feat: implement HTTP connection hijacking for gzipWriter

- Add imports for `bufio`, `errors`, `net`, and `net/http`
- Ensure `gzipWriter` implements the `http.Hijacker` interface
- Implement `Hijack` method for `gzipWriter` to allow taking over the connection from the HTTP server
- Add `hijackableResponse` struct and methods to support hijacking in tests
- Add `TestResponseWriterHijack` to test the hijacking functionality of `gzipWriter`

Signed-off-by: appleboy <[email protected]>

Author: appleboy

gzip.go

@@ -1,7 +1,11 @@
 package gzip
 
 import (
+	"bufio"
 	"compress/gzip"
+	"errors"
+	"net"
+	"net/http"
 
 	"github.com/gin-gonic/gin"
 )
@@ -43,3 +47,21 @@ func (g *gzipWriter) WriteHeader(code int) {
 	g.Header().Del("Content-Length")
 	g.ResponseWriter.WriteHeader(code)
 }
+
+// Ensure gzipWriter implements the http.Hijacker interface.
+// This will cause a compile-time error if gzipWriter does not implement all methods of the http.Hijacker interface.
+var _ http.Hijacker = (*gzipWriter)(nil)
+
+// Hijack allows the caller to take over the connection from the HTTP server.
+// After a call to Hijack, the HTTP server library will not do anything else with the connection.
+// It becomes the caller's responsibility to manage and close the connection.
+//
+// It returns the underlying net.Conn, a buffered reader/writer for the connection, and an error
+// if the ResponseWriter does not support the Hijacker interface.
+func (g *gzipWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	hijacker, ok := g.ResponseWriter.(http.Hijacker)
+	if !ok {
+		return nil, nil, errors.New("the ResponseWriter doesn't support the Hijacker interface")
+	}
+	return hijacker.Hijack()
+}

gzip_test.go

@@ -1,11 +1,13 @@
 package gzip
 
 import (
+	"bufio"
 	"bytes"
 	"compress/gzip"
 	"context"
 	"fmt"
 	"io"
+	"net"
 	"net/http"
 	"net/http/httptest"
 	"net/http/httputil"
@@ -15,6 +17,7 @@ import (
 
 	"github.com/gin-gonic/gin"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 const (
@@ -344,3 +347,49 @@ func TestCustomShouldCompressFn(t *testing.T) {
 	assert.Equal(t, "19", w.Header().Get("Content-Length"))
 	assert.Equal(t, testResponse, w.Body.String())
 }
+
+type hijackableResponse struct {
+	Hijacked bool
+	header   http.Header
+}
+
+func newHijackableResponse() *hijackableResponse {
+	return &hijackableResponse{header: make(http.Header)}
+}
+
+func (h *hijackableResponse) Header() http.Header       { return h.header }
+func (h *hijackableResponse) Write([]byte) (int, error) { return 0, nil }
+func (h *hijackableResponse) WriteHeader(int)           {}
+func (h *hijackableResponse) Flush()                    {}
+func (h *hijackableResponse) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	h.Hijacked = true
+	return nil, nil, nil
+}
+
+func TestResponseWriterHijack(t *testing.T) {
+	req, _ := http.NewRequestWithContext(context.Background(), "GET", "/", nil)
+	req.Header.Add(headerAcceptEncoding, "gzip")
+
+	router := gin.New()
+	router.Use(Gzip(
+		DefaultCompression,
+		WithCustomShouldCompressFn(func(_ *gin.Context) bool {
+			return false
+		}),
+	)).Use(gin.HandlerFunc(func(c *gin.Context) {
+		hj, ok := c.Writer.(http.Hijacker)
+		require.True(t, ok)
+
+		_, _, err := hj.Hijack()
+		assert.Nil(t, err)
+		c.Next()
+	}))
+	router.GET("/", func(c *gin.Context) {
+		c.Header("Content-Length", strconv.Itoa(len(testResponse)))
+		c.String(200, testResponse)
+	})
+
+	hijackable := newHijackableResponse()
+	router.ServeHTTP(hijackable, req)
+	assert.True(t, hijackable.Hijacked)
+}