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• Ivy and Snapshots (Nexus)

  - by Uberpuppy

  Hey folks, I'm using ant, ivy and nexus repo manager to build and store my artifacts. I managed to get everything working: dependency resolution and publishing. Until I hit a problem... (of course!). I was publishing to a 'release' repo in nexus, which is locked to 'disable redeploy' (even if you change the setting to 'allow redeploy' (really lame UI there imo). You can imagine how pissed off I was getting when my changes weren't updating through the repo before I realised that this was happening. Anyway, I now have to switch everything to use a 'Snapshot' repo in nexus. Problem is that this messes up my publish. I've tried a variety of things, including extensive googling, and haven't got anywhere whatsoever. The error I get is a bad PUT request, error code 400. Can someone who has got this working please give me a pointer on what I'm missing. Many thanks, Alastair fyi, here's my config: Note that I have removed any attempts at getting snapshots to work as I didn't know what was actually (potentially) useful and what was complete guff. This is therefore the working release-only setup. Also, please note that I've added the XXX-API ivy.xml for info only. I can't even get the xxx-common to publish (and that doesn't even have dependencies). Ant task: <target name="publish" depends="init-publish"> <property name="project.generated.ivy.file" value="${project.artifact.dir}/ivy.xml"/> <property name="project.pom.file" value="${project.artifact.dir}/${project.handle}.pom"/> <echo message="Artifact dir: ${project.artifact.dir}"/> <ivy:deliver deliverpattern="${project.generated.ivy.file}" organisation="${project.organisation}" module="${project.artifact}" status="integration" revision="${project.revision}" pubrevision="${project.revision}" /> <ivy:resolve /> <ivy:makepom ivyfile="${project.generated.ivy.file}" pomfile="${project.pom.file}"/> <ivy:publish resolver="${ivy.omnicache.publisher}" module="${project.artifact}" organisation="${project.organisation}" revision="${project.revision}" pubrevision="${project.revision}" pubdate="now" overwrite="true" publishivy="true" status="integration" artifactspattern="${project.artifact.dir}/[artifact]-[revision](-[classifier]).[ext]" /> </target> Couple of ivy files to give an idea of internal dependencies: XXX-Common project: <ivy-module version="2.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="http://ant.apache.org/ivy/schemas/ivy.xsd"> <info organisation="com.myorg.xxx" module="xxx_common" status="integration" revision="1.0"> </info> <publications> <artifact name="xxx_common" type="jar" ext="jar"/> <artifact name="xxx_common" type="pom" ext="pom"/> </publications> <dependencies> </dependencies> </ivy-module> XXX-API project: <ivy-module version="2.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="http://ant.apache.org/ivy/schemas/ivy.xsd"> <info organisation="com.myorg.xxx" module="xxx_api" status="integration" revision="1.0"> </info> <publications> <artifact name="xxx_api" type="jar" ext="jar"/> <artifact name="xxx_api" type="pom" ext="pom"/> </publications> <dependencies> <dependency org="com.myorg.xxx" name="xxx_common" rev="1.0" transitive="true" /> </dependencies> </ivy-module> IVY Settings.xml: <ivysettings> <properties file="${ivy.project.dir}/project.properties" /> <settings defaultResolver="chain" defaultConflictManager="all" /> <credentials host="${ivy.credentials.host}" realm="Sonatype Nexus Repository Manager" username="${ivy.credentials.username}" passwd="${ivy.credentials.passwd}" /> <caches> <cache name="ivy.cache" basedir="${ivy.cache.dir}" /> </caches> <resolvers> <ibiblio name="xxx_publisher" m2compatible="true" root="${ivy.xxx.publish.url}" /> <chain name="chain"> <url name="xxx"> <ivy pattern="${ivy.xxx.repo.url}/com/myorg/xxx/[module]/[revision]/ivy-[revision].xml" /> <artifact pattern="${ivy.xxx.repo.url}/com/myorg/xxx/[module]/[revision]/[artifact]-[revision].[ext]" /> </url> <ibiblio name="xxx" m2compatible="true" root="${ivy.xxx.repo.url}"/> <ibiblio name="public" m2compatible="true" root="${ivy.master.repo.url}" /> <url name="com.springsource.repository.bundles.release"> <ivy pattern="http://repository.springsource.com/ivy/bundles/release/[organisation]/[module]/[revision]/[artifact]-[revision].[ext]" /> <artifact pattern="http://repository.springsource.com/ivy/bundles/release/[organisation]/[module]/[revision]/[artifact]-[revision].[ext]" /> </url> <url name="com.springsource.repository.bundles.external"> <ivy pattern="http://repository.springsource.com/ivy/bundles/external/[organisation]/[module]/[revision]/[artifact]-[revision].[ext]" /> <artifact pattern="http://repository.springsource.com/ivy/bundles/external/[organisation]/[module]/[revision]/[artifact]-[revision].[ext]" /> </url> </chain> </resolvers> </ivysettings>

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• What pseudo-operators exist in Perl 5?

  - by Chas. Owens

  I am currently documenting all of Perl 5's operators (see the perlopref GitHub project) and I have decided to include Perl 5's pseudo-operators as well. To me, a pseudo-operator in Perl is anything that looks like an operator, but is really more than one operator or a some other piece of syntax. I have documented the four I am familiar with already: ()= the countof operator =()= the goatse/countof operator ~~ the scalar context operator }{ the Eskimo-kiss operator What other names exist for these pseudo-operators, and do you know of any pseudo-operators I have missed? =head1 Pseudo-operators There are idioms in Perl 5 that appear to be operators, but are really a combination of several operators or pieces of syntax. These pseudo-operators have the precedence of the constituent parts. =head2 ()= X =head3 Description This pseudo-operator is the list assignment operator (aka the countof operator). It is made up of two items C<()>, and C<=>. In scalar context it returns the number of items in the list X. In list context it returns an empty list. It is useful when you have something that returns a list and you want to know the number of items in that list and don't care about the list's contents. It is needed because the comma operator returns the last item in the sequence rather than the number of items in the sequence when it is placed in scalar context. It works because the assignment operator returns the number of items available to be assigned when its left hand side has list context. In the following example there are five values in the list being assigned to the list C<($x, $y, $z)>, so C<$count> is assigned C<5>. my $count = my ($x, $y, $z) = qw/a b c d e/; The empty list (the C<()> part of the pseudo-operator) triggers this behavior. =head3 Example sub f { return qw/a b c d e/ } my $count = ()= f(); #$count is now 5 my $string = "cat cat dog cat"; my $cats = ()= $string =~ /cat/g; #$cats is now 3 print scalar( ()= f() ), "\n"; #prints "5\n" =head3 See also L</X = Y> and L</X =()= Y> =head2 X =()= Y This pseudo-operator is often called the goatse operator for reasons better left unexamined; it is also called the list assignment or countof operator. It is made up of three items C<=>, C<()>, and C<=>. When X is a scalar variable, the number of items in the list Y is returned. If X is an array or a hash it it returns an empty list. It is useful when you have something that returns a list and you want to know the number of items in that list and don't care about the list's contents. It is needed because the comma operator returns the last item in the sequence rather than the number of items in the sequence when it is placed in scalar context. It works because the assignment operator returns the number of items available to be assigned when its left hand side has list context. In the following example there are five values in the list being assigned to the list C<($x, $y, $z)>, so C<$count> is assigned C<5>. my $count = my ($x, $y, $z) = qw/a b c d e/; The empty list (the C<()> part of the pseudo-operator) triggers this behavior. =head3 Example sub f { return qw/a b c d e/ } my $count =()= f(); #$count is now 5 my $string = "cat cat dog cat"; my $cats =()= $string =~ /cat/g; #$cats is now 3 =head3 See also L</=> and L</()=> =head2 ~~X =head3 Description This pseudo-operator is named the scalar context operator. It is made up of two bitwise negation operators. It provides scalar context to the expression X. It works because the first bitwise negation operator provides scalar context to X and performs a bitwise negation of the result; since the result of two bitwise negations is the original item, the value of the original expression is preserved. With the addition of the Smart match operator, this pseudo-operator is even more confusing. The C<scalar> function is much easier to understand and you are encouraged to use it instead. =head3 Example my @a = qw/a b c d/; print ~~@a, "\n"; #prints 4 =head3 See also L</~X>, L</X ~~ Y>, and L<perlfunc/scalar> =head2 X }{ Y =head3 Description This pseudo-operator is called the Eskimo-kiss operator because it looks like two faces touching noses. It is made up of an closing brace and an opening brace. It is used when using C<perl> as a command-line program with the C<-n> or C<-p> options. It has the effect of running X inside of the loop created by C<-n> or C<-p> and running Y at the end of the program. It works because the closing brace closes the loop created by C<-n> or C<-p> and the opening brace creates a new bare block that is closed by the loop's original ending. You can see this behavior by using the L<B::Deparse> module. Here is the command C<perl -ne 'print $_;'> deparsed: LINE: while (defined($_ = <ARGV>)) { print $_; } Notice how the original code was wrapped with the C<while> loop. Here is the deparsing of C<perl -ne '$count++ if /foo/; }{ print "$count\n"'>: LINE: while (defined($_ = <ARGV>)) { ++$count if /foo/; } { print "$count\n"; } Notice how the C<while> loop is closed by the closing brace we added and the opening brace starts a new bare block that is closed by the closing brace that was originally intended to close the C<while> loop. =head3 Example # count unique lines in the file FOO perl -nle '$seen{$_}++ }{ print "$_ => $seen{$_}" for keys %seen' FOO # sum all of the lines until the user types control-d perl -nle '$sum += $_ }{ print $sum' =head3 See also L<perlrun> and L<perlsyn> =cut

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• Java implementing Exception Handling

  - by user69514

  I am trying to implement an OutOfStockException for when the user attempts to buy more items than there are available. I'm not sure if my implementation is correct. Does this look OK to you? public class OutOfStockException extends Exception { public OutOfStockException(){ super(); } public OutOfStockException(String s){ super(s); } } This is the class where I need to test it: import javax.swing.JOptionPane; public class SwimItems { static final int MAX = 100; public static void main (String [] args) { Item [] items = new Item[MAX]; int numItems; numItems = fillFreebies(items); numItems += fillTaxable(items,numItems); numItems += fillNonTaxable(items,numItems); sellStuff(items, numItems); } private static int num(String which) { int n = 0; do { try{ n=Integer.parseInt(JOptionPane.showInputDialog("Enter number of "+which+" items to add to stock:")); } catch(NumberFormatException nfe){ System.out.println("Number Format Exception in num method"); } } while (n < 1 || n > MAX/3); return n; } private static int fillFreebies(Item [] list) { int n = num("FREEBIES"); for (int i = 0; i < n; i++) try{ list [i] = new Item(JOptionPane.showInputDialog("What freebie item will you give away?"), Integer.parseInt(JOptionPane.showInputDialog("How many do you have?"))); } catch(NumberFormatException nfe){ System.out.println("Number Format Exception in fillFreebies method"); } catch(ArrayIndexOutOfBoundsException e){ System.out.println("Array Index Out Of Bounds Exception in fillFreebies method"); } return n; } private static int fillTaxable(Item [] list, int number) { int n = num("Taxable Items"); for (int i = number ; i < n + number; i++) try{ list [i] = new TaxableItem(JOptionPane.showInputDialog("What taxable item will you sell?"), Double.parseDouble(JOptionPane.showInputDialog("How much will you charge (not including tax) for each?")), Integer.parseInt(JOptionPane.showInputDialog("How many do you have?"))); } catch(NumberFormatException nfe){ System.out.println("Number Format Exception in fillTaxable method"); } catch(ArrayIndexOutOfBoundsException e){ System.out.println("Array Index Out Of Bounds Exception in fillTaxable method"); } return n; } private static int fillNonTaxable(Item [] list, int number) { int n = num("Non-Taxable Items"); for (int i = number ; i < n + number; i++) try{ list [i] = new SaleItem(JOptionPane.showInputDialog("What non-taxable item will you sell?"), Double.parseDouble(JOptionPane.showInputDialog("How much will you charge for each?")), Integer.parseInt(JOptionPane.showInputDialog("How many do you have?"))); } catch(NumberFormatException nfe){ System.out.println("Number Format Exception in fillNonTaxable method"); } catch(ArrayIndexOutOfBoundsException e){ System.out.println("Array Index Out Of Bounds Exception in fillNonTaxable method"); } return n; } private static String listEm(Item [] all, int n, boolean numInc) { String list = "Items: "; for (int i = 0; i < n; i++) { try{ list += "\n"+ (i+1)+". "+all[i].toString() ; if (all[i] instanceof SaleItem) list += " (taxable) "; if (numInc) list += " (Number in Stock: "+all[i].getNum()+")"; } catch(ArrayIndexOutOfBoundsException e){ System.out.println("Array Index Out Of Bounds Exception in listEm method"); } catch(NullPointerException npe){ System.out.println("Null Pointer Exception in listEm method"); } } return list; } private static void sellStuff (Item [] list, int n) { int choice; do { try{ choice = Integer.parseInt(JOptionPane.showInputDialog("Enter item of choice: "+listEm(list, n, false))); } catch(NumberFormatException nfe){ System.out.println("Number Format Exception in sellStuff method"); } }while (JOptionPane.showConfirmDialog(null, "Another customer?")==JOptionPane.YES_OPTION); JOptionPane.showMessageDialog(null, "Remaining "+listEm(list, n, true)); } }

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• Class member functions instantiated by traits

