Crate uniffi_core

Runtime support code for uniffi

This crate provides the small amount of runtime code that is required by the generated uniffi component scaffolding in order to transfer data back and forth across the C-style FFI layer, as well as some utilities for testing the generated bindings.

The key concept here is the FfiConverter trait, which is responsible for converting between a Rust type and a low-level C-style type that can be passed across the FFI:

• How to represent values of the Rust type in the low-level C-style type system of the FFI layer.
• How to “lower” values of the Rust type into an appropriate low-level FFI value.
• How to “lift” low-level FFI values back into values of the Rust type.
• How to write values of the Rust type into a buffer, for cases where they are part of a compound data structure that is serialized for transfer.
• How to read values of the Rust type from buffer, for cases where they are received as part of a compound data structure that was serialized for transfer.
• How to return values of the Rust type from scaffolding functions.

This logic encapsulates the Rust-side handling of data transfer. Each foreign-language binding must also implement a matching set of data-handling rules for each data type.

In addition to the core FfiConverter trait, we provide a handful of struct definitions useful for passing core rust types over the FFI, such as RustBuffer.

Re-exports

• pub use ffi::*;
• pub use metadata::*;

Modules

• deps
• ffi
  Types that can cross the FFI boundary.
• metadata
  Pack UniFFI interface metadata into byte arrays

Macros

• assert_compatible_version
  Assert that the uniffi runtime version matches an expected value.
• derive_ffi_traits
  Derive FFI traits
• ffi_converter_arc_forward
  Macro to implement FfiConverterArc<T> for a UniFfiTag using a different UniFfiTag
• ffi_converter_forward
  Macro to implement FfiConverter<T> for a UniFfiTag using a different UniFfiTag
• ffi_converter_rust_buffer_lift_and_lower
  Macro to implement lowering/lifting using a RustBuffer

Traits

• ConvertError
• FfiConverter
  Generalized FFI conversions
• FfiConverterArc
  FfiConverter for Arc-types
• HandleAlloc
  Manage handles for Arc<Self> instances
• Lift
  Lift values passed by the foreign code over the FFI into Rust values
• LiftRef
  Lift references
• LiftReturn
  Return foreign values to Rust
• Lower
  Lower Rust values to pass them to the foreign code
• LowerError
  Return Rust error values
• LowerReturn
  Return Rust values to the foreign code
• TypeId
  Type ID metadata

Functions

• check_compatible_version
  Check whether the uniffi runtime version is compatible a given uniffi_bindgen version.
• check_remaining
  A helper function to ensure we don’t read past the end of a buffer.

Type Aliases

• Result
  Result<T, Error>