From d8e89b0727411f97f7c9e44b0c4b2d1b8af61810 Mon Sep 17 00:00:00 2001 From: Kevin Shekleton Date: Fri, 4 Jan 2013 02:12:56 -0600 Subject: [PATCH] Initial commit --- .rvmrc | 1 + Gemfile | 4 + LICENSE | 202 +++++++++++++++++++++++++++++++++++++++++++++++++ README.md | 91 ++++++++++++++++++++++ mm2pwd.rb | 144 +++++++++++++++++++++++++++++++++++ mm2pwd_spec.rb | 97 ++++++++++++++++++++++++ 6 files changed, 539 insertions(+) create mode 100644 .rvmrc create mode 100644 Gemfile create mode 100644 LICENSE create mode 100644 README.md create mode 100755 mm2pwd.rb create mode 100644 mm2pwd_spec.rb diff --git a/.rvmrc b/.rvmrc new file mode 100644 index 0000000..eda19b1 --- /dev/null +++ b/.rvmrc @@ -0,0 +1 @@ +rvm use 1.9.3@mm2pwd --create \ No newline at end of file diff --git a/Gemfile b/Gemfile new file mode 100644 index 0000000..52c3f01 --- /dev/null +++ b/Gemfile @@ -0,0 +1,4 @@ +source :rubygems + +gem 'rake', '10.0.3' +gem 'rspec', '2.12.0' diff --git a/LICENSE b/LICENSE new file mode 100644 index 0000000..608f068 --- /dev/null +++ b/LICENSE @@ -0,0 +1,202 @@ + + Apache License + Version 2.0, January 2004 + http://www.apache.org/licenses/ + + TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION + + 1. 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We also recommend that a + file or class name and description of purpose be included on the + same "printed page" as the copyright notice for easier + identification within third-party archives. + + Copyright 2012 Kevin Shekleton + + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. \ No newline at end of file diff --git a/README.md b/README.md new file mode 100644 index 0000000..43a59ca --- /dev/null +++ b/README.md @@ -0,0 +1,91 @@ +# Mega Man 2 Password Generator # + +## Overview ## + +Mega Man 2, like many games of its era, utilized a password system in order to continue your progress between game sessions. +This removed the need for a battery in the game catridge and allowed gamers to share passwords (and thus progress) with others. + +In Mega Man 2, the password is represented as a 5x5 grid in which the columns are labled 1-5 and the rows A-E. Each password +is comprised of 9 cells which are 'set', indicated by a red dot. + +Thus, a password can be communicated as A5, B2, B4, C1, C3, C5, D4, D5, E2. + +Put another way, this 5x5 grid represents 25 bits in which a password always has exactly 9 bits set. Using this representation, +the password algorithm can be expressed succinctly in terms of these bits and using basic bitwise operations. + +In the 25 bits, there are 5 words of 5 bits each where each word represents a row in the grid. The entire 25-bit password +is thus comprised of the words A E D C B (using little endian). So, the first word (lowest 5 bits) are the 5 bits of the row B +and the last word (bits 20-25) are the 6 bits of row A. + +### Words 1-4 (bits 1-20) ### + +A Mega Man 2 password has exactly 9 bits set. 8 of these bits represent the alive/defeated status of each of the 8 bosses in +the game. The follow table illustrates the bit values for the alive/defeated status for each of the 8 bosses. + +Boss | Alive | Defeated +---------- | ----- | -------- +Bubble Man | C3 | D1 +Air Man | D2 | E3 +Quick Man | C4 | B4 +Wood Man | B5 | D3 +Crash Man | E2 | C5 +Flash Man | E4 | C1 +Metal Man | E1 | E5 +Heat Man | D5 | B2 + +Thus, if both Bubble Man and Air Man were defeated but all other bosses were still alive, this is represented as the following +bits (1-20) 01111 10001 01000 10000. + +Row | E | D | C | B +---- | ----- | ----- | ----- | ----- +Word | 01111 | 10001 | 01000 | 10000 + +### E-Tank Word (bits 21-25) ### + +The last bit (9th) represents the number of E-Tanks Mega Man has. This is stored in the 5th word (row A) and represents bits +21-25, the most significant bits of the password. Mega Man can have between 0-4 E-Tanks and this is encoded simply per the bit +position in this last word. Thus, if Mega Man has 0 E-Tanks the word is 00001, 1 E-Tank is 00010, 2 E-Tanks is 00100, and so +forth. Unlike the other words, the 5th word (row A) will thus only ever have a single bit set. + +The E-Tank word (row A) is important in that it encodes bits 1-20 by performing a rotate left operations on bits 1-20 by the +number of E-Tanks that Mega Man has. Thus, if Mega Man has 2 E-Tanks, bits 1-20 are rotated left by 2 positions. If Mega Man +has 0 E-Tanks, this is effectively a no-op. The table above illustrating the bits set for each of the 8 bosses represent the +bits prior to the rotate left operation. The bits of the E-Tank word are not included in the left rotation. + +## Algorithm ## + +The algorithm for calculating a password can be summarized as follows: + +1. Set the bits of the first 4 words (rows B, C, D, E) based on the table above (bits 1-20) +2. Rotate left bits 1-20 based on the number of E-Tanks +3. Add the E-Tank word (bits 21-25) as the most significant word of the password + +## Setup ## + +To run mm2pwd you will need [Ruby](http://www.ruby-lang.org/) installed. +mm2pwd has been tested with Ruby 1.9.3p362 which is the latest version as of this writing. + +## Running ## + +To run mm2pwd, simply open a terminal session in the root directory and execute the following command: + + $ ./mm2pwd.rb + +Without an modification, this will generate a password in which Mega Man has all 4 E-Tanks and has defeated all 8 bosses. If you +want to modify this, simply change the values in the initialize method. + +## License ## + +Copyright 2012 Kevin Shekleton + +Licensed under the Apache License, Version 2.0 (the "License"); +you may not use this file except in compliance with the License. +You may obtain a copy of the License at + +http://www.apache.org/licenses/LICENSE-2.0 + +Unless required by applicable law or agreed to in writing, software +distributed under the License is distributed on an "AS IS" BASIS, +WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +See the License for the specific language governing permissions and +limitations under the License. \ No newline at end of file diff --git a/mm2pwd.rb b/mm2pwd.rb new file mode 100755 index 0000000..6c0bab2 --- /dev/null +++ b/mm2pwd.rb @@ -0,0 +1,144 @@ +#!/usr/bin/env ruby +# coding: UTF-8 + +# Copyright 2013 Kevin Shekleton +# Licensed under the Apache License, Version 2.0 (the "License"); +# you may not use this file except in compliance with the License. +# You may obtain a copy of the License at +# +# http://www.apache.org/licenses/LICENSE-2.0 +# +# Unless required by applicable law or agreed to in writing, software +# distributed under the License is distributed on an "AS IS" BASIS, +# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +# See the License for the specific language governing permissions and +# limitations under the License. + +class Mm2Pwd + attr_accessor :e_tanks, :bubble_man, :air_man, :quick_man, :wood_man, :crash_man, :flash_man, :metal_man, :heat_man + + # Initializes an instance of this class with the desired password properties. + # Change the instance variable values here to change the generated password. + # + # Returns an instance of