diff --git a/EIPS/eip-2330.md b/EIPS/eip-2330.md new file mode 100644 index 00000000000000..74dca69de480bb --- /dev/null +++ b/EIPS/eip-2330.md @@ -0,0 +1,68 @@ +--- +eip: 2330 +title: SLOAD2 +author: Dominic Letz (@dominicletz) +discussions-to: https://ethereum-magicians.org/t/eip-2330-sload2-and-abi-for-lower-gas-cost-and-off-chain-apps/3733 +status: Draft +type: Standards Track +category: Core +created: 2019-10-29 +--- + + + +## Simple Summary + +A new `SLOAD2
` EVM opcode to read external contract storage data and corresponding allowing to build registry and token contracts that use less gas. + +## Abstract + +While any off-chain application can read all contract storage data of all contracts, this is not possible for deployed smart contracts themselves. These are bound to use contract calls for any interaction including reading data from other contracts. This EIP adds an EVM opcode to directly read external contract storage. + +## Motivation + +The gas cost when reading from registry style contract such as ERC-20s, ENS and other data contracts is very high, because they incur cross contract call cost, cost for ABI encoding, decoding and dispatching and finally loading the data. In many cases the underlying storage that is being queried is though just a simple mapping. In these cases a new SLOAD2 call directly accessing the mapping in storage could not only **reduce the gas cost** of the interaction more than 10x, but also it would make the gas cost **predictable** for the reading contract. + +## Specification + +**Proposal** +A new EVM instruction `SLOAD2 (0x5c)` that works like `SLOAD (0x54)` with the same gas cost but has an additional parameter representing the contract that is to be read from. + +``` +SLOAD (0x5c) +``` + +**Example** + +An example assuming further Solidity changes for illustration: + +```solidity +interface MemberList { + public fixed(@5) mapping(address => bool) members; +} +``` + +And a corresponding contract function that uses this member list. Similarly tokens or other registries could be implemented. + +```solidity +function membersOnly(address list, address member) { + MemberList ml = MemberList(list); + if (ml.members[client] == false) revert("Nonmember!"); +} +``` + +The call `ml.members[client]` here could let the Solidity compiler generate the normal map access logic but using the new `SLOAD2
` instructions to read from the `ml` contract storage instead of the local contract storage. + +## Backwards Compatibility +This change is fully backwards compatible since it adds a new instruction. + +## Test Cases + +Not started yet. + +## Implementation + +Not started yet. + +## Copyright +Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).