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  • Binder and variadic template ends up in a segmentation fault

    - by phlipsy
    I wrote the following program #include <iostream> template<typename C, typename Res, typename... Args> class bind_class_t { private: Res (C::*f)(Args...); C *c; public: bind_class_t(Res (C::*f)(Args...), C* c) : f(f), c(c) { } Res operator() (Args... args) { return (c->*f)(args...); } }; template<typename C, typename Res, typename... Args> bind_class_t<C, Res, Args...> bind_class(Res (C::*f)(Args...), C* c) { return bind_class<C, Res, Args...>(f, c); } class test { public: int add(int x, int y) { return x + y; } }; int main() { test t; // bind_class_t<test, int, int, int> b(&test::add, &t); bind_class_t<test, int, int, int> b = bind_class(&test::add, &t); std::cout << b(1, 2) << std::endl; return 0; } compiled it with gcc 4.3.3 and got a segmentation fault. After spending some time with gdb and this program it seems to me that the addresses of the function and the class are mixed up and a call of the data address of the class isn't allowed. Moreover if I use the commented line instead everything works fine. Can anyone else reproduce this behavior and/or explain me what's going wrong here?

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  • How to get max of composite data in SQL?

    - by Siddharth Sinha
    SELECT "Name""Month","Year","Value" from Table WHERE "Name" LIKE '%JERRY%' AND "Year" = (SELECT MAX("Year") FROM Table where "Name" LIKE '%JERRY%') AND "Month"= (SELECT MAX("Month") FROM Table where "Name" LIKE '%JERRY%' AND "Year"= (SELECT MAX("Year") FROM Table where "Name" LIKE '%JERRY%')) Table -- Name | Year | Month | Value ----------------------------- JERRY 2012 9 100 JERRY 2012 9 120 JERRY 2012 9 130 JERRY 2012 8 20 JERRY 2011 12 50 So i want the first three rows as output. As for the latest month for the latest year i need all the values. Can someone suggest a better cleaner query?

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  • How do I utilize REST to post GPS data from an Android device into a Ruby on Rails application?

    - by joecan
    I am a student in the process a building an Android app that can post a GPS track into a Rails application. I would like to do things the "Rails" way and take advantage of the REST. My rails application basically has 3 models at this point: users, tracks, and points. A user has_many tracks and a track has_many points. A track also has a total distance. Points have a latitude and longitude. I have successfully been able to create an empty track with: curl -i -X POST -H 'Content-Type: application/xml' -d '<track><distance>100</distance></track>' http://localhost:3000/users/1/tracks Whoo hoo! That is pretty cool. I am really impressed that rails do this. Just to see what would happen I tried the following: curl -i -X POST -H 'Content-Type: application/xml -d '<track><distance>100</distance><points><point><lat>3</lat><lng>2</lng></point></points></track>' http://localhost:3000/users/1/tracks Fail! The server spits back: Processing TracksController#create (for 127.0.0.1 at 2010-04-14 00:03:25) [POST] Parameters: {"track"={"points"={"point"={"lng"="2", "lat"="3"}}, "distance"="100"}, "user_id"="1"} User Load (0.6ms) SELECT * FROM "users" WHERE ("users"."id" = 1) ActiveRecord::AssociationTypeMismatch (Point(#-620976268) expected, got Array(#-607740138)): app/controllers/tracks_controller.rb:47:in `create' It seems my tracks_controller doesn't like or understand what it's getting from the params object in my tracks_controller.rb: def create @track = @user.tracks.build(params[:track]) My xml might be wrong, but at least Rails seems to be expecting a Point from it. Is there anyway I can fix TracksController.create so that it will be able to parse xml of a track with nested multiple points? Or is there another way I should be doing this entirely?

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  • How to save data between calls to a IHttpHandler?

    - by bartek
    I have a IHttpHandler that acts as a source to a jQuery Autocomplete input field. In the constructor of the handler I generate an index that remains fairly static between request (needs to be rebuilt maybe once a day). How can I cache the the index between calls? Debugging indicates that the constructor is called for each request. I've set IsReusable to "false".

