third_party/WebKit/Source/core/html/parser/InputStreamPreprocessor.h

/*
 * Copyright (C) 2008 Apple Inc. All Rights Reserved.
 * Copyright (C) 2009 Torch Mobile, Inc. http://www.torchmobile.com/
 * Copyright (C) 2013 Google, Inc. All Rights Reserved.
 *
 * 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.
 */

#ifndef InputStreamPreprocessor_h
#define InputStreamPreprocessor_h

#include "platform/text/SegmentedString.h"
#include "wtf/Allocator.h"
#include "wtf/Noncopyable.h"

namespace blink {

const LChar kEndOfFileMarker = 0;

// http://www.whatwg.org/specs/web-apps/current-work/#preprocessing-the-input-stream
template <typename Tokenizer>
class InputStreamPreprocessor {
  DISALLOW_NEW();
  WTF_MAKE_NONCOPYABLE(InputStreamPreprocessor);

 public:
  InputStreamPreprocessor(Tokenizer* tokenizer) : m_tokenizer(tokenizer) {
    reset();
  }

  ALWAYS_INLINE UChar nextInputCharacter() const {
    return m_nextInputCharacter;
  }

  // Returns whether we succeeded in peeking at the next character.
  // The only way we can fail to peek is if there are no more
  // characters in |source| (after collapsing \r\n, etc).
  ALWAYS_INLINE bool peek(SegmentedString& source) {
    m_nextInputCharacter = source.currentChar();

    // Every branch in this function is expensive, so we have a
    // fast-reject branch for characters that don't require special
    // handling. Please run the parser benchmark whenever you touch
    // this function. It's very hot.
    static const UChar specialCharacterMask = '\n' | '\r' | '\0';
    if (m_nextInputCharacter & ~specialCharacterMask) {
      m_skipNextNewLine = false;
      return true;
    }
    return processNextInputCharacter(source);
  }

  // Returns whether there are more characters in |source| after advancing.
  ALWAYS_INLINE bool advance(SegmentedString& source) {
    source.advanceAndUpdateLineNumber();
    if (source.isEmpty())
      return false;
    return peek(source);
  }

  bool skipNextNewLine() const { return m_skipNextNewLine; }

  void reset(bool skipNextNewLine = false) {
    m_nextInputCharacter = '\0';
    m_skipNextNewLine = skipNextNewLine;
  }

 private:
  bool processNextInputCharacter(SegmentedString& source) {
  ProcessAgain:
    ASSERT(m_nextInputCharacter == source.currentChar());

    if (m_nextInputCharacter == '\n' && m_skipNextNewLine) {
      m_skipNextNewLine = false;
      source.advancePastNewlineAndUpdateLineNumber();
      if (source.isEmpty())
        return false;
      m_nextInputCharacter = source.currentChar();
    }
    if (m_nextInputCharacter == '\r') {
      m_nextInputCharacter = '\n';
      m_skipNextNewLine = true;
    } else {
      m_skipNextNewLine = false;
      // FIXME: The spec indicates that the surrogate pair range as well as a
      // number of specific character values are parse errors and should be
      // replaced by the replacement character. We suspect this is a problem
      // with the spec as doing that filtering breaks surrogate pair handling
      // and causes us not to match Minefield.
      if (m_nextInputCharacter == '\0' &&
          !shouldTreatNullAsEndOfFileMarker(source)) {
        if (m_tokenizer->shouldSkipNullCharacters()) {
          source.advancePastNonNewline();
          if (source.isEmpty())
            return false;
          m_nextInputCharacter = source.currentChar();
          goto ProcessAgain;
        }
        m_nextInputCharacter = 0xFFFD;
      }
    }
    return true;
  }

  bool shouldTreatNullAsEndOfFileMarker(SegmentedString& source) const {
    return source.isClosed() && source.length() == 1;
  }

  Tokenizer* m_tokenizer;

  // http://www.whatwg.org/specs/web-apps/current-work/#next-input-character
  UChar m_nextInputCharacter;
  bool m_skipNextNewLine;
};

}  // namespace blink

#endif  // InputStreamPreprocessor_h