c++ boost进程间交换(复制)非共享和共享字符串 vector

Question

我想实现在 this 的答案中实现的目标问题，但对于字符串 vector ，即字符串对象。我希望能够编写可用于堆内存或共享内存的通用代码。我已经模拟了代码并编写了一个类来实现适用于堆内存或共享内存的字符串 vector 。我大部分时间都在使用它。但是，当我尝试从堆分配的字符串 vector 中初始化/创建字符串的共享内存 vector 时，我遇到了编译错误。在上面提到的问题中，共享内存 vector 是从非共享内存 vector 初始化的(引用“这是因为......神奇!”)。不确定是不是因为这个问题是在处理一个易于复制和移动的整数 vector 。我已经为共享内存字符串类提供了复制构造函数，但它仍然不起作用。我在下面提供了我的代码(注释掉了给我编译错误的代码)。任何帮助表示赞赏。谢谢。

#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/allocators/allocator.hpp>
#include <boost/interprocess/containers/vector.hpp>
#include <boost/interprocess/containers/string.hpp>
#include <boost/container/scoped_allocator.hpp>
#include <iostream>
#include <string>
#include <sstream>

namespace bip = boost::interprocess;

namespace generic
{

template <typename T, typename Alloc/* = std::allocator<T>*/ >
using vector = bip::vector<T, typename Alloc::template rebind<T>::other >;

template <typename Alloc/* = std::allocator<T>*/ >
using GenericString = bip::basic_string<char, std::char_traits<char>
                           , typename Alloc::template rebind<char>::other>;

template <typename Alloc>
class String
{
public:
  typedef Alloc allocator_type; // ties in with uses_allocator/scoped_allocator

  String(Alloc alloc = Alloc())
  : mString(alloc)
  {
  }

  String(const std::string str, Alloc alloc = Alloc())
  : mString(str.c_str(), alloc)
  {
  }

  String(const char* str, Alloc alloc = Alloc())
  : mString(str, alloc)
  {
  }

  template <typename OtherAlloc>
  String(String<OtherAlloc> const& other, Alloc alloc = Alloc())
  : mString(other.mString.begin(), other.mString.end(), alloc)
  {
  }

  std::string ToString() { return std::string(mString.begin(), mString.end()); }

  friend std::ostream& operator<<(std::ostream& os, const String& str)
  {
    os << str.mString;
    return os;
  }

private:
  template<typename OtherAlloc> friend struct String;
  GenericString<Alloc> mString;
};

template <typename Alloc>
class StringVector
{
public:
  typedef Alloc allocator_type; // ties in with uses_allocator/scoped_allocator
  typedef vector<String<Alloc>, Alloc> GenericStringVector;
  using Iterator = typename GenericStringVector::iterator;
  using ConstIterator = typename GenericStringVector::const_iterator;

  StringVector(Alloc alloc = Alloc())
  : mStrings(alloc)
  {
  }

  template <typename OtherAlloc>
  StringVector(StringVector<OtherAlloc> const& other, Alloc alloc = Alloc())
  : mStrings(other.mStrings.begin(), other.mStrings.end(), alloc)
  {
  }

  void Add(const String<Alloc> str) { mStrings.emplace_back(str); }

  void Remove(Iterator iter) { mStrings.erase(iter); }

  void Clear() { mStrings.clear(); }

  void Print() const
  {
    std::cout << "[";
    for (ConstIterator it = mStrings.begin(); it != mStrings.end(); it++)
      std::cout << (it == mStrings.begin() ? "" : ", ") << *it;
    std::cout << "]\n";
  }

private:
  template<typename OtherAlloc> friend struct StringVector;
  GenericStringVector mStrings;
};

