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chiru-labs / ERC721A

https://ERC721A.org
MIT License
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packedOwnership as lengthless array #394

Open sillytuna opened 2 years ago

sillytuna commented 2 years ago

_packedOwnership access was performing a sha3 op for every new index but as these are consecutive they can be stored as a regular array offset from a base storage location irrespective of the start token id. Only one sha3 is required instead of one per index used. Solidity effectively uses this technique for its arrays but also stores array length, which we don't need to do.

Optimised _packedOwnershipOf accordingly.

Pros Reduces gas usage slightly in common functions but more significantly in bulk transfers (figures below).

Cons 22,772 additional deployment cost Code readability

New

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|  ERC721AGasReporterMock            ·  transferFrom           ·      44232  ·      85751  ·      54612  ·            4  ·          -  │
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|  ERC721AGasReporterMock            ·  transferTenAsc         ·          -  ·          -  ·     295158  ·            1  ·          -  │
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|  ERC721AGasReporterMock            ·  transferTenAvg         ·          -  ·          -  ·     295651  ·            1  ·          -  │
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|  ERC721AGasReporterMock            ·  transferTenDesc        ·          -  ·          -  ·     299608  ·            1  ·          -  │
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|  ERC721AGasReporterMock            ·  transferFrom           ·      44338  ·      86037  ·      54763  ·            4  ·          -  │
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|  ERC721AGasReporterMock            ·  transferTenAsc         ·          -  ·          -  ·     297319  ·            1  ·          -  │
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|  ERC721AGasReporterMock            ·  transferTenAvg         ·          -  ·          -  ·     298166  ·            1  ·          -  │
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|  ERC721AGasReporterMock            ·  transferTenDesc        ·          -  ·          -  ·     303983  ·            1  ·          -  │
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Vectorized commented 2 years ago

O.O

This may require a major version bump, cuz the upgradeable repo requires the storage slots to stay the same.

sillytuna commented 2 years ago

Understand about the storage slot situ.

I've got another optimisation I need to experiment with which may make this less important (tho it'll still save gas). Will check tomorrow. It would also affect storage slots though.