This is fstrm, a C implementation of the Frame Streams data transport protocol.

Frame Streams is a light weight, binary clean protocol that allows for the
transport of arbitrarily encoded data payload sequences with minimal framing
overhead -- just four bytes per data frame. Frame Streams does not specify an
encoding format for data frames and can be used with any data serialization
format that produces byte sequences, such as Protocol Buffers, XML, JSON,
MessagePack, YAML, etc. Frame Streams can be used as both a streaming transport
over a reliable byte stream socket (TCP sockets, TLS connections, AF_UNIX
sockets, etc.) for data in motion as well as a file format for data at rest. A
"Content Type" header identifies the type of payload being carried over an
individual Frame Stream and allows cooperating programs to determine how to
interpret a given sequence of data payloads.

fstrm is an optimized C implementation of Frame Streams that includes a fast,
lockless circular queue implementation and exposes library interfaces for
setting up a dedicated Frame Streams I/O thread and asynchronously submitting
data frames for transport from worker threads. It was originally written to
facilitate the addition of high speed binary logging to DNS servers written in
C using the dnstap log format.