From a8207cfdd970f49747afb58ccb2750c1402e88d1 Mon Sep 17 00:00:00 2001
From: Nilstrieb <48135649+Nilstrieb@users.noreply.github.com>
Date: Tue, 5 Apr 2022 19:46:49 +0200
Subject: [PATCH] adaptors

---
 .rustfmt.toml   |  3 +++
 src/strategy.rs | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+)
 create mode 100644 .rustfmt.toml
 create mode 100644 src/strategy.rs

diff --git a/.rustfmt.toml b/.rustfmt.toml
new file mode 100644
index 0000000..4d7dd9e
--- /dev/null
+++ b/.rustfmt.toml
@@ -0,0 +1,3 @@
+imports_granularity = "Crate"
+newline_style = "Unix"
+group_imports = "StdExternalCrate"
\ No newline at end of file
diff --git a/src/strategy.rs b/src/strategy.rs
new file mode 100644
index 0000000..aba4950
--- /dev/null
+++ b/src/strategy.rs
@@ -0,0 +1,46 @@
+use core::marker::PhantomData;
+
+use stuff::Backend;
+
+pub trait SafeStuffingStrategy<B> {
+    type Extra;
+
+    fn stuff_extra(extra: &Self::Extra) -> B;
+
+    fn extract_extra(addr: B) -> Option<Self::Extra>;
+}
+
+/// An internal type to convert from the safe to the unsafe trait
+pub(crate) struct SafeStrategyAdaptor<S>(PhantomData<S>);
+
+// SAFETY: `extract_extra` panics if an invalid extra is returned
+//         `stuff_extra` never drops the extra
+//         pointer stuffing is just identity
+unsafe impl<S, B> stuff::StuffingStrategy<B> for SafeStrategyAdaptor<S>
+where
+    S: SafeStuffingStrategy<B>,
+{
+    type Extra = S::Extra;
+
+    fn is_extra(data: B) -> bool {
+        S::extract_extra(data).is_some()
+    }
+
+    fn stuff_extra(inner: Self::Extra) -> B {
+        let b = S::stuff_extra(&inner);
+        core::mem::forget(inner);
+        b
+    }
+
+    unsafe fn extract_extra(data: B) -> Self::Extra {
+        S::extract_extra(data).unwrap()
+    }
+
+    fn stuff_ptr(addr: usize) -> B {
+        addr
+    }
+
+    fn extract_ptr(inner: B) -> usize {
+        inner
+    }
+}