我在一个进程的 Boost Interprocess
map<int, vector<int>>
中创建了一个 managed_shared_memory
,然后想在另一个进程中打开它以连续写入它。
另一个进程尝试在对象的构造函数中打开共享内存Communication
,然后提供一个方法addData(int _data)
。
示例:
// Typedefs for shared data structures
using boost::interprocess;
using std::pair;
using std::scoped_allocator_adaptor;
typedef managed_shared_memory::segment_manager man;
typedef allocator <int , man> Int_Allocator;
typedef vector <int, Int_Allocator> Int_Vector;
typedef pair <const int, Int_Vector> Int_Vector_Map_Type;
typedef scoped_allocator_adaptor <allocator<Int_Vector_Map_Type, man>> Int_Vector_Map_Type_Allocator;
typedef map <int, Int_Vector, std::less<int>, Int_Vector_Map_Type_Allocator> Int_Vector_Map;
// Let's call this process 'parent'
managed_shared_memory segment(create_only, "Shared");
Int_Vector_Map_Type_Allocator alloc = segment.get_segment_manager();
segment.construct<Int_Vector_Map>("Map")(std::less<int>(), alloc);
// 'child' process
class Communciation{
Int_Vector_Map* map;
public:
Communication{
managed_shared_memory segment(open_only, "Shared");
map = segment.find<Int_Vector_Map>("Map").first;
}
void addData(int _key, int _value){
if(map->size() == 0 || map->find(_key) == map->end(){
managed_shared_memory segment(open_only, "Shared");
Int_Allocator alloc = segment.get_segment_manager();
map->insert(Int_Vector_Map_Type(_key, Int_Vector(alloc)));
} // create the vector and its allocator, otherwise runtime error
map->at(_key).push_back(_value);
}
}
这是我正在查看的内容的分解示例,但我没有看到立即错误。 当尝试运行此代码时,我收到运行时错误“未处理的异常:EXCEPTION_ACCESS_VIOLATION读取地址(...)”。 将
addData(...)
方法更改为:
void addData(int _key, int _value){
managed_shared_memory segment(open_only, "Shared");
map = segment.find<Int_Vector_Map>("Map").first;
if(map->size() == 0 || map->find(_key) == map->end(){
Int_Allocator alloc = segment.get_segment_manager();
map->insert(Int_Vector_Map_Type(_key, Int_Vector(alloc)));
} // create the vector and its allocator, otherwise runtime error
map->at(_key).push_back(_value);
}
即每次调用打开地图都会修复此问题,但不适用于我的情况,因为我希望能够每帧多次调用此方法,而不会对 fps 产生太大影响。
这个问题的原因是什么?是否可以按照描述使用 boost 的进程间?
答案有很多组成部分:
emplace
方法)我在使用 Boost Container 的实现方面拥有良好的经验,所以让我们展示一下。
// Typedefs for shared data structures
namespace bip = boost::interprocess;
namespace Shared {
namespace bc = boost::container;
using Segment = bip::managed_shared_memory;
using Mgr = Segment::segment_manager;
template <typename T> using Alloc = bc::scoped_allocator_adaptor<bip::allocator<T, Mgr>>;
template <typename T> using Vector = bc::vector<T, Alloc<T>>;
template <typename K, typename V, typename Cmp = std::less<K>, typename P = std::pair<K const, V>>
using Map = bc::map<K, V, Cmp, Alloc<P>>;
} // namespace Shared
现在您可以简单地说:
using IVMap = Shared::Map<int, Shared::Vector<int>>; // Int_Vector_Map
它将扩展到正确的比较器、分配器等集合。
要从构造函数构造段,您将需要使用初始值设定项列表。例如:
class Communication {
public:
Communication() //
: segment_{bip::open_only, "Shared"}
, map_(*segment_.find<IVMap>("Map").first) {}
void addData(int key, int value);
private:
Shared::Segment segment_;
IVMap& map_;
};
要插入新元素,请实现
addData
