Google protocol buffers compare

Question

I want to compare two Messages or (two sub parameters) of Google protocol buffers. I don't find an API to achieve it.

Any ideas?

Answer 1

You can use the class google::protobuf::util::MessageDifferencer for this. I think it's only available since v3.0.2:

Introduced new utility functions/classes in the google/protobuf/util directory:

• MessageDifferencer: compare two proto messages and report their differences.

#include <google/protobuf/util/message_differencer.h>  MessageDifferencer::Equals(msg1, msg2); 

Answer 2

You can rely on the fact that all of your protobuf messages inherit from the google::protobuf::MesageLite type, which in turn has everything you need to compare any two protobuf messages, regardless of if they are even of the same derived type:

bool operator==(const google::protobuf::MessageLite& msg_a,                 const google::protobuf::MessageLite& msg_b) {   return (msg_a.GetTypeName() == msg_b.GetTypeName()) &&       (msg_a.SerializeAsString() == msg_b.SerializeAsString()); } 

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EDIT

As was pointed out in the comments below, and especially for map fields, this answer is incorrect. map elements have non-deterministic ordering. Use MessageDifferencer if map fields might be present in your messages.