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// Copyright 2020 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.
package httpcache
import (
"encoding/base64"
"fmt"
"net/http"
"os"
"strconv"
"strings"
"time"
"code.gitea.io/gitea/modules/setting"
)
// GetCacheControl returns a suitable "Cache-Control" header value
func GetCacheControl() string {
if !setting.IsProd() {
return "no-store"
}
return "private, max-age=" + strconv.FormatInt(int64(setting.StaticCacheTime.Seconds()), 10)
}
// generateETag generates an ETag based on size, filename and file modification time
func generateETag(fi os.FileInfo) string {
etag := fmt.Sprint(fi.Size()) + fi.Name() + fi.ModTime().UTC().Format(http.TimeFormat)
return `"` + base64.StdEncoding.EncodeToString([]byte(etag)) + `"`
}
// HandleTimeCache handles time-based caching for a HTTP request
func HandleTimeCache(req *http.Request, w http.ResponseWriter, fi os.FileInfo) (handled bool) {
w.Header().Set("Cache-Control", GetCacheControl())
ifModifiedSince := req.Header.Get("If-Modified-Since")
if ifModifiedSince != "" {
t, err := time.Parse(http.TimeFormat, ifModifiedSince)
if err == nil && fi.ModTime().Unix() <= t.Unix() {
w.WriteHeader(http.StatusNotModified)
return true
}
}
w.Header().Set("Last-Modified", fi.ModTime().Format(http.TimeFormat))
return false
}
// HandleFileETagCache handles ETag-based caching for a HTTP request
func HandleFileETagCache(req *http.Request, w http.ResponseWriter, fi os.FileInfo) (handled bool) {
etag := generateETag(fi)
return HandleGenericETagCache(req, w, etag)
}
// HandleGenericETagCache handles ETag-based caching for a HTTP request.
// It returns true if the request was handled.
func HandleGenericETagCache(req *http.Request, w http.ResponseWriter, etag string) (handled bool) {
if len(etag) > 0 {
w.Header().Set("Etag", etag)
if checkIfNoneMatchIsValid(req, etag) {
w.WriteHeader(http.StatusNotModified)
return true
}
}
w.Header().Set("Cache-Control", GetCacheControl())
return false
}
// checkIfNoneMatchIsValid tests if the header If-None-Match matches the ETag
func checkIfNoneMatchIsValid(req *http.Request, etag string) bool {
ifNoneMatch := req.Header.Get("If-None-Match")
if len(ifNoneMatch) > 0 {
for _, item := range strings.Split(ifNoneMatch, ",") {
item = strings.TrimSpace(item)
if item == etag {
return true
}
}
}
return false
}
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