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--------------------------------------------------------------
-- Taler amounts and helper functions
-------------------------------------------------------------
CREATE OR REPLACE FUNCTION amount_normalize(
IN amount taler_amount
,OUT normalized taler_amount
)
LANGUAGE plpgsql
AS $$
BEGIN
normalized.val = amount.val + amount.frac / 100000000;
normalized.frac = amount.frac % 100000000;
END $$;
COMMENT ON FUNCTION amount_normalize
IS 'Returns the normalized amount by adding to the .val the value of (.frac / 100000000) and removing the modulus 100000000 from .frac.';
CREATE OR REPLACE FUNCTION amount_add(
IN a taler_amount
,IN b taler_amount
,OUT sum taler_amount
)
LANGUAGE plpgsql
AS $$
BEGIN
sum = (a.val + b.val, a.frac + b.frac);
CALL amount_normalize(sum ,sum);
IF (sum.val > (1<<52))
THEN
RAISE EXCEPTION 'addition overflow';
END IF;
END $$;
COMMENT ON FUNCTION amount_add
IS 'Returns the normalized sum of two amounts. It raises an exception when the resulting .val is larger than 2^52';
CREATE OR REPLACE FUNCTION amount_left_minus_right(
IN l taler_amount
,IN r taler_amount
,OUT diff taler_amount
,OUT ok BOOLEAN
)
LANGUAGE plpgsql
AS $$
BEGIN
IF (l.val > r.val)
THEN
ok = TRUE;
IF (l.frac >= r.frac)
THEN
diff.val = l.val - r.val;
diff.frac = l.frac - r.frac;
ELSE
diff.val = l.val - r.val - 1;
diff.frac = l.frac + 100000000 - r.frac;
END IF;
ELSE
IF (l.val = r.val) AND (l.frac >= r.frac)
THEN
diff.val = 0;
diff.frac = l.frac - r.frac;
ok = TRUE;
ELSE
diff = (-1, -1);
ok = FALSE;
END IF;
END IF;
RETURN;
END $$;
COMMENT ON FUNCTION amount_left_minus_right
IS 'Subtracts the right amount from the left and returns the difference and TRUE, if the left amount is larger than the right, or an invalid amount and FALSE otherwise.';
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