src/direction_func.h

   1 /* $Id$ */
   2
   3 /*
   4  * This file is part of OpenTTD.
   5  * 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.
   6  * 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.
   7  * 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/>.
   8  */
   9
  10 /** @file direction_func.h Different functions related to conversions between directions. */
  11
  12 #ifndef DIRECTION_FUNC_H
  13 #define DIRECTION_FUNC_H
  14
  15 #include "direction_type.h"
  16
  17 /**
  18  * Return the reverse of a direction
  19  *
  20  * @param d The direction to get the reverse from
  21  * @return The reverse Direction
  22  */
  23 static inline Direction ReverseDir(Direction d)
  24 {
  25         return (Direction)(4 ^ d);
  26 }
  27
  28
  29 /**
  30  * Calculate the difference between to directions
  31  *
  32  * @param d0 The first direction as the base
  33  * @param d1 The second direction as the offset from the base
  34  * @return The difference how the second directions drifts of the first one.
  35  */
  36 static inline DirDiff DirDifference(Direction d0, Direction d1)
  37 {
  38         /* Cast to uint so compiler can use bitmask. If the difference is negative
  39          * and we used int instead of uint, further "+ 8" would have to be added. */
  40         return (DirDiff)((uint)(d0 - d1) % 8);
  41 }
  42
  43 /**
  44  * Applies two differences together
  45  *
  46  * This function adds two differences together and return the resulting
  47  * difference. So adding two DIRDIFF_REVERSE together results in the
  48  * DIRDIFF_SAME difference.
  49  *
  50  * @param d The first difference
  51  * @param delta The second difference to add on
  52  * @return The resulting difference
  53  */
  54 static inline DirDiff ChangeDirDiff(DirDiff d, DirDiff delta)
  55 {
  56         /* Cast to uint so compiler can use bitmask. Result can never be negative. */
  57         return (DirDiff)((uint)(d + delta) % 8);
  58 }
  59
  60 /**
  61  * Change a direction by a given difference
  62  *
  63  * This functions returns a new direction of the given direction
  64  * which is rotated by the given difference.
  65  *
  66  * @param d The direction to get a new direction from
  67  * @param delta The offset/drift applied to the direction
  68  * @return The new direction
  69  */
  70 static inline Direction ChangeDir(Direction d, DirDiff delta)
  71 {
  72         /* Cast to uint so compiler can use bitmask. Result can never be negative. */
  73         return (Direction)((uint)(d + delta) % 8);
  74 }
  75
  76
  77 /**
  78  * Returns the reverse direction of the given DiagDirection
  79  *
  80  * @param d The DiagDirection to get the reverse from
  81  * @return The reverse direction
  82  */
  83 static inline DiagDirection ReverseDiagDir(DiagDirection d)
  84 {
  85         return (DiagDirection)(2 ^ d);
  86 }
  87
  88
  89 /**
  90  * Applies a difference on a DiagDirection
  91  *
  92  * This function applies a difference on a DiagDirection and returns
  93  * the new DiagDirection.
  94  *
  95  * @param d The DiagDirection
  96  * @param delta The difference to apply on
  97  * @return The new direction which was calculated
  98  */
  99 static inline DiagDirection ChangeDiagDir(DiagDirection d, DiagDirDiff delta)
 100 {
 101         /* Cast to uint so compiler can use bitmask. Result can never be negative. */
 102         return (DiagDirection)((uint)(d + delta) % 4);
 103 }
 104
 105 /**
 106  * Convert a Direction to a DiagDirection.
 107  *
 108  * This function can be used to convert the 8-way Direction to
 109  * the 4-way DiagDirection. If the direction cannot be mapped its
 110  * "rounded clockwise". So DIR_N becomes DIAGDIR_NE.
 111  *
 112  * @param dir The direction to convert
 113  * @return The resulting DiagDirection, maybe "rounded clockwise".
 114  */
 115 static inline DiagDirection DirToDiagDir(Direction dir)
 116 {
 117         return (DiagDirection)(dir >> 1);
 118 }
 119
 120 /**
 121  * Convert a DiagDirection to a Direction.
 122  *
 123  * This function can be used to convert the 4-way DiagDirection
 124  * to the 8-way Direction. As 4-way are less than 8-way not all
 125  * possible directions can be calculated.
 126  *
 127  * @param dir The direction to convert
 128  * @return The resulting Direction
 129  */
 130 static inline Direction DiagDirToDir(DiagDirection dir)
 131 {
 132         return (Direction)(dir * 2 + 1);
 133 }
 134
 135
 136 /**
 137  * Select the other axis as provided.
 138  *
 139  * This is basically the not-operator for the axis.
 140  *
 141  * @param a The given axis
 142  * @return The other axis
 143  */
 144 static inline Axis OtherAxis(Axis a)
 145 {
 146         return (Axis)(a ^ 1);
 147 }
 148
 149
 150 /**
 151  * Convert a DiagDirection to the axis.
 152  *
 153  * This function returns the axis which belongs to the given
 154  * DiagDirection. The axis X belongs to the DiagDirection
 155  * north-east and south-west.
 156  *
 157  * @param d The DiagDirection
 158  * @return The axis which belongs to the direction
 159  */
 160 static inline Axis DiagDirToAxis(DiagDirection d)
 161 {
 162         return (Axis)(d & 1);
 163 }
 164
 165
 166 /**
 167  * Converts an Axis to a DiagDirection
 168  *
 169  * This function returns the DiagDirection which
 170  * belongs to the axis. As 2 directions are mapped to an axis
 171  * this function returns the one which points to south,
 172  * either south-west (on X axis) or south-east (on Y axis)
 173  *
 174  * @param a The axis
 175  * @return The direction pointed to south
 176  */
 177 static inline DiagDirection AxisToDiagDir(Axis a)
 178 {
 179         return (DiagDirection)(2 - a);
 180 }
 181
 182 /**
 183  * Converts an Axis to a Direction
 184  *
 185  * This function returns the Direction which
 186  * belongs to the axis. As 2 directions are mapped to an axis
 187  * this function returns the one which points to south,
 188  * either south-west (on X axis) or south-east (on Y axis)
 189  *
 190  * @param a The axis
 191  * @return The direction pointed to south
 192  */
 193 static inline Direction AxisToDirection(Axis a)
 194 {
 195         return (Direction)(5 - 2 * a);
 196 }
 197
 198 /**
 199  * Checks if an integer value is a valid DiagDirection
 200  *
 201  * @param d The value to check
 202  * @return True if the value belongs to a DiagDirection, else false
 203  */
 204 static inline bool IsValidDiagDirection(DiagDirection d)
 205 {
 206         return d < DIAGDIR_END;
 207 }
 208
 209 /**
 210  * Checks if an integer value is a valid Direction
 211  *
 212  * @param d The value to check
 213  * @return True if the value belongs to a Direction, else false
 214  */
 215 static inline bool IsValidDirection(Direction d)
 216 {
 217         return d < DIR_END;
 218 }
 219
 220 /**
 221  * Checks if an integer value is a valid Axis
 222  *
 223  * @param d The value to check
 224  * @return True if the value belongs to an Axis, else false
 225  */
 226 static inline bool IsValidAxis(Axis d)
 227 {
 228         return d < AXIS_END;
 229 }
 230
 231 /**
 232  * Checks if a given Direction is diagonal.
 233  *
 234  * @param dir The given direction.
 235  * @return True if the direction is diagonal.
 236  */
 237 static inline bool IsDiagonalDirection(Direction dir)
 238 {
 239         return (dir & 1) != 0;
 240 }
 241
 242 #endif /* DIRECTION_FUNC_H */