Tavis.HttpHeaders

This library implements the grammar used to define HTTP headers in RFC 7230-7235. This grammar is then used to create strongly typed implementations of the standard HTTP headers.

This blog post provides and introduction, motivation and requirements for this project.

The syntax rules for a header can be defined as follows:

        var authHeader = new Expression("authorization")
        {
            new Token("scheme"),
            new Rws(),
            new Token("parameter")
        };

The grammar primitive objects encapsulate the rules for permitted characters as defined by the HTTP specification.

The syntax rule can be used to parse a raw header like this,

        var authHeaderNode = authHeader.Consume(new Inputdata("Basic asddasdasdasdasd"));

        Assert.Equal("Basic",authHeaderNode.ChildNode("scheme").Text);
        Assert.Equal("asddasdasdasdasd", authHeaderNode.ChildNode("parameter").Text);

A more complex example would be the syntax for the user agent header.

        var userAgent = new Expression("useragent")
        {
            new Token("product"),
            new OptionalExpression("versionex"){ new Literal("/"), new Token("version") },  //Optional version
            new Rws(),
            new DelimitedList("productorcomments", " ", new Expression("token")
            {
                new Ows(),
                new OrExpression("productorcomment") {
                        new Comment("comment"), 
                        new Expression("productex")
                        {
                            new Token("product"),
                            new OptionalExpression("versionex"){ new Literal("/"), new Token("version") }
                        }   
                }
            })
        };

These syntax rules can be encapsulated inside some strong types that then make it easy to access the headers.

Here is a test showing how to use the strong type that uses that syntax tree.

    [Fact]
    public void UserAgentStrongType()
    {

        var userAgent =
            UserAgentHeaderValue.Parse(
                "Mozilla/4.0 (compatible; Linux 2.6.22) NetFront/3.4 Kindle/2.5 (screen 824x1200;rotate)");
        var primaryProduct = userAgent.Products.First();
        var lastProduct = userAgent.Products.Last();
        Assert.Equal("(compatible; Linux 2.6.22)", primaryProduct.Comments.First());
        Assert.Equal("(screen 824x1200;rotate)", lastProduct.Comments.First());

        Assert.Equal("Mozilla", primaryProduct.Name);
        Assert.Equal("4.0", primaryProduct.Version);

        Assert.Equal("Kindle", lastProduct.Name);
        Assert.Equal("2.5", lastProduct.Version);

        Assert.Equal(3, userAgent.Products.Count);

    }

Currently only a few of the standard headers are implemented. More will be coming soon.

This library is a PCL based library and so will work on Windows 8, Windows Phone 7.5, .Net 4.