From 1f0a0259a4fd69b375e7a1baf6d41f356a7bddc5 Mon Sep 17 00:00:00 2001
From: Andrew Gallant <jamslam@gmail.com>
Date: Sat, 20 May 2017 10:04:45 -0400
Subject: [PATCH] compiler: fix a byte class bug

The code that computes the byte classes had a bug that was only tripped
when the maximum number of equivalence classes was necessary (256). This
commit fixes that by rewriting the loop such that we never uselessly
increment outside the bounds of `u8`.

Fixes #367
---
 src/compile.rs | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/compile.rs b/src/compile.rs
index 355b23a3a9..5e9cf715dc 100644
--- a/src/compile.rs
+++ b/src/compile.rs
@@ -1033,11 +1033,16 @@ impl ByteClassSet {
         // (0usize..256).map(|x| x as u8).collect()
         let mut byte_classes = vec![0; 256];
         let mut class = 0u8;
-        for i in 0..256 {
-            byte_classes[i] = class;
+        let mut i = 0;
+        loop {
+            byte_classes[i] = class as u8;
+            if i >= 255 {
+                break;
+            }
             if self.0[i] {
                 class = class.checked_add(1).unwrap();
             }
+            i += 1;
         }
         byte_classes
     }
@@ -1084,4 +1089,13 @@ mod tests {
         assert_eq!(classes[7], 3);
         assert_eq!(classes[255], 3);
     }
+
+    #[test]
+    fn full_byte_classes() {
+        let mut set = ByteClassSet::new();
+        for i in 0..256u16 {
+            set.set_range(i as u8, i as u8);
+        }
+        assert_eq!(set.byte_classes().len(), 256);
+    }
 }