Class: FilesHunter::Decoders::ICO

Inherits:
BeginPatternDecoder show all
Defined in:
lib/fileshunter/Decoders/ICO.rb

Constant Summary collapse

BEGIN_PATTERN_ICO = 
Regexp.new("\x00\x00[\x01\x02]\x00.....\x00", nil, 'n')
ALLOWED_BPP_VALUES = 
[ 0, 1, 4, 8, 16, 24, 32 ]

Instance Method Summary collapse

Methods inherited from BeginPatternDecoder

#find_segments

Methods inherited from FilesHunter::Decoder

#segments_found, #setup

Instance Method Details

#decode(offset) ⇒ Object 



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# File 'lib/fileshunter/Decoders/ICO.rb', line 15

def decode(offset)
  ending_offset = nil

  extension = ((@data[offset+2] == "\x01") ? :ico : :cur)
  nbr_images = BinData::Uint16le.read(@data[offset+4..offset+5])
  invalid_data("@#{offset} - Number of images is 0") if (nbr_images == 0)
  cursor = offset + 6
  # Read all image headers
  images = []
  nbr_images.times do |idx_image|
    #image_width = @data[cursor].ord
    #image_height = @data[cursor+1].ord
    nbr_colors = @data[cursor+2].ord
    invalid_data("@#{cursor} - Invalid ICONDIRENTRY header") if (@data[cursor+3].ord != 0)
    color_planes = BinData::Uint16le.read(@data[cursor+4..cursor+5])
    invalid_data("@#{cursor} - Invalid color planes") if ((extension == :ico) and (color_planes > 1))
    bpp = BinData::Uint16le.read(@data[cursor+6..cursor+7])
    invalid_data("@#{cursor} - Invalid bpp value") if ((extension == :ico) and (!ALLOWED_BPP_VALUES.include?(bpp)))
    invalid_data("@#{cursor} - Invalid number of colors") if ((extension == :ico) and (bpp >= 8) and (nbr_colors != 0))
    image_size = BinData::Uint32le.read(@data[cursor+8..cursor+11])
    invalid_data("@#{cursor} - Invalid image size") if (image_size == 0)
    image_offset = BinData::Uint32le.read(@data[cursor+12..cursor+15])
    images << [ image_offset, image_size ]
    cursor += 16
  end
  progress(cursor)
  # Make sure images are not overlapping
  next_offset_min = cursor-offset
  images.sort.each do |image_offset, image_size|
    invalid_data("@#{cursor} - Invalid image offset: #{image_offset} could not be before #{next_offset_min} as it belongs to another image") if (image_offset < next_offset_min)
    next_offset_min += image_size
  end
  # OK now we consider we might have a valid file
  log_debug "@#{cursor} - #{extension.to_s} file with #{nbr_images} images."
  found_relevant_data(extension)
  metadata(
    :nbr_images => nbr_images
  )
  cursor = offset + next_offset_min
  progress(cursor)
  ending_offset = cursor
  # # Decode each image
  # images.each do |image_offset, image_size|
  #   invalid_data("@#{cursor} - Image offset (#{image_offset}) should be #{cursor-offset}") if (cursor-offset != image_offset)
  #   cursor += image_size
  #   progress(cursor)
  # end
  # ending_offset = cursor

  return ending_offset
end

#get_begin_pattern ⇒ Object 



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# File 'lib/fileshunter/Decoders/ICO.rb', line 11

def get_begin_pattern
  return BEGIN_PATTERN_ICO, { :offset_inc => 3, :max_regexp_size => 10 }
end