Add string and bytes support to the StorageSlots library (#4008)

Co-authored-by: Francisco <frangio.1@gmail.com>

contracts/mocks/StorageSlotMock.sol

@@ -5,7 +5,7 @@ pragma solidity ^0.8.0;
 import "../utils/StorageSlot.sol";
 
 contract StorageSlotMock {
-    using StorageSlot for bytes32;
+    using StorageSlot for *;
 
     function setBoolean(bytes32 slot, bool value) public {
         slot.getBooleanSlot().value = value;
@@ -38,4 +38,40 @@ contract StorageSlotMock {
     function getUint256(bytes32 slot) public view returns (uint256) {
         return slot.getUint256Slot().value;
     }
+
+    mapping(uint256 => string) public stringMap;
+
+    function setString(bytes32 slot, string calldata value) public {
+        slot.getStringSlot().value = value;
+    }
+
+    function setStringStorage(uint256 key, string calldata value) public {
+        stringMap[key].getStringSlot().value = value;
+    }
+
+    function getString(bytes32 slot) public view returns (string memory) {
+        return slot.getStringSlot().value;
+    }
+
+    function getStringStorage(uint256 key) public view returns (string memory) {
+        return stringMap[key].getStringSlot().value;
+    }
+
+    mapping(uint256 => bytes) public bytesMap;
+
+    function setBytes(bytes32 slot, bytes calldata value) public {
+        slot.getBytesSlot().value = value;
+    }
+
+    function setBytesStorage(uint256 key, bytes calldata value) public {
+        bytesMap[key].getBytesSlot().value = value;
+    }
+
+    function getBytes(bytes32 slot) public view returns (bytes memory) {
+        return slot.getBytesSlot().value;
+    }
+
+    function getBytesStorage(uint256 key) public view returns (bytes memory) {
+        return bytesMap[key].getBytesSlot().value;
+    }
 }

contracts/utils/StorageSlot.sol

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: MIT
 // OpenZeppelin Contracts (last updated v4.7.0) (utils/StorageSlot.sol)
+// This file was procedurally generated from scripts/generate/templates/StorageSlot.js.
 
 pragma solidity ^0.8.0;
 
@@ -27,7 +28,8 @@ pragma solidity ^0.8.0;
  * }
  * ```
  *
- * _Available since v4.1 for `address`, `bool`, `bytes32`, and `uint256`._
+ * _Available since v4.1 for `address`, `bool`, `bytes32`, `uint256`._
+ * _Available since v4.9 for `string`, `bytes`._
  */
 library StorageSlot {
     struct AddressSlot {
@@ -46,6 +48,14 @@ library StorageSlot {
         uint256 value;
     }
 
+    struct StringSlot {
+        string value;
+    }
+
+    struct BytesSlot {
+        bytes value;
+    }
+
     /**
      * @dev Returns an `AddressSlot` with member `value` located at `slot`.
      */
@@ -85,4 +95,44 @@ library StorageSlot {
             r.slot := slot
         }
     }
+
+    /**
+     * @dev Returns an `StringSlot` with member `value` located at `slot`.
+     */
+    function getStringSlot(bytes32 slot) internal pure returns (StringSlot storage r) {
+        /// @solidity memory-safe-assembly
+        assembly {
+            r.slot := slot
+        }
+    }
+
+    /**
+     * @dev Returns an `StringSlot` representation of the string storage pointer `store`.
+     */
+    function getStringSlot(string storage store) internal pure returns (StringSlot storage r) {
+        /// @solidity memory-safe-assembly
+        assembly {
+            r.slot := store.slot
+        }
+    }
+
+    /**
+     * @dev Returns an `BytesSlot` with member `value` located at `slot`.
+     */
+    function getBytesSlot(bytes32 slot) internal pure returns (BytesSlot storage r) {
+        /// @solidity memory-safe-assembly
+        assembly {
+            r.slot := slot
+        }
+    }
+
+    /**
+     * @dev Returns an `BytesSlot` representation of the bytes storage pointer `store`.
+     */
+    function getBytesSlot(bytes storage store) internal pure returns (BytesSlot storage r) {
+        /// @solidity memory-safe-assembly
+        assembly {
+            r.slot := store.slot
+        }
+    }
 }