Class: ExcelDocument

Inherits:

Object

• Object
• ExcelDocument

Defined in:

lib/surpass/document.rb

Overview

This implementation writes only ‘Root Entry’, ‘Workbook’ streams and 2 empty streams for aligning directory stream on sector boundary

LAYOUT: 0 header 76 MSAT (1st part: 109 SID) 512 workbook stream … additional MSAT sectors if streams’ size > about 7 Mb == (109*512 * 128) … SAT … directory stream

NOTE: this layout is “ad hoc”. It can be more general. RTFM

Constant Summary

SECTOR_SIZE =

0x0200

MIN_LIMIT =

0x1000

SID_FREE_SECTOR =

-1

SID_END_OF_CHAIN =

-2

SID_USED_BY_SAT =

-3

SID_USED_BY_MSAT =

-4

Instance Method Summary

• #build_directory ⇒ Object
• #build_header ⇒ Object
• #build_sat ⇒ Object
• #data(stream) ⇒ Object
• #initialize ⇒ ExcelDocument constructor

  A new instance of ExcelDocument.

• #pack_directory(name, type, colour, did_left, did_right, did_root, start_sid, stream_sz) ⇒ Object
• #save(file, stream) ⇒ Object

Constructor Details

#initialize ⇒ ExcelDocument

Returns a new instance of ExcelDocument.

# File 'lib/surpass/document.rb', line 194

def initialize
  @book_stream_sect = []
  @dir_stream_sect = []
  
  @packed_sat = ''
  @sat_sect = []
  
  @packed_msat_1st = ''
  @packed_msat_2nd = ''
  @msat_sect_2nd = []
  @header = ''
end

Instance Method Details

#build_directory ⇒ Object

# File 'lib/surpass/document.rb', line 207

def build_directory
  @dir_stream = ''
  
  name = 'Root Entry'
  type = 0x05 # root storage
  colour = 0x01 # black
  did_left  = -1
  did_right = -1
  did_root  = 1
  start_sid = -2
  stream_sz = 0
  @dir_stream += pack_directory(name, type, colour, did_left, did_right, did_root, start_sid, stream_sz)

  name = 'Workbook'
  type = 0x02 # user stream
  colour = 0x01 # black
  did_left  = -1
  did_right = -1
  did_root  = -1
  start_sid = 0
  stream_sz = @book_stream_len
  @dir_stream += pack_directory(name, type, colour, did_left, did_right, did_root, start_sid, stream_sz)
  # padding
  name      = ''
  type      = 0x00 # empty
  colour    = 0x01 # black
  did_left  = -1
  did_right = -1
  did_root  = -1
  start_sid = -2
  stream_sz = 0
  @dir_stream += pack_directory(name, type, colour, did_left, did_right, did_root, start_sid, stream_sz) * 2
end

#build_header ⇒ Object

# File 'lib/surpass/document.rb', line 335

def build_header
   doc_magic                    = "\320\317\021\340\241\261\032\341"
   file_uid                     =  "\000" * 16
   rev_num                      = ">\000"
   ver_num                      = "\003\000"
   byte_order                   = "\376\377"
   log_sect_size                = [9].pack('v')
   log_short_sect_size          = [6].pack('v')
   not_used0                    = "\000"*10
   total_sat_sectors            = [@sat_sect.length].pack('V')
   dir_start_sid                = [@dir_stream_sect[0]].pack('V')
   not_used1                    = "\000"*4        
   min_stream_size              = [0x1000].pack('V')
   ssat_start_sid               = [-2].pack('V')
   total_ssat_sectors           = [0].pack('V')
   
   if @msat_sect_2nd.length == 0
     msat_start_sid = [-2].pack('V')
   else
     msat_start_sid = [@msat_sect_2nd[0]].pack('V')
   end
   
   total_msat_sectors = [@msat_sect_2nd.length].pack('V')
   
   @header = [
       doc_magic,
       file_uid,
       rev_num,
       ver_num,
       byte_order,
       log_sect_size,
       log_short_sect_size,
       not_used0,
       total_sat_sectors,
       dir_start_sid,
       not_used1,
       min_stream_size,
       ssat_start_sid,
       total_ssat_sectors,
       msat_start_sid,
       total_msat_sectors
   ].join
end

