Wrapper for struct msghdr for sending messages via Socket::sendMessage(). More...

#include <message_header.hxx>

Inheritance diagram for cosmos::SendMessageHeader:

Classes
class	ControlMessage
	Wrapper for `struct cmsghdr` used for creating new control messages for sending. More...

Public Attributes
WriteIOVector	iovec
	Memory regions to send.

std::optional< ControlMessage >	control_msg
	Control message to send, if any.

Protected Member Functions
void	prepareSend (const SocketAddress *addr)
	Prepare a `sendmsg()` operation using the given optional target address.

void	postSend (size_t sent)
	Perform any cleanup or bookkeeping after a successful `sendmsg()` operation.

void	setAddress (const SocketAddress &addr)
	Fill in the target address fields of the `struct msghdr` for the given address object.

const struct msghdr *	rawHeader () const
	Return a pointer to the raw `struct msghdr` for passing to the `sendmsg()` system call.

Protected Member Functions inherited from cosmos::MessageHeaderBase< msghdr_const >
void	resetAddress ()
	Reset the address portion of the msghdr struct.

void	setIov (IOVEC &iovec)
	Set the `msg_iov` fields of the msghdr struct based on the given iovector object.

MessageFlags	ioFlags () const
	Returns the currently set MessageFlags for send/receive.

Friends
class	Socket

Additional Inherited Members
Public Member Functions inherited from cosmos::MessageHeaderBase< msghdr_const >
	MessageHeaderBase ()
	Create a MSGHDR initialized to all zeroes and with default flags applied.

void	clear ()
	Clear the complete system call structure with zeroes.

void	setIOFlags (const MessageFlags flags)
	Set the flags used for sending or receiving data.

Protected Attributes inherited from cosmos::MessageHeaderBase< msghdr_const >
msghdr_const	m_header
	The low level `struct msghdr`

MessageFlags	m_io_flags
	The currently configured send/receive flags.

Detailed Description

Wrapper for struct msghdr for sending messages via Socket::sendMessage().

This type holds extended data for sending a message over a socket. For one it allows sending data from multiple scattered memory regions using a WriteIOVector. Furthermore additional ancillary data can be sent. Both of these items can be set using the public members iovec and control_msg. These variables will be applied when passing the SendMessageHeader to Socket::sendMessage() or one of its specializations.

Libcosmos currently only supports sending a single control message at once. The ControlMessage type can only be constructed by special types that know how to serialize one like the UnixRightsMessage type for sending file descriptors over a UNIX domain socket.

There are some restrictions when sending ancillary data. With SocketType::STREAM sockets ancillary data must always be accompanied by some payload data. If no payload data is otherwise available then a dummy byte needs to be sent to make it possible to send ancillary data. On SocketType::DGRAM sockets on Linux it is also possible to send ancillary data without any payload.

Definition at line 141 of file message_header.hxx.

Member Function Documentation

◆ postSend()

void cosmos::SendMessageHeader::postSend ( size_t sent )

inlineprotected

Perform any cleanup or bookkeeping after a successful sendmsg() operation.

Definition at line 222 of file message_header.hxx.

                                   {
                iovec.update(sent);
                control_msg.reset();
        }

◆ prepareSend()

void cosmos::SendMessageHeader::prepareSend ( const SocketAddress * addr )

protected

Prepare a sendmsg() operation using the given optional target address.

Definition at line 25 of file message_header.cxx.

                                                             {
        if (addr) {
                setAddress(*addr);
        } else {
                resetAddress();
        }
 
        setIov(iovec);
 
        if (control_msg) {
                m_header.msg_control = control_msg->raw();
                m_header.msg_controllen = control_msg->size();
        } else {
                m_header.msg_control = nullptr;
                m_header.msg_controllen = 0;
        }
}

◆ rawHeader()

const struct msghdr * cosmos::SendMessageHeader::rawHeader ( ) const

inlineprotected

Return a pointer to the raw struct msghdr for passing to the sendmsg() system call.

Definition at line 231 of file message_header.hxx.

                                               {
                return reinterpret_cast<const struct msghdr*>(&m_header);
        }

◆ setAddress()

void cosmos::SendMessageHeader::setAddress ( const SocketAddress & addr )

protected

Fill in the target address fields of the struct msghdr for the given address object.

Definition at line 12 of file message_header.cxx.

                                                            {
        m_header.msg_name = reinterpret_cast<const void*>(addr.basePtr());
        m_header.msg_namelen = addr.size();
}

Friends And Related Symbol Documentation

◆ Socket

friend class Socket

friend

Definition at line 143 of file message_header.hxx.

Member Data Documentation

◆ control_msg

std::optional<ControlMessage> cosmos::SendMessageHeader::control_msg

Control message to send, if any.

Definition at line 214 of file message_header.hxx.

◆ iovec

WriteIOVector cosmos::SendMessageHeader::iovec

Memory regions to send.

Definition at line 212 of file message_header.hxx.

The documentation for this class was generated from the following files:

include/net/message_header.hxx
src/net/message_header.cxx

Classes

Public Attributes

Protected Member Functions

Friends

Additional Inherited Members