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#include <stdlib.h>
#include <inttypes.h>
/* Macros for converting between various fixed-point representations and floating point. */
#define ONE_16 (1L << 16)
#define fixtof64(x) (float)((float)(x) / (float)(1 << 16)) //does not work on int64_t!
#define ftofix32(x) ((int32_t)((x) * (float)(1 << 16) + ((x) < 0 ? -0.5 : 0.5)))
#define ftofix31(x) ((int32_t)((x) * (float)(1 << 31) + ((x) < 0 ? -0.5 : 0.5)))
#define fix31tof64(x) (float)((float)(x) / (float)(1 << 31))
/* Fixed point math routines for use in atrac3.c */
static inline int32_t fixmul16(int32_t x, int32_t y)
{
int64_t temp;
temp = x;
temp *= y;
temp >>= 16;
return (int32_t)temp;
}
static inline int32_t fixmul31(int32_t x, int32_t y)
{
int64_t temp;
temp = x;
temp *= y;
temp >>= 31; //16+31-16 = 31 bits
return (int32_t)temp;
}
static inline int32_t fixdiv16(int32_t x, int32_t y)
{
int64_t temp;
temp = x << 16;
temp /= y;
return (int32_t)temp;
}
/*
* Fast integer square root adapted from algorithm,
* Martin Guy @ UKC, June 1985.
* Originally from a book on programming abaci by Mr C. Woo.
* This is taken from :
* http://wiki.forum.nokia.com/index.php/How_to_use_fixed_point_maths#How_to_get_square_root_for_integers
* with a added shift up of the result by 8 bits to return result in 16.16 fixed-point representation.
*/
static inline int32_t fastSqrt(int32_t n)
{
/*
* Logically, these are unsigned.
* We need the sign bit to test
* whether (op - res - one) underflowed.
*/
int32_t op, res, one;
op = n;
res = 0;
/* "one" starts at the highest power of four <= than the argument. */
one = 1 << 30; /* second-to-top bit set */
while (one > op) one >>= 2;
while (one != 0)
{
if (op >= res + one)
{
op = op - (res + one);
res = res + (one<<1);
}
res >>= 1;
one >>= 2;
}
return(res << 8);
}
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