Merge pull request #270 from BurntSushi/fixes

fix a few bugs

.travis.yml

@@ -7,8 +7,8 @@ rust:
 sudo: false
 script:
   - cargo build --verbose
-  - cargo build --verbose --manifest-path=regex-debug/Cargo.toml
   - if [ "$TRAVIS_RUST_VERSION" = "nightly" ]; then
+      cargo build --verbose --manifest-path=regex-debug/Cargo.toml;
       RUSTFLAGS="-C target-feature=+ssse3" cargo test --verbose --features 'simd-accel pattern';
     else
       travis_wait cargo test --verbose;

regex-syntax/src/lib.rs

@@ -528,6 +528,21 @@ impl Expr {
         }
     }
 
+    /// Returns true if and only if the expression has at least one matchable
+    /// sub-expression that must match the beginning of text.
+    pub fn has_anchored_start(&self) -> bool {
+        match *self {
+            Repeat { ref e, r, .. } => {
+                !r.matches_empty() && e.has_anchored_start()
+            }
+            Group { ref e, .. } => e.has_anchored_start(),
+            Concat(ref es) => es[0].has_anchored_start(),
+            Alternate(ref es) => es.iter().any(|e| e.has_anchored_start()),
+            StartText => true,
+            _ => false,
+        }
+    }
+
     /// Returns true if and only if the expression is required to match at the
     /// end of the text.
     pub fn is_anchored_end(&self) -> bool {
@@ -543,6 +558,21 @@ impl Expr {
         }
     }
 
+    /// Returns true if and only if the expression has at least one matchable
+    /// sub-expression that must match the beginning of text.
+    pub fn has_anchored_end(&self) -> bool {
+        match *self {
+            Repeat { ref e, r, .. } => {
+                !r.matches_empty() && e.has_anchored_end()
+            }
+            Group { ref e, .. } => e.has_anchored_end(),
+            Concat(ref es) => es[es.len() - 1].has_anchored_end(),
+            Alternate(ref es) => es.iter().any(|e| e.has_anchored_end()),
+            EndText => true,
+            _ => false,
+        }
+    }
+
     /// Returns true if and only if the expression contains sub-expressions
     /// that can match arbitrary bytes.
     pub fn has_bytes(&self) -> bool {

src/compile.rs

@@ -143,7 +143,9 @@ impl Compiler {
         // matching engine itself.
         let mut dotstar_patch = Patch { hole: Hole::None, entry: 0 };
         self.compiled.is_anchored_start = expr.is_anchored_start();
+        self.compiled.has_anchored_start = expr.has_anchored_start();
         self.compiled.is_anchored_end = expr.is_anchored_end();
+        self.compiled.has_anchored_end = expr.has_anchored_end();
         if self.compiled.needs_dotstar() {
             dotstar_patch = try!(self.c_dotstar());
             self.compiled.start = dotstar_patch.entry;
@@ -171,6 +173,10 @@ impl Compiler {
             exprs.iter().all(|e| e.is_anchored_start());
         self.compiled.is_anchored_end =
             exprs.iter().all(|e| e.is_anchored_end());
+        self.compiled.has_anchored_start =
+            exprs.iter().any(|e| e.has_anchored_start());
+        self.compiled.has_anchored_end =
+            exprs.iter().any(|e| e.has_anchored_end());
         let mut dotstar_patch = Patch { hole: Hole::None, entry: 0 };
         if self.compiled.needs_dotstar() {
             dotstar_patch = try!(self.c_dotstar());

src/dfa.rs

@@ -152,6 +152,9 @@ struct CacheInner {
     /// The total number of times this cache has been flushed by the DFA
     /// because of space constraints.
     flush_count: u64,
+    /// The total heap size of the DFA's cache. We use this to determine when
+    /// we should flush the cache.
+    size: usize,
 }
 
