Method updateCacheHeaders

imageproxy.go:151–197

updateCacheHeaders updates the cache-control headers in the provided headers. If the cache-control header includes the 'private' directive, then 'no-store' is added to the header to prevent caching. If p.ForceCache is set, then 'private' and 'no-store' are both ignored and removed. This method als

(hdr http.Header)

// duration, the expires header, and the max-age header. It also removes the
// expires header.
func (p *Proxy) updateCacheHeaders(hdr http.Header) {
	cc := tphc.ParseCacheControl(hdr)

	// respect 'private' and 'no-store' directives unless ForceCache is set.
	// The httpcache package ignores the 'private' directive,
	// since it's not intended to be used as a shared cache.
	// imageproxy IS a shared cache, so we enforce the 'private' directive ourself
	// by setting 'no-store', which httpcache does respect.
	if p.ForceCache {
		delete(cc, "private")
		delete(cc, "no-store")
		hdr.Set("Cache-Control", cc.String())
	} else {
		if _, ok := cc["private"]; ok {
			cc["no-store"] = ""
			hdr.Set("Cache-Control", cc.String())
			return
		}
		if _, ok := cc["no-store"]; ok {
			return
		}
	}

	if p.MinimumCacheDuration == 0 {
		return
	}

	var expiresDuration time.Duration
	var maxAgeDuration time.Duration

	if maxAge, ok := cc["max-age"]; ok {
		maxAgeDuration, _ = time.ParseDuration(maxAge + "s")
	}
	if date, err := httpcache.Date(hdr); err == nil {
		if expiresHeader := hdr.Get("Expires"); expiresHeader != "" {
			if expires, err := time.Parse(time.RFC1123, expiresHeader); err == nil {
				expiresDuration = expires.Sub(date)
			}
		}
	}

	maxAge := max(p.MinimumCacheDuration, expiresDuration, maxAgeDuration)
	cc["max-age"] = fmt.Sprintf("%d", int(maxAge.Seconds()))

	hdr.Set("Cache-Control", cc.String())
	hdr.Del("Expires")
}

// ServeHTTP handles incoming requests.
func (p *Proxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {