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common/math: delete unused function Exp

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Aaron Chen 2024-03-09 13:29:42 +08:00 committed by GitHub
parent e31709db65
commit b92564c014
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2 changed files with 0 additions and 36 deletions
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20
common/math/big.go
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@ -248,23 +248,3 @@ func S256(x *big.Int) *big.Int {
} }
return new(big.Int).Sub(x, tt256) return new(big.Int).Sub(x, tt256)
} }
// Exp implements exponentiation by squaring.
// Exp returns a newly-allocated big integer and does not change
// base or exponent. The result is truncated to 256 bits.
//
// 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 < wordBits; i++ {
if word&1 == 1 {
U256(result.Mul(result, base))
}
U256(base.Mul(base, base))
word >>= 1
}
}
return result
}

16
common/math/big_test.go
View file

@ -306,19 +306,3 @@ func TestS256(t *testing.T) {
} }
} }
} }
func TestExp(t *testing.T) {
tests := []struct{ base, exponent, result *big.Int }{
{base: big.NewInt(0), exponent: big.NewInt(0), result: big.NewInt(1)},
{base: big.NewInt(1), exponent: big.NewInt(0), result: big.NewInt(1)},
{base: big.NewInt(1), exponent: big.NewInt(1), result: big.NewInt(1)},
{base: big.NewInt(1), exponent: big.NewInt(2), result: big.NewInt(1)},
{base: big.NewInt(3), exponent: big.NewInt(144), result: MustParseBig256("507528786056415600719754159741696356908742250191663887263627442114881")},
{base: big.NewInt(2), exponent: big.NewInt(255), result: MustParseBig256("57896044618658097711785492504343953926634992332820282019728792003956564819968")},
}
for _, test := range tests {
if result := Exp(test.base, test.exponent); result.Cmp(test.result) != 0 {
t.Errorf("Exp(%d, %d) = %d, want %d", test.base, test.exponent, result, test.result)
}
}
}