From c12d7f2ab11133302892a48dd3b47b67cb790952 Mon Sep 17 00:00:00 2001
From: William Brown <william@blackhats.net.au>
Date: Thu, 30 May 2024 15:35:34 +1000
Subject: [PATCH] Allow an inplace update to prevent a clone

---
 Cargo.toml            | 2 +-
 src/cowcell/asynch.rs | 6 ++++++
 src/cowcell/mod.rs    | 7 ++++++-
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index a4d6e0e..ccaafbe 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "concread"
-version = "0.5.0"
+version = "0.5.1"
 authors = ["William Brown <william@blackhats.net.au>"]
 edition = "2021"
 description = "Concurrently Readable Data-Structures for Rust"
diff --git a/src/cowcell/asynch.rs b/src/cowcell/asynch.rs
index bfa3504..de3794f 100644
--- a/src/cowcell/asynch.rs
+++ b/src/cowcell/asynch.rs
@@ -157,6 +157,12 @@ where
         self.work.as_mut().expect("can not fail")
     }
 
+    /// Update the inner value with a new one. This function exists to prevent a clone
+    /// in the case where you take a read transaction and would otherwise use `mem::swap`
+    pub fn replace(&mut self, value: T) {
+        self.work = Some(value);
+    }
+
     /// Commit the changes made in this write transactions to the `CowCell`.
     /// This will consume the transaction so no further changes can be made
     /// after this is called. Not calling this in a block, is equivalent to
diff --git a/src/cowcell/mod.rs b/src/cowcell/mod.rs
index 125d1d0..7cd451e 100644
--- a/src/cowcell/mod.rs
+++ b/src/cowcell/mod.rs
@@ -179,7 +179,6 @@ where
     /// Access a mutable pointer of the data in the `CowCell`. This data is only
     /// visible to the write transaction object in this thread, until you call
     /// `commit()`.
-    #[inline(always)]
     pub fn get_mut(&mut self) -> &mut T {
         if self.work.is_none() {
             let mut data: Option<T> = Some((*self.read).clone());
@@ -190,6 +189,12 @@ where
         self.work.as_mut().expect("can not fail")
     }
 
+    /// Update the inner value with a new one. This function exists to prevent a clone
+    /// in the case where you take a read transaction and would otherwise use `mem::swap`
+    pub fn replace(&mut self, value: T) {
+        self.work = Some(value);
+    }
+
     /// Commit the changes made in this write transactions to the `CowCell`.
     /// This will consume the transaction so no further changes can be made
     /// after this is called. Not calling this in a block, is equivalent to