/// <summary>
/// 从低位向高位扫描，返回第一次出现1的位置，同时将该位置为0
/// 例如：二进制数 （高位在右）0001001001100（低位在左），返回2，同时bb更改为0001001001000
/// </summary>
/// <param name="u64">一个64位整数，注意：不能为0</param>
/// <returns>返回值从0到63, 最低的1所在的位置</returns>
public static int BitScanForwardWithReset(ref ulong u64)
{ // also called dropForward
int idx = BitHack64.BitScanForward(u64);
u64 &= u64 - 1; // reset bit outside
return(idx);
}
/// <summary>
/// 得到棋子的类型，是7种类型之一，实际对应着从1到7的整数
/// 通过把它们从0到6编号，可以在编程中减少许多if...else if或switch语句
/// </summary>
/// <param name="piece">棋子的ID号：RED_ROOK,RED_KNIGHT,...RED_KING,BLACK_ROOK,BLACK_KNIGHT,...BLACK_KING</param>
/// <returns>返回TYPE_ROOK,...TYPE_KING这7个整数之一；其它情况都返回-1</returns>
public static int PieceType(int piece)
{
// 提高性能，因为b0,b1,...,b6分别代表不同的棋子，这样只要找到1出现的位置就是棋子的类型
// 参看TYPE_ROOK和RED_ROOK, BLACK_ROOK等常量的定义即可
return(BitHack64.Log2((ulong)piece & 0x7F));
//if (piece == RED_ROOK) return TYPE_ROOK;
//else if (piece == RED_KNIGHT) return TYPE_KNIGHT;
//else if (piece == RED_CANNON) return TYPE_CANNON;
//else if (piece == RED_BISHOP) return TYPE_BISHOP;
//else if (piece == RED_ADVISOR) return TYPE_ADVISOR;
//else if (piece == RED_PAWN) return TYPE_PAWN;
//else if (piece == RED_KING) return TYPE_KING;
//else if (piece == BLACK_ROOK) return TYPE_ROOK;
//else if (piece == BLACK_KNIGHT) return TYPE_KNIGHT;
//else if (piece == BLACK_CANNON) return TYPE_CANNON;
//else if (piece == BLACK_BISHOP) return TYPE_BISHOP;
//else if (piece == BLACK_ADVISOR) return TYPE_ADVISOR;
//else if (piece == BLACK_PAWN) return TYPE_PAWN;
//else if (piece == BLACK_KING) return TYPE_KING;
//else return -1;
}