  - by Jive Dadson

  I am reluctant to say I can't figure this out, but I can't figure this out. I've googled and searched Stack Overflow, and come up empty. The abstract, and possibly overly vague form of the question is, how can I use the traits-pattern to instantiate non-virtual member functions? The question came up while modernizing a set of multivariate function optimizers that I wrote more than 10 years ago. The optimizers all operate by selecting a straight-line path through the parameter space away from the current best point (the "update"), then finding a better point on that line (the "line search"), then testing for the "done" condition, and if not done, iterating. There are different methods for doing the update, the line-search, and conceivably for the done test, and other things. Mix and match. Different update formulae require different state-variable data. For example, the LMQN update requires a vector, and the BFGS update requires a matrix. If evaluating gradients is cheap, the line-search should do so. If not, it should use function evaluations only. Some methods require more accurate line-searches than others. Those are just some examples. The original version instantiates several of the combinations by means of virtual functions. Some traits are selected by setting mode bits that are tested at runtime. Yuck. It would be trivial to define the traits with #define's and the member functions with #ifdef's and macros. But that's so twenty years ago. It bugs me that I cannot figure out a whiz-bang modern way. If there were only one trait that varied, I could use the curiously recurring template pattern. But I see no way to extend that to arbitrary combinations of traits. I tried doing it using boost::enable_if, etc.. The specialized state information was easy. I managed to get the functions done, but only by resorting to non-friend external functions that have the this-pointer as a parameter. I never even figured out how to make the functions friends, much less member functions. The compiler (VC++ 2008) always complained that things didn't match. I would yell, "SFINAE, you moron!" but the moron is probably me. Perhaps tag-dispatch is the key. I haven't gotten very deeply into that. Surely it's possible, right? If so, what is best practice? UPDATE: Here's another try at explaining it. I want the user to be able to fill out an order (manifest) for a custom optimizer, something like ordering off of a Chinese menu - one from column A, one from column B, etc.. Waiter, from column A (updaters), I'll have the BFGS update with Cholesky-decompositon sauce. From column B (line-searchers), I'll have the cubic interpolation line-search with an eta of 0.4 and a rho of 1e-4, please. Etc... UPDATE: Okay, okay. Here's the playing-around that I've done. I offer it reluctantly, because I suspect it's a completely wrong-headed approach. It runs okay under vc++ 2008. #include <boost/utility.hpp> #include <boost/type_traits/integral_constant.hpp> namespace dj { struct CBFGS { void bar() {printf("CBFGS::bar %d\n", data);} CBFGS(): data(1234){} int data; }; template<class T> struct is_CBFGS: boost::false_type{}; template<> struct is_CBFGS<CBFGS>: boost::true_type{}; struct LMQN {LMQN(): data(54.321){} void bar() {printf("LMQN::bar %lf\n", data);} double data; }; template<class T> struct is_LMQN: boost::false_type{}; template<> struct is_LMQN<LMQN> : boost::true_type{}; struct default_optimizer_traits { typedef CBFGS update_type; }; template<class traits> class Optimizer; template<class traits> void foo(typename boost::enable_if<is_LMQN<typename traits::update_type>, Optimizer<traits> >::type& self) { printf(" LMQN %lf\n", self.data); } template<class traits> void foo(typename boost::enable_if<is_CBFGS<typename traits::update_type>, Optimizer<traits> >::type& self) { printf("CBFGS %d\n", self.data); } template<class traits = default_optimizer_traits> class Optimizer{ friend typename traits::update_type; //friend void dj::foo<traits>(typename Optimizer<traits> & self); // How? public: //void foo(void); // How??? void foo() { dj::foo<traits>(*this); } void bar() { data.bar(); } //protected: // How? typedef typename traits::update_type update_type; update_type data; }; } // namespace dj int main_() { dj::Optimizer<> opt; opt.foo(); opt.bar(); std::getchar(); return 0; }

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• Where is the virtual function call overhead?

  - by Semen Semenych

  Hello everybody, I'm trying to benchmark the difference between a function pointer call and a virtual function call. To do this, I have written two pieces of code, that do the same mathematical computation over an array. One variant uses an array of pointers to functions and calls those in a loop. The other variant uses an array of pointers to a base class and calls its virtual function, which is overloaded in the derived classes to do absolutely the same thing as the functions in the first variant. Then I print the time elapsed and use a simple shell script to run the benchmark many times and compute the average run time. Here is the code: #include <iostream> #include <cstdlib> #include <ctime> #include <cmath> using namespace std; long long timespecDiff(struct timespec *timeA_p, struct timespec *timeB_p) { return ((timeA_p->tv_sec * 1000000000) + timeA_p->tv_nsec) - ((timeB_p->tv_sec * 1000000000) + timeB_p->tv_nsec); } void function_not( double *d ) { *d = sin(*d); } void function_and( double *d ) { *d = cos(*d); } void function_or( double *d ) { *d = tan(*d); } void function_xor( double *d ) { *d = sqrt(*d); } void ( * const function_table[4] )( double* ) = { &function_not, &function_and, &function_or, &function_xor }; int main(void) { srand(time(0)); void ( * index_array[100000] )( double * ); double array[100000]; for ( long int i = 0; i < 100000; ++i ) { index_array[i] = function_table[ rand() % 4 ]; array[i] = ( double )( rand() / 1000 ); } struct timespec start, end; clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &start); for ( long int i = 0; i < 100000; ++i ) { index_array[i]( &array[i] ); } clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &end); unsigned long long time_elapsed = timespecDiff(&end, &start); cout << time_elapsed / 1000000000.0 << endl; } and here is the virtual function variant: #include <iostream> #include <cstdlib> #include <ctime> #include <cmath> using namespace std; long long timespecDiff(struct timespec *timeA_p, struct timespec *timeB_p) { return ((timeA_p->tv_sec * 1000000000) + timeA_p->tv_nsec) - ((timeB_p->tv_sec * 1000000000) + timeB_p->tv_nsec); } class A { public: virtual void calculate( double *i ) = 0; }; class A1 : public A { public: void calculate( double *i ) { *i = sin(*i); } }; class A2 : public A { public: void calculate( double *i ) { *i = cos(*i); } }; class A3 : public A { public: void calculate( double *i ) { *i = tan(*i); } }; class A4 : public A { public: void calculate( double *i ) { *i = sqrt(*i); } }; int main(void) { srand(time(0)); A *base[100000]; double array[100000]; for ( long int i = 0; i < 100000; ++i ) { array[i] = ( double )( rand() / 1000 ); switch ( rand() % 4 ) { case 0: base[i] = new A1(); break; case 1: base[i] = new A2(); break; case 2: base[i] = new A3(); break; case 3: base[i] = new A4(); break; } } struct timespec start, end; clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &start); for ( int i = 0; i < 100000; ++i ) { base[i]->calculate( &array[i] ); } clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &end); unsigned long long time_elapsed = timespecDiff(&end, &start); cout << time_elapsed / 1000000000.0 << endl; } My system is LInux, Fedora 13, gcc 4.4.2. The code is compiled it with g++ -O3. The first one is test1, the second is test2. Now I see this in console: [Ignat@localhost circuit_testing]$ ./test2 && ./test2 0.0153142 0.0153166 Well, more or less, I think. And then, this: [Ignat@localhost circuit_testing]$ ./test2 && ./test2 0.01531 0.0152476 Where are the 25% which should be visible? How can the first executable be even slower than the second one? I'm asking this because I'm doing a project which involves calling a lot of small functions in a row like this in order to compute the values of an array, and the code I've inherited does a very complex manipulation to avoid the virtual function call overhead. Now where is this famous call overhead?

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• C++ Mutexes and STL Lists Across Subclasses

  - by Genesis

  I am currently writing a multi-threaded C++ server using Poco and am now at the point where I need to be keeping information on which users are connected, how many connections each of them have, and given it is a proxy server, where each of those connections are proxying through to. For this purpose I have created a ServerStats class which holds an STL list of ServerUser objects. The ServerStats class includes functions which can add and remove objects from the list as well as find a user in the list an return a pointer to them so I can access member functions within any given ServerUser object in the list. The ServerUser class contains an STL list of ServerConnection objects and much like the ServerStats class it contains functions to add, remove and find elements within this list. Now all of the above is working but I am now trying to make it threadsafe. I have defined a Poco::FastMutex within the ServerStats class and can lock/unlock this in the appropriate places so that STL containers are not modified at the same time as being searched for example. I am however having an issue setting up mutexes within the ServerUser class and am getting the following compiler error: /root/poco/Foundation/include/Poco/Mutex.h: In copy constructor âServerUser::ServerUser(const ServerUser&)â: src/SocksServer.cpp:185: instantiated from âvoid __gnu_cxx::new_allocator<_Tp::construct(_Tp*, const _Tp&) [with _Tp = ServerUser]â /usr/include/c++/4.4/bits/stl_list.h:464: instantiated from âstd::_List_node<_Tp* std::list<_Tp, _Alloc::_M_create_node(const _Tp&) [with _Tp = ServerUser, _Alloc = std::allocator]â /usr/include/c++/4.4/bits/stl_list.h:1407: instantiated from âvoid std::list<_Tp, _Alloc::_M_insert(std::_List_iterator<_Tp, const _Tp&) [with _Tp = ServerUser, _Alloc = std::allocator]â /usr/include/c++/4.4/bits/stl_list.h:920: instantiated from âvoid std::list<_Tp, _Alloc::push_back(const _Tp&) [with _Tp = ServerUser, _Alloc = std::allocator]â src/SocksServer.cpp:301: instantiated from here /root/poco/Foundation/include/Poco/Mutex.h:164: error: âPoco::FastMutex::FastMutex(const Poco::FastMutex&)â is private src/SocksServer.cpp:185: error: within this context In file included from /usr/include/c++/4.4/x86_64-linux-gnu/bits/c++allocator.h:34, from /usr/include/c++/4.4/bits/allocator.h:48, from /usr/include/c++/4.4/string:43, from /root/poco/Foundation/include/Poco/Bugcheck.h:44, from /root/poco/Foundation/include/Poco/Foundation.h:147, from /root/poco/Net/include/Poco/Net/Net.h:45, from /root/poco/Net/include/Poco/Net/TCPServerParams.h:43, from src/SocksServer.cpp:1: /usr/include/c++/4.4/ext/new_allocator.h: In member function âvoid __gnu_cxx::new_allocator<_Tp::construct(_Tp*, const _Tp&) [with _Tp = ServerUser]â: /usr/include/c++/4.4/ext/new_allocator.h:105: note: synthesized method âServerUser::ServerUser(const ServerUser&)â first required here src/SocksServer.cpp: At global scope: src/SocksServer.cpp:118: warning: âstd::string getWord(std::string)â defined but not used make: * [/root/poco/SocksServer/obj/Linux/x86_64/debug_shared/SocksServer.o] Error 1 The code for the ServerStats, ServerUser and ServerConnection classes is below: class ServerConnection { public: bool continue_connection; int bytes_in; int bytes_out; string source_address; string destination_address; ServerConnection() { continue_connection = true; } ~ServerConnection() { } }; class ServerUser { public: string username; int connection_count; string client_ip; ServerUser() { } ~ServerUser() { } ServerConnection* addConnection(string source_address, string destination_address) { //FastMutex::ScopedLock lock(_connection_mutex); ServerConnection connection; connection.source_address = source_address; connection.destination_address = destination_address; client_ip = getWord(source_address, ":"); _connections.push_back(connection); connection_count++; return &_connections.back(); } void removeConnection(string source_address) { //FastMutex::ScopedLock lock(_connection_mutex); for(list<ServerConnection>::iterator it = _connections.begin(); it != _connections.end(); it++) { if(it->source_address == source_address) { it = _connections.erase(it); connection_count--; } } } void disconnect() { //FastMutex::ScopedLock lock(_connection_mutex); for(list<ServerConnection>::iterator it = _connections.begin(); it != _connections.end(); it++) { it->continue_connection = false; } } list<ServerConnection>* getConnections() { return &_connections; } private: list<ServerConnection> _connections; //UNCOMMENTING THIS LINE BREAKS IT: //mutable FastMutex _connection_mutex; }; class ServerStats { public: int current_users; ServerStats() { current_users = 0; } ~ServerStats() { } ServerUser* addUser(string username) { FastMutex::ScopedLock lock(_user_mutex); for(list<ServerUser>::iterator it = _users.begin(); it != _users.end(); it++) { if(it->username == username) { return &(*it); } } ServerUser newUser; newUser.username = username; _users.push_back(newUser); current_users++; return &_users.back(); } void removeUser(string username) { FastMutex::ScopedLock lock(_user_mutex); for(list<ServerUser>::iterator it = _users.begin(); it != _users.end(); it++) { if(it->username == username) { _users.erase(it); current_users--; break; } } } ServerUser* getUser(string username) { FastMutex::ScopedLock lock(_user_mutex); for(list<ServerUser>::iterator it = _users.begin(); it != _users.end(); it++) { if(it->username == username) { return &(*it); } } return NULL; } private: list<ServerUser> _users; mutable FastMutex _user_mutex; }; Now I have never used C++ for a project of this size or mutexes for that matter so go easy please :) Firstly, can anyone tell me why the above is causing a compiler error? Secondly, can anyone suggest a better way of storing the information I require? Bear in mind that I need to update this info whenever connections come or go and it needs to be global to the whole server.

