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  • How to get at contents of placeholder::_1

    - by sheepsimulator
    I currently have the following code: using boost::bind; typedef boost::signal<void(EventDataItem&)> EventDataItemSignal; class EventDataItem { ... EventDataItemSignal OnTrigger; ... } typedef std::list< shared_ptr<EventDataItem> > DataItemList; typedef std::list<boost::signals::connection> ConnectionList; class MyClass { void OnStart() { DataItemList dilItems; ConnectionList clConns; DataItemList::iterator iterDataItems; for(iterDataItems = dilItems.begin(); iterDataItems != dilItems.end(); iterDataItems++) { // Create Connections from Triggers clConns.push_back((*iterDataItems)->OnTrigger.connect( bind(&MyClass::OnEventTrigger, this))); } } void OnEventTrigger() { // ... Do stuff on Trigger... } } I'd like to change MyClass::OnStart to use std::transform to achieve the same thing: void MyClass::OnStart() { DataItemList dilItems; ConnectionList clConns; // Resize connection list to match number of data items clConns.resize(dilItems.size()); // Build connection list from Items // note: errors on the placeholder _1->OnTrigger std::transform(dilItems.begin(), dilItems.end(), clConns.begin(), bind(&EventDataItemSignal::connect, _1->OnTrigger, bind(&MyClass::Stuff, this))); } However, my hiccup is _1-OnTrigger. How can I reference OnTrigger from placeholder _1?

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  • Compiled Haskell libraries with FFI imports are invalid when imported into GHCI

    - by John Millikin
    I am using GHC 6.12.1, in Ubuntu 10.04 When I try to use the FFI syntax for static storage, only modules running in interpreted mode (ie GHCI) work properly. Compiled modules have invalid pointers, and do not work. I'd like to know whether anybody can reproduce the problem, whether this an error in my code or GHC, and (if the latter) whether it's a known issue. I'm using sys_siglist because it's present in a standard library on my system, but I don't believe the actual storage used matters (I discovered this while writing a binding to libidn). If it helps, sys_siglist is defined in <signal.h> as: extern __const char *__const sys_siglist[_NSIG]; I thought this type might be the problem, so I also tried wrapping it in a plain C procedure: #include<stdio.h> const char **test_ffi_import() { printf("C think sys_siglist = %X\n", sys_siglist); return sys_siglist; } However, importing that doesn't change the result, and the printf() call prints the same pointer value as show siglist_a. My suspicion is that it's something to do with static and dynamic library loading. Update: somebody in #haskell suggested this might be 64-bit specific; if anybody tries to reproduce it, can you mention your architecture and whether it worked in a comment? Code as follows: -- A.hs {-# LANGUAGE ForeignFunctionInterface #-} module A where import Foreign import Foreign.C foreign import ccall "&sys_siglist" siglist_a :: Ptr CString -- -- B.hs {-# LANGUAGE ForeignFunctionInterface #-} module B where import Foreign import Foreign.C foreign import ccall "&sys_siglist" siglist_b :: Ptr CString -- -- Main.hs {-# LANGUAGE ForeignFunctionInterface #-} module Main where import Foreign import Foreign.C import A import B foreign import ccall "&sys_siglist" siglist_main :: Ptr CString main = do putStrLn $ "siglist_a = " ++ show siglist_a putStrLn $ "siglist_b = " ++ show siglist_b putStrLn $ "siglist_main = " ++ show siglist_main peekSiglist "a " siglist_a peekSiglist "b " siglist_b peekSiglist "main" siglist_main peekSiglist name siglist = do ptr <- peekElemOff siglist 2 str <- maybePeek peekCString ptr putStrLn $ "siglist_" ++ name ++ "[2] = " ++ show str I would expect something like this output, where all pointer values identical and valid: $ runhaskell Main.hs siglist_a = 0x00007f53a948fe00 siglist_b = 0x00007f53a948fe00 siglist_main = 0x00007f53a948fe00 siglist_a [2] = Just "Interrupt" siglist_b [2] = Just "Interrupt" siglist_main[2] = Just "Interrupt" However, if I compile A.hs (with ghc -c A.hs), then the output changes to: $ runhaskell Main.hs siglist_a = 0x0000000040378918 siglist_b = 0x00007fe7c029ce00 siglist_main = 0x00007fe7c029ce00 siglist_a [2] = Nothing siglist_b [2] = Just "Interrupt" siglist_main[2] = Just "Interrupt"

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  • Thread-local storage segfaults on NetBSD only?

