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using Plum::BinaryString
module Plum
module HPACK
class Decoder
include HPACK::Context
def initialize(dynamic_table_limit)
super
end
def decode(str)
str = str.dup
headers = []
headers << parse!(str) while str.size > 0
headers.compact
end
private
def parse!(str)
first_byte = str.uint8
if first_byte >= 128 # 0b1XXXXXXX
parse_indexed!(str)
elsif first_byte >= 64 # 0b01XXXXXX
parse_indexing!(str)
elsif first_byte >= 32 # 0b001XXXXX
self.limit = read_integer!(str, 5)
nil
else # 0b0000XXXX (without indexing) or 0b0001XXXX (never indexing)
parse_no_indexing!(str)
end
end
def read_integer!(str, prefix_length)
first_byte = str.byteshift(1).uint8
raise HPACKError.new("integer: end of buffer") unless first_byte
mask = (1 << prefix_length) - 1
ret = first_byte & mask
return ret if ret < mask
octets = 0
while next_value = str.byteshift(1).uint8
ret += (next_value & 0b01111111) << (7 * octets)
octets += 1
if next_value < 128
return ret
elsif octets == 4 # RFC 7541 5.1 tells us that we MUST have limitation. at least > 2 ** 28
raise HPACKError.new("integer: too large integer")
end
end
raise HPACKError.new("integer: end of buffer")
end
def read_string!(str)
first_byte = str.uint8
raise HPACKError.new("string: end of buffer") unless first_byte
huffman = (first_byte >> 7) == 1
length = read_integer!(str, 7)
bin = str.byteshift(length)
raise HTTPError.new("string: end of buffer") if bin.bytesize < length
bin = Huffman.decode(bin) if huffman
bin
end
def parse_indexed!(str)
# indexed
# +---+---+---+---+---+---+---+---+
# | 1 | Index (7+) |
# +---+---------------------------+
index = read_integer!(str, 7)
fetch(index)
end
def parse_indexing!(str)
# +---+---+---+---+---+---+---+---+
# | 0 | 1 | Index (6+) |
# +---+---+-----------------------+
# | H | Value Length (7+) |
# +---+---------------------------+
# | Value String (Length octets) |
# +-------------------------------+
# or
# +---+---+---+---+---+---+---+---+
# | 0 | 1 | 0 |
# +---+---+-----------------------+
# | H | Name Length (7+) |
# +---+---------------------------+
# | Name String (Length octets) |
# +---+---------------------------+
# | H | Value Length (7+) |
# +---+---------------------------+
# | Value String (Length octets) |
# +-------------------------------+
index = read_integer!(str, 6)
if index == 0
name = read_string!(str)
else
name, = fetch(index)
end
val = read_string!(str)
store(name, val)
[name, val]
end
def parse_no_indexing!(str)
# +---+---+---+---+---+---+---+---+
# | 0 | 0 | 0 |0,1| Index (4+) |
# +---+---+-----------------------+
# | H | Value Length (7+) |
# +---+---------------------------+
# | Value String (Length octets) |
# +-------------------------------+
# or
# +---+---+---+---+---+---+---+---+
# | 0 | 0 | 0 |0,1| 0 |
# +---+---+-----------------------+
# | H | Name Length (7+) |
# +---+---------------------------+
# | Name String (Length octets) |
# +---+---------------------------+
# | H | Value Length (7+) |
# +---+---------------------------+
# | Value String (Length octets) |
# +-------------------------------+
index = read_integer!(str, 4)
if index == 0
name = read_string!(str)
else
name, = fetch(index)
end
val = read_string!(str)
[name, val]
end
end
end
end
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