llhttp

HTTP request/response parser extracted from nodejs/llhttp.

This is the HTTP parser used by Node.js - battle-tested against billions of requests. It's a pure C library with no dependencies, designed for high-performance HTTP parsing with a callback-based, zero-copy API.

Source

• Upstream Repository: https://github.com/nodejs/llhttp
• Upstream Version: v9.3.0
• Upstream Commit: release/v9.3.0
• Upstream Date: 2025-05-23
• License: MIT - see LICENSE

Features

• Pure C, zero dependencies
• Callback-based, zero-copy parsing (pointers into your buffer)
• Incremental parsing (feed bytes as they arrive)
• Handles all HTTP/1.x edge cases:
  • Chunked transfer encoding
  • Keep-alive detection
  • Header line folding
  • Request pipelining
  • Content-Length vs Transfer-Encoding
• ~20KB compiled
• Extensively tested (Node.js test suite)

Updating

1. Check for new releases at https://github.com/nodejs/llhttp/releases

2. Download the release tarball:

   gh release download release/vX.Y.Z --repo nodejs/llhttp --archive=tar.gz -D /tmp
   cd /tmp && tar -xzf nodejs-llhttp-*.tar.gz

3. Copy the files:

   cp /tmp/llhttp-release-vX.Y.Z/include/llhttp.h include/
   cp /tmp/llhttp-release-vX.Y.Z/src/*.c src/
   cp /tmp/llhttp-release-vX.Y.Z/LICENSE-MIT LICENSE

4. Update this README with the new version, commit hash, and date.

5. Test the build in IREE.

Contents

include/

• llhttp.h - Public API header with types, callbacks, and function declarations

src/

• llhttp.c - Core parser state machine (auto-generated)
• api.c - User-facing API functions (init, execute, settings)
• http.c - HTTP-specific helpers (keep-alive, upgrade detection)

Usage

#include "llhttp.h"

// Callbacks receive pointers into your buffer (zero-copy)
int on_url(llhttp_t* parser, const char* at, size_t length) {
  printf("URL: %.*s\n", (int)length, at);
  return 0;
}

int on_header_field(llhttp_t* parser, const char* at, size_t length) {
  printf("Header: %.*s\n", (int)length, at);
  return 0;
}

int main() {
  llhttp_t parser;
  llhttp_settings_t settings;

  llhttp_settings_init(&settings);
  settings.on_url = on_url;
  settings.on_header_field = on_header_field;

  llhttp_init(&parser, HTTP_REQUEST, &settings);

  const char* request = "GET /hello HTTP/1.1\r\nHost: example.com\r\n\r\n";
  enum llhttp_errno err = llhttp_execute(&parser, request, strlen(request));

  if (err != HPE_OK) {
    fprintf(stderr, "Parse error: %s\n", llhttp_errno_name(err));
    return 1;
  }
  return 0;
}

Building

Bazel (IREE)

cc_library(
    name = "llhttp",
    srcs = glob(["src/*.c"]),
    hdrs = ["include/llhttp.h"],
    includes = ["include"],
    visibility = ["//visibility:public"],
)

CMake

add_library(llhttp
  src/llhttp.c
  src/api.c
  src/http.c
)
target_include_directories(llhttp PUBLIC include)

Local Patches

(none)