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  • How best to implement "favourites" feature? (like favourite products on a data driven website)

    - by ClarkeyBoy
    Hi, I have written a dynamic database driven, object oriented website with an administration frontend etc etc. I would like to add a feature where customers can save items as "favourites", without having to create an account and login, to come back to them later, but I dont know how exactly to go about doing this... I see three options: Log favourites based on IP address and then change these to be logged against an account if the customer then creates an account; Force customers to create an account to be able to use this functionality; Log favourites based on IP address but give users the option to save their favourites under a name they specify. The problem with option 1 is that I dont know much about IP addresses - my Dad thinks they are unique, but I know people have had problems with systems like this. The problem with 1 and 2 is that accounts have not been opened up to customers yet - only administrators can log in at the moment. It should be easy to alter this (no more than a morning or afternoons work) but I would also have to implement usergroups too. The problem with option 3 is that if user A saves a favourites list called "My Favourites", and then user B tries to save a list under this name and it is refused, user B will then be able to access the list saved by user A because they now know it already exists. A solution to this is to password protect lists, but to go to all this effort I may as well implement option 2. Of course I could always use option 4; use an alternative if anyone can suggest a better solution than any of the above options. So has anyone ever done something like this before? If so how did you go about it? What do you recommend (or not recommend)? Many thanks in advance, Regards, Richard

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  • Temporary non-const istream reference in constructor (C++)

    - by Christopher Bruns
    It seems that a constructor that takes a non-const reference to an istream cannot be constructed with a temporary value in C++. #include <iostream> #include <sstream> using namespace std; class Bar { public: explicit Bar(std::istream& is) {} }; int main() { istringstream stream1("bar1"); Bar bar1(stream1); // OK on all platforms // compile error on linux, Mac gcc; OK on Windows MSVC Bar bar2(istringstream("bar2")); return 0; } This compiles fine with MSVC, but not with gcc. Using gcc I get a compile error: g++ test.cpp -o test test.cpp: In function ‘int main()’: test.cpp:18: error: no matching function for call to ‘Bar::Bar(std::istringstream)’ test.cpp:9: note: candidates are: Bar::Bar(std::istream&) test.cpp:7: note: Bar::Bar(const Bar&) Is there something philosophically wrong with the second way (bar2) of constructing a Bar object? It looks nicer to me, and does not require that stream1 variable that is only needed for a moment.

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  • explicit template instantiations

    - by user323422
    see following code and please clear doubts1. as ABC is template why it not showing error when we put defination of ABC class member function in test.cpp 2.if i put test.cpp code in test.h and remve 2 , then it working fine. // test.h template <typename T> class ABC { public: void foo( T& ); void bar( T& ); }; // test.cpp template <typename T> void ABC<T>::foo( T& ) {} // definition template <typename T> void ABC<T>::bar( T& ) {} // definition template void ABC<char>::foo( char & ); // 1 template class ABC<char>; // 2 // main.cpp #include "test.h" int main() { ABC<char> a; a.foo(); // valid with 1 or 2 a.bar(); // link error if only 1, valid with 2 }

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  • How can i add list data in my object?

    - by Phsika
    Below codes run perfectly but i want to re generate simply static void YeniMethodListele() { Calisan calisan = new Calisan(){ ID=1, Ad="yusuf", SoyAd="karatoprak"}; List<Calisan> myList = new List<Calisan>(); myList.Add(calisan); MyCalisan myCalisan = new MyCalisan() { list = myList }; //myCalisan.list.Add(calisan); foreach (Calisan item in myCalisan.list) { Console.WriteLine(item.Ad.ToString()); } } } public class Calisan { public int ID { get; set; } public string Ad { get; set; } public string SoyAd { get; set; } } public class MyCalisan { public List<Calisan> list { get; set; } public MyCalisan() { list = new List<Calisan>(); } } static void YeniMethodListele() { Calisan calisan = new Calisan(){ ID=1, Ad="yusuf", SoyAd="karatoprak"}; MyCalisan myCalisan = new MyCalisan(); myCalisan.list.Add(calisan); foreach (Calisan item in myCalisan.list) { Console.WriteLine(item.Ad.ToString()); } } } public class Calisan { public int ID { get; set; } public string Ad { get; set; } public string SoyAd { get; set; } } public class MyCalisan { public List<Calisan> list { get; set; } public MyCalisan() { list = new List<Calisan>(); } }

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  • Strings exported from a module have changed line breaks

