1 1a048c00 2022-11-15 o package main
  2 1a048c00 2022-11-15 o 
  3 1a048c00 2022-11-15 o import (
  4 1a048c00 2022-11-15 o 	"archive/tar"
  5 1a048c00 2022-11-15 o 	"errors"
  6 1a048c00 2022-11-15 o 	"fmt"
  7 1a048c00 2022-11-15 o 	"io"
  8 1a048c00 2022-11-15 o 	"io/fs"
  9 1a048c00 2022-11-15 o 	"log"
 10 1a048c00 2022-11-15 o 	"net/http"
 11 1a048c00 2022-11-15 o 	"os"
 12 1a048c00 2022-11-15 o 	"path"
 13 1a048c00 2022-11-15 o 	"time"
 14 1a048c00 2022-11-15 o )
 15 1a048c00 2022-11-15 o 
 16 1a048c00 2022-11-15 o func cacheDir() (string, error) {
 17 1a048c00 2022-11-15 o 	d, err := os.UserCacheDir()
 18 1a048c00 2022-11-15 o 	return path.Join(d, "tarweb"), err
 19 1a048c00 2022-11-15 o }
 20 1a048c00 2022-11-15 o 
 21 1a048c00 2022-11-15 o func Extract(r *tar.Reader, dir string) error {
 22 1a048c00 2022-11-15 o 	for {
 23 1a048c00 2022-11-15 o 		hdr, err := r.Next()
 24 1a048c00 2022-11-15 o 		if err == io.EOF {
 25 1a048c00 2022-11-15 o 			break // End of archive
 26 1a048c00 2022-11-15 o 		}
 27 1a048c00 2022-11-15 o 		if err != nil {
 28 1a048c00 2022-11-15 o 			return err
 29 1a048c00 2022-11-15 o 		}
 30 1a048c00 2022-11-15 o 		fmt.Println(hdr.Name)
 31 1a048c00 2022-11-15 o 		if hdr.FileInfo().IsDir() {
 32 1a048c00 2022-11-15 o 			err := os.MkdirAll(path.Join(dir, hdr.Name), 0755)
 33 1a048c00 2022-11-15 o 			if err != nil && !errors.Is(err, fs.ErrExist) {
 34 1a048c00 2022-11-15 o 				return fmt.Errorf("extract %s: %w", hdr.Name, err)
 35 1a048c00 2022-11-15 o 			}
 36 1a048c00 2022-11-15 o 			continue
 37 1a048c00 2022-11-15 o 		}
 38 1a048c00 2022-11-15 o 		dst := path.Join(dir, hdr.Name)
 39 1a048c00 2022-11-15 o 		f, err := os.Create(dst)
 40 1a048c00 2022-11-15 o 		if err != nil {
 41 1a048c00 2022-11-15 o 			return fmt.Errorf("extract %s: %v", hdr.Name, err)
 42 1a048c00 2022-11-15 o 		}
 43 1a048c00 2022-11-15 o 		if _, err := io.Copy(f, r); err != nil {
 44 1a048c00 2022-11-15 o 			return fmt.Errorf("extract %s: %v", hdr.Name, err)
 45 1a048c00 2022-11-15 o 		}
 46 1a048c00 2022-11-15 o 		f.Close()
 47 1a048c00 2022-11-15 o 	}
 48 1a048c00 2022-11-15 o 	return nil
 49 1a048c00 2022-11-15 o }
 50 1a048c00 2022-11-15 o 
 51 1a048c00 2022-11-15 o var urls []string = []string{"http://127.0.0.1:8000/test.tar"}
 52 1a048c00 2022-11-15 o 
 53 1a048c00 2022-11-15 o var archives = make(map[string]time.Time)
 54 1a048c00 2022-11-15 o 
 55 1a048c00 2022-11-15 o func getIfModified(url string, since time.Time) (*http.Response, error) {
 56 1a048c00 2022-11-15 o 	req, err := http.NewRequest(http.MethodGet, url, nil)
 57 1a048c00 2022-11-15 o 	if err != nil {
