Lesson 07 · Parse the request line

Parse the request line

The first line of every request names the method, the target, and the protocol version. Today you split it into those three parts and reject anything that is not shaped that way.

The goal

Split a request line into method, target, and version, and report an error if it does not have exactly three parts.

Start here - the target

TO DO

Scenario: Parsing the request line

Giventhe line "GET /index.html HTTP/1.1"

Whenit is parsed

Thenmethod = "GET", target = "/index.html", version = "HTTP/1.1"

Andthe line "GET /index.html" (only two parts) is reported as an error

Background

The request line is three tokens separated by single spaces: the method (GET, POST, …), the request target (the path being asked for), and the HTTP version. Splitting on spaces and taking the three pieces is all it takes to read it.

Insist on exactly three parts. A line with two or four tokens is malformed, and returning an error here — rather than limping on with a missing version — is what lets the server answer a broken request with a clean 400 later. The target never contains a space, so a plain three-way split is safe. For now just return the three strings; a few lessons from now they will become fields on a Request.

Make it work

parts := strings.Split(line, " ")
if len(parts) != 3 { // method, target, version — exactly three
    return "", "", "", errors.New("malformed request line")
}
method, target, version := parts[0], parts[1], parts[2]

CheckpointDONE

The request line parses into method, target, and version, and rejects malformed lines. Commit.