Method ServeHTTP

coderd/cachecompress/compress.go:174–213

ServeHTTP returns the response from the orig file system, compressed if possible.

(w http.ResponseWriter, r *http.Request)

// ServeHTTP returns the response from the orig file system, compressed if possible.
func (c *Compressor) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	encoding := c.selectEncoder(r.Header)

	// we can only serve a cached response if all the following:
	// 1. they requested an encoding we support
	// 2. they are requesting the whole file, not a range
	// 3. the method is GET
	if encoding == "" || r.Header.Get("Range") != "" || r.Method != "GET" {
		http.FileServer(c.orig).ServeHTTP(w, r)
		return
	}

	// Whether we should serve a cached response also depends in a fairly complex way on the path and request
	// headers. In particular, we don't need a cached response for non-existing files/directories, and should not serve
	// a cached response if the correct Etag for the file is provided. This logic is all handled by the http.FileServer,
	// and we don't want to reimplement it here. So, what we'll do is send a HEAD request to the http.FileServer to see
	// what it would do.
	headReq := r.Clone(r.Context())
	headReq.Method = http.MethodHead
	headRW := &compressResponseWriter{
		w:       io.Discard,
		headers: make(http.Header),
	}
	// deep-copy the headers already set on the response. This includes things like ETags.
	for key, values := range w.Header() {
		for _, value := range values {
			headRW.headers.Add(key, value)
		}
	}
	http.FileServer(c.orig).ServeHTTP(headRW, headReq)
	if headRW.code != http.StatusOK {
		// again, fall back to the file server. This is often a 404 Not Found, or a 304 Not Modified if they provided
		// the correct ETag.
		http.FileServer(c.orig).ServeHTTP(w, r)
		return
	}

	cref := c.getRef(encoding, r)
	c.serveRef(w, r, headRW.headers, cref)
}

func (c *Compressor) serveRef(w http.ResponseWriter, r *http.Request, headers http.Header, cref ref) {
	select {