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• Fail to analyze core dump with GDB when main.elf is dynamically linked (uses shared libs)

  - by dscTobi

  Hi all. I'm trying to analyze core dump, but i get following result: GNU gdb 6.6.0.20070423-cvs 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 "--host=mipsel-linux --target=mipsel-linux-uclibc". (gdb) file main.elf Reading symbols from /home/tobi/main.elf...Reading symbols from /home/tobi/main.dbg...done. done. (gdb) core-file /srv/tobi/core warning: .dynamic section for "/lib/libpthread.so.0" is not at the expected address (wrong library or version mismatch?) Error while mapping shared library sections: /lib/libdl.so.0: No such file or directory. Error while mapping shared library sections: /lib/librt.so.0: No such file or directory. Error while mapping shared library sections: /lib/libm.so.0: No such file or directory. Error while mapping shared library sections: /lib/libstdc++.so.6: No such file or directory. Error while mapping shared library sections: /lib/libc.so.0: No such file or directory. warning: .dynamic section for "/lib/libgcc_s.so.1" is not at the expected address (wrong library or version mismatch?) Error while mapping shared library sections: /lib/ld-uClibc.so.0: No such file or directory. Reading symbols from /lib/libpthread.so.0...done. Loaded symbols for /lib/libpthread.so.0 Symbol file not found for /lib/libdl.so.0 Symbol file not found for /lib/librt.so.0 Symbol file not found for /lib/libm.so.0 Symbol file not found for /lib/libstdc++.so.6 Symbol file not found for /lib/libc.so.0 Reading symbols from /lib/libgcc_s.so.1...done. Loaded symbols for /lib/libgcc_s.so.1 Symbol file not found for /lib/ld-uClibc.so.0 warning: Unable to find dynamic linker breakpoint function. GDB will be unable to debug shared library initializers and track explicitly loaded dynamic code. Core was generated by 'root/main.elf'. Program terminated with signal 11, Segmentation fault. #0 0x0046006c in NullPtr (parse_p=0x2ac9dc80, result_sym_p=0x13e3d6c "") at folder/my1.c:1624 1624 *ptr += 13; (gdb) bt #0 0x0046006c in NullPtr (parse_p=0x2ac9dc80, result_sym_p=0x13e3d6c "") at folder/my1.c:1624 #1 0x0047a31c in fn1 (line_ptr=0x2ac9dd18 "ccore_null_pointer", target_ptr=0x13e3d6c "", result_ptr=0x2ac9dd14) at folder/my2.c:980 #2 0x0047b9d0 in fn2 (macro_ptr=0x0, rtn_exp_ptr=0x0) at folder/my3.c:1483 /... some functions .../ #8 0x2aab7f9c in __nptl_setxid () from /lib/libpthread.so.0 Backtrace stopped: frame did not save the PC (gdb) thread apply all bt Thread 159 (process 1093): #0 0x2aac15dc in _Unwind_GetCFA () from /lib/libpthread.so.0 #1 0x2afdfde8 in ?? () warning: GDB cant find the start of the function at 0x2afdfde8. GDB is unable to find the start of the function at 0x2afdfde8 and thus cant determine the size of that functions stack frame. This means that GDB may be unable to access that stack frame, or the frames below it. This problem is most likely caused by an invalid program counter or stack pointer. However, if you think GDB should simply search farther back from 0x2afdfde8 for code which looks like the beginning of a function, you can increase the range of the search using the set heuristic-fence-post command. Backtrace stopped: previous frame inner to this frame (corrupt stack?) Thread 158 (process 1051): #0 0x2aac17bc in pthread_mutexattr_getprioceiling () from /lib/libpthread.so.0 #1 0x2aac17a0 in pthread_mutexattr_getprioceiling () from /lib/libpthread.so.0 Backtrace stopped: previous frame identical to this frame (corrupt stack?) Thread 157 (process 1057): #0 0x2aabf908 in ?? () from /lib/libpthread.so.0 #1 0x00000000 in ?? () Thread 156 (process 1090): #0 0x2aac17bc in pthread_mutexattr_getprioceiling () from /lib/libpthread.so.0 #1 0x2aac17a0 in pthread_mutexattr_getprioceiling () from /lib/libpthread.so.0 Backtrace stopped: previous frame identical to this frame (corrupt stack?) Thread 155 (process 1219): #0 0x2aabf908 in ?? () from /lib/libpthread.so.0 #1 0x00000000 in ?? () Thread 154 (process 1218): #0 0x2aabfb44 in connect () from /lib/libpthread.so.0 #1 0x00000000 in ?? () Thread 153 (process 1096): #0 0x2abc92b4 in ?? () warning: GDB cant find the start of the function at 0x2abc92b4. #1 0x2abc92b4 in ?? () warning: GDB cant find the start of the function at 0x2abc92b4. Backtrace stopped: previous frame identical to this frame (corrupt stack?) Thread 152 (process 1170): #0 0x2aabfb44 in connect () from /lib/libpthread.so.0 #1 0x00000000 in ?? () If i make main.elf statically linked everything is OK and i can see bt of all threads. Any ideas?

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• Of these 3 methods for reading linked lists from shared memory, why is the 3rd fastest?

  - by Joseph Garvin

  I have a 'server' program that updates many linked lists in shared memory in response to external events. I want client programs to notice an update on any of the lists as quickly as possible (lowest latency). The server marks a linked list's node's state_ as FILLED once its data is filled in and its next pointer has been set to a valid location. Until then, its state_ is NOT_FILLED_YET. I am using memory barriers to make sure that clients don't see the state_ as FILLED before the data within is actually ready (and it seems to work, I never see corrupt data). Also, state_ is volatile to be sure the compiler doesn't lift the client's checking of it out of loops. Keeping the server code exactly the same, I've come up with 3 different methods for the client to scan the linked lists for changes. The question is: Why is the 3rd method fastest? Method 1: Round robin over all the linked lists (called 'channels') continuously, looking to see if any nodes have changed to 'FILLED': void method_one() { std::vector<Data*> channel_cursors; for(ChannelList::iterator i = channel_list.begin(); i != channel_list.end(); ++i) { Data* current_item = static_cast<Data*>(i->get(segment)->tail_.get(segment)); channel_cursors.push_back(current_item); } while(true) { for(std::size_t i = 0; i < channel_list.size(); ++i) { Data* current_item = channel_cursors[i]; ACQUIRE_MEMORY_BARRIER; if(current_item->state_ == NOT_FILLED_YET) { continue; } log_latency(current_item->tv_sec_, current_item->tv_usec_); channel_cursors[i] = static_cast<Data*>(current_item->next_.get(segment)); } } } Method 1 gave very low latency when then number of channels was small. But when the number of channels grew (250K+) it became very slow because of looping over all the channels. So I tried... Method 2: Give each linked list an ID. Keep a separate 'update list' to the side. Every time one of the linked lists is updated, push its ID on to the update list. Now we just need to monitor the single update list, and check the IDs we get from it. void method_two() { std::vector<Data*> channel_cursors; for(ChannelList::iterator i = channel_list.begin(); i != channel_list.end(); ++i) { Data* current_item = static_cast<Data*>(i->get(segment)->tail_.get(segment)); channel_cursors.push_back(current_item); } UpdateID* update_cursor = static_cast<UpdateID*>(update_channel.tail_.get(segment)); while(true) { if(update_cursor->state_ == NOT_FILLED_YET) { continue; } ::uint32_t update_id = update_cursor->list_id_; Data* current_item = channel_cursors[update_id]; if(current_item->state_ == NOT_FILLED_YET) { std::cerr << "This should never print." << std::endl; // it doesn't continue; } log_latency(current_item->tv_sec_, current_item->tv_usec_); channel_cursors[update_id] = static_cast<Data*>(current_item->next_.get(segment)); update_cursor = static_cast<UpdateID*>(update_cursor->next_.get(segment)); } } Method 2 gave TERRIBLE latency. Whereas Method 1 might give under 10us latency, Method 2 would inexplicably often given 8ms latency! Using gettimeofday it appears that the change in update_cursor-state_ was very slow to propogate from the server's view to the client's (I'm on a multicore box, so I assume the delay is due to cache). So I tried a hybrid approach... Method 3: Keep the update list. But loop over all the channels continuously, and within each iteration check if the update list has updated. If it has, go with the number pushed onto it. If it hasn't, check the channel we've currently iterated to. void method_three() { std::vector<Data*> channel_cursors; for(ChannelList::iterator i = channel_list.begin(); i != channel_list.end(); ++i) { Data* current_item = static_cast<Data*>(i->get(segment)->tail_.get(segment)); channel_cursors.push_back(current_item); } UpdateID* update_cursor = static_cast<UpdateID*>(update_channel.tail_.get(segment)); while(true) { for(std::size_t i = 0; i < channel_list.size(); ++i) { std::size_t idx = i; ACQUIRE_MEMORY_BARRIER; if(update_cursor->state_ != NOT_FILLED_YET) { //std::cerr << "Found via update" << std::endl; i--; idx = update_cursor->list_id_; update_cursor = static_cast<UpdateID*>(update_cursor->next_.get(segment)); } Data* current_item = channel_cursors[idx]; ACQUIRE_MEMORY_BARRIER; if(current_item->state_ == NOT_FILLED_YET) { continue; } found_an_update = true; log_latency(current_item->tv_sec_, current_item->tv_usec_); channel_cursors[idx] = static_cast<Data*>(current_item->next_.get(segment)); } } } The latency of this method was as good as Method 1, but scaled to large numbers of channels. The problem is, I have no clue why. Just to throw a wrench in things: if I uncomment the 'found via update' part, it prints between EVERY LATENCY LOG MESSAGE. Which means things are only ever found on the update list! So I don't understand how this method can be faster than method 2. The full, compilable code (requires GCC and boost-1.41) that generates random strings as test data is at: http://pastebin.com/e3HuL0nr

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• Anchor bug on IE9, anchor hitbox overlapped

  - by user1456399

  The menu below works just fine in Firefox and Chrome, but in IE9, but hitbox for the "HOME" anchor is being covered partially by the list item behind it except for the actual test, and a single horizontal pixel line at the top and bottom of the button. Can anyone see what I'm missing? Code to follow: index.html <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html;charset=utf-8" > <title>Navigation</title> <style> .menu-container { width:960px; height:45px; margin:0 auto; position:relative; z-index:2; background-color: #3d3d3d; margin-bottom: 20px; } .menu-navigation { font-family:Arial, Helvetica, sans-serif; font-size:13px; list-style:none; padding:0; margin:0; text-align: right; font-size: 0; /* Removes whitespace between <li> */ } .menu-navigation > li { display:inline; margin:0; border-left:solid 1px #242424; background-color:transparent; font-size: 12px; padding: 15px 0 15px 0; } .menu-navigation > li:hover, .menu-navigation > li.current-menu-item { background-color:#202020; } .menu-navigation > li.active, .menu-navigation > li.active:hover { background-color:#131313; } .menu-navigation > li a { text-decoration:none; color:#bbbbbb; } .menu-navigation > li a:hover { color:#efefef; } .menu-navigation > li span a { color:#ffffff; } .menu-navigation > li a:focus { outline:none; } .menu-navigation > li.menu-item-parent > span, .menu-navigation > li > span > a { text-transform:uppercase; outline:0; text-decoration:none; color:#ffffff; text-shadow:1px 1px 1px #000000; line-height: 45px; display: inline-block; height: 45px; padding: 0 20px 0 20px; } .menu-navigation > li.menu-item-parent > span { background:url("../img/down.png") no-repeat right center; } .menu-navigation > li.menu-item-parent > span:hover, .menu-navigation > li > span > a:hover { cursor:pointer; } </style> </head> <body> <div class="menu-container"> <ul class="menu-navigation"> <li><span><a href="#">This is a link</a></span></li> <li><span><a href="#">This is a link</a></span></li> <li class="menu-item-parent"><span>Not a link</span></li> <li class="menu-item-parent"><span>Not a link</span></li> <li class="menu-item-parent"><span>Not a link</span></li> </ul> </div> </body> </html> EDIT: Alright, I've changed the code to isolate the issue, and narrowed down the problem CSS. Simply adding a background image fixes the issue. The code is set up so it styles so the hit boxes for all the menu items are the same regardless if there's a link in them or not to facilitate an "onClick" drop down on those menu items without anchors. Refer to lines 81 - 86. Remove those lines (just a background image), and the hit box issue is seen in the menu items "NOT A LINK" as well. Further, the act of adding a background image fixes the hit box issue of "THIS IS A LINK" menu items. Simply add the following snippet to the CSS: .menu-navigation > li > span > a { background:url("../img/down.png") no-repeat right center; } Adding a background image, even if there is no actual image, is changing something with regards to the hit box... I'm just not sure what...

