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Wasmer Rust Embedder App Example
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| extern crate wasmer_runtime; | |
| use std::{fs::File, io::prelude::*, str}; | |
| use wasmer_runtime::{self as runtime, prelude::*}; | |
| fn main() { | |
| // Read the wasm file produced by our sample application... | |
| let mut wasm_file = | |
| File::open("./wasm-sample-app/target/wasm32-unknown-unknown/release/wasm_sample_app.wasm") | |
| .unwrap(); | |
| // ... and put it into a vector. | |
| let mut wasm_bytes = Vec::new(); | |
| wasm_file.read_to_end(&mut wasm_bytes).unwrap(); | |
| // Compile our webassembly into a wasmer-runtime `Module`. | |
| let module = runtime::compile(&wasm_bytes).unwrap(); | |
| // Let's define the import object used to import our function | |
| // into our webassembly sample application. | |
| // | |
| // We've defined a macro that makes it super easy. | |
| // | |
| // The signature tells the runtime what the signature (the parameter | |
| // and return types) of the function we're defining here is. | |
| // The allowed types are `i32`, `u32`, `i64`, `u64`, | |
| // `f32`, and `f64`. | |
| // | |
| // Make sure to check this carefully! | |
| let import_object = imports! { | |
| // Define the "env" namespace that was implicitly used | |
| // by our sample application. | |
| "env" => { | |
| // name // func // signature | |
| "print_str" => print_str<[u32, u32] -> []>, | |
| }, | |
| }; | |
| // Here we go! | |
| // | |
| // Instantiate the module with the imports we just created | |
| // to create, you guessed it, an `Instance`. | |
| // | |
| // You can create any number of instances with a single module. | |
| let mut instance = module.instantiate(import_object).unwrap(); | |
| // At last, we can call the function exported by our webassembly | |
| // sample application. | |
| // | |
| // Since our exported function doesn't receive any parameters, | |
| // we just pass it an empty slice as the parameter list. | |
| instance.call("hello_wasm", &[]).unwrap(); | |
| } | |
| // Let's define our "print_str" function. | |
| // | |
| // The declaration must start with "extern" or "extern "C"". | |
| extern "C" fn print_str(ptr: u32, len: u32, vmctx: &mut vm::Ctx) { | |
| // Get a slice that maps to the memory currently used by the webassembly | |
| // instance. | |
| // | |
| // Webassembly only supports a single memory for now, | |
| // but in the near future, it'll support multiple. | |
| // | |
| // Therefore, we don't assume you always just want to access first | |
| // memory and force you to specify the first memory. | |
| let memory = vmctx.memory(0); | |
| // Get a subslice that corresponds to the memory used by the string. | |
| let str_slice = &memory[ptr as usize..(ptr + len) as usize]; | |
| // Convert the subslice to a `&str`. | |
| let string = str::from_utf8(str_slice).unwrap(); | |
| // Print it! | |
| println!("{}", string); | |
| } |
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