Imported WebKit commit 2ea9d364d0f6efa8fa64acf19f451504c59be0e4 (http://svn.webkit.org/repository/webkit/trunk@104285)

1 files changed, 821 insertions, 0 deletions

diff --git a/Source/JavaScriptCore/yarr/YarrPattern.cpp b/Source/JavaScriptCore/yarr/YarrPattern.cpp
new file mode 100644
index 000000000..1043e405d
--- /dev/null
+++ b/Source/JavaScriptCore/yarr/YarrPattern.cpp
@@ -0,0 +1,821 @@
+/*
+ * Copyright (C) 2009 Apple Inc. All rights reserved.
+ * Copyright (C) 2010 Peter Varga (pvarga@inf.u-szeged.hu), University of Szeged
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
+ */
+
+#include "config.h"
+#include "YarrPattern.h"
+
+#include "Yarr.h"
+#include "YarrParser.h"
+#include <wtf/Vector.h>
+
+using namespace WTF;
+
+namespace JSC { namespace Yarr {
+
+#include "RegExpJitTables.h"
+
+class CharacterClassConstructor {
+public:
+    CharacterClassConstructor(bool isCaseInsensitive = false)
+        : m_isCaseInsensitive(isCaseInsensitive)
+    {
+    }
+    
+    void reset()
+    {
+        m_matches.clear();
+        m_ranges.clear();
+        m_matchesUnicode.clear();
+        m_rangesUnicode.clear();
+    }
+
+    void append(const CharacterClass* other)
+    {
+        for (size_t i = 0; i < other->m_matches.size(); ++i)
+            addSorted(m_matches, other->m_matches[i]);
+        for (size_t i = 0; i < other->m_ranges.size(); ++i)
+            addSortedRange(m_ranges, other->m_ranges[i].begin, other->m_ranges[i].end);
+        for (size_t i = 0; i < other->m_matchesUnicode.size(); ++i)
+            addSorted(m_matchesUnicode, other->m_matchesUnicode[i]);
+        for (size_t i = 0; i < other->m_rangesUnicode.size(); ++i)
+            addSortedRange(m_rangesUnicode, other->m_rangesUnicode[i].begin, other->m_rangesUnicode[i].end);
+    }
+
+    void putChar(UChar ch)
+    {
+        if (ch <= 0x7f) {
+            if (m_isCaseInsensitive && isASCIIAlpha(ch)) {
+                addSorted(m_matches, toASCIIUpper(ch));
+                addSorted(m_matches, toASCIILower(ch));
+            } else
+                addSorted(m_matches, ch);
+        } else {
+            UChar upper, lower;
+            if (m_isCaseInsensitive && ((upper = Unicode::toUpper(ch)) != (lower = Unicode::toLower(ch)))) {
+                addSorted(m_matchesUnicode, upper);
+                addSorted(m_matchesUnicode, lower);
+            } else
+                addSorted(m_matchesUnicode, ch);
+        }
+    }
+
+    // returns true if this character has another case, and 'ch' is the upper case form.
+    static inline bool isUnicodeUpper(UChar ch)
+    {
+        return ch != Unicode::toLower(ch);
+    }
+
+    // returns true if this character has another case, and 'ch' is the lower case form.
+    static inline bool isUnicodeLower(UChar ch)
+    {
+        return ch != Unicode::toUpper(ch);
+    }
+
+    void putRange(UChar lo, UChar hi)
+    {
+        if (lo <= 0x7f) {
+            char asciiLo = lo;
+            char asciiHi = std::min(hi, (UChar)0x7f);
+            addSortedRange(m_ranges, lo, asciiHi);
+            
+            if (m_isCaseInsensitive) {
+                if ((asciiLo <= 'Z') && (asciiHi >= 'A'))
+                    addSortedRange(m_ranges, std::max(asciiLo, 'A')+('a'-'A'), std::min(asciiHi, 'Z')+('a'-'A'));
+                if ((asciiLo <= 'z') && (asciiHi >= 'a'))
+                    addSortedRange(m_ranges, std::max(asciiLo, 'a')+('A'-'a'), std::min(asciiHi, 'z')+('A'-'a'));
+            }
+        }
+        if (hi >= 0x80) {
+            uint32_t unicodeCurr = std::max(lo, (UChar)0x80);
+            addSortedRange(m_rangesUnicode, unicodeCurr, hi);
+            
+            if (m_isCaseInsensitive) {
+                while (unicodeCurr <= hi) {
+                    // If the upper bound of the range (hi) is 0xffff, the increments to
+                    // unicodeCurr in this loop may take it to 0x10000.  This is fine
+                    // (if so we won't re-enter the loop, since the loop condition above
+                    // will definitely fail) - but this does mean we cannot use a UChar
+                    // to represent unicodeCurr, we must use a 32-bit value instead.
