#  File src/library/parallel/R/worker.R
#  Part of the R package, https://www.R-project.org
#
#  Copyright (C) 1995-2012 The R Core Team
#
#  This program is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation; either version 2 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  A copy of the GNU General Public License is available at
#  https://www.R-project.org/Licenses/

## Derived from snow 0.3-6 by Luke Tierney

slaveLoop <- function(master)
{
    repeat
        tryCatch({
            msg <- recvData(master)
            # cat(paste("Type:", msg$type, "\n"))

            if (msg$type == "DONE") {
                closeNode(master)
                break;
            } else if (msg$type == "EXEC") {
                success <- TRUE
                ## This uses the message rather than the exception since
                ## the exception class/methods may not be available on the
                ## master.
                handler <- function(e) {
                    success <<- FALSE
                    structure(conditionMessage(e),
                              class = c("snow-try-error","try-error"))
                }
                t1 <- proc.time()
                value <- tryCatch(do.call(msg$data$fun, msg$data$args, quote = TRUE),
                                  error = handler)
                t2 <- proc.time()
                value <- list(type = "VALUE", value = value, success = success,
                              time = t2 - t1, tag = msg$data$tag)
                msg <- NULL ## release for GC
                sendData(master, value)
                value <- NULL ## release for GC
            }
        }, interrupt = function(e) NULL)
}

## NB: this only sinks the connections, not C-level stdout/err.
sinkWorkerOutput <- function(outfile)
{
    if (nzchar(outfile)) {
        if (.Platform$OS.type == "windows" && outfile == "/dev/null")
            outfile <- "nul:"
        ## all the workers log to the same file.
        outcon <- file(outfile, open = "a")
        sink(outcon)
        sink(outcon, type = "message")
    }
}