Christian Burns Developer Challenge

README.md

@@ -1,4 +1,12 @@
-# Captivation Software Developer Challenge
+# Captivation Software Developer Challenge - Christian Burns
+
+## Installation Instructions
+
+> The minimum required versions of [Python](https://www.python.org/) are 2.6 and 3.0.
+
+You can check which version of Python you have installed via `python --version` or `python3 --version`.
+
+This application can then run via `python /path/to/submission.py` or `python3 /path/to/submission.py` correspondingly.
 
 ## Your Task
 Develop an application that:

submission.py

@@ -0,0 +1,61 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+"""
+Captivation Software Developer Challenge Submission
+
+This application reads a stream of 1's and 0's from STDIN and decodes the input
+characters into single zero-padded ASCII text. When the application finds the
+word "CAPTIVATION" within the input stream, it will print out the next one hundred
+decoded characters following "CAPTIVATION" to STDOUT. This process repeats forever.
+
+Author: Christian Burns
+Date:   June 30, 2021
+See:    https://github.com/captivationsoftware/DeveloperChallenge
+"""
+
+import sys
+from collections import deque
+
+preamble_string = 'CAPTIVATION'  # Keyword to search for
+num_characters_to_print = 100    # Number of characters to print after keyword
+
+# Converting the preamble_string into its binary equivalent
+preamble_binary = ''.join(format(ord(c), '08b') for c in preamble_string)
+preamble_deque = deque(preamble_binary)
+max_input_len = len(preamble_binary)
+
+# --- Decode input stream from STDIN --- #
+
+while True:
+
+    # --- Search for the preamble string --- #
+
+    rolling_input = None    # Rolling queue of the last {max_input_len} binary values
+    preamble_found = False  # True when rolling_input matches preamble_deque
+
+    while not preamble_found:
+        # Bulk read/insert the next {max_input_len} characters to avoid wasting
+        #   time comparing queues prior to the queues reaching equal lengths.
+        if rolling_input is None:
+            characters = sys.stdin.read(max_input_len)
+            rolling_input = deque(characters, maxlen=max_input_len)
+
+        # Since the bits for the preamble message are not guaranteed to be well-aligned,
+        #   we must iterate through STDIN one character at a time. For this reason, we
+        #   utilize Python's builtin collections.deque list which has a time complexity
+        #   of O(1) for inserting and removing items at either end to improve performance.
+        else:
+            character = sys.stdin.read(1)
+            rolling_input.append(character)
+
+        # We compare the rolling_input to a predefined preamble_deque
+        #   to avoid unnecessary string manipulation/conversion.
+        if rolling_input == preamble_deque:
+            preamble_found = True
+
+    # --- Decode and print the next {num_characters_to_print} characters --- #
+
+    for _ in range(num_characters_to_print):
+        input_buffer = sys.stdin.read(8)     # Each character is represented by 8 bits
+        ascii_number = int(input_buffer, 2)  # Converting the bits into an ascii value
+        sys.stdout.write(chr(ascii_number))  # Converting the ascii value to character