Class: Marc2LinkedData::Utils

Inherits:
Object
  • Object
show all
Defined in:
lib/marc2linkeddata/utils.rb

Class Method Summary collapse

Class Method Details

.marc_type_count(marc_filename) ⇒ Object

Count all the records in the MARC file, by parsing the record leader, see www.loc.gov/marc/bibliographic/bdleader.html www.loc.gov/marc/authority/adleader.html



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# File 'lib/marc2linkeddata/utils.rb', line 23

def self.marc_type_count(marc_filename)
  # 06 - Type of record
  # a - Language material
  # c - Notated music
  # d - Manuscript notated music
  # e - Cartographic material
  # f - Manuscript cartographic material
  # g - Projected medium
  # i - Nonmusical sound recording
  # z - Authority data
  record_types = {
      :a_language_material => 0,
      :c_notated_music => 0,
      :d_manuscript_notated_music => 0,
      :e_cartographic_material => 0,
      :f_manuscript_cartographic_material => 0,
      :g_projected_medium => 0,
      :i_nonmusical_sound_recording => 0,
      :z_authority_data => 0
  }
  marc_file = File.open(marc_filename,'r')
  until marc_file.eof?
    begin
      leader = Marc2LinkedData::Utils.parse_leader(marc_file)
      marc_file.seek(leader[:length], IO::SEEK_CUR)
      case leader[:type]
        when 'a'
          record_types[:a_language_material] += 1
        when 'c'
          record_types[:c_notated_music] += 1
        when 'd'
          record_types[:d_manuscript_notated_music] += 1
        when 'e'
          record_types[:e_cartographic_material] += 1
        when 'f'
          record_types[:f_manuscript_cartographic_material] += 1
        when 'g'
          record_types[:g_projected_medium] += 1
        when 'i'
          record_types[:i_nonmusical_sound_recording] += 1
        when 'z'
          record_types[:z_authority_data] += 1
      end
    rescue => e
      Marc2LinkedData::Utils.stack_trace(e, leader)
      binding.pry if CONFIG.debug
    end
  end
  marc_file.close
  record_types
end

.parse_leader(file_handle, leader_bytes = 24) ⇒ Object 



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# File 'lib/marc2linkeddata/utils.rb', line 75

def self.parse_leader(file_handle, leader_bytes=24)
  # example:
  #record.leader
  #=> "00774cz  a2200253n  4500"
  # 00-04: '00774' - record length
  # 05:    'c' - corrected or revised
  # 06:    'z' - always 'z' for authority records
  # 09:    'a' - UCS/Unicode
  # 12-16: '00253' - base address of data, Length of Leader and Directory
  # 17:    'n' - Complete authority record
  # leader_status_codes = {
  #     'a' => 'Increase in encoding level',
  #     'c' => 'Corrected or revised',
  #     'd' => 'Deleted',
  #     'n' => 'New',
  #     'o' => 'Obsolete',
  #     's' => 'Deleted; heading split into two or more headings',
  #     'x' => 'Deleted; heading replaced by another heading'
  # }
  leader = file_handle.read(leader_bytes)
  file_handle.seek(-1 * leader_bytes, IO::SEEK_CUR)
  {
      :length => leader[0..4].to_i,
      :status => leader[5],  # leader_status_codes[ record.leader[5] ]
      :type => leader[6],    # always 'z' for authority records
      :encoding => leader[9],  # translate letter code into ruby encoding string
      :data_address => leader[12..16].to_i,
      :complete => leader[17].include?('n')
  }
end

.stack_trace(e, record = nil) ⇒ Object 



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# File 'lib/marc2linkeddata/utils.rb', line 9

def self.stack_trace(e, record=nil)
  $stderr.write "\n"
  $stderr.write "ERROR\n"
  $stderr.write e.message
  $stderr.write e.backtrace
  $stderr.write "\n"
  $stderr.write record.to_s
  $stderr.write "\n"
end