Method preopened_dir

crates/wasi/src/ctx.rs:300–326

Configures a "preopened directory" to be available to WebAssembly. By default WebAssembly does not have access to the filesystem because there are no preopened directories. All filesystem operations, such as opening a file, are done through a preexisting handle. This means that to provide WebAssembly access to a directory it must be configured through this API. WASI will also prevent access outs

(
        &mut self,
        host_path: impl AsRef<Path>,
        guest_path: impl AsRef<str>,
        dir_perms: DirPerms,
        file_perms: FilePerms,
    )

    /// # }
    /// ```
    pub fn preopened_dir(
        &mut self,
        host_path: impl AsRef<Path>,
        guest_path: impl AsRef<str>,
        dir_perms: DirPerms,
        file_perms: FilePerms,
    ) -> Result<&mut Self> {
        let dir = cap_std::fs::Dir::open_ambient_dir(host_path.as_ref(), ambient_authority())?;
        let mut open_mode = OpenMode::empty();
        if dir_perms.contains(DirPerms::READ) {
            open_mode |= OpenMode::READ;
        }
        if dir_perms.contains(DirPerms::MUTATE) {
            open_mode |= OpenMode::WRITE;
        }
        self.filesystem.preopens.push((
            Dir::new(
                dir,
                dir_perms,
                file_perms,
                open_mode,
                self.filesystem.allow_blocking_current_thread,
            ),
            guest_path.as_ref().to_owned(),
        ));
        Ok(self)
    }

    /// Set the generator for the `wasi:random/random` number generator to the
    /// custom generator specified.