feat: add WAV load/save and ring buffer implementation

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

src/channel.c

@@ -28,6 +28,7 @@ void channel_add(jack_client_t *client, int idx) {
   channels[idx].loop_count = 0;
   channels[idx].record_pos = 0;
   channels[idx].playback_pos = 0;
+  channels[idx].save_ring = NULL;
 
   next_channel_id++;
   channel_count++;

src/channel.h

@@ -8,6 +8,8 @@
 #define LOOP_BUF_SIZE  (5 * 48000)
 #define MAX_CHANNELS   16
 
+#include "ringbuffer.h"
+
 typedef enum {
     STATE_IDLE,
     STATE_RECORD,
@@ -25,6 +27,8 @@ struct channel_t {
     atomic_int    active;
     jack_port_t  *audio_in;
     jack_port_t  *audio_out;
+
+    RingBuf      *save_ring;
 };
 
 /* Globals declared in looper.c */
@@ -33,6 +37,8 @@ extern atomic_int  channel_count;
 extern int         next_channel_id;
 extern atomic_int  cmd_add;
 extern atomic_int  cmd_remove;
+extern atomic_int  cmd_load;
+extern atomic_int  cmd_save;
 
 void channel_add(jack_client_t *client, int idx);
 void channel_remove(jack_client_t *client, int idx);

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);
+        }
+      }
+    }
+  }
 }

src/midi.c

@@ -8,6 +8,8 @@
 extern atomic_int control_key_active;
 extern atomic_int cmd_add;
 extern atomic_int cmd_remove;
+extern atomic_int cmd_load;
+extern atomic_int cmd_save;
 extern atomic_int bind_channel;
 
 void midi_handle_events(void *port_buffer, jack_nframes_t nframes) {
@@ -67,6 +69,12 @@ void midi_handle_events(void *port_buffer, jack_nframes_t nframes) {
             case 63: /* unbind – reset bind to channel 0 */
               atomic_store(&bind_channel, 0);
               break;
+            case 70: /* load WAV into channel 0 */
+              atomic_store(&cmd_load, 1);
+              break;
+            case 71: /* save WAV of channel 0 */
+              atomic_store(&cmd_save, 1);
+              break;
             default:
               break;
             }

src/ringbuffer.c

@@ -0,0 +1,69 @@
+#include "ringbuffer.h"
+#include <stdlib.h>
+
+static inline size_t load_head(const RingBuf *r) {
+    return atomic_load_explicit(&r->head, memory_order_relaxed);
+}
+static inline size_t load_tail(const RingBuf *r) {
+    return atomic_load_explicit(&r->tail, memory_order_relaxed);
+}
+static inline void store_head(RingBuf *r, size_t v) {
+    atomic_store_explicit(&r->head, v, memory_order_relaxed);
+}
+static inline void store_tail(RingBuf *r, size_t v) {
+    atomic_store_explicit(&r->tail, v, memory_order_relaxed);
+}
+
+int ring_init(RingBuf *r, size_t capacity) {
+    r->buf = (float*)malloc(capacity * sizeof(float));
+    if (!r->buf) return -1;
+    r->capacity = capacity;
+    store_head(r, 0);
+    store_tail(r, 0);
+    return 0;
+}
+
+void ring_destroy(RingBuf *r) {
+    free(r->buf);
+    r->buf = NULL;
+    r->capacity = 0;
+}
+
+size_t ring_readable(const RingBuf *r) {
+    size_t h = load_head(r);
+    size_t t = load_tail(r);
+    if (h >= t) return h - t;
+    else        return r->capacity - (t - h);
+}
+
+size_t ring_writeable(const RingBuf *r) {
+    return r->capacity - 1 - ring_readable(r);
+}
+
+size_t ring_write(RingBuf *r, const float *data, size_t count) {
+    size_t avail = ring_writeable(r);
+    if (count > avail) count = avail;
+    if (count == 0) return 0;
+    size_t head = load_head(r);
+    size_t cap = r->capacity;
+    for (size_t i = 0; i < count; ++i) {
+        r->buf[head] = data[i];
+        head = (head + 1) % cap;
+    }
+    store_head(r, head);
+    return count;
+}
+
+size_t ring_read(RingBuf *r, float *data, size_t count) {
+    size_t avail = ring_readable(r);
+    if (count > avail) count = avail;
+    if (count == 0) return 0;
+    size_t tail = load_tail(r);
+    size_t cap = r->capacity;
+    for (size_t i = 0; i < count; ++i) {
+        data[i] = r->buf[tail];
+        tail = (tail + 1) % cap;
+    }
+    store_tail(r, tail);
+    return count;
+}

src/ringbuffer.h

@@ -0,0 +1,21 @@
+#ifndef RINGBUFFER_H
+#define RINGBUFFER_H
+
+#include <stddef.h>
+#include <stdatomic.h>
+
+typedef struct {
+    atomic_size_t head;
+    atomic_size_t tail;
+    size_t        capacity;
+    float        *buf;
+} RingBuf;
+
+int  ring_init(RingBuf *r, size_t capacity);
+void ring_destroy(RingBuf *r);
+size_t ring_readable(const RingBuf *r);
+size_t ring_writeable(const RingBuf *r);
+size_t ring_write(RingBuf *r, const float *data, size_t count);
+size_t ring_read(RingBuf *r, float *data, size_t count);
+
+#endif

