crossfade_ramp.hpp

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// sbl/dsp/primitives/crossfade_ramp.hpp — A gain ramped linearly across one block
//
// A mix or a gain that stepped at block rate would click; this carries it
// from last block's value to this block's, one equal step per sample.
 
#ifndef SBL_DSP_PRIMITIVES_CROSSFADE_RAMP_HPP_
#define SBL_DSP_PRIMITIVES_CROSSFADE_RAMP_HPP_
 
#include <cstdint>
 
namespace sbl::dsp::primitives {
 
class CrossfadeRamp {
public:
    /// @note All public methods are ISR-safe — bounded computation, no I/O.
 
    /// Start a block that ends at `target` after `n` steps.
    void begin(float target, uint16_t n) {
        step_ = (target - value_) / static_cast<float>(n);
        end_ = target;
    }
 
    /// The value for the next sample.
    float next() { return value_ += step_; }
 
    /// Close the block exactly on its target, so rounding never drifts.
    void end() { value_ = end_; }
 
    float value() const { return value_; }
    void reset(float value) { value_ = value; end_ = value; step_ = 0.0f; }
 
private:
    float value_ = 0.0f;
    float end_ = 0.0f;
    float step_ = 0.0f;
};
 
} // namespace sbl::dsp::primitives
 
#endif // SBL_DSP_PRIMITIVES_CROSSFADE_RAMP_HPP_