Use Externals mechanism instead of HostState

examples/interpret.rs

@@ -3,7 +3,7 @@
 extern crate parity_wasm;
 
 use std::env::args;
-use parity_wasm::interpreter::{ModuleInstance, HostState};
+use parity_wasm::interpreter::{ModuleInstance, EmptyExternals};
 
 fn main() {
     let args: Vec<_> = args().collect();
@@ -23,12 +23,12 @@ fn main() {
      // - "main" module doesn't import native module(s) this is why we don't need to provide external native modules here
      // This test shows how to implement native module https://github.com/NikVolf/parity-wasm/blob/master/src/interpreter/tests/basics.rs#L197
     let main = ModuleInstance::new(&module)
-        .run_start(&mut HostState::default())
+        .run_start(&mut EmptyExternals)
         .expect("Failed to initialize module");
 
     // The argument should be parsable as a valid integer
     let argument: i32 = args[2].parse().expect("Integer argument required");
 
     // "_call" export of function to be executed with an i32 argument and prints the result of execution
-    println!("Result: {:?}", main.invoke_export("_call", &[parity_wasm::RuntimeValue::I32(argument)], &mut HostState::default()));
+    println!("Result: {:?}", main.invoke_export("_call", &[parity_wasm::RuntimeValue::I32(argument)], &mut EmptyExternals));
 }

examples/invoke.rs

@@ -4,7 +4,7 @@ use std::env::args;
 
 use parity_wasm::RuntimeValue;
 use parity_wasm::elements::{Internal, External, Type, FunctionType, ValueType};
-use parity_wasm::interpreter::{ModuleInstance, HostState};
+use parity_wasm::interpreter::{ModuleInstance, EmptyExternals};
 
 
 fn main() {
@@ -75,8 +75,8 @@ fn main() {
     // - "main" module doesn't import native module(s) this is why we don't need to provide external native modules here
     // This test shows how to implement native module https://github.com/NikVolf/parity-wasm/blob/master/src/interpreter/tests/basics.rs#L197
     let main = ModuleInstance::new(&module)
-        .run_start(&mut HostState::default())
+        .run_start(&mut EmptyExternals)
         .expect("Failed to initialize module");
 
-    println!("Result: {:?}", main.invoke_export(func_name, &args, &mut HostState::default()).expect(""));
+    println!("Result: {:?}", main.invoke_export(func_name, &args, &mut EmptyExternals).expect(""));
 }

examples/tictactoe.rs

@@ -3,10 +3,11 @@ extern crate parity_wasm;
 use std::env;
 use std::fmt;
 use std::rc::Rc;
-use parity_wasm::elements::Module;
+use parity_wasm::elements::{Module, FunctionType, ValueType, TableType, GlobalType, MemoryType};
 use parity_wasm::interpreter::{
-	Error as InterpreterError, HostModule, HostModuleBuilder,
-	ModuleInstance, UserError, HostState, StateKey
+	Error as InterpreterError, ModuleInstance, UserError,
+	HostFuncIndex, Externals, RuntimeValue, GlobalInstance, TableInstance, MemoryInstance,
+	TableRef, MemoryRef, GlobalRef, FuncRef, TryInto, ImportResolver, FuncInstance,
 };
 
 #[derive(Debug)]
@@ -139,54 +140,123 @@ struct Runtime<'a> {
 	game: &'a mut tictactoe::Game,
 }
 
-unsafe impl<'a> StateKey for Runtime<'a> {
-	type Static = Runtime<'static>;
+const SET_FUNC_INDEX: HostFuncIndex = 0;
+const GET_FUNC_INDEX: HostFuncIndex = 1;
+
+impl<'a> Externals for Runtime<'a> {
+	fn invoke_index(
+		&mut self,
+		index: HostFuncIndex,
+		args: &[RuntimeValue],
+	) -> Result<Option<RuntimeValue>, InterpreterError> {
+		match index {
+			SET_FUNC_INDEX => {
+				let idx: i32 = args[0].try_into().unwrap();
+				self.game.set(idx, self.player)?;
+				Ok(None)
+			}
+			GET_FUNC_INDEX => {
+				let idx: i32 = args[0].try_into().unwrap();
+				let val: i32 = tictactoe::Player::into_i32(self.game.get(idx)?);
+				Ok(Some(val.into()))
+			}
+			_ => panic!("unknown function index")
+		}
+	}
+
+	fn check_signature(&self, index: HostFuncIndex, sig: &FunctionType) -> bool {
+		match index {
+			SET_FUNC_INDEX => {
+				sig.params() == &[ValueType::I32] && sig.return_type() == None
+			}
+			GET_FUNC_INDEX => {
+				sig.params() == &[ValueType::I32] && sig.return_type() == Some(ValueType::I32)
+			}
+			_ => panic!("unknown function index")
+		}
+	}
+
+	fn memory_by_index(&self, _index: usize) -> &MemoryInstance {
+		panic!("host module doesn't export any memories")
+	}
+
+	fn table_by_index(&self, _index: usize) -> &TableInstance {
+		panic!("host module doesn't export any tables")
+	}
+
+	fn global_by_index(&self, _index: usize) -> &GlobalInstance {
+		panic!("host module doesn't export any globals")
+	}
+}
+
+struct RuntimeImportResolver;
+
+impl<'a> ImportResolver for RuntimeImportResolver {
+	fn resolve_func(
+		&self,
+		field_name: &str,
+		_func_type: &FunctionType,
+	) -> Result<FuncRef, InterpreterError> {
+		let func_ref = match field_name {
+			"set" => {
+				FuncInstance::alloc_host(FunctionType::new(vec![ValueType::I32], None), SET_FUNC_INDEX)
+			},
+			"get" => FuncInstance::alloc_host(FunctionType::new(vec![ValueType::I32], Some(ValueType::I32)), GET_FUNC_INDEX),
+			_ => return Err(
+				InterpreterError::Function(
+					format!("host module doesn't export function with name {}", field_name)
+				)
+			)
+		};
+		Ok(func_ref)
+	}
+
+	fn resolve_global(
+		&self,
+		_field_name: &str,
+		_global_type: &GlobalType,
+	) -> Result<GlobalRef, InterpreterError> {
+		Err(
+			InterpreterError::Global("host module doesn't export any globals".to_owned())
+		)
+	}
+
+	fn resolve_memory(
+		&self,
+		_field_name: &str,
+		_memory_type: &MemoryType,
+	) -> Result<MemoryRef, InterpreterError> {
+		Err(
+			InterpreterError::Global("host module doesn't export any memories".to_owned())
+		)
+	}
+
+	fn resolve_table(
+		&self,
+		_field_name: &str,
+		_table_type: &TableType,
+	) -> Result<TableRef, InterpreterError> {
+		Err(
+			InterpreterError::Global("host module doesn't export any tables".to_owned())
+		)
+	}
 }
 
