• Does anyone have database, programming language/framework suggestions for a GUI point of sale system

  - by Jason Down

  Our company has a point of sale system with many extras, such as ordering and receiving functionality, sales and order history etc. Our main issue is that the system was not designed properly from the ground up, so it takes too long to make fixes and handle requests from our customers. Also, the current technology we are using (Progress database, Progress 4GL for the language) incurs quite a bit of licensing expenses on our customers due to mutli-user license fees for database connections etc. After a lot of discussion it is looking like we will probably start over from scratch (while maintaining the current product at least for the time being). We are looking for a couple of things: Create the system with a nice GUI front end (it is currently CHUI and the application was not built in a way that allows us to redesign the front end... no layering or separation of business logic and gui...shudder). Create the system with the ability to modularize different functionality so the product doesn't have to include all features. This would keep the cost down for our current customers that want basic functionality and a lower price tag. The bells and whistles would be available for those that would want them. Use proper design patterns to make the product easy to add or change any part at any time (i.e. change the database or change the front end without needing to rewrite the application or most of it). This is a problem today because the Progress 4GL code is directly compiled against the database. Small changes in the database requires lots of code recompiling. Our new system will be Linux based, with a possibility of a client application providing functionality from one or more windows boxes. So what I'm looking for is any suggestions on which database and/or framework or programming language(s) someone might recommend for this sort of product. Anyone that has experience in this field might be able to point us in the right direction or even have some ideas of what to avoid. We have considered .NET and SQL Express (we don't need an enterprise level DB), but that would limit us to windows (as far as I know anyway). I have heard of Mono for writing .NET code in a Linux environment, but I don't know much about it yet. We've also considered a Java and MySql based implementation. To summarize we are looking to do the following: Keep licensing costs down on the technology we will use to develop the product (Oracle, yikes! MySQL, nice.) Deliver a solution that is easily maintainable and supportable. A solution that has a component capable of running on "old" hardware through a CHUI front end. (some of our customers have 40+ terminals which would be a ton of cash in order to convert over to a PC). Suggestions would be appreciated. Thanks [UPDATE] I should note that we are currently performing a total cost analysis. This question is intended to give us a couple of "educated" options to look into to include in or analysis. Anyone who could share experiences/suggestions about client/server setups would be appreciated (not just those who have experience with point of sale systems... that would just be a bonus).

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• Python: Improving long cumulative sum

  - by Bo102010

  I have a program that operates on a large set of experimental data. The data is stored as a list of objects that are instances of a class with the following attributes: time_point - the time of the sample cluster - the name of the cluster of nodes from which the sample was taken code - the name of the node from which the sample was taken qty1 = the value of the sample for the first quantity qty2 = the value of the sample for the second quantity I need to derive some values from the data set, grouped in three ways - once for the sample as a whole, once for each cluster of nodes, and once for each node. The values I need to derive depend on the (time sorted) cumulative sums of qty1 and qty2: the maximum value of the element-wise sum of the cumulative sums of qty1 and qty2, the time point at which that maximum value occurred, and the values of qty1 and qty2 at that time point. I came up with the following solution: dataset.sort(key=operator.attrgetter('time_point')) # For the whole set sys_qty1 = 0 sys_qty2 = 0 sys_combo = 0 sys_max = 0 # For the cluster grouping cluster_qty1 = defaultdict(int) cluster_qty2 = defaultdict(int) cluster_combo = defaultdict(int) cluster_max = defaultdict(int) cluster_peak = defaultdict(int) # For the node grouping node_qty1 = defaultdict(int) node_qty2 = defaultdict(int) node_combo = defaultdict(int) node_max = defaultdict(int) node_peak = defaultdict(int) for t in dataset: # For the whole system ###################################################### sys_qty1 += t.qty1 sys_qty2 += t.qty2 sys_combo = sys_qty1 + sys_qty2 if sys_combo > sys_max: sys_max = sys_combo # The Peak class is to record the time point and the cumulative quantities system_peak = Peak(time_point=t.time_point, qty1=sys_qty1, qty2=sys_qty2) # For the cluster grouping ################################################## cluster_qty1[t.cluster] += t.qty1 cluster_qty2[t.cluster] += t.qty2 cluster_combo[t.cluster] = cluster_qty1[t.cluster] + cluster_qty2[t.cluster] if cluster_combo[t.cluster] > cluster_max[t.cluster]: cluster_max[t.cluster] = cluster_combo[t.cluster] cluster_peak[t.cluster] = Peak(time_point=t.time_point, qty1=cluster_qty1[t.cluster], qty2=cluster_qty2[t.cluster]) # For the node grouping ##################################################### node_qty1[t.node] += t.qty1 node_qty2[t.node] += t.qty2 node_combo[t.node] = node_qty1[t.node] + node_qty2[t.node] if node_combo[t.node] > node_max[t.node]: node_max[t.node] = node_combo[t.node] node_peak[t.node] = Peak(time_point=t.time_point, qty1=node_qty1[t.node], qty2=node_qty2[t.node]) This produces the correct output, but I'm wondering if it can be made more readable/Pythonic, and/or faster/more scalable. The above is attractive in that it only loops through the (large) dataset once, but unattractive in that I've essentially copied/pasted three copies of the same algorithm. To avoid the copy/paste issues of the above, I tried this also: def find_peaks(level, dataset): def grouping(object, attr_name): if attr_name == 'system': return attr_name else: return object.__dict__[attrname] cuml_qty1 = defaultdict(int) cuml_qty2 = defaultdict(int) cuml_combo = defaultdict(int) level_max = defaultdict(int) level_peak = defaultdict(int) for t in dataset: cuml_qty1[grouping(t, level)] += t.qty1 cuml_qty2[grouping(t, level)] += t.qty2 cuml_combo[grouping(t, level)] = (cuml_qty1[grouping(t, level)] + cuml_qty2[grouping(t, level)]) if cuml_combo[grouping(t, level)] > level_max[grouping(t, level)]: level_max[grouping(t, level)] = cuml_combo[grouping(t, level)] level_peak[grouping(t, level)] = Peak(time_point=t.time_point, qty1=node_qty1[grouping(t, level)], qty2=node_qty2[grouping(t, level)]) return level_peak system_peak = find_peaks('system', dataset) cluster_peak = find_peaks('cluster', dataset) node_peak = find_peaks('node', dataset) For the (non-grouped) system-level calculations, I also came up with this, which is pretty: dataset.sort(key=operator.attrgetter('time_point')) def cuml_sum(seq): rseq = [] t = 0 for i in seq: t += i rseq.append(t) return rseq time_get = operator.attrgetter('time_point') q1_get = operator.attrgetter('qty1') q2_get = operator.attrgetter('qty2') timeline = [time_get(t) for t in dataset] cuml_qty1 = cuml_sum([q1_get(t) for t in dataset]) cuml_qty2 = cuml_sum([q2_get(t) for t in dataset]) cuml_combo = [q1 + q2 for q1, q2 in zip(cuml_qty1, cuml_qty2)] combo_max = max(cuml_combo) time_max = timeline.index(combo_max) q1_at_max = cuml_qty1.index(time_max) q2_at_max = cuml_qty2.index(time_max) However, despite this version's cool use of list comprehensions and zip(), it loops through the dataset three times just for the system-level calculations, and I can't think of a good way to do the cluster-level and node-level calaculations without doing something slow like: timeline = defaultdict(int) cuml_qty1 = defaultdict(int) #...etc. for c in cluster_list: timeline[c] = [time_get(t) for t in dataset if t.cluster == c] cuml_qty1[c] = [q1_get(t) for t in dataset if t.cluster == c] #...etc. Does anyone here at Stack Overflow have suggestions for improvements? The first snippet above runs well for my initial dataset (on the order of a million records), but later datasets will have more records and clusters/nodes, so scalability is a concern. This is my first non-trivial use of Python, and I want to make sure I'm taking proper advantage of the language (this is replacing a very convoluted set of SQL queries, and earlier versions of the Python version were essentially very ineffecient straight transalations of what that did). I don't normally do much programming, so I may be missing something elementary. Many thanks!

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• ListView: convertView / holder getting confused

  - by Steve H

  I'm working with a ListView, trying to get the convertView / referenceHolder optimisation to work properly but it's giving me trouble. (This is the system where you store the R.id.xxx pointers in as a tag for each View to avoid having to call findViewById). I have a ListView populated with simple rows of an ImageView and some text, but the ImageView can be formatted either for portrait-sized images (tall and narrow) or landscape-sized images (short and wide). It's adjusting this formatting for each row which isn't working as I had hoped. The basic system is that to begin with, it inflates the layout for each row and sets the ImageView's settings based on the data, and includes an int denoting the orientation in the tag containing the R.id.xxx values. Then when it starts reusing convertViews, it checks this saved orientation against the orientation of the new row. The theory then is that if the orientation is the same, then the ImageView should already be set up correctly. If it isn't, then it sets the parameters for the ImageView as appropriate and updates the tag. However, I found that it was somehow getting confused; sometimes the tag would get out of sync with the orientation of the ImageView. For example, the tag would still say portrait, but the actual ImageView would still be in landscape layout. I couldn't find a pattern to how or when this happened; it wasn't consistent by orientation, position in the list or speed of scrolling. I can solve the problem by simply removing the check about convertView's orientation and simply always set the ImageView's parameters, but that seems to defeat the purpose of this optimisation. Can anyone see what I've done wrong in the code below? static LinearLayout.LayoutParams layoutParams; (...) public View getView(int position, View convertView, ViewGroup parent){ ReferenceHolder holder; if (convertView == null){ convertView = inflater.inflate(R.layout.pick_image_row, null); holder = new ReferenceHolder(); holder.getIdsAndSetTag(convertView, position); if (data[position][ORIENTATION] == LANDSCAPE) { // Layout defaults to portrait settings, so ImageView size needs adjusting. // layoutParams is modified here, with specific values for width, height, margins etc holder.image.setLayoutParams(layoutParams); } holder.orientation = data[position][ORIENTATION]; } else { holder = (ReferenceHolder) convertView.getTag(); if (holder.orientation != data[position][ORIENTATION]){ //This is the key if statement for my question switch (image[position][ORIENTATION]) { case PORTRAIT: // layoutParams is reset to the Portrait settings holder.orientation = data[position][ORIENTATION]; break; case LANDSCAPE: // layoutParams is reset to the Landscape settings holder.orientation = data[position][ORIENTATION]; break; } holder.image.setLayoutParams(layoutParams); } } // and the row's image and text is set here, using holder.image.xxx // and holder.text.xxx return convertView; } static class ReferenceHolder { ImageView image; TextView text; int orientation; void getIdsAndSetTag(View v, int position){ image = (ImageView) v.findViewById(R.id.pickImageImage); text = (TextView) v.findViewById(R.id.pickImageText); orientation = data[position][ORIENTATION]; v.setTag(this); } } Thanks!

