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# The goal of this is to use a synthetic (non-IO) reader
# to trigger the read/write loop of IO.copy_stream,
# bypassing in-kernel mechanisms like sendfile for zero copy,
# so we wrap the /dev/zero IO object:
class Zero
def initialize
@n = 100000
@in = File.open('/dev/zero', 'rb')
end
def read(len, buf)
return if (@n -= 1) == 0
@in.read(len, buf)
end
end
begin
require 'socket'
src = Zero.new
rd, wr = UNIXSocket.pair
pid = fork do
wr.close
buf = String.new
while rd.read(16384, buf)
end
end
rd.close
IO.copy_stream(src, wr)
rescue Errno::ENOENT, NotImplementedError, NameError
# not *nix: missing /dev/zero, fork, or UNIXSocket
rescue LoadError # no socket?
ensure
wr.close if wr
Process.waitpid(pid) if pid
end if IO.respond_to?(:copy_stream)
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