[Boost-users] Help for using interprocess::managed_mapped_file

Subject: [Boost-users] Help for using interprocess::managed_mapped_file
From: Kanthimathi Kalyanamandapam (kkmadrasi_at_[hidden])
Date: 2010-04-01 13:07:58

Hi:
I am experimenting with managed_mapped_file to store a vector of a complex_data encapsulating a string and an array quite like the provided "containers of containers" example.
However, the program behaves in a rather erratic manner , throwing up boost::interprocess_exception::library_error quite randomly after inserting a few elements.

I am including the program below , any help on this will be highly appreciated,

With Regards,
Kanthi K

/////////////////////////


// Compile with: g++ -ansi -Wall -O2  -lrt -o output progname.cc
#include <iostream>
#include <string>
#include <map>
#include <list>
#include <boost/tuple/tuple.hpp>
#include <boost/interprocess/managed_mapped_file.hpp>
#include <boost/interprocess/allocators/allocator.hpp>
#include <boost/interprocess/containers/string.hpp>
#include <boost/interprocess/containers/vector.hpp>
#include <boost/interprocess/exceptions.hpp>
#define MEGABYTE 1048576L

/**
 * Class for storing data in a mmap file
 */
class memmapfile {
private:
	typedef boost::interprocess::managed_mapped_file managed_mapped_file_t;
	typedef managed_mapped_file_t::segment_manager     segment_manager_t;
	typedef boost::interprocess::allocator<void, segment_manager_t> void_alloc;
	typedef boost::interprocess::allocator<int, segment_manager_t>  int_alloc;
	typedef boost::interprocess::allocator<char, segment_manager_t> char_alloc;
	typedef boost::interprocess::vector<int, int_alloc> mm_int_vector;
	typedef boost::interprocess::basic_string<char, std::char_traits<char>, char_alloc> mm_string;
	typedef std::list<int> std_int_list;
	/* holder */
	struct holder {
		holder(mm_string mstr, mm_int_vector mintvec) :
				mstr_(boost::interprocess::move(mstr)),
				mintvec_(boost::interprocess::move(mintvec)) {
		}
		~holder() {}
private:
		mm_string  mstr_;
		mm_int_vector mintvec_;
	};
	typedef boost::interprocess::allocator<holder, segment_manager_t> holder_alloc;
	typedef boost::interprocess::vector<holder, holder_alloc> mm_holder_vector;
	/** functions */
	/** segment functions */
	void open_file() {
		segment = managed_mapped_file_t(boost::interprocess::open_or_create, file_location_.c_str(), file_size_);
		void_alloc alloc_inst(segment.get_segment_manager());
		mm_holder_vector *usevec;
		usevec = segment.find_or_construct<mm_holder_vector> (boost::interprocess::unique_instance) (alloc_inst);
		std::cerr << "Vec Size at open : " << usevec->size() << std::endl;
	}
	void grow_file(std::size_t ExtraBytes) {
		if (ExtraBytes <= 0) ExtraBytes=file_incr_unit;
		std::cerr << "Growing file : " << file_size_ << " + " << ExtraBytes << " = ";
		segment.grow(file_location_.c_str(),ExtraBytes);
		segment = managed_mapped_file_t(boost::interprocess::open_only, file_location_.c_str());
		file_size_ = segment.get_size();
		std::cerr << file_size_ << std::endl;
	}
	void init_usevec(bool clear) {
		void_alloc alloc_inst(segment.get_segment_manager());
		mm_holder_vector *usevec;
		std::size_t count=0;
		boost::tie(usevec,count) = segment.find<mm_holder_vector> (boost::interprocess::unique_instance);
		if (count==0) {
			std::cerr << "Cannot find vector" << std::endl;
			exit(1);
		}
		if (clear) {
			std::cerr << "Clearing vector" << std::endl;
			segment.destroy<mm_holder_vector>(boost::interprocess::unique_instance);
			usevec = segment.construct<mm_holder_vector> (boost::interprocess::unique_instance) (alloc_inst);
		}
	}
	/* variables */
	std::string file_location_;
	std::size_t file_size_;
	const std::size_t file_incr_unit;
	managed_mapped_file_t segment;
public:
	memmapfile(const std::string file_location, const std::size_t file_size, bool clear) :
			file_location_(file_location), file_size_(file_size), file_incr_unit(file_size) {
		try {
			open_file();
			if (file_size_ > segment.get_size()) grow_file(file_size_ - segment.get_size());
			init_usevec(clear);
		} catch (...) {
			std::cerr << " Cannot init mmapfile " << std::endl;
			exit(1);
		}
	}
	virtual ~memmapfile() {}
	/**
	 * add: add an entry
	 */
	template<class T>
	std::size_t add(const std::string& in_str, const T& in_list) {
		std::size_t ret=0;
		try {
			std::size_t min_space_need = (in_str.length() * sizeof(char)) + (in_list.size() * sizeof(typename T::value_type));
			while ( min_space_need*4  > segment.get_free_memory() ) {
				grow_file(file_incr_unit);
			}
			void_alloc alloc_inst(segment.get_segment_manager());
			mm_holder_vector *usevec;
			std::size_t count=0;
			boost::tie(usevec,count) = segment.find<mm_holder_vector> (boost::interprocess::unique_instance);
			if (count==0) {
				std::cerr << "Cannot find vector" << std::endl;
				exit(1);
			}
			mm_string move_mstr(alloc_inst);
			mm_int_vector move_mintvec(alloc_inst);
			move_mstr = in_str.c_str();
			for (typename T::const_iterator it = in_list.begin() ; it!= in_list.end() ; ++it) {
				move_mintvec.push_back(*it);
			}
			usevec->push_back(holder(move_mstr,move_mintvec));
			ret = usevec->size();
			std::cerr << "Added, Vec size: "  << usevec->size() << "/"  << usevec->max_size() << ", ";
			std::cerr << "Memory free: "  << segment.get_free_memory() << "/" << segment.get_size() << ", ";
			double f = ((double)segment.get_free_memory()/(double)segment.get_size()) * 100;
			std::cerr << "% : "  << f << std::endl;
		} catch (boost::interprocess::interprocess_exception e) {
			std::cerr << "Cannot add: " << e.what() << std::endl;
			exit(1);
		}
		return ret;
	}
};

int main()
{
	typedef std::list<int> std_int_list;
	std::string in_str = "abcdefghijklmnopqrstuvwxyz";
	std_int_list in_list;
	for (int i=0; i<1024*8; ++i) {
		in_list.push_back(i) ;
	}
	std::size_t min_space_need = (in_str.length() * sizeof(char)) + (in_list.size() * sizeof(std_int_list::value_type));
	std::cerr << "#### min space needed: " << min_space_need << std::endl;
	memmapfile* m = new memmapfile("test.bin",MEGABYTE,false);
	int i=0;
	while (++i<100) {
		std::size_t sz = m->add<std_int_list>(in_str,in_list);
		std::cerr << "Added in main loop: " << sz << std::endl;
	}
}







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