Class: Pdfrb::Font::CFF::Dict

Inherits:
Object
  • Object
show all
Defined in:
lib/pdfrb/font/cff/dict.rb

Overview

DICT data parsing (TN5176 s4): a sequence of operands (from the b0 byte ranges) followed by an operator byte.

Used both to READ the Top DICT (CharStrings offset, Private [size offset], charset) and to locate operator positions so a subsetter can patch offsets in place.

Defined Under Namespace

Classes: Entry

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(raw, entries) ⇒ Dict

Returns a new instance of Dict.



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# File 'lib/pdfrb/font/cff/dict.rb', line 87

def initialize(raw, entries)
  @raw = raw
  @entries = entries
end

Instance Attribute Details

#entries ⇒ Object (readonly)

Returns the value of attribute entries.



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# File 'lib/pdfrb/font/cff/dict.rb', line 22

def entries
  @entries
end

#raw ⇒ Object (readonly)

Returns the value of attribute raw.



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# File 'lib/pdfrb/font/cff/dict.rb', line 22

def raw
  @raw
end

Class Method Details

.parse(data) ⇒ Object 



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# File 'lib/pdfrb/font/cff/dict.rb', line 24

def self.parse(data)
  entries = []
  operands = []
  pos = 0
  entry_start = 0
  while pos < data.bytesize
    b0 = data.getbyte(pos)
    case b0
    when 28 then operands << data.byteslice(pos + 1, 2).unpack1("n")
                 pos += 3
    when 29 then operands << data.byteslice(pos + 1, 4).unpack1("N")
                 pos += 5
    when 30
      real, pos = parse_real(data, pos + 1)
      operands << real
    when 32..246
      operands << (b0 - 139)
      pos += 1
    when 247..250
      operands << (((b0 - 247) * 256) + data.getbyte(pos + 1) + 108)
      pos += 2
    when 251..254
      operands << ((-(b0 - 251) * 256) - data.getbyte(pos + 1) - 108)
      pos += 2
    else
      # Operator (0..21, with 12 x for two-byte ops).
      if b0 == 12
        op = [12, data.getbyte(pos + 1)]
        pos += 2
      else
        op = b0
        pos += 1
      end
      entries << Entry.new(op, operands, entry_start, pos)
      operands = []
      entry_start = pos
    end
  end
  new(data, entries)
end

.parse_real(data, pos) ⇒ Object

Real operand (b0 30): nibble-encoded decimal terminated by 0xF. Returns [Float, next_pos].



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# File 'lib/pdfrb/font/cff/dict.rb', line 70

def self.parse_real(data, pos)
  buf = +""
  while pos < data.bytesize
    nibble_pair = data.getbyte(pos)
    pos += 1
    hi = nibble_pair >> 4
    lo = nibble_pair & 0xF
    break if hi == 0xF

    buf << NIBBLE_CHARS[hi]
    break if lo == 0xF

    buf << NIBBLE_CHARS[lo]
  end
  [buf.to_f, pos]
end

Instance Method Details

#charset_offset ⇒ Object

Top DICT helpers (operator numbers per TN5176 Table 6):

15 charset, 17 CharStrings, 18 Private [size offset].


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# File 'lib/pdfrb/font/cff/dict.rb', line 100

def charset_offset
  entry_for(15)&.int_operand
end

#charstrings_offset ⇒ Object 



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# File 'lib/pdfrb/font/cff/dict.rb', line 104

def charstrings_offset
  entry_for(17)&.int_operand
end

#entry_for(operator) ⇒ Object

Entry for a one-byte Integer operator or a two-byte [12, x] operator.



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# File 'lib/pdfrb/font/cff/dict.rb', line 94

def entry_for(operator)
  entries.find { |e| e.operator == operator }
end

#private_size_offset ⇒ Object

Returns [size, offset].



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# File 'lib/pdfrb/font/cff/dict.rb', line 109

def private_size_offset
  e = entry_for(18)
  return nil unless e

  [e.int_operand(0), e.int_operand(1)]
end