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• Is there an equivalent to Java's ClassFileTransformer in .NET? (a way to replace a class)

  - by Alix

  I've been searching for this for quite a while with no luck so far. Is there an equivalent to Java's ClassFileTransformer in .NET? Basically, I want to create a class CustomClassFileTransformer (which in Java would implement the interface ClassFileTransformer) that gets called whenever a class is loaded, and is allowed to tweak it and replace it with the tweaked version. I know there are frameworks that do similar things, but I was looking for something more straightforward, like implementing my own ClassFileTransformer. Is it possible? EDIT #1. More details about why I need this: Basically, I have a C# application and I need to monitor the instructions it wants to run in order to detect read or write operations to fields (operations Ldfld and Stfld) and insert some instructions before the read/write takes place. I know how to do this (except for the part where I need to be invoked to replace the class): for every method whose code I want to monitor, I must: Get the method's MethodBody using MethodBase.GetMethodBody() Transform it to byte array with MethodBody.GetILAsByteArray(). The byte[] it returns contains the bytecode. Analyse the bytecode as explained here, possibly inserting new instructions or deleting/modifying existing ones by changing the contents of the array. Create a new method and use the new bytecode to create its body, with MethodBuilder.CreateMethodBody(byte[] il, int count), where il is the array with the bytecode. I put all these tweaked methods in a new class and use the new class to replace the one that was originally going to be loaded. An alternative to replacing classes would be somehow getting notified whenever a method is invoked. Then I'd replace the call to that method with a call to my own tweaked method, which I would tweak only the first time is invoked and then I'd put it in a dictionary for future uses, to reduce overhead (for future calls I'll just look up the method and invoke it; I won't need to analyse the bytecode again). I'm currently investigating ways to do this and LinFu looks pretty interesting, but if there was something like a ClassFileTransformer it would be much simpler: I just rewrite the class, replace it, and let the code run without monitoring anything. An additional note: the classes may be sealed. I want to be able to replace any kind of class, I cannot impose restrictions on their attributes. EDIT #2. Why I need to do this at runtime. I need to monitor everything that is going on so that I can detect every access to data. This applies to the code of library classes as well. However, I cannot know in advance which classes are going to be used, and even if I knew every possible class that may get loaded it would be a huge performance hit to tweak all of them instead of waiting to see whether they actually get invoked or not. POSSIBLE (BUT PRETTY HARDCORE) SOLUTION. In case anyone is interested (and I see the question has been faved, so I guess someone is), this is what I'm looking at right now. Basically I'd have to implement the profiling API and I'll register for the events that I'm interested in, in my case whenever a JIT compilation starts. An extract of the blogpost: In your ICorProfilerCallback2::ModuleLoadFinished callback, you call ICorProfilerInfo2::GetModuleMetadata to get a pointer to a metadata interface on that module. QI for the metadata interface you want. Search MSDN for "IMetaDataImport", and grope through the table of contents to find topics on the metadata interfaces. Once you're in metadata-land, you have access to all the types in the module, including their fields and function prototypes. You may need to parse metadata signatures and this signature parser may be of use to you. In your ICorProfilerCallback2::JITCompilationStarted callback, you may use ICorProfilerInfo2::GetILFunctionBody to inspect the original IL, and ICorProfilerInfo2::GetILFunctionBodyAllocator and then ICorProfilerInfo2::SetILFunctionBody to replace that IL with your own. The great news: I get notified when a JIT compilation starts and I can replace the bytecode right there, without having to worry about replacing the class, etc. The not-so-great news: you cannot invoke managed code from the API's callback methods, which makes sense but means I'm on my own parsing the IL code, etc, as opposed to be able to use Cecil, which would've been a breeze. I don't think there's a simpler way to do this without using AOP frameworks (such as PostSharp). If anyone has any other idea please let me know. I'm not marking the question as answered yet.

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• Strange things appear on running the program

  - by FILIaS

  Hey! I'm fixing a program but I'm facing a problem and I cant really realize what's the wrong on the code. I would appreciate any help. I didnt post all the code...but i think with this part you can get an idea of it. With the following function enter() I wanna add user commands' datas to a list. eg. user give the command: "enter james bond 007 gun" 'james' is supposed to be the name, 'bond' the surname, 007 the amount and the rest is the description. I use strtok in order to 'cut' the command,then i put each name on a temp array. Then i call InsertSort in order to put the datas on a linked list but in alphabetical order depending on the surname that users give. I wanna keep the list on order and put each time the elements on the right position. /* struct for all the datas that user enters on file*/ typedef struct catalog { char short_name[50]; char surname[50]; signed int amount; char description[1000]; struct catalog *next; }catalog,*catalogPointer; catalogPointer current; catalogPointer head = NULL; void enter(void)//user command: enter <name> <surname> <amount> <description> { int n,j=2,k=0; char temp[1500]; char command[1500]; while (command[j]!=' ' && command[j]!='\0') { temp[k]=command[j]; j++; k++; } temp[k]='\0'; char *curToken = strtok(temp," "); printf("temp is:%s \n",temp); char short_name[50],surname[50],description[1000]; signed int amount; //short_name=(char *)malloc(sizeof (char *)); //surname=(char *)malloc(sizeof (char *)); //description=(char *)malloc(sizeof (char *)); //amount=(int *)malloc(sizeof (int *)); printf("\nWhat you entered for saving:\n"); for (n = 0; curToken !='\0'; ++n) { if (curToken) { strncpy(short_name, curToken, sizeof (char *)); / } printf("Short Name: %s \n",short_name); curToken = strtok(NULL," "); if (curToken) strncpy(surname, curToken, sizeof (char *)); / printf("SurName: %s \n",surname); curToken = strtok(NULL," "); if (curToken) { char *chk; amount = (int) strtol(curToken, &chk, 10); if (!isspace(*chk) && *chk != 0) fprintf(stderr,"Warning: expected integer value for amount, received %s instead\n",curToken); } printf("Amount: %d \n",amount); curToken = strtok(NULL,"\0"); if (curToken) { strncpy(description, curToken, sizeof (char *)); } printf("Description: %s \n",description); break; } if (findEntryExists(head, surname) != NULL) printf("\nAn entry for <%s %s> is already in the catalog!\nNew entry not entered.\n",short_name,surname); else { printf("\nTry to entry <%s %s %d %s> in the catalog list!\n",short_name,surname,amount,description); InsertSort(&head,short_name, surname, amount, description); printf("\n**Entry done!**\n"); } // Maintain the list in alphabetical order by surname. } /********Uses special case code for the head end********/ void SortedInsert(catalog** headRef, catalogPointer newNode,char short_name[],char surname[],signed int amount,char description[]) { strcpy(newNode->short_name, short_name); strcpy(newNode->surname, surname); newNode->amount=amount; strcpy(newNode->description, description); // Special case for the head end if (*headRef == NULL||(*headRef)->surname >= newNode->surname) { newNode->next = *headRef; *headRef = newNode; } else { // Locate the node before the point of insertion catalogPointer current = *headRef; catalogPointer temp=current->next; while ( temp!=NULL ) { if(strcmp(temp->surname,newNode->surname)<0 ) current = temp; } newNode->next = temp; temp = newNode; } } // Given a list, change it to be in sorted order (using SortedInsert()). void InsertSort(catalog** headRef,char short_name[],char surname[],signed int amount,char description[]) { catalogPointer result = NULL; // build the answer here catalogPointer current = *headRef; // iterate over the original list catalogPointer next; while (current!=NULL) { next = current->next; // tricky - note the next pointer before we change it SortedInsert(&result,current,short_name,surname,amount,description); current = next; } *headRef = result; } Running the program I get these strange things (garbage?)... Choose your selection: enter james bond 007 gun Your command is: enter james bond 007 gun temp is:james What you entered for saving: Short Name: james SurName: Amount: 0 Description: 0T?? Try to entry james 0 0T?? in the catalog list! Entry done! Also I'm facing a problem on how to use the 'malloc' on this program. Thanks in advance. . .

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• linux thread synchronization

  - by johnnycrash

  I am new to linux and linux threads. I have spent some time googling to try to understand the differences between all the functions available for thread synchronization. I still have some questions. I have found all of these different types of synchronizations, each with a number of functions for locking, unlocking, testing the lock, etc. gcc atomic operations futexes mutexes spinlocks seqlocks rculocks conditions semaphores My current (but probably flawed) understanding is this: semaphores are process wide, involve the filesystem (virtually I assume), and are probably the slowest. Futexes might be the base locking mechanism used by mutexes, spinlocks, seqlocks, and rculocks. Futexes might be faster than the locking mechanisms that are based on them. Spinlocks dont block and thus avoid context swtiches. However they avoid the context switch at the expense of consuming all the cycles on a CPU until the lock is released (spinning). They should only should be used on multi processor systems for obvious reasons. Never sleep in a spinlock. The seq lock just tells you when you finished your work if a writer changed the data the work was based on. You have to go back and repeat the work in this case. Atomic operations are the fastest synch call, and probably are used in all the above locking mechanisms. You do not want to use atomic operations on all the fields in your shared data. You want to use a lock (mutex, futex, spin, seq, rcu) or a single atomic opertation on a lock flag when you are accessing multiple data fields. My questions go like this: Am I right so far with my assumptions? Does anyone know the cpu cycle cost of the various options? I am adding parallelism to the app so we can get better wall time response at the expense of running fewer app instances per box. Performances is the utmost consideration. I don't want to consume cpu with context switching, spinning, or lots of extra cpu cycles to read and write shared memory. I am absolutely concerned with number of cpu cycles consumed. Which (if any) of the locks prevent interruption of a thread by the scheduler or interrupt...or am I just an idiot and all synchonization mechanisms do this. What kinds of interruption are prevented? Can I block all threads or threads just on the locking thread's CPU? This question stems from my fear of interrupting a thread holding a lock for a very commonly used function. I expect that the scheduler might schedule any number of other workers who will likely run into this function and then block because it was locked. A lot of context switching would be wasted until the thread with the lock gets rescheduled and finishes. I can re-write this function to minimize lock time, but still it is so commonly called I would like to use a lock that prevents interruption...across all processors. I am writing user code...so I get software interrupts, not hardware ones...right? I should stay away from any functions (spin/seq locks) that have the word "irq" in them. Which locks are for writing kernel or driver code and which are meant for user mode? Does anyone think using an atomic operation to have multiple threads move through a linked list is nuts? I am thinking to atomicly change the current item pointer to the next item in the list. If the attempt works, then the thread can safely use the data the current item pointed to before it was moved. Other threads would now be moved along the list. futexes? Any reason to use them instead of mutexes? Is there a better way than using a condition to sleep a thread when there is no work? When using gcc atomic ops, specifically the test_and_set, can I get a performance increase by doing a non atomic test first and then using test_and_set to confirm? *I know this will be case specific, so here is the case. There is a large collection of work items, say thousands. Each work item has a flag that is initialized to 0. When a thread has exclusive access to the work item, the flag will be one. There will be lots of worker threads. Any time a thread is looking for work, they can non atomicly test for 1. If they read a 1, we know for certain that the work is unavailable. If they read a zero, they need to perform the atomic test_and_set to confirm. So if the atomic test_and_set is 500 cpu cycles because it is disabling pipelining, causes cpu's to communicate and L2 caches to flush/fill .... and a simple test is 1 cycle .... then as long as I had a better ratio of 500 to 1 when it came to stumbling upon already completed work items....this would be a win.* I hope to use mutexes or spinlocks to sparilngly protect sections of code that I want only one thread on the SYSTEM (not jsut the CPU) to access at a time. I hope to sparingly use gcc atomic ops to select work and minimize use of mutexes and spinlocks. For instance: a flag in a work item can be checked to see if a thread has worked it (0=no, 1=yes or in progress). A simple test_and_set tells the thread if it has work or needs to move on. I hope to use conditions to wake up threads when there is work. Thanks!

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• Arraylist is null; I cannot access books in the arraylist

  - by user3701380

  I am a beginner-intermediate java programmer and I am getting a null pointer exception from my arraylist. I am writing a bookstore program for APCS and when i add the book, it is supposed to add to the arraylist in the inventory class. But when i call a method to search for a book (e.g. by title), it shows that there isn't anything in the arraylist. //Here is my inventory class -- it has all methods for adding the book or searching for one The searching methods are in getBookByTitle, getBookByAuthor, and getBookByISBN and the method for adding a book is addBook package webbazonab; //Inventory Class //Bharath Senthil //Ansh Sikka import java.util.ArrayList; public class Inventory{ private ArrayList<Book> allBooks = new ArrayList<Book>(); private String bookTitles; private String bookAuthors; private String bookPrices; private String bookCopies; private String ISBNs; public Inventory() { } //@param double price, int copies, String bookTitle, String Author, String isbnNumber public void addBooks(Book addedBook){ allBooks.add(addedBook); } public boolean isAvailable(){ for(Book myBook : allBooks){ if(myBook.copiesLeft() == 0) return false; } return true; } public String populateTitle(){ for (Book titleBooks : allBooks){ bookTitles = titleBooks.getTitle() + "\n"; return bookTitles; } return bookTitles; } public String populateAuthor(){ for(Book authorBooks : allBooks){ bookAuthors = authorBooks.getAuthor() + "\n"; return bookAuthors; } return bookAuthors; } public String populatePrice(){ for (Book pricedBooks : allBooks){ bookPrices = String.valueOf(pricedBooks.getPrice()) + "\n"; } return "$" + bookPrices; } /** * * @return */ public String populateCopies(){ for (Book amtBooks : allBooks){ bookCopies = String.valueOf(amtBooks.copiesLeft()) + "\n"; return bookCopies; } return bookCopies; } public String populateISBN(){ for (Book isbnNums : allBooks){ ISBNs = isbnNums.getIsbn() + "\n"; return ISBNs; } return ISBNs; } @SuppressWarnings("empty-statement") public Book getBookByTitle(String titleSearch) { for(Book titleBook : allBooks) { if (titleBook.getTitle().equals(titleSearch)) { return titleBook; } } return null; } public Book getBookByISBN(String isbnSearch){ for(Book isbnBookSearches : allBooks){ if(isbnBookSearches.getIsbn().equals(isbnSearch)){ return isbnBookSearches; } } return null; } public Book getBookByAuthor(String authorSearch){ for(Book authorBookSearches : allBooks){ if(authorBookSearches.getAuthor().equals(authorSearch)){ return authorBookSearches; } } return null; } public void sort(){ for(int i = 0; i < allBooks.size(); i++) { for(int k = 0; k < allBooks.size(); k++) { if(((Book) allBooks.get(i)).getIsbn().compareTo(((Book) allBooks.get(k)).getIsbn()) < 1) { Book temp = (Book) allBooks.get(k); allBooks.set(k, allBooks.get(i)); allBooks.set(i, temp); } else if(((Book) allBooks.get(i)).getIsbn().compareTo(((Book) allBooks.get(k)).getIsbn()) > 1) { Book temp = (Book) allBooks.get(i); allBooks.set(i, allBooks.get(k)); allBooks.set(k, temp); } } } } public ArrayList<Book> getBooks(){ return allBooks; } } //The exception occurs when i call the method here (in another class): Inventory lib = new Inventory(); jTextField12.setText(lib.getBookByAuthor(authorSearch).getTitle()); Here is my book class if you need it package webbazonab; //Webbazon AB //Project By: Ansh Sikka and Bharath Senthil public class Book { private double myPrice; private String myTitle; private String bookAuthor; private String isbn; private int myCopies; public Book(double price, int copies, String bookTitle, String Author, String isbnNumber) { myPrice = price; myCopies = copies; myTitle = bookTitle; bookAuthor = Author; isbn = isbnNumber; } public double getPrice() { return myPrice; } public String getIsbn() { return isbn; } public String getTitle() { return myTitle; } public String getAuthor() { return bookAuthor; } public int copiesLeft(){ return myCopies; } public String notFound(){ return "The book you searched for could not be found!"; } public String toString() { return "Title: " + getTitle() + "\nAuthor: " + getAuthor() + "\nNumber of Available Books: " + copiesLeft() + "\nPrice: $" + getPrice(); } } Thanks!