    - by Jesse Millikan
    In a DrScheme project, I'm using a MrEd editor-canvas% with text% and inserting a string from a literal in a Scheme file. This results in an extra blank line in the editor for each line of text I'm trying to insert. I've tracked this down to the apparent fact that string literals from outside modules are getting extra line breaks. Here's a full example. The editor is irrelevant at this point, but it displays the result. ; test-literals.ss (module test-literals scheme (provide (all-defined-out)) (define exported-string "From another module with some more line breaks. ")) ; editor-test.ss (module editor-test scheme (require mred "test-literals.ss") (define w (instantiate frame% ("Editor Test" #f) )) (define c (instantiate editor-canvas% (w) (line-count 12) (min-width 400))) (define editor (instantiate text% ())) (send c set-editor editor) (send w show #t) (send editor erase) (send editor insert "Some text with some line breaks. ") (send editor insert exported-string)) And the result in the editor is Some text with some line breaks. From another module with some more line breaks. I've traced in and figured out that it's changing Unix line breaks to Windows line breaks when strings are imported from another module, but these display as double line breaks. Why is this happening and is there a way to stop it other than changing every imported string?

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  • ack: Excluding only one directory but keeping all others with the same name

    - by mattalexx
    My folder structure looks like this: /app /app/data ... /app/secondary /app/secondary/data I want to recursively search /app, including /app/data. I do not want to search /app/secondary/data however. This what I have so far: ack --ignore-dir=data searchtext ack --ignore-dir=secondary/data searchtext The first command is ignoring both directories and the second one is ignoring neither of them. From within the app folder, what should my ack command look like?

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  • Undefined variable error when parsing json

    - by Ben Shelock
    I'm trying to parse the json grabbed from here. Basically what I do is iterate over the items, sort them, then display them. But I get an error saying data.data.children[i] is undefined. I can't think why it's doing it though? var json = 'http://www.reddit.com/reddits/mine/.json'; GM_xmlhttpRequest({ method: "GET", url: json, onload: reddits }); function reddits(response){ var txt = response.responseText; var data; var suggested = document.getElementById('suggested-reddits'); if(window.JSON && JSON.parse){ data = JSON.parse(txt); } else{ data = eval("("+txt+")"); } suggested.innerHTML += '<span>reddits you\'re subscribed to </span> <ul id="rsub"></ul>'; GM_addStyle('#rsub{width: 500px;}'); var reddits = new Array(); var rsub = document.getElementById('rsub'); for(i = 0; i <= data.data.children.length; i++){ var r = data.data.children[i].data.display_name; reddits.push(r); } sort(reddits); for(i = 0; i <= reddits.length; i++){ rsub.innerHTML += '<li><a href="#" onclick="set_sr_name(this); return false">' + reddits[i] + '</a></li>'; } }

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  • how to extend wpf combo box to bind data?

    - by Shaihan
    i need to bind a collection of objects to a combo box which i can use in different forms. so i want create a custom control which binds the collection to the combo box? how t do it by extending combo box? also how can i define the ItemData template?

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  • i have made a from and want to connect it to a oracle 10g data base using php.can you please assume

    - by nachiket-panse
    http://www.freecsstemplates.org Released for free under a Creative Commons Attribution 2.5 License -- Sitename.com by Free Css Templates MANAGEMEINT INFORMATION SYSTEM   <p class="style2">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;REGISTRY ENTRY FORM </p> <form id="form2" method="post" action=""> <p align="center">&nbsp;</p> <p align="center"><span class="style3">JOB DESCRIPTION :</span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <textarea name="textarea"></textarea> </p> <p align="center"><span class="style3">QUANTITY :</span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <input type="text" name="textfield5" /> </p> <p align="center">&nbsp;<span class="style3">CONTACT PERSON </span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <input type="text" name="textfield3" /> </p> <p align="center">&nbsp;</p> <p align="center"><span class="style3">DIVISION CODE: <textarea name="textarea3"></textarea> </span></p> <p align="center"><span class="style3">ACCEPTANCE DATE </span>: <input type="text" name="textfield4" /> </p> <p align="center"><span class="style3">REFERENCE NUMBER :</span> <input type="text" name="textfield2" /> </p> <p align="center"><span class="style3">CLASSIFICATION :</span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <input type="text" name="textfield" /></p> <p align="center">&nbsp;</p> <p align="center"><span class="style3">CUMULATIVE COST: </span> <select name="select"> </select> </p> <p align="center"><span class="style3">PLANNING ENGR: </span> <textarea name="textarea2"></textarea> </p> <p align="center"><span class="style3">PLANNING: </span> <input type="text" name="textfield6" /> </p> <p align="center"> <span class="style3">FILL THE COMPLETION DATE: </span> <input type="text" name="textfield7" /> </p> <p align="center"><span class="style3">REMARKS: </span> <input type="text" name="textfield8" /> </p> <p align="center">&nbsp;</p> <p align="center"> <input type="submit" name="SAVE" value="SAVE" /> <input type="submit" name="Submit2" value="LIST" /> <input type="submit" name="Submit" value="ADD" /> <input type="submit" name="Submit3" value="CANCEL" /> <input type="submit" name="BACK" value="BACK" /></p> <p align="center">&nbsp;</p> <p align="center">&nbsp;</p> <p align="center">&nbsp;</p> <p align="center">&nbsp;</p> <p align="center">&nbsp;</p> </form> <p align="center" class="style2">&nbsp;</p>

