Yardl

Yardl is a simple schema language and command-line tool that generates domain types and serialization code.

Simple example

Given a Yardl definition like this:

# This is an example protocol, which is defined as a Header value
# followed by a stream of zero or more Sample values
MyProtocol: !protocol
  sequence:
    header: Header
    samples: !stream
      items: Sample

# Header is a record with a single string field
Header: !record
  fields:
    subject: string

# Sample is a record made up of a datetime and
# a vector of integers
Sample: !record
  fields:
    timestamp: datetime
    data: int*

After running yardl generate, you can write code like the following to write data to standard out in a compact binary format:

import sys
from sandbox import BinaryMyProtocolWriter, Header, Sample, DateTime

def generate_samples():
    yield Sample(timestamp=DateTime.now(), data=[1, 2, 3])
    yield Sample(timestamp=DateTime.now(), data=[4, 5, 6])

with BinaryMyProtocolWriter(sys.stdout.buffer) as w:
    w.write_header(Header(subject="Me"))
    w.write_samples(generate_samples())

And then another script can read it in from standard in:

import sys
from sandbox import BinaryMyProtocolReader

with BinaryMyProtocolReader(sys.stdin.buffer) as r:
    print(r.read_header())
    for sample in r.read_samples():
        print(sample)

Motivation

It is conceptually similar to, and inspired by, Avro, Protocol Buffers, Bond, and others, but it was designed primarily with raw medical instrument signal data in mind. Some of its features are:

• Persistence to HDF5 files as well as a compact binary format suitable for streaming over a network. There is also a much less efficient NDJSON format that is easier to manually inspect or use with other tools.
• Built-in support for multidimensional arrays and complex numbers.
• The schema is always embedded in the serialized data
• "Clean" generated code with types that are easy to program against.
• Generics
• Computed fields

Modeling a data domain in Yardl brings a number of benefits over writing the code by hand:

• Writing correct and efficient serialization code can be tricky
• Schema versioning, compatibility, and conversions are handled for you
• You do not need to worry about consistency across different programming languages
• Comments could be used to generate documentation

Getting Started

Please check out the project documentation.

Project Status

We are releasing this project order to get community feedback and contributions. It is not complete and is not ready for production use at this time. We expect to introduce breaking changes until the project reaches V1.

We currently support C++ and Python codegen. Other planned features include:

• Reading data with a different schema version
• MATLAB support
• References between packages
• Validating schema evolution is non-breaking
• Constraints
• Improvements to the language and editing experience

Building the Code in this Repo

We recommend opening repo in a dev container or a codespace. Otherwise, all the required dependencies are specified in the Conda environment.yml file in the repo root.

We use the just command runner to build and run tests. To get started, you should be able to run

$ just

from the repo root.

Contributing

This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.opensource.microsoft.com.

When you submit a pull request, a CLA bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., status check, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.

Trademarks

This project may contain trademarks or logos for projects, products, or services. Authorized use of Microsoft trademarks or logos is subject to and must follow Microsoft's Trademark & Brand Guidelines. Use of Microsoft trademarks or logos in modified versions of this project must not cause confusion or imply Microsoft sponsorship. Any use of third-party trademarks or logos are subject to those third-party's policies.