#ifndef _FIXP_ARITH_H
  #define _FIXP_ARITH_H
  
  /*

   * Simplistic fixed-point arithmetics.
   * Hmm, I'm probably duplicating some code :(
   *
   * Copyright (c) 2002 Johann Deneux
   */
  
  /*
   * This program 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; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program 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.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
   *
   * Should you need to contact me, the author, you can do so by

   * e-mail - mail your message to <johann.deneux@gmail.com>

   */
  
  #include <linux/types.h>

  /* The type representing fixed-point values */

  typedef s16 fixp_t;
  
  #define FRAC_N 8
  #define FRAC_MASK ((1<<FRAC_N)-1)

  /* Not to be used directly. Use fixp_{cos,sin} */
  static const fixp_t cos_table[46] = {

  	0x0100,	0x00FF,	0x00FF,	0x00FE,	0x00FD,	0x00FC,	0x00FA,	0x00F8,
  	0x00F6,	0x00F3,	0x00F0,	0x00ED,	0x00E9,	0x00E6,	0x00E2,	0x00DD,
  	0x00D9,	0x00D4,	0x00CF,	0x00C9,	0x00C4,	0x00BE,	0x00B8,	0x00B1,
  	0x00AB,	0x00A4,	0x009D,	0x0096,	0x008F,	0x0087,	0x0080,	0x0078,
  	0x0070,	0x0068,	0x005F,	0x0057,	0x004F,	0x0046,	0x003D,	0x0035,

  	0x002C,	0x0023,	0x001A,	0x0011,	0x0008, 0x0000

  };
  
  
  /* a: 123 -> 123.0 */
  static inline fixp_t fixp_new(s16 a)
  {
  	return a<<FRAC_N;
  }
  
  /* a: 0xFFFF -> -1.0
        0x8000 -> 1.0
        0x0000 -> 0.0
  */
  static inline fixp_t fixp_new16(s16 a)
  {
  	return ((s32)a)>>(16-FRAC_N);
  }
  
  static inline fixp_t fixp_cos(unsigned int degrees)
  {
  	int quadrant = (degrees / 90) & 3;
  	unsigned int i = degrees % 90;

  	if (quadrant == 1 || quadrant == 3)
  		i = 90 - i;

  
  	i >>= 1;
  
  	return (quadrant == 1 || quadrant == 2)? -cos_table[i] : cos_table[i];
  }
  
  static inline fixp_t fixp_sin(unsigned int degrees)
  {
  	return -fixp_cos(degrees + 90);
  }
  
  static inline fixp_t fixp_mult(fixp_t a, fixp_t b)
  {
  	return ((s32)(a*b))>>FRAC_N;
  }
  
  #endif