round amounts based on config, do unit test for rounding

1 files changed, 9 insertions, 4 deletions

diff --git a/src/util/amount.c b/src/util/amount.c
index edb9dc060..48f5d9891 100644
--- a/src/util/amount.c
+++ b/src/util/amount.c
@@ -673,19 +673,24 @@ TALER_amount_divide (struct TALER_Amount *result,
 
 
 /**
- * Round the amount to something that can be
- * transferred on the wire.
+ * Round the amount to something that can be transferred on the wire.
  *
  * @param[in,out] amount amount to round down
+ * @param max_fractional_digits number of fractional digits to round down to
  * @return #GNUNET_OK on success, #GNUNET_NO if rounding was unnecessary,
  *         #GNUNET_SYSERR if the amount or currency was invalid
  */
 int
-TALER_amount_round (struct TALER_Amount *amount)
+TALER_amount_round_down (struct TALER_Amount *amount,
+                         uint8_t max_fractional_digits)
 {
   uint32_t delta;
+  uint32_t divisor = 1;
 
-  delta = amount->fraction % (TALER_AMOUNT_FRAC_BASE / 100);
+  for (unsigned int i = 0; i < max_fractional_digits; i++)
+    divisor *= 10;
+
+  delta = amount->fraction % (TALER_AMOUNT_FRAC_BASE / divisor);
   if (0 == delta)
     return GNUNET_NO;
   amount->fraction -= delta;