1 files changed, 50 insertions, 0 deletions
diff --git a/src/audio/ring_buffer.h b/src/audio/ring_buffer.h
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--- /dev/null
+++ b/src/audio/ring_buffer.h
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+// This file is part of the 64k demo project.
+// It implements a lock-free ring buffer for audio streaming.
+// Bridges main thread (variable tempo) and audio thread (fixed rate).
+
+#pragma once
+
+#include <atomic>
+#include <cstdint>
+
+// Ring buffer capacity: 200ms @ 32kHz stereo
+// = 200ms * 32000 samples/sec * 2 channels / 1000ms = 12800 samples
+// This is exactly 25 DCT frames (25 * 512 = 12800)
+#define RING_BUFFER_LOOKAHEAD_MS 200
+#define RING_BUFFER_SAMPLE_RATE 32000
+#define RING_BUFFER_CHANNELS 2
+#define RING_BUFFER_CAPACITY_SAMPLES \
+  ((RING_BUFFER_LOOKAHEAD_MS * RING_BUFFER_SAMPLE_RATE * RING_BUFFER_CHANNELS) / 1000)
+
+class AudioRingBuffer {
+ public:
+  AudioRingBuffer();
+  ~AudioRingBuffer();
+
+  // Thread-safe write (main thread)
+  // Returns number of samples actually written
+  int write(const float* samples, int count);
+
+  // Thread-safe read (audio thread)
+  // Returns number of samples actually read
+  // If not enough samples available, fills remainder with silence
+  int read(float* samples, int count);
+
+  // Query buffer state
+  int available_write() const;  // Samples that can be written
+  int available_read() const;   // Samples that can be read
+
+  // Get total samples consumed (for timing)
+  int64_t get_total_read() const { return total_read_.load(std::memory_order_acquire); }
+
+  // Clear buffer (for seeking)
+  void clear();
+
+ private:
+  float buffer_[RING_BUFFER_CAPACITY_SAMPLES];
+  int capacity_;  // Total capacity in samples
+
+  std::atomic<int> write_pos_;  // Write position (0 to capacity-1)
+  std::atomic<int> read_pos_;   // Read position (0 to capacity-1)
+  std::atomic<int64_t> total_read_;  // Total samples read (for playback time)
+};