创建字符串的共享内存向量

Question

我正在尝试创建一个管理(std)字符串的共享内存向量的类.

typedef boost::interprocess::allocator<std::string, boost::interprocess::managed_shared_memory::segment_manager> shmem_allocator;
typedef boost::interprocess::vector<std::string, shmem_allocator> shmem_vector;

shmem_mgr::shmem_mgr() :
    shmem_(create_only, SHMEM_KEY, SHMEM_SIZE),
    allocator_(shmem_.get_segment_manager())
{
    mutex_  = shmem_.find_or_construct<interprocess_mutex>(SHMEM_MUTEX)();
    condition_ = shmem_.find_or_construct<interprocess_condition>(SHMEM_CONDITION)();
    //buffer_ is of type shmem_vector
    buffer_  = shmem_.construct<shmem_vector>(SHMEM_BUFFER_KEY)(allocator_);
}

void shmem_mgr::run() {
    running_ = true;

    while(running_) {
        scoped_lock<interprocess_mutex> lock ( *mutex_ );

        int size = buffer_->size();

        log_.debug() << size << " queued request(s) found" << std::endl; //LINE 27
        for(int i=0; i<size; i++) {
            log_.debug() << buffer_->at(i); // at() crashes my app
        }

        buffer_->clear(); //so does clear()
        condition_->wait (lock);
    }
}

客户端成功地向向量添加一个字符串(它也成功从缓冲区读取该字符串以进行调试),管理器(上面的代码)接收信号(condtion变量),写入向量中有一个字符串(第27行) ),但当它试图通过at()应用程序崩溃获取该字符串.

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编辑:我已经想通了,使用std::string是不可能的,string在这种情况下,boost ipc中有一个容器.这并没有改变我需要(boost/std)字符串向量的事实......

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问:如何在共享内存中传递字符串？我需要将它们存储在某个缓冲区(能够一次存储> 1)中,然后在第二个进程中获取 - 这是要求.输入始终std::string是输出,输出也是如此,但shmem中的内部表示可能不同.

Answer 1

来自文档.

#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/containers/vector.hpp>
#include <boost/interprocess/containers/string.hpp>
#include <boost/interprocess/allocators/allocator.hpp>

int main ()
{
   using namespace boost::interprocess;
   //Typedefs
   typedef allocator<char, managed_shared_memory::segment_manager>
      CharAllocator;
   typedef basic_string<char, std::char_traits<char>, CharAllocator>
      MyShmString;
   typedef allocator<MyShmString, managed_shared_memory::segment_manager>
      StringAllocator;
   typedef vector<MyShmString, StringAllocator>
      MyShmStringVector;

   //Open shared memory
   //Remove shared memory on construction and destruction
   struct shm_remove
   {
      shm_remove() { shared_memory_object::remove("MySharedMemory"); }
      ~shm_remove(){ shared_memory_object::remove("MySharedMemory"); }
   } remover;

   managed_shared_memory shm(create_only, "MySharedMemory", 10000);

   //Create allocators
   CharAllocator     charallocator  (shm.get_segment_manager());
   StringAllocator   stringallocator(shm.get_segment_manager());

   //This string is in only in this process (the pointer pointing to the
   //buffer that will hold the text is not in shared memory).
   //But the buffer that will hold "this is my text" is allocated from
   //shared memory
   MyShmString mystring(charallocator);
   mystring = "this is my text";

   //This vector is only in this process (the pointer pointing to the
   //buffer that will hold the MyShmString-s is not in shared memory).
   //But the buffer that will hold 10 MyShmString-s is allocated from
   //shared memory using StringAllocator. Since strings use a shared
   //memory allocator (CharAllocator) the 10 buffers that hold
   //"this is my text" text are also in shared memory.
   MyShmStringVector myvector(stringallocator);
   myvector.insert(myvector.begin(), 10, mystring);

   //This vector is fully constructed in shared memory. All pointers
   //buffers are constructed in the same shared memory segment
   //This vector can be safely accessed from other processes.
   MyShmStringVector *myshmvector =
      shm.construct<MyShmStringVector>("myshmvector")(stringallocator);
   myshmvector->insert(myshmvector->begin(), 10, mystring);

   //Destroy vector. This will free all strings that the vector contains
   shm.destroy_ptr(myshmvector);
   return 0;
}