New gas_evaporate API function

packages/std/src/imports.rs

@@ -81,6 +81,8 @@ extern "C" {
     fn secp256k1_sign(messages_ptr: u32, private_key_ptr: u32) -> u64;
 
     fn ed25519_sign(messages_ptr: u32, private_key_ptr: u32) -> u64;
+
+    fn gas_evaporate(evaporate: u32) -> u32;
 }
 
 /// A stateless convenience wrapper around database imports provided by the VM.
@@ -407,6 +409,18 @@ impl Api for ExternalApi {
             error_code => Err(SigningError::unknown_err(error_code)),
         }
     }
+
+    fn gas_evaporate(&self, evaporate: u32) -> StdResult<()> {
+        let result = unsafe { gas_evaporate(evaporate) };
+        if result != 0 {
+            return Err(StdError::generic_err(format!(
+                "gas_evaporate errored: {}",
+                result
+            )));
+        }
+
+        Ok(())
+    }
 }
 
 /// Takes a pointer to a Region and reads the data into a String.

packages/std/src/testing/mock.rs

@@ -227,6 +227,10 @@ impl Api for MockApi {
     fn ed25519_sign(&self, message: &[u8], private_key: &[u8]) -> Result<Vec<u8>, SigningError> {
         Ok(cosmwasm_crypto::ed25519_sign(message, private_key)?)
     }
+
+    fn gas_evaporate(&self, _evaporate: u32) -> StdResult<()> {
+        Ok(())
+    }
 }
 
 /// Returns a default enviroment with height, time, chain_id, and contract address

packages/std/src/traits.rs

@@ -212,6 +212,13 @@ pub trait Api {
     /// - message: Arbitrary message.
     /// - private key: Raw ED25519 private key (32 bytes)
     fn ed25519_sign(&self, message: &[u8], private_key: &[u8]) -> Result<Vec<u8>, SigningError>;
+
+    /// Gas evaporation.
+    /// 
+    /// This function will burn a evaporate a precise and reproducible amount of sdk gas.
+    /// 
+    ///  - evaporate: Amount of SDK gas to evaporate.
+    fn gas_evaporate(&self, evaporate: u32) -> StdResult<()>;
 }
 
 /// A short-hand alias for the two-level query result (1. accessing the contract, 2. executing query in the contract)