terminal-chess: src/chess/knight.c@6a26114297a1

     1 /*

     2  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.

     3  *

     4  * Copyright 2014 Mike Becker. All rights reserved.

     5  *

     6  * Redistribution and use in source and binary forms, with or without

     7  * modification, are permitted provided that the following conditions are met:

     8  *

     9  *   1. Redistributions of source code must retain the above copyright

    10  *      notice, this list of conditions and the following disclaimer.

    11  *

    12  *   2. Redistributions in binary form must reproduce the above copyright

    13  *      notice, this list of conditions and the following disclaimer in the

    14  *      documentation and/or other materials provided with the distribution.

    15  *

    16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

    17  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

    18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

    19  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE

    20  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

    21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

    22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

    23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

    24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

    25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

    26  * POSSIBILITY OF SUCH DAMAGE.

    27  *

    28  */

    30 #include "knight.h"

    31 #include "rules.h"

    32 #include <stdlib.h>

    34 _Bool knight_chkrules(Move *move) {

    35     int dx = abs(move->fromfile - move->tofile);

    36     int dy = abs(move->fromrow - move->torow);

    38     return (dx == 2 && dy == 1) || (dx == 1 && dy == 2);

    39 }

    41 static int knight_getloc_fixedrow(Board board, Move *move) {

    42     int d = 3 - abs(move->fromrow - move->torow);

    44     if (d == 1 || d == 2) {

    45         if (move->tofile < 6 &&

    46             board[move->fromrow][move->tofile + d] == move->piece) {

    47             if (move->fromfile == POS_UNSPECIFIED) {

    48                 move->fromfile = move->tofile + d;

    49                 return VALID_MOVE_SYNTAX;

    50             } else {

    51                 return AMBIGUOUS_MOVE;

    52             }

    53         }

    54         if (move->tofile > 1 &&

    55             board[move->fromrow][move->tofile - d] == move->piece) {

    56             if (move->fromfile == POS_UNSPECIFIED) {

    57                 move->fromfile = move->tofile - d;

    58                 return VALID_MOVE_SYNTAX;

    59             } else {

    60                 return AMBIGUOUS_MOVE;

    61             }

    62         }

    63     }

    65     return INVALID_POSITION;

    66 }

    68 static int knight_getloc_fixedfile(Board board, Move *move) {

    69     int d = 3 - abs(move->fromfile - move->tofile);

    71     if (d == 1 || d == 2) {

    72         if (move->torow < 6 &&

    73             board[move->torow + d][move->fromfile] == move->piece) {

    74             if (move->fromrow == POS_UNSPECIFIED) {

    75                 move->fromrow = move->torow + d;

    76                 return VALID_MOVE_SYNTAX;

    77             } else {

    78                 return AMBIGUOUS_MOVE;

    79             }

    80         }

    81         if (move->torow > 1 &&

    82             board[move->torow - d][move->fromfile] == move->piece) {

    83             if (move->fromrow == POS_UNSPECIFIED) {

    84                 move->fromrow = move->torow - d;

    85                 return VALID_MOVE_SYNTAX;

    86             } else {

    87                 return AMBIGUOUS_MOVE;

    88             }

    89         }

    90     }

    92     return INVALID_POSITION;

    93 }

    95 int knight_getlocation(Board board, Move *move) {

    97     if (move->fromfile != POS_UNSPECIFIED) {

    98         return knight_getloc_fixedfile(board, move);

    99     }

   101     if (move->fromrow != POS_UNSPECIFIED) {

   102         return knight_getloc_fixedrow(board, move);

   103     }

   105     for (int x = -2 ; x <= 2 ; x++) {

   106         if (x == 0) {

   107             continue;

   108         }

   109         for (int y = -2 ; y <= 2 ; y++) {

   110             if (y == 0 || y == x) {

   111                 continue;

   112             }

   113             uint8_t cx = move->tofile + x;

   114             uint8_t cy = move->torow + y;

   116             if (isidx(cx) && isidx(cy) && board[cy][cx] == move->piece) {

   117                 if (move->fromfile == POS_UNSPECIFIED

   118                     && move->fromrow == POS_UNSPECIFIED) {

   119                     move->fromfile = cx;

   120                     move->fromrow = cy;

   121                 } else {

   122                     return AMBIGUOUS_MOVE;

   123                 }

   124             }

   125         }

   126     }

   128     if (move->fromfile == POS_UNSPECIFIED || move->fromrow == POS_UNSPECIFIED) {

   129         return INVALID_POSITION;

   130     } else {

   131         return VALID_MOVE_SYNTAX;

   132     }

   133 }

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