Adding upstream version 0.28.1.

Signed-off-by: Daniel Baumann <daniel@debian.org>

tools/router/rereadable_read_closer.go

@@ -0,0 +1,60 @@
+package router
+
+import (
+	"bytes"
+	"io"
+)
+
+var (
+	_ io.ReadCloser = (*RereadableReadCloser)(nil)
+	_ Rereader      = (*RereadableReadCloser)(nil)
+)
+
+// Rereader defines an interface for rewindable readers.
+type Rereader interface {
+	Reread()
+}
+
+// RereadableReadCloser defines a wrapper around a io.ReadCloser reader
+// allowing to read the original reader multiple times.
+type RereadableReadCloser struct {
+	io.ReadCloser
+
+	copy   *bytes.Buffer
+	active io.Reader
+}
+
+// Read implements the standard io.Reader interface.
+//
+// It reads up to len(b) bytes into b and at at the same time writes
+// the read data into an internal bytes buffer.
+//
+// On EOF the r is "rewinded" to allow reading from r multiple times.
+func (r *RereadableReadCloser) Read(b []byte) (int, error) {
+	if r.active == nil {
+		if r.copy == nil {
+			r.copy = &bytes.Buffer{}
+		}
+		r.active = io.TeeReader(r.ReadCloser, r.copy)
+	}
+
+	n, err := r.active.Read(b)
+	if err == io.EOF {
+		r.Reread()
+	}
+
+	return n, err
+}
+
+// Reread satisfies the [Rereader] interface and resets the r internal state to allow rereads.
+//
+// note: not named Reset to avoid conflicts with other reader interfaces.
+func (r *RereadableReadCloser) Reread() {
+	if r.copy == nil || r.copy.Len() == 0 {
+		return // nothing to reset or it has been already reset
+	}
+
+	oldCopy := r.copy
+	r.copy = &bytes.Buffer{}
+	r.active = io.TeeReader(oldCopy, r.copy)
+}