1b73c79234
* common/math, core/vm: implement fast EXP. Courtesy @chfast & @karalabe * common/math: fix go vet issues on exp calculation
29 lines
569 B
Go
29 lines
569 B
Go
package math
|
|
|
|
import (
|
|
"math/big"
|
|
|
|
"github.com/ethereum/go-ethereum/common"
|
|
)
|
|
|
|
// wordSize is the size number of bits in a big.Int Word.
|
|
const wordSize = 32 << (uint64(^big.Word(0))>>63)
|
|
|
|
// Exp implement exponentiation by squaring algorithm.
|
|
//
|
|
// Courtesy @karalabe and @chfast
|
|
func Exp(base, exponent *big.Int) *big.Int {
|
|
result := big.NewInt(1)
|
|
|
|
for _, word := range exponent.Bits() {
|
|
for i := 0; i < wordSize; i++ {
|
|
if word&1 == 1 {
|
|
common.U256(result.Mul(result, base))
|
|
}
|
|
common.U256(base.Mul(base, base))
|
|
word >>= 1
|
|
}
|
|
}
|
|
return result
|
|
}
|