Add expiry parsing into CertificateView.

PiperOrigin-RevId: 314437222
Change-Id: Ia7ff932ea0c21ef064f68f6242179d7b579d2a9f
diff --git a/common/quiche_data_reader.h b/common/quiche_data_reader.h
index cf62a16..f74f90d 100644
--- a/common/quiche_data_reader.h
+++ b/common/quiche_data_reader.h
@@ -87,6 +87,11 @@
   // endian.
   bool ReadTag(uint32_t* tag);
 
+  // Reads a sequence of a fixed number of decimal digits, parses them as an
+  // unsigned integer and returns them as a uint64_t.  Forwards internal
+  // iterator on success, may forward it even in case of failure.
+  bool ReadDecimal64(size_t num_digits, uint64_t* result);
+
   // Returns the remaining payload as a quiche::QuicheStringPiece.
   //
   // NOTE: Does not copy but rather references strings in the underlying buffer.