 fn instantiate(
 	module: &Module,
-	env: &HostModule,
 ) -> Result<Rc<ModuleInstance>, Error> {
 	let instance = ModuleInstance::new(module)
-		.with_import("env", &*env)
-		.run_start(&mut HostState::default())?;
+		.with_import("env", &RuntimeImportResolver)
+		.assert_no_start()?;
 
 	Ok(instance)
 }
 
-fn env_host_module() -> HostModule {
-	HostModuleBuilder::new()
-		.with_func1(
-			"set",
-			|state: &mut HostState, idx: i32| -> Result<(), InterpreterError> {
-				state.with_mut(move |runtime: &mut Runtime| -> Result<(), InterpreterError> {
-					runtime.game.set(idx, runtime.player)?;
-					Ok(())
-				})
-			},
-		)
-		.with_func1(
-			"get",
-			|state: &mut HostState, idx: i32| -> Result<i32, InterpreterError> {
-				state.with(move |runtime: &Runtime| -> Result<i32, InterpreterError> {
-					let val: i32 = tictactoe::Player::into_i32(runtime.game.get(idx)?);
-					Ok(val)
-				})
-			},
-		)
-		.build()
-}
-
-fn play<'a>(
-	x_module: &Module,
-	o_module: &Module,
-	host_module: &HostModule,
-	game: &'a mut tictactoe::Game,
+fn play(
+	x_instance: Rc<ModuleInstance>,
+	o_instance: Rc<ModuleInstance>,
+	game: &mut tictactoe::Game,
 ) -> Result<tictactoe::GameResult, Error> {
-	// Instantiate modules of X and O players.
-	let x_instance = instantiate(x_module, host_module)?;
-	let o_instance = instantiate(o_module, host_module)?;
-
 	let mut turn_of = tictactoe::Player::X;
 	let game_result = loop {
 		let (instance, next_turn_of) = match turn_of {
@@ -199,11 +269,7 @@ fn play<'a>(
 				player: turn_of,
 				game: game,
 			};
-			{
-				let mut host_state = HostState::new();
-				host_state.insert::<Runtime>(&mut runtime);
-				let _ = instance.invoke_export("mk_turn", &[], &mut host_state)?;
-			}
+			let _ = instance.invoke_export("mk_turn", &[], &mut runtime)?;
 		}
 
 		match game.game_result() {
@@ -219,7 +285,6 @@ fn play<'a>(
 
 fn main() {
 	let mut game = tictactoe::Game::new();
-	let env_host_module = env_host_module();
 
 	let args: Vec<_> = env::args().collect();
 	if args.len() < 3 {
@@ -229,6 +294,10 @@ fn main() {
 	let x_module = parity_wasm::deserialize_file(&args[1]).expect("X player module to load");
 	let o_module = parity_wasm::deserialize_file(&args[2]).expect("Y player module to load");
 
-	let result = play(&x_module, &o_module, &env_host_module, &mut game);
+	// Instantiate modules of X and O players.
+	let x_instance = instantiate(&x_module).unwrap();
+	let o_instance = instantiate(&o_module).unwrap();
+
+	let result = play(x_instance, o_instance, &mut game);
 	println!("result = {:?}, game = {:#?}", result, game);
 }

src/interpreter/func.rs

@@ -4,10 +4,9 @@ use std::collections::HashMap;
 use std::borrow::Cow;
 use elements::{FunctionType, Local, Opcodes};
 use interpreter::{Error, ModuleInstance};
+use interpreter::host::{Externals, HostFuncIndex};
 use interpreter::runner::{prepare_function_args, FunctionContext, Interpreter};
-use interpreter::host::HostFunc;
 use interpreter::value::RuntimeValue;
-use interpreter::state::HostState;
 use common::stack::StackWithLimit;
 use common::{DEFAULT_FRAME_STACK_LIMIT, DEFAULT_VALUE_STACK_LIMIT};
 
