[#2658] add big integer support to statistics

Pool capacities have been promoted in code from uint64_t to uint128_t.

Bigint is modelled as an int128_t in statistics, following the precedent of
signed integer of int64_t from statistics.

- "total-nas" is extended to 128 bits as requested in the issue.
- "total-pds" has the same risk of overflowing so it has been extended
  as well.
- "total-addresses" always fits in 64 bits, but certain code forces a
  128 bit value on it. See Pool::getCapacity(), Subnet::getPoolCapacity(),
  Subnet::sumPoolCapacity(). It could have been truncated to a 64 bit value,
  but that seems like an unnecessary complication.

Because of the disparity in signedness there is some truncation that can
happen when pool capacity values are passed on to statistics. That only happens
for the last half of the value range, so for prefix ranges larger than /1.

1 files changed, 5 insertions, 4 deletions

diff --git a/src/lib/asiolink/addr_utilities.h b/src/lib/asiolink/addr_utilities.h
index bd78deec4c..9aa9af2d10 100644
--- a/src/lib/asiolink/addr_utilities.h
+++ b/src/lib/asiolink/addr_utilities.h
@@ -8,6 +8,7 @@
 #define ADDR_UTILITIES_H
 
 #include <asiolink/io_address.h>
+#include <util/bigints.h>
 
 namespace isc {
 namespace asiolink {
@@ -54,7 +55,7 @@ IOAddress getNetmask4(uint8_t len);
 /// @param min the first address in range
 /// @param max the last address in range
 /// @return number of addresses in range
-uint64_t addrsInRange(const IOAddress& min, const IOAddress& max);
+isc::util::uint128_t addrsInRange(const IOAddress& min, const IOAddress& max);
 
 /// @brief Returns prefix length from the specified range (min - max).
 ///
@@ -78,7 +79,7 @@ int prefixLengthFromRange(const IOAddress& min, const IOAddress& max);
 /// @param pool_len length of the pool in bits
 /// @param delegated_len length of the prefixes to be delegated from the pool
 /// @return number of prefixes in range
-uint64_t prefixesInRange(const uint8_t pool_len, const uint8_t delegated_len);
+isc::util::uint128_t prefixesInRange(const uint8_t pool_len, const uint8_t delegated_len);
 
 /// @brief Finds the address increased by offset.
 ///
@@ -92,7 +93,7 @@ uint64_t prefixesInRange(const uint8_t pool_len, const uint8_t delegated_len);
 /// @return address being offset greater than the input address
 IOAddress offsetAddress(const IOAddress& addr, uint64_t offset);
 
-};
-};
+}  // namespace asiolink
+}  // namespace isc
 
 #endif // ADDR_UTILITIES_H