Module: Pdfrb::Source::XrefStreamReader

Defined in:
lib/pdfrb/source/xref_stream_reader.rb

Overview

Reads an XRef stream (s7.5.8, PDF 1.5+). The stream's decoded bytes contain the xref entries; /W gives the byte widths of the three fields (type, oid-or-next-free, gen-or-index).

Class Method Summary collapse

Class Method Details

.read(stream_object, document) ⇒ Object

Raises:



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# File 'lib/pdfrb/source/xref_stream_reader.rb', line 11

def read(stream_object, document)
  dict = stream_object
  decoded = stream_object.decoded_stream
  w = dict[:W].to_a
  raise Pdfrb::ParseError, "XRef stream missing /W" if w.nil? || w.length != 3

  index = (dict[:Index] || [0, dict[:Size]]).to_a
  section = XrefSection.new(size: dict[:Size] || 0)
  pos = 0
  bytes = decoded.bytes
  (index.length / 2).times do |seg|
    start_oid = index[seg * 2]
    count = index[seg * 2 + 1]
    count.times do |i|
      type = read_field(bytes, pos, w[0]) || 1
      pos += w[0]
      f2 = read_field(bytes, pos, w[1])
      pos += w[1]
      f3 = read_field(bytes, pos, w[2])
      pos += w[2]
      oid = start_oid + i
      case type
      when 0 then section.add_free(oid, f3 || 0, f2 || 0)
      when 1 then section.add_in_use(oid, f3 || 0, f2 || 0)
      when 2 then section.add_compressed(oid, f2 || 0, f3 || 0)
      end
    end
  end
  section
end