clean up wasi fs public api changes

CHANGELOG.md

@@ -5,6 +5,7 @@ All PRs to the Wasmer repository must add to this file.
 Blocks of changes will separated by version increments.
 
 ## **[Unreleased]**
+- [#595](https://github.com/wasmerio/wasmer/pull/595) Add unstable public API for interfacing with the WASI file system in plugin-like usecases
 - [#579](https://github.com/wasmerio/wasmer/pull/579) Fix bug in caching with LLVM and Singlepass backends.
   Add `default-backend-singlepass`, `default-backend-llvm`, and `default-backend-cranelift` features to `wasmer-runtime`
   to control the `default_compiler()` function (this is a breaking change).  Add `compiler_for_backend` function in `wasmer-runtime`

lib/wasi/src/lib.rs

@@ -6,11 +6,12 @@ extern crate winapi;
 #[macro_use]
 mod macros;
 mod ptr;
-mod state;
+pub mod state;
 mod syscalls;
 mod utils;
 
 use self::state::{WasiFs, WasiState};
+pub use self::syscalls::types;
 use self::syscalls::*;
 
 use std::ffi::c_void;

lib/wasi/src/state.rs

@@ -1,3 +1,6 @@
+//! WARNING: the API exposed here is unstable and very experimental.  Certain thins will not
+//! yet and may be broken in patch releases.  If you're using this and have any specific needs,
+//! please let us know here https://github.com/wasmerio/wasmer/issues/583 or by filing an issue.
 // use wasmer_runtime_abi::vfs::{
 //     vfs::Vfs,
 //     file_like::{FileLike, Metadata};
@@ -14,7 +17,12 @@ use std::{
     path::{Path, PathBuf},
     time::SystemTime,
 };
-use wasmer_runtime_core::debug;
+use wasmer_runtime_core::{debug, vm::Ctx};
+
+/// Get WasiState from a Ctx
+pub unsafe fn get_wasi_state(ctx: &mut Ctx) -> &mut WasiState {
+    &mut *(ctx.data as *mut WasiState)
+}
 
 /// A completely aribtrary "big enough" number used as the upper limit for
 /// the number of symlinks that can be traversed when resolving a path
@@ -54,8 +62,6 @@ impl WasiFsError {
 }
 
 /// This trait relies on your file closing when it goes out of scope via `Drop`
-/// it does not require `Drop` because `std::fs::File` does not implement it
-/// (TODO: figure out how that makes sense, because it clearly does)
 pub trait WasiFile: std::fmt::Debug + Write + Read + Seek {
     /// the last time the file was accessed in nanoseconds as a UNIX timestamp
     fn last_accessed(&self) -> u64;
@@ -392,6 +398,8 @@ pub struct Fd {
 }
 
 #[derive(Debug)]
+/// Warning, modifying these fields directly may cause invariants to break and
+/// should be considered unsafe.  These fields may be made private in a future release
 pub struct WasiFs {
     //pub repo: Repo,
     pub preopen_fds: Vec<u32>,
@@ -875,9 +883,9 @@ impl WasiFs {
 
     pub fn flush(&mut self, fd: __wasi_fd_t) -> Result<(), __wasi_errno_t> {
         match fd {
-            0 => (),
-            1 => io::stdout().flush().map_err(|_| __WASI_EIO)?,
-            2 => io::stderr().flush().map_err(|_| __WASI_EIO)?,
+            __WASI_STDIN_FILENO => (),
+            __WASI_STDOUT_FILENO => self.stdout.flush().map_err(|_| __WASI_EIO)?,
+            __WASI_STDERR_FILENO => self.stderr.flush().map_err(|_| __WASI_EIO)?,
             _ => {
                 let fd = self.fd_map.get(&fd).ok_or(__WASI_EBADF)?;
                 if fd.rights & __WASI_RIGHT_FD_DATASYNC == 0 {
@@ -926,7 +934,7 @@ impl WasiFs {
         rights_inheriting: __wasi_rights_t,
         flags: __wasi_fdflags_t,
         inode: Inode,
-    ) -> Result<u32, __wasi_errno_t> {
+    ) -> Result<__wasi_fd_t, __wasi_errno_t> {
         let idx = self.next_fd.get();
         self.next_fd.set(idx + 1);
         self.fd_map.insert(

lib/wasi/src/syscalls/mod.rs

@@ -9,7 +9,7 @@ use self::types::*;
 use crate::{
     ptr::{Array, WasmPtr},
     state::{
-        host_file_type_to_wasi_file_type, Fd, Inode, InodeVal, Kind, WasiFile, WasiState,
+        self, host_file_type_to_wasi_file_type, Fd, Inode, InodeVal, Kind, WasiFile, WasiState,
         MAX_SYMLINKS,
     },
     ExitCode,
@@ -27,9 +27,10 @@ pub use unix::*;
 #[cfg(any(target_os = "windows"))]
 pub use windows::*;
 
+/// This function is not safe
 #[allow(clippy::mut_from_ref)]
-fn get_wasi_state(ctx: &Ctx) -> &mut WasiState {
-    unsafe { &mut *(ctx.data as *mut WasiState) }
+pub(crate) fn get_wasi_state(ctx: &Ctx) -> &mut WasiState {
+    unsafe { state::get_wasi_state(&mut *(ctx as *const Ctx as *mut Ctx)) }
 }
 
 fn write_bytes<T: Write>(