src/wav.c

@@ -0,0 +1,113 @@
+#include "wav.h"
+#include "channel.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+static inline int read_uint16(int fd, uint16_t *v) {
+    return read(fd, v, sizeof(uint16_t)) == sizeof(uint16_t) ? 0 : -1;
+}
+static inline int read_uint32(int fd, uint32_t *v) {
+    return read(fd, v, sizeof(uint32_t)) == sizeof(uint32_t) ? 0 : -1;
+}
+
+int wav_read(const char *path, float **buffer, unsigned *frames) {
+    int fd = open(path, O_RDONLY);
+    if (fd < 0) return -1;
+    posix_fadvise(fd, 0, 0, POSIX_FADV_SEQUENTIAL);
+    char riff[4];
+    if (read(fd, riff, 4) != 4 || memcmp(riff, "RIFF", 4) != 0) { close(fd); return -1; }
+    uint32_t chunk_size;
+    if (read_uint32(fd, &chunk_size) != 0) { close(fd); return -1; }
+    char wave[4];
+    if (read(fd, wave, 4) != 4 || memcmp(wave, "WAVE", 4) != 0) { close(fd); return -1; }
+    uint32_t fmt_size = 0;
+    uint16_t audio_format = 0;
+    uint16_t num_channels = 0;
+    uint32_t sample_rate = 0;
+    uint16_t bits_per_sample = 0;
+    while (1) {
+        char sub_id[4];
+        if (read(fd, sub_id, 4) != 4) { close(fd); return -1; }
+        if (read_uint32(fd, &fmt_size) != 0) { close(fd); return -1; }
+        if (memcmp(sub_id, "fmt ", 4) == 0) {
+            if (read_uint16(fd, &audio_format) != 0) { close(fd); return -1; }
+            if (read_uint16(fd, &num_channels) != 0)  { close(fd); return -1; }
+            if (read_uint32(fd, &sample_rate) != 0)   { close(fd); return -1; }
+            if (read_uint16(fd, &bits_per_sample) != 0){ close(fd); return -1; }
+            if (fmt_size > 16) lseek(fd, fmt_size - 16, SEEK_CUR);
+            continue;
+        }
+        if (memcmp(sub_id, "data", 4) == 0) break;
+        lseek(fd, fmt_size, SEEK_CUR);
+    }
+    if (audio_format != 1 || num_channels != 1 || bits_per_sample != 16) {
+        close(fd); return -1;
+    }
+    unsigned max_frames = LOOP_BUF_SIZE;
+    unsigned total_frames = 0;
+    float *buf = (float*)malloc(max_frames * sizeof(float));
+    if (!buf) { close(fd); return -1; }
+    while (total_frames < max_frames) {
+        int16_t sample;
+        ssize_t n = read(fd, &sample, 2);
+        if (n < 2) break;
+        buf[total_frames++] = sample / 32768.0f;
+    }
+    close(fd);
+    *buffer = buf;
+    *frames = total_frames;
+    return 0;
+}
+
+int wav_write(const char *path, const float *data, unsigned frames, unsigned sample_rate) {
+    int fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
+    if (fd < 0) return -1;
+    posix_fadvise(fd, 0, 0, POSIX_FADV_SEQUENTIAL);
+    unsigned data_bytes = frames * 2;
+    unsigned file_size = 44 + data_bytes;
+    unsigned char header[44];
+    memset(header, 0, 44);
+    memcpy(header, "RIFF", 4);
+    header[4] = (unsigned char)( file_size      & 0xff);
+    header[5] = (unsigned char)((file_size>>8)  & 0xff);
+    header[6] = (unsigned char)((file_size>>16) & 0xff);
+    header[7] = (unsigned char)((file_size>>24) & 0xff);
+    memcpy(header+8, "WAVE", 4);
+    memcpy(header+12, "fmt ", 4);
+    header[16]=16; header[17]=0; header[18]=0; header[19]=0;
+    header[20]=1; header[21]=0;
+    header[22]=1; header[23]=0;
+    unsigned sr = sample_rate;
+    header[24] = (unsigned char)( sr & 0xff);
+    header[25] = (unsigned char)((sr>>8) & 0xff);
+    header[26] = (unsigned char)((sr>>16)& 0xff);
+    header[27] = (unsigned char)((sr>>24)& 0xff);
+    unsigned br = sr * 2;
+    header[28] = (unsigned char)( br & 0xff);
+    header[29] = (unsigned char)((br>>8) & 0xff);
+    header[30] = (unsigned char)((br>>16)& 0xff);
+    header[31] = (unsigned char)((br>>24)& 0xff);
+    header[32]=2; header[33]=0;
+    header[34]=16; header[35]=0;
+    memcpy(header+36, "data", 4);
+    header[40] = (unsigned char)( data_bytes & 0xff);
+    header[41] = (unsigned char)((data_bytes>>8) & 0xff);
+    header[42] = (unsigned char)((data_bytes>>16)& 0xff);
+    header[43] = (unsigned char)((data_bytes>>24)& 0xff);
+    ssize_t written = write(fd, header, 44);
+    if (written != 44) { close(fd); return -1; }
+    for (unsigned i = 0; i < frames; ++i) {
+        float s = data[i];
+        if (s < -1.0f) s = -1.0f;
+        if (s >  1.0f) s =  1.0f;
+        int16_t sample = (int16_t)(s * 32767);
+        written = write(fd, &sample, 2);
+        if (written != 2) { close(fd); return -1; }
+    }
+    close(fd);
+    return 0;
+}

src/wav.h

@@ -0,0 +1,9 @@
+#ifndef WAV_H
+#define WAV_H
+
+#include <stddef.h>
+
+int wav_read(const char *path, float **buffer, unsigned *frames);
+int wav_write(const char *path, const float *data, unsigned frames, unsigned sample_rate);
+
+#endif