119 lines
3.6 KiB
Ruby
119 lines
3.6 KiB
Ruby
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module EventMachine
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# Streams a file over a given connection. Streaming begins once the object is
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# instantiated. Typically FileStreamer instances are not reused.
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#
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# Streaming uses buffering for files larger than 16K and uses so-called fast file reader (a C++ extension)
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# if available (it is part of eventmachine gem itself).
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#
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# @example
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#
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# module FileSender
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# def post_init
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# streamer = EventMachine::FileStreamer.new(self, '/tmp/bigfile.tar')
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# streamer.callback{
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# # file was sent successfully
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# close_connection_after_writing
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# }
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# end
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# end
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#
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#
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# @author Francis Cianfrocca
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class FileStreamer
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include Deferrable
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# Use mapped streamer for files bigger than 16k
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MappingThreshold = 16384
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# Wait until next tick to send more data when 50k is still in the outgoing buffer
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BackpressureLevel = 50000
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# Send 16k chunks at a time
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ChunkSize = 16384
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# @param [EventMachine::Connection] connection
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# @param [String] filename File path
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#
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# @option args [Boolean] :http_chunks (false) Use HTTP 1.1 style chunked-encoding semantics.
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def initialize connection, filename, args = {}
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@connection = connection
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@http_chunks = args[:http_chunks]
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if File.exist?(filename)
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@size = File.size(filename)
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if @size <= MappingThreshold
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stream_without_mapping filename
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else
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stream_with_mapping filename
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end
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else
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fail "file not found"
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end
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end
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# @private
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def stream_without_mapping filename
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if @http_chunks
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@connection.send_data "#{@size.to_s(16)}\r\n"
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@connection.send_file_data filename
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@connection.send_data "\r\n0\r\n\r\n"
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else
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@connection.send_file_data filename
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end
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succeed
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end
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private :stream_without_mapping
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# @private
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def stream_with_mapping filename
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ensure_mapping_extension_is_present
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@position = 0
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@mapping = EventMachine::FastFileReader::Mapper.new filename
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stream_one_chunk
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end
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private :stream_with_mapping
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# Used internally to stream one chunk at a time over multiple reactor ticks
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# @private
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def stream_one_chunk
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loop {
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if @position < @size
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if @connection.get_outbound_data_size > BackpressureLevel
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EventMachine::next_tick {stream_one_chunk}
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break
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else
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len = @size - @position
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len = ChunkSize if (len > ChunkSize)
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@connection.send_data( "#{len.to_s(16)}\r\n" ) if @http_chunks
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@connection.send_data( @mapping.get_chunk( @position, len ))
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@connection.send_data("\r\n") if @http_chunks
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@position += len
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end
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else
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@connection.send_data "0\r\n\r\n" if @http_chunks
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@mapping.close
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succeed
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break
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end
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}
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end
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#
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# We use an outboard extension class to get memory-mapped files.
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# It's outboard to avoid polluting the core distro, but that means
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# there's a "hidden" dependency on it. The first time we get here in
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# any run, try to load up the dependency extension. User code will see
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# a LoadError if it's not available, but code that doesn't require
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# mapped files will work fine without it. This is a somewhat difficult
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# compromise between usability and proper modularization.
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#
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# @private
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def ensure_mapping_extension_is_present
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@@fastfilereader ||= (require 'fastfilereaderext')
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end
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private :ensure_mapping_extension_is_present
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end # FileStreamer
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end # EventMachine
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