From c54e5531aaa98846cb4bec96cf9fce1435bf54bd Mon Sep 17 00:00:00 2001
From: Nilstrieb <48135649+Nilstrieb@users.noreply.github.com>
Date: Sun, 10 Apr 2022 15:06:37 +0200
Subject: [PATCH] add pointer tag

---
 Cargo.toml |  2 --
 src/lib.rs |  1 +
 src/tag.rs | 17 +++++++++++++++++
 3 files changed, 18 insertions(+), 2 deletions(-)
 create mode 100644 src/tag.rs

diff --git a/Cargo.toml b/Cargo.toml
index e538c8e..295200f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,8 +13,6 @@ categories = ["data-structures", "memory-management", "no-std"]
 include = ["Cargo.toml", "LICENSE", "src", "README.md"]
 rust-version = "1.34.2"
 
-# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
-
 [dependencies]
 sptr = "0.3.1"
 
diff --git a/src/lib.rs b/src/lib.rs
index a7b72a5..4f35c92 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -92,6 +92,7 @@ extern crate alloc; // we want that for tests so we can use `Box`
 
 mod backend;
 mod strategy;
+mod tag;
 
 use core::{
     fmt::{Debug, Formatter},
diff --git a/src/tag.rs b/src/tag.rs
new file mode 100644
index 0000000..858d362
--- /dev/null
+++ b/src/tag.rs
@@ -0,0 +1,17 @@
+use core::marker::PhantomData;
+
+use crate::Backend;
+
+pub struct TaggedPtr<T, S, B = usize>(B::Stored, PhantomData<S>)
+where
+    B: Backend<T>;
+
+pub trait TaggingStrategy<B> {
+    type Tag;
+
+    fn get_tag(data: B) -> Self::Tag;
+
+    fn get_ptr_addr(data: B) -> usize;
+
+    fn set(addr: usize, tag: Self::Tag) -> B;
+}