Strings and Ciphers

This project explores four main areas: strings, system calls, caesar cipher, and substitution cipher. It provides both a C library and unit tests, making it a practical codebase designed for Linux environments. For more background on Linux environments and code I/O, see: Linux Operating Systems - rsiddiq.com.

Features

String helpers (get_str_length, copy_str, case conversion, find-first/last index)
Person and Group structs with basic operations
Caesar cipher (encrypt/decrypt)
General substitution cipher (encrypt/decrypt, key validation + inversion)
Unit tests with Criterion

Project Layout

StringsAndCiphers/
├─ .gitignore
├─ Makefile
├─ README.md
├─ unit_tests.c
├─ build/
│  └─ tests_runner
├─ src/
│  ├─ StringsAndCiphers.c
│  ├─ StringsAndCiphers.h
│  ├─ StringsAndCiphers.o
│  └─ log.h
├─ tests/
│  ├─ unittests_caesar.c
│  ├─ unittests_string.c
│  ├─ unittests_struct.c
│  └─ unittests_substitution.c
└─ .vscode/
   ├─ launch.json
   └─ tasks.json

Build Instructions

This project is intended for Linux systems and requires make, a C11 compiler, and Criterion.

Ubuntu/Debian

sudo apt-get install build-essential pkg-config make
# Criterion (Ubuntu 22.04+ has libcriterion-dev, else build from source)
sudo apt-get install libcriterion-dev

Alternative Environments

Windows: Use WSL (Windows Subsystem for Linux) to run a Linux environment with make and a C compiler.
macOS: Install Xcode command line tools (xcode-select --install) and Criterion via Homebrew (brew install criterion).

Docker: Build and test inside a Linux-based container for a consistent environment:

docker run --rm -it -v $(pwd):/app -w /app gcc:latest bash
apt-get update && apt-get install -y build-essential pkg-config libcriterion-dev
make && ./build/tests_runner

Build and Run Tests

make
./build/tests_runner

Clean Build Artifacts

make clean

Usage as a Library

StringsAndCiphers.c/.h can be dropped into another project, or you can build a static/shared library if desired. Key entry points include:

get_str_length, copy_str, to_uppercase, to_lowercase
person_make_new, person_to_string, group_make_new, add_person, remove_person
encrypt_caesar, decrypt_caesar
is_reversible, get_decryption_key, encrypt_substitution, decrypt_substitution

Development Notes

Compiles with -Wall -Wextra -Wpedantic -std=c11. Treat warnings as errors locally with:
```
CFLAGS="-Wall -Wextra -Wpedantic -Werror -std=c11" make
```
Memory safety: APIs that return newly allocated strings specify that the caller owns the memory.
Tests: Criterion-based tests live under tests/ and run via the build/tests_runner target.

Editor and IDE Support

This repo includes .vscode/launch.json and .vscode/tasks.json to make building and running tests convenient for VS Code users. For JetBrains CLion users, the project also works smoothly: open the folder as a CMake project, set up Criterion as an external library (via pkg-config or manual linking), and configure the test target to run build/tests_runner.

r-siddiq/StringsAndCiphers