Tic-Tac-Toe game written in C

tictactoe.c

#include <stdio.h>
void DrawBoard(int pieceMask, int playerMask);
int CheckWinner(int pieceMask, int playerMask);
int GetPlayerInput();
char Bit2OX(int bit);

void main()
{
    int boardPieceMask = 0, boardPlayerMask = 0;
    int player = 0;
    int winner = 0;
    while (!winner)
    {
        DrawBoard(boardPieceMask, boardPlayerMask);
        printf("It is %c's turn!\n", Bit2OX(player));
        int input = -1;
        while (input == -1)
        {
            input = GetPlayerInput();
            if (input != -1 && (boardPieceMask >> input) & 1)
            {
                printf("area is populated\n");
                input = -1;   
            }
        }
        boardPieceMask |= 0b1 << input;
        if (player)
            boardPlayerMask |= 0b1 << input;
        
        player = !player;
        winner = CheckWinner(boardPieceMask, boardPlayerMask);
        printf("\n\n");
    }
    DrawBoard(boardPieceMask, boardPlayerMask);
    printf("%c WINS!!!", Bit2OX(winner >> 1));
    
}

void DrawBoard(int pieceMask, int playerMask)
{
    int y, x;
    printf("    a   b   c\n");
    for (y = 0; y < 7; y++)
    {
        if (y % 2 == 0)
        {
            printf("  ");
            for (x = 0; x < 13; x++)
                printf("-");
        }
        else
        {
            printf("%d ", y/2 + 1);
            for (x = 0; x < 7; x++)
            {
                if (x % 2 == 0)
                    printf("| ");
                else
                {
                    char piece = ' ';
                    int bitOffset = x / 2 + y / 2 * 3;
                    if ((pieceMask >> bitOffset) & 1)
                        piece = Bit2OX((playerMask >> bitOffset) & 1);
                    printf("%c ", piece);
                }
            }
        }
        printf("\n");
    }
}

char Bit2OX(int bit)
{
    return bit ? 'O' : 'X';
}

int GetPlayerInput()
{
    char inX, inY;
    int coordIdx = -1;
    scanf(" %c%c", &inX, &inY);
    if (inX >= '1' && inX <= '3')
    {
        char temp = inX;
        inX = inY;
        inY = temp;
    }
    if (inX >= 'a' && inX <= 'c' && inY >= '1' && inY <= '3')
        coordIdx = inX - 'a' + (inY - '1') * 3;
    return coordIdx;
}

int CheckWinner(int piece_mask, int player_mask)
{
    const int WIN_CONDITIONS[8] = {
        0b001001001,
        0b010010010,
        0b100100100,
        0b000000111,
        0b000111000,
        0b111000000,
        0b100010001,
        0b001010100,
    };
    int i, result = 0;
    for (i = 0; !result && i < 8; i++)
    {
        int hasWon = (WIN_CONDITIONS[i] & piece_mask) == WIN_CONDITIONS[i];
        int winningPlayer = ((WIN_CONDITIONS[i] & player_mask) > 0);
        result = hasWon << winningPlayer;
    }
    return result;
}