Fix a bug in capture with match

When performing "EndText" matching, it is necessary to check whether
the current position matches the input text length.
However, when capturing a submatch using the matching result of DFA, "EndText" matching
wasn't actually performed correctly because the input text sliced.

By applying this patch we specify the match end position by the argument "end",
not using slice when performing capture with the matching result of DFA.

Fixes rust-lang#557

Author: hikotq

src/backtrack.rs

@@ -98,6 +98,7 @@ impl<'a, 'm, 'r, 's, I: Input> Bounded<'a, 'm, 'r, 's, I> {
         slots: &'s mut [Slot],
         input: I,
         start: usize,
+        end: usize, 
     ) -> bool {
         let mut cache = cache.borrow_mut();
         let cache = &mut cache.backtrack;
@@ -109,7 +110,7 @@ impl<'a, 'm, 'r, 's, I: Input> Bounded<'a, 'm, 'r, 's, I> {
             slots: slots,
             m: cache,
         };
-        b.exec_(start)
+        b.exec_(start, end)
     }
 
     /// Clears the cache such that the backtracking engine can be executed
@@ -147,7 +148,7 @@ impl<'a, 'm, 'r, 's, I: Input> Bounded<'a, 'm, 'r, 's, I> {
 
     /// Start backtracking at the given position in the input, but also look
     /// for literal prefixes.
-    fn exec_(&mut self, mut at: InputAt) -> bool {
+    fn exec_(&mut self, mut at: InputAt, end: usize) -> bool {
         self.clear();
         // If this is an anchored regex at the beginning of the input, then
         // we're either already done or we only need to try backtracking once.
@@ -170,7 +171,7 @@ impl<'a, 'm, 'r, 's, I: Input> Bounded<'a, 'm, 'r, 's, I> {
             if matched && self.prog.matches.len() == 1 {
                 return true;
             }
-            if at.is_end() {
+            if at.pos() == end {
                 break;
             }
             at = self.input.at(at.next_pos());

src/exec.rs

@@ -10,7 +10,6 @@
 
 use std::cell::RefCell;
 use std::collections::HashMap;
-use std::cmp;
 use std::sync::Arc;
 
 use thread_local::CachedThreadLocal;
@@ -557,7 +556,7 @@ impl<'c> RegularExpression for ExecNoSync<'c> {
         match self.ro.match_type {
             MatchType::Literal(ty) => {
                 self.find_literals(ty, text, start).and_then(|(s, e)| {
-                    self.captures_nfa_with_match(slots, text, s, e)
+                    self.captures_nfa_type(MatchNfaType::Auto, slots, text, s, e)
                 })
             }
             MatchType::Dfa => {
@@ -566,7 +565,7 @@ impl<'c> RegularExpression for ExecNoSync<'c> {
                 } else {
                     match self.find_dfa_forward(text, start) {
                         dfa::Result::Match((s, e)) => {
-                            self.captures_nfa_with_match(slots, text, s, e)
+                            self.captures_nfa_type(MatchNfaType::Auto, slots, text, s, e)
                         }
                         dfa::Result::NoMatch(_) => None,
                         dfa::Result::Quit => self.captures_nfa(slots, text, start),
@@ -576,7 +575,7 @@ impl<'c> RegularExpression for ExecNoSync<'c> {
             MatchType::DfaAnchoredReverse => {
                 match self.find_dfa_anchored_reverse(text, start) {
                     dfa::Result::Match((s, e)) => {
-                        self.captures_nfa_with_match(slots, text, s, e)
+                        self.captures_nfa_type(MatchNfaType::Auto, slots, text, s, e)
                     }
                     dfa::Result::NoMatch(_) => None,
                     dfa::Result::Quit => self.captures_nfa(slots, text, start),
@@ -585,14 +584,14 @@ impl<'c> RegularExpression for ExecNoSync<'c> {
             MatchType::DfaSuffix => {
                 match self.find_dfa_reverse_suffix(text, start) {
                     dfa::Result::Match((s, e)) => {
-                        self.captures_nfa_with_match(slots, text, s, e)
+                        self.captures_nfa_type(MatchNfaType::Auto, slots, text, s, e)
                     }
                     dfa::Result::NoMatch(_) => None,
                     dfa::Result::Quit => self.captures_nfa(slots, text, start),
                 }
             }
             MatchType::Nfa(ty) => {
-                self.captures_nfa_type(ty, slots, text, start)
+                self.captures_nfa_type(ty, slots, text, start, text.len())
             }
             MatchType::Nothing => None,
             MatchType::DfaMany => {
@@ -830,7 +829,7 @@ impl<'c> ExecNoSync<'c> {
         text: &[u8],
         start: usize,
     ) -> bool {
-        self.exec_nfa(ty, &mut [false], &mut [], true, text, start)
+        self.exec_nfa(ty, &mut [false], &mut [], true, text, start, text.len())
     }
 
