uplink: metadata support for free hint and price hint

piecrust-uplink/CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- Add support for metadata elements: free limit and free price hint [#357]
 - Add contract charge setting method [#353] 
 - Add contract allowance setting method and a corresponding passing mechanism [#350] 
 
@@ -169,6 +170,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - First `piecrust-uplink` release
 
 <!-- ISSUES -->
+[#357]: https://github.com/dusk-network/piecrust/issues/357
 [#353]: https://github.com/dusk-network/piecrust/issues/353
 [#350]: https://github.com/dusk-network/piecrust/issues/350
 [#324]: https://github.com/dusk-network/piecrust/issues/324

piecrust-uplink/src/abi/state.rs

@@ -76,6 +76,8 @@ mod ext {
         pub fn limit() -> u64;
         pub fn spent() -> u64;
         pub fn owner(contract_id: *const u8) -> i32;
+        pub fn free_limit(contract_id: *const u8) -> i32;
+        pub fn free_price_hint(contract_id: *const u8) -> i32;
         pub fn self_id();
     }
 }
@@ -292,6 +294,37 @@ pub fn owner<const N: usize>(contract: ContractId) -> Option<[u8; N]> {
     }
 }
 
+/// Returns given contract's free limit, if the contract exists and if it
+/// has a free limit set.
+pub fn free_limit(contract: ContractId) -> Option<u64> {
+    let contract_id_ptr = contract.as_bytes().as_ptr();
+    unsafe {
+        match ext::free_limit(contract_id_ptr) as usize {
+            0 => None,
+            arg_pos => with_arg_buf(|buf, _| {
+                let ret = archived_root::<Option<u64>>(&buf[..arg_pos]);
+                ret.deserialize(&mut Infallible).expect("Infallible")
+            }),
+        }
+    }
+}
+
+/// Returns given contract's free gas price hint, if the contract exists and
+/// if it has a free price hint set.
+pub fn free_price_hint(contract: ContractId) -> Option<(u64, u64)> {
+    let contract_id_ptr = contract.as_bytes().as_ptr();
+
+    unsafe {
+        match ext::free_price_hint(contract_id_ptr) as usize {
+            0 => None,
+            arg_pos => with_arg_buf(|buf, _| {
+                let ret = archived_root::<Option<(u64, u64)>>(&buf[..arg_pos]);
+                ret.deserialize(&mut Infallible).expect("Infallible")
+            }),
+        }
+    }
+}
+
 /// Returns the current contract's owner.
 pub fn self_owner<const N: usize>() -> [u8; N] {
     unsafe { ext::owner(ptr::null()) };