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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()
}
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