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  • How much user data should be required to grant a password reset?

    - by Andrew Heath
    I'm looking to add password-reset functionality to my site and have been browsing the numerous threads discussing various aspects of that issue here on SO. One thing I haven't really seen clarified is how much information to require from the user for confirmation before sending out the reset email. is email alone enough? email + account username? email + account username + some other identifying value all accounts must input? I don't want my site to seem like an old wrinkly nun with a ruler, but I don't want people to be able to abuse the password reset system willy-nilly. Suggestions?

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  • How Can I Populate Default Form Data with a ManyToMany Field?

    - by b14ck
    Ok, I've been crawling google and Django documentation for over 2 hours now (as well as the IRC channel on freenode), and haven't been able to figure this one out. Basically, I have a model called Room, which is displayed below: class Room(models.Model): """ A `Partyline` room. Rooms on the `Partyline`s are like mini-chatrooms. Each room has a variable amount of `Caller`s, and usually a moderator of some sort. Each `Partyline` has many rooms, and it is common for `Caller`s to join multiple rooms over the duration of their call. """ LIVE = 0 PRIVATE = 1 ONE_ON_ONE = 2 UNCENSORED = 3 BULLETIN_BOARD = 4 CHILL = 5 PHONE_BOOTH = 6 TYPE_CHOICES = ( ('LR', 'Live Room'), ('PR', 'Private Room'), ('UR', 'Uncensored Room'), ) type = models.CharField('Room Type', max_length=2, choices=TYPE_CHOICES) number = models.IntegerField('Room Number') partyline = models.ForeignKey(Partyline) owner = models.ForeignKey(User, blank=True, null=True) bans = models.ManyToManyField(Caller, blank=True, null=True) def __unicode__(self): return "%s - %s %d" % (self.partyline.name, self.type, self.number) I've also got a forms.py which has the following ModelForm to represent my Room model: from django.forms import ModelForm from partyline_portal.rooms.models import Room class RoomForm(ModelForm): class Meta: model = Room I'm creating a view which allows administrators to edit a given Room object. Here's my view (so far): def edit_room(request, id=None): """ Edit various attributes of a specific `Room`. Room owners do not have access to this page. They cannot edit the attributes of the `Room`(s) that they control. """ room = get_object_or_404(Room, id=id) if not room.is_owner(request.user): return HttpResponseForbidden('Forbidden.') if is_user_type(request.user, ['admin']): form_type = RoomForm elif is_user_type(request.user, ['lm']): form_type = LineManagerEditRoomForm elif is_user_type(request.user, ['lo']): form_type = LineOwnerEditRoomForm if request.method == 'POST': form = form_type(request.POST, instance=room) if form.is_valid(): if 'owner' in form.cleaned_data: room.owner = form.cleaned_data['owner'] room.save() else: defaults = {'type': room.type, 'number': room.number, 'partyline': room.partyline.id} if room.owner: defaults['owner'] = room.owner.id if room.bans: defaults['bans'] = room.bans.all() ### this does not work properly! form = form_type(defaults, instance=room) variables = RequestContext(request, {'form': form, 'room': room}) return render_to_response('portal/rooms/edit.html', variables) Now, this view works fine when I view the page. It shows all of the form attributes, and all of the default values are filled in (when users do a GET)... EXCEPT for the default values for the ManyToMany field 'bans'. Basically, if an admins clicks on a Room object to edit, the page they go to will show all of the Rooms default values except for the 'bans'. No matter what I do, I can't find a way to get Django to display the currently 'banned users' for the Room object. Here is the line of code that needs to be changed (from the view): defaults = {'type': room.type, 'number': room.number, 'partyline': room.partyline.id} if room.owner: defaults['owner'] = room.owner.id if room.bans: defaults['bans'] = room.bans.all() ### this does not work properly! There must be some other syntax I have to use to specify the default value for the 'bans' field. I've really been pulling my hair out on this one, and would definitely appreciate some help. Thanks!

