assert(n <= d && "Probability must be less or equal to 1.");
- // If we can overflow use 96-bit operations.
- if (n > 0 && Frequency > UINT64_MAX / n) {
+ // Calculate Frequency * n.
+ uint64_t mulLo = (Frequency & UINT32_MAX) * n;
+ uint64_t mulHi = (Frequency >> 32) * n;
+ uint64_t mulRes = (mulHi << 32) + mulLo;
+
+ // If there was overflow use 96-bit operations.
+ if (mulHi > UINT32_MAX || mulRes < mulLo) {
// 96-bit value represented as W[1]:W[0].
uint64_t W[2];
return *this;
}
- Frequency *= n;
- Frequency /= d;
+ Frequency = mulRes / d;
return *this;
}