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wasm-bindgen/crates/anyref-xform/Cargo.toml

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Add experimental support for the `anyref` type This commit adds experimental support to `wasm-bindgen` to emit and leverage the `anyref` native wasm type. This native type is still in a proposal status (the reference-types proposal). The intention of `anyref` is to be able to directly hold JS values in wasm and pass the to imported functions, namely to empower eventual host bindings (now renamed WebIDL bindings) integration where we can skip JS shims altogether for many imports. This commit doesn't actually affect wasm-bindgen's behavior at all as-is, but rather this support requires an opt-in env var to be configured. Once the support is stable in browsers it's intended that this will add a CLI switch for turning on this support, eventually defaulting it to `true` in the far future. The basic strategy here is to take the `stack` and `slab` globals in the generated JS glue and move them into wasm using a table. This new table in wasm is managed at the fringes via injected shims. At `wasm-bindgen`-time the CLI will rewrite exports and imports with shims that actually use `anyref` if needed, performing loads/stores inside the wasm module instead of externally in the wasm module. This should provide a boost over what we have today, but it's not a fantastic strategy long term. We have a more grand vision for `anyref` being a first-class type in the language, but that's on a much longer horizon and this is currently thought to be the best we can do in terms of integration in the near future. The stack/heap JS tables are combined into one wasm table. The stack starts at the end of the table and grows down with a stack pointer (also injected). The heap starts at the end and grows up (state managed in linear memory). The anyref transformation here will hook up various intrinsics in wasm-bindgen to the runtime functionality if the anyref supoprt is enabled. The main tricky treatment here was applied to closures, where we need JS to use a different function pointer than the one Rust gives it to use a JS function pointer empowered with anyref. This works by switching up a bit how descriptors work, embedding the shims to call inside descriptors rather than communicated at runtime. This means that we're accessing constant values in the generated JS and we can just update the constant value accessed.
2018-10-18 08:43:36 -07:00
[package]
name = "wasm-bindgen-anyref-xform"
version = "0.2.37"
authors = ["The wasm-bindgen Developers"]
license = "MIT/Apache-2.0"
repository = "https://github.com/rustwasm/wasm-bindgen/tree/master/crates/anyref-xform"
homepage = "https://rustwasm.github.io/wasm-bindgen/"
documentation = "https://docs.rs/wasm-bindgen-anyref-xform"
description = """
Internal anyref transformations for wasm-bindgen
"""
edition = '2018'
[dependencies]
failure = "0.1"
walrus = "0.4"
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