X-Git-Url: https://git.openstreetmap.org/rails.git/blobdiff_plain/64030a40ac98f5420e77cdb672dd428f22bbffd4..ef7f3d800cbdd49b692df10d312e5fd880e2e938:/lib/short_link.rb diff --git a/lib/short_link.rb b/lib/short_link.rb index 045883d57..0d8f21cad 100644 --- a/lib/short_link.rb +++ b/lib/short_link.rb @@ -5,14 +5,13 @@ # Each character encodes 3 bits of x and 3 of y, so there are extra characters # tacked on the end to make the zoom levels "work". module ShortLink - # array of 64 chars to encode 6 bits. this is almost like base64 encoding, but - # the symbolic chars are different, as base64's + and / aren't very + # the symbolic chars are different, as base64's + and / aren't very # URL-friendly. - ARRAY = ('A'..'Z').to_a + ('a'..'z').to_a + ('0'..'9').to_a + ['_','~'] + ARRAY = ('A'..'Z').to_a + ('a'..'z').to_a + ('0'..'9').to_a + ['_', '~'] ## - # Given a string encoding a location, returns the [lon, lat, z] tuple of that + # Given a string encoding a location, returns the [lon, lat, z] tuple of that # location. def self.decode(str) x = 0 @@ -23,7 +22,7 @@ module ShortLink # keep support for old shortlinks which use the @ character, now # replaced by the ~ character because twitter is horribly broken # and we can't have that. - str.gsub!("@","~") + str.gsub!("@", "~") str.each_char do |c| t = ARRAY.index c @@ -31,8 +30,8 @@ module ShortLink z_offset -= 1 else 3.times do - x <<= 1; x = x | 1 unless (t & 32).zero?; t <<= 1 - y <<= 1; y = y | 1 unless (t & 32).zero?; t <<= 1 + x <<= 1; x |= 1 unless (t & 32).zero?; t <<= 1 + y <<= 1; y |= 1 unless (t & 32).zero?; t <<= 1 end z += 3 end @@ -42,20 +41,20 @@ module ShortLink y <<= (32 - z) # project the parameters back to their coordinate ranges. - [(x * 360.0 / 2**32) - 180.0, - (y * 180.0 / 2**32) - 90.0, + [(x * 360.0 / 2**32) - 180.0, + (y * 180.0 / 2**32) - 90.0, z - 8 - (z_offset % 3)] end ## # given a location and zoom, return a short string representing it. def self.encode(lon, lat, z) - code = interleave_bits(((lon + 180.0) * 2**32 / 360.0).to_i, + code = interleave_bits(((lon + 180.0) * 2**32 / 360.0).to_i, ((lat + 90.0) * 2**32 / 180.0).to_i) str = "" # add eight to the zoom level, which approximates an accuracy of # one pixel in a tile. - ((z + 8)/3.0).ceil.times do |i| + ((z + 8) / 3.0).ceil.times do |i| digit = (code >> (58 - 6 * i)) & 0x3f str << ARRAY[digit] end @@ -63,12 +62,12 @@ module ShortLink # partial zoom levels (characters themselves have a granularity # of 3 zoom levels). ((z + 8) % 3).times { str << "-" } - - return str + + str end private - + ## # interleaves the bits of two 32-bit numbers. the result is known # as a Morton code. @@ -80,5 +79,4 @@ module ShortLink end c end - end