59 lines
2.6 KiB
Markdown
59 lines
2.6 KiB
Markdown
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---
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eip: 5615
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title: ERC-1155 Supply Extension
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description: A simple mechanism to fetch token supply data from ERC-1155 tokens
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author: Gavin John (@Pandapip1)
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discussions-to: https://ethereum-magicians.org/t/eip-5615-eip-1155-supply-extension/10732
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status: Review
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type: Standards Track
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category: ERC
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created: 2022-09-07
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requires: 1155
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---
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## Abstract
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This ERC standardizes an existing mechanism to fetch token supply data from [ERC-1155](./eip-1155.md) tokens. It adds a `totalSupply` function, which fetches the number of tokens with a given `id`, and an `exists` function, which checks for the existence of a given `id`.
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## Specification
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The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC 2119.
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```solidity
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interface ERC1155Supply is ERC1155 {
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// @notice This function MUST return whether the given token id exists, previously existed, or may exist
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// @param id The token id of which to check the existence
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// @return Whether the given token id exists, previously existed, or may exist
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function exists(uint256 id) external view returns (bool);
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// @notice This function MUST return the number of tokens with a given id. If the token id does not exist, it MUST return 0.
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// @param id The token id of which fetch the total supply
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// @return The total supply of the given token id
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function totalSupply(uint256 id) external view returns (uint256);
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}
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```
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Implementations MAY support [ERC-165](./eip-165.md) interface discovery, but consumers MUST NOT rely on it.
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## Rationale
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This ERC does not implement [ERC-165](./eip-165.md), as this interface is simple enough that the extra complexity is unnecessary and would cause incompatibilities with pre-existing implementations.
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The `totalSupply` and `exists` functions were modeled after [ERC-721](./eip-721.md) and [ERC-20](./eip-20.md).
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`totalSupply` does not revert if the token ID does not exist, since contracts that care about that case should use `exists` instead (which might return false even if `totalSupply` is zero).
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`exists` is included to differentiate between the two ways that `totalSupply` could equal zero (either no tokens with the given ID have been minted yet, or no tokens with the given ID will ever be minted).
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## Backwards Compatibility
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This ERC is designed to be backward compatible with the OpenZeppelin `ERC1155Supply`.
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## Security Considerations
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None.
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## Copyright
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Copyright and related rights waived via [CC0](../LICENSE.md).
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