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• Unable to start Android emulator > 1.5

  - by Cicatrice

  Hi ! I got this trace when I tried to launch android 1.6 or 2.1. Android 1.5 is working fine. I tried to reinstall each SDK, but there is no way to get it working. I created those AVD with Eclipse plugin. geo@geo-laptop:~> android/android-sdk-linux_86/tools/emulator -avd a16 *** glibc detected *** android/android-sdk-linux_86/tools/emulator: free(): invalid pointer: 0x45454545 *** ======= Backtrace: ========= /lib/libc.so.6(+0x6df7b)[0xb748cf7b] /lib/libc.so.6(cfree+0xd9)[0xb7491ac9] android/android-sdk-linux_86/tools/emulator[0x80db20c] android/android-sdk-linux_86/tools/emulator[0x840eb38] ======= Memory map: ======== 08048000-08246000 r-xp 00000000 08:06 5693701 /home/geo/android/android-sdk-linux_86/tools/emulator 08246000-08249000 rw-p 001fd000 08:06 5693701 /home/geo/android/android-sdk-linux_86/tools/emulator 08249000-08445000 rw-p 00000000 00:00 0 08445000-08447000 rwxp 00000000 00:00 0 08447000-0874c000 rw-p 00000000 00:00 0 [heap] ad8e9000-ada86000 rw-s 00000000 00:04 85229580 /SYSV00000000 (deleted) ada86000-adced000 rw-p 00000000 00:00 0 adced000-add0d000 rw-s 00000000 00:04 84770825 /SYSV0056a4d6 (deleted) add0d000-adde4000 r-xp 00000000 08:05 22591 /usr/lib/libasound.so.2.0.0 adde4000-adde5000 ---p 000d7000 08:05 22591 /usr/lib/libasound.so.2.0.0 adde5000-adde8000 r--p 000d7000 08:05 22591 /usr/lib/libasound.so.2.0.0 adde8000-adde9000 rw-p 000da000 08:05 22591 /usr/lib/libasound.so.2.0.0 adde9000-ade09000 rw-s 00000000 00:05 3268 /dev/snd/pcmC0D0p ade09000-b3e0b000 rw-p 00000000 00:00 0 b3e0b000-b3e0c000 ---p 00000000 00:00 0 b3e0c000-b55cd000 rw-p 00000000 00:00 0 b55cd000-b6dcd000 rwxp 00000000 00:00 0 b6dcd000-b6ea3000 rw-p 00000000 00:00 0 b6ea4000-b7205000 rw-p 00000000 00:00 0 b7205000-b7209000 r-xp 00000000 08:05 22491 /usr/lib/libXfixes.so.3.1.0 b7209000-b720a000 r--p 00003000 08:05 22491 /usr/lib/libXfixes.so.3.1.0 b720a000-b720b000 rw-p 00004000 08:05 22491 /usr/lib/libXfixes.so.3.1.0 b7212000-b7222000 rw-s 00000000 00:05 3269 /dev/snd/pcmC0D0c b7222000-b7226000 r-xp 00000000 08:05 22588 /usr/lib/alsa-lib/libasound_module_rate_speexrate.so b7226000-b7227000 r--p 00003000 08:05 22588 /usr/lib/alsa-lib/libasound_module_rate_speexrate.so b7227000-b7228000 rw-p 00004000 08:05 22588 /usr/lib/alsa-lib/libasound_module_rate_speexrate.so b7228000-b7229000 rw-s 81000000 00:05 3268 /dev/snd/pcmC0D0p b7229000-b722a000 r--s 80000000 00:05 3268 /dev/snd/pcmC0D0p b722a000-b722b000 rw-s 00000000 00:04 84738056 /SYSV0056a4d5 (deleted) b722b000-b7276000 r--p 00000000 08:05 85242 /var/cache/libx11/compose/l4_024_313cb605_00280cc0 b7276000-b72b5000 r--p 00000000 08:05 20724 /usr/lib/locale/en_US.utf8/LC_CTYPE b72b5000-b73d2000 r--p 00000000 08:05 101088 /usr/lib/locale/en_US.utf8/LC_COLLATE b73d2000-b73d9000 r-xp 00000000 08:05 22991 /usr/lib/libXrandr.so.2.2.0 b73d9000-b73da000 r--p 00006000 08:05 22991 /usr/lib/libXrandr.so.2.2.0 b73da000-b73db000 rw-p 00007000 08:05 22991 /usr/lib/libXrandr.so.2.2.0 b73db000-b73e4000 r-xp 00000000 08:05 4146 /usr/lib/libXrender.so.1.3.0 b73e4000-b73e5000 r--p 00008000 08:05 4146 /usr/lib/libXrender.so.1.3.0 b73e5000-b73e6000 rw-p 00009000 08:05 4146 /usr/lib/libXrender.so.1.3.0 b73e6000-b73f7000 r-xp 00000000 08:05 3705 /usr/lib/libXext.so.6.4.0 b73f7000-b73f8000 r--p 00010000 08:05 3705 /usr/lib/libXext.so.6.4.0 b73f8000-b73f9000 rw-p 00011000 08:05 3705 /usr/lib/libXext.so.6.4.0 b73f9000-b73fa000 rw-p 00000000 00:00 0 b73fa000-b73fc000 r-xp 00000000 08:05 8573 /usr/lib/libXau.so.6.0.0 b73fc000-b73fd000 r--p 00001000 08:05 8573 /usr/lib/libXau.so.6.0.0 b73fd000-b73fe000 rw-p 00002000 08:05 8573 /usr/lib/libXau.so.6.0.0 b73fe000-b73ff000 rw-p 00000000 00:00 0 b73ff000-b741d000 r-xp 00000000 08:05 3862 /usr/lib/libxcb.so.1.1.0 b741d000-b741e000 r--p 0001d000 08:05 3862 /usr/lib/libxcb.so.1.1.0 b741e000-b741f000 rw-p 0001e000 08:05 3862 /usr/lib/libxcb.so.1.1.0 b741f000-b7583000 r-xp 00000000 08:05 39690 /lib/libc-2.11.1.so b7583000-b7584000 ---p 00164000 08:05 39690 /lib/libc-2.11.1.so b7584000-b7586000 r--p 00164000 08:05 39690 /lib/libc-2.11.1.so b7586000-b7587000 rw-p 00166000 08:05 39690 /lib/libc-2.11.1.so b7587000-b758a000 rw-p 00000000 00:00 0 b758a000-b75a6000 r-xp 00000000 08:05 11519 /lib/libgcc_s.so.1 b75a6000-b75a7000 r--p 0001b000 08:05 11519 /lib/libgcc_s.so.1 b75a7000-b75a8000 rw-p 0001c000 08:05 11519 /lib/libgcc_s.so.1 b75a8000-b768b000 r-xp 00000000 08:05 85419 /usr/lib/libstdc++.so.6.0.14 b768b000-b768c000 ---p 000e3000 08:05 85419 /usr/lib/libstdc++.so.6.0.14 b768c000-b7690000 r--p 000e3000 08:05 85419 /usr/lib/libstdc++.so.6.0.14 b7690000-b7691000 rw-p 000e7000 08:05 85419 /usr/lib/libstdc++.so.6.0.14 b7691000-b7698000 rw-p 00000000 00:00 0 b7698000-b76c0000 r-xp 00000000 08:05 39698 /lib/libm-2.11.1.so b76c0000-b76c1000 r--p 00027000 08:05 39698 /lib/libm-2.11.1.so b76c1000-b76c2000 rw-p 00028000 08:05 39698 /lib/libm-2.11.1.so b76c2000-b76d9000 r-xp 00000000 08:05 39716 /lib/libpthread-2.11.1.so b76d9000-b76da000 r--p 00016000 08:05 39716 /lib/libpthread-2.11.1.so b76da000-b76db000 rw-p 00017000 08:05 39716 /lib/libpthread-2.11.1.so b76db000-b76de000 rw-p 00000000 00:00 0 b76de000-b76e1000 r-xp 00000000 08:05 39696 /lib/libdl-2.11.1.so b76e1000-b76e2000 r--p 00002000 08:05 39696 /lib/libdl-2.11.1.so b76e2000-b76e3000 rw-p 00003000 08:05 39696 /lib/libdl-2.11.1.so b76e3000-b76eb000 r-xp 00000000 08:05 39720 /lib/librt-2.11.1.so b76eb000-b76ec000 r--p 00007000 08:05 39720 /lib/librt-2.11.1.so b76ec000-b76ed000 rw-p 00008000 08:05 39720 /lib/librt-2.11.1.so b76ed000-b76ef000 r-xp 00000000 08:05 39725 /lib/libutil-2.11.1.so b76ef000-b76f0000 r--p 00001000 08:05 39725 /lib/libutil-2.11.1.so b76f0000-b76f1000 rw-p 00002000 08:05 39725 /lib/libutil-2.11.1.so b76f1000-b7828000 r-xp 00000000 08:05 4550 /usr/lib/libX11.so.6.3.0 b7828000-b7829000 r--p 00136000 08:05 4550 /usr/lib/libX11.so.6.3.0 b7829000-b782c000 rw-p 00137000 08:05 4550 /usr/lib/libX11.so.6.3.0 b782c000-b782d000 rw-s 81000000 00:05 3269 /dev/snd/pcmC0D0c b782d000-b782e000 r--s 80000000 00:05 3269 /dev/snd/pcmC0D0c b782e000-b782f000 rw-s 00000000 00:04 82771979 /SYSV0056a4d7 (deleted) b782f000-b7839000 r-xp 00000000 08:05 22208 /usr/lib/libXcursor.so.1.0.2 b7839000-b783a000 r--p 00009000 08:05 22208 /usr/lib/libXcursor.so.1.0.2 b783a000-b783b000 rw-p 0000a000 08:05 22208 /usr/lib/libXcursor.so.1.0.2 b783b000-b783c000 r--p 00000000 08:05 20194 /usr/lib/locale/en_US.utf8/LC_NUMERIC b783c000-b783d000 r--p 00000000 08:05 100190 /usr/lib/locale/en_US.utf8/LC_TIME b783d000-b783e000 r--p 00000000 08:05 100189 /usr/lib/locale/en_US.utf8/LC_MONETARY[1] 24082 abort android/android-sdk-linux_86/tools/emulator -avd a16

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• Memory limit for running external executables within Asp.net

  - by itsbalur

  I am using WkhtmltoPdf in my C# web application running in .NET 4.0 to generate PDFs from HTML files. In general everything works fine except when the size of the HTML file is below 250KB. Once the HTML file size increases beyond that, the process which runs the wkhtmltopdf.exe gives an exception as below. On the Task Manager, I have seen that the Memory value for the wkhtmltopdf.exe process does not increase beyond a value of 40,096 K, which I believe is the reason why the process is abandoned in between. How can we configure such that the memory limit for external exes can be increased? Is there any other way of solving this issue? More info: When I run the conversion from the command line directly, the PDF is generated fine. So, its unlikely to be a problem with WkhtmlToPdf. The error is from localhost. I have tried the same on the DEV server, with the same result. Exception: > [Exception: Loading pages (1/6) [> > ] 0% [======> ] > 10% [======> ] 11% > [=======> ] 13% > [=========> ] 15% > [==========> ] 18% > [============> ] 20% > [=============> ] 22% > [==============> ] 24% > [===============> ] 26% > [=================> ] 29% > [==================> ] 31% > [===================> ] 33% > [=====================> ] 35% > [======================> ] 37% > [========================> ] 40% > [=========================> ] 42% > [==========================> ] 44% > [============================> ] 47% > [=============================> ] 49% > [==============================> ] 51% > [============================================================] 100% > Counting pages (2/6) > [============================================================] Object > 1 of 1 Resolving links (4/6) > [============================================================] Object > 1 of 1 Loading headers and footers (5/6) > Printing pages (6/6) [> > ] Preparing [=> > ] Page 1 of 49 [==> > ] Page 2 of 49 [===> > ] Page 3 of 49 [====> > ] Page 4 of 49 [======> > ] Page 5 of 49 [=======> > ] Page 6 of 49 [========> > ] Page 7 of 49 [=========> > ] Page 8 of 49 [==========> > ] Page 9 of 49 [============> > ] Page 10 of 49 [=============> > ] Page 11 of 49 [==============> > ] Page 12 of 49 [===============> > ] Page 13 of 49 [================> > ] Page 14 of 49 [==================> > ] Page 15 of 49 [===================> > ] Page 16 of 49 [====================> > ] Page 17 of 49 [=====================> > ] Page 18 of 49 [======================> > ] Page 19 of 49 [========================> > ] Page 20 of 49 [=========================> > ] Page 21 of 49 [==========================> > ] Page 22 of 49 [===========================> > ] Page 23 of 49 [============================> > ] Page 24 of 49 [==============================> > ] Page 25 of 49 [===============================> > ] Page 26 of 49 [=================================> > ] Page 27 of 49 [==================================> > ] Code that I use: var fileName = " - "; var wkhtmlDir = ConfigurationManager.AppSettings[Constants.AppSettings.ExportToPdfExecutablePath]; var wkhtml = ConfigurationManager.AppSettings[Constants.AppSettings.ExportToPdfExecutablePath] + "\\wkhtmltopdf.exe"; var p = new Process(); string switches = ""; switches += "--print-media-type "; switches += "--margin-top 10mm --margin-bottom 10mm --margin-right 5mm --margin-left 5mm "; switches += "--page-size A4 "; switches += "--disable-smart-shrinking "; var startInfo = new ProcessStartInfo { CreateNoWindow = true, FileName = wkhtml, Arguments = switches + " " + url + " " + fileName, UseShellExecute = false, RedirectStandardOutput = true, RedirectStandardError = true, RedirectStandardInput=true, WorkingDirectory=wkhtmlDir }; p.StartInfo = startInfo; p.Start();