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  • Deleting a resource in a Cucumber (Capybara) step doesn't work

    - by Josiah Kiehl
    Here is my Scenario: Scenario: Delete a match Given pojo is logged in And there is a match with the following: | game_id | 1 | | name | Game del Pojo | | date_and_time | 2010-02-23 17:52:00 | | players | 2 | | teams | 2 | | comment | This is an awesome comment | | user_id | 1 | And I am on the show match 1 page And show me the page When I follow "Delete" And I follow "Yes, delete it" Then there should not be a match with the following: | game_id | 1 | | name | Game del Pojo | | date_and_time | 2010-02-23 17:52:00 | | players | 2 | | teams | 2 | | comment | This is an awesome comment | | user_id | 1 | If I walk through these steps manually, they work. When I click the confirmation: Yes, delete it, then the match is deleted. Cucumber, however, fails to delete the record and the last step fails. And I follow "Yes, delete it" # features/step_definitions/web_steps.rb:32 Then there should not be a match with the following: # features/step_definitions/match_steps.rb:8 | game_id | 1 | | name | Game del Pojo | | date_and_time | 2010-02-23 17:52:00 | | players | 2 | | teams | 2 | | comment | This is an awesome comment | | user_id | 1 | <nil> expected but was <#<Match id: 1, name: "Game del Pojo", date_and_time: "2010-02-23 17:52:00", teams: 2, created_at: "2010-03-02 23:06:33", updated_at: "2010-03-02 23:06:33", comment: "This is an awesome comment", players: 2, game_id: 1, user_id: 1>>. (Test::Unit::AssertionFailedError) /usr/lib/ruby/1.8/test/unit/assertions.rb:48:in `assert_block' /usr/lib/ruby/1.8/test/unit/assertions.rb:495:in `_wrap_assertion' /usr/lib/ruby/1.8/test/unit/assertions.rb:46:in `assert_block' /usr/lib/ruby/1.8/test/unit/assertions.rb:83:in `assert_equal' /usr/lib/ruby/1.8/test/unit/assertions.rb:172:in `assert_nil' ./features/step_definitions/match_steps.rb:22:in `/^there should (not)? be a match with the following:$/' features/matches.feature:124:in `Then there should not be a match with the following:' Any clue how to debug this? Thanks!

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  • Windows Mobile : How to bind dropdown's selectedvalue to a column in table A and the list data to a

    - by Rob
    Hi, I am trying to learn the basics of Windows Mobile development against SQL CE and have come across a basic problem. I have two tables. One called Customers that stores customer info and has an identity column called ID as the primary key. The other table is called Orders which has a column called CustomerID (the FK constraint is present). I have added a DataSet to the project that contains both tables and have autogenerated the edit/view forms. This has produced a text control for the CustomerID column in the Order table for the new/edit form and I deleted it and replaced it with a dropdown list. Then, using the 'Advanced' databinding options (in Properties) I set the datasource of the list to the Customers table setting the value to the ID field and the text to the CustomerName field. I then set the SelectedValue of the list box to the CustomerID field of the Orders dataset. So far so good. When I run the app in the emulator and view the 'New' form for Orders the Customer dropdown is indeed populated with a list of customer names and I can select one and happily create a new order successfully. This is confirmed when I see the order appear in the Orders Grid form. However, when I then click on the order in the grid and then select 'Edit' the order loads but the dropdown always shows the first customer in the list and doesn't seem to bind the SelectedValue to the Orders dataset CustomerID field. Now I am an ASP.NET guy and normally hand craft the DAL and it's binding to the UI so I'm not entirely sure where to look to investigate what is going wrong here as this is all generated code. I am sure it is something very trivial but any pointers would be appreciated. My gut feeling is that the SelectedValue and the Customers.CustomerID values do not match for some reason? Many thanks, Rob.