#build_sat ⇒ Object

# File 'lib/surpass/document.rb', line 253

def build_sat
  book_sect_count       = @book_stream_len >> 9
  dir_sect_count        = @dir_stream.length >> 9
  total_sect_count      = book_sect_count + dir_sect_count
  sat_sect_count        = 0
  msat_sect_count       = 0
  sat_sect_count_limit  = 109
  
  while (total_sect_count > 128*sat_sect_count) || (sat_sect_count > sat_sect_count_limit) do
    sat_sect_count += 1
    total_sect_count += 1
    if sat_sect_count > sat_sect_count_limit
      msat_sect_count += 1
      total_sect_count += 1
      sat_sect_count_limit += 127
    end
  end
  
  # initialize the sat array to be filled with the "empty" character specified by SID_FREE_SECTOR
  sat = [SID_FREE_SECTOR]*128*sat_sect_count
  
  sect = 0
  while sect < book_sect_count - 1 do
    @book_stream_sect << sect
    sat[sect] = sect + 1
    sect += 1
  end
  @book_stream_sect << sect
  sat[sect] = SID_END_OF_CHAIN
  sect += 1
  
  while sect < book_sect_count + msat_sect_count do
    @msat_sect_2nd << sect
    sat[sect] = SID_USED_BY_MSAT
    sect += 1
  end
  
  while sect < book_sect_count + msat_sect_count + sat_sect_count do
    @sat_sect << sect
    sat[sect] = SID_USED_BY_SAT
    sect += 1
  end
  
  while sect < book_sect_count + msat_sect_count + sat_sect_count + dir_sect_count - 1 do
    @dir_stream_sect << sect
    sat[sect] = sect + 1
    sect += 1
  end
  
  @dir_stream_sect << sect
  sat[sect] = SID_END_OF_CHAIN
  sect += 1
  
  @packed_sat = sat.pack('V*')
  
  msat_1st = []
  109.times do |i|
    msat_1st[i] = @sat_sect[i] || SID_FREE_SECTOR
  end
  @packed_msat_1st = msat_1st.pack('V*')
  
  msat_2nd = [SID_FREE_SECTOR] * 128 * msat_sect_count
  msat_2nd[-1] = SID_END_OF_CHAIN if msat_sect_count > 0
  
  i = 109
  msat_sect = 0
  sid_num = 0
  
  while i < sat_sect_count do
    if (sid_num + 1) % 128 == 0
      msat_sect += 1
      msat_2nd[sid_num] = @msat_sect_2nd[msat_sect] if msat_sect < @msat_sect_2nd.length
    else
      msat_2nd[sid_num] = @sat_sect[i]
      i += 1
    end
    sid_num += 1
  end
  
  @packed_msat_2nd = msat_2nd.pack('V*')
end

#data(stream) ⇒ Object

# File 'lib/surpass/document.rb', line 379

def data(stream)
  distance_to_end_of_next_sector_boundary = 0x1000 - (stream.length % 0x1000)
  @book_stream_len = stream.length + distance_to_end_of_next_sector_boundary
  padding = "\000" * distance_to_end_of_next_sector_boundary

  build_directory
  build_sat
  build_header
  
  s = StringIO.new
  s.write(@header)
  s.write(@packed_msat_1st)
  s.write(stream)
  s.write(padding)
  s.write(@packed_msat_2nd)
  s.write(@packed_sat)
  s.write(@dir_stream)
  s.rewind
  s
end

#pack_directory(name, type, colour, did_left, did_right, did_root, start_sid, stream_sz) ⇒ Object

# File 'lib/surpass/document.rb', line 241

def pack_directory(name, type, colour, did_left, did_right, did_root, start_sid, stream_sz)
  encoded_name = ''
  0.upto(name.length) do |i|
    encoded_name << name[i, 1] + "\000" 
  end
  encoded_name << "\000"
  name_sz = encoded_name.length

  args = [encoded_name, name_sz, type, colour, did_left, did_right, did_root, 0, 0, 0, 0, 0, 0, 0, 0, 0, start_sid, stream_sz, 0]
  args.pack('a64 v C2 V3 V9 V V2')
end

#save(file, stream) ⇒ Object

# File 'lib/surpass/document.rb', line 400

def save(file, stream)
  we_own_it = !file.respond_to?(:write)
  file = File.open(file, 'wb') if we_own_it
  file.write data(stream).read
  file.close if we_own_it
end