feat!: decouple wasmer from Marine, replace it with generic backend interface (#219)

crates/wasm-backend-traits/src/instance.rs

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2023 Fluence Labs Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+use crate::AsContextMut;
+use crate::Export;
+use crate::ResolveResult;
+use crate::WasmBackend;
+
+/// A handle to an instantiated Wasm module. Cloning is cheap.
+pub trait Instance<WB: WasmBackend>: Clone {
+    /// Returns an `Iterator` to all exports of this instance.
+    fn export_iter<'a>(
+        &'a self,
+        store: <WB as WasmBackend>::ContextMut<'a>,
+    ) -> Box<dyn Iterator<Item = (&'a str, Export<WB>)> + 'a>;
+
+    /// Returns nth exported memory, None if there is no nth memory.
+    /// No guaranties is known for memory order, but almost always a module has only one memory,
+    /// hence the only valid value for `memory_index` is 0.
+    fn get_nth_memory(
+        &self,
+        store: &mut impl AsContextMut<WB>,
+        memory_index: u32, // TODO: refactor memory indexing with enums
+    ) -> Option<<WB as WasmBackend>::Memory>;
+
+    /// Returns a memory export with given name.
+    /// # Errors:
+    ///     Returns an error if there is no export with such name, or it is not a memory.
+    fn get_memory(
+        &self,
+        store: &mut impl AsContextMut<WB>,
+        memory_name: &str,
+    ) -> ResolveResult<<WB as WasmBackend>::Memory>;
+
+    /// Returns an exported function with the given name.
+    /// # Errors:
+    ///     Returns an error if there is no export with such name, or it is not a function.
+    fn get_function(
+        &self,
+        store: &mut impl AsContextMut<WB>,
+        name: &str,
+    ) -> ResolveResult<<WB as WasmBackend>::Function>;
+}