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  • Implementing a robust async stream reader for a console

    - by Jon
    I recently provided an answer to this question: C# - Realtime console output redirection. As often happens, explaining stuff (here "stuff" was how I tackled a similar problem) leads you to greater understanding and/or, as is the case here, "oops" moments. I realized that my solution, as implemented, has a bug. The bug has little practical importance, but it has an extremely large importance to me as a developer: I can't rest easy knowing that my code has the potential to blow up. Squashing the bug is the purpose of this question. I apologize for the long intro, so let's get dirty. I wanted to build a class that allows me to receive input from a Stream in an event-based manner. The stream, in my scenario, is guaranteed to be a FileStream and there is also an associated StreamReader already present to leverage. The public interface of the class is this: public class MyStreamManager { public event EventHandler<ConsoleOutputReadEventArgs> StandardOutputRead; public void StartSendingEvents(); public void StopSendingEvents(); } Obviously this specific scenario has to do with a console's standard output. StartSendingEvents and StopSendingEvents do what they advertise; for the purposes of this discussion, we can assume that events are always being sent without loss of generality. The class uses these two fields internally: protected readonly StringBuilder inputAccumulator = new StringBuilder(); protected readonly byte[] buffer = new byte[256]; The functionality of the class is implemented in the methods below. To get the ball rolling: public void StartSendingEvents(); { this.stopAutomation = false; this.BeginReadAsync(); } To read data out of the Stream without blocking, and also without requiring a carriage return char, BeginRead is called: protected void BeginReadAsync() { if (!this.stopAutomation) { this.StandardOutput.BaseStream.BeginRead( this.buffer, 0, this.buffer.Length, this.ReadHappened, null); } } The challenging part: BeginRead requires using a buffer. This means that when reading from the stream, it is possible that the bytes available to read ("incoming chunk") are larger than the buffer. Since we are only handing off data from the stream to a consumer, and that consumer may well have inside knowledge about the size and/or format of these chunks, I want to call event subscribers exactly once for each chunk. Otherwise the abstraction breaks down and the subscribers have to buffer the incoming data and reconstruct the chunks themselves using said knowledge. This is much less convenient to the calling code, and detracts from the usefulness of my class. Edit: There are comments below correctly stating that since the data is coming from a stream, there is absolutely nothing that the receiver can infer about the structure of the data unless it is fully prepared to parse it. What I am trying to do here is leverage the "flush the output" "structure" that the owner of the console imparts while writing on it. I am prepared to assume (better: allow my caller to have the option to assume) that the OS will pass me the data written between two flushes of the stream in exactly one piece. To this end, if the buffer is full after EndRead, we don't send its contents to subscribers immediately but instead append them to a StringBuilder. The contents of the StringBuilder are only sent back whenever there is no more to read from the stream (thus preserving the chunks). private void ReadHappened(IAsyncResult asyncResult) { var bytesRead = this.StandardOutput.BaseStream.EndRead(asyncResult); if (bytesRead == 0) { this.OnAutomationStopped(); return; } var input = this.StandardOutput.CurrentEncoding.GetString( this.buffer, 0, bytesRead); this.inputAccumulator.Append(input); if (bytesRead < this.buffer.Length) { this.OnInputRead(); // only send back if we 're sure we got it all } this.BeginReadAsync(); // continue "looping" with BeginRead } After any read which is not enough to fill the buffer, all accumulated data is sent to the subscribers: private void OnInputRead() { var handler = this.StandardOutputRead; if (handler == null) { return; } handler(this, new ConsoleOutputReadEventArgs(this.inputAccumulator.ToString())); this.inputAccumulator.Clear(); } (I know that as long as there are no subscribers the data gets accumulated forever. This is a deliberate decision). The good This scheme works almost perfectly: Async functionality without spawning any threads Very convenient to the calling code (just subscribe to an event) Maintains the "chunkiness" of the data; this allows the calling code to use inside knowledge of the data without doing any extra work Is almost agnostic to the buffer size (it will work correctly with any size buffer irrespective of the data being read) The bad That last almost is a very big one. Consider what happens when there is an incoming chunk with length exactly equal to the size of the buffer. The chunk will be read and buffered, but the event will not be triggered. This will be followed up by a BeginRead that expects to find more data belonging to the current chunk in order to send it back all in one piece, but... there will be no more data in the stream. In fact, as long as data is put into the stream in chunks with length exactly equal to the buffer size, the data will be buffered and the event will never be triggered. This scenario may be highly unlikely to occur in practice, especially since we can pick any number for the buffer size, but the problem is there. Solution? Unfortunately, after checking the available methods on FileStream and StreamReader, I can't find anything which lets me peek into the stream while also allowing async methods to be used on it. One "solution" would be to have a thread wait on a ManualResetEvent after the "buffer filled" condition is detected. If the event is not signaled (by the async callback) in a small amount of time, then more data from the stream will not be forthcoming and the data accumulated so far should be sent to subscribers. However, this introduces the need for another thread, requires thread synchronization, and is plain inelegant. Specifying a timeout for BeginRead would also suffice (call back into my code every now and then so I can check if there's data to be sent back; most of the time there will not be anything to do, so I expect the performance hit to be negligible). But it looks like timeouts are not supported in FileStream. Since I imagine that async calls with timeouts are an option in bare Win32, another approach might be to PInvoke the hell out of the problem. But this is also undesirable as it will introduce complexity and simply be a pain to code. Is there an elegant way to get around the problem? Thanks for being patient enough to read all of this.

