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fixed #1261, overflow when calculating work #1283
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@@ -509,5 +510,11 @@ mod tests { | |||
} | |||
} | |||
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#[test] | |||
fn test_difficulty_to_boundary() { | |||
let _ = Ethash::difficulty_to_boundary(&U256::from(0)); |
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Why not asserting the actuall result?
waiting for the answer... |
@@ -255,12 +255,14 @@ impl Ethash { | |||
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/// Convert an Ethash boundary to its original difficulty. Basically just `f(x) = 2^256 / x`. | |||
pub fn boundary_to_difficulty(boundary: &H256) -> U256 { | |||
U256::from((U512::one() << 256) / U256::from(boundary.as_slice()).into()) | |||
let d = cmp::max(U256::from(boundary), U256::one()); | |||
((U256::one() << 255) / d) << 1 |
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will still overflow if boundary == d == U256::one()
(returning the impossible boundary 0
as the tests confirm).
rather it should probably special-case boundary <= 1
and return !U256::zero()
. see YP(160).
updated |
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geth does it similarly https://github.com/ethereum/go-ethereum/blob/506c9277911746dfbab0a585aee736bd3095f206/miner/remote_agent.go#L112-L127