CODEWITHSUNDEEP
c++socketsbooststructboost-asio
DEEPANSH NAGARIA
DEEPANSH NAGARIA

Reputation: 113

How to pass packed structs as messages in boost::asio? (without serialization)

I am boost::asio, the messages and responses are all in the form of packed structs, and as the structs are packed I don't see a use of serialization here. I have seen similar questions and all advice serialization, but that is not what I am looking for. How can we pass and receive a objects of these structs over a tcp connection boost::asio? I am new to boost and just exploring it so a code example will be of much help. thanks in advance.

Example struct:

typedef struct { 
    MessageHeaderInComp MessageHeaderIn;
    RequestHeaderComp RequestHeader;
    uint32_t Username;
    char Password[LEN_PASSWORD];
    char Pad4[LEN_PAD4];


} __attribute__((packed)) UserLoginRequest;

Upvotes: 1

Views: 765

Answers (1)

sehe
sehe

Reputation: 393134

If you mean that the "packed struct" is actually POD (so standard-layour and trivially constructible/destructible), in short bitwise serializable, then you could say that your struct is a buffer.

Indeed, you may decide that you don't need to copy into another buffer/representation and use the buffer. That's simple, just adapt your object as a buffer: 

UserLoginRequest req;
write(socket_or_stream, boost::asio::buffer(&req, sizeof(req)));
read(socket_or_stream, boost::asio::buffer(&req, sizeof(req)));

To avoid doing the math I prefer to use array declaration:

UserLoginRequest req[1];
write(socket_or_stream, boost::asio::buffer(req));
read(socket_or_stream, boost::asio::buffer(req));

Of course on async streams or sockets the async_* variants can be used as well (given that the lifetime of the buffer extends to completion of the operation as always).

More

Related, you can contiguous storage of POD types as a buffer:

std::vector<UserLoginRequest> massLogin(123); // weird, but just for demo
write(socket_or_stream, boost::asio::buffer(massLogin));
read(socket_or_stream, boost::asio::buffer(massLogin));

Caveat

This kind of bitwise serialization is NOT PORTABLE. I'm assuming that you are well aware of this and don't mind.

Bonus links

Upvotes: 1

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