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• CSS Menu loses focus when part of jquery hover()

  - by Steve Syfuhs

  I have the following html (viewable at www.communityftw.com) <table width="100%"> <tr> <td style="text-align: left"> <!-- 2008.3.1314.35 --><span id="headerSearch1_sb_form_q_wrapper" class="RadInput_Default" style="white-space:nowrap;"><input value="language..." type="text" size="20" id="headerSearch1_sb_form_q_text" name="headerSearch1_sb_form_q_text" class="riTextBox riEmpty sw_qboxTop" name="q" style="width:140px;" /><input id="headerSearch1_sb_form_q" name="ctl00$headerSearch1$sb_form_q" class="rdfd_" style="visibility:hidden;margin:-18px 0 0 0;width:1px;height:1px;overflow:hidden;border:0;padding:0;" type="text" value="" /><input id="headerSearch1_sb_form_q_ClientState" name="headerSearch1_sb_form_q_ClientState" type="hidden" /></span> <input type="submit" name="ctl00$headerSearch1$sb_form_go" value="" id="headerSearch1_sb_form_go" class="sw_qbtnTop" /> </td> <td style="text-align: left"> <ul id="menu"> <li class="languageContainer"> <div> <a href="#" id="languageField"> <img src="/images/flags/ca.png" alt="Canada" /> Canada (English)</a> </div> <ul id="language"> <li><a href="#" id="A1"> <img src="/images/flags/ca.png" alt="Canada" /> Canada (French)</a> </li> <li><a href="#" id="A2"> <img src="/images/flags/us.png" alt="United States" /> United States</a> </li> <li><a href="#" id="A3"> <img src="/images/flags/de.png" alt="Germany" /> Germany</a> </li> <li><a href="#" id="A4"> <img src="/images/flags/fr.png" alt="France" /> France</a> </li> <li><a href="#" id="A5"> <img src="/images/flags/ru.png" alt="Russia" /> Russia</a> </li> <li class="last"> <img alt="" src="images/langLocDrop_r4_c1.png" /> </li> </ul> </li> </ul> </td> </tr> </table> Javascript/jquery $('#slide').animate({ top: '-=34' }, 1000); $("#slide").hover(function () { $(this).animate({ top: '+=34' }); }, function () { $(this).animate({ top: '-=34' }); }); menu { margin: 0px; padding: 0px; list-style: none; display: inline-block; float: left; z-index: 1000; } menu a { color: #dc2525; text-decoration: none; } menu li { background: none repeat scroll 0 0; cursor: pointer; float: left; position: relative; } menu li a:hover { color: orange; } menu ul { padding: 0px; margin: 0px; display: block; display: inline; } menu li ul { position: absolute; left: -15px; top: 0px; margin-top: 20px; width: 170px; line-height: 16px; background-image: url(/images/langLocDrop_r2_c1.png); display: none; } menu li:hover ul { display: block; } menu li ul li { display: block; margin: 5px 20px; padding: 5px 0px; border-top: dotted 1px #606060; list-style-type: none; } menu li ul li:first-child { border-top: none; } menu li ul li a { display: block; } menu li ul li a:hover { color: orange; } .languageContainer div { display: inline; padding: 5px; } languageField img { display: inline; vertical-align: middle; } language img { display: inline; } menu .last { background: transparent none repeat scroll 0% 0%; margin: 0px; padding: 0px; border: none; position: relative; border: none; height: 0px; } What I'm trying to do is have a menu mostly hidden at the top except when you mouse over it, and then have a submenu (just css driven) pop out when you mouse over the language. What is happening though is that when I move onto the language list, and I go past Germany (~50% down the list?), the hover() loses focus and closes the original menu, which closes the language menu. Any idea's what is causing the issue? Any ideas how to fix the issue? I have tried the hoverIntent() plugin as well to no avail.

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• Hi i have a c programming doubt in the implementation of hash table?

  - by aks

  Hi i have a c programming doubt in the implementation of hash table? I have implemented the hash table for storing some strings? I am having problem while dealing with hash collisons. I am following chaining link-list approach to overcome the same? But, somehow my code is behaving differently. I am not able to debug the same? Can somebody help? This is what i am facing: Say first time, i insert a string called gaur. My hash map calculates the index as 0 and inserts the string successfully. However, when another string whose hash map also when calculates turns out to be 0, my previous value gets overrridden i.e. gaur will be replaced by new string. This is my code: struct list { char *string; struct list *next; }; struct hash_table { int size; /* the size of the table */ struct list **table; /* the table elements */ }; struct hash_table *create_hash_table(int size) { struct hash_table *new_table; int i; if (size<1) return NULL; /* invalid size for table */ /* Attempt to allocate memory for the table structure */ if ((new_table = malloc(sizeof(struct hash_table))) == NULL) { return NULL; } /* Attempt to allocate memory for the table itself */ if ((new_table->table = malloc(sizeof(struct list *) * size)) == NULL) { return NULL; } /* Initialize the elements of the table */ for(i=0; i<size; i++) new_table->table[i] = '\0'; /* Set the table's size */ new_table->size = size; return new_table; } unsigned int hash(struct hash_table *hashtable, char *str) { unsigned int hashval = 0; int i = 0; for(; *str != '\0'; str++) { hashval += str[i]; i++; } return (hashval % hashtable->size); } struct list *lookup_string(struct hash_table *hashtable, char *str) { printf("\n enters in lookup_string \n"); struct list * new_list; unsigned int hashval = hash(hashtable, str); /* Go to the correct list based on the hash value and see if str is * in the list. If it is, return return a pointer to the list element. * If it isn't, the item isn't in the table, so return NULL. */ for(new_list = hashtable->table[hashval]; new_list != NULL;new_list = new_list->next) { if (strcmp(str, new_list->string) == 0) return new_list; } printf("\n returns NULL in lookup_string \n"); return NULL; } int add_string(struct hash_table *hashtable, char *str) { printf("\n enters in add_string \n"); struct list *new_list; struct list *current_list; unsigned int hashval = hash(hashtable, str); printf("\n hashval = %d", hashval); /* Attempt to allocate memory for list */ if ((new_list = malloc(sizeof(struct list))) == NULL) { printf("\n enters here \n"); return 1; } /* Does item already exist? */ current_list = lookup_string(hashtable, str); if (current_list == NULL) { printf("\n DEBUG Purpose \n"); printf("\n NULL \n"); } /* item already exists, don't insert it again. */ if (current_list != NULL) { printf("\n Item already present...\n"); return 2; } /* Insert into list */ printf("\n Inserting...\n"); new_list->string = strdup(str); new_list->next = NULL; //new_list->next = hashtable->table[hashval]; if(hashtable->table[hashval] == NULL) { hashtable->table[hashval] = new_list; } else { struct list * temp_list = hashtable->table[hashval]; while(temp_list->next!=NULL) temp_list = temp_list->next; temp_list->next = new_list; hashtable->table[hashval] = new_list; } return 0; }

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• Showing ImageView next to TextView in a ListView

  - by KDEx

  So I have a listview that is displaying correctly. When the item is "turned on" the text is white and when it's turned off it's grey. That part all functions great. However when I add the ImageView into the mix I get a null pointer exception. I don't understand why. I've tried using bitmaps as well and get the same problem. Here is some code: @Override public void bindView(View view, Context context, Cursor cursor) { TextView rRule = (TextView) view.findViewById(R.id.rule_text); TextView rType = (TextView) view.findViewById(R.id.rule_type); ImageView iChecked = (ImageView) view.findViewById(R.id.checkBox); String ruleName = cursor.getString(1); int ruleType = cursor.getInt(2); String ruleEnabled = cursor.getString(3); switch (ruleType) { /*...some irrelevant code */ } if (ruleEnabled.equals("true")) { rRule.setTypeface(null, Typeface.BOLD); rRule.setTextColor(Color.WHITE); iChecked.setVisibility(View.VISIBLE); //line 271 } else if (ruleEnabled.equals("false")) { rRule.setTypeface(null, Typeface.NORMAL); rRule.setTextColor(Color.GRAY); iChecked.setVisibility(View.GONE); } rRule.setText(ruleName); } Per request the error log: (Sorry was under the impression null pointers dont say anything helpful..I know the error is the imageview) 06-29 10:29:02.777: E/AndroidRuntime(29516): FATAL EXCEPTION: main 06-29 10:29:02.777: E/AndroidRuntime(29516): java.lang.NullPointerException 06-29 10:29:02.777: E/AndroidRuntime(29516): at com.company.app.DefaultRulesList$RulesAdapter.bindView(DefaultRulesList.java:271) 06-29 10:29:02.777: E/AndroidRuntime(29516): at com.company.app.DefaultRulesList$RulesAdapter.newView(DefaultRulesList.java:284) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.widget.CursorAdapter.getView(CursorAdapter.java:246) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.widget.AbsListView.obtainView(AbsListView.java:2033) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.widget.ListView.makeAndAddView(ListView.java:1772) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.widget.ListView.fillDown(ListView.java:672) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.widget.ListView.fillFromTop(ListView.java:732) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.widget.ListView.layoutChildren(ListView.java:1625) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.widget.AbsListView.onLayout(AbsListView.java:1863) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.view.View.layout(View.java:11278) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.view.ViewGroup.layout(ViewGroup.java:4224) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1628) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1486) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.widget.LinearLayout.onLayout(LinearLayout.java:1399) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.view.View.layout(View.java:11278) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.view.ViewGroup.layout(ViewGroup.java:4224) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.widget.FrameLayout.onLayout(FrameLayout.java:431) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.view.View.layout(View.java:11278) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.view.ViewGroup.layout(ViewGroup.java:4224) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1628) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1486) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.widget.LinearLayout.onLayout(LinearLayout.java:1399) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.view.View.layout(View.java:11278) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.view.ViewGroup.layout(ViewGroup.java:4224) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.widget.FrameLayout.onLayout(FrameLayout.java:431) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.view.View.layout(View.java:11278) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.view.ViewGroup.layout(ViewGroup.java:4224) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1489) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2442) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.os.Handler.dispatchMessage(Handler.java:99) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.os.Looper.loop(Looper.java:137) 06-29 10:29:02.777: E/AndroidRuntime(29516): at android.app.ActivityThread.main(ActivityThread.java:4424) 06-29 10:29:02.777: E/AndroidRuntime(29516): at java.lang.reflect.Method.invokeNative(Native Method) 06-29 10:29:02.777: E/AndroidRuntime(29516): at java.lang.reflect.Method.invoke(Method.java:511) 06-29 10:29:02.777: E/AndroidRuntime(29516): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 06-29 10:29:02.777: E/AndroidRuntime(29516): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 06-29 10:29:02.777: E/AndroidRuntime(29516): at dalvik.system.NativeStart.main(Native Method) Code for iChecked (where the id is called) <ImageView android:id="@+id/checkBox" android:padding="2dip" android:layout_width="wrap_content" android:layout_height="wrap_content" android:background="@android:drawable/checkbox_on_background"/>

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• Link List Implementation Help - Visual C++

