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.

Examples:

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

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.



472
473
474
 
# File 'lib/http/2/compressor.rb', line 472

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], …]



555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
 
# File 'lib/http/2/compressor.rb', line 555

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
      fail 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



520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
 
# File 'lib/http/2/compressor.rb', line 520

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

  fail CompressionError unless header[:type]

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

  case header[:type]
  when :indexed
    fail 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) 


487
488
489
490
491
492
493
494
495
496
497
498
499
500
 
# File 'lib/http/2/compressor.rb', line 487

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

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

    break if (byte & 128).zero?
  end if (i == limit)

  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



507
508
509
510
511
512
513
514
 
# File 'lib/http/2/compressor.rb', line 507

def string(buf)
  huffman = (buf.readbyte(0) & 0x80) == 0x80
  len = integer(buf, 7)
  str = buf.read(len)
  fail 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



478
479
480
 
# File 'lib/http/2/compressor.rb', line 478

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