init

internal/reverseproxy/content.go

@@ -0,0 +1,31 @@
+package reverseproxy
+
+import (
+	"bufio"
+	"errors"
+	"io"
+	"io/ioutil"
+	"mime"
+	"net/http"
+)
+
+func ContentType(rsp *http.Response) string {
+	mimetype, _, _ := mime.ParseMediaType(rsp.Header.Get("Content-Type"))
+	if mimetype == "" {
+		b := bufio.NewReader(rsp.Body)
+		rsp.Body = ioutil.NopCloser(b)
+		mimetype = peekContentType(b)
+	}
+
+	return mimetype
+}
+
+// peekContentType peeks at the first 512 bytes of p, and attempts to detect
+// the content type.  Returns empty string if error occurs.
+func peekContentType(p *bufio.Reader) string {
+	byt, err := p.Peek(512)
+	if err != nil && !errors.Is(err, bufio.ErrBufferFull) && !errors.Is(err, io.EOF) {
+		return ""
+	}
+	return http.DetectContentType(byt)
+}