+                    ASSERT(unicodeCurr <= 0xffff);
+
+                    if (isUnicodeUpper(unicodeCurr)) {
+                        UChar lowerCaseRangeBegin = Unicode::toLower(unicodeCurr);
+                        UChar lowerCaseRangeEnd = lowerCaseRangeBegin;
+                        while ((++unicodeCurr <= hi) && isUnicodeUpper(unicodeCurr) && (Unicode::toLower(unicodeCurr) == (lowerCaseRangeEnd + 1)))
+                            lowerCaseRangeEnd++;
+                        addSortedRange(m_rangesUnicode, lowerCaseRangeBegin, lowerCaseRangeEnd);
+                    } else if (isUnicodeLower(unicodeCurr)) {
+                        UChar upperCaseRangeBegin = Unicode::toUpper(unicodeCurr);
+                        UChar upperCaseRangeEnd = upperCaseRangeBegin;
+                        while ((++unicodeCurr <= hi) && isUnicodeLower(unicodeCurr) && (Unicode::toUpper(unicodeCurr) == (upperCaseRangeEnd + 1)))
+                            upperCaseRangeEnd++;
+                        addSortedRange(m_rangesUnicode, upperCaseRangeBegin, upperCaseRangeEnd);
+                    } else
+                        ++unicodeCurr;
+                }
+            }
+        }
+    }
+
+    CharacterClass* charClass()
+    {
+        CharacterClass* characterClass = new CharacterClass(0);
+
+        characterClass->m_matches.swap(m_matches);
+        characterClass->m_ranges.swap(m_ranges);
+        characterClass->m_matchesUnicode.swap(m_matchesUnicode);
+        characterClass->m_rangesUnicode.swap(m_rangesUnicode);
+
+        return characterClass;
+    }
+
+private:
+    void addSorted(Vector<UChar>& matches, UChar ch)
+    {
+        unsigned pos = 0;
+        unsigned range = matches.size();
+
+        // binary chop, find position to insert char.
+        while (range) {
+            unsigned index = range >> 1;
+
+            int val = matches[pos+index] - ch;
+            if (!val)
+                return;
+            else if (val > 0)
+                range = index;
+            else {
+                pos += (index+1);
+                range -= (index+1);
+            }
+        }
+        
+        if (pos == matches.size())
+            matches.append(ch);
+        else
+            matches.insert(pos, ch);
+    }
+
+    void addSortedRange(Vector<CharacterRange>& ranges, UChar lo, UChar hi)
+    {
+        unsigned end = ranges.size();
+        
+        // Simple linear scan - I doubt there are that many ranges anyway...
+        // feel free to fix this with something faster (eg binary chop).
+        for (unsigned i = 0; i < end; ++i) {
+            // does the new range fall before the current position in the array
+            if (hi < ranges[i].begin) {
+                // optional optimization: concatenate appending ranges? - may not be worthwhile.
+                if (hi == (ranges[i].begin - 1)) {
+                    ranges[i].begin = lo;
+                    return;
+                }
+                ranges.insert(i, CharacterRange(lo, hi));
+                return;
+            }
+            // Okay, since we didn't hit the last case, the end of the new range is definitely at or after the begining
+            // If the new range start at or before the end of the last range, then the overlap (if it starts one after the
+            // end of the last range they concatenate, which is just as good.
+            if (lo <= (ranges[i].end + 1)) {
+                // found an intersect! we'll replace this entry in the array.
+                ranges[i].begin = std::min(ranges[i].begin, lo);
+                ranges[i].end = std::max(ranges[i].end, hi);
+
+                // now check if the new range can subsume any subsequent ranges.
+                unsigned next = i+1;
+                // each iteration of the loop we will either remove something from the list, or break the loop.
+                while (next < ranges.size()) {
+                    if (ranges[next].begin <= (ranges[i].end + 1)) {
+                        // the next entry now overlaps / concatenates this one.
+                        ranges[i].end = std::max(ranges[i].end, ranges[next].end);
+                        ranges.remove(next);
+                    } else
+                        break;
+                }
+                
+                return;
+            }
+        }
+
+        // CharacterRange comes after all existing ranges.
