Class: HTTP2::Header::Decompressor

Inherits:
Object
  • Object
show all
Defined in:
lib/http/2/compressor.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.

Instance Method Summary collapse

Constructor Details

#initialize(**options) ⇒ Decompressor

Returns a new instance of Decompressor.

Parameters:

  • options (Hash) —

    decoding options. Only :table_size is effective.

See Also:



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# File 'lib/http/2/compressor.rb', line 474

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

Instance Method Details

#decode(buf) ⇒ Array

Decodes and processes header commands within provided buffer.

Parameters:

Returns:

  • (Array) —

    [[name, value], …]



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# File 'lib/http/2/compressor.rb', line 561

def decode(buf)
  list = []
  decoding_pseudo_headers = true
  until buf.empty?
    next_header = @cc.process(header(buf))
    next if next_header.nil?

    is_pseudo_header = next_header.first.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
    list << next_header
  end
  list
end

#header(buf) ⇒ Hash

Decodes header command from provided buffer.

Parameters:

Returns:

  • (Hash) —

    command

Raises:

  • (CompressionError) 


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# File 'lib/http/2/compressor.rb', line 525

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

  header = {}
  header[:type], type = HEADREP.find do |_t, desc|
    mask = (peek >> desc[:prefix]) << desc[:prefix]
    mask == desc[:pattern]
  end

  raise CompressionError unless header[:type]

  header[:name] = integer(buf, type[:prefix])

  case header[:type]
  when :indexed
    raise CompressionError if (header[:name]).zero?

    header[:name] -= 1
  when :changetablesize
    header[:value] = header[:name]
  else
    if (header[:name]).zero?
      header[:name] = string(buf)
    else
      header[:name] -= 1
    end
    header[:value] = string(buf)
  end

  header
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/compressor.rb', line 489

def integer(buf, n)
  limit = (2**n) - 1
  i = n.zero? ? 0 : (buf.getbyte & limit)

  m = 0
  if i == limit
    while (byte = buf.getbyte)
      i += ((byte & 127) << m)
      m += 7

      break if (byte & 128).zero?
    end
  end

  i
end

#string(buf) ⇒ String

Decodes string value from provided buffer.

Parameters:

  • buf (String)

Returns:

  • (String) —

    UTF-8 encoded string

Raises:

  • (CompressionError) —

    when input is malformed



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# File 'lib/http/2/compressor.rb', line 511

def string(buf)
  huffman = (buf.readbyte(0) & 0x80) == 0x80
  len = integer(buf, 7)
  str = buf.read(len)
  raise CompressionError, 'string too short' unless str.bytesize == len

  str = Huffman.new.decode(Buffer.new(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/compressor.rb', line 480

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