Add Memory utility library (#5189)

Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>
Co-authored-by: Arr00 <13561405+arr00@users.noreply.github.com>

contracts/utils/Memory.sol

@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.20;
+
+/**
+ * @dev Utilities to manipulate memory.
+ *
+ * Memory is a contiguous and dynamic byte array in which Solidity stores non-primitive types.
+ * This library provides functions to manipulate pointers to this dynamic array.
+ *
+ * WARNING: When manipulating memory, make sure to follow the Solidity documentation
+ * guidelines for https://docs.soliditylang.org/en/v0.8.20/assembly.html#memory-safety[Memory Safety].
+ */
+library Memory {
+    type Pointer is bytes32;
+
+    /// @dev Returns a `Pointer` to the current free `Pointer`.
+    function getFreeMemoryPointer() internal pure returns (Pointer ptr) {
+        assembly ("memory-safe") {
+            ptr := mload(0x40)
+        }
+    }
+
+    /**
+     * @dev Sets the free `Pointer` to a specific value.
+     *
+     * WARNING: Everything after the pointer may be overwritten.
+     **/
+    function setFreeMemoryPointer(Pointer ptr) internal pure {
+        assembly ("memory-safe") {
+            mstore(0x40, ptr)
+        }
+    }
+
+    /// @dev `Pointer` to `bytes32`. Expects a pointer to a properly ABI-encoded `bytes` object.
+    function asBytes32(Pointer ptr) internal pure returns (bytes32) {
+        return Pointer.unwrap(ptr);
+    }
+
+    /// @dev `bytes32` to `Pointer`. Expects a pointer to a properly ABI-encoded `bytes` object.
+    function asPointer(bytes32 value) internal pure returns (Pointer) {
+        return Pointer.wrap(value);
+    }
+}

contracts/utils/README.adoc

@@ -38,6 +38,7 @@ Miscellaneous contracts and libraries containing utility functions you can use t
  * {Panic}: A library to revert with https://docs.soliditylang.org/en/v0.8.20/control-structures.html#panic-via-assert-and-error-via-require[Solidity panic codes].
  * {Comparators}: A library that contains comparator functions to use with the {Heap} library.
  * {CAIP2}, {CAIP10}: Libraries for formatting and parsing CAIP-2 and CAIP-10 identifiers.
+ * {Memory}: A utility library to manipulate memory.
  * {InteroperableAddress}: Library for formatting and parsing ERC-7930 interoperable addresses.
  * {Blockhash}: A library for accessing historical block hashes beyond the standard 256 block limit utilizing EIP-2935's historical blockhash functionality.
  * {Time}: A library that provides helpers for manipulating time-related objects, including a `Delay` type.
@@ -135,6 +136,8 @@ Ethereum contracts have no native concept of an interface, so applications must
 
 {{CAIP10}}
 
+{{Memory}}
+
 {{InteroperableAddress}}
 
 {{Blockhash}}