feat: add WAV load/save and ring buffer implementation

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

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;
+}