    - by bortzmeyer
    Trying to run a C++ program, I get segmentation faults which appear to be specific to NetBSD. Bert Hubert wrote the simple test program (at the end of this message) and, indeed, it crashes only on NetBSD. % uname -a NetBSD golgoth 5.0.1 NetBSD 5.0.1 (GENERIC) #0: Thu Oct 1 15:46:16 CEST 2009 +stephane@golgoth:/usr/obj/sys/arch/i386/compile/GENERIC i386 % g++ --version g++ (GCC) 4.1.3 20080704 prerelease (NetBSD nb2 20081120) Copyright (C) 2006 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. % gdb thread-local-storage-powerdns GNU gdb 6.5 Copyright (C) 2006 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "i386--netbsdelf"... (gdb) run Starting program: /home/stephane/Programmation/C++/essais/thread-local-storage-powerdns Program received signal SIGSEGV, Segmentation fault. 0x0804881b in main () at thread-local-storage-powerdns.cc:20 20 t_a = new Bogo('a'); (gdb) On other Unix, it works fine. Is there a known issue in NetBSD with C++ thread-local storage? #include <stdio.h> class Bogo { public: explicit Bogo(char a) { d_a = a; } char d_a; }; __thread Bogo* t_a; int main() { t_a = new Bogo('a'); Bogo* b = t_a; printf("%c\n", b->d_a); }

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  • Django Testing: Faking User Creation

    - by Ygam
    I want to better write this test: def test_profile_created(self): self.client.post(reverse('registration_register'), data={ 'username':'ygam', 'email':'[email protected]', 'password1':'ygam', 'password2':'ygam' }) """ Test if a profile is created on save """ user = User.objects.get(username='ygam') self.assertTrue(UserProfile.objects.filter(user=user).exists()) and I just came upon this code on django-registration tests that does not actually "create" the user: def test_registration_signal(self): def receiver(sender, **kwargs): self.failUnless('user' in kwargs) self.assertEqual(kwargs['user'].username, 'bob') self.failUnless('request' in kwargs) self.failUnless(isinstance(kwargs['request'], WSGIRequest)) received_signals.append(kwargs.get('signal')) received_signals = [] signals.user_registered.connect(receiver, sender=self.backend.__class__) self.backend.register(_mock_request(), username='bob', email='[email protected]', password1='secret') self.assertEqual(len(received_signals), 1) self.assertEqual(received_signals, [signals.user_registered]) However he used a custom function for this "_mock_request": class _MockRequestClient(Client): def request(self, **request): environ = { 'HTTP_COOKIE': self.cookies, 'PATH_INFO': '/', 'QUERY_STRING': '', 'REMOTE_ADDR': '127.0.0.1', 'REQUEST_METHOD': 'GET', 'SCRIPT_NAME': '', 'SERVER_NAME': 'testserver', 'SERVER_PORT': '80', 'SERVER_PROTOCOL': 'HTTP/1.1', 'wsgi.version': (1,0), 'wsgi.url_scheme': 'http', 'wsgi.errors': self.errors, 'wsgi.multiprocess':True, 'wsgi.multithread': False, 'wsgi.run_once': False, 'wsgi.input': None, } environ.update(self.defaults) environ.update(request) request = WSGIRequest(environ) # We have to manually add a session since we'll be bypassing # the middleware chain. session_middleware = SessionMiddleware() session_middleware.process_request(request) return request def _mock_request(): return _MockRequestClient().request() However, it may be too long of a function for my needs. I want to be able to somehow "fake" the account creation. I have not much experience on mocks and stubs so any help would do. Thanks!

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  • CLLocationManagerDelegate method not calling in iPodTouch

    - by Siddharth
    HI all, I was using a sample code which uses CLLocationManager class to determine the current location of user. when i run this app on iPad i am getting the correct location but when i run the same app on iPod Touch i am getting a blank label i.e nothing is displayed on the label .although wi-fi signal strength is good in both iPod and iPad.The code looks like... - (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation{ int degrees = newLocation.coordinate.latitude; double decimal = fabs(newLocation.coordinate.latitude - degrees); int minutes = decimal * 60; double seconds = decimal * 3600 - minutes * 60; NSString *lat = [NSString stringWithFormat:@"%d° %d' %1.4f\"", degrees, minutes, seconds]; latLabel.text = lat; [latLocationArray addObject:lat]; degrees = newLocation.coordinate.longitude; decimal = fabs(newLocation.coordinate.longitude - degrees); minutes = decimal * 60; seconds = decimal * 3600 - minutes * 60; NSString *longt = [NSString stringWithFormat:@"%d° %d' %1.4f\"", degrees, minutes, seconds]; longLabel.text = longt; [longLocationArray addObject:longt]; }

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  • How to cache pages using background jobs ?

