feat: Waku v2 bridge

Issue #12610

vendor/github.com/anacrolix/missinggo/section_writer.go

@@ -0,0 +1,23 @@
+package missinggo
+
+import "io"
+
+type SectionWriter struct {
+	w        io.WriterAt
+	off, len int64
+}
+
+func NewSectionWriter(w io.WriterAt, off, len int64) *SectionWriter {
+	return &SectionWriter{w, off, len}
+}
+
+func (me *SectionWriter) WriteAt(b []byte, off int64) (n int, err error) {
+	if off >= me.len {
+		err = io.EOF
+		return
+	}
+	if off+int64(len(b)) > me.len {
+		b = b[:me.len-off]
+	}
+	return me.w.WriteAt(b, me.off+off)
+}