feat(erc2330): add erc2330 alternative

Author: Rubilmax

src/ERC2330.sol

@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+pragma solidity ^0.8.0;
+
+import {IERC2330} from "src/interfaces/IERC2330.sol";
+
+/// @dev Gas-optimized extsload getters to allow anyone to read storage from this contract.
+///      Enables the benefit of https://eips.ethereum.org/EIPS/eip-2330 without requiring changes to the execution layer.
+contract ERC2330 is IERC2330 {
+    /* EXTERNAL */
+
+    /// @inheritdoc IERC2330
+    function extsload(bytes32 slot) external view returns (bytes32 value) {
+        /// @solidity memory-safe-assembly
+        assembly {
+            value := sload(slot)
+        }
+    }
+
+    /// @inheritdoc IERC2330
+    function extsload(bytes32 startSlot, uint256 nSlots) external view returns (bytes memory value) {
+        value = new bytes(32 * nSlots);
+
+        /// @solidity memory-safe-assembly
+        assembly {
+            for { let i := 0 } lt(i, nSlots) { i := add(i, 1) } {
+                mstore(add(value, mul(add(i, 1), 32)), sload(add(startSlot, i)))
+            }
+        }
+    }
+}

src/interfaces/IERC2330.sol

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+// SPDX-License-Identifier: AGPL-3.0-only
+pragma solidity ^0.8.0;
+
+interface IERC2330 {
+    /* FUNCTIONS */
+
+    /// @dev Returns the 32-bytes value stored in this contract, at the given storage slot.
+    function extsload(bytes32 slot) external view returns (bytes32 value);
+
+    /// @dev Returns the `nSlots` 32-bytes values stored in this contract, starting from the given start slot.
+    function extsload(bytes32 startSlot, uint256 nSlots) external view returns (bytes memory value);
+}

test/TestERC2330.sol

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+// SPDX-License-Identifier: AGPL-3.0-only
+pragma solidity ^0.8.0;
+
+import {IERC2330} from "src/interfaces/IERC2330.sol";
+
+import {ERC2330Mock} from "test/mocks/ERC2330Mock.sol";
+
+import "forge-std/Test.sol";
+
+contract TestERC2330 is Test {
+    ERC2330Mock mock;
+
+    function setUp() public {
+        mock = new ERC2330Mock();
+    }
+
+    function testExtsload() public {
+        assertEq(
+            mock.extsload(0x0000000000000000000000000000000000000000000000000000000000000000),
+            0x0000000000000000000000000000000100000000000000000000000000000001
+        );
+        assertEq(
+            mock.extsload(0x0000000000000000000000000000000000000000000000000000000000000001),
+            0x0000000000000000000000000000000000000000000000000000000000000002
+        );
+    }
+
+    function testExtsloadMultiple() public {
+        (bytes32 var1, bytes32 var2) = abi.decode(
+            mock.extsload(0x0000000000000000000000000000000000000000000000000000000000000000, 2), (bytes32, bytes32)
+        );
+
+        assertEq(var1, 0x0000000000000000000000000000000100000000000000000000000000000001);
+        assertEq(var2, 0x0000000000000000000000000000000000000000000000000000000000000002);
+    }
+}

test/mocks/ERC2330Mock.sol

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+// SPDX-License-Identifier: AGPL-3.0-only
+pragma solidity ^0.8.0;
+
+import {ERC2330} from "src/ERC2330.sol";
+
+contract ERC2330Mock is ERC2330 {
+    uint128 private _var11;
+    uint128 private _var12;
+    uint256 private _var2;
+
+    constructor() {
+        _var11 = 1;
+        _var12 = 1;
+        _var2 = 2;
+    }
+}