From 1cc4ec4d25faa8b8f6b5838c28de1282283b0432 Mon Sep 17 00:00:00 2001
From: Armin Ronacher <armin.ronacher@active-4.com>
Date: Sat, 20 Feb 2021 15:51:45 +0100
Subject: [PATCH] Refactor to add a is_empty_range function

---
 src/algorithms/lcs.rs   | 5 +++--
 src/algorithms/myers.rs | 9 +++++----
 src/utils.rs            | 6 ++++++
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/src/algorithms/lcs.rs b/src/algorithms/lcs.rs
index 206e115..6c60c1f 100644
--- a/src/algorithms/lcs.rs
+++ b/src/algorithms/lcs.rs
@@ -7,6 +7,7 @@ use std::ops::{Index, Range};
 use std::time::Instant;
 
 use crate::algorithms::DiffHook;
+use crate::utils::is_empty_range;
 
 /// Hunt–McIlroy / Hunt–Szymanski LCS diff algorithm.
 ///
@@ -52,10 +53,10 @@ where
     D: DiffHook,
     New::Output: PartialEq<Old::Output>,
 {
-    if new_range.start >= new_range.end {
+    if is_empty_range(&new_range) {
         d.delete(old_range.start, old_range.len(), new_range.start)?;
         return Ok(());
-    } else if old_range.start >= old_range.end {
+    } else if is_empty_range(&old_range) {
         d.insert(old_range.start, new_range.start, new_range.len())?;
         return Ok(());
     }
diff --git a/src/algorithms/myers.rs b/src/algorithms/myers.rs
index 7432eee..c3117dd 100644
--- a/src/algorithms/myers.rs
+++ b/src/algorithms/myers.rs
@@ -23,6 +23,7 @@ use std::ops::{Index, IndexMut, Range};
 use std::time::Instant;
 
 use crate::algorithms::DiffHook;
+use crate::utils::is_empty_range;
 
 /// Myers' diff algorithm.
 ///
@@ -171,7 +172,7 @@ where
     New: Index<usize> + ?Sized,
     New::Output: PartialEq<Old::Output>,
 {
-    if old_range.start >= old_range.end || new_range.start >= new_range.end {
+    if is_empty_range(&old_range) || is_empty_range(&new_range) {
         return 0;
     }
     new_range
@@ -352,15 +353,15 @@ where
     old_range.end -= common_suffix_len;
     new_range.end -= common_suffix_len;
 
-    if old_range.start >= old_range.end && new_range.start >= new_range.end {
+    if is_empty_range(&old_range) && is_empty_range(&new_range) {
         // Do nothing
-    } else if new_range.start >= new_range.end {
+    } else if is_empty_range(&new_range) {
         d.delete(
             old_range.start,
             old_range.end - old_range.start,
             new_range.start,
         )?;
-    } else if old_range.start >= old_range.end {
+    } else if is_empty_range(&old_range) {
         d.insert(
             old_range.start,
             new_range.start,
diff --git a/src/utils.rs b/src/utils.rs
index 1f8fdc9..55708d6 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -401,6 +401,12 @@ pub fn diff_lines<'x, T: DiffableStrRef + ?Sized>(
         .collect()
 }
 
+/// Utility function to check if a range is empty that works on older rust versions
+#[inline(always)]
+pub(crate) fn is_empty_range<T: PartialOrd>(range: &Range<T>) -> bool {
+    !(range.start < range.end)
+}
+
 #[test]
 fn test_remapper() {
     let a = "foo bar baz";