You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
93 lines
3.1 KiB
93 lines
3.1 KiB
//! An example of how to interact with wasm memory.
|
|
//!
|
|
//! Here a small wasm module is used to show how memory is initialized, how to
|
|
//! read and write memory through the `Memory` object, and how wasm functions
|
|
//! can trap when dealing with out-of-bounds addresses.
|
|
|
|
// You can execute this example with `cargo run --example example`
|
|
|
|
use anyhow::Result;
|
|
use wasmtime::*;
|
|
|
|
fn main() -> Result<()> {
|
|
// Create our `Store` context and then compile a module and create an
|
|
// instance from the compiled module all in one go.
|
|
let wasmtime_store = Store::default();
|
|
let module = Module::from_file(wasmtime_store.engine(), "examples/memory.wat")?;
|
|
let instance = Instance::new(&wasmtime_store, &module, &[])?;
|
|
|
|
// Load up our exports from the instance
|
|
let memory = instance
|
|
.get_memory("memory")
|
|
.ok_or(anyhow::format_err!("failed to find `memory` export"))?;
|
|
let size = instance
|
|
.get_func("size")
|
|
.ok_or(anyhow::format_err!("failed to find `size` export"))?
|
|
.get0::<i32>()?;
|
|
let load = instance
|
|
.get_func("load")
|
|
.ok_or(anyhow::format_err!("failed to find `load` export"))?
|
|
.get1::<i32, i32>()?;
|
|
let store = instance
|
|
.get_func("store")
|
|
.ok_or(anyhow::format_err!("failed to find `store` export"))?
|
|
.get2::<i32, i32, ()>()?;
|
|
|
|
// Note that these memory reads are *unsafe* due to unknown knowledge about
|
|
// aliasing with wasm memory. For more information about the safety
|
|
// guarantees here and how to use `Memory` safely, see the API
|
|
// documentation.
|
|
println!("Checking memory...");
|
|
assert_eq!(memory.size(), 2);
|
|
assert_eq!(memory.data_size(), 0x20000);
|
|
unsafe {
|
|
assert_eq!(memory.data_unchecked_mut()[0], 0);
|
|
assert_eq!(memory.data_unchecked_mut()[0x1000], 1);
|
|
assert_eq!(memory.data_unchecked_mut()[0x1003], 4);
|
|
}
|
|
|
|
assert_eq!(size()?, 2);
|
|
assert_eq!(load(0)?, 0);
|
|
assert_eq!(load(0x1000)?, 1);
|
|
assert_eq!(load(0x1003)?, 4);
|
|
assert_eq!(load(0x1ffff)?, 0);
|
|
assert!(load(0x20000).is_err()); // out of bounds trap
|
|
|
|
println!("Mutating memory...");
|
|
unsafe {
|
|
memory.data_unchecked_mut()[0x1003] = 5;
|
|
}
|
|
|
|
store(0x1002, 6)?;
|
|
assert!(store(0x20000, 0).is_err()); // out of bounds trap
|
|
|
|
unsafe {
|
|
assert_eq!(memory.data_unchecked_mut()[0x1002], 6);
|
|
assert_eq!(memory.data_unchecked_mut()[0x1003], 5);
|
|
}
|
|
assert_eq!(load(0x1002)?, 6);
|
|
assert_eq!(load(0x1003)?, 5);
|
|
|
|
// Grow memory.
|
|
println!("Growing memory...");
|
|
memory.grow(1)?;
|
|
assert_eq!(memory.size(), 3);
|
|
assert_eq!(memory.data_size(), 0x30000);
|
|
|
|
assert_eq!(load(0x20000)?, 0);
|
|
store(0x20000, 0)?;
|
|
assert!(load(0x30000).is_err());
|
|
assert!(store(0x30000, 0).is_err());
|
|
|
|
assert!(memory.grow(1).is_err());
|
|
assert!(memory.grow(0).is_ok());
|
|
|
|
println!("Creating stand-alone memory...");
|
|
let memorytype = MemoryType::new(Limits::new(5, Some(5)));
|
|
let memory2 = Memory::new(&wasmtime_store, memorytype);
|
|
assert_eq!(memory2.size(), 5);
|
|
assert!(memory2.grow(1).is_err());
|
|
assert!(memory2.grow(0).is_ok());
|
|
|
|
Ok(())
|
|
}
|
|
|