From f84474d94d3618b9dc2581b72aea768052a40dd7 Mon Sep 17 00:00:00 2001
From: jacqueline <me@jacqueline.id.au>
Date: Fri, 31 May 2024 11:52:19 +1000
Subject: Introduce a PcmBuffer abstraction for handling source draining

---
 src/drivers/include/drivers/bluetooth.hpp  | 10 ++---
 src/drivers/include/drivers/i2s_dac.hpp    | 11 +++--
 src/drivers/include/drivers/pcm_buffer.hpp | 72 ++++++++++++++++++++++++++++++
 3 files changed, 82 insertions(+), 11 deletions(-)
 create mode 100644 src/drivers/include/drivers/pcm_buffer.hpp

(limited to 'src/drivers/include')

diff --git a/src/drivers/include/drivers/bluetooth.hpp b/src/drivers/include/drivers/bluetooth.hpp
index ad61fcc1..030907d9 100644
--- a/src/drivers/include/drivers/bluetooth.hpp
+++ b/src/drivers/include/drivers/bluetooth.hpp
@@ -14,6 +14,7 @@
 #include <stdint.h>
 #include "drivers/bluetooth_types.hpp"
 #include "drivers/nvs.hpp"
+#include "drivers/pcm_buffer.hpp"
 #include "esp_a2dp_api.h"
 #include "esp_avrc_api.h"
 #include "esp_gap_bt_api.h"
@@ -42,9 +43,8 @@ class Bluetooth {
   auto SetPreferredDevice(std::optional<bluetooth::MacAndName> dev) -> void;
   auto PreferredDevice() -> std::optional<bluetooth::MacAndName>;
 
-  auto SetSource(StreamBufferHandle_t) -> void;
+  auto SetSource(PcmBuffer*) -> void;
   auto SetVolumeFactor(float) -> void;
-  auto SamplesUsed() -> uint32_t;
 
   auto SetEventHandler(std::function<void(bluetooth::Event)> cb) -> void;
 };
@@ -114,8 +114,8 @@ class BluetoothState : public tinyfsm::Fsm<BluetoothState> {
   static auto discovery() -> bool;
   static auto discovery(bool) -> void;
 
-  static auto source() -> StreamBufferHandle_t;
-  static auto source(StreamBufferHandle_t) -> void;
+  static auto source() -> PcmBuffer*;
+  static auto source(PcmBuffer*) -> void;
 
   static auto event_handler(std::function<void(Event)>) -> void;
 
@@ -147,7 +147,7 @@ class BluetoothState : public tinyfsm::Fsm<BluetoothState> {
   static std::optional<bluetooth::MacAndName> sConnectingDevice_;
   static int sConnectAttemptsRemaining_;
 
-  static std::atomic<StreamBufferHandle_t> sSource_;
+  static std::atomic<PcmBuffer*> sSource_;
   static std::function<void(Event)> sEventHandler_;
 
   auto connect(const bluetooth::MacAndName&) -> bool;
diff --git a/src/drivers/include/drivers/i2s_dac.hpp b/src/drivers/include/drivers/i2s_dac.hpp
index 0776dbab..138a0c03 100644
--- a/src/drivers/include/drivers/i2s_dac.hpp
+++ b/src/drivers/include/drivers/i2s_dac.hpp
@@ -16,6 +16,7 @@
 
 #include "driver/i2s_std.h"
 #include "driver/i2s_types.h"
+#include "drivers/pcm_buffer.hpp"
 #include "esp_err.h"
 #include "freertos/FreeRTOS.h"
 #include "freertos/portmacro.h"
@@ -39,9 +40,9 @@ constexpr size_t kI2SBufferLengthFrames = 1024;
  */
 class I2SDac {
  public:
-  static auto create(IGpios& expander) -> std::optional<I2SDac*>;
+  static auto create(IGpios& expander, PcmBuffer&) -> std::optional<I2SDac*>;
 
-  I2SDac(IGpios& gpio, i2s_chan_handle_t i2s_handle);
+  I2SDac(IGpios& gpio, PcmBuffer&, i2s_chan_handle_t i2s_handle);
   ~I2SDac();
 
   auto Start() -> void;
@@ -69,9 +70,6 @@ class I2SDac {
   auto Reconfigure(Channels ch, BitsPerSample bps, SampleRate rate) -> void;
 
   auto WriteData(const std::span<const std::byte>& data) -> void;
-  auto SetSource(StreamBufferHandle_t buffer) -> void;
-
-  auto SamplesUsed() -> uint32_t;
 
   // Not copyable or movable.
   I2SDac(const I2SDac&) = delete;
@@ -81,9 +79,10 @@ class I2SDac {
   auto set_channel(bool) -> void;
 
   IGpios& gpio_;
+  PcmBuffer& buffer_;
   i2s_chan_handle_t i2s_handle_;
+
   bool i2s_active_;
-  StreamBufferHandle_t buffer_;
   std::mutex configure_mutex_;
 
   i2s_std_clk_config_t clock_config_;
diff --git a/src/drivers/include/drivers/pcm_buffer.hpp b/src/drivers/include/drivers/pcm_buffer.hpp
new file mode 100644
index 00000000..6630f720
--- /dev/null
+++ b/src/drivers/include/drivers/pcm_buffer.hpp
@@ -0,0 +1,72 @@
+/*
+ * Copyright 2024 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#pragma once
+
+#include <stdint.h>
+#include <atomic>
+#include <cstddef>
+#include <span>
+
+#include "freertos/FreeRTOS.h"
+
+#include "freertos/ringbuf.h"
+#include "portmacro.h"
+
+namespace drivers {
+
+/*
+ * A circular buffer of signed, 16-bit PCM samples. PcmBuffers are the main
+ * data structure used for shuffling large amounts of read-to-play samples
+ * throughout the system.
+ */
+class PcmBuffer {
+ public:
+  PcmBuffer(size_t size_in_samples);
+  ~PcmBuffer();
+
+  /* Adds samples to the buffer. */
+  auto send(std::span<const int16_t>) -> void;
+
+  /*
+   * Fills the given span with samples. If enough samples are available in
+   * the buffer, then the span will be filled with samples from the buffer. Any
+   * shortfall is made up by padding the given span with zeroes.
+   */
+  auto receive(std::span<int16_t>, bool isr) -> BaseType_t;
+
+  auto clear() -> void;
+  auto isEmpty() -> bool;
+
+  /*
+   * How many samples have been added to this buffer since it was created. This
+   * method overflows by wrapping around to zero.
+   */
+  auto totalSent() -> uint32_t;
+
+  /*
+   * How many samples have been removed from this buffer since it was created.
+   * This method overflows by wrapping around to zero.
+   */
+  auto totalReceived() -> uint32_t;
+
+  // Not copyable or movable.
+  PcmBuffer(const PcmBuffer&) = delete;
+  PcmBuffer& operator=(const PcmBuffer&) = delete;
+
+ private:
+  auto readSingle(std::span<int16_t>, bool isr)
+      -> std::pair<size_t, BaseType_t>;
+
+  StaticRingbuffer_t meta_;
+  uint8_t* buf_;
+
+  std::atomic<uint32_t> sent_;
+  std::atomic<uint32_t> received_;
+  RingbufHandle_t ringbuf_;
+};
+
+}  // namespace drivers
-- 
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