From 08fe640cc61a7c587297e079a2d174534fab5ff3 Mon Sep 17 00:00:00 2001
From: mo khan <mo@mokhan.ca>
Date: Wed, 22 Jan 2025 14:42:53 -0700
Subject: Improve caesar cipher example in assignment 3

---
 3431709-assignment-3.pdf  | Bin 151500 -> 152826 bytes
 Makefile                  |   2 +-
 assignments/3-solution.md |   9 +++++++++
 assignments/3/caesar.rb   |  32 ++++++++++++++++++++++++--------
 4 files changed, 34 insertions(+), 9 deletions(-)

diff --git a/3431709-assignment-3.pdf b/3431709-assignment-3.pdf
index 3dc2ae8..5b01942 100644
Binary files a/3431709-assignment-3.pdf and b/3431709-assignment-3.pdf differ
diff --git a/Makefile b/Makefile
index e032858..8493d44 100644
--- a/Makefile
+++ b/Makefile
@@ -8,7 +8,7 @@ default: 3431709-assignment-1.pdf 3431709-assignment-2.pdf 3431709-assignment-3.
 3431709-assignment-2.pdf: assignments/2-solution.md
 	pandoc -f markdown -t pdf -o 3431709-assignment-2.pdf assignments/2-solution.md
 
-3431709-assignment-3.pdf: assignments/3-solution.md
+3431709-assignment-3.pdf: assignments/3-solution.md assignments/3/caesar.rb assignments/3/main.c assignments/3/main.s
 	pandoc -f markdown -t pdf --filter pandoc-include -o 3431709-assignment-3.pdf assignments/3-solution.md
 
 3431709-assignment-4.pdf: assignments/4-solution.md
diff --git a/assignments/3-solution.md b/assignments/3-solution.md
index b0a72a8..5101c79 100644
--- a/assignments/3-solution.md
+++ b/assignments/3-solution.md
@@ -8,11 +8,20 @@ Chapter 6:
 
 > 13. Write a complete assembly language program (including all necessary pseudo-ops) that reads in a series of integers, one at a time, and outputs the largest and smallest values. The input will consist of a list of integer values
 
+I wrote the following C code and then used the GNU C Compiler to convert the C
+code into Assembly code for my machine. Below is the C code, compiler command,
+and final assembly code.
+
 main.c
 ```c
 !include assignments/3/main.c
 ```
 
+bash
+```bash
+$ gcc -S -fverbose-asm -02 main.c
+```
+
 main.s
 ```assembly
 !include assignments/3/main.s
diff --git a/assignments/3/caesar.rb b/assignments/3/caesar.rb
index bc70f75..c7111e4 100644
--- a/assignments/3/caesar.rb
+++ b/assignments/3/caesar.rb
@@ -1,10 +1,26 @@
 #!/usr/bin/env ruby
 
-key = 5
-alphabet = ('A'..'Z').to_a
-cipher = alphabet.rotate(key)
-map = Hash[cipher.zip(alphabet)]
-map[' '] = ' '
-
-ciphertext = "RTAJ TZY FY IFBS"
-puts ciphertext.chars.map { |x| map[x] }.join
+PLAIN_ALPHABET = ('A'..'Z').to_a
+
+def cipher_alphabet_for(key)
+  PLAIN_ALPHABET.rotate(key)
+end
+
+def decode(ciphertext, key)
+  mapping = Hash[cipher_alphabet_for(key).zip(PLAIN_ALPHABET)]
+  ciphertext.chars.map { |x| mapping[x] || ' ' }.join
+end
+
+key = ENV.fetch("KEY", 5).to_i
+ciphertext = ENV.fetch("CIPHERTEXT", "RTAJ TZY FY IFBS")
+
+width = (PLAIN_ALPHABET.size*2)-1
+puts "# Caesar Cipher"
+puts ""
+puts "| --------------- | --------------------------------------------------- |"
+puts "| Plain Alphabet  | #{PLAIN_ALPHABET.join(",").ljust(width)} |"
+puts "| Cipher Alphabet | #{cipher_alphabet_for(key).join(",").ljust(width)} |"
+puts "| --------------- | --------------------------------------------------- |"
+puts "| Key             | #{key.to_s.ljust(width)} |"
+puts "| Ciphertext      | #{ciphertext.to_s.ljust(width)} |"
+puts "| Plaintext       | #{decode(ciphertext, key).to_s.ljust(width)} |"
-- 
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