instance.py

# Wasmer will let you easily run WebAssembly module in a Python host.
#
# This example illustrates the basics of using Wasmer through a “Hello
# World”-like project:
#
#   1. How to load a WebAssembly module as bytes,
#   2. How to compile the module,
#   3. How to create an instance of the module.
#
# You can run the example directly by executing in Wasmer root:
#
# ```shell
# $ python examples/instance.py
# ```
#
# Ready?

from wasmer import engine, wat2wasm, Store, Module, Instance
from wasmer_compiler_cranelift import Compiler

# Let's declare the Wasm module.
#
# We are using the text representation of the module here but you can
# also load `.wasm` files using the `open` function.
wasm_bytes = wat2wasm(
    """
    (module
      (type $add_one_t (func (param i32) (result i32)))
      (func $add_one_f (type $add_one_t) (param $value i32) (result i32)
        local.get $value
        i32.const 1
        i32.add)
      (export "add_one" (func $add_one_f)))
    """
)

# Create a store. Engines and compilers are explained in other
# examples.
store = Store(engine.Universal(Compiler))

# Let's compile the Wasm module.
module = Module(store, wasm_bytes)

# Let's instantiate the module!
instance = Instance(module)

# We now have an instance ready to be used.
#
# From an `Instance` we can retrieve any exported entities. Each of
# these entities is covered in others examples.
#
# Here we are retrieving the exported function. We won't go into
# details here as the main focus of this example is to show how to
# create an instance out of a Wasm module and have basic interactions
# with it.
assert instance.exports.add_one(1) == 2