Etag.go

main.go

package main

import (
	"bitbucket.org/agallego/log"
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
)

var (
	IdGenerator = 0
)

func main() {
	log.Info("Starting")
	http.HandleFunc("/ym.jpg", func(w http.ResponseWriter, r *http.Request) {
		log.Info("requesting jpg")
		// log.Info("All headers %+#v", r.Header)
		if len(r.Header.Get("If-None-Match")) != 0 || len(r.Header.Get("etag")) != 0 {
			tag := r.Header.Get("ETag")
			if len(tag) == 0 {
				tag = r.Header.Get("If-None-Match")
			}
			log.Info("Using old etag: %s", tag)
			w.Header().Set("ETag", tag)
			w.WriteHeader(http.StatusNotModified)
		} else {
			log.Info("generating etag")
			fileBytes, _ := ioutil.ReadFile("static/ym.jpg")
			IdGenerator++
			log.Info("Using ETag: %d", IdGenerator)
			w.Header().Set("ETag", fmt.Sprintf("%d", IdGenerator))
			w.Header().Set("Content-type", "image/jpeg")
			w.Header().Set("Content-length", fmt.Sprintf("%d", len(fileBytes)))
			w.Header().Set("If-None-Match", fmt.Sprintf("%d", IdGenerator))
			io.Copy(w, bytes.NewReader(fileBytes))
		}
	})
	http.Handle("/", http.FileServer(http.Dir("static")))
	http.ListenAndServe(":8080", nil)
}