}

namespace heap
{
  using VAlloc = std::allocator<void>;
  using String = generic::String<VAlloc>;
  using StringVector = generic::StringVector<VAlloc>;
}

namespace shared
{
  using VAlloc =boost::container::scoped_allocator_adaptor<
          bip::allocator<void, bip::managed_shared_memory::segment_manager> >;

  using String = generic::String<VAlloc>;
  using StringVector = generic::StringVector<VAlloc>;
}

int main(void)
{
  struct shm_remove {
      shm_remove()  { bip::shared_memory_object::remove("MySharedMemory"); }
      ~shm_remove() { bip::shared_memory_object::remove("MySharedMemory"); }
  } remover;

  std::cout << "Heap based storage: \n";
  heap::StringVector svec;

  svec.Add(heap::String("test1"));
  svec.Add(heap::String("test2"));
  svec.Add(heap::String("test3"));
  svec.Add(heap::String("test4"));
  svec.Print();

  std::cout << "Shared memory storage: \n";
  bip::managed_shared_memory seg(bip::create_only, "MySharedMemory", 65536);
  shared::VAlloc shalloc(seg.get_segment_manager());

  shared::StringVector sh_svec(shalloc);
  sh_svec.Add(shared::String("test1", shalloc));
  sh_svec.Add(shared::String("test2", shalloc));
  sh_svec.Add(shared::String("test3", shalloc));
  sh_svec.Add(shared::String("test4", shalloc));
  sh_svec.Print();


  shared::StringVector sh_svec2(sh_svec, shalloc);
  sh_svec2.Print();

  //shared::StringVector sh_svec3(svec, shalloc);   // gives compile error :(
  //sh_svec3.Print();
}

包括编译错误:

In file included from src/test_string_vector.cc:5:0:
/usr/include/boost/container/scoped_allocator.hpp: In instantiation of ‘boost::container::container_detail::scoped_allocator_adaptor_base<OuterAlloc>::scoped_allocator_adaptor_base() [with OuterAlloc = boost::interprocess::allocator<void, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> >]’:
/usr/include/boost/container/scoped_allocator.hpp:963:7:   required from ‘boost::container::scoped_allocator_adaptor<OuterAlloc, InnerAllocs>::scoped_allocator_adaptor() [with OuterAlloc = boost::interprocess::allocator<void, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> >; InnerAllocs = {}]’
/usr/include/boost/container/vector.hpp:1174:15:   required from ‘void boost::container::vector<T, Allocator>::assign(FwdIt, FwdIt, typename boost::container::container_detail::enable_if_c<((! boost::container::container_detail::is_convertible<InIt, typename boost::container::allocator_traits<Allocator>::size_type>::value) && ((! boost::container::container_detail::is_input_iterator<InIt>::value) && (! boost::move_detail::is_same<typename boost::container::container_detail::version<Allocator>::type, boost::container::container_detail::integral_constant<unsigned int, 0u> >::value)))>::type*) [with FwdIt = boost::container::container_detail::vec_iterator<generic::String<std::allocator<void> >*, true>; T = generic::String<boost::container::scoped_allocator_adaptor<boost::interprocess::allocator<void, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> > > >; Allocator = boost::container::scoped_allocator_adaptor<boost::interprocess::allocator<generic::String<boost::container::scoped_allocator_adaptor<boost::interprocess::allocator<void, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> > > >, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> > >; typename boost::container::container_detail::enable_if_c<((! boost::container::container_detail::is_convertible<InIt, typename boost::container::allocator_traits<Allocator>::size_type>::value) && ((! boost::container::container_detail::is_input_iterator<InIt>::value) && (! boost::move_detail::is_same<typename boost::container::container_detail::version<Allocator>::type, boost::container::container_detail::integral_constant<unsigned int, 0u> >::value)))>::type = void]’
/usr/include/boost/container/vector.hpp:864:7:   required from ‘boost::container::vector<T, Allocator>::vector(InIt, InIt, const allocator_type&) [with InIt = boost::container::container_detail::vec_iterator<generic::String<std::allocator<void> >*, true>; T = generic::String<boost::container::scoped_allocator_adaptor<boost::interprocess::allocator<void, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> > > >; Allocator = boost::container::scoped_allocator_adaptor<boost::interprocess::allocator<generic::String<boost::container::scoped_allocator_adaptor<boost::interprocess::allocator<void, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> > > >, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> > >; boost::container::vector<T, Allocator>::allocator_type = boost::container::scoped_allocator_adaptor<boost::interprocess::allocator<generic::String<boost::container::scoped_allocator_adaptor<boost::interprocess::allocator<void, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> > > >, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> > >]’
src/test_string_vector.cc:78:65:   required from ‘generic::StringVector<Alloc>::StringVector(const generic::StringVector<OtherAlloc>&, Alloc) [with OtherAlloc = std::allocator<void>; Alloc = boost::container::scoped_allocator_adaptor<boost::interprocess::allocator<void, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> > >]’
src/test_string_vector.cc:151:46:   required from here
/usr/include/boost/container/scoped_allocator.hpp:762:7: error: no matching function for call to ‘boost::interprocess::allocator<void, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> >::allocator()’
       {}
       ^
In file included from /usr/include/boost/interprocess/segment_manager.hpp:38:0,
                 from /usr/include/boost/interprocess/detail/managed_memory_impl.hpp:30,
                 from /usr/include/boost/interprocess/managed_shared_memory.hpp:25,
                 from src/test_string_vector.cc:1:
/usr/include/boost/interprocess/allocators/allocator.hpp:142:4: note: candidate: template<class T2> boost::interprocess::allocator<T, SegmentManager>::allocator(const boost::interprocess::allocator<T2, SegmentManager>&)
    allocator(const allocator<T2, SegmentManager> &other)
    ^
/usr/include/boost/interprocess/allocators/allocator.hpp:142:4: note:   template argument deduction/substitution failed:
In file included from src/test_string_vector.cc:5:0:
/usr/include/boost/container/scoped_allocator.hpp:762:7: note:   candidate expects 1 argument, 0 provided
       {}
       ^
In file included from /usr/include/boost/interprocess/segment_manager.hpp:38:0,
                 from /usr/include/boost/interprocess/detail/managed_memory_impl.hpp:30,
                 from /usr/include/boost/interprocess/managed_shared_memory.hpp:25,
                 from src/test_string_vector.cc:1:
/usr/include/boost/interprocess/allocators/allocator.hpp:136:4: note: candidate: boost::interprocess::allocator<T, SegmentManager>::allocator(const boost::interprocess::allocator<T, SegmentManager>&) [with T = void; SegmentManager = boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index>]
    allocator(const allocator &other)
    ^
/usr/include/boost/interprocess/allocators/allocator.hpp:136:4: note:   candidate expects 1 argument, 0 provided
/usr/include/boost/interprocess/allocators/allocator.hpp:131:4: note: candidate: boost::interprocess::allocator<T, SegmentManager>::allocator(boost::interprocess::allocator<T, SegmentManager>::segment_manager*) [with T = void; SegmentManager = boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index>; boost::interprocess::allocator<T, SegmentManager>::segment_manager = boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index>]
    allocator(segment_manager *segment_mngr)
    ^
/usr/include/boost/interprocess/allocators/allocator.hpp:131:4: note:   candidate expects 1 argument, 0 provided
Makefile:16: recipe for target 'obj/test_string_vector.o' failed
make: *** [obj/test_string_vector.o] Error 1

