Over the Air (OTA) Package Files

Objective

Provide a packaging and distribution format for code built using Hydro-SDK.

Background

Common Flutter Runtime (CFR) provides an execution environment for Lua 5.2 bytecode chunks. The Lua 5.2 bytecode chunk format is not suitable for more general usecases.

.ota package files are used during development time. They are produced and served by the run-project SDK-tool and consumed by the RunComponent widget in a running host app. In release mode, the RunComponent widget downloads .ota package files from Registry and saves them in an on-device cache.

.ota Package Format

.ota files are tar archives compressed with bzip2. A manifest.json file in their root contains an entries array listing the path and sha256 hash of every contained file. The mountableChunk field in manifest.json contains the path to the bytecode chunk to be ran by CFR. The signature field in manifest.json contains the signature of the sha256 hash of the concatentation of all of the sha256 hashes of every file contained in the package, signed using an RSA private key. This signature can be verified using the associated package public key.

Future Work

It is expected in the future that .ota packages will be used to deliver assets like images and configuration files.