Noise Ser/de🔗ℹ

This is a companion package to Noise that provides utilities for serializing and deserializing data structures between Swift and Racket. Backwards-compatibility is not guaranteed.

1 Serialization & Deserialization🔗ℹ

1.1 Records🔗ℹ

A record is a data structure that is shared between Swift and Racket. In both languages, they are represented by structs. Use the raco command noise-serde-codegen to generate Swift definitions for records reachable from a given root module.

When a field is #:mutable, it uses var as its introducer in Swift instead of let. The option currently has no effect on the generated Racket code.

Changed in version 0.3 of package noise-serde-lib: Added the #:mutable field option.

1.2 Enumerations🔗ℹ

An enumeration is a tagged union of product types. In Racket, enum variants are represented by individual structs that inherit from a common base. In Swift, they are represented using regular enums.

1.3 Field Types🔗ℹ

Field types control how individual values are serialized and deserialized.

The Varint and UVarint field types serialize signed and unsigned integer values, respectively, using a variable-length encoding. In Swift, these values are represented by Int64 and UInt64.

When k is an enum or a record type, the enum or record must be extended to implement the Hashable protocol in Swift.

2 Backends🔗ℹ

The noise/backend module has an internal handler registry that is used to map remote procedure call ids to handler procedures.

The noise-serde-codegen command automatically generates Swift code to handle calling these procedures. In Swift, the RPC id, arg-labels and arg-ids are converted to camel case. The arg-labels have no meaning in Racket.

The noise-serde-codegen command automatically generates Swift code to handle installing Swift procedures for each callout.

In Racket, the above example binds a procedure named hello that may be called with a Human value in order to execute a Swift procedure. In Swift, the generated backend will contain a procedure with the following signature:

That procedure can be used to install a callback from the Swift side. Executing a callout on the Racket side before it’s been installed from the Swift side raises an exception.

Currently, the buffer used to decode data sent back to Swift via a callout is limited to 8KiB, so avoid sending large payloads. If necessary, have the Swift side call a regular RPC when it receives a callout instead.

Returns a procedure that stops the server when applied.

3 Callouts🔗ℹ

The noise/unsafe/callout module provides a facility for converting function pointer addresses to callable Racket procedures via the FFI. A callout box is a two-element struct containing a C function type and an optional Racket procedure of that type. Callout boxes start out empty and must be filled via a call to callout-box-install!. Callout boxes are themselves callable once filled.

Warning: these operations are inherently unsafe and you must take care that the function pointers installed in a box are kept immobile during the lifetime of that box.