c++ - Direct boost serialization to char array

Question

Boost serialization doc's assert that the way to serialize/deserialize items is using a binary/text archive with a stream on the underlying structure. This works fine if I wan't to use the serialized data as an std::string, but my intention is to convert it directly to a char* buffer. How can I achieve this without creating a temporary string?

Solved! For the ones that wanted a example:

char buffer[4096];

boost::iostreams::basic_array_sink<char> sr(buffer, buffer_size);  
boost::iostreams::stream< boost::iostreams::basic_array_sink<char> > source(sr);

boost::archive::binary_oarchive oa(source);

oa << serializable_object; 

Answer 1

If you do not know the size of the data you are sending in advance, this is a generic way to serialize into an std::string:

// serialize obj into an std::string
std::string serial_str;
boost::iostreams::back_insert_device<std::string> inserter(serial_str);
boost::iostreams::stream<boost::iostreams::back_insert_device<std::string> > s(inserter);
boost::archive::binary_oarchive oa(s);

oa << obj;

// don't forget to flush the stream to finish writing into the buffer
s.flush();

// now you get to const char* with serial_str.data() or serial_str.c_str()

To deserialize, use

// wrap buffer inside a stream and deserialize serial_str into obj
boost::iostreams::basic_array_source<char> device(serial_str.data(), serial_str.size());
boost::iostreams::stream<boost::iostreams::basic_array_source<char> > s(device);
boost::archive::binary_iarchive ia(s);
ia >> obj;

This works like a charm, I use this to send data around with MPI.

This can be done very fast if you keep the serial_str in memory, and just call serial_str.clear() before you serialize into it. This clears the data but does not free any memory, so no allocation will happen when your next serialization data size does not require it.