我想在共享內存中保留大量的(經常重複的)字符串,所以我使用了Boost的輕量級和進程間basic_string功能。爲了確保字符串實際存儲在共享內存中,我需要在flyweight使用的hashed_factory中提供一個自定義分配器。使用Boost輕量級共享內存
但是,當我將自定義分配器指定爲hashed_factory時,無法編譯(g ++ 4.2.1)...可能是因爲它需要額外的參數來指定段管理器。什麼是語法來得到這個工作,或者有更好的方法來做到這一點?
#include <boost/interprocess/managed_mapped_file.hpp>
#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/allocators/allocator.hpp>
#include <boost/interprocess/containers/string.hpp>
#include <boost/flyweight.hpp>
#include <boost/flyweight/no_tracking.hpp>
#include <boost/flyweight/hashed_factory.hpp>
using namespace boost::flyweights;
using namespace boost::container;
using namespace boost::interprocess;
typedef boost::interprocess::allocator<boost::mpl::_1, boost::interprocess::managed_mapped_file::segment_manager> ShmFactoryEntryAllocator;
typedef boost::interprocess::allocator<char, boost::interprocess::managed_mapped_file::segment_manager> ShmAllocatorChar;
typedef boost::interprocess::basic_string<char, std::char_traits<char>, ShmAllocatorChar> ShmString;
// TODO: using ShmFactoryEntryAllocator does not work
typedef boost::flyweights::hashed_factory<boost::hash<ShmString>, std::equal_to<ShmString>, ShmFactoryEntryAllocator> ShmStringHashedFactory;
//typedef boost::flyweights::hashed_factory<boost::hash<ShmString>, std::equal_to<ShmString>, std::allocator<boost::mpl::_1> > ShmStringHashedFactory;
// TODO: need to be able to use a hashed_factory with our custom allocator.
typedef boost::flyweights::flyweight<ShmString, ShmStringHashedFactory> ShmFlyweightString;
//typedef boost::flyweights::flyweight<ShmString> ShmFlyweightString;
int main(int argc, char** argv)
{
managed_mapped_file *segment = new managed_mapped_file(create_only, "memory.dat", 409600);
ShmFactoryEntryAllocator factoryEntryAllocator(segment->get_segment_manager());
// create a normal string in shared-memory.
ShmString *ps1 = segment->construct<ShmString>("s1")("some shm normal string", factoryEntryAllocator);
// create a flyweight string in shared memory.
ShmFlyweightString *ps2 = segment->construct<ShmFlyweightString>(anonymous_instance)("some shm flyweight string", factoryEntryAllocator);
return 0;
}
的TODO註釋後的線是有問題的線路,加上註釋的版本是說工作,但沒有使用正確的分配器的人。
我認爲這樣越來越接近了,但我仍然無法完成編譯。事實證明,MyShmAllocator構造函數實際上不應該取消引用指針。但是,在將ShmStringHashedFactory切換爲使用MyShmAllocator後,它仍然不太高興...... https://gist.github.com/bovine/5863647 – bovine
事實證明,您的答案是正確的,但還有更多需要一個完整的解決方案,例如擁有知道如何存儲共享內存和鎖定策略的持有者類。我的同事在Boost郵件列表中提出了同樣的問題,並從JoaquínMLópezMuñoz那裏得到了非常全面的答案:http://permalink.gmane.org/gmane.comp.lib.boost.devel/242512 – bovine