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ERC-1155: Semi Fungible Token Standard implementation

This repository maintains a secure, efficient and standards-compliant implementation of the ERC-1155 token standard for Ethereum. The implementation was created during Horizon Blockchain Games' participation in the coauthoring of the ERC-1155 and is used by Skyweaver, Opensea, and many other projects since its release.

The ERC-1155 token standard contains multiple classes of tokens referenced by IDs from non-fungible (max supply=1), to semi-fungible (supply=low), to highly fungible (supply=high). Standard interface discussion at ERC-1155.

Getting started

Install

yarn add @0xsequence/erc-1155 or npm install @0xsequence/erc-1155

Usage

pragma solidity ^0.8.0;

import '@0xsequence/erc-1155/contracts/tokens/ERC1155/ERC1155.sol';

contract MyERC1155Token is ERC1155 {
  ...
}

Description

The contracts in this repository follow a standard implementation of an (ERC-1155 contract. This standard provides basic functionality to track and transfer multiple tokens and the interface provide an API other contracts and off-chain third parties can use.

ERC-1155 contracts keep track of many token balances, which can lead to significant efficiency gains when batch transferring multiple token classes simultaneously. This is particularly useful for fungible tokens that are likely to be transfered together, such as gaming items (cards, weapons, parts of objects, minerals, etc.). The possible efficiency gains are more significant if the amount of tokens each address can own is capped, as shown in this implementation examples.

This repository contains two main implementations of the ERC-1155 token standard: ERC1155 and ERC155PackedBalance. The latter implementation packs multiple balances within a single uint256 using bitwise operations. This brings the cost of transferring 100 different token classes to 467,173 gas, an average of 4,671 gas per token type transfer. Still using MT, but without balance packing, transferring 100 different token types costs 2,763,399 gas, an average of 27,633 gas per token transfer. The latter is already an improvement over multiple fungible tokens that are stored on different contracts, since cross-contract calls have a base cost of 700 gas. This is ignoring the cost of initial approvals that would need to be set for each user and existing ERC-20 tokens.

Specification

A detailed specification document can be found at SPECIFICATIONS.md.

Security Review

@0xsequence/erc-1155 has been audited by two independant parties and all issues discovered were addressed.

** Agustín was hired as a full-time employee at Horizon after the audit was completed. Agustín did not take part in the writing of Semi Fungible contracts.

Dev env & release

This repository is configured as a yarn workspace, and has multiple pacakge.json files. Specifically, we have the root ./package.json for the development environment, contract compilation and testing. Contract source code and distribution files are packaged in "src/package.json".

To release a new version, make sure to bump the version, tag it, and run yarn release. The release command will publish the @0xsequence/erc-1155 package in the "src/" folder, separate from the root package. The advantage here is that application developers who consume @0xsequence/erc-1155 aren't required to install any of the devDependencies in their toolchains as our build and contract packages are separated.

LICENSE

Licensed under Apache-2.0