diff --git a/common/math/integer.go b/common/math/integer.go index 93b1d036dd..50d3eba1f5 100644 --- a/common/math/integer.go +++ b/common/math/integer.go @@ -18,6 +18,7 @@ package math import ( "fmt" + "math/bits" "strconv" ) @@ -78,22 +79,20 @@ func MustParseUint64(s string) uint64 { return v } -// NOTE: The following methods need to be optimised using either bit checking or asm - -// SafeSub returns subtraction result and whether overflow occurred. +// SafeSub returns x-y and checks for overflow. func SafeSub(x, y uint64) (uint64, bool) { - return x - y, x < y + diff, borrowOut := bits.Sub64(x, y, 0) + return diff, borrowOut != 0 } -// SafeAdd returns the result and whether overflow occurred. +// SafeAdd returns x+y and checks for overflow. func SafeAdd(x, y uint64) (uint64, bool) { - return x + y, y > MaxUint64-x + sum, carryOut := bits.Add64(x, y, 0) + return sum, carryOut != 0 } -// SafeMul returns multiplication result and whether overflow occurred. +// SafeMul returns x*y and checks for overflow. func SafeMul(x, y uint64) (uint64, bool) { - if x == 0 || y == 0 { - return 0, false - } - return x * y, y > MaxUint64/x + hi, lo := bits.Mul64(x, y) + return lo, hi != 0 }