Module: Gdsii::Read

Included in:

Group

Defined in:

lib/gdsii/mixins.rb

Overview

This module will be extended into all classes descended of Group (i.e. the high-level GDSII access classes). The extension brings a “read” class method (i.e. singleton) into these classes which enables a GDSII file to be read into these data structures using the BNF specification.

Instance Method Summary

• #read(file, parent_records = nil, parent_bnf_item = nil, yield_at = nil) {|group| ... } ⇒ Object

  Accepts a file handle and reads data from that file handle into an object descended of Group.

Instance Method Details

#read(file, parent_records = nil, parent_bnf_item = nil, yield_at = nil) {|group| ... } ⇒ Object

Accepts a file handle and reads data from that file handle into an object descended of Group. The parent_records and parent_bnf_item arguments are for internal use only.

Yields:

• (group)

# File 'lib/gdsii/mixins.rb', line 288

def read(file, parent_records=nil, parent_bnf_item=nil, yield_at=nil)
  # Set BNF index at 0, get the BNF items, create an empty grouping object
  i = 0
  bnf_items = bnf_spec.bnf_items
  group = self.new
#      puts "#{self}"
  
  # Loop through the BNF spec for this grouping...
  while i < bnf_items.length do
    bnf_item = bnf_items[i]

    # see what kind of a BNF item this is - a Class or a record type (Fixnum)
    if bnf_item.key.class == Class
      # return if stop_at_class is set to true (used internally for
      # Library#read_header and Cell#read_header).
      yield group if yield_at == :before_group

      # Determine the class to use
      klass = bnf_item.key
      
      # Read from the class
      if bnf_item.multiple?
        if (rec = klass.read(file, group.records, bnf_item))
          # if a record was returned, then add it
          group.records.add(bnf_item.key, rec)
        else
          # if nil was returned, then we're done with the record; next
          i += 1
        end
      else
        # If the record is singular, then get it from the class and
        # increment the counter
        rec = klass.read(file, group.records, bnf_item)
        group.records.set(bnf_item.key, rec)
        i += 1
      end
    else
      # ELSE, a record type is expected (Fixnum)
      rec = Record.read(file)
#          puts "  --> expect #{Gdsii::grt_name(bnf_item.key)}; rec == #{rec.name}"
      if rec.type == bnf_item.key
        # This record matches the grouping BNF item that was expected, so
        # store the data
        if bnf_item.multiple?
          group.records.add(bnf_item.key, rec)
        else
          group.records.set(bnf_item.key, rec)
          i += 1
        end
      else
        # Record does not match expected record as per BNF.  Check that we
        # have data already set in this record or that the record is
        # optional.
        if group.records.has_data?(bnf_item.key) or bnf_item.optional?
          # Already has data - just move to the next record and reset file
          # pointer
          i += 1
          file.seek(-rec.byte_size, IO::SEEK_CUR)
        elsif (parent_bnf_item and parent_bnf_item.key.class == Class and
               (parent_records.has_data?(parent_bnf_item.key) or
                parent_bnf_item.optional?))
          # OK, in this case, we are descended into a Class and did not
          # match the BNF expected.  Furthermore, the parent calling this
          # grouping either already got the data needed or this was an
          # optional class in the first place.  In either case, we're OK
          # and just need to get out - which is what we do by returning
          # nil.
          file.seek(-rec.byte_size, IO::SEEK_CUR)
          return nil
        else
          # Does not match the expected BNF... fail
          raise "Unexpected record while reading GDSII file starting at file position #{file.pos-rec.byte_size}\n" +
            "This record is in the wrong place according to the GDSII specification (from BNF)\n" +
            "Expected record was #{Gdsii::grt_name(bnf_item.key)}; instead, received:\n" +
            "Record type     = #{Gdsii::grt_name(rec.type)}\n" +
            "Data type       = #{Gdsii::gdt_name(rec.data.type)}\n" +
            "Record length   = #{rec.byte_size}\n"
        end
      end
      
    end
  end
  
  # Return this record grouping
  yield group if yield_at == :group
  group
end