+        ranges.append(CharacterRange(lo, hi));
+    }
+
+    bool m_isCaseInsensitive;
+
+    Vector<UChar> m_matches;
+    Vector<CharacterRange> m_ranges;
+    Vector<UChar> m_matchesUnicode;
+    Vector<CharacterRange> m_rangesUnicode;
+};
+
+class YarrPatternConstructor {
+public:
+    YarrPatternConstructor(YarrPattern& pattern)
+        : m_pattern(pattern)
+        , m_characterClassConstructor(pattern.m_ignoreCase)
+        , m_invertParentheticalAssertion(false)
+    {
+        m_pattern.m_body = new PatternDisjunction();
+        m_alternative = m_pattern.m_body->addNewAlternative();
+        m_pattern.m_disjunctions.append(m_pattern.m_body);
+    }
+
+    ~YarrPatternConstructor()
+    {
+    }
+
+    void reset()
+    {
+        m_pattern.reset();
+        m_characterClassConstructor.reset();
+
+        m_pattern.m_body = new PatternDisjunction();
+        m_alternative = m_pattern.m_body->addNewAlternative();
+        m_pattern.m_disjunctions.append(m_pattern.m_body);
+    }
+    
+    void assertionBOL()
+    {
+        if (!m_alternative->m_terms.size() & !m_invertParentheticalAssertion) {
+            m_alternative->m_startsWithBOL = true;
+            m_alternative->m_containsBOL = true;
+            m_pattern.m_containsBOL = true;
+        }
+        m_alternative->m_terms.append(PatternTerm::BOL());
+    }
+    void assertionEOL()
+    {
+        m_alternative->m_terms.append(PatternTerm::EOL());
+    }
+    void assertionWordBoundary(bool invert)
+    {
+        m_alternative->m_terms.append(PatternTerm::WordBoundary(invert));
+    }
+
+    void atomPatternCharacter(UChar ch)
+    {
+        // We handle case-insensitive checking of unicode characters which do have both
+        // cases by handling them as if they were defined using a CharacterClass.
+        if (m_pattern.m_ignoreCase && !isASCII(ch) && (Unicode::toUpper(ch) != Unicode::toLower(ch))) {
+            atomCharacterClassBegin();
+            atomCharacterClassAtom(ch);
+            atomCharacterClassEnd();
+        } else
+            m_alternative->m_terms.append(PatternTerm(ch));
+    }
+
+    void atomBuiltInCharacterClass(BuiltInCharacterClassID classID, bool invert)
+    {
+        switch (classID) {
+        case DigitClassID:
+            m_alternative->m_terms.append(PatternTerm(m_pattern.digitsCharacterClass(), invert));
+            break;
+        case SpaceClassID:
+            m_alternative->m_terms.append(PatternTerm(m_pattern.spacesCharacterClass(), invert));
+            break;
+        case WordClassID:
+            m_alternative->m_terms.append(PatternTerm(m_pattern.wordcharCharacterClass(), invert));
+            break;
+        case NewlineClassID:
+            m_alternative->m_terms.append(PatternTerm(m_pattern.newlineCharacterClass(), invert));
+            break;
+        }
+    }
+
+    void atomCharacterClassBegin(bool invert = false)
+    {
+        m_invertCharacterClass = invert;
+    }
+
+    void atomCharacterClassAtom(UChar ch)
+    {
+        m_characterClassConstructor.putChar(ch);
+    }
+
+    void atomCharacterClassRange(UChar begin, UChar end)
+    {
+        m_characterClassConstructor.putRange(begin, end);
+    }
+
+    void atomCharacterClassBuiltIn(BuiltInCharacterClassID classID, bool invert)
+    {
+        ASSERT(classID != NewlineClassID);
+
+        switch (classID) {
+        case DigitClassID:
+            m_characterClassConstructor.append(invert ? m_pattern.nondigitsCharacterClass() : m_pattern.digitsCharacterClass());
+            break;
+        
+        case SpaceClassID:
+            m_characterClassConstructor.append(invert ? m_pattern.nonspacesCharacterClass() : m_pattern.spacesCharacterClass());
+            break;
+        
+        case WordClassID:
+            m_characterClassConstructor.append(invert ? m_pattern.nonwordcharCharacterClass() : m_pattern.wordcharCharacterClass());
+            break;
+        
+        default:
+            ASSERT_NOT_REACHED();
+        }
+    }
+
+    void atomCharacterClassEnd()
+    {
+        CharacterClass* newCharacterClass = m_characterClassConstructor.charClass();
+        m_pattern.m_userCharacterClasses.append(newCharacterClass);
+        m_alternative->m_terms.append(PatternTerm(newCharacterClass, m_invertCharacterClass));
+    }
+
+    void atomParenthesesSubpatternBegin(bool capture = true)
+    {
+        unsigned subpatternId = m_pattern.m_numSubpatterns + 1;
+        if (capture)
+            m_pattern.m_numSubpatterns++;
+
+        PatternDisjunction* parenthesesDisjunction = new PatternDisjunction(m_alternative);
+        m_pattern.m_disjunctions.append(parenthesesDisjunction);
+        m_alternative->m_terms.append(PatternTerm(PatternTerm::TypeParenthesesSubpattern, subpatternId, parenthesesDisjunction, capture, false));
+        m_alternative = parenthesesDisjunction->addNewAlternative();
+    }
+
+    void atomParentheticalAssertionBegin(bool invert = false)
+    {
+        PatternDisjunction* parenthesesDisjunction = new PatternDisjunction(m_alternative);
+        m_pattern.m_disjunctions.append(parenthesesDisjunction);
+        m_alternative->m_terms.append(PatternTerm(PatternTerm::TypeParentheticalAssertion, m_pattern.m_numSubpatterns + 1, parenthesesDisjunction, false, invert));
+        m_alternative = parenthesesDisjunction->addNewAlternative();
+        m_invertParentheticalAssertion = invert;
+    }
+
+    void atomParenthesesEnd()
+    {
+        ASSERT(m_alternative->m_parent);
+        ASSERT(m_alternative->m_parent->m_parent);
+
+        PatternDisjunction* parenthesesDisjunction = m_alternative->m_parent;
+        m_alternative = m_alternative->m_parent->m_parent;
+
+        PatternTerm& lastTerm = m_alternative->lastTerm();
+
+        unsigned numParenAlternatives = parenthesesDisjunction->m_alternatives.size();
+        unsigned numBOLAnchoredAlts = 0;
+
+        for (unsigned i = 0; i < numParenAlternatives; i++) {
+            // Bubble up BOL flags
+            if (parenthesesDisjunction->m_alternatives[i]->m_startsWithBOL)
+                numBOLAnchoredAlts++;
+        }
+
+        if (numBOLAnchoredAlts) {
+            m_alternative->m_containsBOL = true;
+            // If all the alternatives in parens start with BOL, then so does this one
+            if (numBOLAnchoredAlts == numParenAlternatives)
+                m_alternative->m_startsWithBOL = true;
+        }
+
+        lastTerm.parentheses.lastSubpatternId = m_pattern.m_numSubpatterns;
+        m_invertParentheticalAssertion = false;
+    }
+
+    void atomBackReference(unsigned subpatternId)
+    {
+        ASSERT(subpatternId);
+        m_pattern.m_containsBackreferences = true;
+        m_pattern.m_maxBackReference = std::max(m_pattern.m_maxBackReference, subpatternId);
+
+        if (subpatternId > m_pattern.m_numSubpatterns) {
+            m_alternative->m_terms.append(PatternTerm::ForwardReference());
+            return;
+        }
+
+        PatternAlternative* currentAlternative = m_alternative;
+        ASSERT(currentAlternative);
+
+        // Note to self: if we waited until the AST was baked, we could also remove forwards refs 
+        while ((currentAlternative = currentAlternative->m_parent->m_parent)) {
+            PatternTerm& term = currentAlternative->lastTerm();
+            ASSERT((term.type == PatternTerm::TypeParenthesesSubpattern) || (term.type == PatternTerm::TypeParentheticalAssertion));
+
+            if ((term.type == PatternTerm::TypeParenthesesSubpattern) && term.capture() && (subpatternId == term.parentheses.subpatternId)) {
+                m_alternative->m_terms.append(PatternTerm::ForwardReference());
+                return;
+            }
+        }
+
+        m_alternative->m_terms.append(PatternTerm(subpatternId));
+    }
+
+    // deep copy the argument disjunction.  If filterStartsWithBOL is true, 
+    // skip alternatives with m_startsWithBOL set true.
