modify traceAncestor to support N-ary #28
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merge optimism
merge from optimism
qizhou
reviewed
May 18, 2024
| // state's depth in relation to the parent, we don't need another | ||
| // branch because (n - n) % 2 == 0. | ||
| bool validStep = VM.step(_stateData, _proof, uuid.raw()) == postState.claim.raw(); | ||
| bool parentPostAgree = (parentPos.depth() - postState.position.depth()) % 2 == 0; |
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It will be great if we can update the comment accordingly.
| { | ||
| // Grab the trace ancestor's expected position. | ||
| Position traceAncestorPos = _global ? _pos.traceAncestor() : _pos.traceAncestorBounded(SPLIT_DEPTH); | ||
| Position traceAncestorPos = _global ? _pos.traceAncestorBounded(nBits - 1) : _pos.traceAncestorBounded(SPLIT_DEPTH); |
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I am not sure _pos.traceAncestorBounded(nBits - 1) is correct for both nBits == 1 and nBits > 1 cases.
For example, traceAncestor(3) = 1, while traceAncestorBounded(3, 0) = 3
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qizhou
reviewed
May 21, 2024
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| function traceAncestorV2(Position _position) public view returns (Position ancestor_) { | ||
| if (_position.depth() < nBits) { | ||
| revert ClaimAboveSplit(); | ||
| } | ||
| ancestor_ = _position.traceAncestor(); | ||
| // Position 1 is not the value submitted by the Actors. | ||
| if (1 == ancestor_.raw()) { | ||
| return ancestor_; | ||
| } | ||
| // The depth of the ancestor must not be less than the depth of the first attack position. | ||
| for (uint64 start = ancestor_.depth(); start < nBits; start++) { | ||
| ancestor_ = Position.wrap(ancestor_.raw() * 2 + 1); | ||
| } | ||
| } |
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I guess the code should be
Suggested change
| function traceAncestorV2(Position _position) public view returns (Position ancestor_) { | |
| if (_position.depth() < nBits) { | |
| revert ClaimAboveSplit(); | |
| } | |
| ancestor_ = _position.traceAncestor(); | |
| // Position 1 is not the value submitted by the Actors. | |
| if (1 == ancestor_.raw()) { | |
| return ancestor_; | |
| } | |
| // The depth of the ancestor must not be less than the depth of the first attack position. | |
| for (uint64 start = ancestor_.depth(); start < nBits; start++) { | |
| ancestor_ = Position.wrap(ancestor_.raw() * 2 + 1); | |
| } | |
| } | |
| function traceAncestorV2(Position _position) public view returns (Position ancestor_) { | |
| if (_position.depth() % nBits != 0) { | |
| revert SomeError(); | |
| } | |
| return _position.traceAncestor().roundUp(nBits); | |
| } |
For example, when nBits = 2 and position = 17, it should return 17 rather than 8.
| // Grab the trace ancestor's expected position. | ||
| Position traceAncestorPos = _global ? _pos.traceAncestor() : _pos.traceAncestorBounded(SPLIT_DEPTH); | ||
| Position traceAncestorPos = _global | ||
| ? traceAncestorV2(_pos) : _pos.traceAncestorBounded(findFirstValueDepth(SPLIT_DEPTH)); |
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If we assume SPLIT_DEPTH % nBits == 0, I believe code can be
Suggested change
| ? traceAncestorV2(_pos) : _pos.traceAncestorBounded(findFirstValueDepth(SPLIT_DEPTH)); | |
| ? traceAncestor(_pos).roundUp(nBits): _pos.traceAncestorBounded(SPLIT_DEPTH + nBits - 1).roundUp(nBits); |
where
function roundUp(Position _position, uint256 _nBits) internal pure returns (Position _roundUp) {
_roundUp = _position;
for (uint64 start = _roundUp.depth(); start % _nBits != 0; start++) {
_roundUp = _roundUp.right();
}
return _roundUp;
}
or
function roundUp(Position _position, uint256 _nBits) internal pure returns (Position _roundUp) {
uint256 targetDepth = _position.depth();
if (targetDepth % _nBits != 0) {
targetDepth = targetDepth + _nBits - targetDepth % nBits;
}
return _position.rightIndex(targetDepth);
}
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| function _traceAncestorV2(Position _position, uint256 _intervalDepth) | ||
| internal | ||
| pure | ||
| returns (Position ancestor_) | ||
| { | ||
| if (_position.depth() % _intervalDepth != 0 || _position.depth() < _intervalDepth) { | ||
| revert InvalidClaim(); | ||
| } | ||
| ancestor_ = _position.traceAncestor(); | ||
| // Position 1 is not the value submitted by the Actors. | ||
| if (1 == ancestor_.raw()) { | ||
| return ancestor_; | ||
| } | ||
| return _firstValidPosition(ancestor_, _intervalDepth); | ||
| } |
Check failure
Code scanning / Slither
Weak PRNG
qizhou
reviewed
May 22, 2024
| pure | ||
| returns (Position ancestor_) | ||
| { | ||
| if (_position.depth() % _intervalDepth != 0 || _position.depth() < _intervalDepth) { |
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I think _traceAncestorV2(pos, 1) should behave the same as _traceAncestor, which accept
| revert InvalidClaim(); | ||
| } | ||
| ancestor_ = _position.traceAncestor(); | ||
| // Position 1 is not the value submitted by the Actors. |
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I am not sure of the comment's meaning. In addition, I do not think we need a special check for 1 == ancestor_.raw()
| /// @param _position Current location | ||
| /// @param _intervalDepth The depth of the interval with each submission. | ||
| /// @return first_ First valid location | ||
| function _firstValidPosition(Position _position, uint256 _intervalDepth) |
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first may be confusing since it can be vertical (depth) or horizontal.
I think we can use validRightIndex or firstValidRightIndex.
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| function _firstValidRightIndex(Position _position, uint256 _intervalDepth) | ||
| internal | ||
| pure | ||
| returns (Position first_) | ||
| { | ||
| first_ = _position; | ||
| for (uint64 start = first_.depth(); start % _intervalDepth != 0; start++) { | ||
| first_ = first_.right(); | ||
| } | ||
| } |
Check failure
Code scanning / Slither
Weak PRNG
qizhou
approved these changes
May 23, 2024
| /// @param _position Current location | ||
| /// @param _intervalDepth The depth of the interval with each submission. | ||
| /// @return first_ First valid location | ||
| function _firstValidRightIndex(Position _position, uint256 _intervalDepth) |
Author
|
fix by #35 |
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