From 3e143217a9f093f048680cb60406d24b5c21c5f8 Mon Sep 17 00:00:00 2001
From: Wim Hueskes <rust@wimhueskes.eu>
Date: Thu, 21 Jul 2016 10:20:42 +0200
Subject: [PATCH] od: refactor sign_extend

easier to understand algoritm which does not use unsafe
---
 src/od/od.rs | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/src/od/od.rs b/src/od/od.rs
index f09cb8134..39a09964d 100644
--- a/src/od/od.rs
+++ b/src/od/od.rs
@@ -424,14 +424,8 @@ fn print_item_hex(p: u64, itembytes: usize) {
 
 
 fn sign_extend(item: u64, itembytes: usize) -> i64{
-	// https://graphics.stanford.edu/~seander/bithacks.html#VariableSignExtend
-	unsafe{
-		let b = 8 * itembytes; // number of bits representing the number in p
-		let m =  mem::transmute::<u64,i64>(1u64 << (b - 1));
-		let x =  mem::transmute::<u64,i64>(item) & (mem::transmute::<u64,i64>(1u64 << b) - 1);
-		let r = (x ^ m) - m;
-		r
-	}
+    let shift = 64 - itembytes * 8;
+    (item << shift) as i64 >> shift
 }