Module: BC3::Helper

Included in:
File, Folder, Snapshot
Defined in:
lib/bc3/helper.rb

Overview

Helper methods to be included to File and Folder.

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.crc32(c) ⇒ Object

Calculate the CRC32 for a string.

Based on www.ruby-forum.com/topic/179452 (with minor ruby 1.9 adaptions).



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# File 'lib/bc3/helper.rb', line 70

def self.crc32(c)
  #Alternative solution:
  #~ require 'zlib'
  #~ return Zlib.crc32(c, 0) 
  
  #Encoding of c should be binary or similar.
  n = c.length  
  r = 0xFFFFFFFF
  c.each_byte do |i|
      r ^= i
      8.times do
          if (r & 1)!=0
              r = (r>>1) ^ 0xEDB88320
          else
              r >>= 1
          end
      end
  end
  r ^ 0xFFFFFFFF
end

Instance Method Details

#fixnum2int16(int) ⇒ Object

Same as Helper#fixnum2int64, but as 2 bytes string.

Raises:

  • (ArgumentError) 


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# File 'lib/bc3/helper.rb', line 129

def fixnum2int16( int )
  bindata = ''.force_encoding('BINARY')
  ('%016b' % int).scan(/(\d{8})/).flatten.reverse.each{|b|
      bindata << b.to_i(2)
  }
  raise ArgumentError unless $~.post_match.empty?
  raise ArgumentError unless bindata.size == 2 #int was too big
  bindata
end

#fixnum2int32(int) ⇒ Object

Same as Helper#fixnum2int64, but as 4 bytes string.

Raises:

  • (ArgumentError) 


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# File 'lib/bc3/helper.rb', line 116

def fixnum2int32( int )
  bindata = ''.force_encoding('BINARY')
  ('%032b' % int).scan(/(\d{8})/).flatten.reverse.each{|b|
      bindata << b.to_i(2)
  }
  raise ArgumentError unless $~.post_match.empty?
  raise ArgumentError unless bindata.size == 4  #int was too big
  bindata
end

#fixnum2int64(int) ⇒ Object

Return a Number (e.g. AD epoch) as a binary string with 8 bytes in little endian order.

With

String#<< (Integer)

the integer is a codepoint, the character is added. AD’s epoch isn’t a codepoint, but a binary data. So we need a little conversion, to get AD’s epoch (Bignum) as an bit sequence.

Raises:

  • (ArgumentError) 


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# File 'lib/bc3/helper.rb', line 101

def fixnum2int64( int )
  bindata = ''.force_encoding('BINARY')
  #Ugly code, but it works ;-)
  #.reverse to get "little endian"
  ('%064b' % int).scan(/(\d{8})/).flatten.reverse.each{|b|
      bindata << b.to_i(2)
  }
  raise ArgumentError unless $~.post_match.empty?
  raise ArgumentError unless bindata.size == 8  #int was too big
  bindata
end

#shortstring2bcss(shortstring) ⇒ Object

Save a shortstring to bcss

ShortString:

Variable length single-byte character string (ANSI or UTF-8).  
Not null terminated.

UTF-8: If set the snapshot was compressed on a system where the default

character encoding is UTF-8 (Linux, OS X). Filenames, paths, and link targets will all be stored as UTF-8. If this isn’t set the paths are stored using the original OS’s ANSI codepage (Windows). In that case any paths may be stored a second time as UTF-8 in extended headers.



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# File 'lib/bc3/helper.rb', line 153

def shortstring2bcss(shortstring)
    bcss = "".force_encoding('BINARY')
    bcss << shortstring.bytesize
    bcss << shortstring.dup.force_encoding('binary')
    bcss
end