    - by Alexandre
    Definitions: resource = collection of database records, regeneration = processing these records and outputting the corresponding html Current flow: Receive client request Check for resource in cache If not in cache or cache expired, regenerate Return result The problem is that the regeneration step can tie up a single server process for 10-15 seconds. If a couple of users request the same resource, that could result in a couple of processes regenerating the exact same resource simultaneously, each taking up 10-15 seconds. Wouldn't it be preferrable to have the frontend signal some background process saying "Hey, regenerate this resource for me". But then what would it display to the user? "Rebuilding" is not acceptable. All resources would have to be in cache ahead of time. This could be a problem as the database would almost be duplicated on the filesystem (too big to fit in memory). Is there a way to avoid this? Not ideal, but it seems like the only way out. But then there's one more problem. How to keep the same two processes from requesting the regeneration of a resource at the same time? The background process could be regenerating the resource when a frontend asks for the regeneration of the same resource. I'm using PHP and the Zend Framework just in case someone wants to offer a platform-specific solution. Not that it matters though - I think this problem applies to any language/framework. Thanks!

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  • 1k of Program Space, 64 bytes of RAM. Is assembly an absolute must?

    - by Earlz
    (If your lazy see bottom for TL;DR) Hello, I am planning to build a new (prototype) project dealing with physical computing. Basically, I have wires. These wires all need to have their voltage read at the same time. More than a few hundred microseconds difference between the readings of each wire will completely screw it up. The Arduino takes about 114 microseconds. So the most I could read is 2 or 3 wires before the latency would skew the accuracy of the readings. So my plan is to have an Arduino as the "master" of an array of ATTinys. The arduino is pretty cramped for space, but it's a massive playground compared to the tinys. An ATTiny13A has 1k of flash ROM(program space), 64 bytes of RAM, and 64 bytes of (not-durable and slow) EEPROM. (I'm choosing this for price as well as size) The ATTinys in my system will not do much. Basically, all they will do is wait for a signal from the Master, and then read the voltage of 1 or 2 wires and store it in RAM(or possibly EEPROM if it's that cramped). And then send it to the Master using only 1 wire for data.(no room for more than that!). So far then, all I should have to do is implement trivial voltage reading code (using built in ADC). But this communication bit I'm worried about. Do you think a communication protocol(using just 1 wire!) could even be implemented in such constraints? TL;DR: In less than 1k of program space and 64 bytes of RAM(and 64 bytes of EEPROM) do you think it is possible to implement a 1 wire communication protocol? Would I need to drop to assembly to make it fit? I know that currently my Arduino programs linking to the Wiring library are over 8k, so I'm a bit concerned.

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  • Communication between parent and child

    - by Pierre
    Hi every one ! I have a little problem. I have to code a simple C application that creat a process and his child (fork()) and I have to do an operation. Parent initialize the values and child calculate. I write this : #include #include #include #include #include typedef struct { int op1; char op; int op2; }Operation; Operation *varOP; void finalResult() { float result = 0; if(varOP-op == '+') result = (varOP-op1 + varOP-op2); if(varOP-op == '-') result = (varOP-op1 - varOP-op2); if(varOP-op == '*') result = (varOP-op1 * varOP-op2); if(varOP-op == '+') result = (varOP-op1 / varOP-op2); printf("%f",result); } int main () { int p; varOP = (Operation *)malloc(sizeof(Operation)); p = fork(); if(p == 0) // If child { signal(SIGUSR1, finalResult ); pause(); } if(p 0) // If parent { varOP-op = '+'; varOP-op1 = 2; varOP-op2 = 3; kill(p, SIGUSR1); wait(NULL); } return 0; } But my child is never called. Is there something wrong with my code? Thanks for your help !

