ADSR.h

#ifndef STK_ADSR_H
#define STK_ADSR_H

#include "Generator.h"

namespace stk {

/***************************************************/
/***************************************************/

class ADSR : public Generator
{
 public:

  enum {
    ATTACK,   
    DECAY,    
    SUSTAIN,  
    RELEASE,  
    IDLE      
  };

  ADSR( void );

  ~ADSR( void );

  void keyOn( void );

  void keyOff( void );

  void setAttackRate( StkFloat rate );

  void setAttackTarget( StkFloat target );

  void setDecayRate( StkFloat rate );

  void setSustainLevel( StkFloat level );

  void setReleaseRate( StkFloat rate );

  void setAttackTime( StkFloat time );

  void setDecayTime( StkFloat time );

  void setReleaseTime( StkFloat time );

  void setAllTimes( StkFloat aTime, StkFloat dTime, StkFloat sLevel, StkFloat rTime );

  void setTarget( StkFloat target );

  int getState( void ) const { return state_; };

  void setValue( StkFloat value );

  StkFloat lastOut( void ) const { return lastFrame_[0]; };

  StkFloat tick( void );


  StkFrames& tick( StkFrames& frames, unsigned int channel = 0 );

 protected:  

  void sampleRateChanged( StkFloat newRate, StkFloat oldRate );

  int state_;
  StkFloat value_;
  StkFloat target_;
  StkFloat attackRate_;
  StkFloat decayRate_;
  StkFloat releaseRate_;
  StkFloat releaseTime_;
  StkFloat sustainLevel_;
};

inline StkFloat ADSR :: tick( void )
{
  switch ( state_ ) {

  case ATTACK:
    value_ += attackRate_;
    if ( value_ >= target_ ) {
      value_ = target_;
      target_ = sustainLevel_;
             state_ = DECAY;
    }
    lastFrame_[0] = value_;
    break;

  case DECAY:
    if ( value_ > sustainLevel_ ) {
      value_ -= decayRate_;
      if ( value_ <= sustainLevel_ ) {
        value_ = sustainLevel_;
        state_ = SUSTAIN;
      }
    }
    else {
      value_ += decayRate_; // attack target < sustain level
      if ( value_ >= sustainLevel_ ) {
        value_ = sustainLevel_;
        state_ = SUSTAIN;
      }
    }
    lastFrame_[0] = value_;
    break;

  case RELEASE:
    value_ -= releaseRate_;
    if ( value_ <= 0.0 ) {
      value_ = 0.0;
      state_ = IDLE;
    }
    lastFrame_[0] = value_;

  }

  return value_;
}

inline StkFrames& ADSR :: tick( StkFrames& frames, unsigned int channel )
{
#if defined(_STK_DEBUG_)
  if ( channel >= frames.channels() ) {
    oStream_ << "ADSR::tick(): channel and StkFrames arguments are incompatible!";
    handleError( StkError::FUNCTION_ARGUMENT );
  }
#endif

  StkFloat *samples = &frames[channel];
  unsigned int hop = frames.channels();
  for ( unsigned int i=0; i<frames.frames(); i++, samples += hop )
    *samples = ADSR::tick();

  return frames;
}

} // stk namespace

#endif