Add LibTransient

.gas-snapshot

@@ -1,3 +1,5 @@
+LibTransientTest:testTransientSetAndGet(bytes32,uint256) (runs: 256, μ: 700, ~: 700)
+LibTransientTest:test__codesize() (gas: 1779)
 ReentrancyGuardTest:testRecursiveDirectUnguardedCall() (gas: 32203)
 ReentrancyGuardTest:testRecursiveIndirectUnguardedCall() (gas: 45600)
 ReentrancyGuardTest:testRevertGuardLocked() (gas: 31984)

README.md

@@ -27,6 +27,7 @@ The Solidity smart contracts are located in the `src` directory.
 
 ```ml
 utils
+├─ LibTransient — "Transient storage get/set helper"
 └─ ReentrancyGuard — "Reentrancy guard mixin"
 ```
 

src/utils/LibTransient.sol

@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.24;
+
+/// @notice Transient storage get/set helper.
+/// @author Soledge (https://github.com/vectorized/soledge/blob/main/src/utils/LibTransient.sol)
+library LibTransient {
+    /// @dev Returns the value at `tSlot` in transient storage.
+    function get(bytes32 tSlot) internal view returns (bytes32 result) {
+        /// @solidity memory-safe-assembly
+        assembly {
+            result := tload(tSlot)
+        }
+    }
+
+    /// @dev Sets the value at `tSlot` in transient storage to `value`.
+    function set(bytes32 tSlot, bytes32 value) internal {
+        /// @solidity memory-safe-assembly
+        assembly {
+            tstore(tSlot, value)
+        }
+    }
+}

test/LibTransient.t.sol

@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.24;
+
+import "./utils/SoladyTest.sol";
+import {LibTransient} from "../src/utils/LibTransient.sol";
+
+contract LibTransientTest is SoladyTest {
+    function testTransientSetAndGet(bytes32 s, uint256 i) public {
+        unchecked {
+            assertEq(LibTransient.get(s), bytes32(0));
+            LibTransient.set(s, bytes32(i));
+            assertEq(LibTransient.get(s), bytes32(i));
+        }
+    }
+}