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use crate::*;
use std::marker::PhantomData;
use std::sync::atomic::{AtomicPtr, Ordering};
type DllGetActivationFactory = extern "system" fn(name: RawPtr, factory: *mut RawPtr) -> ErrorCode;
/// Attempts to load and cache the factory interface for the given WinRT class. This is automatically
// used by the generated bindings and should not generally be used directly.
pub struct FactoryCache<C, I> {
shared: AtomicPtr<std::ffi::c_void>,
_c: PhantomData<C>,
_i: PhantomData<I>,
}
impl<C, I> FactoryCache<C, I> {
pub const fn new() -> Self {
Self {
shared: AtomicPtr::new(::std::ptr::null_mut()),
_c: PhantomData,
_i: PhantomData,
}
}
}
impl<C: RuntimeName, I: Interface> FactoryCache<C, I> {
pub fn call<R, F: FnOnce(&I) -> Result<R>>(&mut self, callback: F) -> Result<R> {
loop {
// Attempt to load a previously cached factory pointer.
let ptr = self.shared.load(Ordering::Relaxed);
// If a pointer is found, the cache is primed and we're good to go.
if !ptr.is_null() {
return callback(unsafe { std::mem::transmute(&ptr) });
}
// Otherwise, we load the factory the usual way.
let factory = factory::<C, I>()?;
// If the factory is agile, we can safely cache it.
if factory.cast::<IAgileObject>().is_ok() {
if self
.shared
.compare_exchange_weak(
std::ptr::null_mut(),
unsafe { std::mem::transmute_copy(&factory) },
Ordering::Relaxed,
Ordering::Relaxed,
)
.is_ok()
{
std::mem::forget(factory);
}
} else {
// Otherwise, for non-agile factories we simply use the factory
// and discard after use as it is not safe to cache.
return callback(&factory);
}
}
}
}
/// Attempts to load the factory interface for the given WinRT class.
pub fn factory<C: RuntimeName, I: Interface>() -> Result<I> {
let mut factory: Option<I> = None;
let name = HString::from(C::NAME);
unsafe {
// First attempt to get the activation factory via the OS.
let code = RoGetActivationFactory(name.abi(), &I::IID, factory.set_abi());
// Treat any delay-load errors like standard errors, so that the heuristics
// below can still load registration-free libraries on Windows versions below 10.
let mut code = code.unwrap_or_else(|code| code);
// If this fails because combase hasn't been loaded yet then load combase
// automatically so that it "just works" for apartment-agnostic code.
if code == ErrorCode::CO_E_NOTINITIALIZED {
let mut _cookie = std::ptr::null_mut();
// Won't get any delay-load errors here if we got CO_E_NOTINITIALIZED, so quiet the
// warning from the #[must_use] on the returned Result<>.
let _ = CoIncrementMTAUsage(&mut _cookie);
// Now try a second time to get the activation factory via the OS.
code = RoGetActivationFactory(name.abi(), &I::IID, factory.set_abi())
.unwrap_or_else(|code| code);
}
// If this succeeded then return the resulting factory interface.
if code.is_ok() {
return code.and_some(factory);
}
// If not, first capture the error information from the failure above so that we
// can ultimately return this error information if all else fails.
let original: Error = code.into();
// Now attempt to find the factory's implementation heuristically.
let mut path = C::NAME;
// Remove the suffix until a match is found. For example, if the class name is
// "A.B.TypeName" then this will first attempt to load "A.B.dll" and if that
// fails it will attempt "A.dll" before giving up.
while let Some(pos) = path.rfind('.') {
path = &path[..pos];
let mut library = String::with_capacity(path.len() + 4);
library.push_str(path);
library.push_str(".dll");
if let Ok(function) = delay_load(&library, "DllGetActivationFactory") {
let function: DllGetActivationFactory = std::mem::transmute(function);
let mut abi = std::ptr::null_mut();
let _ = function(name.abi(), &mut abi);
if abi.is_null() {
continue;
}
let factory: IActivationFactory = std::mem::transmute(abi);
return factory.cast();
}
}
Err(original)
}
}
demand_load! {
"ole32.dll" {
fn CoIncrementMTAUsage(cookie: *mut RawPtr) -> ErrorCode;
}
"combase.dll" {
fn RoGetActivationFactory(hstring: RawPtr, interface: &Guid, result: *mut RawPtr) -> ErrorCode;
}
}