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  • In app purchase on iphone.: How to receive your available products *before* someone may be able to b

    - by Thorsten S.
    Currently I am loading my supported products from a plist and after that I send a SKProductsRequest to guarantee that my SKProducts are still valid. So I set up the request, start it and get the response in: (void)productsRequest:(SKProductsRequest *)request didReceiveResponse:(SKProductsResponse *)response Now, so far all functions correctly. Problem: From calling the request until receiving the response it may last several seconds. Until that my app is already loaded and the user may be able to choose and buy a product. But because no products have been received, the available products are not in sync with the validated products - unlikely, but possible error. So my idea is to wait until the data is loaded and only continue when the list is validated. (Just a few seconds waiting...). I have a singleton instance managing all products. + (MyClass *) sharedInstance { if (!sharedInstance) sharedInstance = [MyClass new]; // Now wait until we have our data [condition lock]; while (noEntriesYet) // is yes at begin [condition wait]; [condition unlock]; return sharedInstance; } - productsRequest: didReceiveResponse: { [condition lock]; // I have my data noEntriesYet = false; [condition signal]; [condition unlock]; } Problem: The app freezes. Everything works fine if didReceiveResponse is completed before the sharedInstance is queried. There are different threads, the lock is working if wait is reached during didReceiveResponse, everything fine. But if not, didReceiveResponse is never called even if the request was sent. The lock is released, everything looks ok. I have tried to send the product request in a separate NSThread, with NSOperationQueue...without avail. Why ? What is happening ? How to solve the problem ?

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  • is it possible to turn off vdso on glibc side?

    - by heroxbd
    I am aware that passing vdso=0 to kernel can turn this feature off, and that the dynamic linker in glibc can automatic detect and use vdso feature from kernel. Here I met with this problem. There is a RHEL 5.6 box (kernel 2.6.18-238.el5) in my institution where I only have a normal user access, probably suffering from RHEL bug 673616. As I compile a toolchain of linux-headers-3.9/gcc-4.7.2/glibc-2.17/binutils-2.23 on top of it, gcc bootstrap fails in cc1 in stage2 cannnot be run Program received signal SIGSEGV, Segmentation fault. 0x00002aaaaaaca6eb in ?? () (gdb) info sharedlibrary From To Syms Read Shared Object Library 0x00002aaaaaaabba0 0x00002aaaaaac3249 Yes (*) /home/benda/gnto/lib64/ld-linux-x86-64.so.2 0x00002aaaaacd29b0 0x00002aaaaace2480 Yes (*) /home/benda/gnto/usr/lib/libmpc.so.3 0x00002aaaaaef2cd0 0x00002aaaaaf36c08 Yes (*) /home/benda/gnto/usr/lib/libmpfr.so.4 0x00002aaaab14f280 0x00002aaaab19b658 Yes (*) /home/benda/gnto/usr/lib/libgmp.so.10 0x00002aaaab3b3060 0x00002aaaab3b3b50 Yes (*) /home/benda/gnto/lib/libdl.so.2 0x00002aaaab5b87b0 0x00002aaaab5c4bb0 Yes (*) /home/benda/gnto/usr/lib/libz.so.1 0x00002aaaab7d0e70 0x00002aaaab80f62c Yes (*) /home/benda/gnto/lib/libm.so.6 0x00002aaaaba70d40 0x00002aaaabb81aec Yes (*) /home/benda/gnto/lib/libc.so.6 (*): Shared library is missing debugging information. and a simple program #include <sys/time.h> #include <stdio.h> int main () { struct timeval tim; gettimeofday(&tim, NULL); return 0; } get segment fault in the same way if compiled against glibc-2.17 and xgcc from stage1. Both cc1 and the test program can be run on another running RHEL 5.5 (kernel 2.6.18-194.26.1.el5) with gcc-4.7.2/glibc-2.17/binutils-2.23 as normal user. I cannot simply upgrade the box to a newer RHEL version, nor could I turn VDSO off via sysctl or proc. The question is, is there a way to compile glibc so that it turns off VDSO unconditionally?

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  • Python: Catching / blocking SIGINT during system call

    - by danben
    I've written a web crawler that I'd like to be able to stop via the keyboard. I don't want the program to die when I interrupt it; it needs to flush its data to disk first. I also don't want to catch KeyboardInterruptedException, because the persistent data could be in an inconsistent state. My current solution is to define a signal handler that catches SIGINT and sets a flag; each iteration of the main loop checks this flag before processing the next url. However, I've found that if the system happens to be executing socket.recv() when I send the interrupt, I get this: ^C Interrupted; stopping... // indicates my interrupt handler ran Traceback (most recent call last): File "crawler_test.py", line 154, in <module> main() ... File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/socket.py", line 397, in readline data = recv(1) socket.error: [Errno 4] Interrupted system call and the process exits completely. Why does this happen? Is there a way I can prevent the interrupt from affecting the system call?

