clang-tidy

.clang-format

@@ -7,7 +7,10 @@ Standard: c++14
 ColumnLimit: 100
 AllowShortIfStatementsOnASingleLine: false
 AlignArrayOfStructures: Left
-AlignConsecutiveAssignments: Consecutive
+AlignConsecutiveAssignments:
+  Enabled: true
+  AcrossEmptyLines: false
+  AcrossComments: true
 AllowShortFunctionsOnASingleLine: Empty
 AllowShortCaseLabelsOnASingleLine: true
 AlignConsecutiveShortCaseStatements:

.clang-tidy

@@ -0,0 +1,23 @@
+Checks: >
+  bugprone-*,
+  -bugprone-easily-swappable-parameters,
+  -bugprone-implicit-widening-of-multiplication-result,
+  cert-*,
+  -cert-err58-cpp,
+  cppcoreguidelines-*,
+  -cppcoreguidelines-avoid-magic-numbers,
+  -cppcoreguidelines-pro-bounds-constant-array-index,
+  google-explicit-constructor,
+  hicpp-*,
+  -hicpp-braces-around-statements,
+  -hicpp-uppercase-literal-suffix,
+  misc-*,
+  -misc-non-private-member-variables-in-classes,
+  modernize-*,
+  -modernize-use-trailing-return-type,
+  performance-*,
+  portability-*,
+  readability-misplaced-array-index,
+  readability-redundant-*,
+  readability-reference-to-constructed-temporary,
+  readability-suspicious-call-argument

.github/workflows/tidy.yml

@@ -0,0 +1,22 @@
+name: tidy
+
+on:
+  push:
+    branches: [ master, dev ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  clang-tidy:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4
+    - name: install dependencies
+      run: sudo apt install libsndfile1-dev libliquid-dev nlohmann-json3-dev meson clang-tidy
+    - name: meson setup
+      run: meson setup -Dwerror=true build
+    - name: compile
+      run: cd build && meson compile
+    - name: run clang-tidy
+      run: clang-tidy -p build `find src -name '*.cc' -o -name '*.h'`

src/block_sync.cc

@@ -29,9 +29,9 @@ constexpr int kMaxTolerableBLER = 85;
 
 constexpr int kMaxErrorsToleratedOver50Blocks{kMaxTolerableBLER / 2};
 
-constexpr int kBlockLength       = 26;
-constexpr unsigned kBlockBitmask = (1 << kBlockLength) - 1;
-constexpr int kCheckwordLength   = 10;
+constexpr std::uint32_t kBlockLength     = 26;
+constexpr std::uint32_t kBlockBitmask    = (1U << kBlockLength) - 1U;
+constexpr std::uint32_t kCheckwordLength = 10;
 
 // Each offset word is associated with one block number
 eBlockNumber getBlockNumberForOffset(Offset offset) {
@@ -113,7 +113,8 @@ uint32_t calculateSyndrome(uint32_t vec) {
   uint32_t result{};
 
   for (size_t k = 0; k < parity_check_matrix.size(); k++)
-    result ^= parity_check_matrix[parity_check_matrix.size() - 1 - k] * ((vec >> k) & 0b1);
+    result ^= static_cast<std::uint32_t>(parity_check_matrix[parity_check_matrix.size() - 1U - k] *
+                                         (static_cast<std::uint32_t>(vec >> k) & 1U));
 
   return result;
 }
@@ -237,7 +238,7 @@ void BlockStream::acquireSync(Block block) {
 }
 
 void BlockStream::pushBit(bool bit) {
-  input_register_ = (input_register_ << 1) + bit;
+  input_register_ = (input_register_ << 1U) + bit;
   num_bits_until_next_block_--;
   bitcount_++;
 

