Added a helper function to modulate using CC values

src/sfizz/MidiState.h

@@ -8,6 +8,8 @@
 #include <chrono>
 #include <array>
 #include "SfzHelpers.h"
+#include "CCMap.h"
+#include "Range.h"
 
 namespace sfz
 {
@@ -103,6 +105,26 @@ public:
      */
     void resetAllControllers() noexcept;
 
+    /**
+     * @brief Modulate a value using the last entered CCs in the midiState
+     *
+     * @tparam T
+     * @tparam U
+     * @param value the base value
+     * @param modifiers the list of CC modifiers
+     * @param validRange a range to clamp the output
+     * @param lambda the function to apply for each modifier
+     * @return T
+     */
+    template<class T, class U>
+    T modulate(T value, const CCMap<U>& modifiers, const Range<T>& validRange, const modFunction<T, U>& lambda = addToBase<T>) const noexcept
+    {
+        for (auto& mod: modifiers) {
+            lambda(value, getCCValue(mod.first) * mod.second);
+        }
+        return validRange.clamp(value);
+    }
+
 private:
     template<class T>
     using MidiNoteArray = std::array<T, 128>;

src/sfizz/SfzHelpers.h

@@ -172,5 +172,37 @@ bool findDefine(absl::string_view line, absl::string_view& variable, absl::strin
  */
 bool findInclude(absl::string_view line, std::string& path);
 
+/**
+ * @brief Defines a function that modulates a base value with another one
+ *
+ * @tparam T
+ */
+template<class T, class U>
+using modFunction = std::function<void(T&, U)>;
+
+/**
+ * @brief Modulation helper that adds the modifier to the base value
+ *
+ * @tparam T
+ * @param base the base value
+ * @param modifier the modifier value
+ */
+template<class T>
+constexpr void addToBase(T& base, T modifier)
+{
+    base += modifier;
+}
+
+/**
+ * @brief multiply a value by a factor, in cents. To be used for pitch variations.
+ *
+ * @param base
+ * @param modifier
+ */
+constexpr void multiplyByCents(float& base, int modifier)
+{
+    base *= centsFactor(modifier);
+}
+
 } // namespace sfz