Codec

tags : Custom Protocols, Systems, System Design

What? §

• Codec stands for code/decode
• It’s a reversible method for converting interesting things into completely uninteresting and useless numbers … and then converting those uninteresting and useless numbers back into interesting things again.

A streaming codec loop §

• Protocols wrap protocols. Binary protocols boils down to:
  • Getting how many bytes are coming next
  • Writing the buffer with the meaning of the data(meaningless to the protocol itself).
• Start by writing two threads, TcpListener and the other has a TcpStream that connects to the listener
• Have them send messages back and forth that begin with 8 byte fixed-size frame delimiters.
  • The frame delimiter says how many bytes are coming.
• The codec loop is trivial
  • Read 8 bytes, turn it into a u64
  • Read that many bytes into a new buffer that will be interpreted as the actual message.
  • Eg. 2 a b 3 a b c 1 a will turn into 3 messages: ab, abc, a.
• A Frame is essentially (size, message), these can be refereed to as “framed protocols”.