/**
* performs validation, masking, compression, etc. will return an error if
* there was an error, otherwise msg will be ready to be written
*
* by default websocket++ performs block masking/unmasking in a manner that
* makes assumptions about the nature of the machine and stl library used.
* in particular the assumption is either a 32 or 64 bit word size and an
* stl with std::string::data returning a contiguous char array.
*
* this method improves masking performance by 3-8x depending on the ratio
* of small to large messages and the availability of a 64 bit processor.
*
* to disable this optimization (for use with alternative stl
* implementations or processors) define websocketpp_strict_masking when
* compiling the library. this will force the library to perform masking in
* single byte chunks.
*
* todo: tests
*
* @param in an unprepared message to prepare
* @param out a message to be overwritten with the prepared message
* @return error code
*/
virtual lib::error_code prepare_data_frame(message_ptr in, message_ptr out)
{
if (!in || !out) {
return make_error_code(error::invalid_arguments);
}
frame::opcode::value op = in->get_opcode();
// validate opcode: only regular data frames
if (frame::opcode::is_control(op)) {
return make_error_code(error::invalid_opcode);
}
std::string& i = in->get_raw_payload();
std::string& o = out->get_raw_payload();
// validate payload utf8
if (op == frame::opcode::text && !utf8_validator::validate(i)) {
return make_error_code(error::invalid_payload);
}
frame::masking_key_type key;
bool masked = !base::m_server;
bool compressed = m_permessage_deflate.is_enabled()
&& in->get_compressed();
bool fin = in->get_fin();
// generate header
frame::basic_header h(op,i.size(),fin,masked,compressed);
if (masked) {
// generate masking key.
key.i = m_rng();
frame::extended_header e(i.size(),key.i);
out->set_header(frame::prepare_header(h,e));
} else {
frame::extended_header e(i.size());
out->set_header(frame::prepare_header(h,e));
}
// prepare payload
if (compressed) {
// compress and store in o after header.
m_permessage_deflate.compress(i,o);
// mask in place if necessary
if (masked) {
this->masked_copy(o,o,key);
}
} else {
// no compression, just copy data into the output buffer
o.resize(i.size());
// if we are masked, have the masking function write to the output
// buffer directly to avoid another copy. if not masked, copy
// directly without masking.
if (masked) {
this->masked_copy(i,o,key);
} else {
std::copy(i.begin(),i.end(),o.begin());
}
}
out->set_prepared(true);
return lib::error_code();
}
void echo_func(server* s, websocketpp::connection_hdl hdl, message_ptr msg) {
s->send(hdl, msg->get_payload(), msg->get_opcode());
}