+    PatternDisjunction* copyDisjunction(PatternDisjunction* disjunction, bool filterStartsWithBOL = false)
+    {
+        PatternDisjunction* newDisjunction = 0;
+        for (unsigned alt = 0; alt < disjunction->m_alternatives.size(); ++alt) {
+            PatternAlternative* alternative = disjunction->m_alternatives[alt];
+            if (!filterStartsWithBOL || !alternative->m_startsWithBOL) {
+                if (!newDisjunction) {
+                    newDisjunction = new PatternDisjunction();
+                    newDisjunction->m_parent = disjunction->m_parent;
+                }
+                PatternAlternative* newAlternative = newDisjunction->addNewAlternative();
+                for (unsigned i = 0; i < alternative->m_terms.size(); ++i)
+                    newAlternative->m_terms.append(copyTerm(alternative->m_terms[i], filterStartsWithBOL));
+            }
+        }
+        
+        if (newDisjunction)
+            m_pattern.m_disjunctions.append(newDisjunction);
+        return newDisjunction;
+    }
+    
+    PatternTerm copyTerm(PatternTerm& term, bool filterStartsWithBOL = false)
+    {
+        if ((term.type != PatternTerm::TypeParenthesesSubpattern) && (term.type != PatternTerm::TypeParentheticalAssertion))
+            return PatternTerm(term);
+        
+        PatternTerm termCopy = term;
+        termCopy.parentheses.disjunction = copyDisjunction(termCopy.parentheses.disjunction, filterStartsWithBOL);
+        return termCopy;
+    }
+    
+    void quantifyAtom(unsigned min, unsigned max, bool greedy)
+    {
+        ASSERT(min <= max);
+        ASSERT(m_alternative->m_terms.size());
+
+        if (!max) {
+            m_alternative->removeLastTerm();
+            return;
+        }
+
+        PatternTerm& term = m_alternative->lastTerm();
+        ASSERT(term.type > PatternTerm::TypeAssertionWordBoundary);
+        ASSERT((term.quantityCount == 1) && (term.quantityType == QuantifierFixedCount));
+
+        // For any assertion with a zero minimum, not matching is valid and has no effect,
+        // remove it.  Otherwise, we need to match as least once, but there is no point
+        // matching more than once, so remove the quantifier.  It is not entirely clear
+        // from the spec whether or not this behavior is correct, but I believe this
+        // matches Firefox. :-/
+        if (term.type == PatternTerm::TypeParentheticalAssertion) {
+            if (!min)
+                m_alternative->removeLastTerm();
+            return;
+        }
+
+        if (min == 0)
+            term.quantify(max, greedy   ? QuantifierGreedy : QuantifierNonGreedy);
+        else if (min == max)
+            term.quantify(min, QuantifierFixedCount);
+        else {
+            term.quantify(min, QuantifierFixedCount);
+            m_alternative->m_terms.append(copyTerm(term));
+            // NOTE: this term is interesting from an analysis perspective, in that it can be ignored.....
+            m_alternative->lastTerm().quantify((max == quantifyInfinite) ? max : max - min, greedy ? QuantifierGreedy : QuantifierNonGreedy);
+            if (m_alternative->lastTerm().type == PatternTerm::TypeParenthesesSubpattern)
+                m_alternative->lastTerm().parentheses.isCopy = true;
+        }
+    }
+
+    void disjunction()
+    {
+        m_alternative = m_alternative->m_parent->addNewAlternative();
+    }
+
+    unsigned setupAlternativeOffsets(PatternAlternative* alternative, unsigned currentCallFrameSize, unsigned initialInputPosition)
+    {
+        alternative->m_hasFixedSize = true;
+        Checked<unsigned> currentInputPosition = initialInputPosition;
+
+        for (unsigned i = 0; i < alternative->m_terms.size(); ++i) {
+            PatternTerm& term = alternative->m_terms[i];
+
+            switch (term.type) {
+            case PatternTerm::TypeAssertionBOL:
+            case PatternTerm::TypeAssertionEOL:
+            case PatternTerm::TypeAssertionWordBoundary:
+                term.inputPosition = currentInputPosition.unsafeGet();
+                break;
+
+            case PatternTerm::TypeBackReference:
+                term.inputPosition = currentInputPosition.unsafeGet();
+                term.frameLocation = currentCallFrameSize;
+                currentCallFrameSize += YarrStackSpaceForBackTrackInfoBackReference;
+                alternative->m_hasFixedSize = false;
+                break;
+
+            case PatternTerm::TypeForwardReference:
+                break;
+
+            case PatternTerm::TypePatternCharacter:
+                term.inputPosition = currentInputPosition.unsafeGet();
+                if (term.quantityType != QuantifierFixedCount) {
+                    term.frameLocation = currentCallFrameSize;
+                    currentCallFrameSize += YarrStackSpaceForBackTrackInfoPatternCharacter;
+                    alternative->m_hasFixedSize = false;
+                } else
+                    currentInputPosition += term.quantityCount;
+                break;
+
+            case PatternTerm::TypeCharacterClass:
+                term.inputPosition = currentInputPosition.unsafeGet();
+                if (term.quantityType != QuantifierFixedCount) {
+                    term.frameLocation = currentCallFrameSize;
+                    currentCallFrameSize += YarrStackSpaceForBackTrackInfoCharacterClass;
+                    alternative->m_hasFixedSize = false;
+                } else
+                    currentInputPosition += term.quantityCount;
+                break;
+
+            case PatternTerm::TypeParenthesesSubpattern:
+                // Note: for fixed once parentheses we will ensure at least the minimum is available; others are on their own.