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• How to solve a deallocated connection in iPhone SDK 3.1.3? - Streams - CFSockets

  - by Christian

  Hi everyone, Debugging my implementation I found a memory leak issue. I know where is the issue, I tried to solve it but sadly without success. I will try to explain you, maybe someone of you can help with this. First I have two classes involved in the issue, the publish class (where publishing the service and socket configuration is done) and the connection (where the socket binding and the streams configuration is done). The main issue is in the connection via native socket. In the 'publish' class the "server" accepts a connection with a callback. The callback has the native-socket information. Then, a connection with native-socket information is created. Next, the socket binding and the streams configuration is done. When those actions are successful the instance of the connection is saved in a mutable array. Thus, the connection is established. static void AcceptCallback(CFSocketRef socket, CFSocketCallBackType type, CFDataRef address, const void *data, void *info) { Publish *rePoint = (Publish *)info; if ( type != kCFSocketAcceptCallBack) { return; } CFSocketNativeHandle nativeSocketHandle = *((CFSocketNativeHandle *)data); NSLog(@"The AcceptCallback was called, a connection request arrived to the server"); [rePoint handleNewNativeSocket:nativeSocketHandle]; } - (void)handleNewNativeSocket:(CFSocketNativeHandle)nativeSocketHandle{ Connection *connection = [[[Connection alloc] initWithNativeSocketHandle:nativeSocketHandle] autorelease]; // Create the connection if (connection == nil) { close(nativeSocketHandle); return; } NSLog(@"The connection from the server was created now try to connect"); if ( ! [connection connect]) { [connection close]; return; } [clients addObject:connection]; //save the connection trying to avoid the deallocation } The next step is receive the information from the client, thus a read-stream callback is triggered with the information of the established connection. But when the callback-handler tries to use this connection the error occurs, it says that such connection is deallocated. The issue here is that I don't know where/when the connection is deallocated and how to know it. I am using the debugger, but after some trials, I don't see more info. void myReadStreamCallBack (CFReadStreamRef stream, CFStreamEventType eventType, void *info) { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; Connection *handlerEv = [[(Connection *)info retain] autorelease]; // The error -[Connection retain]: message sent to deallocated instance 0x1f5ef0 (Where 0x1f5ef0 is the reference to the established connection) [handlerEv readStreamHandleEvent:stream andEvent:eventType]; [pool drain]; } void myWriteStreamCallBack (CFWriteStreamRef stream, CFStreamEventType eventType, void *info){ NSAutoreleasePool *p = [[NSAutoreleasePool alloc] init]; Connection *handlerEv = [[(Connection *)info retain] autorelease]; //Sometimes the error also happens here, I tried without the pool, but it doesn't help neither. [handlerEv writeStreamHandleEvent:eventType]; [p drain]; } Something strange is that when I run the debugger(with breakpoints) everything goes well, the connection is not deallocated and the callbacks work fine and the server is able to receive the message. I will appreciate any hint!

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• multiple-inheritance substitution

  - by Luigi

  I want to write a module (framework specific), that would wrap and extend Facebook PHP-sdk (https://github.com/facebook/php-sdk/). My problem is - how to organize classes, in a nice way. So getting into details - Facebook PHP-sdk consists of two classes: BaseFacebook - abstract class with all the stuff sdk does Facebook - extends BaseFacebook, and implements parent abstract persistance-related methods with default session usage Now I have some functionality to add: Facebook class substitution, integrated with framework session class shorthand methods, that run api calls, I use mostly (through BaseFacebook::api()), authorization methods, so i don't have to rewrite this logic every time, configuration, sucked up from framework classes, insted of passed as params caching, integrated with framework cache module I know something has gone very wrong, because I have too much inheritance that doesn't look very normal.Wrapping everything in one "complex extension" class also seems too much. I think I should have few working togheter classes - but i get into problems like: if cache class doesn't really extend and override BaseFacebook::api() method - shorthand and authentication classes won't be able to use the caching. Maybe some kind of a pattern would be right in here? How would you organize these classes and their dependencies? EDIT 04.07.2012 Bits of code, related to the topic: This is how the base class of Facebook PHP-sdk: abstract class BaseFacebook { // ... some methods public function api(/* polymorphic */) { // ... method, that makes api calls } public function getUser() { // ... tries to get user id from session } // ... other methods abstract protected function setPersistentData($key, $value); abstract protected function getPersistentData($key, $default = false); // ... few more abstract methods } Normaly Facebook class extends it, and impelements those abstract methods. I replaced it with my substitude - Facebook_Session class: class Facebook_Session extends BaseFacebook { protected function setPersistentData($key, $value) { // ... method body } protected function getPersistentData($key, $default = false) { // ... method body } // ... implementation of other abstract functions from BaseFacebook } Ok, then I extend this more with shorthand methods and configuration variables: class Facebook_Custom extends Facebook_Session { public funtion __construct() { // ... call parent's constructor with parameters from framework config } public function api_batch() { // ... a wrapper for parent's api() method return $this->api('/?batch=' . json_encode($calls), 'POST'); } public function redirect_to_auth_dialog() { // method body } // ... more methods like this, for common queries / authorization } I'm not sure, if this isn't too much for a single class ( authorization / shorthand methods / configuration). Then there comes another extending layer - cache: class Facebook_Cache extends Facebook_Custom { public function api() { $cache_file_identifier = $this->getUser(); if(/* cache_file_identifier is not null and found a valid file with cached query result */) { // return the result } else { try { // call Facebook_Custom::api, cache and return the result } catch(FacebookApiException $e) { // if Access Token is expired force refreshing it parent::redirect_to_auth_dialog(); } } } // .. some other stuff related to caching } Now this pretty much works. New instance of Facebook_Cache gives me all the functionality. Shorthand methods from Facebook_Custom use caching, because Facebook_Cache overwrited api() method. But here is what is bothering me: I think it's too much inheritance. It's all very tight coupled - like look how i had to specify 'Facebook_Custom::api' instead of 'parent:api', to avoid api() method loop on Facebook_Cache class extending. Overall mess and ugliness. So again, this works but I'm just asking about patterns / ways of doing this in a cleaner and smarter way.

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• Adding functionality to any TextReader

  - by strager

  I have a Location class which represents a location somewhere in a stream. (The class isn't coupled to any specific stream.) The location information will be used to match tokens to location in the input in my parser, to allow for nicer error reporting to the user. I want to add location tracking to a TextReader instance. This way, while reading tokens, I can grab the location (which is updated by the TextReader as data is read) and give it to the token during the tokenization process. I am looking for a good approach on accomplishing this goal. I have come up with several designs. Manual location tracking Every time I need to read from the TextReader, I call AdvanceString on the Location object of the tokenizer with the data read. Advantages Very simple. No class bloat. No need to rewrite the TextReader methods. Disadvantages Couples location tracking logic to tokenization process. Easy to forget to track something (though unit testing helps with this). Bloats existing code. Plain TextReader wrapper Create a LocatedTextReaderWrapper class which surrounds each method call, tracking a Location property. Example: public class LocatedTextReaderWrapper : TextReader { private TextReader source; public Location Location { get; set; } public LocatedTextReaderWrapper(TextReader source) : this(source, new Location()) { } public LocatedTextReaderWrapper(TextReader source, Location location) { this.Location = location; this.source = source; } public override int Read(char[] buffer, int index, int count) { int ret = this.source.Read(buffer, index, count); if(ret >= 0) { this.location.AdvanceString(string.Concat(buffer.Skip(index).Take(count))); } return ret; } // etc. } Advantages Tokenization doesn't know about Location tracking. Disadvantages User needs to create and dispose a LocatedTextReaderWrapper instance, in addition to their TextReader instance. Doesn't allow different types of tracking or different location trackers to be added without layers of wrappers. Event-based TextReader wrapper Like LocatedTextReaderWrapper, but decouples it from the Location object raising an event whenever data is read. Advantages Can be reused for other types of tracking. Tokenization doesn't know about Location tracking or other tracking. Can have multiple, independent Location objects (or other methods of tracking) tracking at once. Disadvantages Requires boilerplate code to enable location tracking. User needs to create and dispose the wrapper instance, in addition to their TextReader instance. Aspect-orientated approach Use AOP to perform like the event-based wrapper approach. Advantages Can be reused for other types of tracking. Tokenization doesn't know about Location tracking or other tracking. No need to rewrite the TextReader methods. Disadvantages Requires external dependencies, which I want to avoid. I am looking for the best approach in my situation. I would like to: Not bloat the tokenizer methods with location tracking. Not require heavy initialization in user code. Not have any/much boilerplate/duplicated code. (Perhaps) not couple the TextReader with the Location class. Any insight into this problem and possible solutions or adjustments are welcome. Thanks! (For those who want a specific question: What is the best way to wrap the functionality of a TextReader?) I have implemented the "Plain TextReader wrapper" and "Event-based TextReader wrapper" approaches and am displeased with both, for reasons mentioned in their disadvantages.

