From 7beb52a2bc6023bc83cb1cb54be2b3b663f29cd3 Mon Sep 17 00:00:00 2001
From: Pat Hickey <pat@moreproductive.org>
Date: Wed, 13 Jan 2021 14:23:59 -0800
Subject: [PATCH] i guess this is a way to do refs

---
 crates/wasi-c2/src/file.rs                | 25 +++++++++++++++--------
 crates/wasi-c2/src/snapshots/preview_1.rs |  2 +-
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/crates/wasi-c2/src/file.rs b/crates/wasi-c2/src/file.rs
index 73d7a3abc5..03393f478d 100644
--- a/crates/wasi-c2/src/file.rs
+++ b/crates/wasi-c2/src/file.rs
@@ -1,6 +1,7 @@
 use crate::Error;
 use bitflags::bitflags;
 use fs_set_times::SetTimes;
+use std::cell::Ref;
 use std::ops::Deref;
 use system_interface::fs::FileIoExt;
 
@@ -92,9 +93,9 @@ impl FileEntry {
         FileEntry { caps, file }
     }
 
-    pub fn get_cap(&self, caps: FileCaps) -> Result<&dyn WasiFile, Error> {
+    pub fn capable_of(&self, caps: FileCaps) -> Result<(), Error> {
         if self.caps.contains(caps) {
-            Ok(self.file.deref())
+            Ok(())
         } else {
             Err(Error::FileNotCapable {
                 desired: caps,
@@ -104,12 +105,9 @@ impl FileEntry {
     }
 
     pub fn drop_caps_to(&mut self, caps: FileCaps) -> Result<(), Error> {
-        if self.caps.contains(caps) {
-            self.caps = caps;
-            Ok(())
-        } else {
-            Err(Error::NotCapable)
-        }
+        self.capable_of(caps)?;
+        self.caps = caps;
+        Ok(())
     }
 
     pub fn get_fdstat(&self) -> Result<FdStat, Error> {
@@ -121,6 +119,17 @@ impl FileEntry {
     }
 }
 
+pub trait FileEntryExt<'a> {
+    fn get_cap(self, caps: FileCaps) -> Result<Ref<'a, dyn WasiFile>, Error>;
+}
+
+impl<'a> FileEntryExt<'a> for Ref<'a, FileEntry> {
+    fn get_cap(self, caps: FileCaps) -> Result<Ref<'a, dyn WasiFile>, Error> {
+        self.capable_of(caps)?;
+        Ok(Ref::map(self, |r| r.file.deref()))
+    }
+}
+
 bitflags! {
     pub struct FileCaps : u32 {
         const DATASYNC           = 0b1;
diff --git a/crates/wasi-c2/src/snapshots/preview_1.rs b/crates/wasi-c2/src/snapshots/preview_1.rs
index 91ae2610b2..13fe6d307a 100644
--- a/crates/wasi-c2/src/snapshots/preview_1.rs
+++ b/crates/wasi-c2/src/snapshots/preview_1.rs
@@ -1,6 +1,6 @@
 #![allow(unused_variables)]
 use crate::dir::{DirCaps, DirEntry, DirFdStat, ReaddirCursor, ReaddirEntity, TableDirExt};
-use crate::file::{FdFlags, FdStat, FileCaps, FileEntry, FileType, Filestat, OFlags};
+use crate::file::{FdFlags, FdStat, FileCaps, FileEntry, FileEntryExt, FileType, Filestat, OFlags};
 use crate::sched::subscription::{RwEventFlags, SubscriptionResult};
 use crate::sched::Poll;
 use crate::{Error, WasiCtx};