  - by Greenhouse Gases

  Hi there I'm trying to implement a link list which stores the city name (though you will see this commented out as I need to resolve the issue of not being able to use string and needing to use a primitive data type instead during the declaration), longitude, latitude and of course a pointer to the next node in the chain. I am new to the Visual C++ environment and my brain is somewhat scrambled after coding for several straight hours today so I wondered if anyone could help resolve the 2 errors I am getting (ignore the #include syntax as I had to change them to avoid the browser interpreting html!): 1U08221.obj : error LNK2028: unresolved token (0A000298) "public: __thiscall Locations::Locations(void)" (??0Locations@@$$FQAE@XZ) referenced in function "int __clrcall main(cli::array^)" (?main@@$$HYMHP$01AP$AAVString@System@@@Z) 1U08221.obj : error LNK2019: unresolved external symbol "public: __thiscall Locations::Locations(void)" (??0Locations@@$$FQAE@XZ) referenced in function "int __clrcall main(cli::array^)" (?main@@$$HYMHP$01AP$AAVString@System@@@Z) The code for my header file is here: include string struct locationNode { //char[10] nodeCityName; double nodeLati; double nodeLongi; locationNode* Next; }; class Locations { private: int size; public: Locations(); // constructor for the class locationNode* Head; int Add(locationNode* Item); }; and here is the code for the file containing the main method: // U08221.cpp : main project file. include "stdafx.h" include "Locations.h" include iostream include string using namespace std; int n = 0; int x; string cityNameInput; bool acceptedInput = false; int Locations::Add(locationNode *NewItem) { locationNode *Sample = new locationNode; Sample = NewItem; Sample-Next = Head; Head = Sample; return size++; } void CorrectCase(string name) // Correct upper and lower case letters of input { x = name.size(); int firstLetVal = name[0], letVal; n = 1; // variable for name index from second letter onwards if((name[0] 90) && (name[0] < 123)) // First letter is lower case { firstLetVal = firstLetVal - 32; // Capitalise first letter name[0] = firstLetVal; } while(n <= x - 1) { if((name[n] = 65) && (name[n] <= 90)) { letVal = name[n] + 32; name[n] = letVal; } n++; } cityNameInput = name; } void nameValidation(string name) { n = 0; // start from first letter x = name.size(); while(!acceptedInput) { if((name[n] = 65) && (name[n] <= 122)) // is in the range of letters { while(n <= x - 1) { while((name[n] =91) && (name[n] <=97)) // ERROR!! { cout << "Please enter a valid city name" << endl; cin name; } n++; } } else { cout << "Please enter a valid city name" << endl; cin name; } if(n <= x - 1) { acceptedInput = true; } } cityNameInput = name; } int main(array ^args) { cout << "Enter a city name" << endl; cin cityNameInput; nameValidation(cityNameInput); // check is made up of valid characters CorrectCase(cityNameInput); // corrects name to standard format of capitalised first letter, and lower case subsequent letters cout << cityNameInput; cin cityNameInput; Locations::Locations(); Locations *Parts = new Locations(); locationNode *Part; Part = new locationNode; //Part-nodeCityName = "London"; Part-nodeLati = 87; Part-nodeLongi = 80; Parts-Add(Part); } I am familiar with the concepts but somewhat inexperienced with OOP so am making some silly errors that you can never find when you've stared at something too long. Any help you can offer will be appreciated! Thanks

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• c++ to vb.net , problem with callback function

  - by johan

  I'm having a hard time here trying to find a solution for my problem. I'm trying to convert a client API funktion from C++ to VB.NET, and i think have some problems with the callback function. parts of the C++ code: typedef struct{ BYTE m_bRemoteChannel; BYTE m_bSendMode; BYTE m_nImgFormat; // =0 cif ; = 1 qcif char *m_sIPAddress; char *m_sUserName; char *m_sUserPassword; BOOL m_bUserCheck; HWND m_hShowVideo; }CLIENT_VIDEOINFO, *PCLIENT_VIDEOINFO; CPLAYER_API LONG __stdcall MP4_ClientStart(PCLIENT_VIDEOINFO pClientinfo,void(CALLBACK *ReadDataCallBack)(DWORD nPort,UCHAR *pPacketBuffer,DWORD nPacketSize)); void CALLBACK ReadDataCallBack(DWORD nPort,UCHAR *pPacketBuffer,DWORD nPacketSize) { TRACE("%d\n",nPacketSize); } ..... aa5.m_sUserName = "123"; aa5.m_sUserPassword="w"; aa5.m_bUserCheck = TRUE; MP4_ClientSetTTL(64); nn1 = MP4_ClientStart(&aa5,ReadDataCallBack); if (nn1 == -1) { MessageBox("error"); return; } SDK description: MP4_ClientStart This function starts a connection. The format of the call is: LONG __stdcall MP4_ClientStart(PCLIENT_VIDEOINFO pClientinfo, void(*ReadDataCallBack)(DWORD nChannel,UCHAR *pPacketBuffer,DWORD nPacketSize)) Parameters pClientinfo holds the information. of this connection. nChannel holds the channel of card. pPacketBuffer holds the pointer to the receive buffer. nPacketSize holds the length of the receive buffer. Return Values If the function succeeds the return value is the context of this connection. If the function fails the return value is -1. Remarks typedef struct{ BYTE m_bRemoteChannel; BYTE m_bSendMode; BYTE m_bImgFormat; char *m_sIPAddress; char *m_sUserName; char *m_sUserPassword; BOOL m_bUserCheck; HWND m_hShowVideo; } CLIENT_VIDEOINFO, * PCLIENT_VIDEOINFO; m_bRemoteChannel holds the channel which the client wants to connect to. m_bSendMode holds the network mode of the connection. m_bImgFormat : Image format, 0 is main channel video, 1 is sub channel video m_sIPAddress holds the IP address of the server. m_sUserName holds the user’s name. m_sUserPassword holds the user’s password. m_bUserCheck holds the value whether sends the user’s name and password or not. m_hShowVideo holds Handle for this video window. If m_hShowVideo holds NULL, the client can be record only without decoder. If m_bUserCheck is FALSE, we will send m_sUserName and m_sUserPassword as NULL, else we will send each 50 bytes. The length of m_sIPAddress and m_sUserName must be more than 50 bytes. ReadDataCallBack: When the library receives a packet from a server, this callback is called. My VB.Net code: Imports System.Runtime.InteropServices Public Class Form1 Const WM_USER = &H400 Public Structure CLIENT_VIDEOINFO Public m_bRemoteChannel As Byte Public m_bSendMode As Byte Public m_bImgFormat As Byte Public m_sIPAddress As String Public m_sUserName As String Public m_sUserPassword As String Public m_bUserCheck As Boolean Public m_hShowVideo As Long 'hWnd End Structure Public Declare Function MP4_ClientSetNetPort Lib "hikclient.dll" (ByVal dServerPort As Integer, ByVal dClientPort As Integer) As Boolean Public Declare Function MP4_ClientStartup Lib "hikclient.dll" (ByVal nMessage As UInteger, ByVal hWnd As System.IntPtr) As Boolean <DllImport("hikclient.dll")> Public Shared Function MP4_ClientStart(ByVal Clientinfo As CLIENT_VIDEOINFO, ByRef ReadDataCallBack As CALLBACKdel) As Long End Function Public Delegate Sub CALLBACKdel(ByVal nPort As Long, <MarshalAs(UnmanagedType.LPArray)> ByRef pPacketBuffer As Byte(), ByVal nPacketSize As Long) Public Sub CALLBACK(ByVal nPort As Long, <MarshalAs(UnmanagedType.LPArray)> ByRef pPacketBuffer As Byte(), ByVal nPacketSize As Long) End Sub Public mydel As New CALLBACKdel(AddressOf CALLBACK) Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Dim Clientinfo As New CLIENT_VIDEOINFO() Clientinfo.m_bRemoteChannel = 0 Clientinfo.m_bSendMode = 0 Clientinfo.m_bImgFormat = 0 Clientinfo.m_sIPAddress = "193.168.1.100" Clientinfo.m_sUserName = "1" Clientinfo.m_sUserPassword = "a" Clientinfo.m_bUserCheck = False Clientinfo.m_hShowVideo = Me.Handle 'Nothing MP4_ClientSetNetPort(850, 850) MP4_ClientStartup(WM_USER + 1, Me.Handle) MP4_ClientStart(Clientinfo, mydel) End Sub End Class here is some other examples of the code in: C# http://blog.csdn.net/nenith1981/archive/2007/09/17/1787692.aspx VB ://read.pudn.com/downloads70/sourcecode/graph/250633/MD%E5%AE%A2%E6%88%B7%E7%AB%AF%28VB%29/hikclient.bas__.htm ://read.pudn.com/downloads70/sourcecode/graph/250633/MD%E5%AE%A2%E6%88%B7%E7%AB%AF%28VB%29/Form1.frm__.htm Delphi ://read.pudn.com/downloads91/sourcecode/multimedia/streaming/349759/Delphi_client/Unit1.pas__.htm

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• Linked lists in Java - Help with writing methods

  - by user368241

  Representation of a string in linked lists In every intersection in the list there will be 3 fields : The letter itself. The number of times it appears consecutively. A pointer to the next intersection in the list. The following class CharNode represents a intersection in the list : public class CharNode { private char _data; private int _value; private charNode _next; public CharNode (char c, int val, charNode n) { _data = c; _value = val; _next = n; } public charNode getNext() { return _next; } public void setNext (charNode node) { _next = node; } public int getValue() { return _value; } public void setValue (int v) { value = v; } public char getData() { return _data; } public void setData (char c) { _data = c; } } The class StringList represents the whole list : public class StringList { private charNode _head; public StringList() { _head = null; } public StringList (CharNode node) { _head = node; } } Add methods to the class StringList according to the details : (I will add methods gradually according to my specific questions) (Pay attention, these are methods from the class String and we want to fulfill them by the representation of a string by a list as explained above) Pay attention to all the possible error cases. Write what is the time complexity and space complexity of every method that you wrote. Make sure the methods you wrote are effective. It is NOT allowed to use ready classes of Java. It is NOT allowed to move to string and use string operations. 1) public int indexOf (int ch) - returns the index in the string it is operated on of the first appeareance of the char "ch". If the char "ch" doesn't appear in the string, returns -1. If the value of fromIndex isn't in the range, returns -1. Here is my try : public int indexOf (int ch) { int count = 0; charNode pos = _head; if (pos == null ) { return -1; } for (pos = _head; pos!=null && pos.getData()!=ch; pos = pos.getNext()) { count = count + pos.getValue(); } if (pos==null) return -1; return count; } Time complexity = O(N) Space complexity = O(1) EDIT : I have a problem. I tested it in BlueJ and if the char ch doesn't appear it returns -1 but if it does, it always returns 0 and I don't understand why... I am confused. How can the compiler know that the value is the number of times the letter appears consecutively? Can I assume this because its given on the question or what? If it's true and I can assume this, then my code should be correct right? Ok I just spoke with my instructor and she said it isn't required to write it in the exercise but in order for me to test that it indeed works, I need to open a new class and write a code for making a list so that the the value of every node is the number of times the letter appears consecutively. Can someone please assist me? So I will copy+paste to BlueJ and this way I will be able to test all the methods. Meanwhile I am moving on to the next methods. 2) public int indexOf (int ch, int fromIndex) - returns the index in the string it is operated on of the first appeareance of the char "ch", as the search begins in the index "fromIndex". If the char "ch" doesn't appear in the string, returns -1. If the value of fromIndex doesn't appear in the range, returns -1. Here is my try: public int indexOf (int ch, int fromIndex) { int count = 0, len=0, i; charNode pos = _head; CharNode cur = _head; for (pos = _head; pos!=null; pos = pos.getNext()) { len = len+1; } if (fromIndex<0 || fromIndex>=len) return -1; for (i=0; i<fromIndex; i++) { cur = cur.getNext(); } if (cur == null ) { return -1; } for (cur = _head; cur!=null && cur.getData()!=ch; cur = cur.getNext()) { count = count + cur.getValue(); } if (cur==null) return -1; return count; } Time complexity = O(N) ? Space complexity = O(1) 3) public StringList concat (String str) - returns a string that consists of the string that it is operated on and in its end the string "str" is concatenated. Here is my try : public StringList concat (String str) { String str = ""; charNode pos = _head; if (str == null) return -1; for (pos = _head; pos!=null; pos = pos.getNext()) { str = str + pos.getData(); } str = str + "str"; return str; } Time complexity = O(N) Space complexity = O(1)

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• Swap image with jquery and show zoom image

  - by Neil Bradley

  Hi there, On my site I have 4 thumbnail product images that when clicked on swap the main image. This part is working okay. However, on the main image I'm also trying to use the jQZoom script. The zoom script works for the most part, except that the zoomed image always displays the zoom of the first image, rather than the one selected. This can be seen in action here; http://www.wearecapital.com/productdetails-new.asp?id=6626 I was wondering if someone might be able to suggest a solution? My code for the page is here; <% if session("qstring") = "" then session("qstring") = "&amp;rf=latest" maxProducts = 6 prodID = request("id") if prodID = "" or not isnumeric(prodid) then response.Redirect("listproducts.asp?err=1" & session("qstring")) else prodId = cint(prodId) end if SQL = "Select * from products,subcategories,labels where subcat_id = prod_subcategory and label_id = prod_label and prod_id = " & prodID set conn = server.CreateObject("ADODB.connection") conn.Open(Application("DATABASE")) set rs = conn.Execute(SQL) if rs.eof then ' product is not valid name = "Error - product id " & prodID & " is not available" else image1 = rs.fields("prod_image1") image1Desc = rs.fields("prod_image1Desc") icon = rs.fields("prod_icon") subcat = rs.fields("prod_subcategory") image2 = rs.fields("prod_image2") image2Desc = rs.fields("prod_image2Desc") image3 = rs.fields("prod_image3") image3Desc = rs.fields("prod_image3Desc") image4 = rs.fields("prod_image4") image4Desc = rs.fields("prod_image4Desc") zoomimg = rs.Fields("prod_zoomimg") zoomimg2 = rs.Fields("prod_zoomimg2") zoomimg3 = rs.Fields("prod_zoomimg3") zoomimg4 = rs.Fields("prod_zoomimg4") thumb1 = rs.fields("prod_preview1").value thumb2 = rs.fields("prod_preview2").value thumb3 = rs.fields("prod_preview3").value thumb4 = rs.fields("prod_preview4").value end if set rs = nothing conn.Close set conn = nothing %> <!-- #include virtual="/includes/head-product.asp" --> <body id="detail"> <!-- #include virtual="/includes/header.asp" --> <script type="text/javascript" language="javascript"> function switchImg(imgName) { var ImgX = document.getElementById("mainimg"); ImgX.src="/images/products/" + imgName; } </script> <script type="text/javascript"> $(document).ready(function(){ var options = { zoomWidth: 466, zoomHeight: 260, xOffset: 34, yOffset: 0, title: false, position: "right" //and MORE OPTIONS }; $(".MYCLASS").jqzoom(options); }); </script> <!-- #include virtual="/includes/nav.asp" --> <div id="column-left"> <div id="main-image"> <% if oldie = false then %><a href="/images/products/<%=zoomimg%>" class="MYCLASS" title="MYTITLE"><img src="/images/products/<%=image1%>" title="IMAGE TITLE" name="mainimg" id="mainimg" style="width:425px; height:638px;" ></a><% end if %> </div> </div> <div id="column-right"> <div id="altviews"> <h3 class="altviews">Alternative Views</h3> <ul> <% if oldie = false then writeThumb thumb1,image1,zoomimg,image1desc writeThumb thumb2,image2,zoomimg2,image2desc writeThumb thumb3,image3,zoomimg3,image3desc writeThumb thumb4,image4,zoomimg4,image4desc end if %> </ul> </div> </div> <!-- #include virtual="/includes/footer-test.asp" --> <% sub writeThumb(thumbfile, imgfile, zoomfile, thumbdesc) response.Write "<li>" if thumbfile <> "65/default_preview.jpg" and thumbfile <> "" and not isnull(thumbfile) then if imgFile <> "" and not isnull(imgfile) then rimgfile = replace(imgfile,"/","//") else rimgfile = "" if thumbdesc <> "" and not isnull(thumbdesc) then rDescription = replace(thumbdesc,"""","&quot;") else rDescription = "" response.write "<img src=""/images/products/"& thumbfile &""" style=""cursor: pointer"" border=""0"" style=""width:65px; height:98px;"" title="""& rDescription &""" onclick=""switchImg('" & rimgfile & "')"" />" & vbcrlf else response.write "<img src=""/images/products/65/default_preview.jpg"" alt="""" />" & vbCrLF end if response.write "</li>" & vbCrLF end sub %>

