echo: support etags for static filesecho/v0.9.5

1 files changed, 30 insertions, 0 deletions

diff --git a/echo/static_file.go b/echo/static_file.go
index 9723db7..258c832 100644
--- a/echo/static_file.go
+++ b/echo/static_file.go
@@ -1,6 +1,8 @@
 package echo
 
 import (
+        "crypto/sha256"
+        "encoding/base64"
         "io"
         "io/fs"
         "net/http"
@@ -12,7 +14,16 @@ import (
 
 type routeFunc func(string, echo.HandlerFunc, ...echo.MiddlewareFunc) *echo.Route
 
+func StaticFSSha256Etags(get routeFunc, f fs.FS, prefix, root string, m ...echo.MiddlewareFunc) *echo.Route {
+        return staticFS(get, f, prefix, root, true, m...)
+}
+
 func StaticFS(get routeFunc, f fs.FS, prefix, root string, m ...echo.MiddlewareFunc) *echo.Route {
+        return staticFS(get, f, prefix, root, false, m...)
+}
+
+// TODO: This should support HEAD requests
+func staticFS(get routeFunc, f fs.FS, prefix, root string, addEtags bool, m ...echo.MiddlewareFunc) *echo.Route {
         if root == "" {
                 root = "." // For security we want to restrict to CWD.
         }
@@ -52,6 +63,25 @@ func StaticFS(get routeFunc, f fs.FS, prefix, root string, m ...echo.MiddlewareF
                         return echo.ErrInternalServerError
                 }
 
+                // Only do this if the consumer requests it since it could be expensive
+                // for high traffic sites as it requires a full read and SHA256
+                // computation
+                // TODO: Cache this?
+                if addEtags {
+                        h := sha256.New()
+                        if _, err := io.Copy(h, fs); err != nil {
+                                c.Logger().Errorf("Error checksumming file %s: %s", p, err)
+                                return echo.ErrInternalServerError
+                        }
+                        etag := base64.RawStdEncoding.EncodeToString(h.Sum(nil))
+                        c.Response().Header().Add("ETag", etag)
+
+                        if _, err := fs.Seek(0, io.SeekStart); err != nil {
+                                c.Logger().Errorf("Error seeking 0 in file %s: %s", p, err)
+                                return echo.ErrInternalServerError
+                        }
+                }
+
                 http.ServeContent(c.Response(), c.Request(), fi.Name(), fi.ModTime(), fs)
                 return nil
         }