From a2c1dfbabddc2b4abaf8bf27c9ed9d1b99594859 Mon Sep 17 00:00:00 2001
From: jacqueline <me@jacqueline.id.au>
Date: Thu, 15 Jun 2023 10:33:46 +1000
Subject: Add vorbis and flac decoders, flesh out codec interface

vorbis doesn't quite work yet, not sure why. will pick it up again
later.
---
 src/codecs/stbvorbis.cpp | 128 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)
 create mode 100644 src/codecs/stbvorbis.cpp

(limited to 'src/codecs/stbvorbis.cpp')

diff --git a/src/codecs/stbvorbis.cpp b/src/codecs/stbvorbis.cpp
new file mode 100644
index 00000000..de315416
--- /dev/null
+++ b/src/codecs/stbvorbis.cpp
@@ -0,0 +1,128 @@
+/*
+ * Copyright 2023 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include "stbvorbis.hpp"
+#include <stdint.h>
+
+#include <cstdint>
+#include <optional>
+
+#include "stb_vorbis.h"
+
+namespace codecs {
+
+StbVorbisDecoder::StbVorbisDecoder()
+    : vorbis_(nullptr),
+      current_sample_(-1),
+      num_channels_(0),
+      num_samples_(0),
+      samples_array_(NULL) {}
+
+StbVorbisDecoder::~StbVorbisDecoder() {
+  if (vorbis_ != nullptr) {
+    stb_vorbis_close(vorbis_);
+  }
+}
+
+static uint32_t scaleToBits(float sample, uint8_t bits) {
+  // Scale to range.
+  int32_t max_val = (1 << (bits - 1));
+  int32_t fixed_point = sample * max_val;
+
+  // Clamp within bounds.
+  fixed_point = std::clamp(fixed_point, -max_val, max_val);
+
+  // Remove sign.
+  return *reinterpret_cast<uint32_t*>(&fixed_point);
+}
+
+auto StbVorbisDecoder::BeginStream(const cpp::span<const std::byte> input)
+    -> Result<OutputFormat> {
+  if (vorbis_ != nullptr) {
+    stb_vorbis_close(vorbis_);
+    vorbis_ = nullptr;
+  }
+  current_sample_ = -1;
+  int bytes_read = 0;
+  int error = 0;
+  vorbis_ =
+      stb_vorbis_open_pushdata(reinterpret_cast<const uint8_t*>(input.data()),
+                               input.size_bytes(), &bytes_read, &error, NULL);
+  if (error != 0) {
+    return {0, cpp::fail(Error::kMalformedData)};
+  }
+  stb_vorbis_info info = stb_vorbis_get_info(vorbis_);
+  return {bytes_read,
+          OutputFormat{.num_channels = static_cast<uint8_t>(info.channels),
+                       .bits_per_sample = 24,
+                       .sample_rate_hz = info.sample_rate}};
+}
+
+auto StbVorbisDecoder::ContinueStream(cpp::span<const std::byte> input,
+                                      cpp::span<std::byte> output)
+    -> Result<OutputInfo> {
+  std::size_t bytes_used = 0;
+  if (current_sample_ < 0) {
+    num_channels_ = 0;
+    num_samples_ = 0;
+    samples_array_ = NULL;
+
+    while (true) {
+      auto cropped = input.subspan(bytes_used);
+      std::size_t b = stb_vorbis_decode_frame_pushdata(
+          vorbis_, reinterpret_cast<const uint8_t*>(cropped.data()),
+          cropped.size_bytes(), &num_channels_, &samples_array_, &num_samples_);
+      if (b == 0) {
+        return {bytes_used, cpp::fail(Error::kOutOfInput)};
+      }
+      bytes_used += b;
+
+      if (num_samples_ == 0) {
+        // Decoder is synchronising. Decode more bytes.
+        continue;
+      }
+      if (num_channels_ == 0 || samples_array_ == NULL) {
+        // The decoder isn't satisfying its contract.
+        return {bytes_used, cpp::fail(Error::kInternalError)};
+      }
+      current_sample_ = 0;
+      break;
+    }
+  }
+
+  // We successfully decoded a frame. Time to write out the samples.
+  std::size_t output_byte = 0;
+  while (current_sample_ < num_samples_) {
+    if (output_byte + (2 * num_channels_) >= output.size()) {
+      return {0, OutputInfo{.bytes_written = output_byte,
+                            .is_finished_writing = false}};
+    }
+
+    for (int channel = 0; channel < num_channels_; channel++) {
+      float raw_sample = samples_array_[channel][current_sample_];
+
+      uint16_t sample_24 = scaleToBits(raw_sample, 24);
+      output[output_byte++] = static_cast<std::byte>((sample_24 >> 16) & 0xFF);
+      output[output_byte++] = static_cast<std::byte>((sample_24 >> 8) & 0xFF);
+      output[output_byte++] = static_cast<std::byte>((sample_24)&0xFF);
+      // Pad to 32 bits for alignment.
+      output[output_byte++] = static_cast<std::byte>(0);
+    }
+    current_sample_++;
+  }
+
+  current_sample_ = -1;
+  return {bytes_used, OutputInfo{.bytes_written = output_byte,
+                                 .is_finished_writing = true}};
+}
+
+auto StbVorbisDecoder::SeekStream(cpp::span<const std::byte> input,
+                                  std::size_t target_sample) -> Result<void> {
+  // TODO(jacqueline): Implement me.
+  return {0, {}};
+}
+
+}  // namespace codecs
-- 
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