Added comments and working on the filter pool

src/sfizz/FilterPool.cpp

@@ -1,6 +1,10 @@
 #include "FilterPool.h"
 #include "SIMDHelpers.h"
 #include "absl/algorithm/container.h"
+#include "AtomicGuard.h"
+#include <thread>
+#include <chrono>
+using namespace std::chrono_literals;
 
 sfz::FilterHolder::FilterHolder(const MidiState& midiState)
 : midiState(midiState)
@@ -43,24 +47,36 @@ void sfz::FilterHolder::process(const float** inputs, float** outputs, unsigned
 
     // TODO: Once the midistate envelopes are done, add modulation in there!
     // For now we take the last value
-    auto cutoff = baseCutoff;
+    lastCutoff = baseCutoff;
     for (auto& mod: description->cutoffCC) {
-        cutoff *= centsFactor(midiState.getCCValue(mod.first) * mod.second);
+        lastCutoff *= centsFactor(midiState.getCCValue(mod.first) * mod.second);
     }
 
-    auto resonance = baseResonance;
+    lastResonance = baseResonance;
     for (auto& mod: description->resonanceCC) {
-        resonance += midiState.getCCValue(mod.first) * mod.second;
+        lastResonance += midiState.getCCValue(mod.first) * mod.second;
     }
 
-    auto gain = baseGain;
+    lastGain = baseGain;
     for (auto& mod: description->gainCC) {
-        gain += midiState.getCCValue(mod.first) * mod.second;
+        lastResonance += midiState.getCCValue(mod.first) * mod.second;
     }
 
-    filter.process(inputs, outputs, cutoff, resonance, gain,numFrames);
+    filter.process(inputs, outputs, lastCutoff, lastResonance, lastGain, numFrames);
 }
 
+float sfz::FilterHolder::getLastCutoff() const
+{
+    return lastCutoff;
+}
+float sfz::FilterHolder::getLastResonance() const
+{
+    return lastResonance;
+}
+float sfz::FilterHolder::getLastGain() const
+{
+    return lastGain;
+}
 
 sfz::FilterPool::FilterPool(const MidiState& state, int numFilters)
 : midiState(state)
@@ -70,6 +86,10 @@ sfz::FilterPool::FilterPool(const MidiState& state, int numFilters)
 
 sfz::FilterHolderPtr sfz::FilterPool::getFilter(const FilterDescription& description, int noteNumber, uint8_t velocity)
 {
+    AtomicGuard guard { givingOutFilters };
+    if (!canGiveOutFilters)
+        return {};
+
     auto filter = absl::c_find_if(filters, [](const FilterHolderPtr& holder) {
         return holder.use_count() == 1;
     });
@@ -81,17 +101,34 @@ sfz::FilterHolderPtr sfz::FilterPool::getFilter(const FilterDescription& descrip
     return *filter;
 }
 
-int sfz::FilterPool::getActiveFilters() const
+size_t sfz::FilterPool::getActiveFilters() const
 {
     return absl::c_count_if(filters, [](const FilterHolderPtr& holder) {
         return holder.use_count() > 1;
     });
 }
 
-void sfz::FilterPool::setNumFilters(int numFilters)
+size_t sfz::FilterPool::setNumFilters(size_t numFilters)
 {
-    filters.clear();
-    filters.reserve(numFilters);
-    for (int i = 0; i < numFilters; ++i)
+    AtomicDisabler disabler { canGiveOutFilters };
+
+    while(givingOutFilters)
+        std::this_thread::sleep_for(1ms);
+
+    auto filterIterator = filters.begin();
+    auto filterSentinel = filters.rbegin();
+    while (filterIterator < filterSentinel.base()) {
+        if (filterIterator->use_count() == 1) {
+            std::iter_swap(filterIterator, filterSentinel);
+            ++filterSentinel;
+        } else {
+            ++filterIterator;
+        }
+    }
+
+    filters.resize(std::distance(filters.begin(), filterSentinel.base()));
+    for (size_t i = filters.size(); i < numFilters; ++i)
         filters.emplace_back(std::make_shared<FilterHolder>(midiState));
+
+    return filters.size();
 }

src/sfizz/FilterPool.h

@@ -13,16 +13,54 @@ class FilterHolder
 public:
     FilterHolder() = delete;
     FilterHolder(const MidiState& state);
-    void reset();
+    /**
+     * @brief Setup a new filter based on a filter description, and a triggering note parameters.
+     *
+     * @param description the filter description
+     * @param noteNumber the triggering note number
+     * @param velocity the triggering note velocity
+     */
     void setup(const FilterDescription& description, int noteNumber = static_cast<int>(Default::filterKeycenter), uint8_t velocity = 0);
+    /**
+     * @brief Process a block of stereo inputs
+     *
+     * @param inputs
+     * @param outputs
+     * @param numFrames
+     */
     void process(const float** inputs, float** outputs, unsigned numFrames);
+    /**
+     * @brief Returns the last value of the cutoff for the filter
+     *
+     * @return float
+     */
+    float getLastCutoff() const;
+    /**
+     * @brief Returns the last value of the resonance for the filter
+     *
+     * @return float
+     */
+    float getLastResonance() const;
+    /**
+     * @brief Returns the last value of the gain for the filter
+     *
+     * @return float
+     */
+    float getLastGain() const;
 private:
+    /**
+     * Reset the filter. Is called internally when using setup().
+     */
+    void reset();
     const MidiState& midiState;
     const FilterDescription* description;
     Filter filter;
     float baseCutoff { Default::filterCutoff };
     float baseResonance { Default::filterResonance };
     float baseGain { Default::filterGain };
+    float lastCutoff { Default::filterCutoff };
+    float lastResonance { Default::filterResonance };
+    float lastGain { Default::filterGain };
     using filterRandomDist = std::uniform_int_distribution<int>;
     filterRandomDist dist { 0, sfz::Default::filterRandom };
 };
@@ -33,11 +71,42 @@ class FilterPool
 {
 public:
     FilterPool() = delete;
+    /**
+     * @brief Construct a new Filter Pool object
+     *
+     * @param state the associated midi state
+     * @param numFilters the number of inactive filters to hold in the pool
+     */
     FilterPool(const MidiState& state, int numFilters = config::defaultNumFilters);
+    /**
+     * @brief Get a filter object to use in Voices
+     *
+     * @param description the filter description to bind to the filter
+     * @param noteNumber the triggering note number
+     * @param velocity the triggering note velocity
+     * @return FilterHolderPtr release this when done with the filter; no deallocation will be done
+     */
     FilterHolderPtr getFilter(const FilterDescription& description, int noteNumber = static_cast<int>(Default::filterKeycenter), uint8_t velocity = 0);
-    int getActiveFilters() const;
-    void setNumFilters(int numFilters);
+    /**
+     * @brief Get the number of active filters
+     *
+     * @return size_t
+     */
+    size_t getActiveFilters() const;
+    /**
+     * @brief Set the number of filters in the pool. This function may sleep and should be called from a background thread.
+     * No filters will be distributed during the reallocation of filters. Existing running filters are kept. If the target
+     * number of filters is less that the number of active filters, the function will not remove them and you may need
+     * to call it again after existing filters have run out.
+     *
+     * @param numFilters
+     * @return size_t the actual number of filters in the pool
+     */
+    size_t setNumFilters(size_t numFilters);
 private:
+    std::atomic<bool> givingOutFilters { false };
+    std::atomic<bool> canGiveOutFilters { true };
+
     const MidiState& midiState;
     std::vector<FilterHolderPtr> filters;
 };