diff options
Diffstat (limited to 'misc.h')
| -rw-r--r-- | misc.h | 46 |
1 files changed, 44 insertions, 2 deletions
@@ -1113,6 +1113,47 @@ inline T1 SaturatingSubtract1(const T1 &a, const T2 &b) return T1((a > b) ? (a - b) : 1);
}
+/// \brief Get the appropriate mask to do a truncating cast
+template <class T, size_t SIZE = sizeof(T)>
+struct TruncatingMask;
+
+template <class T>
+struct TruncatingMask<T, 1>
+{
+ T operator()()
+ {
+ return 0xFF;
+ }
+};
+
+template <class T>
+struct TruncatingMask<T, 2>
+{
+ T operator()()
+ {
+ return 0xFFFF;
+ }
+};
+
+template <class T>
+struct TruncatingMask<T, 4>
+{
+ T operator()()
+ {
+ return 0xFFFFFFFF;
+ }
+};
+
+template <class T>
+struct TruncatingMask<T, 8>
+{
+ T operator()()
+ {
+ return 0xFFFFFFFFFFFFFFFF;
+ }
+};
+
+
/// \brief Reduces a value to a power of 2
/// \tparam T1 class or type
/// \tparam T2 class or type
@@ -1125,8 +1166,9 @@ template <class T1, class T2> inline T2 ModPowerOf2(const T1 &a, const T2 &b)
{
CRYPTOPP_ASSERT(IsPowerOf2(b));
- // Coverity finding CID 170383 Overflowed return value (INTEGER_OVERFLOW)
- return T2(a) & SaturatingSubtract(b,1U);
+ // Coverity finding CID 170383 Overflowed return value (INTEGER_OVERFLOW)
+ // Visual studio runtime_checks don't like us truncating here with the cast to T2 TruncatingMask works around it
+ return T2(a & TruncatingMask<T2>()()) & SaturatingSubtract(b,1U);
}
/// \brief Rounds a value down to a multiple of a second value
|