flat file atomic read/write in progress

gistfile1.rb

require 'thread'
require 'time'
require 'csv'

class FlatfileDb
  attr_reader :active_data
  def initialize()
    @active_data = Array.new
    @sem = Mutex.new
  end

  def id
    t = Time.new
    return t.to_i, t.nsec.to_i
  end

  def write(table, data)
    raise "no such file" if !File.file? table
    Thread.new {
      @sem.synchronize {
        f = File.open(table, "a") 
        row = ''
        data = [data] if data[0].class != Array # for flat array
        data.each do |d|
          epoch, nanosec  = self.id
          row += CSV.generate_line([epoch, nanosec].concat(d))
        end 
        f.write(row)
        f.close
      }
    }
  end

  def read(table, conditions, limit = 0)
    raise "no such file" if !File.file? table
    Thread.new {
      @sem.synchronize {
        f = File.open(table, "r") 
        f.each do |line|
          @active_data.push(line)
        end
       f.close
      }
    }
  end

end