diff --git a/contrib/epee/include/misc_language.h b/contrib/epee/include/misc_language.h index 5f7202150..a04c63231 100644 --- a/contrib/epee/include/misc_language.h +++ b/contrib/epee/include/misc_language.h @@ -106,6 +106,14 @@ namespace misc_utils return true; } + template + T get_mid(const T &a, const T &b) + { + //returns the average of two numbers; overflow safe and works with at least all integral and floating point types + //(a+b)/2 = (a/2) + (b/2) + ((a - 2*(a/2)) + (b - 2*(b/2)))/2 + return (a/2) + (b/2) + ((a - 2*(a/2)) + (b - 2*(b/2)))/2; + } + template type_vec_type median(std::vector &v) { @@ -122,7 +130,7 @@ namespace misc_utils return v[n]; }else {//2, 4, 6... - return (v[n-1] + v[n])/2; + return get_mid(v[n-1],v[n]); } } diff --git a/contrib/epee/include/rolling_median.h b/contrib/epee/include/rolling_median.h index 11275aa70..088a71d3e 100644 --- a/contrib/epee/include/rolling_median.h +++ b/contrib/epee/include/rolling_median.h @@ -34,6 +34,8 @@ #pragma once +#include "misc_language.h" + #include #include @@ -226,7 +228,7 @@ public: Item v = data[heap[0]]; if (minCt < maxCt) { - v = (v + data[heap[-1]]) / 2; + v = get_mid(v, data[heap[-1]]); } return v; } diff --git a/tests/unit_tests/rolling_median.cpp b/tests/unit_tests/rolling_median.cpp index 730f1e7c5..d415c5b95 100644 --- a/tests/unit_tests/rolling_median.cpp +++ b/tests/unit_tests/rolling_median.cpp @@ -170,6 +170,17 @@ TEST(rolling_median, history_blind) } } +TEST(rolling_median, overflow) +{ + epee::misc_utils::rolling_median_t m(2); + + uint64_t over_half = static_cast(3) << static_cast(62); + m.insert(over_half); + m.insert(over_half); + ASSERT_EQ((over_half + over_half) < over_half, true); + ASSERT_EQ(over_half, m.median()); +} + TEST(rolling_median, size) { epee::misc_utils::rolling_median_t m(10);