Refactor nanopb decoding methods (#1438)

Rather than decoding the type, and then the contents, decode them both at once.

2 files changed, 21 insertions, 0 deletions

diff --git a/Firestore/core/src/firebase/firestore/nanopb/reader.cc b/Firestore/core/src/firebase/firestore/nanopb/reader.cc
index 3b102f0..3e6d92e 100644
--- a/Firestore/core/src/firebase/firestore/nanopb/reader.cc
+++ b/Firestore/core/src/firebase/firestore/nanopb/reader.cc
@@ -46,6 +46,17 @@ Tag Reader::ReadTag() {
   return tag;
 }
 
+bool Reader::RequireWireType(pb_wire_type_t wire_type, Tag tag) {
+  if (!status_.ok()) return false;
+  if (wire_type != tag.wire_type) {
+    set_status(Status(FirestoreErrorCode::DataLoss,
+                      "Input proto bytes cannot be parsed (mismatch between "
+                      "the wiretype and the field number (tag))"));
+    return false;
+  }
+  return true;
+}
+
 void Reader::ReadNanopbMessage(const pb_field_t fields[], void* dest_struct) {
   if (!status_.ok()) return;
 
diff --git a/Firestore/core/src/firebase/firestore/nanopb/reader.h b/Firestore/core/src/firebase/firestore/nanopb/reader.h
index 7dd7432..76dc3b6 100644
--- a/Firestore/core/src/firebase/firestore/nanopb/reader.h
+++ b/Firestore/core/src/firebase/firestore/nanopb/reader.h
@@ -58,6 +58,16 @@ class Reader {
   Tag ReadTag();
 
   /**
+   * Ensures the specified tag is of the specified type. If not, then
+   * Reader::status() will return a non-ok value (with the code set to
+   * FirestoreErrorCode::DataLoss).
+   *
+   * @return Convenience indicator for success. (If false, then status() will
+   * return a non-ok value.)
+   */
+  bool RequireWireType(pb_wire_type_t wire_type, Tag tag);
+
+  /**
    * Reads a nanopb message from the input stream.
    *
    * This essentially wraps calls to nanopb's pb_decode() method. If we didn't