Struct libffi::middle::Builder

pub struct Builder { /* fields omitted */ }

Provides a builder-style API for constructing CIFs and closures.

To use a builder, first construct it using Builder::new. The default calling convention is ffi_abi_FFI_DEFAULT_ABI, and the default function type is extern "C" fn() (or in C, void(*)()). Add argument types to the function type with the arg and args methods. Set the result type with res. Change the calling convention, if necessary, with abi.

Once the builder is configured, construct a Cif with into_cif or a closure with into_closure, into_closure_mut, or into_closure_once.

Examples

use std::mem;
use std::os::raw::c_void;

use libffi::middle::*;
use libffi::low;

unsafe extern "C" fn lambda_callback<F: Fn(u64, u64) -> u64>(
    _cif: &low::ffi_cif,
    result: &mut u64,
    args: *const *const c_void,
    userdata: &F)
{
    let args: *const &u64 = mem::transmute(args);
    let arg1 = **args.offset(0);
    let arg2 = **args.offset(1);

    *result = userdata(arg1, arg2);
}

let lambda = |x: u64, y: u64| x + y;

let closure = Builder::new()
    .arg(Type::u64())
    .arg(Type::u64())
    .res(Type::u64())
    .into_closure(lambda_callback, &lambda);

unsafe {
    let fun: &unsafe extern "C" fn(u64, u64) -> u64
        = mem::transmute(closure.code_ptr());

    assert_eq!(11, fun(5, 6));
    assert_eq!(12, fun(5, 7));
}

Methods

impl Builder

pub fn new() -> Self

Constructs a Builder.

pub fn arg(self, type_: Type) -> Self

Adds a type to the argument type list.

pub fn args<I>(self, types: I) -> Self where
    I: IntoIterator<Item = Type>, 

Adds several types to the argument type list.

pub fn res(self, type_: Type) -> Self

Sets the result type.

pub fn abi(self, abi: FfiAbi) -> Self

Sets the calling convention.

pub fn into_cif(self) -> Cif

Builds a CIF.

pub fn into_closure<U, R>(
    self,
    callback: Callback<U, R>,
    userdata: &U
) -> Closure

Builds an immutable closure.

Arguments

• callback — the function to call when the closure is invoked
• userdata — the pointer to pass to callback along with the arguments when the closure is called

Result

The new closure.

pub fn into_closure_mut<U, R>(
    self,
    callback: CallbackMut<U, R>,
    userdata: &mut U
) -> Closure

Builds a mutable closure.

Arguments

• callback — the function to call when the closure is invoked
• userdata — the pointer to pass to callback along with the arguments when the closure is called

Result

The new closure.

pub fn into_closure_once<U: Any, R>(
    self,
    callback: CallbackOnce<U, R>,
    userdata: U
) -> ClosureOnce

Builds a one-shot closure.

Arguments

• callback — the function to call when the closure is invoked
• userdata — the object to pass to callback along with the arguments when the closure is called

Result

The new closure.

Trait Implementations

impl Clone for Builder

fn clone(&self) -> Builder

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Default for Builder

fn default() -> Self

Returns the "default value" for a type.

impl Debug for Builder

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.