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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
src = Zero.new
dst = File.open(IO::NULL, 'wb')
n = IO.copy_stream(src, dst)
rescue Errno::ENOENT
# not *nix
end if IO.respond_to?(:copy_stream) && IO.const_defined?(:NULL)
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