przemek83 / ascii-decode

Simple decoder creating according to rules ascii chars from string of digits.

Ascii decoder

Simple decoder creating, according to given rules, ascii chars from string of digits.

Table of content

• Problem description
• Getting Started
  • Prerequisites
  • Building
• Built with
• Usage
• Testing
• License

Problem description

Decode string of digits into ascii string with following rules:

• Each 4 consecutive digits encodes 1 ascii char.
• Digit 1 and 3 of 4 digits sequence need to be concatenated to get first number.
• Digit 2 and 4 of 4 digits sequence need to be concatenated to get second number.
• Sum of first and second number is an ascii code encoded by 4 digit sequence.

Decoding example:
On input is given string 24746211151814964359. String need to be split into 2474 6211 1518 1496 4359. From each 4 digits group we extract first and second number also calculating sums:

4 digits sequence	first number	second number	sum (first + second)
2474	27	44	71
6211	61	21	82
1518	11	58	69
1496	19	46	65
4359	45	39	84

ASCII codes (sums) will give encoded string GREAT (71 = G, 82 = R, ...).

Input:
In each line encoded ascii chars as sequences of 4 digits per sign.

Output:
Decoded ascii string.

Getting Started

This section describes briefly how to setup environment and build project.

Prerequisites

C++ compiler with C++17 support as a minimum and CMake 3.8+. Additionally Git tool for downloading Google Test library as it is needed by test subproject.

Building

Recommended:
Use Cmake directly or your favorite IDE supporting CMake projects.

Alternative:
Use bare compiler for building project binary:

$ g++ -Wall -std=c++17 -O3 -c *.cpp
$ g++ -Wall -std=c++17 -O3 -o ascii-decode *.o

Built with

Tool	Windows 10	Lubuntu 20.04
GCC	7.3.0	9.3.0
Cmake	3.14	3.17
Git	2.20	2.25
QtCreator	4.12.0	4.13.0

Usage

Application expects on std in strings containing encoded ascii chars in form of 4 digit sequences.
Example input:

24746211151814964359
2244

Examples of usage:

1. Pass example file named testFile.txt from project repo:

   $ ./ascii-decode < testFile.txt
   GREAT
   0
   

2. Use binary directly:

   $ ./ascii-decode
   24746211151814964359
   GREAT
   2244
   0

3. Pipe input:

   $ cat testFile.txt | ./ascii-decode
   GREAT
   0

Testing

Project contains test subproject based on Goggle Test framework. Compile testing subproject and launch tests via IDE or directly from console.
Example run:

$ ./ascii-decode-test.exe
(...)
[==========] Running 2 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 2 tests from AsciiDecode
[ RUN      ] AsciiDecode.decodePositive
[       OK ] AsciiDecode.decodePositive (0 ms)
[ RUN      ] AsciiDecode.decodeNegative
[       OK ] AsciiDecode.decodeNegative (0 ms)
[----------] 2 tests from AsciiDecode (0 ms total)

[----------] Global test environment tear-down
[==========] 2 tests from 1 test suite ran. (0 ms total)
[  PASSED  ] 2 tests.

License

Project is distributed under the MIT License. See LICENSE for more information.