     /// Finds the shortest match using an NFA.
@@ -846,7 +845,7 @@ impl<'c> ExecNoSync<'c> {
         start: usize,
     ) -> Option<usize> {
         let mut slots = [None, None];
-        if self.exec_nfa(ty, &mut [false], &mut slots, true, text, start) {
+        if self.exec_nfa(ty, &mut [false], &mut slots, true, text, start, text.len()) {
             slots[1]
         } else {
             None
@@ -861,7 +860,7 @@ impl<'c> ExecNoSync<'c> {
         start: usize,
     ) -> Option<(usize, usize)> {
         let mut slots = [None, None];
-        if self.exec_nfa(ty, &mut [false], &mut slots, false, text, start) {
+        if self.exec_nfa(ty, &mut [false], &mut slots, false, text, start, text.len()) {
             match (slots[0], slots[1]) {
                 (Some(s), Some(e)) => Some((s, e)),
                 _ => None,
@@ -871,26 +870,6 @@ impl<'c> ExecNoSync<'c> {
         }
     }
 
-    /// Like find_nfa, but fills in captures and restricts the search space
-    /// using previously found match information.
-    ///
-    /// `slots` should have length equal to `2 * nfa.captures.len()`.
-    fn captures_nfa_with_match(
-        &self,
-        slots: &mut [Slot],
-        text: &[u8],
-        match_start: usize,
-        match_end: usize,
-    ) -> Option<(usize, usize)> {
-        // We can't use match_end directly, because we may need to examine one
-        // "character" after the end of a match for lookahead operators. We
-        // need to move two characters beyond the end, since some look-around
-        // operations may falsely assume a premature end of text otherwise.
-        let e = cmp::min(
-            next_utf8(text, next_utf8(text, match_end)), text.len());
-        self.captures_nfa(slots, &text[..e], match_start)
-    }
-
     /// Like find_nfa, but fills in captures.
     ///
     /// `slots` should have length equal to `2 * nfa.captures.len()`.
@@ -900,7 +879,7 @@ impl<'c> ExecNoSync<'c> {
         text: &[u8],
         start: usize,
     ) -> Option<(usize, usize)> {
-        self.captures_nfa_type(MatchNfaType::Auto, slots, text, start)
+        self.captures_nfa_type(MatchNfaType::Auto, slots, text, start, text.len())
     }
 
     /// Like captures_nfa, but allows specification of type of NFA engine.
@@ -910,8 +889,9 @@ impl<'c> ExecNoSync<'c> {
         slots: &mut [Slot],
         text: &[u8],
         start: usize,
+        end: usize, 
     ) -> Option<(usize, usize)> {
-        if self.exec_nfa(ty, &mut [false], slots, false, text, start) {
+        if self.exec_nfa(ty, &mut [false], slots, false, text, start, end) {
             match (slots[0], slots[1]) {
                 (Some(s), Some(e)) => Some((s, e)),
                 _ => None,
@@ -929,6 +909,7 @@ impl<'c> ExecNoSync<'c> {
         quit_after_match: bool,
         text: &[u8],
         start: usize,
+        end: usize, 
     ) -> bool {
         use self::MatchNfaType::*;
         if let Auto = ty {
@@ -940,10 +921,10 @@ impl<'c> ExecNoSync<'c> {
         }
         match ty {
             Auto => unreachable!(),
-            Backtrack => self.exec_backtrack(matches, slots, text, start),
+            Backtrack => self.exec_backtrack(matches, slots, text, start, end),
             PikeVM => {
                 self.exec_pikevm(
-                    matches, slots, quit_after_match, text, start)
+                    matches, slots, quit_after_match, text, start, end)
             }
         }
     }
@@ -956,6 +937,7 @@ impl<'c> ExecNoSync<'c> {
         quit_after_match: bool,
         text: &[u8],
         start: usize,
+        end: usize, 
     ) -> bool {
         if self.ro.nfa.uses_bytes() {
             pikevm::Fsm::exec(
@@ -965,7 +947,8 @@ impl<'c> ExecNoSync<'c> {
                 slots,
                 quit_after_match,
                 ByteInput::new(text, self.ro.nfa.only_utf8),
-                start)
+                start,
+                end)
         } else {
             pikevm::Fsm::exec(
                 &self.ro.nfa,
@@ -974,7 +957,8 @@ impl<'c> ExecNoSync<'c> {
                 slots,
                 quit_after_match,
                 CharInput::new(text),
-                start)
+                start,
+                end)
         }
     }
 
