database_scratch

A lightweight key-value database implementation in C++ with write-ahead logging (WAL) for durability.

Features

• Key-Value Store: Simple API for set, get, delete operations
• Write-Ahead Log (WAL): Binary log format with CRC32 checksums for data integrity
• Persistent Storage: Durable storage to disk with crash recovery
• Interactive CLI: Command-line interface for database operations

Architecture

┌─────────────────────────────────────┐
│            Database                 │
│  API: set, get, del, exists         │
├─────────────────────────────────────┤
│            KVStore                  │
│     (in-memory hash map)            │
├─────────────────────────────────────┤
│    WAL (Write-Ahead Log)            │
│       (durability)                  │
├─────────────────────────────────────┤
│         Storage                     │
│    (disk persistence)               │
└─────────────────────────────────────┘

WAL Format

Each record in the write-ahead log follows this binary format:

| CRC32 (4 bytes) | Type (1 byte) | KeyLen (4) | ValLen (4) | Key | Value |

• CRC32: Checksum for data integrity verification
• Type: Operation type (SET or DEL)
• KeyLen/ValLen: Length of key and value in bytes
• Key/Value: Actual data

Building

mkdir build && cd build
cmake ..
make

Usage

Run the CLI:

./database_scratch

Available commands:

• set <key> <value> - Store a key-value pair
• get <key> - Retrieve value for a key
• del <key> - Delete a key
• exists <key> - Check if a key exists
• clear - Clear the screen
• help - Show available commands
• exit - Quit the program

Project Structure

database_scratch/
├── include/
│   ├── cli.hpp
│   └── db/
│       ├── common.hpp
│       ├── database.hpp
│       ├── kv_store.hpp
│       ├── storage.hpp
│       └── wal.hpp
├── src/
│   ├── main.cpp
│   ├── cli/
│   │   └── cli.cpp
│   └── db/
│       ├── database.cpp
│       ├── kv_store.cpp
│       ├── storage.cpp
│       └── wal.cpp
└── tests/
    └── test_database.cpp

Requirements

• C++20 compatible compiler
• CMake 3.15 or higher

License

MIT