Does `encoding/gob` Guarantee Identical Output for Identical Go Objects?

The Deterministic Nature of Encoding/gob, with Caveats

Question: Can identical Go objects, such as x and y, expect identical output from gob_encode(x) and gob_encode(y)?

Answer: While the current implementation of encoding/gob generally ensures deterministic outcomes, there are exceptions to consider.

Deterministic Encoding:

The stream of encoded data (gobs) is self-describing, meaning each data item is preceded by its type specification. Hence, for the first occurrence of a given type, the type information is transmitted. When another value of the same type is encoded, only a reference to the previous specification is sent.

This deterministic behavior is evident in encoding simple values like integers. For example, the output of gob_encode(Int{1}) will always include the type specification followed by the value ([5 255 130 1 2 0]).

Potentially Non-Deterministic Encodings:

Maps: The involvement of maps introduces non-determinism due to the random iteration order of maps. During serialization, the map's key-value pairs may be transmitted in different sequences, resulting in variable encoded outputs.

Version Variance: It's crucial to note that the implementation of the gob package may evolve with different Go versions. While such changes prioritize backward compatibility, they might still lead to variations in the generated output.

Implications:

In most practical scenarios, the non-determinism introduced by maps is unlikely to pose significant issues. However, for applications requiring strict predictability in encoded outputs, it's advisable to consider alternative encoders. Additionally, developers should be aware of potential version-based differences in encoding behavior.

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