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  • Should I skip authorization, with CanCan, of an action that instantiates a resource?

    - by irkenInvader
    I am writing a web app to pick random lists of cards from larger, complete sets of cards. I have a Card model and a CardSet model. Both models have a full RESTful set of 7 actions (:index, :new, :show, etc). The CardSetsController has an extra action for creating random sets: :random. # app/models/card_set.rb class CardSet < ActiveRecord::Base belongs_to :creator, :class_name => "User" has_many :memberships has_many :cards, :through => :memberships # app/models/card.rb class Card < ActiveRecord::Base belongs_to :creator, :class_name => "User" has_many :memberships has_many :card_sets, :through => :memberships I have added Devise for authentication and CanCan for authorizations. I have users with an 'editor' role. Editors are allowed to create new CardSets. Guest users (Users who have not logged in) can only use the :index and :show actions. These authorizations are working as designed. Editors can currently use both the :random and the :new actions without any problems. Guest users, as expected, cannot. # app/controllers/card_sets_controller.rb class CardSetsController < ApplicationController before_filter :authenticate_user!, :except => [:show, :index] load_and_authorize_resource I want to allow guest users to use the :random action, but not the :new action. In other words, they can see new random sets, but not save them. The "Save" button on the :random action's view is hidden (as designed) from the guest users. The problem is, the first thing the :random action does is build a new instance of the CardSet model to fill out the view. When cancan tries to load_and_authorize_resource a new CardSet, it throws a CanCan::AccessDenied exception. Therefore, the view never loads and the guest user is served a "You need to sign in or sign up before continuing" message. # app/controllers/card_sets_controllers.rb def random @card_set = CardSet.new( :name => "New Set of 10", :set_type => "Set of 10" ) I realize that I can tell load_and_authorize_resource to skip the :random action by passing :except => :random to the call, but that just feels "wrong" for some reason. What's the "right" way to do this? Should I create the new random set without instantiating a new CardSet? Should I go ahead and add the exception?

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  • How would I create a VIM or Vi command to delete all text after a certain character for every line i

    - by Jason Down
    Scenario: I have a text file that has pipe (as in the "|" character) delimited data. Each field of data in the pipe delimited fields can be of variable length, so counting characters won't work (or using some sort of substring function... if that even exists in VIM). Is it possible, using VIM / Vi to delete all data from the second pipe to the end of the line for the entire file? There are approx 150,000 lines, so doing this manually would only be appealing to a masochist... e.g. Change the following lines from: 1111|random sized text 12345|more random data la la la|1111|abcde 2222|random sized text abcdefghijk|la la la la|2222|defgh 3333|random sized text|more random data|33333|ijklmnop to: 1111|random sized text 12345 2222|random sized text abcdefghijk 3333|random sized text I'm sure this can be done somehow... I hope. TIA UPDATE: I should have mentioned that I'm running this on Windows XP, so I don't have access to some of the mentioned *nix commands (CUT is not recognized on Windows).

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  • What's the difference between single and double quotes in Objective-C?

    - by Alex Mcp
    I'm working through a book exercise to generate some random serial number, and here's my function: NSString *randomSerialNumber = [NSString stringWithFormat:@"%c%c%c%c%c", '0' + random() % 10, 'A' + random() % 26, '0' + random() % 10, 'A' + random() % 26, '0' + random() % 10]; This works and has an output like: 2J6X7. But before, the 0s and As I had wrapped in double quotes, and an example output was 11764iÒ˜. What did I do wrong my first time around, and why did using single quotes fix it?

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  • gnuplot - multiple lines with different x ranges

    - by Aly
    Hi, I am using gnuplot to try and plot several lines but each have different x ranges. I am running the following script: # gnuplot script for 'omarConf2EvONLY-vs-everyone-gta-lag-lpas-omarConf1-random-tag-tpas.dat' plot "omarConf2EvONLY-vs-everyone-gta-lag-lpas-omarConf1-random-tag-tpas.dat" using 1:2 with lines title '1' replot "omarConf2EvONLY-vs-everyone-gta-lag-lpas-omarConf1-random-tag-tpas.dat" using 1:3 with lines title '2' replot "omarConf2EvONLY-vs-everyone-gta-lag-lpas-omarConf1-random-tag-tpas.dat" using 1:4 with lines title '3' replot "omarConf2EvONLY-vs-everyone-gta-lag-lpas-omarConf1-random-tag-tpas.dat" using 1:5 with lines title '4' replot "omarConf2EvONLY-vs-everyone-gta-lag-lpas-omarConf1-random-tag-tpas.dat" using 1:6 with lines title '5' replot "omarConf2EvONLY-vs-everyone-gta-lag-lpas-omarConf1-random-tag-tpas.dat" using 1:7 with lines title '6' replot "omarConf2EvONLY-vs-everyone-gta-lag-lpas-omarConf1-random-tag-tpas.dat" using 1:8 with lines title '7' set terminal png size 800,600 set output "omar_vs_everyone-EVONLY.png" replot and the .dat file is just a file with columns such as: 1 0.5 0.5 0.1 2 0.6 1.3 0.8 3 0.7 0.32 4 0.7 0.35 5 1.3 4.32 6 1.67 notice that the columns have different lengths as each line has different x ranges. The problem I have is that it plots funny as shown below:

