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Re: [Boost-users] [serialization, 1_33_0] Correct usage and implementation for serializable objects without default constructors
by Martin Proulx 16 Sep '05

16 Sep '05

> In this example, we have a class A that doesn't have a default > constructor. > An int is needed by the constructor, which is stored in the i member > variable. load/save_construct_data are used to un/serialize the i member, > while the serialize member is used for all other members. > > Looking at this test, I see a couple of behaviors that puzzle me. > > -) Saving the 'a' instance in the save() function doesn't end up calling > save_construct_data. This leaves a serialized version of A which lacks > the > 'i' member. This makes it impossible to fully restore the 'a' > instance. It > seems problematic to me that save_construct_data isn't called in this > case. > >> I just re-ran test_non_default_ctor. I ran under the VC 7.1 debugger and >> inserted traps inside both save_construct_data and >> load_construct_data. II >> verified that save_construct_data and load_construct_data are being >> invoked >> exactly as they are intended. I see no problem here. > > > In my planned usage, I'd like to fully serialize all members, > regardless if > the objects are serialized directly or through pointers. I cannot see how > to do this without serializing the members needed to reconstruct the > object > in both serialize and save_construct_data, even if some members will > end up > serialized twice when an object is stored through a pointer. > >> If the members are not pointers, the constructor is never called. so the >> parameters set by the constructor are not needed. >> save_load_contruct_data >> is only called when its necessary to create a new object. > > > What's the proper way to serialize all members of a class without a > default > constructor so that it gets fully serialized regardless how the > objects are > managed? > >> Exactly as described in the manual and illustrated by the example >> test_non_default_ctor. > > > -) When restoring the 'a' instance within load(), in order to restore > it, we > first create another 'a' instance (with a different constructor > argument), > then restore the other members within, leaving untouched the 'i' member. > Assuming I'd like to be able to serialize and unserialize completely > objects > that do not have a default constructor, I'm wondering how I can fully > restore an object that doesn't have a default constructor. > >> All you have to do is define save_construct_data and >> load_construct_data for >> all types which don't have a default constructor. The library takes >> care of >> everything else. > > > I've looked for some other mechanism relying on a copy constructor and > something along the lines of load_construct_data, but I haven't found > any. > >> Somehow I'm thinking you're looking for the wrong thing. I wonder if >> you're >> not underestimating what the library does for you. As I said, you, only >> need to define save/load_construct_data for those types which don't >> have a >> default constructor - there is nothing else required to do. >> >> Robert Ramey > > Hello, As this discussion is going, it seems clear that either I'm missing something somewhere or that I'm not being clear enough in exposing my problems... I'll directly include a sample of something similar to what I'd like to achieve that doesn't work. Please take a look at the example, and let me know how you would modify this to make both assert succeed. If you notice that I've missed some concept in the way the library should be used, please enlighten me! Thanks, Martin ------------------------------------------------------------------------ #include <cstdlib> #include <cassert> #include <sstream> #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> #include <boost/serialization/string.hpp> using namespace std; class Person { public: Person(const string& name) : _name(name), _favoriteFood("none") {} const string& getName() const {return _name;} const string& getFavoriteFood() const {return _favoriteFood;} void setFavoriteFood(const string& favoriteFood) {_favoriteFood = favoriteFood;} private: const string _name; string _favoriteFood; friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int /* file_version */){ ar & _favoriteFood; } }; namespace boost { namespace serialization { template<class Archive> inline void save_construct_data(Archive & ar, const Person * person, const unsigned int /* file_version */) { ar << person->getName(); } template<class Archive> inline void load_construct_data(Archive & ar, Person * person, const unsigned int /* file_version */) { string name; ar >> name; ::new(person)Person(name); } } // serialization } // namespace boost template<class Archive> void serializePerson(Archive& oa, const Person& someone) { // save_construct_data isn't called when serializing a Person in this fashion. // The person's name will not appear in the archive. oa << someone; } template<class Archive> Person UnserializePerson(Archive& ia) { // I'm constructing a temporary person, with a bogus name, as it's the only workaround I've come up with. // There is no way that unserializing returns an actual object, like I'm needing here. Person someone("bogus name"); // When unserializing in this fashion, load_construct_data isn't called either. ia >> someone; // The initial person's name is then lost. return someone; } void main(void) { Person *const Joe = new Person("Joe"); Person John("John"); stringstream stringStream; boost::archive::text_oarchive oa(stringStream); oa << Joe; serializePerson(oa, John); boost::archive::text_iarchive ia(stringStream); Person* restoredPersonPointer; ia >> restoredPersonPointer; Person restoredPerson(UnserializePerson(ia)); assert(restoredPersonPointer->getName() == Joe->getName()); // works fine. assert(restoredPerson.getName() == John.getName()); // fails. } -- Tel: (450) 681-1681, #271 ------------------------------------------------------------------------ OKIOK Enterprise and e-business security solutions Solutions de sécurité d'entreprise et d'affaires électronique Tel. : (450) 681.1681 http://www.okiok.com This e-mail message (including attachments, if any) is intended for the use of the individual or entity to which it is addressed and may contain information that is privileged, proprietary, confidential and exempt from disclosure. If you are not the intended recipient, you are notified that any dissemination, distribution or copying of this communication is strictly prohibited. If you have received this communication in error, please notify the sender and erase this e-mail message immediately. Le présent message électronique (y compris les pièces qui y sont annexées, le cas échéant) s'adresse au destinataire indiqué et peut contenir des renseignements de caractère privé ou confidentiel. Si vous n'êtes pas le destinataire de ce document, nous vous signalons qu'il est strictement interdit de le diffuser, de le distribuer ou de le reproduire. Si ce message vous a été transmis par erreur, veuillez en informer l'expéditeur et le supprimer immédiatement.

