lwhttp

A lightweight HTTP/1.1 library in C, built from the wire format up using only the C standard library and POSIX.

Why

Built to understand HTTP/1.1 end-to-end without leaning on libcurl, nginx, or a framework as a black box. The goal is a small, readable codebase that maps cleanly onto the relevant sections of RFC 9110 and RFC 9112.

What works today

• Open-addressing hashmap with case-insensitive keys (for headers)
• Method parsing: GET, HEAD, POST, PUT, DELETE, OPTIONS, PATCH
• Request struct: method, URI, version, headers, body
• Response struct: status, reason, version, headers, body
• Request and response serialization to wire format
• Request parsing from a byte buffer (Content-Length bodies)
• Socket server loop
• Transfer-Encoding: chunked
• Persistent connections (Connection: keep-alive)
• Client-side request sending

Non-goals

• TLS (delegate to a reverse proxy)
• HTTP/2 or HTTP/3
• Async I/O — blocking sockets are sufficient for the learning scope

Layout

include/hashmap.h, src/hashmap.c   open-addressing map, case-insensitive keys
include/http.h,    src/http.c      methods, request/response types, parse, serialize
src/main.c                         test driver exercising the library

Building

Requires Meson and a C2x-capable compiler.

meson setup build
meson compile -C build
./build/lwhttp-test

Design notes

• Hashmap for headers. Header lookup is case-insensitive per RFC 9110 §5.1, and a request can carry dozens of headers. A small open-addressing map keeps lookup O(1) average and avoids per-lookup strcasecmp scans.
• Incremental parser API. lw_request_parse returns 1 when the buffer is incomplete so a caller can read more from a socket and retry, rather than forcing the whole request to be buffered before parsing begins.
• C2x + warning level 3. Lets the compiler catch as much as possible at build time given the manual memory management.