 /// The transition table.
@@ -420,18 +423,32 @@ impl Cache {
     pub fn new(prog: &Program) -> Self {
         // We add 1 to account for the special EOF byte.
         let num_byte_classes = (prog.byte_classes[255] as usize + 1) + 1;
-        Cache {
+        let starts = vec![STATE_UNKNOWN; 256];
+        let mut cache = Cache {
             inner: CacheInner {
                 compiled: HashMap::new(),
                 trans: Transitions::new(num_byte_classes),
                 states: vec![],
-                start_states: vec![STATE_UNKNOWN; 256],
+                start_states: starts,
                 stack: vec![],
                 flush_count: 0,
+                size: 0,
             },
             qcur: SparseSet::new(prog.insts.len()),
             qnext: SparseSet::new(prog.insts.len()),
-        }
+        };
+        cache.inner.reset_size();
+        cache
+    }
+}
+
+impl CacheInner {
+    /// Resets the cache size to account for fixed costs, such as the program
+    /// and stack sizes.
+    fn reset_size(&mut self) {
+        self.size =
+            (self.start_states.len() * mem::size_of::<StatePtr>())
+            + (self.stack.len() * mem::size_of::<InstPtr>());
     }
 }
 
@@ -1151,7 +1168,9 @@ impl<'a> Fsm<'a> {
         }
         // If the cache has gotten too big, wipe it.
         if self.approximate_size() > self.prog.dfa_size_limit {
+            println!("clearing cache (size: {:?})", self.approximate_size());
             if !self.clear_cache_and_save(current_state) {
+                println!("giving up");
                 // Ooops. DFA is giving up.
                 return None;
             }
@@ -1280,6 +1299,7 @@ impl<'a> Fsm<'a> {
         } else {
             None
         };
+        self.cache.reset_size();
         self.cache.trans.clear();
         self.cache.states.clear();
         self.cache.compiled.clear();
@@ -1454,6 +1474,11 @@ impl<'a> Fsm<'a> {
         }
         // Finally, put our actual state on to our heap of states and index it
         // so we can find it later.
+        self.cache.size +=
+            self.cache.trans.state_heap_size()
+            + (2 * state.data.len())
+            + (2 * mem::size_of::<State>())
+            + mem::size_of::<StatePtr>();
         self.cache.states.push(state.clone());
         self.cache.compiled.insert(state, si);
         // Transition table and set of states and map should all be in sync.
@@ -1536,51 +1561,8 @@ impl<'a> Fsm<'a> {
     /// be wiped. Namely, it is possible that for certain regexes on certain
     /// inputs, a new state could be created for every byte of input. (This is
     /// bad for memory use, so we bound it with a cache.)
-    ///
-    /// The approximation is guaranteed to be done in constant time (and
-    /// indeed, this requirement is why it's approximate).
     fn approximate_size(&self) -> usize {
-        use std::mem::size_of as size;
-        // Estimate that there are about 16 instructions per state consuming
-        // 20 = 4 + (15 * 1) bytes of space (1 byte because of delta encoding).
-        const STATE_HEAP: usize = 20 + 1; // one extra byte for flags
-        let compiled =
-            (self.cache.compiled.len() * (size::<State>() + STATE_HEAP))
-            + (self.cache.compiled.len() * size::<StatePtr>());
-        let states =
-            self.cache.states.len()
-            * (size::<State>()
-               + STATE_HEAP
-               + (self.num_byte_classes() * size::<StatePtr>()));
-        let start_states = self.cache.start_states.len() * size::<StatePtr>();
-        self.prog.approximate_size() + compiled + states + start_states
-    }
-
-    /// Returns the actual heap space of the DFA. This visits every state in
-    /// the DFA.
-    #[allow(dead_code)] // useful for debugging
-    fn actual_size(&self) -> usize {
-        let mut compiled = 0;
-        for k in self.cache.compiled.keys() {
-            compiled += mem::size_of::<State>();
-            compiled += mem::size_of::<StatePtr>();
-            compiled += k.data.len() * mem::size_of::<u8>();
-        }
-        let mut states = 0;
-        for s in &self.cache.states {
-            states += mem::size_of::<State>();
-            states += s.data.len() * mem::size_of::<u8>();
-        }
-        compiled
-        + states
-        + (self.cache.trans.num_states() *
-           mem::size_of::<StatePtr>() *
-           self.num_byte_classes())
-        + (self.cache.start_states.len() * mem::size_of::<StatePtr>())
-        + (self.cache.stack.len() * mem::size_of::<InstPtr>())
-        + mem::size_of::<Fsm>()
-        + mem::size_of::<CacheInner>()
-        + self.prog.approximate_size() // OK, not actual, but close enough
+        self.cache.size + self.prog.approximate_size()
     }
 }
 
