src/chess/knight.c

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2016 Mike Becker. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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 */

#include "knight.h"
#include "rules.h"
#include <stdlib.h>

bool knight_chkrules(const Move *move) {
    int dx = abs(move->fromfile - move->tofile);
    int dy = abs(move->fromrow - move->torow);
    
    return (dx == 2 && dy == 1) || (dx == 1 && dy == 2);
}

size_t knight_moves(const GameState *gamestate,
        Color c, Row r, File f, Move *moves) {

    size_t count = 0;
    const int offsets[8][2] = {
        { 2,  1},
        { 2, -1},
        {-2,  1},
        {-2, -1},
        { 1,  2},
        { 1, -2},
        {-1,  2},
        {-1, -2}
    };

    for (size_t i = 0 ; i < 8 ; i++) {
        int row = r + offsets[i][0];
        int file = f + offsets[i][1];

        if (isidx(row) && isidx(file)) {
            moves[count] = (Move){0};
            moves[count].piece = mkpiece(KNIGHT, c);
            moves[count].fromrow = r;
            moves[count].fromfile = f;
            moves[count].torow = row;
            moves[count].tofile = file;
            moves[count].capture = piece_at(gamestate, row, file) != 0;
            count++;
        }
    }

    return count;
}