Avoid frequent allocation of little vectors of pointers in stretch

libraries/lib-stretching-sequence/AudioSegment.h

@@ -27,13 +27,12 @@ class STRETCHING_SEQUENCE_API AudioSegment
    /**
     * @brief Fills `buffers` with as many as `numSamples` or the number of
     * remaining samples, whichever is smaller.
-    * @param buffers A vector of pointers to buffers, one for each channel.
+    * @param buffers Pointers to buffers, one for each channel.
     * @param numSamples The max. number of samples to write to each buffer.
-    * @pre `buffers.size() == GetWidth()`
     * @return The number of samples actually provided in each buffer.
     */
    virtual size_t
-   GetFloats(std::vector<float*>& buffers, size_t numSamples) = 0;
+   GetFloats(float *const *buffers, size_t numSamples) = 0;
 
    /**
     * @brief The number of channels in the segment.

libraries/lib-stretching-sequence/ClipSegment.cpp

@@ -46,12 +46,11 @@ ClipSegment::ClipSegment(
 {
 }
 
-size_t ClipSegment::GetFloats(std::vector<float*>& buffers, size_t numSamples)
+size_t ClipSegment::GetFloats(float *const *buffers, size_t numSamples)
 {
-   assert(buffers.size() == mSource.GetWidth());
    const auto numSamplesToProduce = limitSampleBufferSize(
       numSamples, mTotalNumSamplesToProduce - mTotalNumSamplesProduced);
-   mStretcher->GetSamples(buffers.data(), numSamplesToProduce);
+   mStretcher->GetSamples(buffers, numSamplesToProduce);
    mTotalNumSamplesProduced += numSamplesToProduce;
    return numSamplesToProduce;
 }

libraries/lib-stretching-sequence/ClipSegment.h

@@ -26,7 +26,7 @@ class STRETCHING_SEQUENCE_API ClipSegment final : public AudioSegment
       const ClipInterface&, double durationToDiscard, PlaybackDirection);
 
    // AudioSegment
-   size_t GetFloats(std::vector<float*>& buffers, size_t numSamples) override;
+   size_t GetFloats(float *const *buffers, size_t numSamples) override;
    bool Empty() const override;
    size_t GetWidth() const override;
 

libraries/lib-stretching-sequence/SilenceSegment.cpp

@@ -20,9 +20,8 @@ SilenceSegment::SilenceSegment(size_t numChannels, sampleCount numSamples)
 }
 
 size_t
-SilenceSegment::GetFloats(std::vector<float*>& buffers, size_t numSamples)
+SilenceSegment::GetFloats(float *const *buffers, size_t numSamples)
 {
-   assert(buffers.size() == mNumChannels);
    const size_t numSamplesToProduce =
       std::min<long long>(mNumRemainingSamples.as_long_long(), numSamples);
    for (auto i = 0u; i < mNumChannels; ++i)

libraries/lib-stretching-sequence/SilenceSegment.h

@@ -18,7 +18,7 @@ class STRETCHING_SEQUENCE_API SilenceSegment final : public AudioSegment
 {
 public:
    SilenceSegment(size_t numChannels, sampleCount numSamples);
-   size_t GetFloats(std::vector<float*>& buffers, size_t numSamples) override;
+   size_t GetFloats(float *const *buffers, size_t numSamples) override;
    bool Empty() const override;
    size_t GetWidth() const override;
 

libraries/lib-stretching-sequence/StretchingSequence.cpp

@@ -17,13 +17,14 @@
 
 namespace
 {
-std::vector<float*>
-GetOffsetBuffer(float* const* buffer, size_t numChannels, size_t offset)
+#define stackAllocate(T, count) static_cast<T*>(alloca(count * sizeof(T)))
+
+void
+GetOffsetBuffer(float **offsetBuffer,
+   float* const* buffer, size_t numChannels, size_t offset)
 {
-   std::vector<float*> offsetBuffer(numChannels);
    for (auto i = 0u; i < numChannels; ++i)
       offsetBuffer[i] = buffer[i] + offset;
-   return offsetBuffer;
 }
 } // namespace
 
@@ -54,8 +55,9 @@ bool StretchingSequence::GetNext(
           mActiveAudioSegmentIt != mAudioSegments.end())
    {
       const auto& segment = *mActiveAudioSegmentIt;
-      auto offsetBuffers =
-         GetOffsetBuffer(buffers, mSequence.NChannels(), numProcessedSamples);
+      const auto offsetBuffers = stackAllocate(float *, mSequence.NChannels());
+      GetOffsetBuffer(offsetBuffers,
+         buffers, mSequence.NChannels(), numProcessedSamples);
       numProcessedSamples += segment->GetFloats(
          offsetBuffers,
          numSamples - numProcessedSamples); // No need to reverse, we feed the
@@ -67,8 +69,9 @@ bool StretchingSequence::GetNext(
    const auto remaining = numSamples - numProcessedSamples;
    if (remaining > 0u)
    {
-      const auto offsetBuffers =
-         GetOffsetBuffer(buffers, mSequence.NChannels(), numProcessedSamples);
+      const auto offsetBuffers = stackAllocate(float *, mSequence.NChannels());
+      GetOffsetBuffer(
+         offsetBuffers, buffers, mSequence.NChannels(), numProcessedSamples);
       for (auto i = 0u; i < mSequence.NChannels(); ++i)
          std::fill(offsetBuffers[i], offsetBuffers[i] + remaining, 0.f);
    }

