Codecrafters Redis Challenge – C Implementation

This repository contains a minimal Redis server implementation written in C for the Codecrafters Redis challenge.

Features

• TCP server: Accepts connections from Redis clients.
• RESP protocol parsing: Handles the Redis Serialization Protocol for requests and responses.
• Key-value store: Supports basic Redis commands (PING, ECHO, SET, GET).
• Key expiry (TTL): Supports time-to-live for keys.
• Streams and Replication: Includes stream and replication modules for more advanced Redis features.

Folder Structure

app/
├── hashset.c       # Hashset (key-value store) implementation
├── hashset.h
├── message.c       # Handles message/request/response logic
├── message.h
├── parser.c        # RESP protocol parser
├── parser.h
├── replication.c   # Redis replication logic
├── replication.h
├── server.c        # TCP server and main event loop
├── stream.c        # Stream data-type and logic
├── stream.h

Getting Started

Prerequisites

• GCC or Clang (C99 compatible)
• make utility
• Linux/macOS (Windows support may vary)
• redis-cli or netcat for manual testing

Build And Run

./spawn_redis_server.sh

By default, the server listens on port 6379.

Connect & Test

Using redis-cli:

redis-cli -p 6379 ping
redis-cli -p 6379 set foo bar
redis-cli -p 6379 get foo

Or with nc:

echo -en "*1\r\n$4\r\nPING\r\n" | nc localhost 6379

Extending

• Add new commands in message.c and update protocol handling in parser.c.
• Stream and replication features can be extended by editing stream.c and replication.c.

License

MIT License

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Inspired by Redis. Built for the Codecrafters Redis challenge.