minor optimizations of the modexp builtin
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8d04dffe69
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ca27234a59
@ -111,7 +111,7 @@ impl Builtin {
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pub fn cost(&self, input: &[u8]) -> U256 { self.pricer.cost(input) }
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/// Simple forwarder for execute.
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pub fn execute(&self, input: &[u8], output: &mut BytesRef) -> Result<(), Error> {
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pub fn execute(&self, input: &[u8], output: &mut BytesRef) -> Result<(), Error> {
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self.native.execute(input, output)
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}
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@ -288,9 +288,11 @@ impl Impl for ModexpImpl {
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let exp = read_num(exp_len);
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let modulus = read_num(mod_len);
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// calculate modexp: exponentiation by squaring.
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// calculate modexp: exponentiation by squaring. the `num` crate has pow, but not modular.
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fn modexp(mut base: BigUint, mut exp: BigUint, modulus: BigUint) -> BigUint {
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match (base == BigUint::zero(), exp == BigUint::zero()) {
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use num::Integer;
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match (base.is_zero(), exp.is_zero()) {
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(_, true) => return BigUint::one(), // n^0 % m
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(true, false) => return BigUint::zero(), // 0^n % m, n>0
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(false, false) if modulus <= BigUint::one() => return BigUint::zero(), // a^b % 1 = 0.
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@ -301,10 +303,9 @@ impl Impl for ModexpImpl {
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base = base % &modulus;
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// fast path for base divisible by modulus.
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if base == BigUint::zero() { return result }
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while exp != BigUint::zero() {
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// exp has to be on the right here to avoid move.
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if BigUint::one() & &exp == BigUint::one() {
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if base.is_zero() { return result }
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while !exp.is_zero() {
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if exp.is_odd() {
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result = (result * &base) % &modulus;
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}
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@ -331,22 +332,22 @@ impl Impl for ModexpImpl {
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fn read_fr(reader: &mut io::Chain<&[u8], io::Repeat>) -> Result<::bn::Fr, Error> {
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let mut buf = [0u8; 32];
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reader.read_exact(&mut buf[..]).expect("reading from zero-extended memory cannot fail; qed");
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::bn::Fr::from_slice(&buf[0..32]).map_err(|_| Error::from("Invalid field element"))
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}
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fn read_point(reader: &mut io::Chain<&[u8], io::Repeat>) -> Result<::bn::G1, Error> {
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use bn::{Fq, AffineG1, G1, Group};
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let mut buf = [0u8; 32];
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reader.read_exact(&mut buf[..]).expect("reading from zero-extended memory cannot fail; qed");
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let px = Fq::from_slice(&buf[0..32]).map_err(|_| Error::from("Invalid point x coordinate"))?;
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reader.read_exact(&mut buf[..]).expect("reading from zero-extended memory cannot fail; qed");
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let py = Fq::from_slice(&buf[0..32]).map_err(|_| Error::from("Invalid point x coordinate"))?;
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Ok(
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if px == Fq::zero() && py == Fq::zero() {
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G1::zero()
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@ -374,7 +375,7 @@ impl Impl for Bn128AddImpl {
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output.write(0, &write_buf);
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Ok(())
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}
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}
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}
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impl Impl for Bn128MulImpl {
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@ -394,7 +395,7 @@ impl Impl for Bn128MulImpl {
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}
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output.write(0, &write_buf);
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Ok(())
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}
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}
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}
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mod bn128_gen {
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@ -420,13 +421,13 @@ mod bn128_gen {
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.expect("a valid field element"),
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Fq::from_str("4082367875863433681332203403145435568316851327593401208105741076214120093531")
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.expect("a valid field element"),
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),
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),
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).expect("the generator P2(10857046999023057135944570762232829481370756359578518086990519993285655852781 + 11559732032986387107991004021392285783925812861821192530917403151452391805634i, 8495653923123431417604973247489272438418190587263600148770280649306958101930 + 4082367875863433681332203403145435568316851327593401208105741076214120093531i) is a valid curve point"));
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}
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}
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lazy_static! {
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pub static ref P1_P2_PAIRING: Gt = pairing(P1.clone(), P2.clone());
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}
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}
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}
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impl Impl for Bn128PairingImpl {
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@ -438,8 +439,8 @@ impl Impl for Bn128PairingImpl {
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use bn::{AffineG1, AffineG2, Fq, Fq2, pairing, G1, G2, Gt};
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let elements = input.len() / 192; // (a, b_a, b_b - each 64-byte affine coordinates)
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if input.len() % 192 != 0 {
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return Err("Invalid input length, must be multiple of 192 (3 * (32*2))".into())
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if input.len() % 192 != 0 {
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return Err("Invalid input length, must be multiple of 192 (3 * (32*2))".into())
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}
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let ret_val = if input.len() == 0 {
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U256::one()
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@ -459,11 +460,11 @@ impl Impl for Bn128PairingImpl {
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.map_err(|_| Error::from("Invalid b argument imaginary coeff y coordinate"))?;
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let b_a_x = Fq::from_slice(&input[idx*192+128..idx*192+160])
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.map_err(|_| Error::from("Invalid b argument real coeff x coordinate"))?;
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.map_err(|_| Error::from("Invalid b argument real coeff x coordinate"))?;
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let b_a_y = Fq::from_slice(&input[idx*192+160..idx*192+192])
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.map_err(|_| Error::from("Invalid b argument real coeff y coordinate"))?;
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.map_err(|_| Error::from("Invalid b argument real coeff y coordinate"))?;
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vals.push((
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G1::from(
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AffineG1::new(a_x, a_y).map_err(|_| Error::from("Invalid a argument - not on curve"))?
