Add Packing library (#4992)

Co-authored-by: ernestognw <ernestognw@gmail.com>

contracts/utils/Packing.sol

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.20;
+
+/**
+ * @dev Helper library packing and unpacking multiple values into bytes32
+ */
+library Packing {
+    type Uint128x2 is bytes32;
+
+    /// @dev Cast a bytes32 into a Uint128x2
+    function asUint128x2(bytes32 self) internal pure returns (Uint128x2) {
+        return Uint128x2.wrap(self);
+    }
+
+    /// @dev Cast a Uint128x2 into a bytes32
+    function asBytes32(Uint128x2 self) internal pure returns (bytes32) {
+        return Uint128x2.unwrap(self);
+    }
+
+    /// @dev Pack two uint128 into a Uint128x2
+    function pack(uint128 first128, uint128 second128) internal pure returns (Uint128x2) {
+        return Uint128x2.wrap(bytes32(bytes16(first128)) | bytes32(uint256(second128)));
+    }
+
+    /// @dev Split a Uint128x2 into two uint128
+    function split(Uint128x2 self) internal pure returns (uint128, uint128) {
+        return (first(self), second(self));
+    }
+
+    /// @dev Get the first element of a Uint128x2 counting from higher to lower bytes
+    function first(Uint128x2 self) internal pure returns (uint128) {
+        return uint128(bytes16(Uint128x2.unwrap(self)));
+    }
+
+    /// @dev Get the second element of a Uint128x2 counting from higher to lower bytes
+    function second(Uint128x2 self) internal pure returns (uint128) {
+        return uint128(uint256(Uint128x2.unwrap(self)));
+    }
+}

contracts/utils/README.adoc

@@ -33,6 +33,7 @@ Miscellaneous contracts and libraries containing utility functions you can use t
  * {StorageSlot}: Methods for accessing specific storage slots formatted as common primitive types. Also include primitives for reading from and writing to transient storage (only value types are currently supported).
  * {Multicall}: Abstract contract with an utility to allow batching together multiple calls in a single transaction. Useful for allowing EOAs to perform multiple operations at once.
  * {Context}: An utility for abstracting the sender and calldata in the current execution context.
+ * {Packing}: A library for packing and unpacking multiple values into bytes32
  * {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].
 
 [NOTE]
@@ -120,4 +121,6 @@ Ethereum contracts have no native concept of an interface, so applications must
 
 {{Context}}
 
+{{Packing}}
+
 {{Panic}}