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  • Better way to write an object generator for an RAII template class?

    - by Dan
    I would like to write an object generator for a templated RAII class -- basically a function template to construct an object using type deduction of parameters so the types don't have to be specified explicitly. The problem I foresee is that the helper function that takes care of type deduction for me is going to return the object by value, which will result in a premature call to the RAII destructor when the copy is made. Perhaps C++0x move semantics could help but that's not an option for me. Anyone seen this problem before and have a good solution? This is what I have: template<typename T, typename U, typename V> class FooAdder { private: typedef OtherThing<T, U, V> Thing; Thing &thing_; int a_; // many other members public: FooAdder(Thing &thing, int a); ~FooAdder(); void foo(T t, U u); void bar(V v); }; The gist is that OtherThing has a horrible interface, and FooAdder is supposed to make it easier to use. The intended use is roughly like this: FooAdder(myThing, 2) .foo(3, 4) .foo(5, 6) .bar(7) .foo(8, 9); The FooAdder constructor initializes some internal data structures. The foo and bar methods populate those data structures. The ~FooAdder dtor wraps things up and calls a method on thing_, taking care of all the nastiness. That would work fine if FooAdder wasn't a template. But since it is, I would need to put the types in, more like this: FooAdder<Abc, Def, Ghi>(myThing, 2) ... That's annoying, because the types can be inferred based on myThing. So I would prefer to create a templated object generator, similar to std::make_pair, that will do the type deduction for me. Something like this: template<typename T, typename U, typename V> FooAdder<T, U, V> AddFoo(Thing &thing, int a) { return FooAdder<T, U, V>(thing, a); } That seems problematic: because it returns by value, the stack temporary object will be destructed, which will cause the RAII dtor to run prematurely. One thought I had was to give FooAdder a copy ctor with move semantics, kinda like std::auto_ptr. But I would like to do this without dynamic memory allocation, so I thought the copy ctor could set a flag within FooAdder indicating the dtor shouldn't do the wrap-up. Like this: FooAdder(FooAdder &rhs) // Note: rhs is not const : thing_(rhs.thing_) , a_(rhs.a_) , // etc... lots of other members, annoying. , moved(false) { rhs.moved = true; } ~FooAdder() { if (!moved) { // do whatever it would have done } } Seems clunky. Anyone got a better way?

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  • Cumulative +1/-1 Cointoss crashes on 1000 iterations. Please advise; c++ boost random libraries