,例如:
void addData(int key, int value) {
auto it = map_.find(key);
if (it == map_.end())
it = map_.emplace(key).first;
it->second.push_back(value);
}
请注意,该段只是存在。请注意,由于作用域分配器适配器与
emplace
结构的结合,分配器得以传播。
编辑 遗憾的是我无法编译 emplace。我确信我错过了一些琐碎的事情,但我已经解决了这个问题,例如:
if (it == map_.end()) {
IVMap::mapped_type v(map_.get_allocator());
it = map_.emplace(key, std::move(v)).first;
}
#include <boost/container/scoped_allocator.hpp>
#include <boost/interprocess/allocators/allocator.hpp>
#include <boost/interprocess/containers/map.hpp>
#include <boost/interprocess/containers/vector.hpp>
#include <boost/interprocess/managed_mapped_file.hpp>
#include <boost/interprocess/managed_shared_memory.hpp>
#include <set>
// Typedefs for shared data structures
namespace bip = boost::interprocess;
namespace Shared {
namespace bc = boost::container;
#ifdef COLIRU // online compiler
using Segment = bip::managed_mapped_file;
#else
using Segment = bip::managed_shared_memory;
#endif
using Mgr = Segment::segment_manager;
template <typename T> using Alloc = bc::scoped_allocator_adaptor<bip::allocator<T, Mgr>>;
template <typename T> using Vector = bc::vector<T, Alloc<T>>;
template <typename K, typename V, typename Cmp = std::less<K>, typename P = std::pair<K const, V>>
using Map = bc::map<K, V, Cmp, Alloc<P>>;
} // namespace Shared
using IVMap = Shared::Map<int, Shared::Vector<int>>; // Int_Vector_Map
class Communication {
public:
Communication() //
: segment_{bip::open_only, "Shared"}
, map_(*segment_.find<IVMap>("Map").first) {}
void addData(int key, int value) {
auto it = map_.find(key);
if (it == map_.end()) {
IVMap::mapped_type v(map_.get_allocator());
it = map_.emplace(key, std::move(v)).first;
}
it->second.push_back(value);
}
auto const& get() const { return map_; }
private:
Shared::Segment segment_;
IVMap& map_;
};
#include <fmt/ranges.h>
#include <functional>
#include <random>
static auto vals = bind(std::uniform_int_distribution(100, 999), std::mt19937{std::random_device{}()});
int main(int argc, char** argv) {
auto const args = std::set<std::string_view>(argv + 1, argv + argc);
if (args.contains("parent")) {
Shared::Segment seg{bip::open_or_create, "Shared", 10 << 10};
seg.find_or_construct<IVMap>("Map")(seg.get_segment_manager());
}
if (args.contains("child")) {
Communication comm;
for (unsigned n = 10; n--;) {
auto v = vals();
comm.addData(v / 100, v);
}
fmt::print("After insertion:\n - {}\n", fmt::join(comm.get(), "\n - "));
}
}
印刷
+ ./a.out parent
+ ./a.out child
After insertion:
- (1, [155, 170])
- (2, [248])
- (4, [418])
- (5, [542, 562])
- (6, [642, 674, 659])
- (7, [783])
+ ./a.out child
After insertion:
- (1, [155, 170, 143, 130])
- (2, [248, 222])
- (3, [325])
- (4, [418, 428])
- (5, [542, 562, 556])
- (6, [642, 674, 659, 671])
- (7, [783, 793, 733, 745])
+ ./a.out child
After insertion:
- (1, [155, 170, 143, 130])
- (2, [248, 222])
- (3, [325, 320, 362])
- (4, [418, 428, 486, 437])
- (5, [542, 562, 556])
- (6, [642, 674, 659, 671, 695, 609])
- (7, [783, 793, 733, 745, 786, 777, 793])
- (9, [995])