Class: EventMachine::AblyHttpRequest::HttpDecoders::GZipHeader

Inherits:
Object
  • Object
show all
Defined in:
lib/em-http/decoders.rb

Overview

Partial implementation of RFC 1952 to extract the deflate stream from a gzip file

Instance Method Summary collapse

Constructor Details

#initialize ⇒ GZipHeader

Returns a new instance of GZipHeader.



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# File 'lib/em-http/decoders.rb', line 97

def initialize
  @state = :begin
  @data = ""
  @pos = 0
end

Instance Method Details

#eof? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/em-http/decoders.rb', line 124

def eof?
  @pos >= @data.size
end

#extract_stream(compressed) ⇒ Object 



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# File 'lib/em-http/decoders.rb', line 128

def extract_stream(compressed)
  @data << compressed

  while !eof? && !finished?
    buffer = ""

    case @state
    when :begin
      break if !read(10, buffer)

      if buffer.getbyte(0) != 0x1f || buffer.getbyte(1) != 0x8b
        raise DecoderError.new("magic header not found")
      end

      if buffer.getbyte(2) != 0x08
        raise DecoderError.new("unknown compression method")
      end

      @flags = buffer.getbyte(3)
      if (@flags & 0xe0).nonzero?
        raise DecoderError.new("unknown header flags set")
      end

      # We don't care about these values, I'm leaving the code for reference
      # @time = buffer[4..7].unpack("V")[0] # little-endian uint32
      # @extra_flags = buffer.getbyte(8)
      # @os = buffer.getbyte(9)

      @state = :extra_length

    when :extra_length
      if (@flags & 0x04).nonzero?
        break if !read(2, buffer)
        @extra_length = buffer.unpack("v")[0] # little-endian uint16
        @state = :extra
      else
        @state = :extra
      end

    when :extra
      if (@flags & 0x04).nonzero?
        break if read(@extra_length, buffer)
        @state = :name
      else
        @state = :name
      end

    when :name
      if (@flags & 0x08).nonzero?
        while !(buffer = readbyte).nil?
          if buffer == 0
            @state = :comment
            break
          end
        end
      else
        @state = :comment
      end

    when :comment
      if (@flags & 0x10).nonzero?
        while !(buffer = readbyte).nil?
          if buffer == 0
            @state = :hcrc
            break
          end
        end
      else
        @state = :hcrc
      end

    when :hcrc
      if (@flags & 0x02).nonzero?
        break if !read(2, buffer)
        @state = :finish
      else
        @state = :finish
      end
    end
  end

  if finished?
    compressed[(@pos - (@data.length - compressed.length))..-1]
  else
    ""
  end
end

#finished? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/em-http/decoders.rb', line 103

def finished?
  @state == :finish
end

#read(n, buffer) ⇒ Object 



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# File 'lib/em-http/decoders.rb', line 107

def read(n, buffer)
  if (@pos + n) <= @data.size
    buffer << @data[@pos..(@pos + n - 1)]
    @pos += n
    return true
  else
    return false
  end
end

#readbyte ⇒ Object 



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# File 'lib/em-http/decoders.rb', line 117

def readbyte
  if (@pos + 1) <= @data.size
    @pos += 1
    @data.getbyte(@pos - 1)
  end
end