    - by user1731972
    following some former advice Multithreaded application, am I doing it right? I think I have a threadsafe number generator using boost, but my program crashes when I input 1000 iterations. The output .csv file when graphed looks right, but I'm not sure why it's crashing. It's using _beginthread, and everyone is telling me I should use the more (convoluted) _beingthreadex, which I'm not familiar with. If someone could recommend an example, I would greatly appreciate it. Also... someone pointed out I should be applying a second parameter to my _beginthread for the array counting start positions, but I have no idea how to pass more than one parameter, other than attempting to use a structure, and I've read structure's and _beginthread don't get along (although, I could just use the boost threads...) #include <process.h> #include <windows.h> #include <iostream> #include <fstream> #include <time.h> #include <random> #include <boost/random.hpp> //for srand48_r(time(NULL), &randBuffer); which doesn't work #include <stdio.h> #include <stdlib.h> //#include <thread> using namespace std; using namespace boost; using namespace boost::random; void myThread0 (void *dummy ); void myThread1 (void *dummy ); void myThread2 (void *dummy ); void myThread3 (void *dummy ); //for random seeds void initialize(); //from http://stackoverflow.com/questions/7114043/random-number-generation-in-c11-how-to-generate-how-do-they-work uniform_int_distribution<> two(1,2); typedef std::mt19937 MyRNG; // the Mersenne Twister with a popular choice of parameters uint32_t seed_val; // populate somehow MyRNG rng1; // e.g. keep one global instance (per thread) MyRNG rng2; // e.g. keep one global instance (per thread) MyRNG rng3; // e.g. keep one global instance (per thread) MyRNG rng4; // e.g. keep one global instance (per thread) //only needed for shared variables //CRITICAL_SECTION cs1,cs2,cs3,cs4; // global int main() { ofstream myfile; myfile.open ("coinToss.csv"); int rNum; long numRuns; long count = 0; int divisor = 1; float fHolder = 0; long counter = 0; float percent = 0.0; //? //unsigned threadID; //HANDLE hThread; initialize(); HANDLE hThread[4]; const int size = 100000; int array[size]; printf ("Runs (uses multiple of 100,000) "); cin >> numRuns; for (int a = 0; a < numRuns; a++) { hThread[0] = (HANDLE)_beginthread( myThread0, 0, (void*)(array) ); hThread[1] = (HANDLE)_beginthread( myThread1, 0, (void*)(array) ); hThread[2] = (HANDLE)_beginthread( myThread2, 0, (void*)(array) ); hThread[3] = (HANDLE)_beginthread( myThread3, 0, (void*)(array) ); //waits for threads to finish before continuing WaitForMultipleObjects(4, hThread, TRUE, INFINITE); //closes handles I guess? CloseHandle( hThread[0] ); CloseHandle( hThread[1] ); CloseHandle( hThread[2] ); CloseHandle( hThread[3] ); //dump array into calculations //average array into fHolder //this could be split into threads as well for (int p = 0; p < size; p++) { counter += array[p] == 2 ? 1 : -1; //cout << array[p] << endl; //cout << counter << endl; } //this fHolder calculation didn't work //fHolder = counter / size; //so I had to use this cout << counter << endl; fHolder = counter; fHolder = fHolder / size; myfile << fHolder << endl; } } void initialize() { //seed value needs to be supplied //rng1.seed(seed_val*1); rng1.seed((unsigned int)time(NULL)); rng2.seed(((unsigned int)time(NULL))*2); rng3.seed(((unsigned int)time(NULL))*3); rng4.seed(((unsigned int)time(NULL))*4); }; void myThread0 (void *param) { //EnterCriticalSection(&cs1); //aquire the critical section object int *i = (int *)param; for (int x = 0; x < 25000; x++) { //doesn't work, part of merssene twister //i[x] = next(); i[x] = two(rng1); //original srand //i[x] = rand() % 2 + 1; //doesn't work for some reason. //uint_dist2(rng); //i[x] = qrand() % 2 + 1; //cout << i[x] << endl; } //LeaveCriticalSection(&cs1); // release the critical section object } void myThread1 (void *param) { //EnterCriticalSection(&cs2); //aquire the critical section object int *i = (int *)param; for (int x = 25000; x < 50000; x++) { //param[x] = rand() % 2 + 1; i[x] = two(rng2); //i[x] = rand() % 2 + 1; //cout << i[x] << endl; } //LeaveCriticalSection(&cs2); // release the critical section object } void myThread2 (void *param) { //EnterCriticalSection(&cs3); //aquire the critical section object int *i = (int *)param; for (int x = 50000; x < 75000; x++) { i[x] = two(rng3); //i[x] = rand() % 2 + 1; //cout << i[x] << endl; } //LeaveCriticalSection(&cs3); // release the critical section object } void myThread3 (void *param) { //EnterCriticalSection(&cs4); //aquire the critical section object int *i = (int *)param; for (int x = 75000; x < 100000; x++) { i[x] = two(rng4); //i[x] = rand() % 2 + 1; //cout << i[x] << endl; } //LeaveCriticalSection(&cs4); // release the critical section object }

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  • Varnish VCL - Regular Expression Evaluation