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• Linker errors between multiple projects in Visual C++

  - by rlbond

  Hi, I have a solution with multiple projects. I have a "main" project, which acts as a menu and from there, the user can access any of the other projects. On this main project, I get linker errors for every function called. How do I avoid these linker errors? I set the project dependencies already in the "Project Dependencies..." dialog. Thanks EDIT -- I did as suggested and added the output folder to the linker's additional directories. Now, however, I get a million errors as follows: 3msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: void __thiscall std::basic_ios ::setstate(int,bool)" (?setstate@?$basic_ios@DU?$char_traits@D@std@@@std@@QAEXH_N@Z) already defined in panels.lib(panel_main.obj) 3msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: int __thiscall std::ios_base::width(int)" (?width@ios_base@std@@QAEHH@Z) already defined in panels.lib(panel_main.obj) 3msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: int __thiscall std::basic_streambuf ::sputn(char const *,int)" (?sputn@?$basic_streambuf@DU?$char_traits@D@std@@@std@@QAEHPBDH@Z) already defined in panels.lib(panel_main.obj) 3msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: static bool __cdecl std::char_traits::eq_int_type(int const &,int const &)" (?eq_int_type@?$char_traits@D@std@@SA_NABH0@Z) already defined in panels.lib(panel_main.obj) 3msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: static int __cdecl std::char_traits::eof(void)" (?eof@?$char_traits@D@std@@SAHXZ) already defined in panels.lib(panel_main.obj) 3msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: int __thiscall std::basic_streambuf ::sputc(char)" (?sputc@?$basic_streambuf@DU?$char_traits@D@std@@@std@@QAEHD@Z) already defined in panels.lib(panel_main.obj) 3msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: class std::basic_streambuf * __thiscall std::basic_ios ::rdbuf(void)const " (?rdbuf@?$basic_ios@DU?$char_traits@D@std@@@std@@QBEPAV?$basic_streambuf@DU?$char_traits@D@std@@@2@XZ) already defined in panels.lib(panel_main.obj) 3msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: char __thiscall std::basic_ios ::fill(void)const " (?fill@?$basic_ios@DU?$char_traits@D@std@@@std@@QBEDXZ) already defined in panels.lib(panel_main.obj) 3msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: int __thiscall std::ios_base::flags(void)const " (?flags@ios_base@std@@QBEHXZ) already defined in panels.lib(panel_main.obj) 3msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: int __thiscall std::ios_base::width(void)const " (?width@ios_base@std@@QBEHXZ) already defined in panels.lib(panel_main.obj) 3msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: static unsigned int __cdecl std::char_traits::length(char const *)" (?length@?$char_traits@D@std@@SAIPBD@Z) already defined in panels.lib(panel_main.obj) 3msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: class std::basic_ostream & __thiscall std::basic_ostream ::flush(void)" (?flush@?$basic_ostream@DU?$char_traits@D@std@@@std@@QAEAAV12@XZ) already defined in panels.lib(panel_main.obj) 3msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: class std::basic_ostream * __thiscall std::basic_ios ::tie(void)const " (?tie@?$basic_ios@DU?$char_traits@D@std@@@std@@QBEPAV?$basic_ostream@DU?$char_traits@D@std@@@2@XZ) already defined in panels.lib(panel_main.obj) 3msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: bool __thiscall std::ios_base::good(void)const " (?good@ios_base@std@@QBE_NXZ) already defined in panels.lib(panel_main.obj) 3msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: void __thiscall std::basic_ostream ::_Osfx(void)" (?_Osfx@?$basic_ostream@DU?$char_traits@D@std@@@std@@QAEXXZ) already defined in panels.lib(panel_main.obj) 3msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: void __thiscall std::basic_streambuf ::_Lock(void)" (?_Lock@?$basic_streambuf@DU?$char_traits@D@std@@@std@@QAEXXZ) already defined in panels.lib(panel_main.obj) 3msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: void __thiscall std::basic_streambuf ::_Unlock(void)" (?_Unlock@?$basic_streambuf@DU?$char_traits@D@std@@@std@@QAEXXZ) already defined in panels.lib(panel_main.obj) 3msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: class std::locale::facet * __thiscall std::locale::facet::_Decref(void)" (?_Decref@facet@locale@std@@QAEPAV123@XZ) already defined in panels.lib(panel_main.obj) 3libcpmtd.lib(ios.obj) : error LNK2005: "private: static void __cdecl std::ios_base::_Ios_base_dtor(class std::ios_base *)" (?_Ios_base_dtor@ios_base@std@@CAXPAV12@@Z) already defined in msvcprtd.lib(MSVCP90D.dll) 3libcpmtd.lib(ios.obj) : error LNK2005: "public: static void __cdecl std::ios_base::_Addstd(class std::ios_base *)" (?_Addstd@ios_base@std@@SAXPAV12@@Z) already defined in msvcprtd.lib(MSVCP90D.dll) 3libcpmtd.lib(locale0.obj) : error LNK2005: "void __cdecl _AtModuleExit(void (__cdecl*)(void))" (?_AtModuleExit@@YAXP6AXXZ@Z) already defined in msvcprtd.lib(locale0_implib.obj) 3libcpmtd.lib(locale0.obj) : error LNK2005: __Fac_tidy already defined in msvcprtd.lib(locale0_implib.obj) 3libcpmtd.lib(locale0.obj) : error LNK2005: "private: static void __cdecl std::locale::facet::facet_Register(class std::locale::facet *)" (?facet_Register@facet@locale@std@@CAXPAV123@@Z) already defined in msvcprtd.lib(locale0_implib.obj) 3libcpmtd.lib(locale0.obj) : error LNK2005: "private: static class std::locale::_Locimp * __cdecl std::locale::_Getgloballocale(void)" (?_Getgloballocale@locale@std@@CAPAV_Locimp@12@XZ) already defined in msvcprtd.lib(MSVCP90D.dll) 3libcpmtd.lib(locale0.obj) : error LNK2005: "private: static class std::locale::_Locimp * __cdecl std::locale::_Init(void)" (?_Init@locale@std@@CAPAV_Locimp@12@XZ) already defined in msvcprtd.lib(MSVCP90D.dll) 3libcpmtd.lib(locale0.obj) : error LNK2005: "public: static void __cdecl std::_Locinfo::_Locinfo_ctor(class std::_Locinfo *,class std::basic_string,class std::allocator const &)" (?_Locinfo_ctor@_Locinfo@std@@SAXPAV12@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@2@@Z) already defined in msvcprtd.lib(MSVCP90D.dll) 3libcpmtd.lib(locale0.obj) : error LNK2005: "public: static void __cdecl std::_Locinfo::_Locinfo_dtor(class std::_Locinfo *)" (?_Locinfo_dtor@_Locinfo@std@@SAXPAV12@@Z) already defined in msvcprtd.lib(MSVCP90D.dll) 3libcpmtd.lib(xlock.obj) : error LNK2005: "public: __thiscall std::_Lockit::_Lockit(int)" (??0_Lockit@std@@QAE@H@Z) already defined in msvcprtd.lib(MSVCP90D.dll) 3libcpmtd.lib(xlock.obj) : error LNK2005: "public: __thiscall std::_Lockit::~_Lockit(void)" (??1_Lockit@std@@QAE@XZ) already defined in msvcprtd.lib(MSVCP90D.dll)

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• IErrorHandler doesn't seem to be handling my errors in WCF .. any ideas?

  - by John Nicholas

  Have been readign around on IErrorHandler and want to go the config route. so, I have read the following in an attempt to implement it. MSDN Keyvan Nayyeri blog about the type defintion Rory Primrose Blog I have got it to compile and from the various errors i have fixed it seems like WCF is actually loading the error handler. My problem is that the exception that i am throwing to handle in the error handler doesn;t get the exception passed to it. My service implementation simply calls a method on another class that throws ArgumentOutOfRangeException - however this exception never gets handled by the handler. My web.config <system.serviceModel> <bindings> <basicHttpBinding> <binding name="basic"> <security mode="None" /> </binding> </basicHttpBinding> </bindings> <extensions> <behaviorExtensions> <add name="customHttpBehavior" type="ErrorHandlerTest.ErrorHandlerElement, ErrorHandlerTest, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" /> </behaviorExtensions> </extensions> <behaviors> <serviceBehaviors> <behavior name="exceptionHandlerBehaviour"> <serviceMetadata httpGetEnabled="true"/> <!-- To receive exception details in faults for debugging purposes, set the value below to true. Set to false before deployment to avoid disclosing exception information --> <serviceDebug includeExceptionDetailInFaults="true"/> <customHttpBehavior /> </behavior> </serviceBehaviors> </behaviors> <services> <service behaviorConfiguration="exceptionHandlerBehaviour" name="ErrorHandlerTest.Service1"> <endpoint binding="basicHttpBinding" bindingConfiguration="basic" contract="ErrorHandlerTest.IService1" /> </service> </services> Service Contract [ServiceContract] public interface IService1 { [OperationContract] [FaultContract(typeof(GeneralInternalFault))] string GetData(int value); } The ErrorHandler class public class ErrorHandler : IErrorHandler , IServiceBehavior { public bool HandleError(Exception error) { Console.WriteLine("caught exception {0}:",error.Message ); return true; } public void ProvideFault(Exception error, MessageVersion version, ref Message fault) { if (fault!=null ) { if (error is ArgumentOutOfRangeException ) { var fe = new FaultException<GeneralInternalFault>(new GeneralInternalFault("general internal fault.")); MessageFault mf = fe.CreateMessageFault(); fault = Message.CreateMessage(version, mf, fe.Action); } else { var fe = new FaultException<GeneralInternalFault>(new GeneralInternalFault(" the other general internal fault.")); MessageFault mf = fe.CreateMessageFault(); fault = Message.CreateMessage(version, mf, fe.Action); } } } public void AddBindingParameters(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase, System.Collections.ObjectModel.Collection<ServiceEndpoint> endpoints, BindingParameterCollection bindingParameters) { } public void ApplyDispatchBehavior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase) { IErrorHandler errorHandler = new ErrorHandler(); foreach (ChannelDispatcherBase channelDispatcherBase in serviceHostBase.ChannelDispatchers) { ChannelDispatcher channelDispatcher = channelDispatcherBase as ChannelDispatcher; if (channelDispatcher != null) { channelDispatcher.ErrorHandlers.Add(errorHandler); } } } public void Validate(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase) { } } And the Behaviour Extension Element public class ErrorHandlerElement : BehaviorExtensionElement { protected override object CreateBehavior() { return new ErrorHandler(); } public override Type BehaviorType { get { return typeof(ErrorHandler); } } }

