From da5b3ba8aeb9d47e4f99cd22847c9b539ff8ee2b Mon Sep 17 00:00:00 2001
From: Florian Dold <florian.dold@gmail.com>
Date: Wed, 15 Jan 2020 15:17:02 +0100
Subject: round amounts based on config, do unit test for rounding

---
 src/util/amount.c      | 13 +++++++++----
 src/util/test_amount.c | 23 +++++++++++++++++++++++
 2 files changed, 32 insertions(+), 4 deletions(-)

(limited to 'src/util')

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;
diff --git a/src/util/test_amount.c b/src/util/test_amount.c
index d9110eaf8..4eeccd7e0 100644
--- a/src/util/test_amount.c
+++ b/src/util/test_amount.c
@@ -234,6 +234,29 @@ main (int argc,
   GNUNET_assert (0 == a2.value);
   GNUNET_assert (1 == a2.fraction);
 
+  /* test rounding #1 */
+
+  GNUNET_assert (GNUNET_OK ==
+                 TALER_string_to_amount ("EUR:4.001",
+                                         &a1));
+  GNUNET_assert (GNUNET_OK ==
+                 TALER_string_to_amount ("EUR:4",
+                                         &a2));
+
+  GNUNET_assert (GNUNET_OK == TALER_amount_round_down (&a1, 2));
+  GNUNET_assert (GNUNET_NO == TALER_amount_round_down (&a1, 2));
+  GNUNET_assert (0 == TALER_amount_cmp (&a1, &a2));
+
+  /* test rounding #2 */
+
+  GNUNET_assert (GNUNET_OK ==
+                 TALER_string_to_amount ("EUR:4.001",
+                                         &a1));
+  GNUNET_assert (GNUNET_OK ==
+                 TALER_string_to_amount ("EUR:4.001",
+                                         &a2));
+  GNUNET_assert (GNUNET_NO == TALER_amount_round_down (&a1, 3));
+  GNUNET_assert (0 == TALER_amount_cmp (&a1, &a2));
 
   return 0;
 }
-- 
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