@@ -29,8 +28,8 @@ pub enum FuncInstance {
 		body: Rc<FuncBody>,
 	},
 	Host {
-		func_type: Rc<FunctionType>,
-		host_func: Rc<HostFunc>,
+		func_type: FunctionType,
+		host_func: HostFuncIndex,
 	},
 }
 
@@ -57,7 +56,7 @@ impl fmt::Debug for FuncInstance {
 }
 
 impl FuncInstance {
-	pub fn alloc_internal(
+	pub(crate) fn alloc_internal(
 		module: Rc<ModuleInstance>,
 		func_type: Rc<FunctionType>,
 		body: FuncBody,
@@ -70,7 +69,7 @@ impl FuncInstance {
 		FuncRef(Rc::new(func))
 	}
 
-	pub fn alloc_host(func_type: Rc<FunctionType>, host_func: Rc<HostFunc>) -> FuncRef {
+	pub fn alloc_host(func_type: FunctionType, host_func: HostFuncIndex) -> FuncRef {
 		let func = FuncInstance::Host {
 			func_type,
 			host_func,
@@ -78,10 +77,10 @@ impl FuncInstance {
 		FuncRef(Rc::new(func))
 	}
 
-	pub fn func_type(&self) -> Rc<FunctionType> {
+	pub fn func_type(&self) -> &FunctionType {
 		match *self {
-			FuncInstance::Internal { ref func_type, .. } |
-			FuncInstance::Host { ref func_type, .. } => Rc::clone(func_type),
+			FuncInstance::Internal { ref func_type, .. } => func_type,
+			FuncInstance::Host { ref func_type, .. } => func_type,
 		}
 	}
 
@@ -92,14 +91,14 @@ impl FuncInstance {
 		}
 	}
 
-	pub fn invoke<'a, 'b: 'a>(
+	pub fn invoke<E: Externals>(
 		func: FuncRef,
 		args: Cow<[RuntimeValue]>,
-		state: &'a mut HostState<'b>,
+		externals: &mut E,
 	) -> Result<Option<RuntimeValue>, Error> {
 		enum InvokeKind<'a> {
 			Internal(FunctionContext),
-			Host(Rc<HostFunc>, &'a [RuntimeValue]),
+			Host(HostFuncIndex, &'a [RuntimeValue]),
 		}
 
 		let result = match *func {
@@ -117,16 +116,16 @@ impl FuncInstance {
 				InvokeKind::Internal(context)
 			}
 			FuncInstance::Host { ref host_func, .. } => {
-				InvokeKind::Host(Rc::clone(host_func), &*args)
+				InvokeKind::Host(*host_func, &*args)
 			}
 		};
 
 		match result {
 			InvokeKind::Internal(ctx) => {
-				let mut interpreter = Interpreter::new(state);
+				let mut interpreter = Interpreter::new(externals);
 				interpreter.run_function(ctx)
 			}
-			InvokeKind::Host(host_func, args) => host_func(state, args),
+			InvokeKind::Host(host_func, args) => externals.invoke_index(host_func, args),
 		}
 	}
 }

src/interpreter/host.rs

@@ -1,405 +1,50 @@
-use std::rc::Rc;
-use std::collections::HashMap;
-use std::collections::hash_map::Entry;
-use elements::{FunctionType, GlobalType, MemoryType, TableType, ValueType};
-use interpreter::module::{ExternVal, ModuleInstance};
-use interpreter::func::FuncRef;
-use interpreter::global::GlobalRef;
-use interpreter::memory::MemoryRef;
-use interpreter::table::TableRef;
-use interpreter::func::FuncInstance;
+use elements::FunctionType;
 use interpreter::global::GlobalInstance;
 use interpreter::memory::MemoryInstance;
 use interpreter::table::TableInstance;
-use interpreter::value::{RuntimeValue, TryInto};
+use interpreter::value::RuntimeValue;
 use interpreter::Error;
-use interpreter::ImportResolver;
-use interpreter::state::HostState;
 
-pub type HostFunc = Fn(&mut HostState, &[RuntimeValue])
-	-> Result<Option<RuntimeValue>, Error>;
+pub type HostFuncIndex = u32;
 