Mm2Pwd. + def initialize + @e_tanks = 4 + + # alive (true) ; defeated (false) + @bubble_man = false + @air_man = false + @quick_man = false + @wood_man = false + @crash_man = false + @flash_man = false + @metal_man = false + @heat_man = false + end + + # Public: Generates the password coordinates suitable for input in Mega Man 2. + # + # This method will also print the 25-bit password and coordinates to the console. + # + # Returns the Array of password coordinates (Strings) for this class. + def generate + bits = generate_password_bits + puts bits.to_s(2) + + coordinates = bits_to_coordinates(bits) + puts coordinates.inspect + + coordinates + end + + private + + # Internal: Generates the password bits (1-25). + # + # Returns the 25-bit password (Integer) for this class. + def generate_password_bits + # row E D C B + bits = 0b00000_00000_00000_00000 + + # Determine the boss bits (bits 1-20) + bits |= @bubble_man ? 0b00000_00000_00100_00000 : 0b00000_00001_00000_00000 # C3 / D1 + bits |= @air_man ? 0b00000_00010_00000_00000 : 0b00100_00000_00000_00000 # D2 / E3 + bits |= @quick_man ? 0b00000_00000_01000_00000 : 0b00000_00000_00000_01000 # C4 / B4 + bits |= @wood_man ? 0b00000_00000_00000_10000 : 0b00000_00100_00000_00000 # B5 / D3 + bits |= @crash_man ? 0b00010_00000_00000_00000 : 0b00000_00000_10000_00000 # E2 / C5 + bits |= @flash_man ? 0b01000_00000_00000_00000 : 0b00000_00000_00001_00000 # E4 / C1 + bits |= @metal_man ? 0b00001_00000_00000_00000 : 0b10000_00000_00000_00000 # E1 / E5 + bits |= @heat_man ? 0b00000_10000_00000_00000 : 0b00000_00000_00000_00010 # D5 / B2 + + # Rotate bits left based on the number of E-Tanks + bits = rotate_left(bits, @e_tanks) + + # Set the E-Tank bits + bits |= (1 << 20 + @e_tanks) + + bits + end + + # Internal: Given the following bits, returns the coordinates of the set bits. + # + # bits - [Integer] The 25-bit password. + # + # Examples + # + # bits_to_coordinates(0b10000_01000_00100_00010_00011) + # # => ['A5', 'B1', 'B2', 'C2', 'D3', 'E4'] + # + # Returns the coordinates of the set bits expressed in terms of the grid. + def bits_to_coordinates(bits) + a = (bits & 0b11111_00000_00000_00000_00000) >> 20 + e = (bits & 0b11111_00000_00000_00000) >> 15 + d = (bits & 0b11111_00000_00000) >> 10 + c = (bits & 0b11111_00000) >> 5 + b = bits & 0b11111 + + coordinates = [] + + coordinates.push(*word_to_coordinates(:A, a)) + coordinates.push(*word_to_coordinates(:B, b)) + coordinates.push(*word_to_coordinates(:C, c)) + coordinates.push(*word_to_coordinates(:D, d)) + coordinates.push(*word_to_coordinates(:E, e)) + end + + # Internal: Given the following word, returns the coordinates of the set bits. + # + # row_name - [Symbol] The name of the row being evaluated + # word - [Integer] The word (5 bits) being evaluated + # + # Examples + # + # word_to_coordinates(:B, 0b01101) + # # => ['B1', 'B3', 'B4'] + # + # Returns a non-nil Array of the coordinates that are 'set'. + def word_to_coordinates(row_name, word) + coordinates = [] + 5.times do |i| + coordinates << "#{row_name}#{i+1}" if (word & (1 << i)) > 0 + end + + coordinates + end + + # Internal: Rotate the bits of the given value left by the given shift + # Note that a word size of 20 is assumed + # + # value - [Integer] The bit value to shift + # shift - [Integer] The number of left shifts + # + # Examples + # + # rotate_left(0b01010_00000_00000_00000, 2) + # # => 0b01000_00000_00000_00001 + # + # Returns the given value left shifted by the given shift. + def rotate_left(value, shift) + ((value << shift) | (value >> (20 - shift))) & 