    - by Hugues ALARY
    I have been struggling for the past few days with this problem: Basically, I want to send to a client browser a cookie of the form foo[sha1oftheurl]=[randomvalue] if and only if the cookie has not already been set. e.g. If a client browser requests "/page.html", the HTTP response will be like: resp.http.Set-Cookie = "foo4c9ae249e9e061dd6e30893e03dc10a58cc40ee6=ABCD;" then, if the same client request "/index.html", the HTTP response will contain a header: resp.http.Set-Cookie = "foo14fe4559026d4c5b5eb530ee70300c52d99e70d7=QWERTY;" In the end, the client browser will have 2 cookies: foo4c9ae249e9e061dd6e30893e03dc10a58cc40ee6=ABCD foo14fe4559026d4c5b5eb530ee70300c52d99e70d7=QWERTY Now, that, is not complicated in itself. The following code does it: import digest; import random; ##This vmod does not exist, it's just for the example. sub vcl_recv() { ## We compute the sha1 of the requested URL and store it in req.http.Url-Sha1 set req.http.Url-Sha1 = digest.hash_sha1(req.url); set req.http.random-value = random.get_rand(); } sub vcl_deliver() { ## We create a cookie on the client browser by creating a "Set-Cookie" header ## In our case the cookie we create is of the form foo[sha1]=[randomvalue] ## e.g for a URL "/page.html" the cookie will be foo4c9ae249e9e061dd6e30893e03dc10a58cc40ee6=[randomvalue] set resp.http.Set-Cookie = {""} + resp.http.Set-Cookie + "foo"+req.http.Url-Sha1+"="+req.http.random-value; } However, this code does not take into account the case where the Cookie already exists. I need to check that the Cookie does not exists before generating a random value. So I thought about this code: import digest; import random; sub vcl_recv() { ## We compute the sha1 of the requested URL and store it in req.http.Url-Sha1 set req.http.Url-Sha1 = digest.hash_sha1(req.url); set req.http.random-value = random.get_rand(); set req.http.regex = "abtest"+req.http.Url-Sha1; if(!req.http.Cookie ~ req.http.regex) { set req.http.random-value = random.get_rand(); } } The problem is that Varnish does not compute Regular expression at run time. Which leads to this error when I try to compile: Message from VCC-compiler: Expected CSTR got 'req.http.regex' (program line 940), at ('input' Line 42 Pos 31) if(req.http.Cookie !~ req.http.regex) { ------------------------------##############--- Running VCC-compiler failed, exit 1 VCL compilation failed One could propose to solve my problem by matching on the "abtest" part of the cookie or even "abtest[a-fA-F0-9]{40}": if(!req.http.Cookie ~ "abtest[a-fA-F0-9]{40}") { set req.http.random-value = random.get_rand(); } But this code matches any cookie starting by 'abtest' and containing an hexadecimal string of 40 characters. Which means that if a client requests "/page.html" first, then "/index.html", the condition will evaluate to true even if the cookie for the "/index.html" has not been set. I found in bug report phk or someone else stating that computing regular expressions was extremely expensive which is why they are evaluated during compilation. Considering this, I believe that there is no way of achieving what I want the way I've been trying to. Is there any way of solving this problem, other than writting a vmod? Thanks for your help! -Hugues

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  • NHibernate HiLo - new column per entity and HiLo catches

    - by Gareth
    Im currently using the hilo id generator for my classes but have just been using the minimal of settings eg <class name="ClassA" <id name="Id" column="id" unsaved-value="0" <generator class="hilo" / </id ... But should I really be specifying a new column for NHibernate to use foreach entity and providing it with a max lo? <class name="ClassA" <id name="Id" column="id" unsaved-value="0" <generator class="hilo" <param name="table"hibernate_unique_key</param <param name="column"classA_nexthi</param <param name="max_lo"20</param </generator </id ... <class name="ClassB" <id name="Id" column="id" unsaved-value="0" <generator class="hilo" <param name="table"hibernate_unique_key</param <param name="column"classB_nexthi</param <param name="max_lo"20</param </generator </id ... Also I've noticed that when I do the above the SchemaExport will not create all the columns - only classB_nexthi, is there something else im doing wrong. Thanks

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  • How do I generate a random string of up to a certain length?

    - by slavy13
    I would like to generate a random string (or a series of random strings, repetitions allowed) of length between 1 and n characters from some (finite) alphabet. Each string should be equally likely (in other words, the strings should be uniformly distributed). The uniformity requirement means that an algorithm like this doesn't work: alphabet = "abcdefghijklmnopqrstuvwxyz" len = rand(1, n) s = "" for(i = 0; i < len; ++i) s = s + alphabet[rand(0, 25)] (pseudo code, rand(a, b) returns a integer between a and b, inclusively, each integer equally likely) It doesn't work because shorter lengths are as likely as longer ones, meaning it's more likely to generate a shorter string than a longer one, so the result is not uniform.

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  • How do I generate a random time interval and add it to a mysql datetime using php?

