Hello,
I'm trying to write multiple variables one by one into a mapped_region,
but somehow I fail. Here is the Code I worked on so far:
boost::interprocess::shared_memory_object
shm_obj(boost::interprocess::open_or_create, "Test",
boost::interprocess::read_write);
shm_obj.truncate(1000);
boost::interprocess::mapped_region region(shm_obj,
boost::interprocess::read_write, 0, 0);
uint32_t size = 33;
uint32_t type = 666;
std::string data("I'm a Test!");
uint32_t* start_ptr_int = &(static_cast
(region.get_address())[0]);
std::memcpy(start_ptr_int, &size, sizeof (uint32_t));
start_ptr_int = &(static_cast (region.get_address())[4]);
std::memcpy(start_ptr_int, &type, sizeof (uint32_t));
char* start_ptr_char = &(static_cast (region.get_address())[8]);
std::memcpy(start_ptr_char, data.c_str(), data.length());
uint32_t sizeOfData;
std::memcpy(&sizeOfData, &(static_cast
(region.get_address())[0]), sizeof (uint32_t));
uint32_t typeOfData;
std::memcpy(&typeOfData, &(static_cast
(region.get_address())[4]), 4);
char* revData = new char[sizeOfData];
std::memcpy(revData, &(static_cast
(region.get_address())[sizeof (uint32_t) * 2]), sizeOfData);
First I write an uint32_t into the region at index 0. Afterwards, I'm
writing another uint32_t at position 4 (assuming the first uint32_t took
the bytes 0 - 3).
Last I write a string into the region, at index 8. Reading the first
uint32_t again from shared memory works fine, as does reading the string
(the last variable). But if I try to read the second variable
(uint32_t) the data is not what I expected. I know that the problem is
memcpy, somehow my syntax does not work. Unfortunately I could not find
a matching example, cause mostly memset is used to
explain the functionality of boost::mapped_region. I have to write lots
of data into shared memory (structured like
size1|type1|data1|...|sizeN|typeN|dataN) but still can't figure out how
to do this the right way.
Any suggestions are greatly appreciated.
Kind regards
Michael Behnke
--
Bachelorand
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