@@ -985,6 +969,7 @@ impl<'c> ExecNoSync<'c> {
         slots: &mut [Slot],
         text: &[u8],
         start: usize,
+        end: usize,
     ) -> bool {
         if self.ro.nfa.uses_bytes() {
             backtrack::Bounded::exec(
@@ -993,15 +978,17 @@ impl<'c> ExecNoSync<'c> {
                 matches,
                 slots,
                 ByteInput::new(text, self.ro.nfa.only_utf8),
-                start)
+                start,
+                end)
         } else {
             backtrack::Bounded::exec(
                 &self.ro.nfa,
                 self.cache,
                 matches,
                 slots,
                 CharInput::new(text),
-                start)
+                start,
+                end)
         }
     }
 
@@ -1045,11 +1032,12 @@ impl<'c> ExecNoSync<'c> {
                             &mut [],
                             false,
                             text,
-                            start)
+                            start,
+                            text.len())
                     }
                 }
             }
-            Nfa(ty) => self.exec_nfa(ty, matches, &mut [], false, text, start),
+            Nfa(ty) => self.exec_nfa(ty, matches, &mut [], false, text, start, text.len()),
             Nothing => false,
         }
     }

src/pikevm.rs

@@ -107,6 +107,7 @@ impl<'r, I: Input> Fsm<'r, I> {
         quit_after_match: bool,
         input: I,
         start: usize,
+        end: usize, 
     ) -> bool {
         let mut cache = cache.borrow_mut();
         let cache = &mut cache.pikevm;
@@ -124,6 +125,7 @@ impl<'r, I: Input> Fsm<'r, I> {
             slots,
             quit_after_match,
             at,
+            end, 
         )
     }
 
@@ -135,6 +137,7 @@ impl<'r, I: Input> Fsm<'r, I> {
         slots: &mut [Slot],
         quit_after_match: bool,
         mut at: InputAt,
+        end: usize, 
     ) -> bool {
         let mut matched = false;
         let mut all_matched = false;
@@ -212,7 +215,7 @@ impl<'r, I: Input> Fsm<'r, I> {
                     }
                 }
             }
-            if at.is_end() {
+            if at.pos() == end {
                 break;
             }
             at = at_next;

tests/regression.rs

@@ -88,8 +88,13 @@ ismatch!(reverse_suffix2, r"\d\d\d000", "153.230000\n", true);
 matiter!(reverse_suffix3, r"\d\d\d000", "153.230000\n", (4, 10));
 
 // See: https://github.com/rust-lang/regex/issues/334
-mat!(captures_after_dfa_premature_end, r"a(b*(X|$))?", "abcbX",
+// See: https://github.com/rust-lang/regex/issues/557
+mat!(captures_after_dfa_premature_end1, r"a(b*(X|$))?", "abcbX",
      Some((0, 1)), None, None);
+mat!(captures_after_dfa_premature_end2, r"a(bc*(X|$))?", "abcbX",
+     Some((0, 1)), None, None);
+mat!(captures_after_dfa_premature_end3, r"(aa$)?", "aaz",
+     Some((0, 0)));
 
 // See: https://github.com/rust-lang/regex/issues/437
 ismatch!(