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Re: [Boost-users] Could the BGL graph algorithms be improvedto automatically work with VertexList = listS graphs?
by Tony Cook 16 Sep '05

16 Sep '05

I retracted this in a subsequent post - it was my problem with a custom vertex property (blush) >From: Daryle Walker <darylew(a)hotmail.com> >Reply-To: boost-users(a)lists.boost.org >To: Boost Users mailing list <boost-users(a)lists.boost.org> >Subject: Re: [Boost-users] Could the BGL graph algorithms be >improvedto automatically work with VertexList = listS graphs? >Date: Thu, 15 Sep 2005 18:05:46 -0400 > >On 9/15/05 7:05 AM, "Tony Cook" <tony__cook(a)hotmail.com> wrote: > > > Can I add that misuse of graph assignment and a graph copy constructor >is > > possible - corruptible shallow copies are the result. These methods >should > > be given private scope to prevent (mis)use or be correctly implemented > > > > G2 = G1 ; // Compiles but NO you must use boost::graph_copy (G1, G2) >instead > >If this is accurate, then it should be fixed. Types with abnormal copying >semantics can't be used in STL containers or similar contexts. > >-- >Daryle Walker >Mac, Internet, and Video Game Junkie >darylew AT hotmail DOT com > >_______________________________________________ >Boost-users mailing list >Boost-users(a)lists.boost.org >http://lists.boost.org/mailman/listinfo.cgi/boost-users

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How can I find all the shortest path in a graph?
by Giulio Veronesi 16 Sep '05

16 Sep '05

Hi all, Please excuse me if I post my question again, but I've spent all the night and the day before looking for a solution of the following problem: How to find *all* the possible shortest paths from a source vertex to a target vertex in a directed graph? I tried using depth_first_search and acting on visitors without any success. Please, could you help me? Thanks a lot in advance, Giulio

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How to extending algorithms with visitors
by Giulio Veronesi 15 Sep '05

15 Sep '05

Hi all, I'm enjoying learning the boost graph library. I'm trying to use the Dijkstra algorithm and try to store the shortest path as explained in the subsection "Extending Algorithms with Visitors" of the section "Quick Tour" of the BGL user guide. When I try to compile my code, I get the following error message: mesh.cpp:38: error: expected constructor, destructor, or type conversion before '<' token mesh.cpp:38: error: expected `;' before '<' token where line 38 is highlighted in the following portion of code. Could you help me to resolve this problem? Thanks in advance, Giulio template <class PredecessorMap> class record_predecessors : public dijkstra_visitor<> { public: record_predecessors(PredecessorMap p) : m_predecessor(p) { } template <class Edge, class Graph> void edge_relaxed(Edge e, Graph& g) { // set the parent of the target(e) to source(e) put(m_predecessor, target(e, g), source(e, g)); } protected: PredecessorMap m_predecessor; }; template <class PredecessorMap> line 38: record_predecessors<PredecessorMap> make_predecessor_recorder(PredecessorMap p) { return record_predecessors<PredecessorMap>(p); } ___________________________________ Yahoo! Mail: gratis 1GB per i messaggi e allegati da 10MB http://mail.yahoo.it

