# Systems Programming Projects

Low-level work: operating systems, compilers, networking, and performance engineering.

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## Tiny HTTP/1.1 Server (C)

A from-scratch HTTP server written in C that handles concurrent connections using `epoll` on Linux.

**What it does:**

- Serves static files with correct MIME types
- Handles `keep-alive` connections
- Parses request headers manually (no third-party parser)
- ~1,200 lines of C — intentionally minimal

**Interesting problems solved:**

- Non-blocking I/O with an event loop
- Incremental parsing of chunked request bodies
- Safe path traversal (no `../` escapes from the document root)

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## Shell Implementation (C)

A POSIX-compatible shell (`mysh`) supporting pipelines, redirections, background jobs, and a small built-in set.

**Supported features:**

- Pipelines: `cmd1 | cmd2 | cmd3`
- I/O redirections: `>`, `>>`, `<`, `2>`
- Background jobs: `cmd &`
- Job control: `fg`, `bg`, `jobs`
- Signal handling (SIGINT, SIGTSTP, SIGHUP)

**Focus areas:** `fork/exec` model, `waitpid`, file descriptor management, signal masking.

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## Memory Allocator

A drop-in `malloc` replacement using `mmap`-backed free lists with coalescing.

**Algorithms implemented:**

- First-fit and best-fit strategies (switchable at compile time)
- Boundary-tag coalescing to reduce fragmentation
- Thread-local caches for small allocations (reduces lock contention)

**Benchmarked** against `glibc malloc` on synthetic workloads — within 2× for mixed-size allocations.

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## Bytecode Interpreter (Python → C)

A small virtual machine that executes a simple bytecode format, written in C. The front-end compiler is written in Python and produces `.bco` files.

**VM features:**

- Stack-based architecture (inspired by CPython)
- 30 opcodes: arithmetic, comparisons, jumps, function calls, closures
- Mark-and-sweep garbage collector
- Disassembler for debugging (`--disasm` flag)

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