Initial reorg.

This is largely the same as #305, but updated for the current tree.

crates/wasi-common/src/fs/file.rs

@@ -0,0 +1,107 @@
+use crate::fs::{error::wasi_errno_to_io_error, Metadata};
+use crate::{host, hostcalls, wasi, WasiCtx};
+use std::io;
+
+/// A reference to an open file on the filesystem.
+///
+/// This corresponds to [`std::fs::File`].
+///
+/// Note that this `File` has no `open` or `create` methods. To open or create
+/// a file, you must first obtain a [`Dir`] containing the file, and then call
+/// [`Dir::open_file`] or [`Dir::create_file`].
+///
+/// [`std::fs::File`]: https://doc.rust-lang.org/std/fs/struct.File.html
+/// [`Dir`]: struct.Dir.html
+/// [`Dir::open_file`]: struct.Dir.html#method.open_file
+/// [`Dir::create_file`]: struct.Dir.html#method.create_file
+pub struct File<'ctx> {
+    ctx: &'ctx mut WasiCtx,
+    fd: wasi::__wasi_fd_t,
+}
+
+impl<'ctx> File<'ctx> {
+    /// Constructs a new instance of `Self` from the given raw WASI file descriptor.
+    ///
+    /// This corresponds to [`std::fs::File::from_raw_fd`].
+    ///
+    /// [`std::fs::File::from_raw_fd`]: https://doc.rust-lang.org/std/fs/struct.File.html#method.from_raw_fd
+    pub unsafe fn from_raw_wasi_fd(ctx: &'ctx mut WasiCtx, fd: wasi::__wasi_fd_t) -> Self {
+        Self { ctx, fd }
+    }
+
+    /// Attempts to sync all OS-internal metadata to disk.
+    ///
+    /// This corresponds to [`std::fs::File::sync_all`].
+    ///
+    /// [`std::fs::File::sync_all`]: https://doc.rust-lang.org/std/fs/struct.File.html#method.sync_all
+    pub fn sync_all(&self) -> io::Result<()> {
+        wasi_errno_to_io_error(unsafe { hostcalls::fd_sync(self.ctx, self.fd) })
+    }
+
+    /// This function is similar to `sync_all`, except that it may not synchronize
+    /// file metadata to the filesystem.
+    ///
+    /// This corresponds to [`std::fs::File::sync_data`].
+    ///
+    /// [`std::fs::File::sync_data`]: https://doc.rust-lang.org/std/fs/struct.File.html#method.sync_data
+    pub fn sync_data(&self) -> io::Result<()> {
+        wasi_errno_to_io_error(unsafe { hostcalls::fd_datasync(self.ctx, self.fd) })
+    }
+
+    /// Truncates or extends the underlying file, updating the size of this file
+    /// to become size.
+    ///
+    /// This corresponds to [`std::fs::File::set_len`].
+    ///
+    /// [`std::fs::File::set_len`]: https://doc.rust-lang.org/std/fs/struct.File.html#method.set_len
+    pub fn set_len(&self, size: u64) -> io::Result<()> {
+        wasi_errno_to_io_error(unsafe { hostcalls::fd_filestat_set_size(self.ctx, self.fd, size) })
+    }
+
+    /// Queries metadata about the underlying file.
+    ///
+    /// This corresponds to [`std::fs::File::metadata`].
+    ///
+    /// [`std::fs::File::metadata`]: https://doc.rust-lang.org/std/fs/struct.File.html#method.metadata
+    pub fn metadata(&self) -> io::Result<Metadata> {
+        Ok(Metadata {})
+    }
+}
+
+impl<'ctx> Drop for File<'ctx> {
+    fn drop(&mut self) {
+        // Note that errors are ignored when closing a file descriptor. The
+        // reason for this is that if an error occurs we don't actually know if
+        // the file descriptor was closed or not, and if we retried (for
+        // something like EINTR), we might close another valid file descriptor
+        // opened after we closed ours.
+        let _ = unsafe { hostcalls::fd_close(self.ctx, self.fd) };
+    }
+}
+
+impl<'ctx> io::Read for File<'ctx> {
+    /// TODO: Not yet implemented. See the comment in `Dir::open_file`.
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        let iov = [host::__wasi_iovec_t {
+            buf: buf.as_mut_ptr() as *mut u8,
+            buf_len: buf.len(),
+        }];
+        let mut nread = 0;
+
+        // TODO: See the comment in `Dir::open_file`.
+        unimplemented!("File::read");
+        /*
+        wasi_errno_to_io_error(unsafe {
+            hostcalls::fd_read(self.ctx, self.fd, &iov, 1, &mut nread)
+        })?;
+        */
+
+        Ok(nread)
+    }
+}
+
+// TODO: traits to implement: Write, Seek
+
+// TODO: functions from FileExt?
+
+// TODO: impl Debug for File