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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
//! # Low-level typesystem for the FFI layer of a component interface.
//!
//! This module provides the "FFI-level" typesystem of a UniFFI Rust Component, that is,
//! the C-style functions and structs and primitive datatypes that are used to interface
//! between the Rust component code and the foreign-language bindings.
//!
//! These types are purely an implementation detail of UniFFI, so consumers shouldn't
//! need to know about them. But as a developer working on UniFFI itself, you're likely
//! to spend a lot of time thinking about how these low-level types are used to represent
//! the higher-level "interface types" from the [`super::types::Type`] enum.
/// Represents the restricted set of low-level types that can be used to construct
/// the C-style FFI layer between a rust component and its foreign language bindings.
///
/// For the types that involve memory allocation, we make a distinction between
/// "owned" types (the recipient must free it, or pass it to someone else) and
/// "borrowed" types (the sender must keep it alive for the duration of the call).
#[derive(Debug, Clone, Hash, PartialEq, Eq)]
pub enum FfiType {
// N.B. there are no booleans at this layer, since they cause problems for JNA.
UInt8,
Int8,
UInt16,
Int16,
UInt32,
Int32,
UInt64,
Int64,
Float32,
Float64,
/// A `*const c_void` pointer to a rust-owned `Arc<T>`.
/// If you've got one of these, you must call the appropriate rust function to free it.
/// The templates will generate a unique `free` function for each T.
/// The inner string references the name of the `T` type.
RustArcPtr(String),
/// A byte buffer allocated by rust, and owned by whoever currently holds it.
/// If you've got one of these, you must either call the appropriate rust function to free it
/// or pass it to someone that will.
/// If the inner option is Some, it is the name of the external type. The bindings may need
/// to use this name to import the correct RustBuffer for that type.
RustBuffer(Option<String>),
/// A borrowed reference to some raw bytes owned by foreign language code.
/// The provider of this reference must keep it alive for the duration of the receiving call.
ForeignBytes,
/// A pointer to a single function in to the foreign language.
/// This function contains all the machinery to make callbacks work on the foreign language side.
ForeignCallback,
// TODO: you can imagine a richer structural typesystem here, e.g. `Ref<String>` or something.
// We don't need that yet and it's possible we never will, so it isn't here for now.
}
/// Represents an "extern C"-style function that will be part of the FFI.
///
/// These can't be declared explicitly in the UDL, but rather, are derived automatically
/// from the high-level interface. Each callable thing in the component API will have a
/// corresponding `FfiFunction` through which it can be invoked, and UniFFI also provides
/// some built-in `FfiFunction` helpers for use in the foreign language bindings.
#[derive(Debug, Default, Clone)]
pub struct FfiFunction {
pub(super) name: String,
pub(super) arguments: Vec<FfiArgument>,
pub(super) return_type: Option<FfiType>,
}
impl FfiFunction {
pub fn name(&self) -> &str {
&self.name
}
pub fn arguments(&self) -> Vec<&FfiArgument> {
self.arguments.iter().collect()
}
pub fn return_type(&self) -> Option<&FfiType> {
self.return_type.as_ref()
}
}
/// Represents an argument to an FFI function.
///
/// Each argument has a name and a type.
#[derive(Debug, Clone)]
pub struct FfiArgument {
pub(super) name: String,
pub(super) type_: FfiType,
}
impl FfiArgument {
pub fn name(&self) -> &str {
&self.name
}
pub fn type_(&self) -> FfiType {
self.type_.clone()
}
}
#[cfg(test)]
mod test {
// There's not really much to test here to be honest,
// it's mostly type declarations.
}
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