Module: GitFit::Geo::Polyline

Defined in:
lib/git_fit/geo/polyline.rb

Class Method Summary collapse

Class Method Details

.decode(str) ⇒ Object 



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# File 'lib/git_fit/geo/polyline.rb', line 6

def decode(str)
  return nil unless str && str.length > 0

  points = []
  index = 0
  lat = 0
  lng = 0

  while index < str.length
    shift = 0
    result = 0
    begin
      byte = str[index].ord - 63
      index += 1
      result |= (byte & 0x1f) << shift
      shift += 5
    end while byte >= 0x20

    dlat = (result & 1) != 0 ? ~(result >> 1) : (result >> 1)
    lat += dlat

    shift = 0
    result = 0
    begin
      byte = str[index].ord - 63
      index += 1
      result |= (byte & 0x1f) << shift
      shift += 5
    end while byte >= 0x20

    dlng = (result & 1) != 0 ? ~(result >> 1) : (result >> 1)
    lng += dlng

    points << [lat * 1e-5, lng * 1e-5]
  end

  points
end

.encode(points) ⇒ Object 



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# File 'lib/git_fit/geo/polyline.rb', line 45

def encode(points)
  result = ""
  plat = 0
  plng = 0

  points.each do |lat, lng|
    dlat = ((lat * 1e5).round - plat)
    dlng = ((lng * 1e5).round - plng)

    plat += dlat
    plng += dlng

    result += encode_number(dlat)
    result += encode_number(dlng)
  end

  result
end

.encode_number(num) ⇒ Object 



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# File 'lib/git_fit/geo/polyline.rb', line 64

def encode_number(num)
  num = num < 0 ? ~(num << 1) : (num << 1)
  result = ""

  while num >= 0x20
    result += ((0x20 | (num & 0x1f)) + 63).chr
    num >>= 5
  end

  result += (num + 63).chr
  result
end