Answer 1

我想我现在明白你的意图了。你想要这段代码，其中 OtherAlloc = std::allocator , Alloc = bi:allocator

template <typename OtherAlloc>
  StringVector(StringVector<OtherAlloc> const& other, Alloc alloc = Alloc())
  : mStrings(other.mStrings.begin(), other.mStrings.end(), alloc)
  {
  }

调用您提供的复制构造函数以将堆类型转换为共享类型

 template <typename OtherAlloc>
  String(String<OtherAlloc> const& other, Alloc alloc = Alloc())
  : mString(other.mString.begin(), other.mString.end(), alloc)
  {
  }

但是 boost::interprocess::vector::assign(first,last) 没有传递你的分配器实例，看起来它使用了 Alloc alloc = Alloc() where Alloc = boost::interprocess::allocator 并且它没有默认构造函数。它与我所有的帖子相关:-)我明天会尝试编写我的代码，非常具有挑战性的难题。

我今天修改了你的代码，请看下面，看看你是否喜欢它。

#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/allocators/allocator.hpp>
#include <boost/interprocess/containers/vector.hpp>
#include <boost/interprocess/containers/string.hpp>
#include <boost/container/scoped_allocator.hpp>
#include <iostream>
#include <string>
#include <sstream>
#include <algorithm>

namespace bip = boost::interprocess;

namespace generic
{

template <typename T, typename Alloc/* = std::allocator<T>*/ >
using vector = bip::vector<T, typename Alloc::template rebind<T>::other >;

template <typename Alloc/* = std::allocator<T>*/ >
using GenericString = bip::basic_string<char, std::char_traits<char>
                           , typename Alloc::template rebind<char>::other>;

