2019-01-24 18:51:20 +00:00
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# Wasmer-Runtime
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Wasmer-runtime is a library that makes embedding WebAssembly
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in your application easy, efficient, and safe.
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# How to use Wasmer-Runtime
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The easiest way is to use the [`instantiate`] function to create an [`Instance`].
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Then you can use [`call`] or [`func`] and then [`call`][func.call] to call an exported function safely.
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[`instantiate`]: https://docs.rs/wasmer-runtime/*/wasmer_runtime/fn.instantiate.html
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[`Instance`]: https://docs.rs/wasmer-runtime/*/wasmer_runtime/struct.Instance.html
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[`call`]: https://docs.rs/wasmer-runtime/*/wasmer_runtime/struct.Instance.html#method.call
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[`func`]: https://docs.rs/wasmer-runtime/*/wasmer_runtime/struct.Instance.html#method.func
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[func.call]: https://docs.rs/wasmer-runtime/*/wasmer_runtime/struct.Function.html#method.call
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## Here's an example:
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Given this WebAssembly:
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```wat
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(module
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(type $t0 (func (param i32) (result i32)))
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(func $add_one (export "add_one") (type $t0) (param $p0 i32) (result i32)
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get_local $p0
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i32.const 1
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i32.add))
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```
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compiled into wasm bytecode, we can call the exported "add_one" function:
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```rust
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static WASM: &'static [u8] = &[
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// The module above compiled to bytecode goes here.
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0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00, 0x01, 0x06, 0x01, 0x60,
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0x01, 0x7f, 0x01, 0x7f, 0x03, 0x02, 0x01, 0x00, 0x07, 0x0b, 0x01, 0x07,
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0x61, 0x64, 0x64, 0x5f, 0x6f, 0x6e, 0x65, 0x00, 0x00, 0x0a, 0x09, 0x01,
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0x07, 0x00, 0x20, 0x00, 0x41, 0x01, 0x6a, 0x0b, 0x00, 0x1a, 0x04, 0x6e,
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0x61, 0x6d, 0x65, 0x01, 0x0a, 0x01, 0x00, 0x07, 0x61, 0x64, 0x64, 0x5f,
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0x6f, 0x6e, 0x65, 0x02, 0x07, 0x01, 0x00, 0x01, 0x00, 0x02, 0x70, 0x30,
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];
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use wasmer_runtime::{
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instantiate,
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Value,
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imports,
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error,
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};
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fn main() -> error::Result<()> {
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// We're not importing anything, so make an empty import object.
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let import_object = imports! {};
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2019-02-26 23:39:54 +00:00
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let mut instance = instantiate(WASM, &import_object)?;
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2019-01-24 18:51:20 +00:00
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let values = instance
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.func("add_one")?
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.call(&[Value::I32(42)])?;
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assert_eq!(values[0], Value::I32(43));
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Ok(())
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}
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```
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# Additional Notes:
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The `wasmer-runtime` is build to support compiler multiple backends.
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Currently, we support the [Cranelift] compiler with the [`wasmer-clif-backend`] crate.
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You can specify the compiler you wish to use with the [`compile_with`] function.
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[Cranelift]: https://github.com/CraneStation/cranelift
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[`wasmer-clif-backend`]: https://crates.io/crates/wasmer-clif-backend
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[`compile_with`]: https://docs.rs/wasmer-runtime/*/wasmer_runtime/fn.compile_with.html
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