# access a user file; one instance per open file
resource FileServer
  import Defs
  op fopen(name user, name fname, accessmode m) returns file_descriptor  fd
body FileServer()

  proc fopen(user, fname, m) returns fd  {
    op fread rd
    op fwrite wr
    op fclose cl		# local operations
    file f = open("dfs/" || user || "/" || fname, m)
    if (f == null) {    # cannot open file
      fd = file_descriptor(null, null, null)
      reply
      destroy myresource()
    }
    fd = file_descriptor(rd, wr, cl)
    reply    # return result to invoker
    while (true) {
      in rd(ln) returns status ->
	  ln = ""    # to handle EOF properly
	  status = read(f, ln)
      [] wr(ln) -> write(f, ln)
      [] cl() -> close(f); exit
      ni
    }
    destroy myresource()
  }
end FileServer