Merge pull request #86 from google/drinckes-patch-2

ruby code length validation

Author: drinckes

ruby/lib/plus_codes.rb

@@ -9,6 +9,11 @@ module PlusCodes
   # The max number of characters can be placed before the separator.
   SEPARATOR_POSITION = 8
 
+  # Maxiumum code length using lat/lng pair encoding. The area of such a
+  # code is approximately 13x13 meters (at the equator), and should be suitable
+  # for identifying buildings. This excludes prefix and separator characters.
+  PAIR_CODE_LENGTH = 10
+
   # The character used to pad a code
   PADDING = '0'.freeze
 

ruby/lib/plus_codes/open_location_code.rb

@@ -41,7 +41,7 @@ def full?(code)
     # @param longitude [Numeric] a longitude in degrees
     # @param code_length [Integer] the number of characters in the code, this excludes the separator
     # @return [String] a plus+codes
-    def encode(latitude, longitude, code_length = 10)
+    def encode(latitude, longitude, code_length = PAIR_CODE_LENGTH)
       raise ArgumentError,
       "Invalid Open Location Code(Plus+Codes) length: #{code_length}" if invalid_length?(code_length)
 
@@ -83,7 +83,7 @@ def decode(code)
 
       digit = 0
       while digit < code.length
-        if digit < 10
+        if digit < PAIR_CODE_LENGTH
           lat_resolution /= 20
           lng_resolution /= 20
           south_latitude += lat_resolution * DECODE[code[digit].ord]
@@ -180,7 +180,7 @@ def narrow_region(digit, latitude, longitude)
       if digit == 0
         latitude /= 20
         longitude /= 20
-      elsif digit < 10
+      elsif digit < PAIR_CODE_LENGTH
         latitude *= 20
         longitude *= 20
       else
@@ -193,7 +193,7 @@ def narrow_region(digit, latitude, longitude)
     def build_code(digit_count, code, latitude, longitude)
       lat_digit = latitude.to_i
       lng_digit = longitude.to_i
-      if digit_count < 10
+      if digit_count < PAIR_CODE_LENGTH
         code << CODE_ALPHABET[lat_digit]
         code << CODE_ALPHABET[lng_digit]
         [digit_count + 2, latitude - lat_digit, longitude - lng_digit]
@@ -230,18 +230,18 @@ def valid_character?(code)
     end
 
     def invalid_length?(code_length)
-      code_length < 2 || (code_length < SEPARATOR_POSITION && code_length.odd?)
+      code_length < 2 || (code_length < PAIR_CODE_LENGTH && code_length.odd?)
     end
 
     def padded(code)
       code << PADDING * (SEPARATOR_POSITION - code.length) << SEPARATOR
     end
 
     def precision_by_length(code_length)
-      if code_length <= 10
+      if code_length <= PAIR_CODE_LENGTH
         precision = 20 ** ((code_length / -2).to_i + 2)
       else
-        precision = (20 ** -3) / (5 ** (code_length - 10))
+        precision = (20 ** -3) / (5 ** (code_length - PAIR_CODE_LENGTH))
       end
       precision.to_r
     end

ruby/test/plus_codes_test.rb

@@ -63,6 +63,9 @@ def test_exceptions
     assert_raise ArgumentError do
       @olc.encode(20, 30, 1)
     end
+    assert_raise ArgumentError do
+      @olc.encode(20, 30, 9)
+    end
     assert_raise ArgumentError do
       @olc.recover_nearest('9C3W9QCJ-2VX', 51.3708675, -1.217765625)
     end