1 files changed, 77 insertions, 0 deletions
diff --git a/internal/serving/disk/helpers.go b/internal/serving/disk/helpers.go
new file mode 100644
index 00000000..7ace39be
--- /dev/null
+++ b/internal/serving/disk/helpers.go
@@ -0,0 +1,77 @@
+package disk
+
+import (
+	"io"
+	"mime"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"gitlab.com/gitlab-org/gitlab-pages/internal/httputil"
+	"golang.org/x/sys/unix"
+)
+
+func endsWithSlash(path string) bool {
+	return strings.HasSuffix(path, "/")
+}
+
+func endsWithoutHTMLExtension(path string) bool {
+	return !strings.HasSuffix(path, ".html")
+}
+
+func openNoFollow(path string) (*os.File, error) {
+	return os.OpenFile(path, os.O_RDONLY|unix.O_NOFOLLOW, 0)
+}
+
+// Detect file's content-type either by extension or mime-sniffing.
+// Implementation is adapted from Golang's `http.serveContent()`
+// See https://github.com/golang/go/blob/902fc114272978a40d2e65c2510a18e870077559/src/net/http/fs.go#L194
+func detectContentType(path string) (string, error) {
+	contentType := mime.TypeByExtension(filepath.Ext(path))
+
+	if contentType == "" {
+		var buf [512]byte
+
+		file, err := os.Open(path)
+		if err != nil {
+			return "", err
+		}
+
+		defer file.Close()
+
+		// Using `io.ReadFull()` because `file.Read()` may be chunked.
+		// Ignoring errors because we don't care if the 512 bytes cannot be read.
+		n, _ := io.ReadFull(file, buf[:])
+		contentType = http.DetectContentType(buf[:n])
+	}
+
+	return contentType, nil
+}
+
+func acceptsGZip(r *http.Request) bool {
+	if r.Header.Get("Range") != "" {
+		return false
+	}
+
+	offers := []string{"gzip", "identity"}
+	acceptedEncoding := httputil.NegotiateContentEncoding(r, offers)
+	return acceptedEncoding == "gzip"
+}
+
+func handleGZip(w http.ResponseWriter, r *http.Request, fullPath string) string {
+	if !acceptsGZip(r) {
+		return fullPath
+	}
+
+	gzipPath := fullPath + ".gz"
+
+	// Ensure the .gz file is not a symlink
+	if fi, err := os.Lstat(gzipPath); err != nil || !fi.Mode().IsRegular() {
+		return fullPath
+	}
+
+	w.Header().Set("Content-Encoding", "gzip")
+
+	return gzipPath
+}