synththing/src/utils/envelope.c

/*
 * Filename:    envelope.c
 *
 * Description:
 *
 *
 * Version:     
 * Created:     Wed Oct 30 17:15:02 2019
 * Revision:    None
 * Author:      Rachel Fae Fox (foxiepaws),fox@foxiepa.ws
 *
 */
#include "../common.h"
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>


typedef enum EnvState {_e_off,_e_attack, _e_attackrelease, _e_decay, _e_sustain,_e_release, _e_finished} EnvState;
typedef struct Envelope {
    // these values are in samples.
    unsigned int attack;
    unsigned int decay;
    unsigned int release;
    float sustain_level;
    float max_level;
    float min_level;
    float level;
    bool gate;
    unsigned long int t;
    EnvState envstate;
    bool ar;
    bool sustain;
    float(*process)(struct Envelope *,EngineState *);
    
} Envelope;
/*

    if (self->ar) {
	float diff = (self->max_level - self->min_level) / (float) self->attack;
	if (self->t <= self->attack && self->gate) {
	    self->level = self->state * diff;
	    self->state++;
	} else if (self->sustain && self->gate) {
	    self->level = self->max_level;
	} else if (self->state < self->attack && self->state > 0){
	    self->level = self->level - diff;
	    self->state--;
	} else if ((self->state - self->attack) <= self->release) {
	    self->level = self->max_level - ((self->state - self->attack) * diff);
	    self->state++;
	}
	}

    return self->level;
    return self->gate ? self->max_level : self-> min_level;

*/

float envelope_process(Envelope *self, EngineState *t) {
    switch (self->envstate) {
    case _e_off:
	//printf("_off\n");
	if (self->gate) {
	    self->t = 0;
	    self->envstate = _e_attack;
	    return envelope_process(self, t);
	}
	break;
    case _e_attack:
	//printf("_attack: %i\n", self->t);
	if (self->gate) {
	    if ( self->t < self->attack ) {
		float stepsize = (self->max_level - self->min_level) / self->attack;
		self->t++;
		return self->t * stepsize;
	    } else {
		if (self->ar) {
		    self->t = 0;
		    self->envstate = _e_sustain;
		    return self->max_level;
		} else {
		    self->t = 0;
		    self->envstate = _e_decay;
		    return self->max_level; 
		}
	    }
	} else {
	    self->envstate = _e_attackrelease;
	    return envelope_process(self, t);
	}
	break;
    case _e_decay:
	//	printf("_decay: %i\n", self->t);
	if (self->gate) {
	    if (self->t < self->decay) {
		float stepsize = (self->max_level - self->sustain_level) / self->decay;
		self->t++;
		return (self->max_level - (self->t * stepsize));
		
	    } else {
		self->envstate = _e_sustain;
		return self->sustain_level;
	    }
	} else {
	    self->envstate = _e_attackrelease;
	    return envelope_process(self, t);
	}
	break;
    case _e_sustain:
	//printf("_sustain\n", self->t);
	if (!self->sustain) {
	    self->envstate = _e_release;
	    self->t = 0;
	    return envelope_process(self, t);
	}
	if (!self->gate) {
	    self->t = 0;
	    self->envstate = _e_release;
	    if (self->ar)
		return self->max_level;
	    return self->sustain_level;
	}
	if (self->ar)
	    return self->max_level;
	return self->sustain_level;
	break;
    case _e_release:
	//	printf("_release: %i\n", self->t);
	if (self->gate && self->sustain) {
	    // reset envelope.
	    self->envstate=_e_off;
	    return envelope_process(self,t);
	}
	if (self->t < self->release) {
	    float stepsize = ((self->ar ? self->max_level : self->sustain_level) - self->min_level) / self->release;
	    self->t++;
	    return (self->ar ? self->max_level : self->sustain_level) - (stepsize * self->t);
	} else {
	    self->envstate = _e_off;
	    return self->min_level;
	}
	
	break;
    case _e_attackrelease:
	if (self->gate) {
	    //reset envelope
	    self->envstate=_e_off;
	    return envelope_process(self,t);
	}
	return 0.0f;
	break;
	
    }
    return 0.0f; // if this is reached, something went wrong or an unhandled function was used.
}
Envelope* envelope_new() {
    Envelope *e = malloc(sizeof(Envelope));
    e->process = envelope_process;
    e->envstate = _e_off;
    e->t = 0;
    e->max_level = 1.0f;
    e->sustain_level = 1.0f;
    e->min_level = 0.0f;
    return e;
}