Base62

gistfile1.rb

class Base62
    @@ranges = [
        ('0'..'9'),
        ('a'..'z'),
        ('A'..'Z')
        ]
    @@base = nil
    @@offsets = nil

    def self.to_s(number)
        if @@base.nil?
            @@base = self.calculate_base
        end
        string = ""
        while number > (@@base - 1)
            place = number % @@base
            string = self.lookup(place) + string
            number = number / @@base    
        end

        self.lookup(number) + string
    end

    def self.to_i(string)
        if @@base.nil?
            @@base = self.calculate_base
        end
        number = 0
        i = string.length - 1
        string.each_byte do |c|
            c = c.chr
            @@ranges.each_index do |j|
                range = @@ranges[j]
                if range.member? c
                    number += (c[0] - range.to_a.first[0] + @@offsets[j]) * (@@base ** i)
                    break
                end
            end
            i -= 1
        end
        number
    end

    def self.lookup(place)
        string = ""
        if @@base.nil?
            @@base = self.calculate_base
        end
        (0..(@@ranges.length-1)).each do |i|
            range_array = @@ranges[i].to_a
            start = 0 + @@offsets[i]
            stop = range_array.length - 1 + @@offsets[i]
            if (start..stop).member? place
                string = range_array[place - @@offsets[i]]
                break
            end 
        end
        string
    end

    def self.next_integer(integer)
        integer + 1
    end

    def self.calculate_base
        i = 0
        @@offsets = []
        @@ranges.each do |range|
            @@offsets << i
            i += range.to_a.length
        end
        i
    end
end