src/common.h

@@ -24,9 +24,17 @@
 namespace redsea {
 
 constexpr float kBitsPerSecond        = 1187.5f;
-constexpr float kMinimumSampleRate_Hz = 128000.0f;
+// Minimum sensible rate to still have RDS below Nyquist
+constexpr float kMinimumSampleRate_Hz = 128'000.f;
 constexpr int kNumBlerAverageGroups   = 12;
-constexpr float kTargetSampleRate_Hz  = 171000.0f;
+constexpr float kTargetSampleRate_Hz  = 171'000.f;
+
+// Limit of the resamp_rrrf object
+constexpr float kLiquidMinimumResamplerRatio = 0.004f;
+constexpr float kMaximumSampleRate_Hz        = 40'000'000.f;
+static_assert(kMaximumSampleRate_Hz < kTargetSampleRate_Hz / kLiquidMinimumResamplerRatio, "");
+
+constexpr float kMaxResampleRatio = kTargetSampleRate_Hz / kMinimumSampleRate_Hz;
 
 struct BitBuffer {
   std::chrono::time_point<std::chrono::system_clock> time_received;

src/dsp/liquid_wrappers.h

@@ -30,7 +30,7 @@ extern "C" {
 }
 #pragma clang diagnostic pop
 
-template<typename T>
+template <typename T>
 struct Maybe {
   T data;
   bool valid;
@@ -41,7 +41,9 @@ namespace liquid {
 class AGC {
  public:
   AGC(float bw, float initial_gain);
-  AGC(const AGC&) = delete;
+  AGC(const AGC&)            = delete;
+  AGC& operator=(const AGC&) = delete;
+
   ~AGC();
   std::complex<float> execute(std::complex<float> s);
 
@@ -52,7 +54,9 @@ class AGC {
 class FIRFilter {
  public:
   FIRFilter(unsigned int len, float fc, float As = 60.0f, float mu = 0.0f);
-  FIRFilter(const FIRFilter&) = delete;
+  FIRFilter(const FIRFilter&)            = delete;
+  FIRFilter& operator=(const FIRFilter&) = delete;
+
   ~FIRFilter();
   void push(std::complex<float> s);
   std::complex<float> execute();
@@ -65,7 +69,8 @@ class FIRFilter {
 class NCO {
  public:
   NCO(liquid_ncotype type, float freq);
-  NCO(const NCO&) = delete;
+  NCO(const NCO&)            = delete;
+  NCO& operator=(const NCO&) = delete;
   ~NCO();
   std::complex<float> mixDown(std::complex<float> s);
   void step();
@@ -80,9 +85,9 @@ class NCO {
 
 class SymSync {
  public:
-  SymSync(liquid_firfilt_type ftype, unsigned k, unsigned m,
-          float beta, unsigned num_filters);
-  SymSync(const SymSync&) = delete;
+  SymSync(liquid_firfilt_type ftype, unsigned k, unsigned m, float beta, unsigned num_filters);
+  SymSync(const SymSync&)            = delete;
+  SymSync& operator=(const SymSync&) = delete;
   ~SymSync();
   void reset();
   void setBandwidth(float);
@@ -97,7 +102,8 @@ class SymSync {
 class Modem {
  public:
   explicit Modem(modulation_scheme scheme);
-  Modem(const Modem&) = delete;
+  Modem(const Modem&)            = delete;
+  Modem& operator=(const Modem&) = delete;
   ~Modem();
   unsigned int demodulate(std::complex<float> sample);
   float getPhaseError();
@@ -113,7 +119,8 @@ class Modem {
 class Resampler {
  public:
   explicit Resampler(float ratio, unsigned int length);
-  Resampler(const Resampler&) = delete;
+  Resampler(const Resampler&)            = delete;
+  Resampler& operator=(const Resampler&) = delete;
   ~Resampler();
   unsigned int execute(float in, float* out);
 
@@ -123,4 +130,4 @@ class Resampler {
 
 }  // namespace liquid
 
-#endif // DSP_LIQUID_WRAPPERS_H_
+#endif  // DSP_LIQUID_WRAPPERS_H_

src/dsp/subcarrier.cc

@@ -16,6 +16,7 @@
  */
 #include "src/dsp/subcarrier.h"
 
