From 9728dd8699a255686deaedbdd0f23f549e62009f Mon Sep 17 00:00:00 2001
From: Kangzhi Shi <shikangzhi@gmail.com>
Date: Fri, 16 Apr 2021 09:35:11 +0200
Subject: [PATCH] fix test_string_boundaries

---
 src/engine.rs  | 14 +++++++++++---
 tests/tests.rs | 11 +++++++++++
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/src/engine.rs b/src/engine.rs
index 5e0e0f420..0de9f4384 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -292,6 +292,14 @@ trait MatchContextDrive {
         let this = !self.at_end() && word_checker(self.peek_char());
         this != that
     }
+    fn at_non_boundary<F: FnMut(u32) -> bool>(&self, mut word_checker: F) -> bool {
+        if self.at_beginning() && self.at_end() {
+            return false;
+        }
+        let that = !self.at_beginning() && word_checker(self.back_peek_char());
+        let this = !self.at_end() && word_checker(self.peek_char());
+        this == that
+    }
     fn back_peek_char(&self) -> u32 {
         self.state().string.back_peek(self.ctx().string_offset)
     }
@@ -738,14 +746,14 @@ fn at(drive: &StackDrive, atcode: SreAtCode) -> bool {
         SreAtCode::BEGINNING | SreAtCode::BEGINNING_STRING => drive.at_beginning(),
         SreAtCode::BEGINNING_LINE => drive.at_beginning() || is_linebreak(drive.back_peek_char()),
         SreAtCode::BOUNDARY => drive.at_boundary(is_word),
-        SreAtCode::NON_BOUNDARY => !drive.at_boundary(is_word),
+        SreAtCode::NON_BOUNDARY => drive.at_non_boundary(is_word),
         SreAtCode::END => (drive.remaining_chars() == 1 && drive.at_linebreak()) || drive.at_end(),
         SreAtCode::END_LINE => drive.at_linebreak() || drive.at_end(),
         SreAtCode::END_STRING => drive.at_end(),
         SreAtCode::LOC_BOUNDARY => drive.at_boundary(is_loc_word),
-        SreAtCode::LOC_NON_BOUNDARY => !drive.at_boundary(is_loc_word),
+        SreAtCode::LOC_NON_BOUNDARY => drive.at_non_boundary(is_loc_word),
         SreAtCode::UNI_BOUNDARY => drive.at_boundary(is_uni_word),
-        SreAtCode::UNI_NON_BOUNDARY => !drive.at_boundary(is_uni_word),
+        SreAtCode::UNI_NON_BOUNDARY => drive.at_non_boundary(is_uni_word),
     }
 }
 
diff --git a/tests/tests.rs b/tests/tests.rs
index f4cd091f0..690c72861 100644
--- a/tests/tests.rs
+++ b/tests/tests.rs
@@ -37,3 +37,14 @@ fn test_assert() {
     state = state.search();
     assert!(state.has_matched == Some(true));
 }
+
+#[test]
+fn test_string_boundaries() {
+    // pattern big_b = re.compile(r'\B')
+    // START GENERATED by generate_tests.py
+    #[rustfmt::skip] let big_b = Pattern { code: &[15, 4, 0, 0, 0, 6, 11, 1], flags: SreFlag::from_bits_truncate(32) };
+    // END GENERATED
+    let mut state = big_b.state("", 0..usize::MAX);
+    state = state.search();
+    assert!(state.has_matched == None)
+}