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73 lines
2.9 KiB
73 lines
2.9 KiB
//! An example of how to interact with wasm memory.
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//!
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//! Here a small wasm module is used to show how memory is initialized, how to
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//! read and write memory through the `Memory` object, and how wasm functions
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//! can trap when dealing with out-of-bounds addresses.
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// You can execute this example with `cargo run --example memory`
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use wasmtime::*;
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fn main() -> Result<()> {
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// Create our `store_fn` context and then compile a module and create an
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// instance from the compiled module all in one go.
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let mut store: Store<()> = Store::default();
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let module = Module::from_file(store.engine(), "examples/memory.wat")?;
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let instance = Instance::new(&mut store, &module, &[])?;
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// load_fn up our exports from the instance
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let memory = instance
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.get_memory(&mut store, "memory")
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.ok_or(anyhow::format_err!("failed to find `memory` export"))?;
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let size = instance.get_typed_func::<(), i32>(&mut store, "size")?;
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let load_fn = instance.get_typed_func::<i32, i32>(&mut store, "load")?;
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let store_fn = instance.get_typed_func::<(i32, i32), ()>(&mut store, "store")?;
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println!("Checking memory...");
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assert_eq!(memory.size(&store), 2);
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assert_eq!(memory.data_size(&store), 0x20000);
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assert_eq!(memory.data_mut(&mut store)[0], 0);
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assert_eq!(memory.data_mut(&mut store)[0x1000], 1);
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assert_eq!(memory.data_mut(&mut store)[0x1003], 4);
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assert_eq!(size.call(&mut store, ())?, 2);
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assert_eq!(load_fn.call(&mut store, 0)?, 0);
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assert_eq!(load_fn.call(&mut store, 0x1000)?, 1);
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assert_eq!(load_fn.call(&mut store, 0x1003)?, 4);
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assert_eq!(load_fn.call(&mut store, 0x1ffff)?, 0);
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assert!(load_fn.call(&mut store, 0x20000).is_err()); // out of bounds trap
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println!("Mutating memory...");
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memory.data_mut(&mut store)[0x1003] = 5;
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store_fn.call(&mut store, (0x1002, 6))?;
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assert!(store_fn.call(&mut store, (0x20000, 0)).is_err()); // out of bounds trap
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assert_eq!(memory.data(&store)[0x1002], 6);
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assert_eq!(memory.data(&store)[0x1003], 5);
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assert_eq!(load_fn.call(&mut store, 0x1002)?, 6);
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assert_eq!(load_fn.call(&mut store, 0x1003)?, 5);
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// Grow memory.
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println!("Growing memory...");
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memory.grow(&mut store, 1)?;
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assert_eq!(memory.size(&store), 3);
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assert_eq!(memory.data_size(&store), 0x30000);
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assert_eq!(load_fn.call(&mut store, 0x20000)?, 0);
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store_fn.call(&mut store, (0x20000, 0))?;
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assert!(load_fn.call(&mut store, 0x30000).is_err());
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assert!(store_fn.call(&mut store, (0x30000, 0)).is_err());
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assert!(memory.grow(&mut store, 1).is_err());
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assert!(memory.grow(&mut store, 0).is_ok());
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println!("Creating stand-alone memory...");
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let memorytype = MemoryType::new(5, Some(5));
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let memory2 = Memory::new(&mut store, memorytype)?;
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assert_eq!(memory2.size(&store), 5);
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assert!(memory2.grow(&mut store, 1).is_err());
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assert!(memory2.grow(&mut store, 0).is_ok());
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Ok(())
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}
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