-pub struct HostModuleBuilder {
-	exports: HashMap<String, ExternVal>,
-}
-
-impl HostModuleBuilder {
-	pub fn new() -> Self {
-		HostModuleBuilder {
-			exports: HashMap::new(),
-		}
-	}
-
-	pub fn insert_func0<
-		Cl: Fn(&mut HostState) -> Result<Ret, Error> + 'static,
-		Ret: IntoReturnVal + 'static,
-		N: Into<String>,
-	>(
-		&mut self,
-		name: N,
-		f: Cl,
-	) {
-		let func_type = FunctionType::new(vec![], Ret::value_type());
-		let host_func = Rc::new(
-			move |state: &mut HostState, args: &[RuntimeValue]| -> Result<Option<RuntimeValue>, Error> {
-				assert!(args.len() == 0);
-				let result = f(state)?.into_return_val();
-				Ok(result)
-			},
-		);
-
-		let func = FuncInstance::alloc_host(Rc::new(func_type), host_func);
-		self.insert_func(name, func);
-	}
-
-	pub fn insert_func1<
-		Cl: Fn(&mut HostState, P1) -> Result<Ret, Error> + 'static,
-		Ret: IntoReturnVal + 'static,
-		P1: FromArg + 'static,
-		N: Into<String>,
-	>(
-		&mut self,
-		name: N,
-		f: Cl,
-	) {
-		let func_type = FunctionType::new(vec![P1::value_type()], Ret::value_type());
-		let host_func = Rc::new(
-			move |state: &mut HostState, args: &[RuntimeValue]| -> Result<Option<RuntimeValue>, Error> {
-				assert!(args.len() == 1);
-				let mut args = args.into_iter();
-				let result = f(
-					state,
-					P1::from_arg(args.next().unwrap())
-				)?.into_return_val();
-				Ok(result)
-			},
-		);
-
-		let func = FuncInstance::alloc_host(Rc::new(func_type), host_func);
-		self.insert_func(name, func);
-	}
-
-	pub fn insert_func2<
-		Cl: Fn(&mut HostState, P1, P2) -> Result<Ret, Error> + 'static,
-		Ret: IntoReturnVal + 'static,
-		P1: FromArg + 'static,
-		P2: FromArg + 'static,
-		N: Into<String>,
-	>(
-		&mut self,
-		name: N,
-		f: Cl,
-	) {
-		let func_type =
-			FunctionType::new(vec![P1::value_type(), P2::value_type()], Ret::value_type());
-		let host_func = Rc::new(
-			move |state: &mut HostState, args: &[RuntimeValue]| -> Result<Option<RuntimeValue>, Error> {
-				assert!(args.len() == 2);
-				let mut args = args.into_iter();
-				let result = f(
-					state,
-					P1::from_arg(args.next().unwrap()),
-					P2::from_arg(args.next().unwrap()),
-				)?.into_return_val();
-				Ok(result)
-			},
-		);
-
-		let func = FuncInstance::alloc_host(Rc::new(func_type), host_func);
-		self.insert_func(name, func);
-	}
-
-	pub fn insert_func3<
-		Cl: Fn(&mut HostState, P1, P2, P3) -> Result<Ret, Error> + 'static,
-		Ret: IntoReturnVal + 'static,
-		P1: FromArg + 'static,
-		P2: FromArg + 'static,
-		P3: FromArg + 'static,
-		N: Into<String>,
-	>(
-		&mut self,
-		name: N,
-		f: Cl,
-	) {
-		let func_type = FunctionType::new(
-			vec![P1::value_type(), P2::value_type(), P3::value_type()],
-			Ret::value_type(),
-		);
-		let host_func = Rc::new(
-			move |state: &mut HostState, args: &[RuntimeValue]| -> Result<Option<RuntimeValue>, Error> {
-				assert!(args.len() == 3);
-				let mut args = args.into_iter();
-				let result = f(
-					state,
-					P1::from_arg(args.next().unwrap()),
-					P2::from_arg(args.next().unwrap()),
-					P3::from_arg(args.next().unwrap()),
-				)?.into_return_val();
-				Ok(result)
-			},
-		);
-
-		let func = FuncInstance::alloc_host(Rc::new(func_type), host_func);
-		self.insert_func(name, func);
-	}
-
-	pub fn insert_func4<
-		Cl: Fn(&mut HostState, P1, P2, P3, P4) -> Result<Ret, Error> + 'static,
-		Ret: IntoReturnVal + 'static,
-		P1: FromArg + 'static,
-		P2: FromArg + 'static,
-		P3: FromArg + 'static,
-		P4: FromArg + 'static,
-		N: Into<String>,
-	>(
-		&mut self,
-		name: N,
-		f: Cl,
-	) {
-		let func_type = FunctionType::new(
-			vec![
-				P1::value_type(),
-				P2::value_type(),
-				P3::value_type(),
-				P4::value_type(),
-			],
-			Ret::value_type(),
-		);
-		let host_func = Rc::new(
-			move |state: &mut HostState, args: &[RuntimeValue]| -> Result<Option<RuntimeValue>, Error> {
-				assert!(args.len() == 4);
-				let mut args = args.into_iter();
-				let result = f(
-					state,
-					P1::from_arg(args.next().unwrap()),
-					P2::from_arg(args.next().unwrap()),
-					P3::from_arg(args.next().unwrap()),
-					P4::from_arg(args.next().unwrap()),
-				)?.into_return_val();
-				Ok(result)
-			},
-		);
-
-		let func = FuncInstance::alloc_host(Rc::new(func_type), host_func);
-		self.insert_func(name, func);
-	}
-
-	pub fn with_func0<
-		Cl: Fn(&mut HostState) -> Result<Ret, Error> + 'static,
-		Ret: IntoReturnVal + 'static,
-		N: Into<String>,
-	>(
-		mut self,
-		name: N,
-		f: Cl,
-	) -> Self {
-		self.insert_func0(name, f);
-		self
