From 0214e426a6cd2c80671bb55257e3358e737f60d3 Mon Sep 17 00:00:00 2001
From: Christian Grothoff <christian@grothoff.org>
Date: Mon, 6 Mar 2017 16:35:30 +0100
Subject: add amount division API and test case

---
 src/include/taler_amount_lib.h  | 14 ++++++++++++++
 src/include/taler_error_codes.h | 15 +++++++++++++++
 src/util/amount.c               | 28 ++++++++++++++++++++++++++++
 src/util/test_amount.c          | 37 +++++++++++++++++++++++++++++++++++++
 4 files changed, 94 insertions(+)

diff --git a/src/include/taler_amount_lib.h b/src/include/taler_amount_lib.h
index 5a59c10ce..555894f4b 100644
--- a/src/include/taler_amount_lib.h
+++ b/src/include/taler_amount_lib.h
@@ -251,6 +251,20 @@ TALER_amount_add (struct TALER_Amount *sum,
                   const struct TALER_Amount *a2);
 
 
+/**
+ * Divide an amount by a float.  Note that this function
+ * may introduce a rounding error!
+ *
+ * @param result where to store @a dividend / @a divisor
+ * @param dividend amount to divide
+ * @param divisor by what to divide, must be positive
+ */
+void
+TALER_amount_divide (struct TALER_Amount *result,
+                     const struct TALER_Amount *dividend,
+                     uint32_t divisor);
+
+
 /**
  * Normalize the given amount.
  *
diff --git a/src/include/taler_error_codes.h b/src/include/taler_error_codes.h
index e47cff77c..c8a030fac 100644
--- a/src/include/taler_error_codes.h
+++ b/src/include/taler_error_codes.h
@@ -1005,6 +1005,21 @@ enum TALER_ErrorCode
    */
   TALER_EC_PAY_FAILED_COMPUTE_PROPOSAL_HASH = 2123,
 
+  /**
+   * Failed to locate merchant's account information matching the
+   * wire hash given in the proposal.
+   * This response is
+   * provided with HTTP status code MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_PAY_WIRE_HASH_UNKNOWN = 2124,
+
+  /**
+   * We got different currencies for the wire fee and the maximum wire
+   * fee.  This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_PAY_WIRE_FEE_CURRENCY_MISSMATCH = 2125,
+
 
   /**
    * Integer overflow with sepcified timestamp argument detected.
diff --git a/src/util/amount.c b/src/util/amount.c
index 407232a9e..7684ddf32 100644
--- a/src/util/amount.c
+++ b/src/util/amount.c
@@ -565,4 +565,32 @@ TALER_amount_to_string (const struct TALER_Amount *amount)
 }
 
 
+/**
+ * Divide an amount by a float.  Note that this function
+ * may introduce a rounding error!
+ *
+ * @param result where to store @a dividend / @a divisor
+ * @param dividend amount to divide
+ * @param divisor by what to divide, must be positive
+ */
+void
+TALER_amount_divide (struct TALER_Amount *result,
+                     const struct TALER_Amount *dividend,
+                     uint32_t divisor)
+{
+  uint64_t modr;
+
+  GNUNET_assert (0 != divisor);
+  *result = *dividend;
+  if (1 == divisor)
+    return;
+  modr = result->value % divisor;
+  result->value /= divisor;
+  /* modr is a 32-bit value, so we can safely multiply by (<32-bit) base and add fraction! */
+  modr = (modr * TALER_AMOUNT_FRAC_BASE) + result->fraction;
+  GNUNET_assert (modr < TALER_AMOUNT_FRAC_BASE * divisor);
+  result->fraction = (uint32_t) (modr / divisor);
+}
+
+
 /* end of amount.c */
diff --git a/src/util/test_amount.c b/src/util/test_amount.c
index e176d2131..3854297dd 100644
--- a/src/util/test_amount.c
+++ b/src/util/test_amount.c
@@ -197,6 +197,43 @@ main(int argc,
 		 TALER_amount_subtract (&a3, &a1, &a2));
   GNUNET_assert (UINT64_MAX - 1 == a3.value);
   GNUNET_assert (TALER_AMOUNT_FRAC_BASE - 1 == a3.fraction);
+
+  /* test division */
+  GNUNET_assert (GNUNET_OK ==
+		 TALER_string_to_amount ("EUR:3.33",
+					 &a1));
+  TALER_amount_divide (&a2,
+                       &a1,
+                       1);
+  GNUNET_assert (0 == strcasecmp ("EUR",
+				  a2.currency));
+  GNUNET_assert (3 == a2.value);
+  GNUNET_assert (TALER_AMOUNT_FRAC_BASE / 100 * 33 == a2.fraction);
+
+  TALER_amount_divide (&a2,
+                       &a1,
+                       3);
+  GNUNET_assert (0 == strcasecmp ("EUR",
+				  a2.currency));
+  GNUNET_assert (1 == a2.value);
+  GNUNET_assert (TALER_AMOUNT_FRAC_BASE / 100 * 11 == a2.fraction);
+
+  TALER_amount_divide (&a2,
+                       &a1,
+                       2);
+  GNUNET_assert (0 == strcasecmp ("EUR",
+				  a2.currency));
+  GNUNET_assert (1 == a2.value);
+  GNUNET_assert (TALER_AMOUNT_FRAC_BASE / 1000 * 665 == a2.fraction);
+  TALER_amount_divide (&a2,
+                       &a1,
+                       TALER_AMOUNT_FRAC_BASE * 2);
+  GNUNET_assert (0 == strcasecmp ("EUR",
+				  a2.currency));
+  GNUNET_assert (0 == a2.value);
+  GNUNET_assert (1 == a2.fraction);
+
+
   return 0;
 }
 
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