+#include <cassert>
 #include <cmath>
 #include <complex>
 #include <cstdio>
@@ -51,7 +52,7 @@ constexpr float hertz2step(float Hz) {
 // At correct clock phase, evaluate symbol in
 // constellation {-1,0} => 0, {1,0} => 1
 Maybe<bool> BiphaseDecoder::push(std::complex<float> psk_symbol) {
-  Maybe<bool> result;
+  Maybe<bool> result{};
 
   const auto biphase_symbol = (psk_symbol - prev_psk_symbol_) * 0.5f;
   result.data               = biphase_symbol.real() >= 0.0f;
@@ -112,33 +113,47 @@ void Subcarrier::reset() {
 
 /** MPX to bits
  */
-BitBuffer Subcarrier::processChunk(MPXBuffer<>& chunk) {
+BitBuffer Subcarrier::processChunk(MPXBuffer& input_chunk) {
   if (resample_ratio_ != 1.0f) {
-    unsigned int i_resampled = 0;
-    for (size_t i = 0; i < chunk.used_size; i++) {
-      static float buf[4];
-      const auto num_resampled = resampler_.execute(chunk.data[i], buf);
+    std::size_t i_resampled{};
 
-      for (unsigned int j = 0; j < num_resampled; j++) {
-        resampled_buffer_.data[i_resampled] = buf[j];
+    // ceil(resample_ratio) is enough, as per liquid-dsp's API, but std::ceil is not constexpr in
+    // C++14
+    constexpr std::size_t kMaxResamplerOutputSize = static_cast<std::size_t>(kMaxResampleRatio) + 1;
+    std::array<float, kMaxResamplerOutputSize> resamp_output{};
+
+    for (size_t i_input{}; i_input < input_chunk.used_size; i_input++) {
+      const auto num_resampled =
+          resampler_.execute(input_chunk.data[i_input], resamp_output.data());
+
+      // Always true as per liquid-dsp API
+      assert(num_resampled <= resamp_output.size());
+
+      for (unsigned int i_buf{}; i_buf < num_resampled; i_buf++) {
+        // Must always be true due to our selection of maximum resampler ratio and extra room in
+        // the chunk
+        assert(i_resampled < resampled_chunk_.data.size());
+
+        resampled_chunk_.data[i_resampled] = resamp_output[i_buf];
         i_resampled++;
       }
     }
-    resampled_buffer_.used_size = i_resampled;
+    resampled_chunk_.used_size = i_resampled;
+    assert(resampled_chunk_.used_size <= resampled_chunk_.data.size());
   }
 
-  MPXBuffer<>& buf = (resample_ratio_ == 1.0f ? chunk : resampled_buffer_);
+  MPXBuffer& chunk = (resample_ratio_ == 1.0f ? input_chunk : resampled_chunk_);
 
   constexpr int decimate_ratio =
       static_cast<int>(kTargetSampleRate_Hz / kBitsPerSecond / 2 / kSamplesPerSymbol);
 
   BitBuffer bitbuffer;
-  bitbuffer.time_received = chunk.time_received;
+  bitbuffer.time_received = input_chunk.time_received;
 
-  for (size_t i = 0; i < buf.used_size; i++) {
+  for (size_t i = 0; i < chunk.used_size; i++) {
     // Mix RDS to baseband for filtering purposes
     const std::complex<float> sample_baseband =
-        oscillator_.mixDown(std::complex<float>(buf.data[i]));
+        oscillator_.mixDown(std::complex<float>(chunk.data[i]));
 
     fir_lpf_.push(sample_baseband);
 

src/dsp/subcarrier.h

@@ -56,7 +56,7 @@ class Subcarrier {
   explicit Subcarrier(const Options& options);
   ~Subcarrier() = default;
   bool eof() const;
-  BitBuffer processChunk(MPXBuffer<>& chunk);
+  BitBuffer processChunk(MPXBuffer& input_chunk);
   void reset();
   float getSecondsSinceLastReset() const;
 
@@ -72,7 +72,7 @@ class Subcarrier {
   liquid::Modem modem_;
   liquid::Resampler resampler_;
 
-  MPXBuffer<> resampled_buffer_{};
+  MPXBuffer resampled_chunk_{};
 
   bool is_eof_{false};