/* This code is placed in the public domain. */ #include <math.h>#include <stdlib.h>#include "soundpipe.h" int sp_expon_create(sp_expon **p){    *p = malloc(sizeof(sp_expon));    return SP_OK;} int sp_expon_destroy(sp_expon **p){    free(*p);    return SP_OK;} static void expon_reinit(sp_data *sp, sp_expon *p){    SPFLOAT onedsr;    p->stime = 0;    p->sdur = p->dur * sp->sr;    onedsr = 1.0 / sp->sr;     if ((p->a * p->b) > 0.0) {        p->incr = pow((SPFLOAT)(p->b / p->a), onedsr / p->dur);    } else {        p->incr = 1;        p->val = p->a;    }     p->val = p->a;} int sp_expon_init(sp_data *sp, sp_expon *p){    p->a = 0.000001;    p->b = 1;    p->dur = 1;    expon_reinit(sp, p);    p->init = 1;    return SP_OK;} int sp_expon_compute(sp_data *sp, sp_expon *p, SPFLOAT *in, SPFLOAT *out){    if (*in) {        expon_reinit(sp, p);        p->init = 0;    }     if (p->init) {        *out = 0;        return SP_OK;    }     if (p->stime < p->sdur) {        SPFLOAT val = p->val;        p->val *= p->incr;        p->stime++;        *out = val;    } else {        *out = p->b;    }     return SP_OK;}