codec: rewrite of codec::Framed (#2368)

Framed was designed to encapsulate both AsyncRead and AsyncWrite so
that it could wrap two-way connections. It used Fuse to manage the pinned
io object between the FramedWrite and FramedRead structs.

I replaced the Fuse struct by isolating the state used in reading and
writing, and making the code generic over that instead. This means
the FramedImpl struct now has a parameter for the state, and contains
the logic for both directions. The Framed* structs are now simply
wrappers around this type

Hopefully removing the `Pin` handling made things easier to
understand, too.

1 files changed, 6 insertions, 0 deletions

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index b338838e..772b1dce 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -132,9 +132,15 @@ RUSTDOCFLAGS="--cfg docsrs" cargo +nightly doc --all-features
 ```
 The `cargo fmt` command does not work on the Tokio codebase. You can use the
 command below instead:
+
+#### Bash
 ```
 rustfmt --check --edition 2018 $(find . -name '*.rs' -print)
 ```
+#### Powershell
+```
+Get-ChildItem . -Filter "*.rs" -Recurse | foreach { rustfmt --check --edition 2018 $_.FullName }
+```
 The `--check` argument prints the things that need to be fixed. If you remove
 it, `rustfmt` will update your files locally instead.