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1 #pragma once
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2
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3 namespace collidoscope {
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4
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5
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6 /*
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7 * An ASR envelope with linear shape. It is modeled after the STK envelope classes.
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8 * The tick() method advances the computation of the envelope one sample and returns the computed sample
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9 * The class is templated for the type of the samples that each tick of the envelope produces.
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10 *
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11 * Client classes can set/get the current state of the envelope with the
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12 * respective getter/setter methods
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13 *
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14 */
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15 template <typename T>
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16 class EnvASR
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17 {
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18 public:
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19
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20 enum class State {
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21 eAttack,
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22 eSustain,
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23 eRelease,
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24 eIdle // before attack after release
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25 };
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26
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27 EnvASR( T sustainLevel, T attackTime, T releaseTime, std::size_t sampleRate ) :
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28 mSustainLevel( sustainLevel ),
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29 mState( State::eIdle ),
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30 mValue( 0 )
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31
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32 {
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33 if ( attackTime <= 0 )
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34 attackTime = T( 0.001 );
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35
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36 if ( releaseTime <= 0 )
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37 releaseTime = T( 0.001 );
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38
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39 mAttackRate = T( 1.0 ) / (attackTime * sampleRate);
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40 mReleaseRate = T( 1.0 ) / (releaseTime * sampleRate);
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41 }
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42
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43 T tick()
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44 {
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45
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46 switch ( mState )
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47 {
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48
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49 case State::eIdle: {
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50 mValue = 0;
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51 };
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52 break;
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53
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54 case State::eAttack: {
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55 mValue += mAttackRate;
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56 if ( mValue >= mSustainLevel ){
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57 mValue = mSustainLevel;
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58 mState = State::eSustain;
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59 }
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60 };
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61 break;
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62
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63 case State::eRelease:
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64 mValue -= mReleaseRate;
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65 if ( mValue <= 0 ){
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66 mValue = 0;
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67 mState = State::eIdle;
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68 }
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69 break;
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70 default:
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71 break;
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72 }
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73
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74 return mValue;
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75
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76 }
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77
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78 State getState() const
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79 {
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80 return mState;
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81 }
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82
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83 void setState( State state )
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84 {
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85 mState = state;
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86 }
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87
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88 private:
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89 T mSustainLevel;
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90 T mAttackRate;
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91 T mReleaseRate;
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92
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93 // output
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94 T mValue;
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95
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96 State mState;
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97
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98 };
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99
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100
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101 }
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