+                term.frameLocation = currentCallFrameSize;
+                if (term.quantityCount == 1 && !term.parentheses.isCopy) {
+                    if (term.quantityType != QuantifierFixedCount)
+                        currentCallFrameSize += YarrStackSpaceForBackTrackInfoParenthesesOnce;
+                    currentCallFrameSize = setupDisjunctionOffsets(term.parentheses.disjunction, currentCallFrameSize, currentInputPosition.unsafeGet());
+                    // If quantity is fixed, then pre-check its minimum size.
+                    if (term.quantityType == QuantifierFixedCount)
+                        currentInputPosition += term.parentheses.disjunction->m_minimumSize;
+                    term.inputPosition = currentInputPosition.unsafeGet();
+                } else if (term.parentheses.isTerminal) {
+                    currentCallFrameSize += YarrStackSpaceForBackTrackInfoParenthesesTerminal;
+                    currentCallFrameSize = setupDisjunctionOffsets(term.parentheses.disjunction, currentCallFrameSize, currentInputPosition.unsafeGet());
+                    term.inputPosition = currentInputPosition.unsafeGet();
+                } else {
+                    term.inputPosition = currentInputPosition.unsafeGet();
+                    setupDisjunctionOffsets(term.parentheses.disjunction, 0, currentInputPosition.unsafeGet());
+                    currentCallFrameSize += YarrStackSpaceForBackTrackInfoParentheses;
+                }
+                // Fixed count of 1 could be accepted, if they have a fixed size *AND* if all alternatives are of the same length.
+                alternative->m_hasFixedSize = false;
+                break;
+
+            case PatternTerm::TypeParentheticalAssertion:
+                term.inputPosition = currentInputPosition.unsafeGet();
+                term.frameLocation = currentCallFrameSize;
+                currentCallFrameSize = setupDisjunctionOffsets(term.parentheses.disjunction, currentCallFrameSize + YarrStackSpaceForBackTrackInfoParentheticalAssertion, currentInputPosition.unsafeGet());
+                break;
+
+            case PatternTerm::TypeDotStarEnclosure:
+                alternative->m_hasFixedSize = false;
+                term.inputPosition = initialInputPosition;
+                break;
+            }
+        }
+
+        alternative->m_minimumSize = (currentInputPosition - initialInputPosition).unsafeGet();
+        return currentCallFrameSize;
+    }
+
+    unsigned setupDisjunctionOffsets(PatternDisjunction* disjunction, unsigned initialCallFrameSize, unsigned initialInputPosition)
+    {
+        if ((disjunction != m_pattern.m_body) && (disjunction->m_alternatives.size() > 1))
+            initialCallFrameSize += YarrStackSpaceForBackTrackInfoAlternative;
+
+        unsigned minimumInputSize = UINT_MAX;
+        unsigned maximumCallFrameSize = 0;
+        bool hasFixedSize = true;
+
+        for (unsigned alt = 0; alt < disjunction->m_alternatives.size(); ++alt) {
+            PatternAlternative* alternative = disjunction->m_alternatives[alt];
+            unsigned currentAlternativeCallFrameSize = setupAlternativeOffsets(alternative, initialCallFrameSize, initialInputPosition);
+            minimumInputSize = min(minimumInputSize, alternative->m_minimumSize);
+            maximumCallFrameSize = max(maximumCallFrameSize, currentAlternativeCallFrameSize);
+            hasFixedSize &= alternative->m_hasFixedSize;
+        }
+        
+        ASSERT(minimumInputSize != UINT_MAX);
+        ASSERT(maximumCallFrameSize >= initialCallFrameSize);
+
+        disjunction->m_hasFixedSize = hasFixedSize;
+        disjunction->m_minimumSize = minimumInputSize;
+        disjunction->m_callFrameSize = maximumCallFrameSize;
+        return maximumCallFrameSize;
+    }
+
+    void setupOffsets()
+    {
+        setupDisjunctionOffsets(m_pattern.m_body, 0, 0);
+    }
+
+    // This optimization identifies sets of parentheses that we will never need to backtrack.