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• CSS/JavaScript/hacking: Detect :visited styling on a link *without* checking it directly OR do it fa

  - by Sai Emrys

  This is for research purposes on http://cssfingerprint.com Consider the following code: <style> div.csshistory a { display: none; color: #00ff00;} div.csshistory a:visited { display: inline; color: #ff0000;} </style> <div id="batch" class="csshistory"> <a id="1" href="http://foo.com">anything you want here</a> <a id="2" href="http://bar.com">anything you want here</a> [etc * ~2000] </div> My goal is to detect whether foo has been rendered using the :visited styling. I want to detect whether foo.com is visited without directly looking at $('1').getComputedStyle (or in Internet Explorer, currentStyle), or any other direct method on that element. The purpose of this is to get around a potential browser restriction that would prevent direct inspection of the style of visited links. For instance, maybe you can put a sub-element in the <a> tag, or check the styling of the text directly; etc. Any method that does not directly or indierctly rely on $('1').anything is acceptable. Doing something clever with the child or parent is probably necessary. Note that for the purposes of this point only, the scenario is that the browser will lie to JavaScript about all properties of the <a> element (but not others), and that it will only render color: in :visited. Therefore, methods that rely on e.g. text size or background-image will not meet this requirement. I want to improve the speed of my current scraping methods. The majority of time (at least with the jQuery method in Firefox) is spent on document.body.appendChild(batch), so finding a way to improve that call would probably most effective. See http://cssfingerprint.com/about and http://cssfingerprint.com/results for current speed test results. The methods I am currently using can be seen at http://github.com/saizai/cssfingerprint/blob/master/public/javascripts/history_scrape.js To summarize for tl;dr, they are: set color or display on :visited per above, and check each one directly w/ getComputedStyle put the ID of the link (plus a space) inside the <a> tag, and using jQuery's :visible selector, extract only the visible text (= the visited link IDs) FWIW, I'm a white hat, and I'm doing this in consultation with the EFF and some other fairly well known security researchers. If you contribute a new method or speedup, you'll get thanked at http://cssfingerprint.com/about (if you want to be :-P), and potentially in a future published paper. ETA: The bounty will be rewarded only for suggestions that can, on Firefox, avoid the hypothetical restriction described in point 1 above, or perform at least 10% faster, on any browser for which I have sufficient current data, than my best performing methods listed in the graph at http://cssfingerprint.com/about In case more than one suggestion fits either criterion, the one that does best wins.

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• Python/numpy tricky slicing problem

  - by daver

  Hi stack overflow, I have a problem with some numpy stuff. I need a numpy array to behave in an unusual manner by returning a slice as a view of the data I have sliced, not a copy. So heres an example of what I want to do: Say we have a simple array like this: a = array([1, 0, 0, 0]) I would like to update consecutive entries in the array (moving left to right) with the previous entry from the array, using syntax like this: a[1:] = a[0:3] This would get the following result: a = array([1, 1, 1, 1]) Or something like this: a[1:] = 2*a[:3] # a = [1,2,4,8] To illustrate further I want the following kind of behaviour: for i in range(len(a)): if i == 0 or i+1 == len(a): continue a[i+1] = a[i] Except I want the speed of numpy. The default behavior of numpy is to take a copy of the slice, so what I actually get is this: a = array([1, 1, 0, 0]) I already have this array as a subclass of the ndarray, so I can make further changes to it if need be, I just need the slice on the right hand side to be continually updated as it updates the slice on the left hand side. Am I dreaming or is this magic possible? Update: This is all because I am trying to use Gauss-Seidel iteration to solve a linear algebra problem, more or less. It is a special case involving harmonic functions, I was trying to avoid going into this because its really not necessary and likely to confuse things further, but here goes. The algorithm is this: while not converged: for i in range(len(u[:,0])): for j in range(len(u[0,:])): # skip over boundary entries, i,j == 0 or len(u) u[i,j] = 0.25*(u[i-1,j] + u[i+1,j] + u[i, j-1] + u[i,j+1]) Right? But you can do this two ways, Jacobi involves updating each element with its neighbours without considering updates you have already made until the while loop cycles, to do it in loops you would copy the array then update one array from the copied array. However Gauss-Seidel uses information you have already updated for each of the i-1 and j-1 entries, thus no need for a copy, the loop should essentially 'know' since the array has been re-evaluated after each single element update. That is to say, every time we call up an entry like u[i-1,j] or u[i,j-1] the information calculated in the previous loop will be there. I want to replace this slow and ugly nested loop situation with one nice clean line of code using numpy slicing: u[1:-1,1:-1] = 0.25(u[:-2,1:-1] + u[2:,1:-1] + u[1:-1,:-2] + u[1:-1,2:]) But the result is Jacobi iteration because when you take a slice: u[:,-2,1:-1] you copy the data, thus the slice is not aware of any updates made. Now numpy still loops right? Its not parallel its just a faster way to loop that looks like a parallel operation in python. I want to exploit this behaviour by sort of hacking numpy to return a pointer instead of a copy when I take a slice. Right? Then every time numpy loops, that slice will 'update' or really just replicate whatever happened in the update. To do this I need slices on both sides of the array to be pointers. Anyway if there is some really really clever person out there that awesome, but I've pretty much resigned myself to believing the only answer is to loop in C.

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• Delphi - Why is my global variable "inacessible" when i debug

  - by Antoine Lpy

  I'm building an application that contains around 30 Forms. I need to manage sessions, so I would like to have a global LoggedInUser variable accessible from all forms. I read "David Heffernan"'s post about global variables, and how to avoid them but I thought it would be easier to have a global User variable rather than 30 forms having their own User variable. So i have a unit : GlobalVars unit GlobalVars; interface uses User; // I defined my TUser class in a unit called User var LoggedInUser: TUser; implementation initialization LoggedInUser:= TUser.Create; finalization LoggedInUser.Free; end. Then in my LoginForm's LoginBtnClick procedure I do : unit FormLogin; interface uses [...],User; type TForm1 = class(TForm) [...] procedure LoginBtnClick(Sender: TObject); private { Déclarations privées } public end; var Form1: TForm1; AureliusConnection : IDBConnection; implementation {$R *.fmx} uses [...]GlobalVars; procedure TForm1.LoginBtnClick(Sender: TObject); var Manager : TObjectManager; MyCriteria: TCriteria<TUser>; u : TUser; begin Manager := TObjectManageR.Create(AureliusConnection); MyCriteria :=Manager.Find<TUtilisateur> .Add(TExpression.Eq('login',LoginEdit.Text)) .Add(TExpression.Eq('password',PasswordEdit.Text)); u := MyCriteria.UniqueResult; if u = nil then MessageDlg('Login ou mot de passe incorrect',TMsgDlgType.mtError,[TMsgDlgBtn.mbOK],0) else begin LoggedInUser:=u; //Here I assign my local User data to my global User variable Form1.Destroy; A00Form.visible:=true; end; Manager.Free; end; Then in another form I would like to access this LoggedInUser object in the Menu1BtnClick procedure : Unit C01_Deviations; interface uses System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants, FMX.Types, FMX.Graphics, FMX.Controls, FMX.Forms, FMX.Dialogs, FMX.StdCtrls, FMX.ListView.Types, FMX.ListView, FMX.Objects, FMX.Layouts, FMX.Edit, FMX.Ani; type TC01Form = class(TForm) [...] Menu1Btn: TButton; [...] procedure Menu1BtnClick(Sender: TObject); private { Déclarations privées } public { Déclarations publiques } end; var C01Form: TC01Form; implementation uses [...]User,GlobalVars; {$R *.fmx} procedure TC01Form.Menu1BtnClick(Sender: TObject); var Assoc : TUtilisateur_FonctionManagement; ValidationOK : Boolean; util : TUser; begin ValidationOK := False; util := GlobalVars.LoggedInUser; // Here i created a local user variable for debug purposes as I thought it would permit me to see the user data. But i get "Inaccessible Value" as its value util.Nom:='test'; for Assoc in util.FonctionManagement do // Here is were my initial " access violation" error occurs begin if Assoc.FonctionManagement.Libelle = 'Reponsable équipe HACCP' then begin ValidationOK := True; break; end; end; [...] end; When I debug I see "Inaccessible Value" in the value column of my user. Do you have any idea why ? I tried to put an integer in this GlobalVar unit, and i was able to set its value from my login form and read it from my other form.. I guess I could store the user's id, which is an integer, and then retrieve the user from the database using its id. But it seems really unefficient.

