added base36.rb Ruby library

git-svn-id: http://biopieces.googlecode.com/svn/trunk@1265 74ccb610-7750-0410-82ae-013aeee3265d

diff --git a/code_ruby/Maasha/lib/base36.rb b/code_ruby/Maasha/lib/base36.rb
new file mode 100644 (file)
index 0000000..9af7a3f
--- /dev/null
+++ b/code_ruby/Maasha/lib/base36.rb
@@ -0,0 +1,70 @@
+# Copyright (C) 2011 Martin A. Hansen.
+
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+
+# http://www.gnu.org/copyleft/gpl.html
+
+# >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
+
+# This software is part of the Biopieces framework (www.biopieces.org).
+
+# >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
+
+# Error class for all exceptions to do with Base36.
+class Base36Error < StandardError; end
+
+ALPH   = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
+BASE36 = 36
+
+# Class containing methods to encode and decade Base 36.
+# Note that the ALPH is [alph + num] and not [num + alph]
+# which prevents us from simply using .to_i(36) and .to_s(36).
+#
+# http://en.wikipedia.org/wiki/Base_36
+class Base36
+  # Method that encodes an integer into a base36 string
+  # that is returned.
+  def self.encode(num)
+    raise Base36Error unless num.is_a? Fixnum
+
+    base36 = ""
+
+    while num > 0
+      base36 << ALPH[(num % BASE36)]
+      num /= BASE36
+    end
+
+    base36 << ALPH[0] if num == 0
+
+    base36.reverse
+  end
+
+  # Method that decodes a base36 string and returns an integer.
+  def self.decode(base36)
+    raise Base36Error if base36.empty?
+
+    result = 0
+    pos    = 0
+
+    base36.upcase.reverse.each_char do |char|
+      result += ALPH.index(char) * (BASE36 ** pos)
+      pos    += 1
+    end
+
+    return result;
+  end
+end
+
+__END__

diff --git a/code_ruby/Maasha/test/test_base36.rb b/code_ruby/Maasha/test/test_base36.rb
new file mode 100755 (executable)
index 0000000..c966900
--- /dev/null
+++ b/code_ruby/Maasha/test/test_base36.rb
@@ -0,0 +1,48 @@
+#!/usr/bin/env ruby
+$:.unshift File.join(File.dirname(__FILE__),'..','lib')
+
+# Copyright (C) 2011 Martin A. Hansen.
+
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+
+# http://www.gnu.org/copyleft/gpl.html
+
+# >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
+
+# This software is part of the Biopieces framework (www.biopieces.org).
+
+# >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
+
+require 'test/unit'
+require 'base36'
+require 'pp'
+
+class Base36Test < Test::Unit::TestCase
+  def test_Base36_encode_with_non_fixnum_value_raises
+    assert_raise(Base36Error) { Base36.encode("foo") }
+  end
+
+  def test_Base36_encode_returns_correctly
+    assert_equal("AWVHI", Base36.encode(1053908))
+  end
+
+  def test_Base36_decode_with_empty_value_raises
+    assert_raise(Base36Error) { Base36.decode("") }
+  end
+
+  def test_Base36_decode_returns_correctly
+    assert_equal(1053908, Base36.decode("AWVHI"))
+  end
+end