/* This code is placed in the public domain. */ #include <stdlib.h>#include <math.h>#include "soundpipe.h" enum { CLEAR, ATTACK, DECAY, SUSTAIN, RELEASE }; int sp_adsr_create(sp_adsr **p){    *p = malloc(sizeof(sp_adsr));    return SP_OK;} int sp_adsr_destroy(sp_adsr **p){    free(*p);    return SP_OK;} int sp_adsr_init(sp_data *sp, sp_adsr *p){    p->atk = 0.1;    p->dec = 0.1;    p->sus = 0.5;    p->rel = 0.3;    p->timer = 0;    p->a = 0;    p->b = 0;    p->y = 0;    p->x = 0;    p->prev = 0;    p->atk_time = p->atk * sp->sr;    p->mode = CLEAR;    return SP_OK;} static SPFLOAT tau2pole(sp_data *sp, sp_adsr *p, SPFLOAT tau){    USED(p);     return exp(-1.0 / (tau * sp->sr));} static SPFLOAT adsr_filter(sp_data *sp, sp_adsr *p){    USED(sp);     p->y = p->b * p->x  + p->a * p->y;    return p->y;} int sp_adsr_compute(sp_data *sp, sp_adsr *p, SPFLOAT *in, SPFLOAT *out){    SPFLOAT pole;    if (p->prev < *in && p->mode != DECAY) {        p->mode = ATTACK;        p->timer = 0;        /* quick fix: uncomment if broken */        /* pole = tau2pole(sp, p, p->atk * 0.75); */        /* p->atk_time = p->atk * sp->sr * 1.5; */        pole = tau2pole(sp, p, p->atk * 0.6);        p->atk_time = p->atk * sp->sr;        p->a = pole;        p->b = 1 - pole;    } else if (p->prev > *in) {        p->mode = RELEASE;        pole = tau2pole(sp, p, p->rel);        p->a = pole;        p->b = 1 - pole;    }     p->x = *in;    p->prev = *in;     switch (p->mode) {        case CLEAR:            *out = 0;            break;        case ATTACK:            p->timer++;            *out = adsr_filter(sp, p);            /* quick fix: uncomment if broken */            /* if(p->timer > p->atk_time) { */            if (*out > 0.99) {                p->mode = DECAY;                pole = tau2pole(sp, p, p->dec);                p->a = pole;                p->b = 1 - pole;            }            break;        case DECAY:        case RELEASE:            p->x *= p->sus;            *out = adsr_filter(sp, p);        default:            break;    }     return SP_OK;}