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

/*
 * Copyright (C) 2010 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 HTMLInputStream_h
#define HTMLInputStream_h

#include "core/html/parser/InputStreamPreprocessor.h"
#include "platform/text/SegmentedString.h"
#include "wtf/Allocator.h"

namespace blink {

// The InputStream is made up of a sequence of SegmentedStrings:
//
// [--current--][--next--][--next--] ... [--next--]
//            /\                         (also called m_last)
//            L_ current insertion point
//
// The current segmented string is stored in InputStream.  Each of the
// afterInsertionPoint buffers are stored in InsertionPointRecords on the stack.
//
// We remove characters from the "current" string in the InputStream.
// document.write() will add characters at the current insertion point, which
// appends them to the "current" string.
//
// m_last is a pointer to the last of the afterInsertionPoint strings. The
// network adds data at the end of the InputStream, which appends them to the
// "last" string.
class HTMLInputStream {
  DISALLOW_NEW();
  WTF_MAKE_NONCOPYABLE(HTMLInputStream);

 public:
  HTMLInputStream() : m_last(&m_first) {}

  void appendToEnd(const SegmentedString& string) { m_last->append(string); }

  void insertAtCurrentInsertionPoint(const SegmentedString& string) {
    m_first.append(string);
  }

  bool hasInsertionPoint() const { return &m_first != m_last; }

  void markEndOfFile() {
    m_last->append(SegmentedString(String(&kEndOfFileMarker, 1)));
    m_last->close();
  }

  void closeWithoutMarkingEndOfFile() { m_last->close(); }

  bool haveSeenEndOfFile() const { return m_last->isClosed(); }

  SegmentedString& current() { return m_first; }
  const SegmentedString& current() const { return m_first; }

  void splitInto(SegmentedString& next) {
    next = m_first;
    m_first = SegmentedString();
    if (m_last == &m_first) {
      // We used to only have one SegmentedString in the InputStream but now we
      // have two.  That means m_first is no longer also the m_last string,
      // |next| is now the last one.
      m_last = &next;
    }
  }

  void mergeFrom(SegmentedString& next) {
    m_first.append(next);
    if (m_last == &next) {
      // The string |next| used to be the last SegmentedString in
      // the InputStream.  Now that it's been merged into m_first,
      // that makes m_first the last one.
      m_last = &m_first;
    }
    if (next.isClosed()) {
      // We also need to merge the "closed" state from next to m_first.
      // Arguably, this work could be done in append().
      m_first.close();
    }
  }

 private:
  SegmentedString m_first;
  SegmentedString* m_last;
};

class InsertionPointRecord {
  STACK_ALLOCATED();
  WTF_MAKE_NONCOPYABLE(InsertionPointRecord);

 public:
  explicit InsertionPointRecord(HTMLInputStream& inputStream)
      : m_inputStream(&inputStream) {
    m_line = m_inputStream->current().currentLine();
    m_column = m_inputStream->current().currentColumn();
    m_inputStream->splitInto(m_next);
    // We 'fork' current position and use it for the generated script part. This
    // is a bit weird, because generated part does not have positions within an
    // HTML document.
    m_inputStream->current().setCurrentPosition(m_line, m_column, 0);
  }

  ~InsertionPointRecord() {
    // Some inserted text may have remained in input stream. E.g. if script has
    // written "&amp" or "<table", it stays in buffer because it cannot be
    // properly tokenized before we see next part.
    int unparsedRemainderLength = m_inputStream->current().length();
    m_inputStream->mergeFrom(m_next);
    // We restore position for the character that goes right after unparsed
    // remainder.
    m_inputStream->current().setCurrentPosition(m_line, m_column,
                                                unparsedRemainderLength);
  }

 private:
  HTMLInputStream* m_inputStream;
  SegmentedString m_next;
  OrdinalNumber m_line;
  OrdinalNumber m_column;
};

}  // namespace blink

#endif  // HTMLInputStream_h