libraries/lib-stretching-sequence/tests/ClipSegmentTest.cpp

@@ -38,7 +38,7 @@ TEST_CASE("ClipSegment")
                FloatVectorVector { { 1.f, 2.f, 3.f }, { -1.f, -2.f, -3.f } });
       ClipSegment sut { *clip, 0., direction };
       AudioContainer output(sampleRate, numChannels);
-      REQUIRE(sut.GetFloats(output.channelPointers, sampleRate) == sampleRate);
+      REQUIRE(sut.GetFloats(output.channelPointers.data(), sampleRate) == sampleRate);
       if (numChannels == 1u)
       {
          const auto expected = direction == PlaybackDirection::forward ?
@@ -69,7 +69,7 @@ TEST_CASE("ClipSegment")
       constexpr auto playbackOffset = 2 / static_cast<double>(sampleRate);
       ClipSegment sut { *clip, playbackOffset, direction };
       AudioContainer output(numSamples, 1u);
-      REQUIRE(sut.GetFloats(output.channelPointers, numSamples) == 3);
+      REQUIRE(sut.GetFloats(output.channelPointers.data(), numSamples) == 3);
       const auto expected = direction == PlaybackDirection::forward ?
                                std::vector<float> { 3.f, 4.f, 5.f, 0.f, 0.f } :
                                std::vector<float> { 3.f, 2.f, 1.f, 0.f, 0.f };

libraries/lib-stretching-sequence/tests/MockAudioSegmentFactory.h

@@ -16,7 +16,7 @@
 class NiceAudioSegment final : public AudioSegment
 {
 public:
-   size_t GetFloats(std::vector<float*>&, size_t numSamples) override
+   size_t GetFloats(float *const *, size_t numSamples) override
    {
       return numSamples;
    }

libraries/lib-stretching-sequence/tests/SilenceSegmentTest.cpp

@@ -21,8 +21,8 @@ TEST_CASE("SilenceSegment", "behaves as expected")
    SilenceSegment sut(numChannels, silenceSegmentLength);
    REQUIRE(!sut.Empty());
    AudioContainer container(3u, numChannels);
-   REQUIRE(sut.GetFloats(container.channelPointers, 1) == 1);
+   REQUIRE(sut.GetFloats(container.channelPointers.data(), 1) == 1);
    REQUIRE(!sut.Empty());
-   REQUIRE(sut.GetFloats(container.channelPointers, 3) == 2);
+   REQUIRE(sut.GetFloats(container.channelPointers.data(), 3) == 2);
    REQUIRE(sut.Empty());
 }

libraries/lib-time-and-pitch/StaffPadTimeAndPitch.cpp

@@ -10,15 +10,14 @@ namespace
 // to be specified in the `setup` call.)
 constexpr auto maxBlockSize = 1024;
 
-std::vector<float*>
-GetOffsetBuffer(float* const* buffer, size_t numChannels, size_t offset)
+#define stackAllocate(T, count) static_cast<T*>(alloca(count * sizeof(T)))
+
+void
+GetOffsetBuffer(float **offsetBuffer,
+   float* const* buffer, size_t numChannels, size_t offset)
 {
-   std::vector<float*> offsetBuffer(numChannels);
    for (auto i = 0u; i < numChannels; ++i)
-   {
       offsetBuffer[i] = buffer[i] + offset;
-   }
-   return offsetBuffer;
 }
 
 std::unique_ptr<staffpad::TimeAndPitch> MaybeCreateTimeAndPitch(
@@ -82,9 +81,9 @@ void StaffPadTimeAndPitch::GetSamples(float* const* output, size_t outputLen)
          const auto numSamplesToGet =
             std::min({ maxBlockSize, numOutputSamplesAvailable,
                        static_cast<int>(outputLen - numOutputSamples) });
-         const auto buffer =
-            GetOffsetBuffer(output, mNumChannels, numOutputSamples);
-         mTimeAndPitch->retrieveAudio(buffer.data(), numSamplesToGet);
+         const auto buffer = stackAllocate(float*, mNumChannels);
+         GetOffsetBuffer(buffer, output, mNumChannels, numOutputSamples);
+         mTimeAndPitch->retrieveAudio(buffer, numSamplesToGet);
          numOutputSamplesAvailable -= numSamplesToGet;
          numOutputSamples += numSamplesToGet;
       }