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• CSS: Labels in table columns

  - by hello

  Hello. BACKGROUND: I would like to have small labels in columns of a table. I'm using some implemented parts of HTML5/CSS3 in my project, and this section specifically is for mobile devices. While both facts are not necessarily relevant, the bottom line is that I don't have to support Internet Explorer or even Firefox for that matter (just WebKit). THE PROBLEM With my current CSS approach, the vertical padding of the cell comes from the <span element (set to display: block with top/bottom margins), which contains the "value" of the column. As a result there's no padding when the <span> is empty or missing (no value) and the label is not in place. The "full" coulmns should give you the idea of where I want the labels to be, even if there's no value, and the <span> is not there. I realize that I could use "non-breaking-space", but I would really like to avoid it. I wonder if any of you have a fix / better way to do this? current code is below. Thank you for any help. <!DOCTYPE html> <html lang="en"> <head> <title>ah</title> <style> body { width: 320px; } /* TABLE */ table { width: 100%; border-collapse: collapse; font-family: arial; } th, td { border: 1px solid #ccc; border-width: 0px 0px 1px 1px; } th:last-child, td:last-child { border-right-width: 1px; } tr:first-child th { border-top-width: 1px; background: #efefef; } /* RELEVANT STUFF */ td { padding: 3px; } td sup { display: block; } td span { display: block; margin: 3px 0px; text-align: center; } </style> </head> <body> <table> <tr> <th colspan="3">something</th> </tr> <tr> <td>^{some label}<span>any content</span></td> <td>^{some label}<span>any content</span></td> <td>^{some label}<span></span></td><!-- No content, just a label --> </tr> </table> </body> </html>

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• A format for storing personal contacts in a database

  - by Gart

  I'm thinking of the best way to store personal contacts in a database for a business application. The traditional and straightforward approach would be to create a table with columns for each element, i.e. Name, Telephone Number, Job title, Address, etc... However, there are known industry standards for this kind of data, like for example vCard, or hCard, or vCard-RDF/XML or even Windows Contacts XML Schema. Utilizing an standard format would offer some benefits, like inter-operablilty with other systems. But how can I decide which method to use? The requirements are mainly to store the data. Search and ordering queries are highly unlikely but possible. The volume of the data is 100,000 records at maximum. My database engine supports native XML columns. I have been thinking to use some XML-based format to store the personal contacts. Then it will be possible to utilize XML indexes on this data, if searching and ordering is needed. Is this a good approach? Which contacts format and schema would you recommend for this? Edited after first answers Here is why I think the straightforward approach is bad. This is due to the nature of this kind of data - it is not that simple. The personal contacts it is not well-structured data, it may be called semi-structured. Each contact may have different data fields, maybe even such fields which I cannot anticipate. In my opinion, each piece of this data should be treated as important information, i.e. no piece of data could be discarded just because there was no relevant column in the database. If we took it further, assuming that no data may be lost, then we could create a big text column named Comment or Description or Other and put there everything which cannot be fitted well into table columns. But then again - the data would lose structure - this might be bad. If we wanted structured data then - according to the database design principles - the data should be decomposed into entities, and relations should be established between the entities. But this adds complexity - there are just too many entities, and lots of design desicions should be made, like "How do we store Address? Personal Name? Phone number? How do we encode home phone numbers and mobile phone numbers? How about other contact info?.." The relations between entities are complex and multiple, and each relation is a table in the database. Each relation needs to be documented in the design papers. That is a lot of work to do. But it is possible to avoid the complexity entirely - just document that the data is stored according to such and such standard schema, period. Then anybody who would be reading that document should easily understand what it was all about. Finally, this is all about using an industry standard. The standard is, hopefully, designed by some clever people who anticipated and described the structure of personal contacts information much better than I ever could. Why should we all reinvent the wheel?? It's much easier to use a standard schema. The problem is, there are just too many standards - it's not easy to decide which one to use!

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• PROJECT HELP NEEDED. SOME BASIC CONCEPTS GREAT CONFUSION BECAUSE OF LACK OF PROPER MATERIAL PLEASE H

  - by user287745

  Task ATTENDENCE RECORDER AND MANAGEMENT SYSTEM IN DISTRIBUTED ENVIRONMENT ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Example implementation needed. a main server in each lab where the operator punches in the attendence of the student. =========================================================== scenerio:- a college, 10 departments, all departments have a computer lab with 60-100 computers, the computers within each lab are interconnected and all computers in any department have to dail to a particular number (THE NUMBER GIVEN BY THE COLLEGE INTERNET DEPARTMENT) to get connected to the internet. therefore safe to assume that there is a central location to which all the computers in the college are connected to. there is a 'students attendence portal' which can be accessed using internet explorer, students enter there id and get the particular attendence record regarding to the labs only. a description of the working is like:- 1) the user will select which department, which year has arrived to the lab 2) the selection will give the user a return of all the students name and there roll numbers belonging to that department; 'with a check box to "TICK MARK IF THE STUDENT IS PRESENT" ' 3) A SUBMIT BUTTON when pressed reads the 'id' of the checkbox to determine the "particular count number of the student" from that an id of the student is constructed and that id is inserted with a present. (there is also date and time and much more to normalize the db and to avoid conflicts and keep historic records etc but that you will have to assume) steps taken till this date:- ( please note we are not computer students, we are to select something of some other line as a project!, as you will read in my many post 'i" have designed small websites just out of liking. have never ever done any thing official to implement like this.) * have made the database fully normalized. * have made the website which does the functions required on the database. Testing :- deployed the db and site on a free aspspider server and it worked. tested from several computers. Now the problem please help thank youuuuuuuu a practical demonstration has to be done within the college network. no internet! we have been assigned a lab - 60 computers- to demonstrate. (please dont give replies as 60 computers only! is not a big deal one CPU can manage it. i know that; IT IS A HYPOTHETICAL SITUATION WHERE WE ASSUME THAT 60 IS NOT 60 BUT ITS LIKE 60,000 COMPUTERS) 1a) make a web server, yes iis and put files in www folder and configure server to run aspx files- although a link to a step by step guide will be appreciated)\ ? which version of windows should i ask for xp or win server 2000 something? 2a) make a database server. ( well yes install sql server 2005, okay but then what? just put the database file on a pc share it and append the connection string to the share? ) 3a) make the site accessible from the remaining computers ? http://localhost/sitename ? all users "being operators of the particular lab" have the right to edit, write or delete(in dispute), thereby any "users" who hate our program can make the database inconsistent by accessing te same record and doing different edits and then complaining? so how to prevent this? you know something like when the db table is being written to others can only read but not write.. one big confusion:- IN DISTRIBUTED ENVIRONMENT "how to implement this" where does "distributed environment" come in! meaning :- alright the labs are in different departments but the "database server will be one" the "web server will be one" so whats distributed!?

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• TripleDES in Perl/PHP/ColdFusion

  - by Seidr

  Recently a problem arose regarding hooking up an API with a payment processor who were requesting a string to be encrypted to be used as a token, using the TripleDES standard. Our Applications run using ColdFusion, which has an Encrypt tag - that supports TripleDES - however the result we were getting back was not what the payment processor expected. First of all, here is the resulting token the payment processor were expecting. AYOF+kRtg239Mnyc8QIarw== And below is the snippet of ColdFusion we were using, and the resulting string. <!--- Coldfusion Crypt (here be monsters) ---> <cfset theKey="123412341234123412341234"> <cfset theString = "username=test123"> <cfset strEncodedEnc = Encrypt(theString, theKey, "DESEDE", "Base64")> <!--- resulting string(strEncodedEnc): tc/Jb7E9w+HpU2Yvn5dA7ILGmyNTQM0h ---> As you can see, this was not returning the string we were hoping for. Seeking a solution, we ditched ColdFusion for this process and attempted to reproduce the token in PHP. Now I'm aware that various languages implement encryption in different ways - for example in the past managing encryption between a C# application and PHP back-end, I've had to play about with padding in order to get the two to talk, but my experience has been that PHP generally behaves when it comes to encryption standards. Anyway, on to the PHP source we tried, and the resulting string. /* PHP Circus (here be Elephants) */ $theKey="123412341234123412341234"; $theString="username=test123"; $strEncodedEnc=base64_encode(mcrypt_ecb (MCRYPT_3DES, $theKey, $theString, MCRYPT_ENCRYPT)); /* resulting string(strEncodedEnc): sfiSu4mVggia8Ysw98x0uw== */ As you can plainly see, we've got another string that differs from both the string expected by the payment processor AND the one produced by ColdFusion. Cue head-against-wall integration techniques. After many to-and-fro communications with the payment processor (lots and lots of reps stating 'we can't help with coding issues, you must be doing it incorrectly, read the manual') we were finally escalated to someone with more than a couple of brain-cells to rub together, who was able to step back and actually look at and diagnose the issue. He agreed, our CF and PHP attempts were not resulting in the correct string. After a quick search, he also agreed that it was not neccesarily our source, but rather how the two languages implemented their vision of the TripleDES standard. Coming into the office this morning, we were met by an email with a snippet of source code, in Perl. This is was the code they were directly using on their end to produce the expected token. #!/usr/bin/perl # Perl Crypt Calamity (here be...something) use strict; use CGI; use MIME::Base64; use Crypt::TripleDES; my $cgi = CGI->new(); my $param = $cgi->Vars(); $param->{key} = "123412341234123412341234"; $param->{string} = "username=test123"; my $des = Crypt::TripleDES->new(); my $enc = $des->encrypt3($param->{string}, $param->{key}); $enc = encode_base64($enc); $enc =~ s/\n//gs; # resulting string (enc): AYOF+kRtg239Mnyc8QIarw== So, there we have it. Three languages, three implementations of what they quote in the documentation as TripleDES Standard Encryption, and three totally different resulting strings. My question is, from your experience of these three languages and their implementations of the TripleDES algorithm, have you been able to get any two of them to give the same response, and if so what tweaks to the code did you have to make in order to come to the result? I understand this is a very drawn out question, but I wanted to give clear and precise setting for each stage of testing that we had to perform. I'll also be performing some more investigatory work on this subject later, and will post any findings that I come up with to this question, so that others may avoid this headache.