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  • Programmatically controlled virtual drive

    - by Robert Lin
    How would I go about creating a virtual drive with which I can programmatically and dynamically change the contents? For instance, program A starts running and creates a virtual drive. When program B looks in the drive, it sees an error log and starts reading/processing it. In the middle of all this program A gets a signal from somewhere and decides to add to the log. I want program B to be unaware of the change and just keep on going. Program B should continue reading as if nothing happened. Program A would just report a rediculously large file size for the log and then fill it in as appropriate. Program A would fill the log with tags if program B tries to read past the last entry. I know this is a weird request but there's really no other way to do this... I basically can't rewrite program B so I need to fool it. How do I do this in windows? How about OSX?

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  • Return a list of important Python modules in a script?

    - by Jono Bacon
    Hi All, I am writing a program that categorizes a list of Python files by which modules they import. As such I need to scan the collection of .py files ad return a list of which modules they import. As an example, if one of the files I import has the following lines: import os import sys, gtk I would like it to return: ["os", "sys", "gtk"] I played with modulefinder and wrote: from modulefinder import ModuleFinder finder = ModuleFinder() finder.run_script('testscript.py') print 'Loaded modules:' for name, mod in finder.modules.iteritems(): print '%s ' % name, but this returns more than just the modules used in the script. As an example in a script which merely has: import os print os.getenv('USERNAME') The modules returned from the ModuleFinder script return: tokenize heapq __future__ copy_reg sre_compile _collections cStringIO _sre functools random cPickle __builtin__ subprocess cmd gc __main__ operator array select _heapq _threading_local abc _bisect posixpath _random os2emxpath tempfile errno pprint binascii token sre_constants re _abcoll collections ntpath threading opcode _struct _warnings math shlex fcntl genericpath stat string warnings UserDict inspect repr struct sys pwd imp getopt readline copy bdb types strop _functools keyword thread StringIO bisect pickle signal traceback difflib marshal linecache itertools dummy_thread posix doctest unittest time sre_parse os pdb dis ...whereas I just want it to return 'os', as that was the module used in the script. Can anyone help me achieve this?

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  • 1k of Program Space, 64 bytes of RAM. Is 1 wire communication possible?

    - by Earlz
    (If your lazy see bottom for TL;DR) Hello, I am planning to build a new (prototype) project dealing with physical computing. Basically, I have wires. These wires all need to have their voltage read at the same time. More than a few hundred microseconds difference between the readings of each wire will completely screw it up. The Arduino takes about 114 microseconds. So the most I could read is 2 or 3 wires before the latency would skew the accuracy of the readings. So my plan is to have an Arduino as the "master" of an array of ATTinys. The arduino is pretty cramped for space, but it's a massive playground compared to the tinys. An ATTiny13A has 1k of flash ROM(program space), 64 bytes of RAM, and 64 bytes of (not-durable and slow) EEPROM. (I'm choosing this for price as well as size) The ATTinys in my system will not do much. Basically, all they will do is wait for a signal from the Master, and then read the voltage of 1 or 2 wires and store it in RAM(or possibly EEPROM if it's that cramped). And then send it to the Master using only 1 wire for data.(no room for more than that!). So far then, all I should have to do is implement trivial voltage reading code (using built in ADC). But this communication bit I'm worried about. Do you think a communication protocol(using just 1 wire!) could even be implemented in such constraints? TL;DR: In less than 1k of program space and 64 bytes of RAM(and 64 bytes of EEPROM) do you think it is possible to implement a 1 wire communication protocol? Would I need to drop to assembly to make it fit? I know that currently my Arduino programs linking to the Wiring library are over 8k, so I'm a bit concerned.

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  • tipfy for Google App Engine: Is it stable? Can auth/session components of tipfy be used with webapp?

    - by cv12
    I am building a web application on Google App Engine that requires users to register with the application and subsequently authenticate with it and maintain sessions. I don't want to force users to have Google accounts. Also, the target audience for the application is the average non-geek, so I'm not very keen on using OpenID or OAuth. I need something simple like: User registers with an e-mail and password, and then can log back in with those credentials. I understand that this approach does not provide the security benefits of Google or OpenID authentication, but I am prepared to trade foolproof security for end-user convenience and hassle-free experience. I explored Django, but decided that consecutive deprecations from appengine-helper to app-engine-patch to django-nonrel may signal that path may be a bit risky in the long-term. I'd like to use a code base that is likely to be maintained consistently. I also explored standalone session/auth packages like gaeutilities and suas. GAEUtilities looked a bit immature (e.g., the code wasn't pythonic in places, in my opinion) and SUAS did not give me a lot of comfort with the cookie-only sessions. I could be wrong with my assessment of these two, so I would appreciate input on those (or others that may serve my objective). Finally, I recently came across tipfy. It appears to be based on Werkzeug and Alex Martelli spoke highly of it here on stackoverflow. I have two primary questions related to tipfy: As a framework, is it as mature as webapp? Is it stable and likely to be maintained for some time? Since my primary interest is the auth/session components, can those components of the tipfy framework be used with webapp, independent of the broader tipfy framework? If yes, I would appreciate a few pointers to how I could go about doing that.

