pub fn new_with_locals(locals: &[(u32, ValType)]) -> Self {

        Self {

            func: Function::new(locals.iter().copied()),

        }

    }

    pub fn memory_init(&mut self, data_idx: u32, dst: u32, len: u32) {

        self.func.instruction(&Instruction::I32Const(dst as i32));

        self.func.instruction(&Instruction::I32Const(0)); // src offset in data segment

        self.func.instruction(&Instruction::I32Const(len as i32));

        self.func.instruction(&Instruction::MemoryInit {

            mem: 0,

            data_index: data_idx,

        });

    }

    pub fn local_get(&mut self, idx: u32) {

        self.func.instruction(&Instruction::LocalGet(idx));

    }

    pub fn local_set(&mut self, idx: u32) {

        self.func.instruction(&Instruction::LocalSet(idx));

    }

    pub fn i32_const(&mut self, value: i32) {

        self.func.instruction(&Instruction::I32Const(value));

    }

    pub fn i32_add(&mut self) {

        self.func.instruction(&Instruction::I32Add);

    }

    pub fn i32_ge_u(&mut self) {

        self.func.instruction(&Instruction::I32GeU);

    }

    pub fn array_new_data(&mut self, type_idx: u32, data_idx: u32) {

        self.func.instruction(&Instruction::ArrayNewData {

            array_type_index: type_idx,

            array_data_index: data_idx,

        });

    }

    pub fn array_get_u(&mut self, type_idx: u32) {

        self.func.instruction(&Instruction::ArrayGetU(type_idx));

    }

    pub fn block_start(&mut self) {

        self.func.instruction(&Instruction::Block(BlockType::Empty));

    }

    pub fn loop_start(&mut self) {

        self.func.instruction(&Instruction::Loop(BlockType::Empty));

    }

    pub fn block_end(&mut self) {

        self.func.instruction(&Instruction::End);

    }

    pub fn br(&mut self, depth: u32) {

        self.func.instruction(&Instruction::Br(depth));

    }

    pub fn br_if(&mut self, depth: u32) {

        self.func.instruction(&Instruction::BrIf(depth));

    }

    pub fn call(&mut self, func_idx: u32) {

        self.func.instruction(&Instruction::Call(func_idx));

    }

    pub fn store_u8_dynamic(&mut self, local_base: u32, offset: u32, value: u8) {

        self.func.instruction(&Instruction::LocalGet(local_base));

        self.func.instruction(&Instruction::I32Const(offset as i32));

        self.func.instruction(&Instruction::I32Add);

        self.func

            .instruction(&Instruction::I32Const(i32::from(value)));

        self.func.instruction(&Instruction::I32Store8(MemArg {

            offset: 0,

            align: 0,

            memory_index: 0,

        }));

    }

    pub fn store_i32_dynamic(&mut self, local_base: u32, offset: u32, value: i32) {

        self.func.instruction(&Instruction::LocalGet(local_base));

        self.func.instruction(&Instruction::I32Const(offset as i32));

        self.func.instruction(&Instruction::I32Add);

        self.func.instruction(&Instruction::I32Const(value));

        self.func.instruction(&Instruction::I32Store(MemArg {

            offset: 0,

            align: 2,

            memory_index: 0,

        }));

    }

    pub fn store_i64_dynamic(&mut self, local_base: u32, offset: u32, value: i64) {

        self.func.instruction(&Instruction::LocalGet(local_base));

        self.func.instruction(&Instruction::I32Const(offset as i32));

        self.func.instruction(&Instruction::I32Add);

        self.func.instruction(&Instruction::I64Const(value));

        self.func.instruction(&Instruction::I64Store(MemArg {

            offset: 0,

            align: 3,

            memory_index: 0,

        }));

    }

    pub fn i32_store8_raw(&mut self) {

        self.func.instruction(&Instruction::I32Store8(MemArg {

            offset: 0,

            align: 0,

            memory_index: 0,

        }));

    }

    pub fn end(&mut self) {

        self.func.instruction(&Instruction::End);

    }

    pub fn finish(self) -> Function {

        self.func

    }