9364eb1d98
* Compute instance exports on demand. Instead having instances eagerly compute a Vec of Externs, and bumping the refcount for each Extern, compute Externs on demand. This also enables `Instance::get_export` to avoid doing a linear search. This also means that the closure returned by `get0` and friends now holds an `InstanceHandle` to dynamically hold the instance live rather than being scoped to a lifetime. * Compute module imports and exports on demand too. And compute Extern::ty on demand too. * Add a utility function for computing an ExternType. * Add a utility function for looking up a function's signature. * Add a utility function for computing the ValType of a Global. * Rename wasmtime_environ::Export to EntityIndex. This helps differentiate it from other Export types in the tree, and describes what it is. * Fix a typo in a comment. * Simplify module imports and exports. * Make `Instance::exports` return the export names. This significantly simplifies the public API, as it's relatively common to need the names, and this avoids the need to do a zip with `Module::exports`. This also changes `ImportType` and `ExportType` to have public members instead of private members and accessors, as I find that simplifies the usage particularly in cases where there are temporary instances. * Remove `Instance::module`. This doesn't quite remove `Instance`'s `module` member, it gets a step closer. * Use a InstanceHandle utility function. * Don't consume self in the `Func::get*` methods. Instead, just create a closure containing the instance handle and the export for them to call. * Use `ExactSizeIterator` to avoid needing separate `num_*` methods. * Rename `Extern::func()` etc. to `into_func()` etc. * Revise examples to avoid using `nth`. * Add convenience methods to instance for getting specific extern types. * Use the convenience functions in more tests and examples. * Avoid cloning strings for `ImportType` and `ExportType`. * Remove more obviated clone() calls. * Simplify `Func`'s closure state. * Make wasmtime::Export's fields private. This makes them more consistent with ExportType. * Fix compilation error. * Make a lifetime parameter explicit, and use better lifetime names. Instead of 'me, use 'instance and 'module to make it clear what the lifetime is. * More lifetime cleanups.
94 lines
3.1 KiB
Rust
94 lines
3.1 KiB
Rust
//! 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 example`
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use anyhow::Result;
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use wasmtime::*;
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fn main() -> Result<()> {
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// Create our `Store` 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 wasmtime_store = Store::default();
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let module = Module::from_file(&wasmtime_store, "examples/memory.wat")?;
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let instance = Instance::new(&module, &[])?;
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// Load up our exports from the instance
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let memory = instance
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.get_memory("memory")
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.ok_or(anyhow::format_err!("failed to find `memory` export"))?;
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let size = instance
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.get_func("size")
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.ok_or(anyhow::format_err!("failed to find `size` export"))?
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.get0::<i32>()?;
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let load = instance
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.get_func("load")
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.ok_or(anyhow::format_err!("failed to find `load` export"))?
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.get1::<i32, i32>()?;
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let store = instance
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.get_func("store")
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.ok_or(anyhow::format_err!("failed to find `store` export"))?
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.get2::<i32, i32, ()>()?;
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// Note that these memory reads are *unsafe* due to unknown knowledge about
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// aliasing with wasm memory. For more information about the safety
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// guarantees here and how to use `Memory` safely, see the API
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// documentation.
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println!("Checking memory...");
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assert_eq!(memory.size(), 2);
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assert_eq!(memory.data_size(), 0x20000);
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unsafe {
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assert_eq!(memory.data_unchecked_mut()[0], 0);
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assert_eq!(memory.data_unchecked_mut()[0x1000], 1);
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assert_eq!(memory.data_unchecked_mut()[0x1003], 4);
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}
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assert_eq!(size()?, 2);
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assert_eq!(load(0)?, 0);
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assert_eq!(load(0x1000)?, 1);
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assert_eq!(load(0x1003)?, 4);
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assert_eq!(load(0x1ffff)?, 0);
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assert!(load(0x20000).is_err()); // out of bounds trap
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println!("Mutating memory...");
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unsafe {
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memory.data_unchecked_mut()[0x1003] = 5;
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}
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store(0x1002, 6)?;
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assert!(store(0x20000, 0).is_err()); // out of bounds trap
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unsafe {
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assert_eq!(memory.data_unchecked_mut()[0x1002], 6);
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assert_eq!(memory.data_unchecked_mut()[0x1003], 5);
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}
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assert_eq!(load(0x1002)?, 6);
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assert_eq!(load(0x1003)?, 5);
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// Grow memory.
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println!("Growing memory...");
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memory.grow(1)?;
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assert_eq!(memory.size(), 3);
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assert_eq!(memory.data_size(), 0x30000);
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assert_eq!(load(0x20000)?, 0);
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store(0x20000, 0)?;
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assert!(load(0x30000).is_err());
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assert!(store(0x30000, 0).is_err());
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assert!(memory.grow(1).is_err());
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assert!(memory.grow(0).is_ok());
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println!("Creating stand-alone memory...");
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let memorytype = MemoryType::new(Limits::new(5, Some(5)));
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let memory2 = Memory::new(&wasmtime_store, memorytype);
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assert_eq!(memory2.size(), 5);
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assert!(memory2.grow(1).is_err());
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assert!(memory2.grow(0).is_ok());
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Ok(())
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}
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