50 Lines of C Code for HTTP Parsing with Exceptional Performance!

Introduction

Have you ever wondered how lightweight an HTTP parser can be? Today, we will introduce a project—httplite—that implements a zero-copy, zero-allocation, dependency-free HTTP/1.1 parser in just 50 lines of C code. Even more impressive, it is fully compatible with the C89 standard and does not rely on the standard library! Sounds a bit “geeky,” right? Let’s unveil its mysteries together!

What is httplite?

httplite is a minimalist HTTP parsing library created by developer xyurt, with the core idea of:fast, accurate, and efficient. It avoids unnecessary features and focuses solely on one task—efficiently parsing the start line and headers of HTTP requests or responses.

It uses pure pointer arithmetic, with no memory copying (zero-copy) and no dynamic memory allocation (zero-allocation), making it very suitable for embedded systems or high-performance scenarios.

Core Features Overview

  • ✅ Minimalist Design: Only one header file <span>httplite.h</span>, with a total of 50 lines of code.
  • ✅ Zero-Copy: Operates directly in the input buffer without copying data.
  • ✅ Zero-Allocation: Does not use any dynamic memory allocation functions like <span>malloc</span>.
  • ✅ No Dependencies: No standard library dependencies, not even <span><stdio.h></span>.
  • ✅ Strong Compatibility: Supports the C89 standard, suitable for older compiler environments.
  • ✅ High Performance: Suitable for high-throughput or resource-constrained embedded systems.

How to Use?

Usage is very simple; just include the header file:

#include "httplite.h"

Then you can parse an HTTP request like this:

void main() {
    const char *request = "GET /index.html HTTP/1.1\r\nHost: example.com\r\nConnection: close\r\n\r\n";
    size_t len = 66;

    http_message message;
    if (http_parse_message(request, len, &message)) {
        printf("Method: %.*s\n", (int)message.part1_length, message.part1);
        printf("Path: %.*s\n", (int)message.part2_length, message.part2);
        printf("Version: %.*s\n", (int)message.part3_length, message.part3);

        const char *name, *value;
        size_t name_len, value_len;

        printf("Headers:\n");
        while (http_next_header(&message, &name, &name_len, &value, &value_len)) {
            if (name == NULL || name_len == 0) break;
            printf("  %.*s: %.*s\n", (int)name_len, name, (int)value_len, value);
        }
    }
}

How Does It Achieve Such Speed?

The Art of Pointer Arithmetic

httplite relies entirely on pointer arithmetic to perform parsing, without any string handling functions (like <span>strcpy</span>, <span>strtok</span>, etc.). This method is not only fast but also consumes almost no additional memory.

Dependency-Free Struct Design

It uses a simple struct <span>http_message</span> to record the current parsing position and state, allowing subsequent calls to <span>http_next_header</span> to read HTTP headers one by one like a stream.

Where Are the Performance Advantages?

  • CPU Friendly: No unnecessary data copying or function calls.
  • Memory Friendly: Does not allocate heap memory, and stack space usage is minimal.
  • Suitable for Embedded Systems: Can run on devices with extremely limited resources.
  • Suitable for High-Frequency IO: Ideal for server programs that require frequent HTTP protocol parsing.

Current Limitations

Although httplite is very lightweight and efficient, it also has its limitations:

  • Only supports parsing of the start line and headers for HTTP/1.x;
  • Must use <span>\r\n</span> as the line terminator;
  • Does not validate message body or header content;
  • Does not support multi-line headers or chunked transfer encoding.

So if you need to fully parse an entire HTTP message (including the body), it may not be suitable for you. But if you only need to parse headers, it is definitely the most refined choice you have seen!

Recommended Use Cases

  • HTTP service modules in embedded devices;
  • High-performance network proxies or gateways;
  • Basic components for custom protocol parsers;
  • A great teaching material for learning the underlying principles of the HTTP protocol.

Conclusion: Small and Beautiful is Truly Hardcore!

In this era of pursuing “big and complete,” httplite proves with less than a page of code that:real experts simplify complex things. It is not only a technical minimalist but also a perfect interpretation of the philosophy of “less is more.”

Open Source License and Repository Information

  • License: MIT License
  • GitHub Repository: https://github.com/xyurt/httplite

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