+    // In these cases we do not need to store state from prior iterations.
+    // We can presently avoid backtracking for:
+    //   * where the parens are at the end of the regular expression (last term in any of the
+    //     alternatives of the main body disjunction).
+    //   * where the parens are non-capturing, and quantified unbounded greedy (*).
+    //   * where the parens do not contain any capturing subpatterns.
+    void checkForTerminalParentheses()
+    {
+        // This check is much too crude; should be just checking whether the candidate
+        // node contains nested capturing subpatterns, not the whole expression!
+        if (m_pattern.m_numSubpatterns)
+            return;
+
+        Vector<PatternAlternative*>& alternatives = m_pattern.m_body->m_alternatives;
+        for (size_t i = 0; i < alternatives.size(); ++i) {
+            Vector<PatternTerm>& terms = alternatives[i]->m_terms;
+            if (terms.size()) {
+                PatternTerm& term = terms.last();
+                if (term.type == PatternTerm::TypeParenthesesSubpattern
+                    && term.quantityType == QuantifierGreedy
+                    && term.quantityCount == quantifyInfinite
+                    && !term.capture())
+                    term.parentheses.isTerminal = true;
+            }
+        }
+    }
+
+    void optimizeBOL()
+    {
+        // Look for expressions containing beginning of line (^) anchoring and unroll them.
+        // e.g. /^a|^b|c/ becomes /^a|^b|c/ which is executed once followed by /c/ which loops
+        // This code relies on the parsing code tagging alternatives with m_containsBOL and
+        // m_startsWithBOL and rolling those up to containing alternatives.
+        // At this point, this is only valid for non-multiline expressions.
+        PatternDisjunction* disjunction = m_pattern.m_body;
+        
+        if (!m_pattern.m_containsBOL || m_pattern.m_multiline)
+            return;
+        
+        PatternDisjunction* loopDisjunction = copyDisjunction(disjunction, true);
+
+        // Set alternatives in disjunction to "onceThrough"
+        for (unsigned alt = 0; alt < disjunction->m_alternatives.size(); ++alt)
+            disjunction->m_alternatives[alt]->setOnceThrough();
+
+        if (loopDisjunction) {
+            // Move alternatives from loopDisjunction to disjunction
+            for (unsigned alt = 0; alt < loopDisjunction->m_alternatives.size(); ++alt)
+                disjunction->m_alternatives.append(loopDisjunction->m_alternatives[alt]);
+                
+            loopDisjunction->m_alternatives.clear();
+        }
+    }
+
+    bool containsCapturingTerms(PatternAlternative* alternative, size_t firstTermIndex, size_t lastTermIndex)
+    {
+        Vector<PatternTerm>& terms = alternative->m_terms;
+
+        for (size_t termIndex = firstTermIndex; termIndex <= lastTermIndex; ++termIndex) {
+            PatternTerm& term = terms[termIndex];
+
+            if (term.m_capture)
+                return true;
+
+            if (term.type == PatternTerm::TypeParenthesesSubpattern) {
+                PatternDisjunction* nestedDisjunction = term.parentheses.disjunction;
+                for (unsigned alt = 0; alt < nestedDisjunction->m_alternatives.size(); ++alt) {
+                    if (containsCapturingTerms(nestedDisjunction->m_alternatives[alt], 0, nestedDisjunction->m_alternatives[alt]->m_terms.size() - 1))
+                        return true;
+                }
+            }
+        }
+
+        return false;
+    }
+
+    // This optimization identifies alternatives in the form of 
+    // [^].*[?]<expression>.*[$] for expressions that don't have any 
+    // capturing terms. The alternative is changed to <expression> 
+    // followed by processing of the dot stars to find and adjust the 
+    // beginning and the end of the match.
