Iterator.h

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//------------------------------------------------------------------------------
/*
  https://github.com/vinniefalco/LuaBridge
 
  Copyright 2012, Vinnie Falco <vinnie.falco@gmail.com>
 
  License: The MIT License (http://www.opensource.org/licenses/mit-license.php)
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
 
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
*/
//==============================================================================
 
class Iterator
{
private:
  lua_State* m_L;
  LuaRef m_table;
  LuaRef m_key;
  LuaRef m_value;
 
  void next ()
  {
    m_table.push(m_L);
    m_key.push (m_L);
    if (lua_next (m_L, -2))
    {
      m_value.pop (m_L);
      m_key.pop (m_L);
    }
    else
    {
      m_key = Nil();
      m_value = Nil();
    }
    lua_pop(m_L, 1);
  }
 
public:
  explicit Iterator (LuaRef table)
    : m_L (table.state ())
    , m_table (table)
    , m_key (table.state ()) // m_key is nil
    , m_value (table.state ()) // m_value is nil
  {
    next (); // get the first (key, value) pair from table
  }
 
  lua_State* state () const
  {
    return m_L;
  }
 
  LuaRef operator* () const
  {
    return m_value;
  }
 
  LuaRef operator-> () const
  {
    return m_value;
  }
 
  Iterator& operator++ ()
  {
    if (isNil())
    {
      // if the iterator reaches the end, do nothing
      return *this;
    }
    else
    {
      next();
      return *this;
    }
  }
 
  inline bool isNil () const
  {
    return m_key.isNil ();
  }
 
  inline LuaRef key () const
  {
    return m_key;
  }
 
  inline LuaRef value () const
  {
    return m_value;
  }
 
private:
  // Don't use postfix increment, it is less efficient
  Iterator operator++ (int);
};