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• what is mistakes/errors in this code c++ tell me the correction ??

  - by jeje

  hello all here in this code the compiler print error : 132 C:.... `createlist' undeclared (first use this function) (Each undeclared identifier is reported only once for each function it appears in.) and repeat it again in all calls in main function :( what's the problem ?? plzzzz help me #include<iostream> #include<string> using namespace std; template <typename T> struct Node { T num; struct Node<T> *next; // to craet list nodes void createlist(Node<T> *p) { T data; for( ; ; ) // its containue until user want to stop { cout<<"enter data number or '#' to stop\n"; cin>>data; if(data == '#') { p->next =NULL; break; } else { p->num= data; p->next = new Node<T>; p=p->next; } } } //count list to use it in sort function int countlist (Node<T> *p) { int count=0; while(p->next != NULL) { count++; p=p->next; } return count; } // sort list void sort( Node<T> *p) { Node<T> *p1, *p2; //element 1 & 2 to compare between them int i, j , n; T temp; n= countlist(p); for( i=1; i<n ; i++) { // here every loop time we put the first element in list in p1 and the second in p2 p1=p; p2=p->next; for(j=1; j<=(n-i) ; j++) { if( p1->num > p2->num) { temp=p2->num; p2->num=p1->num; p1->num=temp; } } p1= p1->next; p2= p2->next; } } //add new number in any location the user choose void insertatloc(Node<T> *p) { T n; //read new num int loc; //read the choosen location Node<T> *locadd, *newnum, *temp; cout <<" enter location you want ..! \n"; cin>>loc; locadd=NULL; //make it null to checked if there is location after read it from user ot not while(p->next !=NULL) { if( p->next==loc) { locadd=p; break; } p=p->next; } if (locadd==NULL) {cout<<" cannot find the location\n";} else //if location is right {cout<<" enter new number\n"; // new number to creat also new location for it cin>>n; newnum= new Node/*<T>*/; newnum->num=n; temp= locadd->next; locadd->next=newnum; newnum->next=temp; } locadd->num=sort(locadd); // call sort function } // display all list nodes void displaylist (Node<T> *p) { while (p->next != NULL) { cout<<" the list contain:\n"; cout<<p->num<<endl; p=p->next; } } };//end streuct int main() { cout<<"*** Welcome in Linked List Sheet 2****\n"; // defined pointer for structer Node // that value is the address of first node struct Node<int>*mynodes= new struct Node<int>; // create nodes in mynodes list cout<<"\nCreate nodes in list"; createlist(mynodes); // insert node in location insertatloc(mynodes); /* count the number of all nodes nodescount = countlist(mynodes); cout<<"\nThe number of nodes in list is: "<<nodescount;*/ // sort nodes in list sort(mynodes); // Display nodes cout<<"\nDisplay all nodes in list:\n"; displaylist(mynodes); system("pause"); return 0; }

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• C programming: hashtable insertion/search

  - by Ricardo Campos

  Hello i have a problem with my hash table its implemented like this: #define HT_SIZE 10 typedef struct _list_t_ { char key[20]; char string[20]; char prevValue[20]; struct _list_t_ *next; } list_t; typedef struct _hash_table_t_ { int size; /* the size of the table */ list_t ***table; /* first */ sem_t lock; } hash_table_t; I have a Linked list with 3 pointers because i want a hash table with several partitions (shards), here is my initialization of my Hash table: hash_table_t *create_hash_table(int NUM_SERVER_THREADS, int num_shards){ hash_table_t *new_table; int j,i; if (HT_SIZE<1) return NULL; /* invalid size for table */ /* Attempt to allocate memory for the hashtable structure */ new_table = (hash_table_t*)malloc(sizeof(hash_table_t)*HT_SIZE); /* Attempt to allocate memory for the table itself */ new_table->table = (list_t ***)calloc(1,sizeof(list_t **)); /* Initialize the elements of the table */ for(j=0; j<num_shards; j++){ new_table->table[j] = (list_t **)calloc(1,sizeof(list_t *)); for(i=0; i<HT_SIZE; i++){ new_table->table[j][i] = (list_t *)calloc(1,sizeof(list_t )); } } /* Set the table's size */ new_table->size = HT_SIZE; sem_init(&new_table->lock, 0, 1); return new_table; } Here is my search function to search in the hash table list_t *lookup_string(hash_table_t *hashtable, char *key, int shardId){ list_t *list ; int hashval = hash(key); /* Go to the correct list based on the hash value and see if key is * in the list. If it is, return return a pointer to the list element. * If it isn't, the item isn't in the table, so return NULL. */ sem_wait(&hashtable->lock); for(list = hashtable->table[shardId][hashval]; list != NULL; list =list->next) { if (strcmp(key, list->key) == 0){ sem_post(&hashtable->lock); return list; } } sem_post(&hashtable->lock); return NULL; } And my insert function: char *add_string(hash_table_t *hashtable, char *str,char *key, int shardId){ list_t *new_list; list_t *current_list; unsigned int hashval = hash(key); /*printf("|%d|%d|%s|\n",hashval,shardId,key);*/ /* Lock for concurrency */ sem_wait(&hashtable->lock); /* Attempt to allocate memory for list */ new_list = (list_t*)malloc(sizeof(list_t)); /* Does item already exist? */ sem_post(&hashtable->lock); current_list = lookup_string(hashtable, key,shardId); sem_wait(&hashtable->lock); /* item already exists, don't insert it again. */ if (current_list != NULL){ strcpy(new_list->prevValue,current_list->string); strcpy(new_list->string,str); strcpy(new_list->key,key); new_list->next = hashtable->table[shardId][hashval]; hashtable->table[shardId][hashval] = new_list; sem_post(&hashtable->lock); return new_list->prevValue; } /* Insert into list */ strcpy(new_list->string,str); strcpy(new_list->key,key); new_list->next = hashtable->table[shardId][hashval]; hashtable->table[shardId][hashval] = new_list; /* Unlock */ sem_post(&hashtable->lock); return new_list->prevValue; } My main class runs some of tests by executing the insertion / reading / delete from the elements of the hash table the problem is when i have more than 4 partitions/shards the tests stop at the first reading element saying it returned the wrong value NULL on the search function, when its less than 4 it runs perfectly well and passes all the tests. You can see my main.c in here if you want to give a look: http://hostcode.sourceforge.net/view/1105 My complete Hash table code: http://hostcode.sourceforge.net/view/1103 And other functions where hash table code is executed: .c file http://hostcode.sourceforge.net/view/1104 .h file http://hostcode.sourceforge.net/view/1106 Thank for you time, i appreciate any help you can give to me this is a college important project that I'm trying to solve and I'm stuck here for 2 days.

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• Trying to draw textured triangles on device fails, but the emulator works. Why?

  - by Dinedal

  I have a series of OpenGL-ES calls that properly render a triangle and texture it with alpha blending on the emulator (2.0.1). When I fire up the same code on an actual device (Droid 2.0.1), all I get are white squares. This suggests to me that the textures aren't loading, but I can't figure out why they aren't loading. All of my textures are 32-bit PNGs with alpha channels, under res/raw so they aren't optimized per the sdk docs. Here's how I am loading my textures: private void loadGLTexture(GL10 gl, Context context, int reasource_id, int texture_id) { //Get the texture from the Android resource directory Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(), reasource_id, sBitmapOptions); //Generate one texture pointer... gl.glGenTextures(1, textures, texture_id); //...and bind it to our array gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[texture_id]); //Create Nearest Filtered Texture gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_NEAREST); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR); //Different possible texture parameters, e.g. GL10.GL_CLAMP_TO_EDGE gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S, GL10.GL_REPEAT); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T, GL10.GL_REPEAT); //Use the Android GLUtils to specify a two-dimensional texture image from our bitmap GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bitmap, 0); //Clean up bitmap.recycle(); } Here's how I am rendering the texture: //Clear gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); //Enable vertex buffer gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer); gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer); //Push transformation matrix gl.glPushMatrix(); //Transformation matrices gl.glTranslatef(x, y, 0.0f); gl.glScalef(scalefactor, scalefactor, 0.0f); gl.glColor4f(1.0f,1.0f,1.0f,1.0f); //Bind the texture gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[textureid]); //Draw the vertices as triangles gl.glDrawElements(GL10.GL_TRIANGLES, indices.length, GL10.GL_UNSIGNED_BYTE, indexBuffer); //Pop the matrix back to where we left it gl.glPopMatrix(); //Disable the client state before leaving gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY); And here are the options I have enabled: gl.glShadeModel(GL10.GL_SMOOTH); //Enable Smooth Shading gl.glEnable(GL10.GL_DEPTH_TEST); //Enables Depth Testing gl.glDepthFunc(GL10.GL_LEQUAL); //The Type Of Depth Testing To Do gl.glEnable(GL10.GL_TEXTURE_2D); gl.glEnable(GL10.GL_BLEND); gl.glBlendFunc(GL10.GL_SRC_ALPHA,GL10.GL_ONE_MINUS_SRC_ALPHA); Edit: I just tried supplying a BitmapOptions to the BitmapFactory.decodeResource() call, but this doesn't seem to fix the issue, despite manually setting the same preferredconfig, density, and targetdensity. Edit2: As requested, here is a screenshot of the emulator working. The underlaying triangles are shown with a circle texture rendered onto it, the transparency is working because you can see the black background. Here is a shot of what the droid does with the exact same code on it: Edit3: Here are my BitmapOptions, updated the call above with how I am now calling the BitmapFactory, still the same results as below: sBitmapOptions.inPreferredConfig = Bitmap.Config.RGB_565; sBitmapOptions.inDensity = 160; sBitmapOptions.inTargetDensity = 160; sBitmapOptions.inScreenDensity = 160; sBitmapOptions.inDither = false; sBitmapOptions.inSampleSize = 1; sBitmapOptions.inScaled = false; Here are my vertices, texture coords, and indices: /** The initial vertex definition */ private static final float vertices[] = { -1.0f, -1.0f, 0.0f, 1.0f, -1.0f, 0.0f, -1.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f }; /** The initial texture coordinates (u, v) */ private static final float texture[] = { //Mapping coordinates for the vertices 0.0f, 1.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f }; /** The initial indices definition */ private static final byte indices[] = { //Faces definition 0,1,3, 0,3,2 }; Is there anyway to dump the contents of the texture once it's been loaded into OpenGL ES? Maybe I can compare the emulator's loaded texture with the actual device's loaded texture? I did try with a different texture (the default android icon) and again, it works fine for the emulator but fails to render on the actual phone. Edit4: Tried switching around when I do texture loading. No luck. Tried using a constant offset of 0 to glGenTextures, no change. Is there something that I'm using that the emulator supports that the actual phone does not? Edit5: Per Ryan below, I resized my texture from 200x200 to 256x256, and the issue was NOT resolved. Edit: As requested, added the calls to glVertexPointer and glTexCoordPointer above. Also, here is the initialization of vertexBuffer, textureBuffer, and indexBuffer: ByteBuffer byteBuf = ByteBuffer.allocateDirect(vertices.length * 4); byteBuf.order(ByteOrder.nativeOrder()); vertexBuffer = byteBuf.asFloatBuffer(); vertexBuffer.put(vertices); vertexBuffer.position(0); byteBuf = ByteBuffer.allocateDirect(texture.length * 4); byteBuf.order(ByteOrder.nativeOrder()); textureBuffer = byteBuf.asFloatBuffer(); textureBuffer.put(texture); textureBuffer.position(0); indexBuffer = ByteBuffer.allocateDirect(indices.length); indexBuffer.put(indices); indexBuffer.position(0); loadGLTextures(gl, this.context);

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