add amount division API and test case

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.
  *

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.

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 */

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;
 }