1 // Copyright 2014 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef MEDIA_CAST_COMMON_MOD_UTIL_H_ 6 #define MEDIA_CAST_COMMON_MOD_UTIL_H_ 7 8 #include <map> 9 #include "base/logging.h" 10 11 namespace media { 12 namespace cast { 13 14 // MAP is a map<uint??, ...> where the unsigned integer is 15 // assumed to wrap around, but only a small range is used at a time. 16 // Return the oldest entry in the map. 17 template<class MAP> 18 typename MAP::iterator ModMapOldest(MAP* map) { 19 typename MAP::iterator ret = map->begin(); 20 if (ret != map->end()) { 21 typename MAP::key_type lower_quarter = 0; 22 lower_quarter--; 23 lower_quarter >>= 1; 24 if (ret->first < lower_quarter) { 25 typename MAP::iterator tmp = map->upper_bound(lower_quarter * 3); 26 if (tmp != map->end()) 27 ret = tmp; 28 } 29 } 30 return ret; 31 } 32 33 // MAP is a map<uint??, ...> where the unsigned integer is 34 // assumed to wrap around, but only a small range is used at a time. 35 // Returns the previous entry in the map. 36 template<class MAP> 37 typename MAP::iterator ModMapPrevious(MAP* map, typename MAP::iterator i) { 38 DCHECK(!map->empty()); 39 typename MAP::iterator ret = i; 40 if (i == map->begin()) { 41 ret = map->end(); 42 } 43 ret--; 44 if (i == ret) 45 return map->end(); 46 if ((i->first - ret->first) > ((typename MAP::key_type(0) - 1)) >> 1) 47 return map->end(); 48 return ret; 49 } 50 51 } // namespace cast 52 } // namespace media 53 54 #endif 55
