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using Plum::BinaryString
module Plum
module HPACK
class Encoder
include HPACK::Context
def initialize(dynamic_table_limit)
super
end
def encode(headers)
out = ""
headers.each do |name, value|
name = name.to_s; value = value.to_s
if index = search(name, value)
out << encode_indexed(index)
elsif index = search(name, nil)
out << encode_half_indexed(index, value, true) # incremental indexing
else
out << encode_literal(name, value, true) # incremental indexing
end
end
out.force_encoding(Encoding::BINARY)
end
private
# +---+---+---+---+---+---+---+---+
# | 0 | 1 | 0 |
# +---+---+-----------------------+
# | H | Name Length (7+) |
# +---+---------------------------+
# | Name String (Length octets) |
# +---+---------------------------+
# | H | Value Length (7+) |
# +---+---------------------------+
# | Value String (Length octets) |
# +-------------------------------+
def encode_literal(name, value, indexing = true)
if indexing
store(name, value)
fb = "\x40"
else
fb = "\x00"
end
fb << encode_string(name) << encode_string(value)
end
# +---+---+---+---+---+---+---+---+
# | 0 | 1 | Index (6+) |
# +---+---+-----------------------+
# | H | Value Length (7+) |
# +---+---------------------------+
# | Value String (Length octets) |
# +-------------------------------+
def encode_half_indexed(index, value, indexing = true)
if indexing
store(fetch(index)[0], value)
fb = encode_integer(index, 6)
fb.setbyte(0, fb.uint8 | 0b01000000)
else
fb = encode_integer(index, 4)
end
fb << encode_string(value)
end
# +---+---+---+---+---+---+---+---+
# | 1 | Index (7+) |
# +---+---------------------------+
def encode_indexed(index)
s = encode_integer(index, 7)
s.setbyte(0, s.uint8 | 0b10000000)
s
end
def encode_integer(value, prefix_length)
mask = (1 << prefix_length) - 1
out = ""
if value < mask
out.push_uint8(value)
else
value -= mask
out.push_uint8(mask)
while value >= mask
out.push_uint8((value % 0b10000000) + 0b10000000)
value >>= 7
end
out.push_uint8(value)
end
end
def encode_string(str)
huffman_str = Huffman.encode(str).force_encoding(__ENCODING__)
if huffman_str.bytesize < str.bytesize
lenstr = encode_integer(huffman_str.bytesize, 7)
lenstr.setbyte(0, lenstr.uint8(0) | 0b10000000)
lenstr << huffman_str
else
encode_integer(str.bytesize, 7) << str
end
end
end
end
end
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