74 lines
3.4 KiB
Markdown
74 lines
3.4 KiB
Markdown
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# Encoding
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The `codec` is used everywhere in the Cosmos SDK to encode and decode structs and interfaces. The specific codec used in the Cosmos SDK is called `go-amino`. {synopsis}
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## Pre-requisite Readings
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- [Cosmos SDK Encoding](https://docs.cosmos.network/master/core/encoding.html) {prereq}
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## Encoding Formats
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The Cosmos SDK utilizes two binary wire encoding protocols, [Amino](https://github.com/tendermint/go-amino/)
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and [Protocol Buffers](https://developers.google.com/protocol-buffers), where Amino
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is an object encoding specification. It is a subset of Proto3 with an extension for
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interface support. See the [Proto3 spec](https://developers.google.com/protocol-buffers/docs/proto3)
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for more information on Proto3, which Amino is largely compatible with (but not with Proto2).
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Due to Amino having significant performance drawbacks, being reflection-based, and
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not having any meaningful cross-language/client support, Protocol Buffers, specifically
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[gogoprotobuf](https://github.com/gogo/protobuf/), is being used in place of Amino.
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Note, this process of using Protocol Buffers over Amino is still an ongoing process.
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Binary wire encoding of types in the Cosmos SDK can be broken down into two main
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categories, client encoding and store encoding. Client encoding mainly revolves
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around transaction processing and signing, whereas store encoding revolves around
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types used in state-machine transitions and what is ultimately stored in the Merkle
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tree.
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For store encoding, protobuf definitions can exist for any type and will typically
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have an Amino-based "intermediary" type. Specifically, the protobuf-based type
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definition is used for serialization and persistence, whereas the Amino-based type
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is used for business logic in the state-machine where they may converted back-n-forth.
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Note, the Amino-based types may slowly be phased-out in the future so developers
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should take note to use the protobuf message definitions where possible.
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In the `codec` package, there exists two core interfaces, `Marshaler` and `ProtoMarshaler`,
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where the former encapsulates the current Amino interface except it operates on
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types implementing the latter instead of generic `interface{}` types.
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In addition, there exists three implementations of `Marshaler`. The first being
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`AminoCodec`, where both binary and JSON serialization is handled via Amino. The
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second being `ProtoCodec`, where both binary and JSON serialization is handled
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via Protobuf. Finally, `HybridCodec`, a codec that utilizes Protobuf for binary
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serialization and Amino for JSON serialization. The `HybridCodec` is typically
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the codec that used in majority in situations as it's easier to use for client
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and state serialization.
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This means that modules may use Amino or Protobuf encoding but the types must
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implement `ProtoMarshaler`. If modules wish to avoid implementing this interface
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for their types, they may use an Amino codec directly.
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### Amino
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Every module uses an Amino codec to serialize types and interfaces. This codec typically
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has types and interfaces registered in that module's domain only (e.g. messages),
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but there are exceptions like `x/gov`. Each module exposes a `RegisterCodec` function
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that allows a user to provide a codec and have all the types registered. An application
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will call this method for each necessary module.
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### Protobuf
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<!-- TODO: -->
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## RLP
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<!-- TODO: -->
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## Next {hide}
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Learn about [events](./events.md) {hide}
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