feat: Get Call Data functionality

src/precompiles/native-tokens/INativeTokens.sol

@@ -7,9 +7,7 @@ pragma solidity >=0.8.12;
 interface INativeTokens {
     function balanceOf(address account, uint256 tokenID) external returns (uint256);
     function burn(uint256 subID, address holder, uint256 amount) external;
-
-    // TODO: implement `callvalues()`
-
+    function getCallValues() external returns (uint256[] memory, uint256[] memory);
     function mint(uint256 subID, address recipient, uint256 amount) external;
     function transfer(address to, uint256 tokenID, uint256 amount) external;
     function transferAndCall(

src/precompiles/native-tokens/NativeTokens.sol

@@ -30,6 +30,31 @@ library NativeTokens {
         return abi.decode(returnData, (uint256));
     }
 
+    /// @notice Returns the token ids and amounts of the Native Tokens transferred in the context
+    /// of the current contract call.
+    ///
+    /// Requirements:
+    /// - The caller of this function must be a contract.
+    ///
+    /// @return tokenIDs The IDs of the transferred Native Tokens.
+    /// @return amounts The amounts of the transferred Native Tokens.
+    function getCallValues(address notUsed) internal returns (uint256[] memory, uint256[] memory) {
+        notUsed;
+        // ABI encode the input parameters.
+        bytes memory callData = abi.encodeCall(INativeTokens.getCallValues, ());
+
+        // Call the precompile.
+        (bool success, bytes memory returnData) = PRECOMPILE_NATIVE_TOKENS.delegatecall(callData);
+
+        // This is an unexpected error since the VM should have panicked if the call failed.
+        if (!success) {
+            revert StdLib_UnknownError("NativeTokens: getCallValues failed");
+        }
+
+        // Decode the return data.
+        return abi.decode(returnData, (uint256[], uint256[]));
+    }
+
     /*//////////////////////////////////////////////////////////////////////////
                          USER-FACING NON-CONSTANT FUNCTIONS
     //////////////////////////////////////////////////////////////////////////*/

src/standards/srf-20/NaiveTokenTransferrerMock.sol

@@ -11,6 +11,12 @@ contract NaiveTokenTransferrerMock {
         return account.balanceOf(tokenID);
     }
 
+    function getCallValues() external payable returns (uint256[] memory, uint256[] memory) {
+        // TODO: make the getCallValues() function callable directly from the Precompile, w/o having to call it on an
+        // address
+        return msg.sender.getCallValues();
+    }
+
     function transfer(address to, uint256 tokenID, uint256 amount) external {
         to.transfer(tokenID, amount);
     }