module SPCore
class Gain
  
  #MAX_DB = 72
  #NUM_DB_HALF_STEPS=146
  #DB_TO_SCALAR_TABLE = [
  #  1.0,              # 0 dB
  #  1.059253725,      # 0.5
  #  1.122018454,      # 1
  #  1.188502227,      # 1.5
  #  1.258925412,      # 2
  #  1.333521432,      # 2.5
  #  1.412537545,      # 3
  #  1.496235656,      # 3.5
  #  1.584893192,      # 4
  #  1.678804018,      # 4.5
  #  1.77827941,       # 5
  #  1.883649089,      # 5.5
  #  1.995262315,      # 6
  #  2.11348904,       # 6.5
  #  2.238721139,      # 7
  #  2.371373706,      # 7.5
  #  2.511886432,      # 8
  #  2.66072506,       # 8.5
  #  2.818382931,      # 9
  #  2.985382619,      # 9.5
  #  3.16227766,       # 10 dB
  #  3.349654392,      # 10.5
  #  3.548133892,      # 11
  #  3.758374043,      # 11.5
  #  3.981071706,      # 12
  #  4.216965034,      # 12.5
  #  4.466835922,      # 13
  #  4.73151259,       # /13.5
  #  5.011872336,      # 14
  #  5.308844442,      # 14.5
  #  5.623413252,      # 15
  #  5.956621435,      # 15.5
  #  6.309573445,      # 16
  #  6.683439176,      # 16.5
  #  7.079457844,      # 17
  #  7.498942093,      # 17.5
  #  7.943282347,      # 18
  #  8.413951416,      # 18.5
  #  8.912509381,      # 19
  #  9.440608763,      # 19.5
  #  10.0,             # 20 dB
  #  10.59253725,      # 20.5
  #  11.22018454,      # 21
  #  11.88502227,      # 21.5
  #  12.58925412,      # 22
  #  13.33521432,      # 22.5
  #  14.12537545,      # 23
  #  14.96235656,      # 23.5
  #  15.84893192,      # 24
  #  16.78804018,      # 24.5
  #  17.7827941,       # 25
  #  18.83649089,      # 25.5
  #  19.95262315,      # 26
  #  21.1348904,       # 26.5
  #  22.38721139,      # 27
  #  23.71373706,      # 27.5
  #  25.11886432,      # 28
  #  26.6072506,       # 28.5
  #  28.18382931,      # 29
  #  29.85382619,      # 29.5
  #  31.6227766,       # 30 dB
  #  33.49654392,      # 30.5
  #  35.48133892,      # 31
  #  37.58374043,      # 31.5
  #  39.81071706,      # 32
  #  42.16965034,      # 32.5
  #  44.66835922,      # 33
  #  47.3151259,       # 33.5
  #  50.11872336,      # 34
  #  53.08844442,      # 34.5
  #  56.23413252,      # 35
  #  59.56621435,      # 35.5
  #  63.09573445,      # 36
  #  66.83439176,      # 36.5
  #  70.79457844,      # 37
  #  74.98942093,      # 37.5
  #  79.43282347,      # 38
  #  84.13951416,      # 38.5
  #  89.12509381,      # 39
  #  94.40608763,      # 39.5
  #  100.0,            # 40 dB
  #  105.9253725,      # 40.5
  #  112.2018454,      # 41
  #  118.8502227,      # 41.5
  #  125.8925412,      # 42
  #  133.3521432,      # 42.5
  #  141.2537545,      # 43
  #  149.6235656,      # 43.5
  #  158.4893192,      # 44
  #  167.8804018,      # 44.5
  #  177.827941,       # 45
  #  188.3649089,      # 45.5
  #  199.5262315,      # 46
  #  211.348904,       # 46.5
  #  223.8721139,      # 47
  #  237.1373706,      # 47.5
  #  251.1886432,      # 48
  #  266.072506,       # 48.5
  #  281.8382931,      # 49
  #  298.5382619,      # 49.5
  #  316.227766,       # 50 dB
  #  334.9654392,      # 50.5
  #  354.8133892,      # 51
  #  375.8374043,      # 51.5
  #  398.1071706,      # 52
  #  421.6965034,      # 52.5
  #  446.6835922,      # 53
  #  473.151259,       # 53.5
  #  501.1872336,      # 54
  #  530.8844442,      # 54.5
  #  562.3413252,      # 55
  #  595.6621435,      # 55.5
  #  630.9573445,      # 56
  #  668.3439176,      # 56.5
  #  707.9457844,      # 57
  #  749.8942093,      # 57.5
  #  794.3282347,      # 58
  #  841.3951416,      # 58.5
  #  891.2509381,      # 59
  #  944.0608763,      # 59.5
  #  1000.0,           # 60 dB
  #  1059.253725,      # 60.5
  #  1122.018454,      # 61
  #  1188.502227,      # 61.5
  #  1258.925412,      # 62
  #  1333.521432,      # 62.5
  #  1412.537545,      # 63
  #  1496.235656,      # 63.5
  #  1584.893192,      # 64
  #  1678.804018,      # 64.5
  #  1778.27941,       # 65
  #  1883.649089,      # 65.5
  #  1995.262315,      # 66
  #  2113.48904,       # 66.5
  #  2238.721139,      # 67
  #  2371.373706,      # 67.5
  #  2511.886432,      # 68
  #  2660.72506,       # 68.5
  #  2818.382931,      # 69
  #  2985.382619,      # 69.5
  #  3162.27766,       # 70 dB
  #  3349.654392,      # 70.5
  #  3548.133892,      # 71
  #  3758.374043,      # 71.5
  #  3981.071706,      # 72
  #]
  #
  #def self.db_to_linear db
  #  raise ArgumentError, "#{db} db is not between -#{MAX_DB} and #{MAX_DB}" unless db.between(-MAX_DB, MAX_DB)
  #  db_half_step = (dB * 2.0).to_i
  #
  #  if(db_half_step >= 0)
  #    linear = DB_TO_SCALAR_TABLE[db_half_step]
  #  elsif
  #    linear = DB_TO_SCALAR_TABLE[-db_half_step]
  #    scalar = 1.0 / scalar
  #  end
  #
  #  return scalar
  #end

  MAX_DB_ABS = 6000.0

  def self.db_to_linear db
    db_abs = db.abs
    raise ArgumentError, "|db| is #{db_abs}, which is greater than the allowed #{MAX_DB_ABS}" if db_abs > MAX_DB_ABS
    return 10.0**(db / 20.0)
  end
  
  def self.linear_to_db linear
    raise ArgumentError, "linear value #{linear} is less than or equal to 0.0" if linear <= 0.0
    return 20.0 * Math::log10(linear)
  end

end
end