csv generation, conversion, with utf16le - example

encode_io.rb

require 'iconv' unless "".respond_to?(:encode)
require 'active_support/basic_object'

# = EncodeIo
#
# This is essentially a basic delegation class. The reason it isn't
# using the delegate library from stdlib is that FasterCSV has special
# casing for io classes. In order to keep using this, we need #kind_of?
# and #class to pretend that this is the original class.
#
# This class will wrap any IO like object and pass any writes through
# Iconv before passing them on to the underlying IO.
#
# XXX - #putc may be bugged for big endian encodings.
class WF::EncodeIo < ActiveSupport::BasicObject

  def initialize(io, from = 'UTF-8', to = 'UTF-16le//IGNORE', encode_opts = {})
    @io = io
    @from, @to = from, to
    @encode_opts = encode_opts

    if "".respond_to?(:encode)
      @from = Encoding.find(from) unless from.kind_of?(Encoding)
      unless to.kind_of?(Encoding)
        coding, ignore = to.split('//')
        @encode_opts[:fallback] = lambda { |c| c } if ignore =~ /ignore/i
        @to = Encoding.find(coding)
      end
    end
  end

  conversion_methods = %w[ write syswrite write_nonblock << putc print ]
  conversion_methods.each do |m|
    class_eval <<-RUBY, __FILE__, __LINE__
      def #{m}(*args)
        @io.send __method__, *_convert(*args)
      end
    RUBY
  end

  def puts(*args)
    # The documented IO#puts conventions claim to do this, however, in many
    # cases it's actually "optimized", that is, reimplemented inline in C.
    args.each do |arg|
      line = arg.end_with?($/) ? arg : arg + $/
      print line
    end
    nil
  end

  def method_missing(name, *args, &block)
    @io.send(name, *args, &block)
  end

  private

  if "".respond_to?(:encode)
    def _convert(*args)
      args.map { |a| a.encode(@to, @from, @encode_opts) }
    end
  else
    def _convert(*args)
      args.map { |a| Iconv.conv(@to, @from, a) }
    end
  end
end

class WF::CSV
  UTF16LE_BOM = "\xFF\xFE"

  attr_reader :name, :path

  def initialize name = 'export.csv.zip'
    @name = name
    Tempfile.open(@name) do |io|
      begin
        @path = io.path
        
      ensure
        @path = nil
      end
    end
  end

  def write
    unless @path
      raise ArgumentError,
        "you must write to the CSV from within the block passed to initialize"
    end

    Zip::ZipOutputStream.open(@path) do |zip|
      zip.put_next_entry(@name)
      zip.print(UTF16LE_BOM)
      csv = FasterCSV.new(zip, :col_sep => "\t", :row_sep => "\n")
      yield csv
    end
  end
end

# Example usage:

WF::CSV.new("#{CGI.escape page_name}.csv.zip") do |zip|
  zip.data do |csv|
    csv << %w[header1 header2 header3]
    Model.scope.find_each do |model|
      csv << model.attributes.values_at(*%w[attr1 attr2 attr3])
    end
  end

  Mailer.send_csv_email user_email, :attachment => zip.path
end