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  • Qt and variadic functions

    - by Noah Roberts
    OK, before lecturing me on the use of C-style variadic functions in C++...everything else has turned out to require nothing short of rewriting the Qt MOC. What I'd like to know is whether or not you can have a "slot" in a Qt object that takes an arbitrary amount/type of arguments. The thing is that I really want to be able to generate Qt objects that have slots of an arbitrary signature. Since the MOC is incompatible with standard preprocessing and with templates, it's not possible to do so with either direct approach. I just came up with another idea: struct funky_base : QObject { Q_OBJECT funky_base(QObject * o = 0); public slots: virtual void the_slot(...) = 0; }; If this is possible then, because you can make a template that is a subclass of a QObject derived object so long as you don't declare new Qt stuff in it, I should be able to implement a derived templated type that takes the ... stuff and turns it into the appropriate, expected types. If it is, how would I connect to it? Would this work? connect(x, SIGNAL(someSignal(int)), y, SLOT(the_slot(...))); If nobody's tried anything this insane and doesn't know off hand, yes I'll eventually try it myself...but I am hoping someone already has existing knowledge I can tap before possibly wasting my time on it.

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  • WPF, notify a child in the element tree about an event in a parent

    - by jester
    I am developing a WPF app and I want an event in a parent to be notified to several of its children in the element tree, so that each of them can take an action accordingly. I know that a custom RoutedEvent can be used to signal in the other direction from a child to one of its ancestors by bubbling the event upwards, so that any of the ancestor elements can handle the event. What I want is the children to be notified about an event in the parent and they handle them appropriately. What is the best strategy to achieve this? EDIT: Clarifying the comments : Say I have a parent UserControl. It has a TabControl and its contents are several nested child UserControls. Now consider a scenario where I want the TabControl.SelectionChanged() event to cause some changes in each of the child UserControl. How to achieve this? (The contents of each tab is a UserControl which themselves may contain another few levels of children UserControls. I want the UserControl in the bottom level to know about the SelectionChanged() event and respond accordingly).

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  • Catching / blocking SIGINT during system call

    - by danben
    I've written a web crawler that I'd like to be able to stop via the keyboard. I don't want the program to die when I interrupt it; it needs to flush its data to disk first. I also don't want to catch KeyboardInterruptedException, because the persistent data could be in an inconsistent state. My current solution is to define a signal handler that catches SIGINT and sets a flag; each iteration of the main loop checks this flag before processing the next url. However, I've found that if the system happens to be executing socket.recv() when I send the interrupt, I get this: ^C Interrupted; stopping... // indicates my interrupt handler ran Traceback (most recent call last): File "crawler_test.py", line 154, in <module> main() ... File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/socket.py", line 397, in readline data = recv(1) socket.error: [Errno 4] Interrupted system call and the process exits completely. Why does this happen? Is there a way I can prevent the interrupt from affecting the system call?

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  • How can I compare market data feed sources for quality and latency improvement?

    - by yves Baumes
    I am in the very first stages of implementing a tool to compare 2 market data feed sources in order to prove the quality of new developed sources to my boss ( meaning there are no regressions, no missed updates, or wrong ), and to prove latencies improvement. So the tool I need must be able to check updates differences as well as to tell which source is the best (in term of latency). Concrectly, reference source could be Reuters while the other one is a Feed handler we develop internally. People warned me that updates might not arrive in the same order as Reuters implementation could differs totally from ours. Therefore a simple algorithm based on the fact that updates could arrive in the same order is likely not to work. My very first idea would be to use fingerprint to compare feed sources, as Shazaam application does to find the title of the tube you are submitting. Google told me it is based on FFT. And I was wondering if signal processing theory could behaves well with market access applications. I wanted to know your own experience in that field, is that possible to develop a quite accurate algorithm to meet the needs? What was your own idea? What do you think about fingerprint based comparison?

