Class: HexaPDF::Font::TrueType::Table

Inherits:
Object
  • Object
show all
Defined in:
lib/hexapdf/font/true_type/table.rb,
lib/hexapdf/font/true_type/table/os2.rb,
lib/hexapdf/font/true_type/table/cmap.rb,
lib/hexapdf/font/true_type/table/glyf.rb,
lib/hexapdf/font/true_type/table/head.rb,
lib/hexapdf/font/true_type/table/hhea.rb,
lib/hexapdf/font/true_type/table/hmtx.rb,
lib/hexapdf/font/true_type/table/kern.rb,
lib/hexapdf/font/true_type/table/loca.rb,
lib/hexapdf/font/true_type/table/maxp.rb,
lib/hexapdf/font/true_type/table/name.rb,
lib/hexapdf/font/true_type/table/post.rb,
lib/hexapdf/font/true_type/table/directory.rb,
lib/hexapdf/font/true_type/table/cmap_subtable.rb

Overview

Implementation of a generic table inside a sfnt-formatted font file.

See: developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6.html

Direct Known Subclasses

Cmap, Directory, Glyf, Head, Hhea, Hmtx, Kern, Loca, Maxp, Name, OS2, Post

Defined Under Namespace

Classes: Cmap, CmapSubtable, Directory, Glyf, Head, Hhea, Hmtx, Kern, Loca, Maxp, Name, OS2, Post

Constant Summary collapse

TIME_EPOCH =

The time Epoch used in sfnt-formatted font files.

Time.new(1904, 1, 1)

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(font, entry) ⇒ Table

Creates a new Table object for the given font and initializes it by reading the data from the font’s associated IO stream

See: #parse_table



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# File 'lib/hexapdf/font/true_type/table.rb', line 81

def initialize(font, entry)
  @font = font
  @directory_entry = entry
  load_from_io
end

Instance Attribute Details

#font ⇒ Object (readonly)

The TrueType font object associated with this table.



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# File 'lib/hexapdf/font/true_type/table.rb', line 75

def font
  @font
end

Class Method Details

.calculate_checksum(data) ⇒ Object

Calculates the checksum for the given data.



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# File 'lib/hexapdf/font/true_type/table.rb', line 65

def self.calculate_checksum(data)
  checksum = 0
  if (remainder_length = data.length % 4) != 0
    checksum = (data[-remainder_length, remainder_length] << "\0" * (4 - remainder_length)).
      unpack1('N')
  end
  checksum + data.unpack('N*').inject(0) {|sum, long| sum + long } % 2**32
end

Instance Method Details

#checksum_valid? ⇒ Boolean

Returns true if the checksum stored in the directory entry of the table matches the tables data.

Returns:

  • (Boolean) 


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# File 'lib/hexapdf/font/true_type/table.rb', line 96

def checksum_valid?
  directory_entry.checksum == self.class.calculate_checksum(raw_data)
end

#directory_entry ⇒ Object

Returns the directory entry for this table.

See: Directory



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# File 'lib/hexapdf/font/true_type/table.rb', line 90

def directory_entry
  @directory_entry
end

#raw_data ⇒ Object

Returns the raw table data.



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# File 'lib/hexapdf/font/true_type/table.rb', line 101

def raw_data
  with_io_pos(directory_entry.offset) { io.read(directory_entry.length) }
end