`class Frame`

Definitions

`VALID_STREAM_ID = 0..0x7fffffff`

Stream Identifier cannot be bigger than this: https://http2.github.stream/http2-spec/#rfc.section.4.1

`VALID_LENGTH = 0..0xffffff`

The absolute maximum bounds for the length field:

`LENGTH_HISHIFT = 16`

Used for generating 24-bit frame length:

`TYPE = nil`

The base class does not have any specific type index:

`def initialize(stream_id = 0, flags = 0, type = self.class::TYPE, length = nil, payload = nil)`

Implementation

def initialize(stream_id = 0, flags = 0, type = self.class::TYPE, length = nil, payload = nil)
	@stream_id = stream_id
	@flags = flags
	@type = type
	@length = length
	@payload = payload
end

`def connection?`

Check if frame is a connection frame: SETTINGS, PING, GOAWAY, and any frame addressed to stream ID = 0.

Implementation

def connection?
	@stream_id.zero?
end

`def header`

Generates common 9-byte frame header.

http://tools.ietf.org/html/draft-ietf-httpbis-http2-16#section-4.1

Implementation

def header
	unless VALID_LENGTH.include? @length
		raise ProtocolError, "Invalid frame length: #{@length.inspect}"
	end
	
	unless VALID_STREAM_ID.include? @stream_id
		raise ProtocolError, "Invalid stream identifier: #{@stream_id.inspect}"
	end
	
	[
		# These are guaranteed correct due to the length check above.
		@length >> LENGTH_HISHIFT,
		@length & LENGTH_LOMASK,
		@type,
		@flags,
		@stream_id
	].pack(HEADER_FORMAT)
end

`def self.parse_header(buffer)`

Decodes common 9-byte header.

Implementation

def self.parse_header(buffer)
	length_hi, length_lo, type, flags, stream_id = buffer.unpack(HEADER_FORMAT)
	length = (length_hi << LENGTH_HISHIFT) | length_lo
	stream_id = stream_id & STREAM_ID_MASK
	
	# puts "parse_header: length=#{length} type=#{type} flags=#{flags} stream_id=#{stream_id}"
	
	return length, type, flags, stream_id
end