R/context.R

In r-lib/async: Asynchronous Computation and 'I/O'

async_env <- new.env(parent = emptyenv())
async_env$loops <- list()

get_default_event_loop <- function() {
  num_loops <- length(async_env$loops)
  if (num_loops == 0) {
    err <- make_error(
      "You can only call async functions from an async context",
      class = "async_synchronization_barrier_error"
    )
    stop(err)
  }

  async_env$loops[[num_loops]]
}

push_event_loop <- function() {
  num_loops <- length(async_env$loops)
  if (num_loops > 0) async_env$loops[[num_loops]]$suspend()
  new_el <- event_loop$new()
  async_env$loops <- c(async_env$loops, list(new_el))
  new_el
}

pop_event_loop <- function() {
  num_loops <- length(async_env$loops)
  async_env$loops[[num_loops]] <- NULL
  if (num_loops > 1) async_env$loops[[num_loops - 1]]$wakeup()
}