Class: SharedStringTable

Inherits:
Object
  • Object
show all
Defined in:
lib/surpass/biff_record.rb

Constant Summary collapse

SST_ID = 
0x00FC

Instance Method Summary collapse

Constructor Details

#initialize ⇒ SharedStringTable

Returns a new instance of SharedStringTable.



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# File 'lib/surpass/biff_record.rb', line 4

def initialize
  @sst_record = nil
  @continues = []
  @current_piece = [0,0].pack('V2')

  @str_indexes = {} # TODO replace with array? or is hash more efficient?
  @add_calls = 0
end

Instance Method Details

#add_str(s) ⇒ Object 



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# File 'lib/surpass/biff_record.rb', line 13

def add_str(s)
  @add_calls += 1
  index = @str_indexes[s]
  if index.nil?
    # This is a new string for the SST.
    position = @str_indexes.length
    @str_indexes[s] = position
    index = position
    add_to_sst(s)
  end
  index
end

#add_to_sst(s) ⇒ Object 



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# File 'lib/surpass/biff_record.rb', line 38

def add_to_sst(s)
  u_str = mock_unicode_string(s)
  raise "very long string" if u_str.length > 0xFFFF
  save_atom(u_str[0...4])
  save_splitted(u_str[4..-1], false)
end

#new_piece ⇒ Object

Store the @current_piece in @continues and initialize a new @current_piece



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# File 'lib/surpass/biff_record.rb', line 46

def new_piece
  if @sst_record.nil?
    # We get here when we first run out of space, or if that never happens then we end
    # up here when everything is finished and we call to_biff for the first time.
    @sst_record = @current_piece
  else
    @continues << [BiffRecord::CONTINUE_RECORD_ID, @current_piece.length].pack('v2') + @current_piece
  end
  @current_piece = ''
end

#save_atom(atom) ⇒ Object 



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# File 'lib/surpass/biff_record.rb', line 57

def save_atom(atom)
  free_space = 0x2020 - @current_piece.length
  new_piece if free_space < atom.length
  @current_piece += atom
end

#save_splitted(s, is_unicode_str) ⇒ Object 



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# File 'lib/surpass/biff_record.rb', line 63

def save_splitted(s, is_unicode_str)
  i = 0
  while i < s.length do
    free_space = 0x2020 - @current_piece.length
    tail_length = s.length - i
    need_more_space = free_space < tail_length
    
    if !need_more_space
      atom_length = tail_length
    else
      if is_unicode_str
        atom_length = free_space & 0xFFFE
      else
        atom_length = free_space
      end
    end
    @current_piece += s[i...(i+atom_length)]
    
    if need_more_space
      new_piece
      if is_unicode_str
        @current_piece += "\001"
      else
        @current_piece += "\000"
      end
    end
    
    i += atom_length
  end
end

#str_index(s) ⇒ Object 



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# File 'lib/surpass/biff_record.rb', line 26

def str_index(s)
  @str_indexes[s]
end

#to_biff ⇒ Object 



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# File 'lib/surpass/biff_record.rb', line 30

def to_biff
  new_piece # flush the 'current' piece
  result = [SST_ID, @sst_record.length, @add_calls, @str_indexes.length].pack('v2V2')
  result += @sst_record[8..-1]
  result += @continues.join
  result
end