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  • How can I tell groovy/grails not to try to "re-encode" binary data? (Revised title)

    - by ?????
    I have a groovy/grails application that needs to serve images It works fine on my dev box, the image is returned properly. Here's the start of the returned JPEG, as seen by od -cx 0000000 377 330 377 340 \0 020 J F I F \0 001 001 001 001 , d8ff e0ff 1000 464a 4649 0100 0101 2c01 but on the production box, there's some garbage in front, and the d8ff e0ff before the 1000 is missing 0000000 ? ** ** ? ** ** ? ** ** ? ** ** \0 020 J F bfef efbd bdbf bfef efbd bdbf 1000 464a 0000020 I F \0 001 001 001 \0 H \0 H \0 \0 ? ** ** ? 4649 0100 0101 4800 4800 0000 bfef efbd It's the exact same code. I just moved the .war over and run it on a different machine. (Isn't Java supposed to be write once, run everywhere?) Any ideas? An "encoding" problem? The code is sent to the response like this: response.contentType = "image/jpeg"; response.outputStream << out; Here's the code that locates the image on an internal application server and re-serves the image. I've pared down the code a bit to remove the error handling, etc, to make it easier to read. def show = { def address = "http://internal.application.server:9899/img?photoid=${params.id}" def out = new ByteArrayOutputStream() out << new URL(address).openStream() response.contentLength = out.size(); // XXX If you don't do this hack, "head" requests won't work! if (request.method == 'HEAD') { render( text : "", contentType : "image/jpeg" ); } else { response.contentType = "image/jpeg"; response.outputStream << out; } } Update: I tried setting the CharacterEncoding response.setCharacterEncoding("ISO-8859-1"); if (request.method == 'HEAD') { render( text : "", contentType : "image/jpeg" ); } else { response.contentType = "image/jpeg;charset=ISO-8859-1"; response.outputStream << out; } but it made no difference in the output. On my production machine, the binary bytes in the image are re-encoded/escaped as if they were UTF-8 (see Michael's explanation below). It works fine on my development machine.

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  • Appending facts into an existing prolog file.

    - by vuj
    Hi, I'm having trouble inserting facts into an existing prolog file, without overwriting the original contents. Suppose I have a file test.pl: :- dynamic born/2. born(john,london). born(tim,manchester). If I load this in prolog, and I assert more facts: | ?- assert(born(laura,kent)). yes I'm aware I can save this by doing: |?- tell('test.pl'),listing(born/2),told. Which works but test.pl now only contains the facts, not the ":- dynamic born/2": born(john,london). born(tim,manchester). born(laura,kent). This is problematic because if I reload this file, I won't be able to insert anymore facts into test.pl because ":- dynamic born/2." doesn't exist anymore. I read somewhere that, I could do: append('test.pl'),listing(born/2),told. which should just append to the end of the file, however, I get the following error: ! Existence error in user:append/1 ! procedure user:append/1 does not exist ! goal: user:append('test.pl') Btw, I'm using Sicstus prolog. Does this make a difference? Thanks!