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• boost::serialization with mutable members

  - by redmoskito

  Using boost::serialization, what's the "best" way to serialize an object that contains cached, derived values in mutable members, such that cached members aren't serialized, but on deserialization, they are initialized the their appropriate default. A definition of "best" follows later, but first an example: class Example { public: Example(float n) : num(n), sqrt_num(-1.0) {} float get_num() const { return num; } // compute and cache sqrt on first read float get_sqrt() const { if(sqrt_num < 0) sqrt_num = sqrt(num); return sqrt_num; } template <class Archive> void serialize(Archive& ar, unsigned int version) { ... } private: float num; mutable float sqrt_num; }; On serialization, only the "num" member should be saved. On deserialization, the sqrt_num member must be initialized to its sentinel value indicating it needs to be computed. What is the most elegant way to implement this? In my mind, an elegant solution would avoid splitting serialize() into separate save() and load() methods (which introduces maintenance problems). One possible implementation of serialize: template <class Archive> void serialize(Archive& ar, unsigned int version) { ar & num; sqrt_num = -1.0; } This handles the deserialization case, but in the serialization case, the cached value is killed and must be recomputed. Also, I've never seen an example of boost::serialize that explicitly sets members inside of serialize(), so I wonder if this is generally not recommended. Some might suggest that the default constructor handles this, for example: int main() { Example e; { std::ifstream ifs("filename"); boost::archive::text_iarchive ia(ifs); ia >> e; } cout << e.get_sqrt() << endl; return 0; } which works in this case, but I think fails if the object receiving the deserialized data has already been initialized, as in the example below: int main() { Example ex1(4); Example ex2(9); cout << ex1.get_sqrt() << endl; // outputs 2; cout << ex2.get_sqrt() << endl; // outputs 3; // the following two blocks should implement ex2 = ex1; // save ex1 to archive { std::ofstream ofs("filename"); boost::archive::text_oarchive oa(ofs); oa << ex1; } // read it back into ex2 { std::ifstream ifs("filename"); boost::archive::text_iarchive ia(ifs); ia >> ex2; } // these should be equal now, but aren't, // since Example::serialize() doesn't modify num_sqrt cout << ex1.get_sqrt() << endl; // outputs 2; cout << ex2.get_sqrt() << endl; // outputs 3; return 0; } I'm sure this issue has come up with others, but I have struggled to find any documentation on this particular scenario. Thanks!

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• Overriding Object.Equals() instance method in C#; now Code Analysis / FxCop warning CA2218: "should

  - by Chris W. Rea

  I've got a complex class in my C# project on which I want to be able to do equality tests. It is not a trivial class; it contains a variety of scalar properties as well as references to other objects and collections (e.g. IDictionary). For what it's worth, my class is sealed. To enable a performance optimization elsewhere in my system (an optimization that avoids a costly network round-trip), I need to be able to compare instances of these objects to each other for equality – other than the built-in reference equality – and so I'm overriding the Object.Equals() instance method. However, now that I've done that, Visual Studio 2008's Code Analysis a.k.a. FxCop, which I keep enabled by default, is raising the following warning: warning : CA2218 : Microsoft.Usage : Since 'MySuperDuperClass' redefines Equals, it should also redefine GetHashCode. I think I understand the rationale for this warning: If I am going to be using such objects as the key in a collection, the hash code is important. i.e. see this question. However, I am not going to be using these objects as the key in a collection. Ever. Feeling justified to suppress the warning, I looked up code CA2218 in the MSDN documentation to get the full name of the warning so I could apply a SuppressMessage attribute to my class as follows: [SuppressMessage("Microsoft.Naming", "CA2218:OverrideGetHashCodeOnOverridingEquals", Justification="This class is not to be used as key in a hashtable.")] However, while reading further, I noticed the following: How to Fix Violations To fix a violation of this rule, provide an implementation of GetHashCode. For a pair of objects of the same type, you must ensure that the implementation returns the same value if your implementation of Equals returns true for the pair. When to Suppress Warnings ----- Do not suppress a warning from this rule. [arrow & emphasis mine] So, I'd like to know: Why shouldn't I suppress this warning as I was planning to? Doesn't my case warrant suppression? I don't want to code up an implementation of GetHashCode() for this object that will never get called, since my object will never be the key in a collection. If I wanted to be pedantic, instead of suppressing, would it be more reasonable for me to override GetHashCode() with an implementation that throws a NotImplementedException? Update: I just looked this subject up again in Bill Wagner's good book Effective C#, and he states in "Item 10: Understand the Pitfalls of GetHashCode()": If you're defining a type that won't ever be used as the key in a container, this won't matter. Types that represent window controls, web page controls, or database connections are unlikely to be used as keys in a collection. In those cases, do nothing. All reference types will have a hash code that is correct, even if it is very inefficient. [...] In most types that you create, the best approach is to avoid the existence of GetHashCode() entirely. ... that's where I originally got this idea that I need not be concerned about GetHashCode() always.

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• wpf display staggered content

  - by Chris Cap

  I am trying to display a rather dynamic list of data in WPF. I have essentially a LineItem class that contains a list of strings and a line type. The line type separates different categories of line items. All line items with the same type should be displayed the same and their data should line up. For example, this list will contain an order summary. And the there will be a line type that represents something with a width and height. The width and height must line up vertically. However, there may be other line types that don't have to line up vertically. I want to produce a table similar to what you see below: ------------------------------------------------------------------ | some content here | some more content here | last content here | |----------------------------------------------------------------| | some content here | | last content here | |----------------------------------------------------------------| | spanning content that is longer then most | last content here | |----------------------------------------------------------------| | some content that can span a really long distance | ------------------------------------------------------------------ I attempted to do this by creating ListView with a single column that had a datatemplate that contained a grid with a fixed number of fields and then bind to the Colspan value. Unfortunately, this didn't work. I ended up with incorrect or overlapping content anytime I tried to do a column span. Here's the XAML I was working with <ListView ItemsSource="{Binding}" > <ListView.View> <GridView> <GridViewColumn Header="Content"> <GridViewColumn.CellTemplate> <DataTemplate> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition /> <ColumnDefinition /> <ColumnDefinition /> </Grid.ColumnDefinitions> <TextBlock Grid.Column="0" Grid.ColumnSpan="{Binding Path=Tokens[0].ColumnSpan}" Text="{Binding Path=Tokens[0].Content}" ></TextBlock> <TextBlock Grid.Column="1" Grid.ColumnSpan="{Binding Path=Tokens[1].ColumnSpan}" Text="{Binding Path=Tokens[1].Content}" ></TextBlock> <TextBlock Grid.Column="2" Text="{Binding Path=Tokens[2].Content}"></TextBlock> </Grid> </DataTemplate> </GridViewColumn.CellTemplate> </GridViewColumn> </GridView> </ListView.View> And here's the classes I was binding to public class DisplayLine { public LineType Linetype { get; set; } public List<Token> Tokens { get; set; } public DisplayLine() { Tokens = new List<Token>(); } } public class Token { public string Content { get; set; } public bool IsEmpty { get { return string.IsNullOrEmpty(Content); } } public int ColumnSpan { get; set; } public Token() { ColumnSpan = 1; } } Does anyone have any suggestions of maybe a way of making this work. I may be taking the wrong approach. I'm trying to avoid any solutions where I explcitily build something in the code behind as I'm using the MVVM pattern so it has to be something that I can bind from exposed through the controller. My intial plan was to create a factory and separate classes that display the data differently based on type. However, I'm struggling coming up with a strategy for this using MVVM as I really can't just build something and display it. I have toyed with the idea of making some kind of UI service class that is injected, but it would still require some pretty detailed UI information from the controller to do it's work.

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• How do I catch this WPF Bitmap loading exception?

