# cmd_helper.h

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    00001 /* $Id$ */
    00002
    00003 /*
    00004  * This file is part of OpenTTD.
    00005  * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
    00006  * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
    00007  * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
    00008  */
    00009
    00012 #ifndef CMD_HELPER_H
    00013 #define CMD_HELPER_H
    00014
    00015 #include "direction_type.h"
    00016 #include "road_type.h"
    00017
    00018
    00019 template<uint N> static inline void ExtractValid();
    00020 template<> inline void ExtractValid<1>() {}
    00021
    00022
    00023 template<typename T> struct ExtractBits;
    00024 template<> struct ExtractBits<Axis>          { static const uint Count =  1; };
    00025 template<> struct ExtractBits<DiagDirection> { static const uint Count =  2; };
    00026 template<> struct ExtractBits<RoadBits>      { static const uint Count =  4; };
    00027
    00028
    00029 template<typename T, uint N, typename U> static inline T Extract(U v)
    00030 {
    00031   /* Check if there are enough bits in v */
    00032   ExtractValid<N + ExtractBits<T>::Count <= sizeof(U) * 8>();
    00033   return (T)GB(v, N, ExtractBits<T>::Count);
    00034 }
    00035
    00036 #endif