[Serialization] Can I load two object from one input file?
Hi all, Code like this: // Save std::ofstream ofs( "c.out" ); A testA1; B testB1; testA1.Save( ofs ); testB1.Save( ofs ); ofs.close(); // Load std::ifstream ifs( "c.out" ); A testA11; B testB11; testA11.Load( ifs ); testB11.Load( ifs ); The testA1 and testB1 can save successful, and the testA11 can load successful, but when loading testB11, it throw a exception "invalid_signature". I have trace into the code, I found when the testA11 loading, the "file_signature" is "serialization::archive", but when testB11 loading, the "file_signature" is empty. Why it like this? What should I do? May be there is the same question before I ask, but I don't know what keyword could be search, sorry. Thanks!
On Thursday 27 December 2007 00:20:24 sjdf wrote:
// Save std::ofstream ofs( "c.out" );
A testA1; B testB1;
testA1.Save( ofs ); testB1.Save( ofs );
ofs.close();
// Load std::ifstream ifs( "c.out" );
A testA11; B testB11;
testA11.Load( ifs ); testB11.Load( ifs );
The simple solution would be to create a "C" type that contains an "A" and a "B". Then you could just save and load the C object. Hope This Helps, Justin
In my application, I am am saving 2 objects into the same archive and then reading them back correctly in the same order - so it is possible. Maybe you could post how you implemented "Load" and "Save" and I can try to help you. Mahesh
The program run ok when I compile it with mingw, but if I compile it use vc71, the program will crash when excute "pbb->Load( ifs );". Thinks! code: //---------------------------------------------------------------------------- #include <string> #include <iostream> #include <fstream> #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> //---------------------------------------------------------------------------- using namespace std; //---------------------------------------------------------------------------- class A { private: friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & a; ar & b; } public: int a; int b; void Load( std::ifstream& ifs ) { boost::archive::text_iarchive ia(ifs); ia >> *this; } void Save( std::ofstream& ofs ) { boost::archive::text_oarchive oa(ofs); const A& refa = *this; oa << refa; } }; //---------------------------------------------------------------------------- class B { private: friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & ms; ar & a; } public: void Load( std::ifstream& ifs ) { boost::archive::text_iarchive ia(ifs); ia >> *this; } void Save( std::ofstream& ofs ) { boost::archive::text_oarchive oa(ofs); const B& refb = *this; oa << refb; } public: B( const string& s ) : ms( s ){} void print(){ cout << ms << endl; } private: string ms; A a; }; //---------------------------------------------------------------------------- int test_TestStorage() { // Save A* pa = new A; pa->a = 3; pa->b = 5; B* pb = new B( "this is test B" ); std::ofstream ofs( "all.out" ); pa->Save( ofs ); pb->Save( ofs ); delete pa; delete pb; ofs.close(); // Load A* paa = new A; B* pbb = new B( "" ); std::ifstream ifs( "all.out", std::ios::binary ); paa->Load( ifs ); pbb->Load( ifs ); cout << "A: " << paa->a << " " << paa->b << endl; pbb->print(); delete paa; delete pbb; return 0; } //---------------------------------------------------------------------------- int main( void ) { test_TestStorage(); return 0; } 2007/12/31, Mahesh Venkitachalam <mkvenkit.vc@gmail.com>:
In my application, I am am saving 2 objects into the same archive and then reading them back correctly in the same order - so it is possible. Maybe you could post how you implemented "Load" and "Save" and I can try to help you.
Mahesh
_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
#include <iostream>
#include <fstream>
#include <boost/serialization/string.hpp> #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp>
//---------------------------------------------------------------------------- using namespace std;
//---------------------------------------------------------------------------- class A { private: friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & a; ar & b; }
public: int a; int b;
};
//---------------------------------------------------------------------------- class B { private: friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & ms; ar & a; } public:
public: B( const string& s ) : ms( s ){} void print(){ cout << ms << endl; } private: B(){} // use by serialization only string ms; A a; };
//---------------------------------------------------------------------------- int main() { // Save A* pa = new A;
Rather than put your program on my debugger, here is the way I anticipated that the library would be used: pa->a = 3; pa->b = 5; B* pb = new B( "this is test B" ); { std::ofstream ofs( "all.out" ); boost::archive::text_oarchive oa(ofs); oa << pa; ob << pb; delete pa; delete pb; } A* paa; B* pbb { std::ifstream ifs( "all.out", std::ios::binary ); boost::archive::text_oarchive ia(ifs); ia >> paa; ia >> pbb; } cout << "A: " << paa->a << " " << paa->b << endl; pbb->print(); delete paa; delete pbb; return 0; } Robert Ramey
Thank you, Robert. I really want to konw why the program can run successful when using mingw to compile, and will crash when using vc71 to compile. I have debug and trace into the code, I found when I execute pbb->Load( ifs );, it will call this function: basic_text_iarchive<Archive>::init(void){ // read signature in an archive version independent manner std::string file_signature; * this->This() >> file_signature; if(file_signature != ARCHIVE_SIGNATURE()) boost::throw_exception( archive_exception(archive_exception::invalid_signature) ); the file_signature is empty, so throw the exception invalid_signature. Can you tell me, why it like this? 2008/1/2, Robert Ramey <ramey@rrsd.com>:
Rather than put your program on my debugger, here is the way I anticipated that the library would be used:
#include <iostream>
#include <fstream>
#include <boost/serialization/string.hpp> #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp>
//---------------------------------------------------------------------------- using namespace std;
//---------------------------------------------------------------------------- class A { private: friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & a; ar & b; }
public: int a; int b;
};
//---------------------------------------------------------------------------- class B { private: friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & ms; ar & a; } public:
public: B( const string& s ) : ms( s ){} void print(){ cout << ms << endl; } private: B(){} // use by serialization only string ms; A a; };
//---------------------------------------------------------------------------- int main() { // Save A* pa = new A; pa->a = 3; pa->b = 5;
B* pb = new B( "this is test B" );
{ std::ofstream ofs( "all.out" ); boost::archive::text_oarchive oa(ofs);
oa << pa; ob << pb;
delete pa; delete pb; } A* paa; B* pbb { std::ifstream ifs( "all.out", std::ios::binary );
boost::archive::text_oarchive ia(ifs); ia >> paa; ia >> pbb; }
cout << "A: " << paa->a << " " << paa->b << endl; pbb->print();
delete paa; delete pbb; return 0; }
Robert Ramey
_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
In your original example a) you' re reconstruction the archive for each object. I can't imagine what the purpose of this is. Certainly one would not expect to be able to serialize multiple objects to an archive if the archive is being re-constructed with every object. b) you're code contains things like ar << *this; This suggests to me that there is some confusion as to how the library is intended to be used. I would recommend a more careful revue of the demos and perhaps some of the tests which might be similar to your example. Robert Ramey
participants (2)
-
KSpam -
Mahesh Venkitachalam -
Robert Ramey -
sjdf