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  • C# Accepting sockets in async fasion - best practices

    - by psulek
    What is the best way to accept new sockets in async way. First way: while (!abort && listener.Server.IsBound) { acceptedSocketEvent.Reset(); listener.BeginAcceptSocket(AcceptConnection, null); bool signaled = false; do { signaled = acceptedSocketEvent.WaitOne(1000, false); } while (!signaled && !abort && listener.Server.IsBound); } where AcceptConnection should be: private void AcceptConnection(IAsyncResult ar) { // Signal the main thread to continue. acceptedSocketEvent.Set(); Socket socket = listener.EndAcceptSocket(ar); // continue to receive data and so on... .... } or Second way: listener.BeginAcceptSocket(AcceptConnection, null); while (!abort && listener.Server.IsBound) { Thread.Sleep(500); } and AcceptConnection will be: private void AcceptConnection(IAsyncResult ar) { Socket socket = listener.EndAcceptSocket(ar); // begin accepting next socket listener.BeginAcceptSocket(AcceptConnection, null); // continue to receive data and so on... .... } What is your prefered way and why?

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  • Weird Qt SSL issue -- error "No Error" shows up, nothing else, and if I ignore it, everything works

    - by houbysoft
    The issue is as follows : in my Qt app, I have a QWebView, which I use to load a HTTPS page. Everything worked fine on my development machine, so I'm now trying to get it to run on a test machine. I ran the app, but the page didn't load (the QWebView was blank). After much debugging, I found the problem is that an SSL error shows up, and the sslErrors() signal is fired. Here is my sslErrors() handling code: void blah::sslErrors(QNetworkReply *reply, const QList<QSslError> &errors) { foreach(QSslError error, errors) { qDebug() << error.errorString() << endl; } reply->ignoreSslErrors(); } The only thing the above code prints is: "No error" So there's no error, but unless I call reply->ignoreSslErrors(), the page doesn't load (on the test machine, on my developer computer no error is reported). Huh? Is this a bug? Is it safe to ignore the error, if I make sure it's of the type "No error"?

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  • CLLocationManager class method not calling in iPodTouch

    - by Siddharth
    HI all, I was using a sample code which uses CLLocationManager class to determine the current location of user. when i run this app on iPad i am getting the correct location but when i run the same app on iPod Touch i am getting a blank label i.e nothing is displayed on the label .although wi-fi signal strength is good in both iPod and iPad.The code looks like... - (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation{ int degrees = newLocation.coordinate.latitude; double decimal = fabs(newLocation.coordinate.latitude - degrees); int minutes = decimal * 60; double seconds = decimal * 3600 - minutes * 60; NSString *lat = [NSString stringWithFormat:@"%d° %d' %1.4f\"", degrees, minutes, seconds]; latLabel.text = lat; [latLocationArray addObject:lat]; degrees = newLocation.coordinate.longitude; decimal = fabs(newLocation.coordinate.longitude - degrees); minutes = decimal * 60; seconds = decimal * 3600 - minutes * 60; NSString *longt = [NSString stringWithFormat:@"%d° %d' %1.4f\"", degrees, minutes, seconds]; longLabel.text = longt; [longLocationArray addObject:longt]; }

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  • Avoiding a fork()/SIGCHLD race condition

    - by larry
    Please consider the following fork()/SIGCHLD pseudo-code. // main program excerpt for (;;) { if ( is_time_to_make_babies ) { pid = fork(); if (pid == -1) { /* fail */ } else if (pid == 0) { /* child stuff */ print "child started" exit } else { /* parent stuff */ print "parent forked new child ", pid children.add(pid); } } } // SIGCHLD handler sigchld_handler(signo) { while ( (pid = wait(status, WNOHANG)) > 0 ) { print "parent caught SIGCHLD from ", pid children.remove(pid); } } In the above example there's a race-condition. It's possible for "/* child stuff */" to finish before "/* parent stuff */" starts which can result in a child's pid being added to the list of children after it's exited, and never being removed. When the time comes for the app to close down, the parent will wait endlessly for the already-finished child to finish. One solution I can think of to counter this is to have two lists: started_children and finished_children. I'd add to started_children in the same place I'm adding to children now. But in the signal handler, instead of removing from children I'd add to finished_children. When the app closes down, the parent can simply wait until the difference between started_children and finished_children is zero. Another possible solution I can think of is using shared-memory, e.g. share the parent's list of children and let the children .add and .remove themselves? But I don't know too much about this. EDIT: Another possible solution, which was the first thing that came to mind, is to simply add a sleep(1) at the start of /* child stuff */ but that smells funny to me, which is why I left it out. I'm also not even sure it's a 100% fix. So, how would you correct this race-condition? And if there's a well-established recommended pattern for this, please let me know! Thanks.