-	}
-
-	pub fn with_func1<
-		Cl: Fn(&mut HostState, P1) -> Result<Ret, Error> + 'static,
-		Ret: IntoReturnVal + 'static,
-		P1: FromArg + 'static,
-		N: Into<String>,
-	>(
-		mut self,
-		name: N,
-		f: Cl,
-	) -> Self {
-		self.insert_func1(name, f);
-		self
-	}
-
-	pub fn with_func2<
-		Cl: Fn(&mut HostState, P1, P2) -> Result<Ret, Error> + 'static,
-		Ret: IntoReturnVal + 'static,
-		P1: FromArg + 'static,
-		P2: FromArg + 'static,
-		N: Into<String>,
-	>(
-		mut self,
-		name: N,
-		f: Cl,
-	) -> Self {
-		self.insert_func2(name, f);
-		self
-	}
-
-	pub fn insert_func<N: Into<String>>(&mut self, name: N, func: FuncRef) {
-		self.insert(name, ExternVal::Func(func));
-	}
-
-	pub fn insert_global<N: Into<String>>(&mut self, name: N, global: GlobalRef) {
-		self.insert(name, ExternVal::Global(global));
-	}
-
-	pub fn insert_memory<N: Into<String>>(&mut self, name: N, memory: MemoryRef) {
-		self.insert(name, ExternVal::Memory(memory));
-	}
-
-	pub fn insert_table<N: Into<String>>(&mut self, name: N, table: TableRef) {
-		self.insert(name, ExternVal::Table(table));
-	}
-
-	pub fn with_global<N: Into<String>>(mut self, name: N, global: GlobalRef) -> Self {
-		self.insert_global(name, global);
-		self
-	}
-
-	pub fn with_memory<N: Into<String>>(mut self, name: N, memory: MemoryRef) -> Self {
-		self.insert_memory(name, memory);
-		self
-	}
-
-	pub fn with_table<N: Into<String>>(mut self, name: N, table: TableRef) -> Self {
-		self.insert_table(name, table);
-		self
-	}
-
-	fn insert<N: Into<String>>(&mut self, name: N, extern_val: ExternVal) {
-		match self.exports.entry(name.into()) {
-			Entry::Vacant(v) => v.insert(extern_val),
-			Entry::Occupied(o) => panic!("Duplicate export name {}", o.key()),
-		};
-	}
-
-	pub fn build(self) -> HostModule {
-		let internal_instance = Rc::new(ModuleInstance::with_exports(self.exports));
-		HostModule { internal_instance }
-	}
-}
-
-pub struct HostModule {
-	internal_instance: Rc<ModuleInstance>,
-}
-
-impl HostModule {
-	pub fn export_by_name(&self, name: &str) -> Option<ExternVal> {
-		self.internal_instance.export_by_name(name)
-	}
-}
-
-impl ImportResolver for HostModule {
-	fn resolve_func(
-		&self,
-		field_name: &str,
-		func_type: &FunctionType,
-	) -> Result<FuncRef, Error> {
-		self.internal_instance.resolve_func(field_name, func_type)
-	}
-
-	fn resolve_global(
-		&self,
-		field_name: &str,
-		global_type: &GlobalType,
-	) -> Result<GlobalRef, Error> {
-		self.internal_instance
-			.resolve_global(field_name, global_type)
-	}
-
-	fn resolve_memory(
-		&self,
-		field_name: &str,
-		memory_type: &MemoryType,
-	) -> Result<MemoryRef, Error> {
-		self.internal_instance
-			.resolve_memory(field_name, memory_type)
-	}
-
-	fn resolve_table(
-		&self,
-		field_name: &str,
-		table_type: &TableType,
-	) -> Result<TableRef, Error> {
-		self.internal_instance.resolve_table(field_name, table_type)
-	}
-}
-
-pub trait FromArg
-where
-	Self: Sized,
-{
-	fn from_arg(arg: &RuntimeValue) -> Self;
-	fn value_type() -> ValueType;
-}
-
-macro_rules! impl_from_arg {
-	($ty: ident, $val_ty: ident) => {
-		impl FromArg for $ty {
-			fn from_arg(arg: &RuntimeValue) -> Self {
-				arg
-					.try_into()
-					.expect(
-						concat!("Due to validation, arg expected to be ", stringify!($val_ty))
-					)
-			}
-
-			fn value_type() -> ValueType {
-				use self::ValueType::*;
-				$val_ty
-			}
-		}
-	}
-}
-
-impl_from_arg!(i32, I32);
-impl_from_arg!(u32, I32);
-impl_from_arg!(i64, I64);
-impl_from_arg!(u64, I64);
-impl_from_arg!(f32, F32);
-impl_from_arg!(f64, F64);
-
-pub trait IntoReturnVal {
-	fn into_return_val(self) -> Option<RuntimeValue>;
-	fn value_type() -> Option<ValueType>;
-}
-
-macro_rules! impl_into_return_val {
-	($ty: ident, $val_ty: ident) => {
-		impl IntoReturnVal for $ty {
-			fn into_return_val(self) -> Option<RuntimeValue> {
-				Some(self.into())
-			}
-
-			fn value_type() -> Option<ValueType> {
-				use self::ValueType::*;
-				Some($val_ty)
-			}
-		}
-	}
-}
-
-impl_into_return_val!(i32, I32);
-impl_into_return_val!(u32, I32);
-impl_into_return_val!(i64, I64);
-impl_into_return_val!(u64, I64);
-impl_into_return_val!(f32, F32);
-impl_into_return_val!(f64, F64);
-
-impl IntoReturnVal for () {
-	fn into_return_val(self) -> Option<RuntimeValue> {
-		None
-	}
-
-	fn value_type() -> Option<ValueType> {
-		None
-	}
-}
-
-trait Externals {
+pub trait Externals {
 	fn invoke_index(
 		&mut self,
-		index: u32,
+		index: HostFuncIndex,
 		args: &[RuntimeValue],
 	) -> Result<Option<RuntimeValue>, Error>;
 