+    void optimizeDotStarWrappedExpressions()
+    {
+        Vector<PatternAlternative*>& alternatives = m_pattern.m_body->m_alternatives;
+        if (alternatives.size() != 1)
+            return;
+
+        PatternAlternative* alternative = alternatives[0];
+        Vector<PatternTerm>& terms = alternative->m_terms;
+        if (terms.size() >= 3) {
+            bool startsWithBOL = false;
+            bool endsWithEOL = false;
+            size_t termIndex, firstExpressionTerm, lastExpressionTerm;
+
+            termIndex = 0;
+            if (terms[termIndex].type == PatternTerm::TypeAssertionBOL) {
+                startsWithBOL = true;
+                ++termIndex;
+            }
+            
+            PatternTerm& firstNonAnchorTerm = terms[termIndex];
+            if ((firstNonAnchorTerm.type != PatternTerm::TypeCharacterClass) || (firstNonAnchorTerm.characterClass != m_pattern.newlineCharacterClass()) || !((firstNonAnchorTerm.quantityType == QuantifierGreedy) || (firstNonAnchorTerm.quantityType == QuantifierNonGreedy)))
+                return;
+            
+            firstExpressionTerm = termIndex + 1;
+            
+            termIndex = terms.size() - 1;
+            if (terms[termIndex].type == PatternTerm::TypeAssertionEOL) {
+                endsWithEOL = true;
+                --termIndex;
+            }
+            
+            PatternTerm& lastNonAnchorTerm = terms[termIndex];
+            if ((lastNonAnchorTerm.type != PatternTerm::TypeCharacterClass) || (lastNonAnchorTerm.characterClass != m_pattern.newlineCharacterClass()) || (lastNonAnchorTerm.quantityType != QuantifierGreedy))
+                return;
+            
+            lastExpressionTerm = termIndex - 1;
+
+            if (firstExpressionTerm > lastExpressionTerm)
+                return;
+
+            if (!containsCapturingTerms(alternative, firstExpressionTerm, lastExpressionTerm)) {
+                for (termIndex = terms.size() - 1; termIndex > lastExpressionTerm; --termIndex)
+                    terms.remove(termIndex);
+
+                for (termIndex = firstExpressionTerm; termIndex > 0; --termIndex)
+                    terms.remove(termIndex - 1);
+
+                terms.append(PatternTerm(startsWithBOL, endsWithEOL));
+                
+                m_pattern.m_containsBOL = false;
+            }
+        }
+    }
+
+private:
+    YarrPattern& m_pattern;
+    PatternAlternative* m_alternative;
+    CharacterClassConstructor m_characterClassConstructor;
+    bool m_invertCharacterClass;
+    bool m_invertParentheticalAssertion;
+};
+
+const char* YarrPattern::compile(const UString& patternString)
+{
+    YarrPatternConstructor constructor(*this);
+
+    if (const char* error = parse(constructor, patternString))
+        return error;
+    
+    // If the pattern contains illegal backreferences reset & reparse.
+    // Quoting Netscape's "What's new in JavaScript 1.2",
+    //      "Note: if the number of left parentheses is less than the number specified
+    //       in \#, the \# is taken as an octal escape as described in the next row."
+    if (containsIllegalBackReference()) {
+        unsigned numSubpatterns = m_numSubpatterns;
+
+        constructor.reset();
+#if !ASSERT_DISABLED
+        const char* error =
+#endif
+            parse(constructor, patternString, numSubpatterns);
+
+        ASSERT(!error);
+        ASSERT(numSubpatterns == m_numSubpatterns);
+    }
+
+    constructor.checkForTerminalParentheses();
+    constructor.optimizeDotStarWrappedExpressions();
+    constructor.optimizeBOL();
+        
+    constructor.setupOffsets();
+
+    return 0;
+}
+
+YarrPattern::YarrPattern(const UString& pattern, bool ignoreCase, bool multiline, const char** error)
+    : m_ignoreCase(ignoreCase)
+    , m_multiline(multiline)
+    , m_containsBackreferences(false)
+    , m_containsBOL(false)
+    , m_numSubpatterns(0)
+    , m_maxBackReference(0)
+    , newlineCached(0)
+    , digitsCached(0)
+    , spacesCached(0)
+    , wordcharCached(0)
+    , nondigitsCached(0)
+    , nonspacesCached(0)
+    , nonwordcharCached(0)
+{
+    *error = compile(pattern);
+}
+
+} }