2 files changed, 65 insertions, 0 deletions
diff --git a/src/cryptonote_basic/cryptonote_format_utils.cpp b/src/cryptonote_basic/cryptonote_format_utils.cpp
index 1bc6b6377..d8f9bb176 100644
--- a/src/cryptonote_basic/cryptonote_format_utils.cpp
+++ b/src/cryptonote_basic/cryptonote_format_utils.cpp
@@ -1064,6 +1064,69 @@ namespace cryptonote
     return s;
   }
   //---------------------------------------------------------------
+  uint64_t round_money_up(uint64_t amount, unsigned significant_digits)
+  {
+    // round monetary amount up with the requested amount of significant digits
+
+    CHECK_AND_ASSERT_THROW_MES(significant_digits > 0, "significant_digits must not be 0");
+    static_assert(sizeof(unsigned long long) == sizeof(uint64_t), "Unexpected unsigned long long size");
+
+    // we don't need speed, so we do it via text, as it's easier to get right
+    char buf[32];
+    snprintf(buf, sizeof(buf), "%llu", (unsigned long long)amount);
+    const size_t len = strlen(buf);
+    if (len > significant_digits)
+    {
+      bool bump = false;
+      char *ptr;
+      for (ptr = buf + significant_digits; *ptr; ++ptr)
+      {
+        // bump digits by one if the following digits past significant digits were to be 5 or more
+        if (*ptr != '0')
+        {
+          bump = true;
+          *ptr = '0';
+        }
+      }
+      ptr = buf + significant_digits;
+      while (bump && ptr > buf)
+      {
+        --ptr;
+        // bumping a nine overflows
+        if (*ptr == '9')
+          *ptr = '0';
+        else
+        {
+          // bumping another digit means we can stop bumping (no carry)
+          ++*ptr;
+          bump = false;
+        }
+      }
+      if (bump)
+      {
+        // carry reached the highest digit, we need to add a 1 in front
+        size_t offset = strlen(buf);
+        for (size_t i = offset + 1; i > 0; --i)
+          buf[i] = buf[i - 1];
+        buf[0] = '1';
+      }
+    }
+    char *end = NULL;
+    errno = 0;
+    const unsigned long long ull = strtoull(buf, &end, 10);
+    CHECK_AND_ASSERT_THROW_MES(ull != ULONG_MAX || errno == 0, "Failed to parse rounded amount: " << buf);
+    CHECK_AND_ASSERT_THROW_MES(ull != 0 || amount == 0, "Overflow in rounding");
+    return ull;
+  }
+  //---------------------------------------------------------------
+  std::string round_money_up(const std::string &s, unsigned significant_digits)
+  {
+    uint64_t amount;
+    CHECK_AND_ASSERT_THROW_MES(parse_amount(amount, s), "Failed to parse amount: " << s);
+    amount = round_money_up(amount, significant_digits);
+    return print_money(amount);
+  }
+  //---------------------------------------------------------------
   crypto::hash get_blob_hash(const blobdata& blob)
   {
     crypto::hash h = null_hash;
diff --git a/src/cryptonote_basic/cryptonote_format_utils.h b/src/cryptonote_basic/cryptonote_format_utils.h
index 25cd89e99..ce3ce7492 100644
--- a/src/cryptonote_basic/cryptonote_format_utils.h
+++ b/src/cryptonote_basic/cryptonote_format_utils.h
@@ -144,6 +144,8 @@ namespace cryptonote
   std::string get_unit(unsigned int decimal_point = -1);
   std::string print_money(uint64_t amount, unsigned int decimal_point = -1);
   std::string print_money(const boost::multiprecision::uint128_t &amount, unsigned int decimal_point = -1);
+  uint64_t round_money_up(uint64_t amount, unsigned significant_digits);
+  std::string round_money_up(const std::string &amount, unsigned significant_digits);
   //---------------------------------------------------------------
   template<class t_object>
   bool t_serializable_object_from_blob(t_object& to, const blobdata& b_blob)