-	// TODO: or check signature?
-	fn signature(&self, index: usize) -> &FunctionType;
+	fn check_signature(&self, index: HostFuncIndex, signature: &FunctionType) -> bool;
 
 	fn memory_by_index(&self, index: usize) -> &MemoryInstance;
 	fn table_by_index(&self, index: usize) -> &TableInstance;
 	fn global_by_index(&self, index: usize) -> &GlobalInstance;
 }
 
+pub struct EmptyExternals;
 
+impl Externals for EmptyExternals {
+	fn invoke_index(
+		&mut self,
+		_index: HostFuncIndex,
+		_args: &[RuntimeValue],
+	) -> Result<Option<RuntimeValue>, Error> {
+		panic!("called invoke_index on EmptyExternals")
+	}
+
+	fn check_signature(&self, _index: HostFuncIndex, _signature: &FunctionType) -> bool {
+		panic!("called check_signature on EmptyExternals")
+	}
+
+	fn memory_by_index(&self, _index: usize) -> &MemoryInstance {
+		panic!("called memory_by_index on EmptyExternals")
+	}
+
+	fn table_by_index(&self, _index: usize) -> &TableInstance {
+		panic!("called table_by_index on EmptyExternals")
+	}
+
+	fn global_by_index(&self, _index: usize) -> &GlobalInstance {
+		panic!("called global_by_index on EmptyExternals")
+	}
+}

src/interpreter/mod.rs

@@ -146,7 +146,6 @@ mod host;
 mod imports;
 mod global;
 mod func;
-mod state;
 
 #[cfg(test)]
 mod tests;
@@ -154,10 +153,9 @@ mod tests;
 pub use self::memory::{MemoryInstance, MemoryRef};
 pub use self::table::{TableInstance, TableRef};
 pub use self::program::ProgramInstance;
-pub use self::value::RuntimeValue;
-pub use self::host::{HostModule, HostModuleBuilder, HostFunc, IntoReturnVal, FromArg};
+pub use self::value::{RuntimeValue, TryInto};
+pub use self::host::{Externals, HostFuncIndex, EmptyExternals};
 pub use self::imports::{ImportResolver, Imports};
 pub use self::module::ModuleInstance;
 pub use self::global::{GlobalInstance, GlobalRef};
 pub use self::func::{FuncInstance, FuncRef};
-pub use self::state::{HostState, StateKey};

src/interpreter/module.rs

@@ -10,8 +10,8 @@ use interpreter::imports::{ImportResolver, Imports};
 use interpreter::global::{GlobalInstance, GlobalRef};
 use interpreter::func::{FuncRef, FuncBody, FuncInstance};
 use interpreter::table::TableRef;
-use interpreter::state::HostState;
 use interpreter::memory::MemoryRef;
+use interpreter::host::Externals;
 use validation::validate_module;
 use common::{DEFAULT_MEMORY_INDEX, DEFAULT_TABLE_INDEX};
 
@@ -187,7 +187,7 @@ impl ModuleInstance {
 							"Due to validation function type should exists",
 						);
 						let actual_fn_type = func.func_type();
-						if expected_fn_type != actual_fn_type {
+						if &*expected_fn_type != actual_fn_type {
 							return Err(Error::Instantiation(format!(
 								"Expected function with type {:?}, but actual type is {:?} for entry {}",
 								expected_fn_type,
@@ -405,11 +405,11 @@ impl ModuleInstance {
 		InstantiationBuilder::new(module)
 	}
 
-	pub fn invoke_index<'a>(
+	pub fn invoke_index<E: Externals>(
 		&self,
 		func_idx: u32,
 		args: &[RuntimeValue],
-		state: &'a mut HostState<'a>,
+		state: &mut E,
 	) -> Result<Option<RuntimeValue>, Error> {
 		let func_instance = self.func_by_index(func_idx).ok_or_else(|| {
 			Error::Program(format!(
@@ -420,11 +420,11 @@ impl ModuleInstance {
 		FuncInstance::invoke(func_instance, Cow::Borrowed(args), state)
 	}
 
-	pub fn invoke_export<'a>(
+	pub fn invoke_export<E: Externals>(
 		&self,
 		func_name: &str,
 		args: &[RuntimeValue],
-		state: &'a mut HostState<'a>,
+		state: &mut E,
 	) -> Result<Option<RuntimeValue>, Error> {
 		let extern_val = self.export_by_name(func_name).ok_or_else(|| {
 			Error::Program(format!("Module doesn't have export {}", func_name))
@@ -474,7 +474,7 @@ impl<'a> InstantiationBuilder<'a> {
 		self
 	}
 