  - by mmr

  I'm developing an application that loads bitmaps off of the web using .NET 3.5 sp1 and C#. The loading code looks like: try { CurrentImage = pics[unChosenPics[index]]; bi = new BitmapImage(CurrentImage.URI); // BitmapImage.UriSource must be in a BeginInit/EndInit block. bi.DownloadCompleted += new EventHandler(bi_DownloadCompleted); AssessmentImage.Source = bi; } catch { System.Console.WriteLine("Something broke during the read!"); } and the code to load on bi_DownloadCompleted is: void bi_DownloadCompleted(object sender, EventArgs e) { try { double dpi = 96; int width = bi.PixelWidth; int height = bi.PixelHeight; int stride = width * 4; // 4 bytes per pixel byte[] pixelData = new byte[stride * height]; bi.CopyPixels(pixelData, stride, 0); BitmapSource bmpSource = BitmapSource.Create(width, height, dpi, dpi, PixelFormats.Bgra32, null, pixelData, stride); AssessmentImage.Source = bmpSource; Loading.Visibility = Visibility.Hidden; AssessmentImage.Visibility = Visibility.Visible; } catch { System.Console.WriteLine("Exception when viewing bitmap."); } } Every so often, an image comes along that breaks the reader. I guess that's to be expected. However, rather than being caught by either of those try/catch blocks, the exception is apparently getting thrown outside of where I can handle it. I could handle it using global WPF exceptions, like this SO question. However, that will seriously mess up the control flow of my program, and I'd like to avoid that if at all possible. I have to do the double source assignment because it appears that many images are lacking in width/height parameters in the places where the microsoft bitmap loader expects them to be. So, the first assignment appears to force the download, and the second assignment gets the dpi/image dimensions happen properly. What can I do to catch and handle this exception? Stack trace: at MS.Internal.HRESULT.Check(Int32 hr) at System.Windows.Media.Imaging.BitmapFrameDecode.get_ColorContexts() at System.Windows.Media.Imaging.BitmapImage.FinalizeCreation() at System.Windows.Media.Imaging.BitmapImage.OnDownloadCompleted(Object sender, EventArgs e) at System.Windows.Media.UniqueEventHelper.InvokeEvents(Object sender, EventArgs args) at System.Windows.Media.Imaging.LateBoundBitmapDecoder.DownloadCallback(Object arg) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Boolean isSingleParameter) at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler) at System.Windows.Threading.DispatcherOperation.InvokeImpl() at System.Threading.ExecutionContext.runTryCode(Object userData) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Windows.Threading.DispatcherOperation.Invoke() at System.Windows.Threading.Dispatcher.ProcessQueue() at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Boolean isSingleParameter) at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler) at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Boolean isSingleParameter) at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam) at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg) at System.Windows.Threading.Dispatcher.TranslateAndDispatchMessage(MSG& msg) at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame) at System.Windows.Application.RunInternal(Window window) at LensComparison.App.Main() in C:\Users\Mark64\Documents\Visual Studio 2008\Projects\LensComparison\LensComparison\obj\Release\App.g.cs:line 48 at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart()

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• Need Help Setting Transparent Image to Clipboard

  - by AMissico

  I need help setting a transparent image to the clipboard. I keep getting "handle is invalid". Following is the specific code with the complete working project at ftp://missico.net/ImageVisualizer.zip. This is an image Debug Visualizer class library, but I made to run as executable for testing. (Note that window is a toolbox window and show in taskbar is set to false.) I was tired of having to perform a screen capture on the toolbox window, open with an image editor, and then deleting the background added due to the screen capture. So I thought I would quickly put the transparent image onto the clipboard. Well, the problem is...no transparency support for Clipboard.SetImage. Google to the rescue...not quite. This is what I have so far pulled from a number of sources. See the code for the main reference. My problem is the "invalid handle" when using CF_DIBV5. I imagine the problem is related to BITMAPV5HEADER and CreateDIBitmap. Any help from you GDI/GDI+ Wizards would be greatly appreciated. public static void SetClipboardData(Bitmap bitmap, IntPtr hDC) { const uint SRCCOPY = 0x00CC0020; const int CF_DIBV5 = 17; const int CF_BITMAP = 2; //'reference //'http://social.msdn.microsoft.com/Forums/en-US/winforms/thread/816a35f6-9530-442b-9647-e856602cc0e2 IntPtr memDC = CreateCompatibleDC(hDC); IntPtr memBM = CreateCompatibleBitmap(hDC, bitmap.Width, bitmap.Height); SelectObject(memDC, memBM); using (Graphics g = Graphics.FromImage(bitmap)) { IntPtr hBitmapDC = g.GetHdc(); IntPtr hBitmap = bitmap.GetHbitmap(); SelectObject(hBitmapDC, hBitmap); BitBlt(memDC, 0, 0, bitmap.Width, bitmap.Height, hBitmapDC, 0, 0, SRCCOPY); if (!OpenClipboard(IntPtr.Zero)) { throw new System.Runtime.InteropServices.ExternalException("Could not open Clipboard", new Win32Exception()); } if (!EmptyClipboard()) { throw new System.Runtime.InteropServices.ExternalException("Unable to empty Clipboard", new Win32Exception()); } //IntPtr hClipboard = SetClipboardData(CF_BITMAP, memBM); //works but image is not transparent //all my attempts result in SetClipboardData returning hClipboard = IntPtr.Zero IntPtr hClipboard = SetClipboardData(CF_DIBV5, memBM); //because if (hClipboard == IntPtr.Zero) { // InnerException: System.ComponentModel.Win32Exception // Message="The handle is invalid" // ErrorCode=-2147467259 // NativeErrorCode=6 // InnerException: throw new System.Runtime.InteropServices.ExternalException("Could not put data on Clipboard", new Win32Exception()); } if (!CloseClipboard()) { throw new System.Runtime.InteropServices.ExternalException("Could not close Clipboard", new Win32Exception()); } g.ReleaseHdc(hBitmapDC); } } private void __copyMenuItem_Click(object sender, EventArgs e) { //'Applications that I have verified can paste the clipboard custom data format PNG are: //' Word 2003 //' Excel 2003 using (Graphics g = __pictureBox.CreateGraphics()) { IntPtr hDC = g.GetHdc(); MemoryStream ms = new MemoryStream(); __pictureBox.Image.Save(ms, ImageFormat.Png); ms.Seek(0, SeekOrigin.Begin); Image imag = Image.FromStream(ms); // Derive BitMap object using Image instance, so that you can avoid the issue //"a graphics object cannot be created from an image that has an indexed pixel format" Bitmap img = new Bitmap(new Bitmap(imag)); SetClipboardData(img, hDC); g.ReleaseHdc(); } }

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• Writing more efficient xquery code (avoiding redundant iteration)

  - by Coquelicot

  Here's a simplified version of a problem I'm working on: I have a bunch of xml data that encodes information about people. Each person is uniquely identified by an 'id' attribute, but they may go by many names. For example, in one document, I might find <person id=1>Paul Mcartney</person> <person id=2>Ringo Starr</person> And in another I might find: <person id=1>Sir Paul McCartney</person> <person id=2>Richard Starkey</person> I want to use xquery to produce a new document that lists every name associated with a given id. i.e.: <person id=1> <name>Paul McCartney</name> <name>Sir Paul McCartney</name> <name>James Paul McCartney</name> </person> <person id=2> ... </person> The way I'm doing this now in xquery is something like this (pseudocode-esque): let $ids := distinct-terms( [all the id attributes on people] ) for $id in $ids return <person id={$id}> { for $unique-name in distinct-values ( for $name in ( [all names] ) where $name/@id=$id return $name ) return <name>{$unique-name}</name> } </person> The problem is that this is really slow. I imagine the bottleneck is the innermost loop, which executes once for every id (of which there are about 1200). I'm dealing with a fair bit of data (300 MB, spread over about 800 xml files), so even a single execution of the query in the inner loop takes about 12 seconds, which means that repeating it 1200 times will take about 4 hours (which might be optimistic - the process has been running for 3 hours so far). Not only is it slow, it's using a whole lot of virtual memory. I'm using Saxon, and I had to set java's maximum heap size to 10 GB (!) to avoid getting out of memory errors, and it's currently using 6 GB of physical memory. So here's how I'd really like to do this (in Pythonic pseudocode): persons = {} for id in ids: person[id] = set() for person in all_the_people_in_my_xml_document: persons[person.id].add(person.name) There, I just did it in linear time, with only one sweep of the xml document. Now, is there some way to do something similar in xquery? Surely if I can imagine it, a reasonable programming language should be able to do it (he said quixotically). The problem, I suppose, is that unlike Python, xquery doesn't (as far as I know) have anything like an associative array. Is there some clever way around this? Failing that, is there something better than xquery that I might use to accomplish my goal? Because really, the computational resources I'm throwing at this relatively simple problem are kind of ridiculous.

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• Windows NT Service shutdown issues

  - by Jeremiah Gowdy

  I have developed middleware that provides RPC functionality to multiple client applications on multiple platforms within our organization. The middleware is written in C# and runs as a Windows NT Service. It handles things like file access to network shares, database access, etc. The middleware is hosted on two high end systems running Windows Server 2008 R2. When one of our server administrators goes to reboot the machine, primarily to do Windows Updates, there are serious problems with how the system behaves in regards to my NT Service. My service is designed to immediately stop listening for new connections, immediately start refusing new requests on existing connections, and otherwise shut down as rapidly as possible in the case of an OnStop or OnShutdown request from the SCM. Still, to maintain system integrity, operations that are currently in progress are allowed to continue for a reasonable time. Usually the server shuts down inside of 30 seconds (when the service is manually stopped for example). However, when the system is instructed to restart, my service immediately loses access to network drives and UNC paths, causing data integrity problems for any open files and partial writes to those locations. My service does list Workstation (and thus SMB Redirector) as a dependency, so I would think that my service would need to be stopped prior to Workstation/Redirector being stopped if Windows were honoring those dependencies. Basically, my application is forced to crash and burn, failing remote procedure calls and eventually being forced to terminate by the operating system after a timeout period has elapsed (seems to be on the order of 20-30 seconds). Unlike a Windows application, my Windows NT Service doesn't seem to have any power to stop a system shutdown in progress, delay the system shutdown, or even just the opportunity to save out any pending network share disk writes before being forcibly disconnected and shutdown. How is an NT Service developer supposed to have any kind of application integrity in this environment? Why is it that Forms Applications get all of the opportunity to finish their business prior to shutdown, while services seem to get no such benefits? I have tried: Calling SetProcessShutdownParameters via p/invoke to try to notify my application of the shutdown sooner to avoid Redirector shutting down before I do. Calling ServiceBase.RequestAdditionalTime with a value less than or equal to the two minute limit. Tweaking the WaitToKillServiceTimeout Everything I can think of to make my service shutdown faster. But in the end, I still get ~30 seconds of problematic time in which my service doesn't even seem to have been notified of an OnShutdown event yet, but requests are failing due to redirector no longer servicing my network share requests. How is this issue meant to be resolved? What can I do to delay or stop the shutdown, or at least be allowed to shut down my active tasks without Redirector services disappearing out from under me? I can understand what Microsoft is trying to do to prevent services from dragging their feet and showing shutdowns, but that seems like a great goal for Windows client operating systems, not for servers. I don't want my servers to shutdown fast, I want operational integrity and graceful shutdowns. Thanks in advance for any help you can provide. PS in regards to writing my own middleware, this is for a telephony application with sub-second "soft-realtime" response time requirements. It does make sense, and it's not a point I'm looking to debate. :)

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• Partial generic type inference possible in C#?

