ASPN-LCM

This Python module contains the Python variant of ASPN-LCM.

Release Versioning

This project implements a versioning scheme similar to semantic versioning SemVer, but much lighter. This project does not define an API and therefore has no concrete definition of what constitutes a breaking change.

Nonetheless, if a new release would require significant changes downstream we will attempt to communicate that by incrementing the major version. If there are new features or newly deprecated features, we will attempt to communicate that by incrementing the minor version. If the changes are primarily bug fixes, we will attempt to communicate that by incrementing the patch version.

However, we make no concrete promises about whether or not a given release will be compatible with your project downstream. You may experience breaking changes on minor or patch releases. If this is an issue for your project, we recommend you pin to a specific version of this project rather than a range.

Fingerprints

Each message defined by this project has a unique fingerprint, a hash calculated from all of the fields of the message, recursively. If any fingerprints change this indicates a hard incompatibility with previous versions of this project. In this case, we will increment the major version if any fingerprint changes. Additionally, we maintain a table of fingerprint changes so you can know which messages' compatibility changed.

Breaking Changes

Below is a history of breaking changes between the listed version and the previous version.

2.0.0

This version includes breaking changes to the following ASPN messages, meaning that they have new fingerprints:

• measurement_direction_2d_to_points
• measurement_direction_3d_to_points
• measurement_image
• measurement_satnav_subframe

This occurred because certain fields were changed from int16_t to byte in order to better represent ASPN in LCM. Specifically, this change was made to fields which represented opaque data streams (e.g. image data). This change has the benefit of reducing the size of these fields by half, which is important since some of these messages can be very large (e.g. images).

Legacy Submodule

The ASPN-LCM Python module ships with the latest version of the previous major release via the legacy submodule. This submodule is provided as a convenience in order to more easily convert legacy data to a format compatible with the latest version of ASPN-LCM after breaking changes are made.

For example, if between 1.0 and 2.0 the fingerprint for the measurement_image message changed, it will still be possible to decode that message using aspn23_lcm.legacy.measurement_image.

Only the previous major release will be provided.