From 0550c2117480d4e2dd4b7b58c7ac3784f6938e36 Mon Sep 17 00:00:00 2001
From: Gaelan Steele <gbs@canishe.com>
Date: Mon, 21 Dec 2020 01:26:29 -0800
Subject: [PATCH 1/2] Use TryInto to avoid unsafe.

Previously, to_fields and to_fields_le used unsafe to convert a
&[u8] into a &[u8; 8]. Now that we're only supporting Rust
versions where TryInto is stable, we can use try_into().unwrap()
instead, making uuid entirely safe Rust.

In release mode, the compiler detects that the slice will always
be the correct size, so try_into can never fail. Thus, the unwrap
is optimized out and we end up with the exact same assembly
as the unsafe block.

Godbolt output showing the resulting assembly:
https://godbolt.org/z/nWxT6W

Closes #488.
---
 src/lib.rs | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index fe57353f8..c18ea949d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -198,7 +198,7 @@ mod v5;
 #[cfg(all(windows, feature = "winapi"))]
 mod winapi_support;
 
-use crate::std::{fmt, str};
+use crate::std::{convert::TryInto, fmt, str};
 
 pub use crate::error::Error;
 
@@ -390,8 +390,7 @@ impl Uuid {
         let d3 =
             u16::from(self.as_bytes()[6]) << 8 | u16::from(self.as_bytes()[7]);
 
-        let d4: &[u8; 8] =
-            unsafe { &*(self.as_bytes()[8..16].as_ptr() as *const [u8; 8]) };
+        let d4: &[u8; 8] = self.as_bytes()[8..16].try_into().unwrap();
         (d1, d2, d3, d4)
     }
 
@@ -431,8 +430,7 @@ impl Uuid {
         let d3 =
             u16::from(self.as_bytes()[6]) | u16::from(self.as_bytes()[7]) << 8;
 
-        let d4: &[u8; 8] =
-            unsafe { &*(self.as_bytes()[8..16].as_ptr() as *const [u8; 8]) };
+        let d4: &[u8; 8] = self.as_bytes()[8..16].try_into().unwrap();
         (d1, d2, d3, d4)
     }
 

From f93a2ada47c1392aa81a1ad41ec5011280423bb5 Mon Sep 17 00:00:00 2001
From: Gaelan Steele <gbs@canishe.com>
Date: Mon, 4 Jan 2021 13:56:27 -0800
Subject: [PATCH 2/2] Remove TryFrom import.

---
 src/lib.rs | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index c18ea949d..c77dad634 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -198,7 +198,7 @@ mod v5;
 #[cfg(all(windows, feature = "winapi"))]
 mod winapi_support;
 
-use crate::std::{convert::TryInto, fmt, str};
+use crate::std::{convert, fmt, str};
 
 pub use crate::error::Error;
 
@@ -390,7 +390,8 @@ impl Uuid {
         let d3 =
             u16::from(self.as_bytes()[6]) << 8 | u16::from(self.as_bytes()[7]);
 
-        let d4: &[u8; 8] = self.as_bytes()[8..16].try_into().unwrap();
+        let d4: &[u8; 8] =
+            convert::TryInto::try_into(&self.as_bytes()[8..16]).unwrap();
         (d1, d2, d3, d4)
     }
 
@@ -430,7 +431,8 @@ impl Uuid {
         let d3 =
             u16::from(self.as_bytes()[6]) | u16::from(self.as_bytes()[7]) << 8;
 
-        let d4: &[u8; 8] = self.as_bytes()[8..16].try_into().unwrap();
+        let d4: &[u8; 8] =
+            convert::TryInto::try_into(&self.as_bytes()[8..16]).unwrap();
         (d1, d2, d3, d4)
     }