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  • MYSQL not running on Ubuntu OS - Error 2002.

    - by mgj
    Hi, I am a novice to mysql DB. I am trying to run the MYSQL Server on Ubuntu 10.04. Through Synaptic Package Manager I am have installed the mysql version: mysql-client-5.1 I wonder that how was the database password set for the mysql-client software that I installed through the above way.It would be nice if you could enlighten me on this. When I tried running this database, I encountered the error given below: mohnish@mohnish-laptop:/var/lib$ mysql ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) mohnish@mohnish-laptop:/var/lib$ I referred to a similar question posted by another user. I didn't find a solution through the proposed answers. For instance when I tried the solutions posted for the similar question I got the following: mohnish@mohnish-laptop:/var/lib$ service start mysqld start: unrecognized service mohnish@mohnish-laptop:/var/lib$ ps -u mysql ERROR: User name does not exist. ********* simple selection ********* ********* selection by list ********* -A all processes -C by command name -N negate selection -G by real group ID (supports names) -a all w/ tty except session leaders -U by real user ID (supports names) -d all except session leaders -g by session OR by effective group name -e all processes -p by process ID T all processes on this terminal -s processes in the sessions given a all w/ tty, including other users -t by tty g OBSOLETE -- DO NOT USE -u by effective user ID (supports names) r only running processes U processes for specified users x processes w/o controlling ttys t by tty *********** output format ********** *********** long options *********** -o,o user-defined -f full --Group --User --pid --cols --ppid -j,j job control s signal --group --user --sid --rows --info -O,O preloaded -o v virtual memory --cumulative --format --deselect -l,l long u user-oriented --sort --tty --forest --version -F extra full X registers --heading --no-heading --context ********* misc options ********* -V,V show version L list format codes f ASCII art forest -m,m,-L,-T,H threads S children in sum -y change -l format -M,Z security data c true command name -c scheduling class -w,w wide output n numeric WCHAN,UID -H process hierarchy mohnish@mohnish-laptop:/var/lib$ which mysql /usr/bin/mysql mohnish@mohnish-laptop:/var/lib$ mysql ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) I even tried referring to http://forums.mysql.com/read.php?11,27769,84713#msg-84713 but couldn't find anything useful. Please let me know how I could tackle this error. Thank you very much..

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  • How to compare two variables from a java class in jess and execute a rule?

    - by user3417084
    I'm beginner in Jess. I'm trying to compare two variables from a Java class in Jess and trying to execute a rule. I have imported cTNumber and measuredCurrent (both are integer)form a java class called CurrentSignal. Similarly imported vTNumberand measuredVoltage form a java class DERSignal. Now I want to make a rule such that if cTNumber is equal to vTNumber then multiply measuredCurrent and measuredVoltage (Both are double) for calculating power. I'm trying in this way.... (import signals.*) (deftemplate CurrentSignal (declare (from-class CurrentSignal))) (deftemplate DERSignal (declare (from-class DERSignal))) (defglobal ?*CTnumber* = 0) (defglobal ?*VTnumber* = 0) (defglobal ?*VTnumberDER* = 0) (defglobal ?*measuredCurrent* = 0) (defglobal ?*measuredVoltage* = 0) (defglobal ?*measuredVoltageDER* = 0) (defrule Get-CT-Number (CurrentSignal (cTNumber ?m)) (CurrentSignal (measuredCurrent ?c)) => (bind ?*measuredCurrent* ?c) (printout t "Measured Current : " ?*measuredCurrent*" Amps"crlf) (bind ?*CTnumber* ?m) (printout t ?*CTnumber* crlf) ) (defrule Get-DER-Number (DERSignal (vTNumber ?o)) (DERSignal (measuredVoltage ?V)) => (bind ?*measuredVoltageDER* ?V) (printout t "Measured Voltage : " ?*measuredVoltageDER* " V" crlf) (bind ?*VTnumberDER* ?o) (printout t ?*VTnumberDER* crlf) ) (defrule Power-Calculation-DER-signal "Power calculation of DER Bay" (test (= ?*CTnumber* ?*VTnumberDER* )) => (printout t "Total Generation : " (* ?*measuredCurrent* ?*measuredVoltageDER*) crlf) ) But the Total Generation is showing 0. But I tried calculating in Java and it's showing a number. Can anyone please help me to solve this problem. Thank you.

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