Method ServeHTTP

middleware/compress/handler.go:105–197

ServeHTTP implements http.Handler.

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

// ServeHTTP implements http.Handler.
func (c *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	v, ok := r.Header["Accept-Encoding"]
	if !ok { // No header, use "identity".
		c.next.ServeHTTP(w, r)
		return
	}
	ae, nok := parseAccept(v[0])
	var zw zwriter
	// Find the first accept-encoding we support. See
	// https://www.rfc-editor.org/rfc/rfc9110.html#section-12.5.3 for all the
	// semantics.
	//
	// NB The "identity" encoding shouldn't show up in the Content-Encoding
	// response header.
	for _, a := range ae {
		switch a.Type {
		case "gzip", "x-gzip":
			w.Header().Set("content-encoding", "gzip")
			gz := c.gzip.Get().(*gzip.Writer)
			gz.Reset(w)
			defer c.gzip.Put(gz)
			zw = gz
		case "deflate":
			w.Header().Set("content-encoding", "deflate")
			z := c.flate.Get().(*flate.Writer)
			z.Reset(w)
			defer c.flate.Put(z)
			zw = z
		case "zstd":
			w.Header().Set("content-encoding", "zstd")
			s := c.zstd.Get().(*zstd.Encoder)
			s.Reset(w)
			defer c.zstd.Put(s)
			zw = s
		case "identity":
			w.Header().Set("accept-encoding", acceptable)
		case "*":
			// If we hit a star, it's technically OK to return any encoding not
			// already specified. So, attempt to use gzip and then identity and
			// give up.
			// Clients that do extremely weird things like
			//	*;q=1.0, gzip;q=0.1, identity;q=0.1"
			// deserve extremely weird replies.
			_, gznok := nok["gzip"]
			_, idnok := nok["identity"]
			switch {
			case !gznok:
				w.Header().Set("content-encoding", "gzip")
				gz := c.gzip.Get().(*gzip.Writer)
				gz.Reset(w)
				defer c.gzip.Put(gz)
				zw = gz
			case !idnok:
				// "Identity" isn't not OK, so fallthrough.
			default:
				w.Header().Set("accept-encoding", acceptable)
				w.WriteHeader(http.StatusUnsupportedMediaType)
				return