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  • When getting substring in .Net, does the new string reference the same original string data or does

    - by Elan
    Assuming I have the following strings: string str1 = "Hello World!"; string str2 = str1.SubString(6, 5); // "World" I am hoping that in the above example str2 does not copy "World", but simply ends up being a new string that points to the same memory space only that it starts with an offset of 6 and a length of 5. In actuality I am dealing with some potentially very long strings and am interested in how this works behind the scenes for performance reasons. I am not familiar enaugh with IL to look into this.

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  • GAE datastore querying integer fields

    - by ParanoidAndroid
    I notice strange behavior when querying the GAE datastore. Under certain circumstances Filter does not work for integer fields. The following java code reproduces the problem: log.info("start experiment"); DatastoreService datastore = DatastoreServiceFactory.getDatastoreService(); int val = 777; // create and store the first entity. Entity testEntity1 = new Entity(KeyFactory.createKey("Test", "entity1")); Object value = new Integer(val); testEntity1.setProperty("field", value); datastore.put(testEntity1); // create the second entity by using BeanUtils. Test test2 = new Test(); // just a regular bean with an int field test2.setField(val); Entity testEntity2 = new Entity(KeyFactory.createKey("Test", "entity2")); Map<String, Object> description = BeanUtilsBean.getInstance().describe(test2); for(Entry<String,Object> entry:description.entrySet()){ testEntity2.setProperty(entry.getKey(), entry.getValue()); } datastore.put(testEntity2); // now try to retrieve the entities from the database... Filter equalFilter = new FilterPredicate("field", FilterOperator.EQUAL, val); Query q = new Query("Test").setFilter(equalFilter); Iterator<Entity> iter = datastore.prepare(q).asIterator(); while (iter.hasNext()) { log.info("found entity: " + iter.next().getKey()); } log.info("experiment finished"); the log looks like this: INFO: start experiment INFO: found entity: Test("entity1") INFO: experiment finished For some reason it only finds the first entity even though both entities are actually stored in the datastore and both 'field' values are 777 (I see it in the Datastore Viewer)! Why does it matter how the entity is created? I would like to use BeanUtils, because it is convenient. The same problem occurs on the local devserver and when deployed to GAE.

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  • How does Bitmap.Save(Stream, ImageFormat) format the data?

    - by Matt Jacobsen
    I have a non transparent, colour bitmap with length 2480 and width 3507. Using Bitmap.GetPixel(int x, int y) I am able to get the colour information of each pixel in the bitmap. If I squirt the bitmap into a byte[]: MemoryStream ms = new MemoryStream(); bmp.Save(ms, ImageFormat.Bmp); ms.Position = 0; byte[] bytes = ms.ToArray(); then I'd expect to have the same information, i.e. I can go to bytes[1000] and read the colour information for that pixel. It turns out that my array of bytes is larger than I anticipated. I thought I'd get an array with 2480 x 3507 = 8697360 elements. Instead I get an array with 8698438 elements - some sort of header I presume. In what format the bytes in my array stored? Is there a header 1078 bytes long followed by Alpha, Red, Green, Blue values for every byte element, or something else?

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  • Multiple IN statements for WHERE. Would this return good data?

    - by TheDudeAbides
    SELECT ['VISA CK - 021810$'].[ACCT NBR #1], ['VISA CK - 021810$'].[ALT CUST NM #1], ['VISA CK - 021810$'].[LAST USED] FROM ['VISA CK - 021810$'] WHERE ['VISA CK - 021810$'].[ALT CUST NM #1] IN ( SELECT ['VISA CK - 021810$'].[ALT CUST NM #1] FROM ['VISA CK - 021810$'] GROUP BY ['VISA CK - 021810$'].[ALT CUST NM #1] HAVING COUNT(['VISA CK - 021810$'].[ALT CUST NM #1]) > 1 ) AND ['VISA CK - 021810$'].[ACCT NBR #1] IN ( SELECT ['VISA CK - 021810$'].[ACCT NBR #1] FROM ['VISA CK - 021810$'] GROUP BY ['VISA CK - 021810$'].[ACCT NBR #1] HAVING COUNT(['VISA CK - 021810$'].[ACCT NBR #1]) > 1 )

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