efe7f37542
This commit deletes the old `snapshot_0` implementation of wasi-common, along with the `wig` crate that was used to generate bindings for it. This then reimplements `snapshot_0` in terms of `wasi_snapshot_preview1`. There were very few changes between the two snapshots: * The `nlink` field of `FileStat` was increased from 32 to 64 bits. * The `set` field of `whence` was reordered. * Clock subscriptions in polling dropped their redundant userdata field. This makes all of the syscalls relatively straightforward to simply delegate to the next snapshot's implementation. Some trickery happens to avoid extra cost when dealing with iovecs, but since the memory layout of iovecs remained the same this should still work. Now that `snapshot_0` is using wiggle we simply have a trait to implement, and that's implemented for the same `WasiCtx` that has the `wasi_snapshot_preview1` trait implemented for it as well. While this theoretically means that you could share the file descriptor table between the two snapshots that's not supported in the generated bindings just yet. A separate `WasiCtx` will be created for each WASI module.
This is the wasmtime-wasi crate, which implements the
WebAssembly System Interface (WASI) API in Rust.
WASI is greatly inspired by and directly derived from CloudABI. It differs in that it has aspirations to expand to a greater scope, and to better support the needs of WebAssembly engines.