Class: HTTP2::Header::Decompressor

Inherits:
Object
  • Object
show all
Includes:
BufferUtils, Error
Defined in:
lib/http/2/header/decompressor.rb

Overview

Responsible for decoding received headers and maintaining compression context of the opposing peer. Decompressor must be initialized with appropriate starting context based on local role: client or server.

Examples:

server_role = Decompressor.new(:request)
client_role = Decompressor.new(:response)

Constant Summary collapse

FORBIDDEN_HEADERS = 
%w[connection te].freeze

Instance Method Summary collapse

Methods included from BufferUtils

#append_str, #read_str, #read_uint32, #shift_byte

Constructor Details

#initialize(options = {}) ⇒ Decompressor

Returns a new instance of Decompressor.

Parameters:

  • options (Hash) (defaults to: {}) —

    decoding options. Only :table_size is effective.



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# File 'lib/http/2/header/decompressor.rb', line 19

def initialize(options = {})
  @cc = EncodingContext.new(options)
end

Instance Method Details

#decode(buf, frame = nil) ⇒ Array

Decodes and processes header commands within provided buffer.

Parameters:

  • buf (Buffer)
  • frame (HTTP2::Frame, nil) (defaults to: nil)

Returns:

  • (Array) —

    +[[name, value], …]



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# File 'lib/http/2/header/decompressor.rb', line 116

def decode(buf, frame = nil)
  list = []
  decoding_pseudo_headers = true
  @cc.listen_on_table do
    until buf.empty?
      field, value = @cc.process(header(buf))
      next if field.nil?

      is_pseudo_header = field.start_with?(":")
      if !decoding_pseudo_headers && is_pseudo_header
        raise ProtocolError, "one or more pseudo headers encountered after regular headers"
      end

      decoding_pseudo_headers = is_pseudo_header
      raise ProtocolError, "invalid header received: #{field}" if FORBIDDEN_HEADERS.include?(field)

      if frame
        case field
        when ":status"
          frame[:status] = Integer(value)
        when ":method"
          frame[:method] = value
        when "content-length"
          frame[:content_length] = Integer(value)
        when "trailer"
          (frame[:trailer] ||= []) << value
        end
      end
      list << [field, value]
    end
  end
  list
end

#header(buf) ⇒ Hash

Decodes header command from provided buffer.

Parameters:

  • buf (Buffer)

Returns:

  • (Hash) —

    command

Raises:



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# File 'lib/http/2/header/decompressor.rb', line 78

def header(buf)
  peek = buf.getbyte(0)

  header_type, type = HEADREP.find do |_, desc|
    mask = (peek >> desc[:prefix]) << desc[:prefix]
    mask == desc[:pattern]
  end

  raise CompressionError unless header_type && type

  header_name = integer(buf, type[:prefix])

  case header_type
  when :indexed
    raise CompressionError if header_name.zero?

    header_name -= 1

    { type: header_type, name: header_name }
  when :changetablesize
    { type: header_type, name: header_name, value: header_name }
  else
    if header_name.zero?
      header_name = string(buf)
    else
      header_name -= 1
    end
    header_value = string(buf)

    { type: header_type, name: header_name, value: header_value }
  end
end

#integer(buf, n) ⇒ Integer

Decodes integer value from provided buffer.

Parameters:

  • buf (String)
  • n (Integer) —

    number of available bits

Returns:

  • (Integer) 


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# File 'lib/http/2/header/decompressor.rb', line 34

def integer(buf, n)
  limit = (1 << n) - 1
  i = n.zero? ? 0 : (shift_byte(buf) & limit)

  m = 0
  if i == limit
    offset = 0

    buf.each_byte.with_index do |byte, idx|
      offset = idx
      # while (byte = shift_byte(buf))
      i += ((byte & 127) << m)
      m += 7

      break if byte.nobits?(128)
    end

    read_str(buf, offset + 1)
  end

  i
end

#string(buf) ⇒ String

Decodes string value from provided buffer.

Parameters:

  • buf (String)

Returns:

  • (String) —

    UTF-8 encoded string

Raises:



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# File 'lib/http/2/header/decompressor.rb', line 62

def string(buf)
  raise CompressionError, "invalid header block fragment" if buf.empty?

  huffman = buf.getbyte(0).allbits?(0x80)
  len = integer(buf, 7)
  str = read_str(buf, len)
  raise CompressionError, "string too short" unless str.bytesize == len

  str = Huffman.decode(str) if huffman
  str.force_encoding(Encoding::UTF_8)
end

#table_size=(size) ⇒ Object

Set dynamic table size in EncodingContext

Parameters:

  • size (Integer) —

    new dynamic table size



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# File 'lib/http/2/header/decompressor.rb', line 25

def table_size=(size)
  @cc.table_size = size
end