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Data Encoding/Decoding

To optimize how data is sent and received over the network, Gear uses the parity-scale-codec - a Rust implementation of the SCALE Codec. This codec is used by the Substrate nodes' internal runtime. SCALE is a lightweight format that enables the serialization and deserialization of data. Encoding (and decoding) data using SCALE makes it highly suitable for resource-constrained execution environments like blockchain runtimes and low-power/low-memory devices.

To use the SCALE codec in a program, add it to Cargo.toml:

[dependencies]

// ...
codec = { package = "parity-scale-codec", version = "3.6", default-features = false }
use codec::{Decode, Encode};

#[derive(Encode, Decode)]
enum MyType {
    MyStruct { field: ... },
    ...
}
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The Encode and Decode traits are needed when using wrapped methods from gstd, such as: msg::load, msg::send, msg::reply, msg::send_for_reply, etc.

In methods like msg::load_bytes, msg::send_bytes, or msg::reply_bytes, operations are performed with a set of bytes, so nothing needs to be decoded/encoded.

Learn more about the SCALE Codec here.

scale-info​

scale-info is a library to describe Rust types, intended for providing information about the structure of encodable SCALE types.

The definitions provide third-party tools (e.g., a UI client) with information about how to decode types agnostic of language. The interface that uses scale-info for Gear programs is called metadata. It defines incoming and outgoing types for all necessary entry points and allows programs and the client part to understand each other.

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Learn more about using metadata in a program.

To use scale-info in a project:

[dependencies]

// ...
scale-info = { version = "2.9", default-features = false, features = ["derive"] }

Learn more about scale-info here.