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Matrix of submatricies...
by Edward Grace 15 Sep '05

15 Sep '05

Dear all, [you may need a fixed with font] Consider the following 4x4 matrix which is a 2x2 matrix of submatricies. A B | 0 0 C D | 0 0 ----+---- 0 0 | a b 0 0 | c d Clearly matrix operations such as products do not need to involve the off diagonal (zero) sub matricies. Is there a matrix type that "knows" about this type of matrix so that when prod() is carried out it does not do unnecessary operations with the zero elements? -ed

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[Regex] Empty regular expression
by Marco Craveiro 15 Sep '05

15 Sep '05

Hello boosters, First, apologies if this has been discussed before - I did some googling and could not find it. I've bumped into an interesting issue while using Boost.Regex. The documentation states: http://www.boost.org/libs/regex/doc/basic_regex.html Effects: Constructs an object of class basic_regex. The postconditions of this function are indicated in the table: Element Value empty() true size() 0 str() basic_string<charT>() Using 1.33, I get empty() set to false with the default constructor. In addition, if you attempt to search using an empty regex, the program segfaults. The following example demonstrates the problem: code: ------ #include <iostream> #include <string> #include <boost/regex.hpp> int main() { std::string line("this is an example line"); boost::smatch what; boost::regex re; std::cout << "re.empty(): " << re.empty() << std::endl; bool result = boost::regex_search(line, what, re); } output: ------ re.empty(): 0 Segmentation fault This does not happen if I initialize the regex using an empty string (it throws empty expression). Which leads to the main question (and the reason why I discovered all of this): is it possible to make a regular expression that matches anything? For instance, when using AWK, if you define a rule without a pattern, i.e.: { print $0; } I thought an empty regex would do the trick. Regards, Marco -- in software development, the design document is a source code listing. -- jack reeves

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Error compiling boost/tuple/tuple.hpp with boost 1.33 on VC 7.1
by Rob Caldecott 15 Sep '05

15 Sep '05

I have just upgraded to boost 1.33 from 1.32 and boost/tuple/tuple.hpp no longer compiles. I am using MS Visual Studio 2003 (7.1). Errors include: "boost-1_33\boost\tuple\detail\tuple_basic.hpp(66) : error C2332: 'class' : missing tag name" when compiling: template <class HT, class TT> struct cons; As I am new to boost, I have no idea how to continue. I am not even using tuple directly - it is included by iterator/indirect_iterator.hpp. Anyone else come across this? Looks like I'll have to switch back to 1.32. Thanks in advance.

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boost libraries under VxWorks
by swoh 15 Sep '05

15 Sep '05

Hello all. I am failing to compile the serialization library (from version 1.0.32) for use with VxWorks 5.4.2 (Tornado 2.2.1). I am restricted to their version of the g++2.96 compiler and matching libraries. I will probably be interested in using other boost libraries in the future (shared pointer at the least). The errors I am getting all have to do with default template parameters, although there may be other problems lurking ahead. Has anyone succeeded in using boost with this combination? Any tips? Thank you ori

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Boost.Iostreams + error handling
by Martin Slater 14 Sep '05

14 Sep '05

Hi there, Are exceptions the only way to propogate an error out of and IOStreams.Device policy? We have a lot of code using this style std::istream is(file); if(is) { .... } and would like not to have to change it all over to use ios exceptions but I can't see a way to avoid it. Is it possible? thanks Martin

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Re: [Boost-users] [filesystem] function to determine available space
by Sohail Somani 14 Sep '05

14 Sep '05

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Delfin Rojas > Sent: Wednesday, September 14, 2005 11:55 AM > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] [filesystem] function to determine > available space > > > > > I think the word "status" in space_status is misleading since > > > available/total space is not really a status. > > > > What makes you say that? > > > > Ben. > > > > It is just my interpretation of the word "status": the status > of a patient (stable, critical, etc.), the status of an > electronic device (powered, running, connected, disconnected, etc.). > > If I see a function or structure that is called > filesystem_status I would think it represents one or more > states in which the files system can be, like empty/full or > online/offline. I guess each possible total_size / used_size > combination is a possible filesystem status but still it > doesn't sound good to me. > > At the end of the day it is up to whoever implements the > function to decide, I was just giving my suggestion because I > think it is important programming constructs have a name from > which their usage/meaning can be easily guessed or deduced. Design by committee rocks.

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