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pub extern crate libloading;
use std::ffi::OsStr;
#[doc(hidden)]
pub trait ExternFnPtr {
type FnPtr;
}
#[doc(hidden)]
pub trait LoadFnPtr<G> {
fn load_from_lib(libs: &mut G);
}
#[macro_export]
macro_rules! lazy_extern {
(
libgroup $groupname:ident : $grouptype:ident;
$(lib $libname:ident = $libpath:expr;)*
$(
$(#[$($meta:tt)*])*
extern $abi:tt fn $fnname:ident($($argname:ident : $argty:ty),*) -> $retty:ty;
)*
) => {
$(
#[doc(hidden)]
#[allow(non_camel_case_types)]
pub enum $fnname {}
impl $crate::ExternFnPtr for $fnname {
type FnPtr = unsafe extern $abi fn($($argname : $argty),*) -> $retty;
}
lazy_extern! {
@process_fn_meta
$groupname $grouptype
$abi $fnname($($argname : $argty),*; $retty);
$(#[$($meta)*])*
}
)*
#[allow(non_snake_case)]
pub struct $grouptype {
pub $($libname : Option<$crate::libloading::Library>,)*
pub $($fnname : Option<<$fnname as $crate::ExternFnPtr>::FnPtr>,)*
}
lazy_static! {
pub static ref $groupname : $grouptype = {
#[allow(non_snake_case)] {
$(let $libname = $crate::LibSpecifier::load_lib($libpath).ok();)*
$(let $fnname = None;)*
let mut group = $grouptype {
$($libname,)*
$($fnname,)*
};
$(<$fnname as $crate::LoadFnPtr<$grouptype>>::load_from_lib(&mut group);)*
group
}
};
}
};
(
@process_fn_meta
$groupname:ident $grouptype:ident
$abi:tt $fnname:ident($($argname:ident : $argty:ty),*; $retty:ty);
$(; doc $doc:expr)*
) => {
#[allow(non_snake_case)]
$(#[doc = $doc])*
pub unsafe fn $fnname($($argname : $argty),*) -> $retty {
($groupname.$fnname
.expect("You should use feature_test if you don't know whether this function will be loaded")
)($($argname),*)
}
};
(
@process_fn_meta
$groupname:ident $grouptype:ident
$abi:tt $fnname:ident($($argname:ident : $argty:ty),*; $retty:ty);
#[doc = $meta:expr]
$(#[$($rest:tt)*])*
$(; doc $doc:expr)*
) => {
lazy_extern! {
@process_fn_meta
$groupname $grouptype
$abi $fnname($($argname : $argty),*; $retty);
$(#[$($rest)*])*
$(; doc $doc)*
; doc $meta
}
};
(
@process_fn_meta
$groupname:ident $grouptype:ident
$abi:tt $fnname:ident($($argname:ident : $argty:ty),*; $retty:ty);
#[lib($libname:ident)]
$(#[$($rest:tt)*])*
$(; doc $doc:expr)*
) => {
#[doc(hidden)]
impl $crate::LoadFnPtr<$grouptype> for $fnname {
fn load_from_lib(libs: &mut $grouptype) {
let sym = ::std::option::Option::as_ref(&libs.$libname)
.and_then(|lib| {
unsafe {
let func: $crate::libloading::Symbol<<$fnname as $crate::ExternFnPtr>::FnPtr> =
lib.get(concat!(stringify!($fnname), "\0").as_bytes()).ok()?;
Some(*func)
}
});
libs.$fnname = sym;
}
}
lazy_extern! {
@process_fn_meta
$groupname $grouptype
$abi $fnname($($argname : $argty),*; $retty);
$(#[$($rest)*])*
$(; doc $doc)*
}
};
(
@process_fn_meta
$groupname:ident $grouptype:ident
$abi:tt $fnname:ident($($argname:ident : $argty:ty),*; $retty:ty);
#[feature_test($feature:ident)]
$(#[$($rest:tt)*])*
$(; doc $doc:expr)*
) => {
pub fn $feature() -> bool {
::std::option::Option::is_some(&$groupname.$fnname)
}
lazy_extern! {
@process_fn_meta
$groupname $grouptype
$abi $fnname($($argname : $argty),*; $retty);
$(#[$($rest)*])*
$(; doc $doc)*
}
};
}
pub trait LibSpecifier {
fn load_lib(spec: Self) -> libloading::Result<libloading::Library>;
}
impl<'a> LibSpecifier for &'a OsStr {
fn load_lib(spec: Self) -> libloading::Result<libloading::Library> {
libloading::Library::new(spec)
}
}
impl<'a> LibSpecifier for &'a str {
fn load_lib(spec: Self) -> libloading::Result<libloading::Library> {
libloading::Library::new(spec)
}
}
impl LibSpecifier for libloading::Result<libloading::Library> {
fn load_lib(spec: Self) -> libloading::Result<libloading::Library> {
spec
}
}
impl LibSpecifier for libloading::Library {
fn load_lib(spec: Self) -> libloading::Result<libloading::Library> {
Ok(spec)
}
}