template <typename Alloc>
class String
{
public:
  typedef Alloc allocator_type; // ties in with uses_allocator/scoped_allocator

  template<typename ...T>
  String(const std::string &str, T && ...t)
  : alloc_(std::forward<T>(t)...) , mString(str.c_str(), alloc_)
  {}

  template<typename ...T>
  String(const char* str, T && ...t)
  : alloc_(std::forward<T>(t)...) , mString(str, alloc_)
  {}

  template <typename OtherAlloc, typename ...T>
  String(String<OtherAlloc> const& other, T && ...t)
  : alloc_(std::forward<T>(t)...) , mString(other.mString.begin(), other.mString.end(), alloc_)
  {}

  std::string ToString() { return std::string(mString.begin(), mString.end()); }

  friend std::ostream& operator<<(std::ostream& os, const String& str)
  {
    os << str.mString;
    return os;
  }

private:
  template<typename OtherAlloc> friend struct String;
  Alloc alloc_;
  GenericString<Alloc> mString;
};

template <typename Alloc>
class StringVector
{
public:
  typedef Alloc allocator_type; // ties in with uses_allocator/scoped_allocator
  typedef vector<String<Alloc>, Alloc> GenericStringVector;
  using Iterator = typename GenericStringVector::iterator;
  using ConstIterator = typename GenericStringVector::const_iterator;

  StringVector()
  : alloc_(), mStrings(alloc_)
  {}

  template<typename T>
  StringVector(T && t)
  : alloc_(std::forward<T>(t)), mStrings(alloc_)
  {}

  template <typename OtherAlloc, typename ...T>
  StringVector(StringVector<OtherAlloc> const& other, T && ...t)
  : alloc_(std::forward<T>(t)...), mStrings(alloc_)
  {
      std::transform ( other.mStrings.begin(), other.mStrings.end(), std::back_inserter(mStrings), [&t...](auto &s) {
          return typename GenericStringVector::value_type(s, std::forward<T>(t)...);
      });
  }

  void Add(const String<Alloc> str) { mStrings.emplace_back(str); }

  void Remove(Iterator iter) { mStrings.erase(iter); }

  void Clear() { mStrings.clear(); }

  void Print() const
  {
    std::cout << "[";
    for (ConstIterator it = mStrings.begin(); it != mStrings.end(); it++)
      std::cout << (it == mStrings.begin() ? "" : ", ") << *it;
    std::cout << "]\n";
  }

private:
  template<typename OtherAlloc> friend struct StringVector;
  Alloc alloc_;
  GenericStringVector mStrings;
};

}

namespace heap
{
  using VAlloc = std::allocator<void>;
  using String = generic::String<VAlloc>;
  using StringVector = generic::StringVector<VAlloc>;
}

namespace shared
{
  using VAlloc =boost::container::scoped_allocator_adaptor<
          bip::allocator<char, bip::managed_shared_memory::segment_manager> >;

  using String = generic::String<VAlloc>;
  using StringVector = generic::StringVector<VAlloc>;
}

int main(void)
{
  struct shm_remove {
      shm_remove()  { bip::shared_memory_object::remove("MySharedMemory"); }
      ~shm_remove() { bip::shared_memory_object::remove("MySharedMemory"); }
  } remover;

  std::cout << "Heap based storage: \n";
  heap::StringVector svec;

  svec.Add(heap::String("test1"));
  svec.Add(heap::String("test2"));
  svec.Add(heap::String("test3"));
  svec.Add(heap::String("test4"));
  svec.Print();

  std::cout << "Shared memory storage: \n";
  bip::managed_shared_memory seg(bip::create_only, "MySharedMemory", 65536);
  auto smp = seg.get_segment_manager();

  shared::StringVector sh_svec(smp);
  sh_svec.Add(shared::String("test1", smp));
  sh_svec.Add(shared::String("test2", smp));
  sh_svec.Add(shared::String("test3", smp));
  sh_svec.Add(shared::String("test4", smp));
  sh_svec.Print();


  shared::StringVector sh_svec2(sh_svec, smp);
  sh_svec2.Print();

  shared::StringVector sh_svec3(svec, smp);   // does not give compile error 
  sh_svec3.Print();
}