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 two 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 direction 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 returns 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  * Calculate the difference between two DiagDirection values
  90  *
  91  * @param d0 The first direction as the base
  92  * @param d1 The second direction as the offset from the base
  93  * @return The difference how the second direction drifts of the first one.
  94  */
  95 static inline DiagDirDiff DiagDirDifference(DiagDirection d0, DiagDirection d1)
  96 {
  97         /* Cast to uint so compiler can use bitmask. Result can never be negative. */
  98         return (DiagDirDiff)((uint)(d0 - d1) % 4);
  99 }
 100
 101 /**
 102  * Applies a difference on a DiagDirection
 103  *
 104  * This function applies a difference on a DiagDirection and returns
 105  * the new DiagDirection.
 106  *
 107  * @param d The DiagDirection
 108  * @param delta The difference to apply on
 109  * @return The new direction which was calculated
 110  */
 111 static inline DiagDirection ChangeDiagDir(DiagDirection d, DiagDirDiff delta)
 112 {
 113         /* Cast to uint so compiler can use bitmask. Result can never be negative. */
 114         return (DiagDirection)((uint)(d + delta) % 4);
 115 }
 116
 117 /**
 118  * Convert a Direction to a DiagDirection.
 119  *
 120  * This function can be used to convert the 8-way Direction to
 121  * the 4-way DiagDirection. If the direction cannot be mapped its
 122  * "rounded clockwise". So DIR_N becomes DIAGDIR_NE.
 123  *
 124  * @param dir The direction to convert
 125  * @return The resulting DiagDirection, maybe "rounded clockwise".
 126  */
 127 static inline DiagDirection DirToDiagDir(Direction dir)
 128 {
 129         return (DiagDirection)(dir >> 1);
 130 }
 131
 132 /**
 133  * Convert a DiagDirection to a Direction.
 134  *
 135  * This function can be used to convert the 4-way DiagDirection
 136  * to the 8-way Direction. As 4-way are less than 8-way not all
 137  * possible directions can be calculated.
 138  *
 139  * @param dir The direction to convert
 140  * @return The resulting Direction
 141  */
 142 static inline Direction DiagDirToDir(DiagDirection dir)
 143 {
 144         return (Direction)(dir * 2 + 1);
 145 }
 146
 147
 148 /**
 149  * Select the other axis as provided.
 150  *
 151  * This is basically the not-operator for the axis.
 152  *
 153  * @param a The given axis
 154  * @return The other axis
 155  */
 156 static inline Axis OtherAxis(Axis a)
 157 {
 158         return (Axis)(a ^ 1);
 159 }
 160
 161
 162 /**
 163  * Convert a DiagDirection to the axis.
 164  *
 165  * This function returns the axis which belongs to the given
 166  * DiagDirection. The axis X belongs to the DiagDirection
 167  * north-east and south-west.
 168  *
 169  * @param d The DiagDirection
 170  * @return The axis which belongs to the direction
 171  */
 172 static inline Axis DiagDirToAxis(DiagDirection d)
 173 {
 174         return (Axis)(d & 1);
 175 }
 176
 177
 178 /**
 179  * Converts an Axis to a DiagDirection
 180  *
 181  * This function returns the DiagDirection which
 182  * belongs to the axis. As 2 directions are mapped to an axis
 183  * this function returns the one which points to south,
 184  * either south-west (on X axis) or south-east (on Y axis)
 185  *
 186  * @param a The axis
 187  * @return The direction pointed to south
 188  */
 189 static inline DiagDirection AxisToDiagDir(Axis a)
 190 {
 191         return (DiagDirection)(2 - a);
 192 }
 193
 194 /**
 195  * Checks if an integer value is a valid DiagDirection
 196  *
 197  * @param d The value to check
 198  * @return True if the value belongs to a DiagDirection, else false
 199  */
 200 static inline bool IsValidDiagDirection(DiagDirection d)
 201 {
 202         return d < DIAGDIR_END;
 203 }
 204
 205 /**
 206  * Checks if an integer value is a valid Direction
 207  *
 208  * @param d The value to check
 209  * @return True if the value belongs to a Direction, else false
 210  */
 211 static inline bool IsValidDirection(Direction d)
 212 {
 213         return d < DIR_END;
 214 }
 215
 216 /**
 217  * Checks if an integer value is a valid Axis
 218  *
 219  * @param d The value to check
 220  * @return True if the value belongs to an Axis, else false
 221  */
 222 static inline bool IsValidAxis(Axis d)
 223 {
 224         return d < AXIS_END;
 225 }
 226
 227 /**
 228  * Checks if a given Direction is diagonal.
 229  *
 230  * @param dir The given direction.
 231  * @return True if the direction is diagonal.
 232  */
 233 static inline bool IsDiagonalDirection(Direction dir)
 234 {
 235         return (dir & 1) != 0;
 236 }
 237
 238 #endif /* DIRECTION_FUNC_H */