created_at2023-10-16 00:26:24.549874
updated_at2024-03-15 17:25:46.116717
descriptionCompact and streamable data format that works anywhere--from web apps to robots.



Compact and streamable data format that works anywhere--from web apps to robots. ## What's a Pact? Pacts describe the structure of _related_ types of **data**, each containing one or more **fields**. Pact data can encode to and decode from raw binary data streams, which means pacts are extra-helpful for making distributed or embedded apps that speak different languages or rely on low-level networking. > _Note_: For those familiar with other data > interchange formats, pacts have a lot in common > with things like the > [`proto`]( > schemas used by [`gRPC`]( and the > `capnp` schemas used by [Cap'n Proto]( Each data type in a pact can have the following kinds of fields: 1. Unsigned integers from `8` to `64` bits (`u8`, `u16`, `u32`, and `u64`). 2. Signed integers from `8` to `64` bits (`i8`, `i16`, `i32`, and `i64`). 3. Signed floating-point integers from `32` to `64` bits (`f32` and `f64`). 4. Booleans (`bool`). 5. UTF-8 encoded strings, AKA text (`string`). 6. _Other_ user-defined data types ("nested" data) 7. Lists of any of the things listed above. For information on how pact data is coded to and from binary data, refer to the [`codec`]( docs. ## How do I make a Pact? Pacts are made with TOML: ```toml ## An example pact. pact = 'MyGreeter' ## Data type in this pact ## named "Request". [data.1. Request] message = 'string' ## Another data type in this ## pact named "Response". [data.2. Response] message = 'string' ## This field of a Response is a ## list of strings, instead of just ## a single string, because it is ## surrounded by `[]`. friends = ['string'] ## This field of a Response is a ## copy of the request that the ## response is for, showing how ## we can nest other data types ## within data types. request = 'Request' ``` This example describes a `MyGreeter` pact with two kinds of data: `Request` and `Response`. Both of these data contain a `message` string, while the `Response` data contains a _list_ of strings called `friends` and a copy of the original `Request`. Every data description starts with a number called an **Ordinal**. Ordinals uniquely identify the different kinds of data in the same pact. The first data described by a pact always has ordinal `1`, and each additional data type in the same pact has an ordinal that is one higher than the previous data. Comments that start with `##` and come immediately before the `pact` name, a `data` name, or a field name, will be parsed as documentation for the item they precede. The easiest way to get started with TOML pacts in your own projects is via the [`pact-derive`]( crate. ## Can I change or "evolve" a Pact? Yes! Pact data is designed to evolve as a system's needs change: - New data types can be added to any pact. - New fields can be added to any data type. - Existing fields and data types can be renamed. If a system receives data of a new type it doesn't support, or containing new fields it doesn't support, the new information will be gracefully ignored. Conversely, if a system receives data that's _missing_ newly-added fields, the missing fields will be gracefully populated with default values. ## License Copyright 2024 Alicorn Systems, Inc. Licensed under the GNU Affero General Public License version 3, as published by the Free Software Foundation. Refer to [the license file](../LICENSE.txt) for more information. If you have any questions, please reach out to [``].
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cargo fmt