-	pub fn run_start<'b>(mut self, state: &'b mut HostState<'b>) -> Result<Rc<ModuleInstance>, Error> {
+	pub fn run_start<'b, E: Externals>(mut self, state: &'b mut E) -> Result<Rc<ModuleInstance>, Error> {
 		let imports = self.imports.get_or_insert_with(|| Imports::default());
 		let instance = ModuleInstance::instantiate_with_imports(self.module, imports)?;
 

src/interpreter/program.rs

@@ -5,10 +5,9 @@ use elements::Module;
 use interpreter::Error;
 use interpreter::module::{ModuleInstance};
 use interpreter::func::{FuncInstance, FuncRef};
-use interpreter::host::HostModule;
 use interpreter::value::RuntimeValue;
 use interpreter::imports::{Imports, ImportResolver};
-use interpreter::state::HostState;
+use interpreter::host::Externals;
 
 /// Program instance. Program is a set of instantiated modules.
 #[deprecated]
@@ -27,11 +26,11 @@ impl ProgramInstance {
 	}
 
 	/// Instantiate module with validation.
-	pub fn add_module<'a>(
+	pub fn add_module<'a, E: Externals>(
 		&mut self,
 		name: &str,
 		module: Module,
-		state: &'a mut HostState<'a>,
+		externals: &'a mut E,
 	) -> Result<Rc<ModuleInstance>, Error> {
 		let module_instance = {
 			let mut imports = Imports::new();
@@ -43,7 +42,7 @@ impl ProgramInstance {
 			}
 			ModuleInstance::new(&module)
 				.with_imports(imports)
-				.run_start(state)?
+				.run_start(externals)?
 		};
 		self.modules.insert(name.to_owned(), Rc::clone(&module_instance));
 
@@ -58,49 +57,41 @@ impl ProgramInstance {
 		self.resolvers.insert(name.to_owned(), import_resolver);
 	}
 
-	pub fn add_host_module(
-		&mut self,
-		name: &str,
-		host_module: HostModule,
-	) {
-		self.resolvers.insert(name.to_owned(), Box::new(host_module) as Box<ImportResolver>);
-	}
-
 	pub fn insert_loaded_module(&mut self, name: &str, module: Rc<ModuleInstance>) {
 		self.modules.insert(name.to_owned(), module);
 	}
 
-	pub fn invoke_export<'a>(
+	pub fn invoke_export<'a, E: Externals>(
 		&mut self,
 		module_name: &str,
 		func_name: &str,
 		args: &[RuntimeValue],
-		state: &'a mut HostState<'a>,
+		externals: &'a mut E,
 	) -> Result<Option<RuntimeValue>, Error> {
 		let module_instance = self.modules.get(module_name).ok_or_else(|| {
 			Error::Program(format!("Module {} not found", module_name))
 		})?;
-		module_instance.invoke_export(func_name, args, state)
+		module_instance.invoke_export(func_name, args, externals)
 	}
 
-	pub fn invoke_index<'a>(
+	pub fn invoke_index<'a, E: Externals>(
 		&mut self,
 		module_name: &str,
 		func_idx: u32,
 		args: &[RuntimeValue],
-		state: &'a mut HostState<'a>,
+		externals: &'a mut E,
 	) -> Result<Option<RuntimeValue>, Error> {
 		let module_instance = self.modules.get(module_name).cloned().ok_or_else(|| {
 			Error::Program(format!("Module {} not found", module_name))
 		})?;
-		module_instance.invoke_index(func_idx, args, state)
+		module_instance.invoke_index(func_idx, args, externals)
 	}
 
-	pub fn invoke_func<'a>(
+	pub fn invoke_func<'a, E: Externals>(
 		&mut self,
 		func_instance: FuncRef,
 		args: &[RuntimeValue],
-		state: &'a mut HostState<'a>,
+		state: &'a mut E,
 	) -> Result<Option<RuntimeValue>, Error> {
 		FuncInstance::invoke(func_instance.clone(), Cow::Borrowed(args), state)
 	}

src/interpreter/runner.rs

@@ -14,13 +14,13 @@ use interpreter::value::{
 	RuntimeValue, TryInto, WrapInto, TryTruncateInto, ExtendInto,
 	ArithmeticOps, Integer, Float, LittleEndianConvert, TransmuteInto,
 };
+use interpreter::host::Externals;
 use common::{DEFAULT_MEMORY_INDEX, DEFAULT_TABLE_INDEX, BlockFrame, BlockFrameType};
 use common::stack::StackWithLimit;
-use interpreter::state::HostState;
 
 /// Function interpreter.
-pub struct Interpreter<'a, 'b: 'a> {
-	state: &'a mut HostState<'b>,
+pub struct Interpreter<'a, E: Externals + 'a> {
+	externals: &'a mut E,
 }
 
 /// Function execution context.
@@ -64,10 +64,10 @@ enum RunResult {
 	NestedCall(FuncRef),
 }
 
-impl<'a, 'b: 'a> Interpreter<'a, 'b> {
-	pub fn new(state: &'a mut HostState<'b>) -> Interpreter<'a, 'b> {
+impl<'a, E: Externals> Interpreter<'a, E> {
+	pub fn new(externals: &'a mut E) -> Interpreter<'a, E> {
 		Interpreter {
-			state: state,
+			externals,
 		}
 	}
 
