Class: Proxihash

Inherits:
Object
  • Object
show all
Defined in:
lib/proxihash.rb,
lib/proxihash/version.rb

Constant Summary collapse

VERSION = 
[0, 0, 1]

Class Attribute Summary collapse

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(value, num_bits) ⇒ Proxihash

Returns a new instance of Proxihash.



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# File 'lib/proxihash.rb', line 4

def initialize(value, num_bits)
  @value = value
  @num_bits = num_bits
  num_bits.odd? or
    raise ArgumentError, "bitlength must be odd"
  value < 1 << num_bits or
    raise ArgumentError, "value too large for #{num_bits} bits"
end

Class Attribute Details

.angular_units ⇒ Object

Returns the value of attribute angular_units.



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# File 'lib/proxihash.rb', line 52

def angular_units
  @angular_units
end

.max_lat ⇒ Object (readonly)

Returns the value of attribute max_lat.



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# File 'lib/proxihash.rb', line 53

def max_lat
  @max_lat
end

.max_lng ⇒ Object (readonly)

Returns the value of attribute max_lng.



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# File 'lib/proxihash.rb', line 53

def max_lng
  @max_lng
end

.min_lat ⇒ Object (readonly)

Returns the value of attribute min_lat.



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# File 'lib/proxihash.rb', line 53

def min_lat
  @min_lat
end

.min_lng ⇒ Object (readonly)

Returns the value of attribute min_lng.



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# File 'lib/proxihash.rb', line 53

def min_lng
  @min_lng
end

.radius ⇒ Object

Returns the value of attribute radius.



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# File 'lib/proxihash.rb', line 52

def radius
  @radius
end

Instance Attribute Details

#num_bits ⇒ Object (readonly)

Returns the value of attribute num_bits.



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# File 'lib/proxihash.rb', line 13

def num_bits
  @num_bits
end

#value ⇒ Object (readonly)

Returns the value of attribute value.



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# File 'lib/proxihash.rb', line 13

def value
  @value
end

Class Method Details

.encode(lat, lng, num_bits = 31) ⇒ Object 



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# File 'lib/proxihash.rb', line 55

def encode(lat, lng, num_bits=31)
  lat = lat.to_f
  lng = lng.to_f

  value = 0

  lat0 = min_lat
  lat1 = max_lat
  lng0 = min_lng
  lng1 = max_lng

  (num_bits - 1).downto(0) do |i|
    if i.odd?
      mid = 0.5 * (lat0 + lat1)
      if lat > mid
        value |= (1 << i)
        lat0 = mid
      else
        lat1 = mid
      end
    else
      mid = 0.5 * (lng0 + lng1)
      if lng > mid
        value |= (1 << i)
        lng0 = mid
      else
        lng1 = mid
      end
    end
  end

  new(value, num_bits)
end

.search_tiles(lat, lng, distance, options = {}) ⇒ Object 



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# File 'lib/proxihash.rb', line 89

def search_tiles(lat, lng, distance, options={})
  lat = lat.to_f
  lng = lng.to_f
  bits = 2*lng_bits(lat, distance.to_f) - 1

  if (min_bits = options[:min_bits]) && bits < min_bits
    return nil
  elsif (max_bits = options[:max_bits]) && bits > max_bits
    # TODO: avoid unnecessary neighboring tiles
    bits = max_bits
  end

  # TODO: can use the next 2 bits to determine quadrant instead
  center = encode(lat, lng, bits)
  tile_lat, tile_lng = center.decode
  dlat = lat < tile_lat ? -1 : 1
  dlng = lng < tile_lng ? -1 : 1
  [
    center,
    center.neighbor(0   , dlng),
    center.neighbor(dlat, dlng),
    center.neighbor(dlat,    0),
  ]
rescue PoleWrapException
  nil
end

Instance Method Details

#==(other) ⇒ Object Also known as: eql? 



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# File 'lib/proxihash.rb', line 188

def ==(other)
  other.is_a?(Proxihash) && value == other.value && num_bits == other.num_bits
end

#decode ⇒ Object 



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# File 'lib/proxihash.rb', line 133

def decode
  lat0, lat1, lng0, lng1 = tile
  [0.5 * (lat0 + lat1), 0.5 * (lng0 + lng1)]
end

#east ⇒ Object 



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# File 'lib/proxihash.rb', line 180

def east
  neighbor(0, 1)
end

#hash ⇒ Object 



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# File 'lib/proxihash.rb', line 192

def hash
  value.hash ^ num_bits
end

#id ⇒ Object 



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# File 'lib/proxihash.rb', line 15

def id
  value | 1 << num_bits
end

#inspect ⇒ Object 



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# File 'lib/proxihash.rb', line 197

def inspect
  "Proxihash[#{value.to_s(2).rjust(num_bits, '0')}]"
end

#neighbor(dlat, dlng) ⇒ Object 



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# File 'lib/proxihash.rb', line 165

def neighbor(dlat, dlng)
  value = self.value
  value = bump(value, 1, dlat, false) unless dlat.zero?
  value = bump(value, 0, dlng, true ) unless dlng.zero?
  self.class.new(value, num_bits)
end

#north ⇒ Object 



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# File 'lib/proxihash.rb', line 172

def north
  neighbor(1, 0)
end

#south ⇒ Object 



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# File 'lib/proxihash.rb', line 176

def south
  neighbor(-1, 0)
end

#tile ⇒ Object 



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# File 'lib/proxihash.rb', line 138

def tile
  lat0 = min_lat
  lat1 = max_lat
  lng0 = min_lng
  lng1 = max_lng

  (num_bits - 1).downto(0) do |i|
    if i.odd?
      mid = 0.5 * (lat0 + lat1)
      if value[i] == 1
        lat0 = mid
      else
        lat1 = mid
      end
    else
      mid = 0.5 * (lng0 + lng1)
      if value[i] == 1
        lng0 = mid
      else
        lng1 = mid
      end
    end
  end

  [lat0, lat1, lng0, lng1]
end

#west ⇒ Object 



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# File 'lib/proxihash.rb', line 184

def west
  neighbor(0, -1)
end