 58 1a048c00 2022-11-15 o 		return nil, err
 59 1a048c00 2022-11-15 o 	}
 60 1a048c00 2022-11-15 o 	req.Header.Add("If-Modified-Since", since.UTC().Format(time.RFC1123Z))
 61 1a048c00 2022-11-15 o 	return http.DefaultClient.Do(req)
 62 1a048c00 2022-11-15 o }
 63 1a048c00 2022-11-15 o 
 64 1a048c00 2022-11-15 o func fetchloop(root string, sleep time.Duration) {
 65 1a048c00 2022-11-15 o 	for {
 66 1a048c00 2022-11-15 o 		for url, since := range archives {
 67 1a048c00 2022-11-15 o 			resp, err := getIfModified(url, since)
 68 1a048c00 2022-11-15 o 			if err != nil {
 69 1a048c00 2022-11-15 o 				log.Println("get archive:", err)
 70 1a048c00 2022-11-15 o 				continue
 71 1a048c00 2022-11-15 o 			}
 72 1a048c00 2022-11-15 o 			if resp.StatusCode == http.StatusNotModified {
 73 1a048c00 2022-11-15 o 				log.Printf("%s unmodified", url)
 74 1a048c00 2022-11-15 o 				continue
 75 1a048c00 2022-11-15 o 			}
 76 1a048c00 2022-11-15 o 			if resp.Header.Get("Last-Modified") != "" {
 77 1a048c00 2022-11-15 o 				modified, err := time.Parse(time.RFC1123, resp.Header.Get("Last-Modified"))
 78 1a048c00 2022-11-15 o 				if err != nil {
 79 1a048c00 2022-11-15 o 					log.Printf("parse last modified time for %s: %v", url, err)
 80 1a048c00 2022-11-15 o 					continue
 81 1a048c00 2022-11-15 o 				}
 82 1a048c00 2022-11-15 o 				archives[url] = modified
 83 1a048c00 2022-11-15 o 			}
 84 1a048c00 2022-11-15 o 			rd := tar.NewReader(resp.Body)
 85 1a048c00 2022-11-15 o 			if err := Extract(rd, root); err != nil {
 86 1a048c00 2022-11-15 o 				log.Printf("extract %s: %v", url, err)
 87 1a048c00 2022-11-15 o 			}
 88 1a048c00 2022-11-15 o 			resp.Body.Close()
 89 1a048c00 2022-11-15 o 		}
 90 1a048c00 2022-11-15 o 		time.Sleep(sleep)
 91 1a048c00 2022-11-15 o 	}
 92 1a048c00 2022-11-15 o }
 93 1a048c00 2022-11-15 o 
 94 1a048c00 2022-11-15 o func main() {
 95 1a048c00 2022-11-15 o 	archives["http://127.0.0.1:8000/test.tar"] = time.Time{}
 96 1a048c00 2022-11-15 o 	archives["http://127.0.0.1:8000/meerkat.tar"] = time.Time{}
 97 1a048c00 2022-11-15 o 	cache, err := cacheDir()
 98 1a048c00 2022-11-15 o 	if err != nil {
 99 1a048c00 2022-11-15 o 		log.Fatal(err)
100 1a048c00 2022-11-15 o 	}
101 1a048c00 2022-11-15 o 	if err := os.MkdirAll(cache, 0755); err != nil {
102 1a048c00 2022-11-15 o 		log.Fatal(err)
103 1a048c00 2022-11-15 o 	}
104 1a048c00 2022-11-15 o 	log.Println("serving archives from", cache)
105 1a048c00 2022-11-15 o 	go fetchloop(cache, 20*time.Second)
106 1a048c00 2022-11-15 o 	log.Fatal(http.ListenAndServe(":6969", http.FileServer(http.FS(os.DirFS(cache)))))
107 1a048c00 2022-11-15 o }