Support memory arrays in MerkleTree multiproof (#3493)

contracts/utils/cryptography/MerkleProof.sol

@@ -81,12 +81,26 @@ library MerkleProof {
      * _Available since v4.7._
      */
     function multiProofVerify(
+        bytes32[] memory proof,
+        bool[] memory proofFlags,
+        bytes32 root,
+        bytes32[] memory leaves
+    ) internal pure returns (bool) {
+        return processMultiProof(proof, proofFlags, leaves) == root;
+    }
+
+    /**
+     * @dev Calldata version of {multiProofVerify}
+     *
+     * _Available since v4.7._
+     */
+    function multiProofVerifyCalldata(
         bytes32[] calldata proof,
         bool[] calldata proofFlags,
         bytes32 root,
-        bytes32[] calldata leaves
+        bytes32[] memory leaves
     ) internal pure returns (bool) {
-        return processMultiProof(proof, proofFlags, leaves) == root;
+        return processMultiProofCalldata(proof, proofFlags, leaves) == root;
     }
 
     /**
@@ -97,9 +111,55 @@ library MerkleProof {
      * _Available since v4.7._
      */
     function processMultiProof(
+        bytes32[] memory proof,
+        bool[] memory proofFlags,
+        bytes32[] memory leaves
+    ) internal pure returns (bytes32 merkleRoot) {
+        // This function rebuild the root hash by traversing the tree up from the leaves. The root is rebuilt by
+        // consuming and producing values on a queue. The queue starts with the `leaves` array, then goes onto the
+        // `hashes` array. At the end of the process, the last hash in the `hashes` array should contain the root of
+        // the merkle tree.
+        uint256 leavesLen = leaves.length;
+        uint256 totalHashes = proofFlags.length;
+
+        // Check proof validity.
+        require(leavesLen + proof.length - 1 == totalHashes, "MerkleProof: invalid multiproof");
+
+        // The xxxPos values are "pointers" to the next value to consume in each array. All accesses are done using
+        // `xxx[xxxPos++]`, which return the current value and increment the pointer, thus mimicking a queue's "pop".
+        bytes32[] memory hashes = new bytes32[](totalHashes);
+        uint256 leafPos = 0;
+        uint256 hashPos = 0;
+        uint256 proofPos = 0;
+        // At each step, we compute the next hash using two values:
+        // - a value from the "main queue". If not all leaves have been consumed, we get the next leaf, otherwise we
+        //   get the next hash.
+        // - depending on the flag, either another value for the "main queue" (merging branches) or an element from the
+        //   `proof` array.
+        for (uint256 i = 0; i < totalHashes; i++) {
+            bytes32 a = leafPos < leavesLen ? leaves[leafPos++] : hashes[hashPos++];
+            bytes32 b = proofFlags[i] ? leafPos < leavesLen ? leaves[leafPos++] : hashes[hashPos++] : proof[proofPos++];
+            hashes[i] = _hashPair(a, b);
+        }
+
+        if (totalHashes > 0) {
+            return hashes[totalHashes - 1];
+        } else if (leavesLen > 0) {
+            return leaves[0];
+        } else {
+            return proof[0];
+        }
+    }
+
+    /**
+     * @dev Calldata version of {processMultiProof}
+     *
+     * _Available since v4.7._
+     */
+    function processMultiProofCalldata(
         bytes32[] calldata proof,
         bool[] calldata proofFlags,
-        bytes32[] calldata leaves
+        bytes32[] memory leaves
     ) internal pure returns (bytes32 merkleRoot) {
         // This function rebuild the root hash by traversing the tree up from the leaves. The root is rebuilt by
         // consuming and producing values on a queue. The queue starts with the `leaves` array, then goes onto the