nim-chronos

Transports are high-level interfaces for interaction with the OS IO system. The main task that the Transport concept is designed to solve is to reduce the number of syscalls and of memory allocations for performing a single IO operation.

Current version of asyncdispatch uses at least four (4) syscalls for every single IO operation.

For Linux/BSD/MacOS systems, current version of asyncdispatch performs such operations for every single IO operation:

Register for a read/write event in the system queue
Wait for an event in the system queue
Perform an IO operation
Unregister a read/write event from the system queue

For Windows system, the current version of asyncdispatch performs allocations of OVERLAPPED structure for every single IO operation.

For example

proc processSomething(socket: AsyncFD) {.async.} =
  var request = socket.recv(10)  # 4 syscalls (Posix) or 1 allocation (Windows) 
  var data = socket.recv(100)    # 4 syscalls (Posix) or 1 allocation (Windows)
  var answer = "ANSWER"
  await socket.send(answer)      # 4 syscalls (Posix) or 1 allocation (Windows)