text: /*
   * 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 THIRD_PARTY_BLINK_RENDERER_CORE_HTML_PARSER_INPUT_STREAM_PREPROCESSOR_H_
  #define THIRD_PARTY_BLINK_RENDERER_CORE_HTML_PARSER_INPUT_STREAM_PREPROCESSOR_H_
  
  #include "base/macros.h"
  #include "third_party/blink/renderer/platform/text/segmented_string.h"
  #include "third_party/blink/renderer/platform/wtf/allocator/allocator.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();
  
   public:
    explicit InputStreamPreprocessor(Tokenizer* tokenizer)
        : tokenizer_(tokenizer) {}
  
    // http://www.whatwg.org/specs/web-apps/current-work/#next-input-character
    // 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, UChar& cc) {
      cc = source.CurrentChar();
      return ProcessNextInputCharacter(source, cc);
    }
  
    // Returns whether there are more characters in |source| after advancing.
    ALWAYS_INLINE bool Advance(SegmentedString& source, UChar& cc) {
      cc = source.AdvanceAndUpdateLineNumber();
      return ProcessNextInputCharacter(source, cc);
    }
  
    ALWAYS_INLINE bool AdvancePastNonNewline(SegmentedString& source, UChar& cc) {
      cc = source.AdvancePastNonNewline();
      return ProcessNextInputCharacter(source, cc);
    }
  
    bool SkipNextNewLine() const { return skip_next_new_line_; }
  
    void Reset(bool skip_next_new_line = false) {
      skip_next_new_line_ = skip_next_new_line;
    }
  
   private:
    ALWAYS_INLINE bool ProcessNextInputCharacter(SegmentedString& source,
                                                 UChar& cc) {
      // 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 kSpecialCharacterMask = '\n' | '\r' | '\0';
      if (cc & ~kSpecialCharacterMask) {
        skip_next_new_line_ = false;
        return true;
      }
      // |source| will only be empty if it returns a null character
      // after advancing.
      if (source.IsEmpty())
        return false;
      return ProcessNextInputSpecialCharacter(source, cc);
    }
  
    bool ProcessNextInputSpecialCharacter(SegmentedString& source, UChar& cc) {
    ProcessAgain:
      DCHECK_EQ(cc, source.CurrentChar());
  
      if (cc == '\n' && skip_next_new_line_) {
        skip_next_new_line_ = false;
        cc = source.AdvancePastNewlineAndUpdateLineNumber();
        if (source.IsEmpty())
          return false;
      }
      if (cc == '\r') {
        cc = '\n';
        skip_next_new_line_ = true;
      } else {
        skip_next_new_line_ = 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 (cc == '\0' && !ShouldTreatNullAsEndOfFileMarker(source)) {
          if (tokenizer_->ShouldSkipNullCharacters()) {
            cc = source.AdvancePastNonNewline();
            if (source.IsEmpty())
              return false;
            goto ProcessAgain;
          }
          cc = 0xFFFD;
        }
      }
      return true;
    }
  
    bool ShouldTreatNullAsEndOfFileMarker(SegmentedString& source) const {
      return source.IsClosed() && source.length() == 1;
    }
  
    Tokenizer* tokenizer_;
    bool skip_next_new_line_ = false;
  
    DISALLOW_COPY_AND_ASSIGN(InputStreamPreprocessor);
  };
  
  }  // namespace blink
  
  #endif  // THIRD_PARTY_BLINK_RENDERER_CORE_HTML_PARSER_INPUT_STREAM_PREPROCESSOR_H_
  