text: /*
   * 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:
   *
   *     * Redistributions of source code must retain the above copyright
   * notice, this list of conditions and the following disclaimer.
   *     * 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.
   *     * Neither the name of Google Inc. nor the names of its
   * contributors may be used to endorse or promote products derived from
   * this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "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 THE COPYRIGHT
   * OWNER 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 WEEX_UIKIT_WTF_TEXT_STRINGVIEW_H_
  #define WEEX_UIKIT_WTF_TEXT_STRINGVIEW_H_
  
  #include "render/wtf/text/StringImpl.h"
  
  namespace WTF {
  
  class WTF_EXPORT StringView {
   public:
    StringView() : m_offset(0), m_length(0) {}
  
    explicit StringView(PassRefPtr<StringImpl> impl)
        : m_impl(impl), m_offset(0), m_length(m_impl->length()) {}
  
    StringView(PassRefPtr<StringImpl> impl, unsigned offset, unsigned length)
        : m_impl(impl), m_offset(offset), m_length(length) {
      ASSERT_WITH_SECURITY_IMPLICATION(offset + length <= m_impl->length());
    }
  
    void narrow(unsigned offset, unsigned length) {
      ASSERT_WITH_SECURITY_IMPLICATION(offset + length <= m_length);
      m_offset += offset;
      m_length = length;
    }
  
    bool isEmpty() const { return !m_length; }
    unsigned length() const { return m_length; }
  
    bool is8Bit() const { return m_impl->is8Bit(); }
  
    const LChar* characters8() const {
      if (!m_impl)
        return 0;
      ASSERT(is8Bit());
      return m_impl->characters8() + m_offset;
    }
  
    const UChar* characters16() const {
      if (!m_impl)
        return 0;
      ASSERT(!is8Bit());
      return m_impl->characters16() + m_offset;
    }
  
    PassRefPtr<StringImpl> toString() const {
      if (!m_impl)
        return m_impl;
      if (m_impl->is8Bit())
        return StringImpl::create(characters8(), m_length);
      return StringImpl::create(characters16(), m_length);
    }
  
   private:
    RefPtr<StringImpl> m_impl;
    unsigned m_offset;
    unsigned m_length;
  };
  
  }  // namespace WTF
  
  using WTF::StringView;
  
  #endif  // WEEX_UIKIT_WTF_TEXT_STRINGVIEW_H_
  