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 anyhow::Result; 10 use wasmtime::*; 11 12 fn main() -> Result<()> { 13 // Create our `store_fn` context and then compile a module and create an 14 // instance from the compiled module all in one go. 15 let mut store: Store<()> = Store::default(); 16 let module = Module::from_file(store.engine(), "examples/memory.wat")?; 17 let instance = Instance::new(&mut store, &module, &[])?; 18 19 // load_fn up our exports from the instance 20 let memory = instance 21 .get_memory(&mut store, "memory") 22 .ok_or(anyhow::format_err!("failed to find `memory` export"))?; 23 let size = instance.get_typed_func::<(), i32>(&mut store, "size")?; 24 let load_fn = instance.get_typed_func::<i32, i32>(&mut store, "load")?; 25 let store_fn = instance.get_typed_func::<(i32, i32), ()>(&mut store, "store")?; 26 27 println!("Checking memory..."); 28 assert_eq!(memory.size(&store), 2); 29 assert_eq!(memory.data_size(&store), 0x20000); 30 assert_eq!(memory.data_mut(&mut store)[0], 0); 31 assert_eq!(memory.data_mut(&mut store)[0x1000], 1); 32 assert_eq!(memory.data_mut(&mut store)[0x1003], 4); 33 34 assert_eq!(size.call(&mut store, ())?, 2); 35 assert_eq!(load_fn.call(&mut store, 0)?, 0); 36 assert_eq!(load_fn.call(&mut store, 0x1000)?, 1); 37 assert_eq!(load_fn.call(&mut store, 0x1003)?, 4); 38 assert_eq!(load_fn.call(&mut store, 0x1ffff)?, 0); 39 assert!(load_fn.call(&mut store, 0x20000).is_err()); // out of bounds trap 40 41 println!("Mutating memory..."); 42 memory.data_mut(&mut store)[0x1003] = 5; 43 44 store_fn.call(&mut store, (0x1002, 6))?; 45 assert!(store_fn.call(&mut store, (0x20000, 0)).is_err()); // out of bounds trap 46 47 assert_eq!(memory.data(&store)[0x1002], 6); 48 assert_eq!(memory.data(&store)[0x1003], 5); 49 assert_eq!(load_fn.call(&mut store, 0x1002)?, 6); 50 assert_eq!(load_fn.call(&mut store, 0x1003)?, 5); 51 52 // Grow memory. 53 println!("Growing memory..."); 54 memory.grow(&mut store, 1)?; 55 assert_eq!(memory.size(&store), 3); 56 assert_eq!(memory.data_size(&store), 0x30000); 57 58 assert_eq!(load_fn.call(&mut store, 0x20000)?, 0); 59 store_fn.call(&mut store, (0x20000, 0))?; 60 assert!(load_fn.call(&mut store, 0x30000).is_err()); 61 assert!(store_fn.call(&mut store, (0x30000, 0)).is_err()); 62 63 assert!(memory.grow(&mut store, 1).is_err()); 64 assert!(memory.grow(&mut store, 0).is_ok()); 65 66 println!("Creating stand-alone memory..."); 67 let memorytype = MemoryType::new(5, Some(5)); 68 let memory2 = Memory::new(&mut store, memorytype)?; 69 assert_eq!(memory2.size(&store), 5); 70 assert!(memory2.grow(&mut store, 1).is_err()); 71 assert!(memory2.grow(&mut store, 0).is_ok()); 72 73 Ok(()) 74 } 75