1 //! An example of how to interact with wasm memory. 2 //! 3 //! Here a small wasm module is used to show how memory is initialized, how to 4 //! read and write memory through the `Memory` object, and how wasm functions 5 //! can trap when dealing with out-of-bounds addresses. 6 7 // You can execute this example with `cargo run --example memory` 8 9 use wasmtime::*; 10 11 fn main() -> Result<()> { 12 // Create our `store_fn` context and then compile a module and create an 13 // instance from the compiled module all in one go. 14 let mut store: Store<()> = Store::default(); 15 let module = Module::from_file(store.engine(), "examples/memory.wat")?; 16 let instance = Instance::new(&mut store, &module, &[])?; 17 18 // load_fn up our exports from the instance 19 let memory = instance 20 .get_memory(&mut store, "memory") 21 .ok_or(wasmtime::format_err!("failed to find `memory` export"))?; 22 let size = instance.get_typed_func::<(), i32>(&mut store, "size")?; 23 let load_fn = instance.get_typed_func::<i32, i32>(&mut store, "load")?; 24 let store_fn = instance.get_typed_func::<(i32, i32), ()>(&mut store, "store")?; 25 26 println!("Checking memory..."); 27 assert_eq!(memory.size(&store), 2); 28 assert_eq!(memory.data_size(&store), 0x20000); 29 assert_eq!(memory.data_mut(&mut store)[0], 0); 30 assert_eq!(memory.data_mut(&mut store)[0x1000], 1); 31 assert_eq!(memory.data_mut(&mut store)[0x1003], 4); 32 33 assert_eq!(size.call(&mut store, ())?, 2); 34 assert_eq!(load_fn.call(&mut store, 0)?, 0); 35 assert_eq!(load_fn.call(&mut store, 0x1000)?, 1); 36 assert_eq!(load_fn.call(&mut store, 0x1003)?, 4); 37 assert_eq!(load_fn.call(&mut store, 0x1ffff)?, 0); 38 assert!(load_fn.call(&mut store, 0x20000).is_err()); // out of bounds trap 39 40 println!("Mutating memory..."); 41 memory.data_mut(&mut store)[0x1003] = 5; 42 43 store_fn.call(&mut store, (0x1002, 6))?; 44 assert!(store_fn.call(&mut store, (0x20000, 0)).is_err()); // out of bounds trap 45 46 assert_eq!(memory.data(&store)[0x1002], 6); 47 assert_eq!(memory.data(&store)[0x1003], 5); 48 assert_eq!(load_fn.call(&mut store, 0x1002)?, 6); 49 assert_eq!(load_fn.call(&mut store, 0x1003)?, 5); 50 51 // Grow memory. 52 println!("Growing memory..."); 53 memory.grow(&mut store, 1)?; 54 assert_eq!(memory.size(&store), 3); 55 assert_eq!(memory.data_size(&store), 0x30000); 56 57 assert_eq!(load_fn.call(&mut store, 0x20000)?, 0); 58 store_fn.call(&mut store, (0x20000, 0))?; 59 assert!(load_fn.call(&mut store, 0x30000).is_err()); 60 assert!(store_fn.call(&mut store, (0x30000, 0)).is_err()); 61 62 assert!(memory.grow(&mut store, 1).is_err()); 63 assert!(memory.grow(&mut store, 0).is_ok()); 64 65 println!("Creating stand-alone memory..."); 66 let memorytype = MemoryType::new(5, Some(5)); 67 let memory2 = Memory::new(&mut store, memorytype)?; 68 assert_eq!(memory2.size(&store), 5); 69 assert!(memory2.grow(&mut store, 1).is_err()); 70 assert!(memory2.grow(&mut store, 0).is_ok()); 71 72 Ok(()) 73 } 74