Class: ImageSize::ISOBMFF

Inherits:
Object
  • Object
show all
Defined in:
lib/image_size/isobmff.rb

Overview

:nodoc:

Defined Under Namespace

Classes: Box, FullBox

Constant Summary collapse

S64_OVERFLOW = 
1 << 63

Instance Method Summary collapse

Constructor Details

#initialize(options = {}) ⇒ ISOBMFF

Returns a new instance of ISOBMFF.



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# File 'lib/image_size/isobmff.rb', line 41

def initialize(options = {})
  @full = options.fetch(:full, []).to_set
  @last = options.fetch(:last, []).to_set
  @recurse = options.fetch(:recurse, []).to_set
end

Instance Method Details

#recurse(reader, offset = 0, length = nil, &block) ⇒ Object 



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# File 'lib/image_size/isobmff.rb', line 91

def recurse(reader, offset = 0, length = nil, &block)
  walk(reader, offset, length) do |box|
    yield box

    recurse(reader, box.data_offset, box.data_size, &block) if @recurse.include?(box.type)
  end
end

#walk(reader, offset = 0, length = nil) ⇒ Object 



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# File 'lib/image_size/isobmff.rb', line 47

def walk(reader, offset = 0, length = nil)
  max_offset = length ? offset + length : S64_OVERFLOW
  index = 1
  while offset < max_offset && !['', nil].include?(reader[offset, 4])
    size = reader.unpack1(offset, 4, 'N')
    type = reader.fetch(offset + 4, 4)
    relative_data_offset = 8

    case size
    when 1
      size = reader.unpack1(offset + 8, 8, 'Q>')
      relative_data_offset += 8
      raise FormatError, "Unexpected ISOBMFF xl-box size #{size}" if size < 16
    when 2..7
      raise FormatError, "Reserved ISOBMFF box size #{size}"
    end

    attributes = {
      type: type,
      offset: offset,
      size: size,
      relative_data_offset: relative_data_offset,
      index: index,
    }

    if @full.include?(type)
      version_n_flags = reader.unpack1(offset + relative_data_offset, 4, 'N')
      attributes[:version] = version_n_flags >> 24
      attributes[:flags] = version_n_flags & 0xffffff

      attributes[:relative_data_offset] += 4

      yield FullBox.new(attributes)
    else
      yield Box.new(attributes)
    end

    break if size == 0 || @last.include?(type)

    index += 1
    offset += size
  end
end