hphp/util/map-walker.h

   1 /*
   2    +----------------------------------------------------------------------+
   3    | HipHop for PHP                                                       |
   4    +----------------------------------------------------------------------+
   5    | Copyright (c) 2010-2013 Facebook, Inc. (http://www.facebook.com)     |
   6    +----------------------------------------------------------------------+
   7    | This source file is subject to version 3.01 of the PHP license,      |
   8    | that is bundled with this package in the file LICENSE, and is        |
   9    | available through the world-wide-web at the following url:           |
  10    | http://www.php.net/license/3_01.txt                                  |
  11    | If you did not receive a copy of the PHP license and are unable to   |
  12    | obtain it through the world-wide-web, please send a note to          |
  13    | license@php.net so we can mail you a copy immediately.               |
  14    +----------------------------------------------------------------------+
  15 */
  16
  17 #ifndef incl_HPHP_UTIL_MAPWALKER_H_
  18 #define incl_HPHP_UTIL_MAPWALKER_H_
  19
  20 namespace HPHP {
  21
  22 /*
  23  * MapWalker is designed to iterate over an ordered map and an ordered list of
  24  * keys in parallel. Once created with a reference to a map, hasNext(key) will
  25  * return true iff the next item in the map matches the given key. If it
  26  * returns true, next() will return a reference to that element and advance its
  27  * internal iterator. hasNext() can be used to check if the internal iterator
  28  * is at the end of the map.
  29  */
  30 template<typename Map>
  31 struct MapWalker {
  32   typedef typename Map::key_type Key;
  33   typedef typename Map::mapped_type Value;
  34   typedef typename Map::const_iterator ConstIter;
  35
  36   explicit MapWalker(const Map& m)
  37     : m_map(m)
  38     , m_iter(m.begin())
  39   {}
  40
  41   bool hasNext() const {
  42     return m_iter != m_map.end();
  43   }
  44
  45   bool hasNext(const Key& key) const {
  46     assert(m_iter == m_map.end() || key <= m_iter->first);
  47     return m_iter != m_map.end() && m_iter->first == key;
  48   }
  49
  50   const Value& next() {
  51     assert(m_iter != m_map.end());
  52     auto const& val = m_iter->second;
  53     ++m_iter;
  54     return val;
  55   }
  56
  57  private:
  58   const Map& m_map;
  59   ConstIter m_iter;
  60 };
  61
  62 template<typename Map>
  63 MapWalker<Map> makeMapWalker(const Map& m) {
  64   return MapWalker<Map>(m);
  65 }
  66
  67 }
  68
  69 #endif