scanner/entry: a custom Ord Token wrapper

A TokenEntry is designed as a wrapper for Tokens returned from the
Scanner, ensuring that they are returned from the Queue in an order that
mirrors where in the buffer the token was read.

This will allow me to push Tokens out of order particularly when
handling Keys and still have them returned in the expected order

src/scanner/entry.rs

@@ -0,0 +1,59 @@
+use std::cmp::Ordering;
+
+use crate::token::Token;
+
+/// A wrapper around a token containing a custom Ord impl
+/// based on the token's position in the buffer.
+///
+/// Note that this wrapper *does not* compare tokens, so if
+/// you desire that ensure that you compare them directly
+#[derive(Debug)]
+pub(crate) struct TokenEntry<'de>
+{
+    pub token: Token<'de>,
+    read_at:   usize,
+}
+
+impl<'de> TokenEntry<'de>
+{
+    pub fn new(token: Token<'de>, read_at: usize) -> Self
+    {
+        Self { token, read_at }
+    }
+
+    pub fn read_at(&self) -> usize
+    {
+        self.read_at
+    }
+
+    pub fn into_token(self) -> Token<'de>
+    {
+        self.token
+    }
+}
+
+impl<'de> PartialEq for TokenEntry<'de>
+{
+    fn eq(&self, other: &Self) -> bool
+    {
+        self.read_at.eq(&other.read_at)
+    }
+}
+
+impl<'de> Eq for TokenEntry<'de> {}
+
+impl<'de> PartialOrd for TokenEntry<'de>
+{
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering>
+    {
+        Some(self.cmp(other))
+    }
+}
+
+impl<'de> Ord for TokenEntry<'de>
+{
+    fn cmp(&self, other: &Self) -> Ordering
+    {
+        self.read_at.cmp(&other.read_at)
+    }
+}

src/scanner/mod.rs

@@ -4,6 +4,7 @@
 mod macros;
 
 mod context;
+mod entry;
 mod error;
 mod key;
 mod scalar;