Update vendor, move to labstack/echo/v4 Fixes #698

vendor/github.com/labstack/echo/v4/middleware/compress.go

@@ -0,0 +1,118 @@
+package middleware
+
+import (
+	"bufio"
+	"compress/gzip"
+	"io"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"strings"
+
+	"github.com/labstack/echo/v4"
+)
+
+type (
+	// GzipConfig defines the config for Gzip middleware.
+	GzipConfig struct {
+		// Skipper defines a function to skip middleware.
+		Skipper Skipper
+
+		// Gzip compression level.
+		// Optional. Default value -1.
+		Level int `yaml:"level"`
+	}
+
+	gzipResponseWriter struct {
+		io.Writer
+		http.ResponseWriter
+	}
+)
+
+const (
+	gzipScheme = "gzip"
+)
+
+var (
+	// DefaultGzipConfig is the default Gzip middleware config.
+	DefaultGzipConfig = GzipConfig{
+		Skipper: DefaultSkipper,
+		Level:   -1,
+	}
+)
+
+// Gzip returns a middleware which compresses HTTP response using gzip compression
+// scheme.
+func Gzip() echo.MiddlewareFunc {
+	return GzipWithConfig(DefaultGzipConfig)
+}
+
+// GzipWithConfig return Gzip middleware with config.
+// See: `Gzip()`.
+func GzipWithConfig(config GzipConfig) echo.MiddlewareFunc {
+	// Defaults
+	if config.Skipper == nil {
+		config.Skipper = DefaultGzipConfig.Skipper
+	}
+	if config.Level == 0 {
+		config.Level = DefaultGzipConfig.Level
+	}
+
+	return func(next echo.HandlerFunc) echo.HandlerFunc {
+		return func(c echo.Context) error {
+			if config.Skipper(c) {
+				return next(c)
+			}
+
+			res := c.Response()
+			res.Header().Add(echo.HeaderVary, echo.HeaderAcceptEncoding)
+			if strings.Contains(c.Request().Header.Get(echo.HeaderAcceptEncoding), gzipScheme) {
+				res.Header().Set(echo.HeaderContentEncoding, gzipScheme) // Issue #806
+				rw := res.Writer
+				w, err := gzip.NewWriterLevel(rw, config.Level)
+				if err != nil {
+					return err
+				}
+				defer func() {
+					if res.Size == 0 {
+						if res.Header().Get(echo.HeaderContentEncoding) == gzipScheme {
+							res.Header().Del(echo.HeaderContentEncoding)
+						}
+						// We have to reset response to it's pristine state when
+						// nothing is written to body or error is returned.
+						// See issue #424, #407.
+						res.Writer = rw
+						w.Reset(ioutil.Discard)
+					}
+					w.Close()
+				}()
+				grw := &gzipResponseWriter{Writer: w, ResponseWriter: rw}
+				res.Writer = grw
+			}
+			return next(c)
+		}
+	}
+}
+
+func (w *gzipResponseWriter) WriteHeader(code int) {
+	if code == http.StatusNoContent { // Issue #489
+		w.ResponseWriter.Header().Del(echo.HeaderContentEncoding)
+	}
+	w.Header().Del(echo.HeaderContentLength) // Issue #444
+	w.ResponseWriter.WriteHeader(code)
+}
+
+func (w *gzipResponseWriter) Write(b []byte) (int, error) {
+	if w.Header().Get(echo.HeaderContentType) == "" {
+		w.Header().Set(echo.HeaderContentType, http.DetectContentType(b))
+	}
+	return w.Writer.Write(b)
+}
+
+func (w *gzipResponseWriter) Flush() {
+	w.Writer.(*gzip.Writer).Flush()
+}
+
+func (w *gzipResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	return w.ResponseWriter.(http.Hijacker).Hijack()
+}