rockbox/apps/codecs/libwma/wmafixed.c

/****************************************************************************
 *             __________               __   ___.
 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
 *                     \/            \/     \/    \/            \/
 *
 * Copyright (C) 2007 Michael Giacomelli
 *
 * 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 software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ****************************************************************************/

#include "wmadec.h"
#include "wmafixed.h"
#include <codecs.h>

fixed64 IntTo64(int x){
    fixed64 res = 0;
    unsigned char *p = (unsigned char *)&res;

#ifdef ROCKBOX_BIG_ENDIAN
    p[5] = x & 0xff;
    p[4] = (x & 0xff00)>>8;
    p[3] = (x & 0xff0000)>>16;
    p[2] = (x & 0xff000000)>>24;
#else
    p[2] = x & 0xff;
    p[3] = (x & 0xff00)>>8;
    p[4] = (x & 0xff0000)>>16;
    p[5] = (x & 0xff000000)>>24;
#endif
    return res;
}

int IntFrom64(fixed64 x)
{
    int res = 0;
    unsigned char *p = (unsigned char *)&x;

#ifdef ROCKBOX_BIG_ENDIAN
    res = p[5] | (p[4]<<8) | (p[3]<<16) | (p[2]<<24);
#else
    res = p[2] | (p[3]<<8) | (p[4]<<16) | (p[5]<<24);
#endif
    return res;
}

fixed32 Fixed32From64(fixed64 x)
{
  return x & 0xFFFFFFFF;
}

fixed64 Fixed32To64(fixed32 x)
{
  return (fixed64)x;
}

/*
    Not performance senstitive code here

*/

fixed32 fixdiv32(fixed32 x, fixed32 y)
{
    fixed64 temp;

    if(x == 0)
        return 0;
    if(y == 0)
        return 0x7fffffff;
    temp = x;
    temp <<= PRECISION;
    return (fixed32)(temp / y);
}

fixed64 fixdiv64(fixed64 x, fixed64 y)
{
    fixed64 temp;

    if(x == 0)
        return 0;
    if(y == 0)
        return 0x07ffffffffffffffLL;
    temp = x;
    temp <<= PRECISION64;
    return (fixed64)(temp / y);
}

 fixed32 fixsqrt32(fixed32 x)
{

    unsigned long r = 0, s, v = (unsigned long)x;

#define STEP(k) s = r + (1 << k * 2); r >>= 1; \
    if (s <= v) { v -= s; r |= (1 << k * 2); }

    STEP(15);
    STEP(14);
    STEP(13);
    STEP(12);
    STEP(11);
    STEP(10);
    STEP(9);
    STEP(8);
    STEP(7);
    STEP(6);
    STEP(5);
    STEP(4);
    STEP(3);
    STEP(2);
    STEP(1);
    STEP(0);

    return (fixed32)(r << (PRECISION / 2));
}


     static const long cordic_circular_gain = 0xb2458939; /* 0.607252929 */  
     
 /* Table of values of atan(2^-i) in 0.32 format fractions of pi where pi = 0xffffffff / 2 */    
 static const unsigned long atan_table[] = {     
     0x1fffffff, /* +0.785398163 (or pi/4) */    
     0x12e4051d, /* +0.463647609 */  
     0x09fb385b, /* +0.244978663 */  
     0x051111d4, /* +0.124354995 */  
     0x028b0d43, /* +0.062418810 */  
     0x0145d7e1, /* +0.031239833 */  
     0x00a2f61e, /* +0.015623729 */  
     0x00517c55, /* +0.007812341 */  
     0x0028be53, /* +0.003906230 */  
     0x00145f2e, /* +0.001953123 */  
     0x000a2f98, /* +0.000976562 */  
     0x000517cc, /* +0.000488281 */  
     0x00028be6, /* +0.000244141 */  
     0x000145f3, /* +0.000122070 */  
     0x0000a2f9, /* +0.000061035 */  
     0x0000517c, /* +0.000030518 */  
     0x000028be, /* +0.000015259 */  
     0x0000145f, /* +0.000007629 */  
     0x00000a2f, /* +0.000003815 */  
     0x00000517, /* +0.000001907 */  
     0x0000028b, /* +0.000000954 */  
     0x00000145, /* +0.000000477 */  
     0x000000a2, /* +0.000000238 */  
     0x00000051, /* +0.000000119 */  
     0x00000028, /* +0.000000060 */  
     0x00000014, /* +0.000000030 */  
     0x0000000a, /* +0.000000015 */  
     0x00000005, /* +0.000000007 */  
     0x00000002, /* +0.000000004 */  
     0x00000001, /* +0.000000002 */  
     0x00000000, /* +0.000000001 */  
     0x00000000, /* +0.000000000 */  
 };  
     
 /**     
  * Implements sin and cos using CORDIC rotation.    
  *  
  * @param phase has range from 0 to 0xffffffff, representing 0 and  
  *        2*pi respectively.    
  * @param cos return address for cos    
  * @return sin of phase, value is a signed value from LONG_MIN to LONG_MAX,     
  *         representing -1 and 1 respectively.  
  *  
  *        Gives at least 24 bits precision (last 2-8 bits or so are probably off)   
  */     
     
 long fsincos(unsigned long phase, fixed32 *cos)     
 {   
     int32_t x, x1, y, y1;   
     unsigned long z, z1;    
     int i;  
     
     /* Setup initial vector */  
     x = cordic_circular_gain;   
     y = 0;  
     z = phase;  
     
     /* The phase has to be somewhere between 0..pi for this to work right */    
     if (z < 0xffffffff / 4) {   
         /* z in first quadrant, z += pi/2 to correct */     
         x = -x;     
         z += 0xffffffff / 4;    
     } else if (z < 3 * (0xffffffff / 4)) {  
         /* z in third quadrant, z -= pi/2 to correct */     
         z -= 0xffffffff / 4;    
     } else {    
         /* z in fourth quadrant, z -= 3pi/2 to correct */   
         x = -x;     
         z -= 3 * (0xffffffff / 4);  
     }   
     
     /* Each iteration adds roughly 1-bit of extra precision */  
     for (i = 0; i < 31; i++) {  
         x1 = x >> i;    
         y1 = y >> i;    
         z1 = atan_table[i];     
     
         /* Decided which direction to rotate vector. Pivot point is pi/2 */     
         if (z >= 0xffffffff / 4) {  
             x -= y1;    
             y += x1;    
             z -= z1;    
         } else {    
             x += y1;    
             y -= x1;    
             z += z1;    
         }   
     }   
     
     if (cos)    
         *cos = x;   
     
     return y;   
 }