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|
# frozen-string-literal: true
using Plum::BinaryString
module Plum
module HPACK
class Decoder
include HPACK::Context
def initialize(dynamic_table_limit)
super
end
def decode(str)
headers = []
pos = 0
lpos = str.bytesize
while pos < lpos
l, succ = parse(str, pos)
pos += succ
headers << l if l
end
headers
end
private
def parse(str, pos)
first_byte = str.getbyte(pos)
if first_byte >= 0x80 # 0b1XXXXXXX
parse_indexed(str, pos)
elsif first_byte >= 0x40 # 0b01XXXXXX
parse_indexing(str, pos)
elsif first_byte >= 0x20 # 0b001XXXXX
self.limit, succ = read_integer(str, pos, 5)
[nil, succ]
else # 0b0000XXXX (without indexing) or 0b0001XXXX (never indexing)
parse_no_indexing(str, pos)
end
end
def read_integer(str, pos, prefix_length)
raise HPACKError.new("integer: end of buffer") if str.empty?
mask = 1 << prefix_length
ret = str.getbyte(pos) % mask
return [ret, 1] if ret != mask - 1
octets = 0
while next_value = str.uint8(pos + octets + 1)
ret += (next_value % 0x80) << (7 * octets)
octets += 1
if next_value < 0x80
return [ret, 1 + octets]
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, pos)
raise HPACKError.new("string: end of buffer") if str.empty?
first_byte = str.uint8(pos)
huffman = first_byte > 0x80
length, ilen = read_integer(str, pos, 7)
raise HTTPError.new("string: end of buffer") if str.bytesize < length
bin = str.byteslice(pos + ilen, length)
if huffman
[Huffman.decode(bin), ilen + length]
else
[bin, ilen + length]
end
end
def parse_indexed(str, pos)
# indexed
# +---+---+---+---+---+---+---+---+
# | 1 | Index (7+) |
# +---+---------------------------+
index, succ = read_integer(str, pos, 7)
[fetch(index), succ]
end
def parse_indexing(str, pos)
# +---+---+---+---+---+---+---+---+
# | 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) |
# +-------------------------------+
ret, len = parse_literal(str, pos, 6)
store(*ret)
[ret, len]
end
def parse_no_indexing(str, pos)
# +---+---+---+---+---+---+---+---+
# | 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) |
# +-------------------------------+
ret, len = parse_literal(str, pos, 4)
[ret, len]
end
def parse_literal(str, pos, pref)
index, ilen = read_integer(str, pos, pref)
if index == 0
name, nlen = read_string(str, pos + ilen)
else
name, = fetch(index)
nlen = 0
end
val, vlen = read_string(str, pos + ilen + nlen)
[[name, val], ilen + nlen + vlen]
end
end
end
end
|
