[][src]Macro wiggle::from_witx

from_witx!() { /* proc-macro */ }

This macro expands to a set of pub Rust modules:

  • The types module contains definitions for each typename declared in the witx document. Type names are translated to the Rust-idiomatic CamelCase.

  • For each module defined in the witx document, a Rust module is defined containing definitions for that module. Module names are teanslated to the Rust-idiomatic snake_case.

    • For each @interface func defined in a witx module, an abi-level function is generated which takes ABI-level arguments, along with a "context" struct (whose type is given by the ctx field in the macro invocation) and a GuestMemory implementation.

    • A public "module trait" is defined (called the module name, in SnakeCase) which has a &self method for each function in the module. These methods takes idiomatic Rust types for each argument and return Result<($return_types),$error_type>

Arguments are provided using Rust struct value syntax.

  • witx takes a list of string literal paths. Paths are relative to the CARGO_MANIFEST_DIR of the crate where the macro is invoked.
  • ctx takes a type name. This type must implement all of the module traits


use wiggle::{GuestPtr, GuestErrorType};

/// The test witx file `arrays.witx` lives in the test directory. For a
/// full-fledged example with runtime tests, see `tests/arrays.rs` and
/// the rest of the files in that directory.
    witx: ["../tests/arrays.witx"],
    ctx: YourCtxType,

/// The `ctx` type for this wiggle invocation.
pub struct YourCtxType {}

/// `arrays.witx` contains one module called `arrays`. So, we must
/// implement this one method trait for our ctx type:
impl arrays::Arrays for YourCtxType {
    /// The arrays module has two methods, shown here.
    /// Note that the `GuestPtr` type comes from `wiggle`,
    /// whereas the witx-defined types like `Excuse` and `Errno` come
    /// from the `pub mod types` emitted by the `wiggle::from_witx!`
    /// invocation above.
    fn reduce_excuses(&self, _a: &GuestPtr<[GuestPtr<types::Excuse>]>)
        -> Result<types::Excuse, types::Errno> {
    fn populate_excuses(&self, _a: &GuestPtr<[GuestPtr<types::Excuse>]>)
        -> Result<(), types::Errno> {

/// For all types used in the `Error` position of a `Result` in the module
/// traits, you must implement `GuestErrorType` which tells wiggle-generated
/// code what value to return when the method returns Ok(...).
impl GuestErrorType for types::Errno {
    fn success() -> Self {

/// The `types::GuestErrorConversion` trait is also generated with a method for
/// each type used in the `Error` position. This trait allows wiggle-generated
/// code to convert a `wiggle::GuestError` into the right error type. The trait
/// must be implemented for the user's `ctx` type.

impl types::GuestErrorConversion for YourCtxType {
    fn into_errno(&self, _e: wiggle::GuestError) -> types::Errno {