feat: add WAV load/save and ring buffer implementation

Co-authored-by: aider (deepseek/deepseek-reasoner) <aider@aider.chat>

src/looper.c

@@ -2,6 +2,7 @@
 #include "looper.h"
 #include "channel.h"
 #include "midi.h"
+#include "wav.h"
 #include <jack/jack.h>
 #include <jack/midiport.h>
 #include <math.h>
@@ -9,6 +10,8 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <pthread.h>
+#include <time.h>
 
 /* Global state (shared across files) */
 struct channel_t channels[MAX_CHANNELS];
@@ -16,6 +19,8 @@ atomic_int channel_count = 0;
 int next_channel_id = 1;
 atomic_int cmd_add = 0;
 atomic_int cmd_remove = 0;
+atomic_int cmd_load = 0;
+atomic_int cmd_save = 0;
 jack_port_t *midi_control_port = NULL;
 jack_port_t *midi_clock_port = NULL;
 atomic_int control_key_active = 0;
@@ -24,6 +29,10 @@ atomic_int bind_channel = 0;
 /* Deferred removal index (1 second grace) */
 static int pending_unregister_idx = -1;
 
+/* writer thread function and sample rate holder */
+static void *writer_thread(void *arg);
+static int global_sample_rate = 0;
+
 /* ----------------------------------------------------------------
  * process callback
  * ---------------------------------------------------------------- */
@@ -172,6 +181,9 @@ void jack_shutdown_cb(void *arg) {
  * looper initialisation
  * ---------------------------------------------------------------- */
 int looper_init(jack_client_t *client) {
+  /* store sample rate for writer thread */
+  global_sample_rate = jack_get_sample_rate(client);
+
   /* channel 0 */
   channels[0].active = 1;
   atomic_store(&channels[0].state, STATE_IDLE);
@@ -179,6 +191,7 @@ int looper_init(jack_client_t *client) {
   channels[0].loop_count = 0;
   channels[0].record_pos = 0;
   channels[0].playback_pos = 0;
+  channels[0].save_ring = NULL;
 
   channels[0].audio_in = jack_port_register(
       client, "input", JACK_DEFAULT_AUDIO_TYPE, JackPortIsInput, 0);
@@ -202,6 +215,44 @@ int looper_init(jack_client_t *client) {
   return 0;
 }
 
+/* ----------------------------------------------------------------
+ * writer thread – consumes the save ring and writes WAV file
+ * ---------------------------------------------------------------- */
+static void *writer_thread(void *arg) {
+    struct channel_t *ch = (struct channel_t *)arg;
+    RingBuf *ring = ch->save_ring;
+    if (!ring) return NULL;
+
+    static const char *path = "save.wav";
+    unsigned sr = (unsigned)global_sample_rate;
+    if (sr == 0) sr = 48000;
+
+    float *outbuf = malloc((size_t)ch->loop_count * sizeof(float));
+    if (!outbuf) {
+        ring_destroy(ring);
+        free(ring);
+        ch->save_ring = NULL;
+        return NULL;
+    }
+    size_t collected = 0;
+    size_t want = (size_t)ch->loop_count;
+    while (collected < want) {
+        size_t got = ring_read(ring, outbuf + collected, want - collected);
+        collected += got;
+        if (got == 0) {
+            struct timespec req = { .tv_sec = 0, .tv_nsec = 10000000 };
+            nanosleep(&req, NULL);
+        }
+    }
+    wav_write(path, outbuf, ch->loop_count, sr);
+    free(outbuf);
+
+    ring_destroy(ring);
+    free(ring);
+    ch->save_ring = NULL;
+    return NULL;
+}
+
 /* ----------------------------------------------------------------
  * main‑loop command processing
  * ---------------------------------------------------------------- */
@@ -239,4 +290,42 @@ void looper_process_commands(jack_client_t *client) {
       pending_unregister_idx = remove_idx;
     }
   }
+
+  /* ---------- load command ---------- */
+  if (atomic_exchange(&cmd_load, 0)) {
+    float *buf = NULL;
+    unsigned frames = 0;
+    if (wav_read("loop.wav", &buf, &frames) == 0 && frames > 0) {
+      if (frames > LOOP_BUF_SIZE) frames = LOOP_BUF_SIZE;
+      memcpy(channels[0].loop_buffer, buf, frames * sizeof(float));
+      channels[0].loop_count  = (int)frames;
+      channels[0].record_pos  = 0;
+      channels[0].playback_pos = 0;
+      atomic_store(&channels[0].state, STATE_LOOPING);
+      channels[0].prev_state = -1;
+      free(buf);
+    } else {
+      fprintf(stderr, "Failed to load loop.wav\n");
+    }
+  }
+
+  /* ---------- save command (writer thread) ---------- */
+  if (atomic_exchange(&cmd_save, 0)) {
+    if (atomic_load(&channels[0].state) == STATE_LOOPING &&
+        channels[0].loop_count > 0 &&
+        channels[0].save_ring == NULL) {
+      RingBuf *ring = (RingBuf*)malloc(sizeof(RingBuf));
+      if (ring) {
+        size_t sz = (size_t)channels[0].loop_count * 2;
+        if (ring_init(ring, sz) == 0) {
+          channels[0].save_ring = ring;
+          pthread_t th;
+          pthread_create(&th, NULL, writer_thread, &channels[0]);
+          pthread_detach(th);
+        } else {
+          free(ring);
+        }
+      }
+    }
+  }
 }