Closes #434

Signed-off-by: Vishal Rana <vr@labstack.com>

context.go

@@ -7,7 +7,6 @@ import (
 	"mime"
 	"mime/multipart"
 	"net/http"
-	"os"
 	"path"
 	"path/filepath"
 	"time"
@@ -134,6 +133,11 @@ type (
 		// Echo returns the `Echo` instance.
 		Echo() *Echo
 
+		// ServeContent sends static content from `io.Reader` and handles caching
+		// via `If-Modified-Since` request header. It automatically sets `Content-Type`
+		// and `Last-Modified` response headers.
+		ServeContent(http.File) error
+
 		// Object returns the `context` instance.
 		Object() *context
 
@@ -376,10 +380,8 @@ func (c *context) File(file string) error {
 		if err != nil {
 			return ErrNotFound
 		}
-		fi, _ = f.Stat()
 	}
-
-	return ServeContent(c.Request(), c.Response(), f, fi)
+	return c.ServeContent(f)
 }
 
 func (c *context) Attachment(r io.Reader, name string) (err error) {
@@ -420,13 +422,24 @@ func (c *context) Object() *context {
 	return c
 }
 
-// ServeContent sends a response from `io.Reader`. It automatically sets the `Content-Type`
-// and `Last-Modified` headers.
-func ServeContent(rq engine.Request, rs engine.Response, f http.File, fi os.FileInfo) error {
+func (c *context) ServeContent(f http.File) error {
+	rq := c.Request()
+	rs := c.Response()
+	fi, err := f.Stat()
+	if err != nil {
+		return err
+	}
+
+	if t, err := time.Parse(http.TimeFormat, rq.Header().Get(IfModifiedSince)); err == nil && fi.ModTime().Before(t.Add(1*time.Second)) {
+		rs.Header().Del(ContentType)
+		rs.Header().Del(ContentLength)
+		return c.NoContent(http.StatusNotModified)
+	}
+
 	rs.Header().Set(ContentType, detectContentType(fi.Name()))
 	rs.Header().Set(LastModified, fi.ModTime().UTC().Format(http.TimeFormat))
 	rs.WriteHeader(http.StatusOK)
-	_, err := io.Copy(rs, f)
+	_, err = io.Copy(rs, f)
 	return err
 }
 

context_test.go

@@ -239,6 +239,33 @@ func TestContextNetContext(t *testing.T) {
 	// assert.Equal(t, "val", c.Value("key"))
 }
 
+func TestContextServeContent(t *testing.T) {
+	e := New()
+	rq := test.NewRequest(GET, "/", nil)
+	rc := test.NewResponseRecorder()
+	c := NewContext(rq, rc, e)
+
+	// Not cached
+	fs := http.Dir("_fixture/images")
+	f, err := fs.Open("walle.png")
+	if assert.NoError(t, err) {
+		if assert.NoError(t, c.ServeContent(f)) {
+			assert.Equal(t, http.StatusOK, rc.Status())
+		}
+	}
+
+	// Cached
+	rc = test.NewResponseRecorder()
+	c = NewContext(rq, rc, e)
+	fi, err := f.Stat()
+	if assert.NoError(t, err) {
+		rq.Header().Set(IfModifiedSince, fi.ModTime().UTC().Format(http.TimeFormat))
+		if assert.NoError(t, c.ServeContent(f)) {
+			assert.Equal(t, http.StatusNotModified, rc.Status())
+		}
+	}
+}
+
 func testBindOk(t *testing.T, c Context, ct string) {
 	c.Request().Header().Set(ContentType, ct)
 	u := new(user)

echo.go

@@ -176,6 +176,7 @@ const (
 	ContentEncoding    = "Content-Encoding"
 	ContentLength      = "Content-Length"
 	ContentType        = "Content-Type"
+	IfModifiedSince    = "If-Modified-Since"
 	LastModified       = "Last-Modified"
 	Location           = "Location"
 	Upgrade            = "Upgrade"

middleware/static.go

@@ -61,7 +61,7 @@ func StaticFromConfig(config StaticConfig) echo.MiddlewareFunc {
 			if fi.IsDir() {
 				/* NOTE:
 				Not checking the Last-Modified header as it caches the response `304` when
-				changing differnt directories for the same path.
+				changing different directories for the same path.
 				*/
 				d := f
 
@@ -97,9 +97,8 @@ func StaticFromConfig(config StaticConfig) echo.MiddlewareFunc {
 					}
 					return next.Handle(c)
 				}
-				fi, _ = f.Stat() // Index file stat
 			}
-			return echo.ServeContent(c.Request(), c.Response(), f, fi)
+			return c.ServeContent(f)
 		})
 	}
 }