0xFFFFF + end +end + +Mm2Pwd.new.generate \ No newline at end of file diff --git a/mm2pwd_spec.rb b/mm2pwd_spec.rb new file mode 100644 index 0000000..dafe77b --- /dev/null +++ b/mm2pwd_spec.rb @@ -0,0 +1,97 @@ +# coding: UTF-8 + +# Copyright 2013 Kevin Shekleton +# Licensed under the Apache License, Version 2.0 (the "License"); +# you may not use this file except in compliance with the License. +# You may obtain a copy of the License at +# +# http://www.apache.org/licenses/LICENSE-2.0 +# +# Unless required by applicable law or agreed to in writing, software +# distributed under the License is distributed on an "AS IS" BASIS, +# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +# See the License for the specific language governing permissions and +# limitations under the License. + +require './mm2pwd' + +describe Mm2Pwd do + let(:m) { Mm2Pwd.new } + + context '#initialize' do + it 'returns a non-nill instance' do + m.should be_an_instance_of(Mm2Pwd) + end + end + + context '#generate' do + it 'returns the correct coordinates for 4 E-Tanks and all 8 bosses defeated' do + expect(m.generate).to eq(['A5', 'B2', 'B4', 'C1', 'C3', 'C5', 'D4', 'D5', 'E2']) + end + + it 'returns the correct coordinates for 0 E-Tanks and all 8 bosses defeated' do + m.e_tanks = 0 + expect(m.generate).to eq(['A1', 'B2', 'B4', 'C1', 'C5', 'D1', 'D3', 'E3', 'E5']) + end + end + + context '#generate_password_bits' do + it 'returns the correct bits for 4 E-Tanks and all 8 bosses defeated' do + expect(m.send(:generate_password_bits)).to eq(0b10000_00010_11000_10101_01010) + end + end + + context '#bits_to_coordinates' do + it 'returns no coordinates if all bits are unset' do + expect(m.send(:bits_to_coordinates, 0b00000_00000_00000_00000_00000)).to eq([]) + end + + it 'correctly pulls the 1st word (B)' do + expect(m.send(:bits_to_coordinates, 0b00000_00000_00000_00000_01110)).to eq(['B2', 'B3', 'B4']) + end + + it 'correctly pulls the 2nd word (C)' do + expect(m.send(:bits_to_coordinates, 0b00000_00000_00000_11011_00000)).to eq(['C1', 'C2', 'C4', 'C5']) + end + + it 'correctly pulls the 3rd word (D)' do + expect(m.send(:bits_to_coordinates, 0b00000_00000_00110_00000_00000)).to eq(['D2', 'D3']) + end + + it 'correctly pulls the 4th word (E)' do + expect(m.send(:bits_to_coordinates, 0b00000_01001_00000_00000_00000)).to eq(['E1', 'E4']) + end + + it 'correctly pulls the 5th word (A)' do + expect(m.send(:bits_to_coordinates, 0b10010_00000_00000_00000_00000)).to eq(['A2', 'A5']) + end + end + + context '#word_to_coordinates' do + it 'correctly identifies the set bits when all bits are set' do + expect(m.send(:word_to_coordinates, :A, 0b11111)).to eq(['A1', 'A2', 'A3', 'A4', 'A5']) + end + + it 'correctly identifies the set bits when all bits are unset' do + expect(m.send(:word_to_coordinates, :A, 0b00000)).to eq([]) + end + + it 'correctly identifies the set bits when there are a mixture of set and unset bits' do + expect(m.send(:word_to_coordinates, :A, 0b01010)).to eq(['A2', 'A4']) + end + end + + context '#rotate_left' do + it 'correctly does not rotation if the shift is 0' do + expect(m.send(:rotate_left, 0b10000_00000_00000_00000, 0)).to eq(0b10000_00000_00000_00000) + end + + it 'correctly roates and wraps values for a shift of 1' do + expect(m.send(:rotate_left, 0b10100_00000_00000_00000, 1)).to eq(0b01000_00000_00000_00001) + end + + it 'correctly roates and wraps values for a shift of 2' do + expect(m.send(:rotate_left, 0b10100_00000_00000_00000, 2)).to eq(0b10000_00000_00000_00010) + end + end +end \ No newline at end of file