AsyncHttpMachine

AsyncHttpMachine is adapted from Benjamin van der Veen's HttpMachine C# HTTP request parser. It implements an asynchronous state machine with Adrian Thurston's excellent state machine compiler, Ragel, using C#'s Task, async and await features. Because Ragel supports C, D, Java, Ruby, it wouldn't be hard to port this library to those languages.

HttpMachine is Copyright (c) 2011 Benjamin van der Veen. HttpMachine is licensed under the MIT License. See LICENSE.txt. No copyright is claimed on the minor adaptations to asynchronous use made by CommodiFusion Ltd.

Features

• HTTP/1.1 and 1.0
• Supports pipelined requests
• Tells your server if it should keep-alive
• Extracts the length of the entity body

Eminently-possible future features

• Support for decoding chunked transfers.
• Support for protocol upgrade.
• Support for parsing responses.

Usage

AsyncHttpMachine provides HTTP data through callbacks. To receive these callbacks, implement the IHttpParserHandler interface.

public interface IHttpParserHandler
{
    Task OnMessageBegin(HttpParser parser);
    Task OnMethod(HttpParser parser, string method);
    Task OnRequestUri(HttpParser parser, string requestUri);
    Task OnFragment(HttpParser parser, string fragment);
    Task OnQueryString(HttpParser parser, string queryString);
    Task OnHeaderName(HttpParser parser, string name);
    Task OnHeaderValue(HttpParser parser, string value);
    Task OnHeadersEnd(HttpParser parser);
    Task OnBody(HttpParser parser, ArraySegment<byte> data);
    Task OnMessageEnd(HttpParser parser);
}

Then, create an instance of HttpParser. Whenever you read data, execute the parser on the data. The Execute method returns the number of bytes successfully parsed. If value is not the same as the length of the buffer you provided, an error occurred while parsing. Make sure you provide a zero-length buffer at the end of the stream, as some callbacks may still be pending.

var handler = new MyHttpParserHandler();
var parser = new HttpParser(handler);

var buffer = new byte[1024 /* or whatever you like */]

int bytesRead;

while ((bytesRead = inputStream.Read(buffer, 0, buffer.Length)) > 0)
    if (bytesRead != await parser.Execute(new ArraySegment<byte>(buffer, 0, bytesRead))
        goto error; /* or whatever you like */

// ensure you get the last callbacks.
await parser.Execute(default(ArraySegment<byte>));

The parser has three public properties:

// HTTP version provided in the request
public int MajorVersion { get; }
public int MinorVersion { get; }

// inspects "Connection" header and HTTP version (if any) to recommend a connection behavior
public bool ShouldKeepAlive { get; }

These properties are only guaranteed to be accurate in the OnBody and OnMessageEnd callbacks.