Optimise permit hashing (#260)

* permit hash in assembly * fuzz test
Uniswap · Aug 4, 2024 · d65f158 · d65f158
1 parent 86b5ea3
commit d65f158
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Showing 5 changed files with 24 additions and 5 deletions.
diff --git a/.forge-snapshots/PositionManager_permit.snap b/.forge-snapshots/PositionManager_permit.snap
@@ -1 +1 @@
-79585
+79486
diff --git a/.forge-snapshots/PositionManager_permit_secondPosition.snap b/.forge-snapshots/PositionManager_permit_secondPosition.snap
@@ -1 +1 @@
-62497
+62398
diff --git a/.forge-snapshots/PositionManager_permit_twice.snap b/.forge-snapshots/PositionManager_permit_twice.snap
@@ -1 +1 @@
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+45298
diff --git a/src/libraries/ERC721PermitHash.sol b/src/libraries/ERC721PermitHash.sol
@@ -5,7 +5,20 @@ library ERC721PermitHashLibrary {
     /// @dev Value is equal to keccak256("Permit(address spender,uint256 tokenId,uint256 nonce,uint256 deadline)");
     bytes32 constant PERMIT_TYPEHASH = 0x49ecf333e5b8c95c40fdafc95c1ad136e8914a8fb55e9dc8bb01eaa83a2df9ad;
 
-    function hash(address spender, uint256 tokenId, uint256 nonce, uint256 deadline) internal pure returns (bytes32) {
-        return keccak256(abi.encode(PERMIT_TYPEHASH, spender, tokenId, nonce, deadline));
+    function hash(address spender, uint256 tokenId, uint256 nonce, uint256 deadline)
+        internal
+        pure
+        returns (bytes32 digest)
+    {
+        // equivalent to: keccak256(abi.encode(PERMIT_TYPEHASH, spender, tokenId, nonce, deadline));
+        assembly ("memory-safe") {
+            let fmp := mload(0x40)
+            mstore(fmp, PERMIT_TYPEHASH)
+            mstore(add(fmp, 0x20), spender)
+            mstore(add(fmp, 0x40), tokenId)
+            mstore(add(fmp, 0x60), nonce)
+            mstore(add(fmp, 0x80), deadline)
+            digest := keccak256(fmp, 0xa0)
+        }
     }
 }
diff --git a/test/ERC721Permit.t.sol b/test/ERC721Permit.t.sol
@@ -67,6 +67,12 @@ contract ERC721PermitTest is Test {
         );
     }
 
+    function test_fuzz_permitHash(address spender, uint256 tokenId, uint256 nonce, uint256 deadline) public view {
+        bytes32 expectedHash =
+            keccak256(abi.encode(ERC721PermitHashLibrary.PERMIT_TYPEHASH, spender, tokenId, nonce, deadline));
+        assertEq(expectedHash, ERC721PermitHashLibrary.hash(spender, tokenId, nonce, deadline));
+    }
+
     function test_domainSeparator() public view {
         assertEq(
             IERC721Permit(address(erc721Permit)).DOMAIN_SEPARATOR(),