[Achintya47]

This PR extends tnerroT from tracker communication and peer discovery to actual data transfer. Introduces peer communication which involves proper handshakes, maintaining peer state machine, and proper communication. Apart from that, thread dispatchable downloader has been implemented with a simple concurrency model. Piece Manager maintains the piece states as Missing, Complete or In-Progress and Logging functionality for network and downloading activities.

What Changed

Peer Management

• Added peer.c / peer.h
• Implemented BitTorrent peer handshake
• Added peer connection management
• Added peer message parsing/framing
• Handles peer availability/bitfield information
• Supports multiple simultaneous peer connections

Download Manager

• Added downloader.c / downloader.h
• Coordinates multiple peer connections
• Assigns pieces/blocks to available peers
• Tracks download progress
• Handles completed and failed requests

Piece Management

• Added piece_manager.c / piece_manager.h
• Tracks piece state
• Prevents multiple peers from unnecessarily downloading the same work
• Tracks requested/completed pieces
• Performs piece-level SHA-1 verification

File Writer

• Added file_writer.c / file_writer.h
• Writes completed pieces directly to their correct file offsets
• Avoids keeping the entire torrent payload in memory
• Supports random-access writes for out-of-order piece completion

Logging

• Added log.c / log.h
• Centralized logging functionality
• Provides consistent logging across peer, downloader, and storage
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