Finish adsr implementation

2 files changed, 151 insertions, 4 deletions

diff --git a/mmband/adsr.c b/mmband/adsr.c
index c50a5c1..b2a22e6 100644
--- a/mmband/adsr.c
+++ b/mmband/adsr.c
@@ -1,3 +1,146 @@
+#include <math.h>
+#include <stdbool.h>
+#include <stdlib.h>
+
 #include <mmband/api/adsr.h>
 
+#define SLOPE_CURVE(rate,target_curve) exp(-log((1.0 + target_curve) / target_curve) / rate)
+
+enum adsr_state {
+    ADSR_SLEEP,
+    ADSR_ATTACK,
+    ADSR_DECAY,
+    ADSR_SUSTAIN,
+    ADSR_RELEASE
+};
+
+struct adsr {
+    float attack;
+    float attack_base;
+    float attack_curve;
+
+    float decay;
+    float decay_base;
+    float decay_curve;
+
+    float sustain;
+
+    float release;
+    float release_base;
+    float release_curve;
+
+    float asc_target;
+    float desc_target;
+
+    float out;
+
+    bool gate;
+    enum adsr_state state;
+};
+
+adsr_ref adsr_new () {
+    adsr_ref adsr = malloc(sizeof(struct adsr));
+
+    adsr_set_attack(adsr, 0.0);
+    adsr_set_decay(adsr, 0.0);
+    adsr_set_sustain(adsr, 1.0);
+    adsr_set_release(adsr, 0.0);
+    adsr_set_asc_target(adsr, 0.2);
+    adsr_set_desc_target(adsr, 0.0001);
+
+    adsr->gate = false;
+    adsr->state = ADSR_SLEEP;
+    adsr->out = 0.0;
+
+    return adsr;  
+}
+
+void adsr_free (adsr_ref adsr) {
+    free(adsr);
+}
+
+void adsr_reset (adsr_ref adsr) {
+    adsr->gate = false;
+    adsr->state = ADSR_SLEEP;
+    adsr->out = 0.0;
+}
+
+void adsr_gate (adsr_ref adsr) {
+    if (!adsr->gate) {
+        adsr->state = ADSR_ATTACK;
+        adsr->gate = true;
+    } else if (adsr->state != ADSR_SLEEP) {
+        adsr->state = ADSR_RELEASE;
+        adsr->gate = false;
+    } 
+}
+
+float adsr_tick (adsr_ref adsr) {
+    switch (adsr->state) {
+        case ADSR_ATTACK:
+            adsr->out = adsr->attack_base + adsr->out * adsr->attack_curve;
+
+            if (adsr->out >= 1.0) {
+                adsr->out = 1.0;
+                adsr->state = ADSR_DECAY;
+            }
+
+            break;
+        case ADSR_DECAY:
+            adsr->out = adsr->decay_base + adsr->out * adsr->decay_curve;
+
+            if (adsr->out <= adsr->sustain) {
+                adsr->out = adsr->sustain;
+                adsr->state = ADSR_SUSTAIN;
+            }
+
+            break;
+        case ADSR_RELEASE:
+            adsr->out = adsr->release_base + adsr->out * adsr->release_curve;
+
+            if (adsr->out <= 0.0) {
+                adsr->out = 0.0;
+                adsr->state = ADSR_SLEEP;
+            }
+
+            break;
+        default:
+            break;
+    }
+
+    return adsr->out;
+}
+
+void adsr_set_attack (adsr_ref adsr, float attack_rate) {
+    adsr->attack = attack_rate;
+    adsr->attack_curve = SLOPE_CURVE(attack_rate, adsr->asc_target);
+    adsr->attack_base = (1.0 + adsr->asc_target) * (1.0 - adsr->attack_curve);
+}
+
+void adsr_set_decay (adsr_ref adsr, float decay_rate) {
+    adsr->decay = decay_rate;
+    adsr->decay_curve = SLOPE_CURVE(decay_rate, adsr->desc_target);
+    adsr->decay_base = (adsr->sustain - adsr->desc_target);
+}
+
+void adsr_set_sustain (adsr_ref adsr, float sustain_level) {
+    adsr->sustain = sustain_level;
+    adsr->decay_base = (adsr->sustain - adsr->desc_target) * (1.0 - adsr->decay_curve);
+}
+
+void adsr_set_release (adsr_ref adsr, float release_rate) {
+    adsr->release = release_rate;
+    adsr->release_curve = SLOPE_CURVE(release_rate, adsr->desc_target);
+    adsr->release_base = -adsr->desc_target * (1.0 - adsr->release_curve);
+}
+
+void adsr_set_asc_target (adsr_ref adsr, float target) {
+    adsr->asc_target = target;
+    adsr->attack_base = (1.0 + adsr->asc_target) * (1.0 - adsr->attack_curve);
+}
 
+void adsr_set_desc_target (adsr_ref adsr, float target) {
+    adsr->desc_target = target;
+    adsr->decay_base = (adsr->sustain - adsr->desc_target) * (1.0 - adsr->decay_curve);
+    adsr->release_base = -adsr->desc_target * (1.0 - adsr->release_curve);
+}
diff --git a/mmband/api/adsr.h b/mmband/api/adsr.h
index 899d1fe..d9a9e1b 100644
--- a/mmband/api/adsr.h
+++ b/mmband/api/adsr.h
@@ -3,15 +3,19 @@
 
 typedef struct adsr *adsr_ref;
 
-adsr_ref    adsr_new        (float sample_rate);
-void        adsr_free       (adsr_ref adsr);
+adsr_ref    adsr_new    ();
+void        adsr_free   (adsr_ref adsr);
+
+void        adsr_reset  (adsr_ref adsr);
+void        adsr_gate   (adsr_ref adsr);
+float       adsr_tick   (adsr_ref adsr);
 
 void        adsr_set_attack     (adsr_ref adsr, float attack_rate);
 void        adsr_set_decay      (adsr_ref adsr, float decay_rate);
 void        adsr_set_sustain    (adsr_ref adsr, float sustain_level);
 void        adsr_set_release    (adsr_ref adsr, float release_rate);
 
-void        adsr_set_asc_ratio  (adsr_ref adsr, float ratio);
-void        adsr_set_desc_ratio (adsr_ref adsr, float ratio);
+void        adsr_set_asc_target     (adsr_ref adsr, float target);
+void        adsr_set_desc_target    (adsr_ref adsr, float target);
 
 #endif