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@ -719,7 +720,7 @@ mod tests {
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pricer: Box::new(Linear { base: 0, word: 0 }),
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native: ethereum_builtin("bn128_add"),
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activate_at: 0,
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};
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};
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// zero-points additions
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{
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@ -738,7 +739,7 @@ mod tests {
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f.execute(&input[..], &mut BytesRef::Fixed(&mut output[..])).expect("Builtin should not fail");
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assert_eq!(output, expected);
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}
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}
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// no input, should not fail
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@ -754,7 +755,7 @@ mod tests {
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f.execute(&input[..], &mut BytesRef::Fixed(&mut output[..])).expect("Builtin should not fail");
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assert_eq!(output, expected);
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}
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}
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// should fail - point not on curve
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{
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@ -769,7 +770,7 @@ mod tests {
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let res = f.execute(&input[..], &mut BytesRef::Fixed(&mut output[..]));
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assert!(res.is_err(), "There should be built-in error here");
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}
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}
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}
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@ -781,7 +782,7 @@ mod tests {
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pricer: Box::new(Linear { base: 0, word: 0 }),
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native: ethereum_builtin("bn128_mul"),
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activate_at: 0,
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};
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};
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// zero-point multiplication
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{
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@ -799,7 +800,7 @@ mod tests {
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f.execute(&input[..], &mut BytesRef::Fixed(&mut output[..])).expect("Builtin should not fail");
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assert_eq!(output, expected);
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}
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}
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// should fail - point not on curve
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{
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@ -813,7 +814,7 @@ mod tests {
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let res = f.execute(&input[..], &mut BytesRef::Fixed(&mut output[..]));
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assert!(res.is_err(), "There should be built-in error here");
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}
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}
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}
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fn builtin_pairing() -> Builtin {
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@ -826,12 +827,12 @@ mod tests {
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fn empty_test(f: Builtin, expected: Vec<u8>) {
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let mut empty = [0u8; 0];
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let input = BytesRef::Fixed(&mut empty);
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let input = BytesRef::Fixed(&mut empty);
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let mut output = vec![0u8; expected.len()];
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f.execute(&input[..], &mut BytesRef::Fixed(&mut output[..])).expect("Builtin should not fail");
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assert_eq!(output, expected);
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assert_eq!(output, expected);
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}
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fn error_test(f: Builtin, input: &[u8], msg_contains: Option<&str>) {
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@ -851,12 +852,12 @@ mod tests {
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fn bytes(s: &'static str) -> Vec<u8> {
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FromHex::from_hex(s).expect("static str should contain valid hex bytes")
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}
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#[test]
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fn bn128_pairing_empty() {
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// should not fail, because empty input is a valid input of 0 elements
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empty_test(
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builtin_pairing(),
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builtin_pairing(),
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bytes("0000000000000000000000000000000000000000000000000000000000000001"),
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);
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}
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@ -890,7 +891,7 @@ mod tests {
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),
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Some("Invalid input length"),
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);
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}
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}
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#[test]
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#[should_panic]
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@ -953,4 +954,4 @@ mod tests {
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b.execute(&i[..], &mut BytesRef::Fixed(&mut o[..])).expect("Builtin should not fail");
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assert_eq!(i, o);
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}
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}
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}
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