# libuv — Cross-Platform Asynchronous I/O Library

> The event loop and async I/O library that powers Node.js, providing non-blocking TCP/UDP, filesystem, DNS, and child process APIs for C and C++.

## Install

Save in your project root:

# libuv — Cross-Platform Asynchronous I/O Library

## Quick Use
```bash
# Install via system package manager
sudo apt install libuv1-dev   # Debian/Ubuntu
brew install libuv             # macOS
vcpkg install libuv            # vcpkg
```

```c
#include <uv.h>

int main() {
    uv_loop_t *loop = uv_default_loop();
    printf("Default loop running.\n");
    uv_run(loop, UV_RUN_DEFAULT);
    return 0;
}
```

## Introduction
libuv is a multi-platform C library that provides an event loop with async I/O, originally developed for Node.js. It abstracts OS-specific APIs (epoll, kqueue, IOCP, event ports) behind a single portable interface, enabling high-performance network servers and system tools on Linux, macOS, Windows, and more.

## What libuv Does
- Manages an event loop with support for timers, idle watchers, and signal handlers
- Provides non-blocking TCP and UDP sockets with connection pooling
- Offers async file system operations backed by a thread pool
- Handles DNS resolution, child process spawning, and IPC via pipes
- Delivers cross-platform threading, mutexes, and read-write locks

## Architecture Overview
At its core libuv runs a single-threaded event loop that polls for I/O readiness using the fastest OS primitive available. Network I/O is handled directly in the loop thread. File system operations and DNS lookups are dispatched to a configurable thread pool (default 4 threads) since most OSes lack true async file I/O. Callbacks fire on the loop thread, avoiding synchronization complexity for users.

## Self-Hosting & Configuration
- Build with CMake: `mkdir build && cd build && cmake .. && make`
- Link against `libuv` (shared) or `libuv_a` (static)
- Set the thread pool size via `UV_THREADPOOL_SIZE` environment variable (default 4, max 1024)
- Works on Linux, macOS, Windows, FreeBSD, Solaris, AIX, and Android
- Minimum requirement: C89 compiler; no C++ or external dependencies

## Key Features
- Powers Node.js, Neovim, Julia, Luvit, and many other runtimes
- Full-featured IOCP support makes it one of the best async libraries on Windows
- Stable C API with strong backward compatibility guarantees
- Extensive test suite and continuous fuzzing via OSS-Fuzz
- MIT licensed with an active community and regular releases

## Comparison with Similar Tools
- **libevent** — older, similar scope; libuv has simpler API and better Windows support
- **libev** — Unix-focused, no native Windows IOCP; lighter but less portable
- **Boost.Asio** — C++ only, header-heavy; libuv is plain C with smaller footprint
- **io_uring** — Linux-only kernel interface; libuv wraps it on newer kernels transparently
- **mio (Rust)** — similar abstraction but for Rust; libuv targets C/C++

## FAQ
**Q: Is libuv only for Node.js?**
A: No. It is a standalone C library used by Neovim, Julia, Luvit, CMake, and hundreds of other projects.

**Q: Does libuv support io_uring?**
A: Experimental io_uring support was added for file I/O on Linux. Network I/O still uses epoll by default.

**Q: How does the thread pool affect performance?**
A: The pool handles blocking operations (file I/O, DNS). Increase `UV_THREADPOOL_SIZE` if your workload is file-heavy.

**Q: Can I embed multiple event loops?**
A: Yes. You can create multiple loops with `uv_loop_new()`, each running in its own thread.

## Sources
- https://github.com/libuv/libuv
- https://docs.libuv.org/en/v1.x/

---
Source: https://tokrepo.com/en/workflows/asset-5f6e751d
Author: AI Open Source