@@ -105,7 +105,7 @@ impl<'a, 'b: 'a> Interpreter<'a, 'b> {
 						},
 						FuncInstance::Host { ref func_type, .. } => {
 							let args = prepare_function_args(func_type, &mut function_context.value_stack)?;
-							let return_val = FuncInstance::invoke(nested_func.clone(), args.into(), self.state)?;
+							let return_val = FuncInstance::invoke(nested_func.clone(), args.into(), self.externals)?;
 							if let Some(return_val) = return_val {
 								function_context.value_stack_mut().push(return_val)?;
 							}
@@ -439,13 +439,14 @@ impl<'a, 'b: 'a> Interpreter<'a, 'b> {
 			.expect("Due to validation table should exists");
 		let func_ref = table.get(table_func_idx)?;
 
+		{
 			let actual_function_type = func_ref.func_type();
 			let required_function_type = context
 				.module()
 				.type_by_index(type_idx)
 				.expect("Due to validation type should exists");
 
-		if required_function_type != actual_function_type {
+			if &*required_function_type != actual_function_type {
 				return Err(Error::Function(format!(
 					"expected function with signature ({:?}) -> {:?} when got with ({:?}) -> {:?}",
 					required_function_type.params(),
@@ -454,6 +455,7 @@ impl<'a, 'b: 'a> Interpreter<'a, 'b> {
 					actual_function_type.return_type()
 				)));
 			}
+		}
 
 		Ok(InstructionOutcome::ExecuteCall(func_ref))
 	}

src/interpreter/state.rs

@@ -1,138 +0,0 @@
-
-use std::any::{Any, TypeId};
-use std::collections::HashMap;
-
-pub unsafe trait StateKey {
-	type Static: ?Sized + 'static;
-}
-
-pub fn type_id<T>() -> TypeId
-where
-	T: StateKey,
-	T::Static: Any,
-{
-	TypeId::of::<T::Static>()
-}
-
-#[derive(Default)]
-pub struct HostState<'a> {
-	data: HashMap<TypeId, *mut ()>,
-	_marker: ::std::marker::PhantomData<&'a mut ()>,
-}
-
-impl<'a> HostState<'a> {
-	pub fn new() -> Self {
-		HostState {
-			data: HashMap::default(),
-			_marker: ::std::marker::PhantomData,
-		}
-	}
-
-	pub fn insert<V: StateKey + 'a>(&mut self, val: &'a mut V) {
-		let ty_id = type_id::<V>();
-		let ptr = val as *mut V as *mut ();
-		let existing = self.data.insert(ty_id, ptr);
-		assert!(existing.is_none());
-	}
-
-	pub fn with<V: StateKey + 'a, R, F: FnOnce(&V) -> R>(&self, f: F) -> R {
-		let ptr = self.data.get(&type_id::<V>()).unwrap();
-		unsafe {
-			let val_ref = &*(*ptr as *const V);
-			f(val_ref)
-		}
-	}
-
-	pub fn with_mut<V: StateKey + 'a, R, F: FnOnce(&mut V) -> R + 'static>(&mut self, f: F) -> R {
-		let ptr = self.data.get_mut(&type_id::<V>()).unwrap();
-		unsafe {
-			let val_ref = &mut *(*ptr as *mut V);
-			f(val_ref)
-		}
-	}
-}
-
-#[cfg(test)]
-mod tests {
-	use super::*;
-
-	struct MyState<'a>(&'a mut i32);
-	impl<'a> MyState<'a> {
-		fn inc(&mut self) {
-			*self.0 += 1;
-		}
-
-		fn get(&self) -> i32 {
-			*self.0
-		}
-	}
-
-	/// Safety of this impl should be ensured by a macro.
-	unsafe impl<'a> StateKey for MyState<'a> {
-		type Static = MyState<'static>;
-	}
-
-	#[test]
-	fn it_works() {
-		let mut counter = 33i32;
-
-		let new_value = {
-			let mut my_state = MyState(&mut counter);
-			let mut host_state = HostState::new();
-			host_state.insert::<MyState>(&mut my_state);
-			host_state.with_mut(|my_state: &mut MyState| {
-				my_state.inc();
-				my_state.get()
-			})
-		};
-
-		assert_eq!(new_value, counter);
-	}
-
-	struct MyImmutableState<'a>(&'a i32);
-	/// Safety of this impl should be ensured by a macro.
-	unsafe impl<'a> StateKey for MyImmutableState<'a> {
-		type Static = MyImmutableState<'static>;
-	}
-
-	struct StaticState(i32);
-
-	impl StaticState {
-		fn inc(&mut self) {
-			self.0 += 1;
-		}
-
-		fn get(&self) -> i32 {
-			self.0
-		}
-	}
-
-	/// Safety of this impl should be ensured by a macro.
-	unsafe impl<'a> StateKey for StaticState {
-		type Static = StaticState;
-	}
-
-	#[test]
-	fn compiles_with_static() {
-		let mut static_state = StaticState(45);
-		let mut host_state = HostState::new();
-		host_state.insert::<StaticState>(&mut static_state);
-		host_state.with_mut(|my_state: &mut StaticState| {
-			my_state.inc();
-		});
-		host_state.with_mut(|my_state: &mut StaticState| {
-			my_state.inc();
-			assert_eq!(47, my_state.get());
-		})
-	}
-
-	#[test]
-	#[should_panic]
-	fn doesnt_allow_dups() {
-		let mut static_state_1 = StaticState(45);
-		let mut static_state_2 = StaticState(45);
-		let mut host_state = HostState::new();
-		host_state.insert::<StaticState>(&mut static_state_1);
-		host_state.insert::<StaticState>(&mut static_state_2);
-	}
-}