  - by Lasse V. Karlsen

  I am working on rewriting my fluent interface for my IoC class library, and when I refactored some code in order to share some common functionality through a base class, I hit upon a snag. Note: This is something I want to do, not something I have to do. If I have to make do with a different syntax, I will, but if anyone has an idea on how to make my code compile the way I want it, it would be most welcome. I want some extension methods to be available for a specific base-class, and these methods should be generic, with one generic type, related to an argument to the method, but the methods should also return a specific type related to the particular descendant they're invoked upon. Better with a code example than the above description methinks. Here's a simple and complete example of what doesn't work: using System; namespace ConsoleApplication16 { public class ParameterizedRegistrationBase { } public class ConcreteTypeRegistration : ParameterizedRegistrationBase { public void SomethingConcrete() { } } public class DelegateRegistration : ParameterizedRegistrationBase { public void SomethingDelegated() { } } public static class Extensions { public static ParameterizedRegistrationBase Parameter<T>( this ParameterizedRegistrationBase p, string name, T value) { return p; } } class Program { static void Main(string[] args) { ConcreteTypeRegistration ct = new ConcreteTypeRegistration(); ct .Parameter<int>("age", 20) .SomethingConcrete(); // <-- this is not available DelegateRegistration del = new DelegateRegistration(); del .Parameter<int>("age", 20) .SomethingDelegated(); // <-- neither is this } } } If you compile this, you'll get: 'ConsoleApplication16.ParameterizedRegistrationBase' does not contain a definition for 'SomethingConcrete' and no extension method 'SomethingConcrete'... 'ConsoleApplication16.ParameterizedRegistrationBase' does not contain a definition for 'SomethingDelegated' and no extension method 'SomethingDelegated'... What I want is for the extension method (Parameter<T>) to be able to be invoked on both ConcreteTypeRegistration and DelegateRegistration, and in both cases the return type should match the type the extension was invoked on. The problem is as follows: I would like to write: ct.Parameter<string>("name", "Lasse") ^------^ notice only one generic argument but also that Parameter<T> returns an object of the same type it was invoked on, which means: ct.Parameter<string>("name", "Lasse").SomethingConcrete(); ^ ^-------+-------^ | | +---------------------------------------------+ .SomethingConcrete comes from the object in "ct" which in this case is of type ConcreteTypeRegistration Is there any way I can trick the compiler into making this leap for me? If I add two generic type arguments to the Parameter method, type inference forces me to either provide both, or none, which means this: public static TReg Parameter<TReg, T>( this TReg p, string name, T value) where TReg : ParameterizedRegistrationBase gives me this: Using the generic method 'ConsoleApplication16.Extensions.Parameter<TReg,T>(TReg, string, T)' requires 2 type arguments Using the generic method 'ConsoleApplication16.Extensions.Parameter<TReg,T>(TReg, string, T)' requires 2 type arguments Which is just as bad. I can easily restructure the classes, or even make the methods non-extension-methods by introducing them into the hierarchy, but my question is if I can avoid having to duplicate the methods for the two descendants, and in some way declare them only once, for the base class. Let me rephrase that. Is there a way to change the classes in the first code example above, so that the syntax in the Main-method can be kept, without duplicating the methods in question? The code will have to be compatible with both C# 3.0 and 4.0. Edit: The reason I'd rather not leave both generic type arguments to inference is that for some services, I want to specify a parameter value for a constructor parameter that is of one type, but pass in a value that is a descendant. For the moment, matching of specified argument values and the correct constructor to call is done using both the name and the type of the argument. Let me give an example: ServiceContainerBuilder.Register<ISomeService>(r => r .From(f => f.ConcreteType<FileService>(ct => ct .Parameter<Stream>("source", new FileStream(...))))); ^--+---^ ^---+----^ | | | +- has to be a descendant of Stream | +- has to match constructor of FileService If I leave both to type inference, the parameter type will be FileStream, not Stream.

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• Qt, MSVC, and /Zc:wchar_t- == I want to blow up the world

  - by Noah Roberts

  So Qt is compiled with /Zc:wchar_t- on windows. What this means is that instead of wchar_t being a typedef for some internal type (__wchar_t I think) it becomes a typedef for unsigned short. The really cool thing about this is that the default for MSVC is the opposite, which of course means that the libraries you're using are likely compiled with wchar_t being a different type than Qt's wchar_t. This doesn't become an issue of course until you try to use something like std::wstring in your code; especially when one or more libraries have functions that accept it as parameters. What effectively happens is that your code happily compiles but then fails to link because it's looking for definitions using std::wstring<unsigned short...> but they only contain definitions expecting std::wstring<__wchar_t...> (or whatever). So I did some web searching and ran into this link: http://bugreports.qt.nokia.com/browse/QTBUG-6345 Based on the statement by Thiago Macieira, "Sorry, we will not support building Qt like this," I've been worried that fixing Qt to work like everything else might cause some problem and have been trying to avoid it. We recompiled all of our support libraries with the /Zc:wchar_t- flag and have been fairly content with that until a couple days ago when we started trying to port over (we're in the process of switching from Wx to Qt) some serialization code. Because of how win32 works, and because Wx just wraps win32, we've been using std::wstring to represent string data with the intent of making our product as i18n ready as possible. We did some testing and Wx did not work with multibyte characters when trying to print special stuff (even not so special stuff like the degree symbol was an issue). I'm not so sure that Qt has this problem since QString isn't just a wrapper to the underlying _TCHAR type but is a Unicode monster of some sort. At any rate, the serialization library in boost has compiled parts. We've attempted to recompile boost with /Zc:wchar_t- but so far our attempts to tell bjam to do this have gone unheeded. We're at an impasse. From where I'm sitting I have three options: Recompile Qt and hope it works with /Zc:wchar_t. There's some evidence around the web that others have done this but I have no way of predicting what will happen. All attempts to ask Qt people on forums and such have gone unanswered. Hell, even in that very bug report someone asks why and it just sat there for a year. Keep fighting with bjam until it listens. Right now I've got someone under me doing that and I have more experience fighting with things to get what I want but I do have to admit to getting rather tired of it. I'm also concerned that I'll KEEP running into this issue just because Qt wants to be a c**t. Stop using wchar_t for anything. Unfortunately my i18n experience is pretty much 0 but it seems to me that I just need to find the right to/from function in QString (it has a BUNCH) to encode the Unicode into 8-bytes and visa-versa. UTF8 functions look promising but I really want to be sure that no data will be lost if someone from Zimbabfuckegypt starts writing in their own language and the documentation in QString frightens me a little into thinking that could happen. Of course, I could always run into some library that insists I use wchar_t and then I'm back to 1 or 2 but I rather doubt that would happen. So, what's my question... Which of these options is my best bet? Is Qt going to eventually cause me to gouge out my own eyes because I decided to compile it with /Zc:wchar_t anyway? What's the magic incantation to get boost to build with /Zc:wchar_t- and will THAT cause permanent mental damage? Can I get away with just using the standard 8-bit (well, 'common' anyway) character classes and be i18n compliant/ready? How do other Qt developers deal with this mess?

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• How to create a HTML5 + SVG document using the PHP XSLTProcessor

  - by Kau-Boy

  For a little project about XML I try to use HTML5 as it has SVG and WAI-ARIA Support. I also want to use a XSL stylesheet for my document. But I can't get a valid HTML5 document with a nested SVG. Here are some version I tested so far: <?xml version="1.0" encoding="UTF-8"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:output indent="yes" method="xml"/> <xsl:template match="/"> <html xmlns="http://www.w3.org/1999/xhtml"> // content with the svg tag in the body </html> </xsl:template> </xsl:stylesheet> In combination with header('Content-Type: application/xml'); it works and produces this HTML output: <?xml version="1.0"?> <html xmlns="http://www.w3.org/1999/xhtml"> // content with the svg tag in the body </html> But it is not HTML5 and without a DOCTYPE I get a lot of errors on the W3 validator. So trying to get a HTML5 document I used the following XSL: <?xml version="1.0" encoding="UTF-8"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:output indent="yes" method="html"/> <xsl:template match="/"> <xsl:text disable-output-escaping='yes'>&lt;!DOCTYPE HTML></xsl:text> <html> // content with the svg tag in the body </html> </xsl:template> </xsl:stylesheet> But unfortunately that will produce thze following HTML output: <!DOCTYPE HTML> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> .... </head> // content with the svg tag in the body </html> As you can see it's regular HTML5 but using it in combination with header('Content-Type: application/xml'); it fails because of the missing slash at the end of the meta tag (which was automatically created). Using header('Content-Type: image/xhtml+svg'); or header('Content-Type: text/html'); there is no XML parsing error, but the page will not show the SVG as a graph but as text (without the tags). Can anyone tell me how to avoid the meta tag to be inserted or how to set a propper Content-Type that will make the browser rendern the SVG. Or even any other hint to get this working. I would really like to keep HTML5 to be able to keep the WAI-ARIA Landmark Roles an the HTML5 tags like NAV and FOOTER.

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