[viff-devel] How to structure code with callbacks

[Tord Ingolf Reistad]

Hello,

I have a problem with how to structure codes with much callback in VIFF. 
I want to do some stuff with shares, reveal some values, do more 
calculations with shares, reveal more values, and so on.

For illustration purposes, lets say I have a bitwise secret shared value 
r (r and r_as_bits), and I want to compute c = x + r. Then reveal c and 
print it and reveal c. But this is only done if bits of r are not all zero.

Below is the psudocode and the real code. The real code does not work, 
because it will return the last result only if the reactor is not shut 
down prematurely. So my question is how do I get a working program that 
looks more like my psaudocode?


psaudocode:
--------------------------------------
def protocol(r_as_bits, mask, r, x):
	test = test_not_all_zero(r_as_bits, mask)
	if test == True
		c = r + x
		c = open(c)
		print c
	else
		print "False"

def test_not_all_zero(r_as_bits, mask)
	#reveal (sum(bits) - number_of_bits)*mask
	temp = sum(r_as_bits[:]) - len(r_as_bits)) * mask
	temp = open(temp)
	if temp == 0
		return False
	return True
-------------------------------------

real code:    def protocol_part_1(self, r_as_bits, r, mask, x):
	test = self.test_not_all_zero(r_as_bits, mask)
	self.r = r
	self.x = x
	return test.addCallback(self.protocol_part_2)

     def protocol_part_2(self, test):
         if test:
             c = self.r + self.x
             c_open = self.runtime.open(c)
             result = gather_shares([c_open])
             callback_result = result.addCallback(self.print_answer)
             return callback_result
         else:
             print "No value, False"
             return False

     def print_answer(self, value):
         print "Result ", value
         return True


     def test_not_all_zero(self, r_as_bits, mask):
	#reveal (sum(bits))*mask
	temp = sum(r_as_bits[:]) * mask
	temp_open = self.runtime.open(temp)

	def check_result(check):
             print "Comparing ", check, " to 0"
             if check[0].value == 0:
                 return False
             return True