Instantiating class with custom allocator in shared memory
- by recipriversexclusion
I'm pulling my hair due to the following problem: I am following the example given in boost.interprocess documentation to instantiate a fixed-size ring buffer buffer class that I wrote in shared memory. The skeleton constructor for my class is:
template<typename ItemType, class Allocator >
SharedMemoryBuffer<ItemType, Allocator>::SharedMemoryBuffer( unsigned long capacity ){
m_capacity = capacity;
// Create the buffer nodes.
m_start_ptr = this->allocator->allocate(); // allocate first buffer node
BufferNode* ptr = m_start_ptr;
for( int i = 0 ; i < this->capacity()-1; i++ ) {
BufferNode* p = this->allocator->allocate(); // allocate a buffer node
}
}
My first question: Does this sort of allocation guarantee that the buffer nodes are allocated in contiguous memory locations, i.e. when I try to access the n'th node from address m_start_ptr + n*sizeof(BufferNode) in my Read() method would it work? If not, what's a better way to keep the nodes, creating a linked list?
My test harness is the following:
// Define an STL compatible allocator of ints that allocates from the managed_shared_memory.
// This allocator will allow placing containers in the segment
typedef allocator<int, managed_shared_memory::segment_manager> ShmemAllocator;
//Alias a vector that uses the previous STL-like allocator so that allocates
//its values from the segment
typedef SharedMemoryBuffer<int, ShmemAllocator> MyBuf;
int main(int argc, char *argv[])
{
shared_memory_object::remove("MySharedMemory");
//Create a new segment with given name and size
managed_shared_memory segment(create_only, "MySharedMemory", 65536);
//Initialize shared memory STL-compatible allocator
const ShmemAllocator alloc_inst (segment.get_segment_manager());
//Construct a buffer named "MyBuffer" in shared memory with argument alloc_inst
MyBuf *pBuf = segment.construct<MyBuf>("MyBuffer")(100, alloc_inst);
}
This gives me all kinds of compilation errors related to templates for the last statement. What am I doing wrong?
