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/* Copyright (c) 1997-2001 Miller Puckette and others.
* For information on usage and redistribution, and for a DISCLAIMER OF ALL
* WARRANTIES, see the file, "LICENSE.txt," in this distribution. */
#include "d_math.h"
#include "m_pd.h"
#include <math.h>
/* sigrsqrt - reciprocal square root good to 8 mantissa bits */
static float rsqrt_exptab[DUMTAB1SIZE], rsqrt_mantissatab[DUMTAB2SIZE];
static void init_rsqrt(void)
{
int i;
for (i = 0; i < DUMTAB1SIZE; i++)
{
float f;
int32 l = (i ? (i == DUMTAB1SIZE-1 ? DUMTAB1SIZE-2 : i) : 1)<< 23;
*(int32 *)(&f) = l;
rsqrt_exptab[i] = 1./sqrt(f);
}
for (i = 0; i < DUMTAB2SIZE; i++)
{
float f = 1 + (1./DUMTAB2SIZE) * i;
rsqrt_mantissatab[i] = 1./sqrt(f);
}
}
typedef struct sigrsqrt
{
t_object x_obj;
t_float x_f;
} t_sigrsqrt;
static t_class *sigrsqrt_class;
static void *sigrsqrt_new(void)
{
t_sigrsqrt *x = (t_sigrsqrt *)pd_new(sigrsqrt_class);
outlet_new(&x->x_obj, gensym("signal"));
x->x_f = 0;
return (x);
}
static t_int *sigrsqrt_perform(t_int *w)
{
t_sample *in = *(t_sample **)(w+1), *out = *(t_sample **)(w+2);
t_int n = *(t_int *)(w+3);
while (n--)
{
t_sample f = *in;
long l = *(long *)(in++);
if (f < 0) *out++ = 0;
else
{
t_sample g = rsqrt_exptab[(l >> 23) & 0xff] *
rsqrt_mantissatab[(l >> 13) & 0x3ff];
*out++ = 1.5 * g - 0.5 * g * g * g * f;
}
}
return (w + 4);
}
static void sigrsqrt_dsp(t_sigrsqrt *x, t_signal **sp)
{
dsp_add(sigrsqrt_perform, 3, sp[0]->s_vec, sp[1]->s_vec, sp[0]->s_n);
}
void rsqrt_tilde_setup(void)
{
init_rsqrt();
sigrsqrt_class = class_new(gensym("rsqrt~"), (t_newmethod)sigrsqrt_new, 0,
sizeof(t_sigrsqrt), 0, 0);
/* an old name for it: */
class_addcreator(sigrsqrt_new, gensym("q8_rsqrt~"), 0);
CLASS_MAINSIGNALIN(sigrsqrt_class, t_sigrsqrt, x_f);
class_addmethod(sigrsqrt_class, (t_method)sigrsqrt_dsp, gensym("dsp"), 0);
}
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