feat: add example4

__wasm/wasmtime/examples/example4.rs

@@ -0,0 +1,29 @@
+use anyhow::Result;
+use wasmtime::*;
+
+fn main() -> Result<()> {
+    // Modules can be compiled through either the text or binary format
+    let engine = Engine::default();
+    let wasm = include_bytes!("/Users/hatterjiang/Code/hattergit/simple-rust-tests/__wasm/wasmtime/wasms/simple_rust_wasm/target/wasm32-unknown-unknown/debug/simple_rust_wasm.wasm");
+    let module = Module::new(&engine, wasm)?;
+
+    // Create a `Linker` which will be later used to instantiate this module.
+    // Host functionality is defined by name within the `Linker`.
+    let mut linker = Linker::new(&engine);
+    linker.func_wrap("host", "hello", |caller: Caller<'_, u32>, param: i32| {
+        println!("Got {} from WebAssembly", param);
+        println!("my host state is: {}", caller.data());
+    })?;
+
+    // All wasm objects operate within the context of a "store". Each
+    // `Store` has a type parameter to store host-specific data, which in
+    // this case we're using `4` for.
+    let mut store = Store::new(&engine, 4);
+    let instance = linker.instantiate(&mut store, &module)?;
+    let hello = instance.get_typed_func::<(), ()>(&mut store, "hello")?;
+
+    // And finally we can call the wasm!
+    hello.call(&mut store, ())?;
+
+    Ok(())
+}

__wasm/wasmtime/justfile

@@ -15,3 +15,8 @@ run_example2:
 run_example3:
   cargo run --example example3
 
+run_example4:
+  cd wasms/simple_rust_wasm; cargo build --target wasm32-unknown-unknown
+  cp wasms/simple_rust_wasm/target/wasm32-unknown-unknown/debug/simple_rust_wasm.wasm .
+  cargo run --example example4
+  rm simple_rust_wasm.wasm

__wasm/wasmtime/wasms/simple_rust_wasm/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "simple_rust_wasm"
+version = "0.1.0"

__wasm/wasmtime/wasms/simple_rust_wasm/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "simple_rust_wasm"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[lib]
+crate-type = ['cdylib']
+
+[dependencies]
+

__wasm/wasmtime/wasms/simple_rust_wasm/justfile

@@ -0,0 +1,7 @@
+_:
+  @just --list
+
+build:
+  cargo build --target wasm32-unknown-unknown
+
+

__wasm/wasmtime/wasms/simple_rust_wasm/src/lib.rs

@@ -0,0 +1,12 @@
+#[link(wasm_import_module = "host")]
+extern "C" {
+
+     #[link_name = "hello"]
+    fn host_hello(a: i32);
+}
+
+#[no_mangle]
+pub extern "C" fn hello() {
+  unsafe { host_hello(3); }
+}
+