Add support for new seal_random API (#734)

* [env] [lang] Add support for new `seal_random` API

* Don't support old seal_random

crates/env/src/api.rs

@@ -483,7 +483,8 @@ where
     })
 }
 
-/// Returns a random hash seed.
+/// Returns a random hash seed and the block number since which it was determinable
+/// by chain observers.
 ///
 /// # Note
 ///
@@ -493,7 +494,15 @@ where
 /// # Errors
 ///
 /// If the returned value cannot be properly decoded.
-pub fn random<T>(subject: &[u8]) -> Result<T::Hash>
+///
+/// # Important
+///
+/// The returned seed should only be used to distinguish commitments made before
+/// the returned block number. If the block number is too early (i.e. commitments were
+/// made afterwards), then ensure no further commitments may be made and repeatedly
+/// call this on later blocks until the block number returned is later than the latest
+/// commitment.
+pub fn random<T>(subject: &[u8]) -> Result<(T::Hash, T::BlockNumber)>
 where
     T: Environment,
 {

crates/env/src/backend.rs

@@ -339,7 +339,7 @@ pub trait TypedEnvBackend: EnvBackend {
     /// # Note
     ///
     /// For more details visit: [`random`][`crate::random`]
-    fn random<T>(&mut self, subject: &[u8]) -> Result<T::Hash>
+    fn random<T>(&mut self, subject: &[u8]) -> Result<(T::Hash, T::BlockNumber)>
     where
         T: Environment;
 }

crates/env/src/engine/off_chain/impls.rs

@@ -449,13 +449,11 @@ impl TypedEnvBackend for EnvInstance {
         self.transfer_impl::<T>(&destination, value)
     }
 
-    fn random<T>(&mut self, subject: &[u8]) -> Result<T::Hash>
+    fn random<T>(&mut self, subject: &[u8]) -> Result<(T::Hash, T::BlockNumber)>
     where
         T: Environment,
     {
-        self.current_block()
-            .expect(UNITIALIZED_EXEC_CONTEXT)
-            .random::<T>(subject)
-            .map_err(Into::into)
+        let block = self.current_block().expect(UNITIALIZED_EXEC_CONTEXT);
+        Ok((block.random::<T>(subject)?, block.number::<T>()?))
     }
 }

crates/env/src/engine/on_chain/ext.rs

@@ -308,12 +308,6 @@ mod sys {
 
         pub fn seal_set_rent_allowance(value_ptr: Ptr32<[u8]>, value_len: u32);
 
-        pub fn seal_random(
-            subject_ptr: Ptr32<[u8]>,
-            subject_len: u32,
-            output_ptr: Ptr32Mut<[u8]>,
-            output_len_ptr: Ptr32Mut<u32>,
-        );
         pub fn seal_println(str_ptr: Ptr32<[u8]>, str_len: u32);
 
         pub fn seal_hash_keccak_256(
@@ -337,6 +331,16 @@ mod sys {
             output_ptr: Ptr32Mut<[u8]>,
         );
     }
+
+    #[link(wasm_import_module = "seal1")]
+    extern "C" {
+        pub fn seal_random(
+            subject_ptr: Ptr32<[u8]>,
+            subject_len: u32,
+            output_ptr: Ptr32Mut<[u8]>,
+            output_len_ptr: Ptr32Mut<u32>,
+        );
+    }
 }
 
 fn extract_from_slice(output: &mut &mut [u8], new_len: usize) {

crates/env/src/engine/on_chain/impls.rs

@@ -460,7 +460,7 @@ impl TypedEnvBackend for EnvInstance {
         scale::Decode::decode(&mut &output[..]).map_err(Into::into)
     }
 
-    fn random<T>(&mut self, subject: &[u8]) -> Result<T::Hash>
+    fn random<T>(&mut self, subject: &[u8]) -> Result<(T::Hash, T::BlockNumber)>
     where
         T: Environment,
     {

crates/lang/src/env_access.rs

@@ -303,7 +303,7 @@ where
     /// # Note
     ///
     /// For more details visit: [`ink_env::random`]
-    pub fn random(self, subject: &[u8]) -> T::Hash {
+    pub fn random(self, subject: &[u8]) -> (T::Hash, T::BlockNumber) {
         ink_env::random::<T>(subject).expect("couldn't decode randomized hash")
     }