    - by KeenLearner
    I have many rows in mysql table with datetime's in the format of: 2008-12-08 04:16:51 etc I'd like to generate a random time interval of anywhere between 30 seconds, and 3 days and add them to the time above. a) how do I generate a random time between 30 and 3 days? b) how do I add this time to the date time format above? I imagine i need to do a loop to pull out all the info, do the math in php, and then update the row... Any ideas?

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  • Why is using a Non-Random IV with CBC Mode a vulnerability?

    - by The Rook
    I understand the purpose of an IV. Specifically in CBC mode this insures that the first block of of 2 messages encrypted with the same key will never be identical. But why is it a vulnerability if the IV's are sequential? According to CWE-329 NON-Random IV's allow for the possibility of a dictionary attack. I know that in practice protocols like WEP make no effort to hide the IV. If the attacker has the IV and a cipher text message then this opens the door for a dictionary attack against the key. I don't see how a random iv changes this. (I know the attacks against wep are more complex than this.) What security advantage does a randomized iv have? Is this still a problem with an "Ideal Block Cipher"? (A perfectly secure block cipher with no possible weaknesses.)

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  • What could be causing Windows to randomnly reset the system time to a random time?

    - by Jonathan Dumaine
    My Windows 7 machine infuriates me. It cannot hold a date. At one point it all worked fine, but now it will decide that it needs to change the system time to a random time and date either in the future or past. There seems to be no correlation or set interval of when it happens. To remedy it I have: Correctly set the time in bios. Replaced the motherboard battery with a new CR2032 (even checked it with a multimeter). Tried disabling automatic internet synchronizing via "Date and Time" dialog. Stopped, restarted, left disabled the Windows Time service. Yet with all of these actions, the time will continue to change. Any ideas?

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  • Random BSODs on Win7 boot. Can't find a valid reason.

    - by 0plus1
    Hi, I bought and assembled a new pc: ASUS m4a785td-v EVO AMD x4 620 OCZ Black Edition 2x 2gb WD 500gb sata Win7 Ultimate 64bit fresh install BSOD on boot. Formatted, reinstalled, BSOD on install. Ran memtest - no errors. Ran Win7 install in safe mode. Installed, random BSOD on win7 startup, even in safe mode. Updated BIOS. Ran the win7 memtest (no error), booted after some tries and ran Prime95 blend test for 12 hours straight with no errors at all! When the pc has booted, win7 runs as smooth as possible, I've been playing STALKER for 4 hours straight with not a single hiccup. Using Blue Screen View I can see that every BSOD involves: ntoskrnl.exe Here are the dumps Any help would be greatly appreciated, this thing is driving me crazy.

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  • What could be causing Windows to randomly reset the system time to a random time?

    - by Jonathan Dumaine
    My Windows 7 machine infuriates me. It cannot hold a date. At one point it all worked fine, but now it will decide that it needs to change the system time to a random time and date, either in the future or past. There seems to be no correlation or set interval of when it happens. In attempt to remedy this, I have: Correctly set the time in BIOS. Replaced the motherboard battery with a new CR2032 (even checked it with a multimeter). Tried disabling automatic internet synchronizing via "Date and Time" dialog. Stopped, restarted, left disabled the Windows Time service. Yet with all of these actions, the time will continue to change. Any ideas?

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  • Apache crashing at random intervals. Can not find a reason in log files

    - by Nick Downton
    We are having an issue with a VPS running plesk 9.5 on ubuntu 8.04 At seemingly random intervals Apache will disappear and needs to be started manually. I have checked the apache error log, /var/log/messages, individual virtual host apache error files and cannot find anything that coincides with the time of the failure. dmesg is empty which is a bit odd. We have also had the psa service go down for no apparent reason but apache stay up. I'm at a loss to diagnose this really because all the log files I can find do not point to any issues. Are there any others I can look at? Memory usage sits at about 55% (out of 400mb) and it isn't a particularly high trafficed server. Any pointers as to where else I can find out what is going on would be very much appreciated. Nick

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  • is it okay to use random URLs instead of passwords?

    - by stew
    Is it considered "safe" to use URL constructed from random characters like this? http://example.com/EU3uc654/Photos I'd like to put some files/picture galleries on a webserver that are only to be accessed by a small group of users. My main concern is that the files should not get picked up by search-engines or curious power-users that poke around my site. I've set up an .htaccess file, just to notice that clicking on http://user:pass@url/ links doesn't work well with some browsers/email clients, prompting dialogs and warnings messages that confuse my not-too-computer-savy users.

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