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