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0xInu~ _packedOwnershipOf optimization, saving 2143 gas on transfers #433

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Nov 15, 2022
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0xInu~ _packedOwnershipOf optimization, saving 2143 gas on transfers #433

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17 changes: 14 additions & 3 deletions contracts/ERC721A.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -343,13 +343,23 @@ contract ERC721A is IERC721A {
/**
* Returns the packed ownership data of `tokenId`.
*/
function _packedOwnershipOf(uint256 tokenId) private view returns (uint256) {
function _packedOwnershipOf(uint256 tokenId) private view returns (uint256) {
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uint256 curr = tokenId;

unchecked {
if (_startTokenId() <= curr)
if (_startTokenId() <= curr) {

// load the packed ownership of the current tokenId
uint256 packed = _packedOwnerships[curr];

// If the data exists, and it's not burned, return it and skip tracing
// This is possible because we have already achieved the target condition
// This saves 2143 gas on transfers of initialized tokens.
if (packed != 0 && packed & _BITMASK_BURNED == 0) return packed;

// If the tokenId is within index-bounds
if (curr < _currentIndex) {
uint256 packed = _packedOwnerships[curr];

// If not burned.
if (packed & _BITMASK_BURNED == 0) {
// Invariant:
Expand All @@ -367,6 +377,7 @@ contract ERC721A is IERC721A {
return packed;
}
}
}
}
revert OwnerQueryForNonexistentToken();
}
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