@@ -1628,6 +1610,11 @@ impl Transitions {
         self.table[si as usize + cls]
     }
 
+    /// The heap size, in bytes, of a single state in the transition table.
+    fn state_heap_size(&self) -> usize {
+        self.num_byte_classes * mem::size_of::<StatePtr>()
+    }
+
     /// Like `next`, but uses unchecked access and is therefore unsafe.
     unsafe fn next_unchecked(&self, si: StatePtr, cls: usize) -> StatePtr {
         debug_assert!((si as usize) < self.table.len());

src/exec.rs

@@ -840,11 +840,7 @@ impl<'c> ExecNoSync<'c> {
     ) -> 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.
-        let e = if self.ro.nfa.uses_bytes() {
-            cmp::min(match_end + 1, text.len())
-        } else {
-            cmp::min(next_utf8(text, match_end), text.len())
-        };
+        let e = cmp::min(next_utf8(text, match_end), text.len());
         self.captures_nfa(slots, &text[..e], match_start)
     }
 
@@ -1113,7 +1109,15 @@ impl ExecReadOnly {
         // If our set of prefixes is complete, then we can use it to find
         // a match in lieu of a regex engine. This doesn't quite work well in
         // the presence of multiple regexes, so only do it when there's one.
-        if self.res.len() == 1 {
+        //
+        // TODO(burntsushi): Also, don't try to match literals if the regex is
+        // partially anchored. We could technically do it, but we'd need to
+        // create two sets of literals: all of them and then the subset that
+        // aren't anchored. We would then only search for all of them when at
+        // the beginning of the input and use the subset in all other cases.
+        if self.res.len() == 1
+            && !self.nfa.has_anchored_start
+            && !self.nfa.has_anchored_end {
             if self.nfa.prefixes.complete() {
                 return if self.nfa.is_anchored_start {
                     Literal(MatchLiteralType::AnchoredStart)

src/prog.rs

@@ -52,6 +52,12 @@ pub struct Program {
     pub is_anchored_start: bool,
     /// Whether the regex must match at the end of the input.
     pub is_anchored_end: bool,
+    /// Whether the regex has at least one matchable sub-expression that must
+    /// match from the start of the input.
+    pub has_anchored_start: bool,
+    /// Whether the regex has at least one matchable sub-expression that must
+    /// match at the end of the input.
+    pub has_anchored_end: bool,
     /// Whether this program contains a Unicode word boundary instruction.
     pub has_unicode_word_boundary: bool,
     /// A possibly empty machine for very quickly matching prefix literals.
@@ -91,6 +97,8 @@ impl Program {
             is_reverse: false,
             is_anchored_start: false,
             is_anchored_end: false,
+            has_anchored_start: false,
+            has_anchored_end: false,
             has_unicode_word_boundary: false,
             prefixes: LiteralSearcher::empty(),
             dfa_size_limit: 2 * (1<<20),

tests/regression.rs

@@ -57,3 +57,10 @@ split!(split_on_word_boundary, r"\b", r"Should this (work?)",
          t!(" ("), t!("work"), t!("?)")]);
 matiter!(word_boundary_dfa, r"\b", "a b c",
          (0, 0), (1, 1), (2, 2), (3, 3), (4, 4), (5, 5));
+
+// See: https://github.com/rust-lang-nursery/regex/issues/268
+matiter!(partial_anchor, u!(r"^a|b"), "ba", (0, 1));
+
+// See: https://github.com/rust-lang-nursery/regex/issues/264
+mat!(ascii_boundary_no_capture, u!(r"(?-u)\B"), "\u{28f3e}", Some((0, 0)));
+mat!(ascii_boundary_capture, u!(r"(?-u)(\B)"), "\u{28f3e}", Some((0, 0)));