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Joe Lobraco Snippet ID Download Version Date Posted Author Delete 330 0.1 2008-01-09 05:22 Joe Lobraco

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# A ruby function that can write a basic dbf file. 
# 
# Currently this function only handles text and number fields.
# 
# This function takes a filename, a field structure array, and a record array
# as parameters.
# 
# The field structure array is a list of hashes that contain the following:
#   :field_name - the name of the field (10 characters max)
#   :field_size - the length of the field (for number fields must be long 
#                 enough to hold the string representation of the number)
#   :field_type - 'N' for number fields (max 18 character length)
#                 'C' for string fields (max 254 character length)
#   :decimals   - The number of decimal places for number fields 
#                 (0 for integers and other data types)
# 
#  Example:
#  
#  fields = [
#    {:field_name=>'LOCID', :field_size=>11, :field_type=>'N', :decimals=>0},
#    {:field_name=>'LOCNAME', :field_size=>254, :field_type=>'C', :decimals=>0},
#    {:field_name=>'LOCADDR', :field_size=>100, :field_type=>'C', :decimals=>0},
#    {:field_name=>'LOCCITY', :field_size=>40, :field_type=>'C', :decimals=>0},
#    {:field_name=>'LOCSTATE', :field_size=>2, :field_type=>'C', :decimals=>0},
#    {:field_name=>'LOCZIP', :field_size=>5, :field_type=>'C', :decimals=>0}
#  ]
#  
#  The record structure array is a list of hashes that contain the data, hashed by
#  the field name.
#  
#  Example:
#  
#  records = [
#   {:LOCID=>1, :LOCNAME=>'My Place', :LOCADDR=>'123 Main St.', 
#    :LOCCITY=>'Austin', :LOCSTATE=>'TX', :LOCZIP=>'55555'},
#   {:LOCID=>2, :LOCNAME=>'Your Place', :LOCADDR=>'12 Smith Ave.', 
#    :LOCCITY=>'New York', :LOCSTATE=>'NY', :LOCZIP=>'12345'},
#   {:LOCID=>3, :LOCNAME=>'Their Place', :LOCADDR=>'100 N. High Blvd',
#    :LOCCITY=>'Atlanta', :LOCSTATE=>'GA', :LOCZIP=>'54321'}
#  ]
#  
# ACKNOWLEDGMENTS:
# 
# This code was modeled after the Python DBF Reader and Writer script 
# written by Raymond Hettinger found on the ASPN website: 
# http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/362715
# 
# Additionally, information on the dbf file format that was used in 
# creating this function was found on this website: 
# http://www.clicketyclick.dk/databases/xbase/format/dbf.html
#
def dbf_writer(filename, fields, records)

  File.open(filename, 'w') do |dbf|
    
    now = Time.now()
    numfields = fields.length
    
    # Header Info
    header = Array.new
    header << 3                                         # Version
    header << now.year-1900                             # Year
    header << now.month                                 # Month
    header << now.day                                   # Day
    header << records.length                            # Number of records
    header << (numfields * 32 + 33)                     # The length of the header
    x = 0
    fields.each { |f| x+=f[:field_size] }
    header << x + 1                                     # The length of each record

    hdr = header.pack('CCCCVvvxxxxxxxxxxxxxxxxxxxx')
    
    # Write out the header
    dbf.write(hdr)
    
    fields.each do |f|                                  
      field = Array.new
      field << f[:field_name].ljust(11, "\x00")
      field << f[:field_type][0]
      field << f[:field_size]
      field << f[:decimals]
      fld = field.pack('a11cxxxxCCxxxxxxxxxxxxxx') 
      
      # Write out field descriptor
      dbf.write(fld)
    end
    
    # Write terminator '\r'
    dbf.write("\r")
    
    records.each do |r|
      # Write deletion flag
      dbf.write(' ')
      
      fields.each do |f|
        value = r[f[:field_name].to_sym]

        if f[:field_type] == 'N'
          value = value.to_s.rjust(f[:field_size], ' ')
        else
          value = value.to_s[0,f[:field_size]].ljust(f[:field_size], ' ')
        end
        
        if value.length != f[:field_size]
          raise "Record too long"
        end

        # Write value
        dbf.write(value)
        
      end # fields.each
    end # records.each
    
    # Write end of file '\x1A'
    dbf.write("\x1A")
    
  end # File.open
  
end





		

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