simple_multithreaded_example

files = [{:name => f1}, {:name => f2}, {:name => f3}]
index = 0

scanner = Thread.new do
   files.each do |f|
      f[:sha1] = sha1(f[:name])
      index += 1
   end
end

updater = Thread.new do
  local_index = 0
  while (local_index < files.size - 1) 
     if (local_index < index) 
        update_metadata(files[local_index])
     else
        sleep(1)
     end
  end
end

scanner.join
updater.join

simple_multithreaded_example_with_locks

files = [{:name => f1}, {:name => f2}, {:name => f3}]
index = 0
mutex = Mutex.new

scanner = Thread.new do
   files.each do |f|
     sha1 = sha1(f[:name])
     mutex.synchronize {
       f[:sha1] = sha1
       index += 1
     }
   end
end

updater = Thread.new do
  local_index = 0
  while (local_index < files.size - 1) 
     if (local_index < mutex.synchronize {index} ) 
        update_metadata(files[local_index])
     else
        sleep(1)
     end
  end
end

scanner.join
updater.join