Source code
Revision control
Copy as Markdown
Other Tools
// Licensed under the Apache License, Version 2.0
// All files in the project carrying such notice may not be copied, modified, or distributed
// except according to those terms.
//! Utilities and wrappers for Microsoft COM interfaces in Windows.
//!
//! This works with the `Class` and `Interface` traits from the `winapi` crate.
use std::marker::PhantomData;
use std::mem;
use std::ops::Deref;
use std::ptr::{self, null_mut, NonNull};
use std::rc::Rc;
use std::slice;
use winapi::shared::minwindef::LPVOID;
use winapi::shared::{
winerror::HRESULT,
wtypesbase::{CLSCTX, CLSCTX_INPROC_SERVER, CLSCTX_LOCAL_SERVER},
};
use winapi::um::{
combaseapi::{CoCreateInstance, CoInitializeEx, CoTaskMemFree, CoUninitialize},
objbase::{COINIT_APARTMENTTHREADED, COINIT_MULTITHREADED},
unknwnbase::IUnknown,
};
use winapi::{Class, Interface};
use check_succeeded;
use error::{succeeded_or_err, HResult, ResultExt};
/// Wrap COM interfaces sanely
///
#[repr(transparent)]
pub struct ComRef<T>(NonNull<T>)
where
T: Interface;
impl<T> ComRef<T>
where
T: Interface,
{
/// Creates a `ComRef` to wrap a raw pointer.
/// It takes ownership over the pointer which means it does __not__ call `AddRef`.
/// `T` __must__ be a COM interface that inherits from `IUnknown`.
pub unsafe fn from_raw(ptr: NonNull<T>) -> ComRef<T> {
ComRef(ptr)
}
/// Casts up the inheritance chain
pub fn up<U>(self) -> ComRef<U>
where
T: Deref<Target = U>,
U: Interface,
{
unsafe { ComRef::from_raw(NonNull::new(self.into_raw().as_ptr() as *mut U).unwrap()) }
}
/// Extracts the raw pointer.
/// You are now responsible for releasing it yourself.
pub fn into_raw(self) -> NonNull<T> {
let p = self.0;
mem::forget(self);
p
}
fn as_unknown(&self) -> &IUnknown {
unsafe { &*(self.as_raw_ptr() as *mut IUnknown) }
}
/// Get another interface via `QueryInterface`.
///
/// If the call to `QueryInterface` fails or the resulting interface is null, return an error.
pub fn cast<U>(&self) -> Result<ComRef<U>, HResult>
where
U: Interface,
{
let mut obj = null_mut();
let hr =
succeeded_or_err(unsafe { self.as_unknown().QueryInterface(&U::uuidof(), &mut obj) })?;
NonNull::new(obj as *mut U)
.map(|obj| unsafe { ComRef::from_raw(obj) })
.ok_or_else(|| HResult::new(hr).function("IUnknown::QueryInterface"))
}
/// Obtains the raw pointer without transferring ownership.
///
/// Do __not__ release this pointer because it is still owned by the `ComRef`.
///
/// Do __not__ use this pointer beyond the lifetime of the `ComRef`.
pub fn as_raw(&self) -> NonNull<T> {
self.0
}
/// Obtains the raw pointer without transferring ownership.
///
/// Do __not__ release this pointer because it is still owned by the `ComRef`.
///
/// Do __not__ use this pointer beyond the lifetime of the `ComRef`.
pub fn as_raw_ptr(&self) -> *mut T {
self.0.as_ptr()
}
}
impl<T> Deref for ComRef<T>
where
T: Interface,
{
type Target = T;
fn deref(&self) -> &T {
unsafe { &*self.as_raw_ptr() }
}
}
impl<T> Clone for ComRef<T>
where
T: Interface,
{
fn clone(&self) -> Self {
unsafe {
self.as_unknown().AddRef();
ComRef::from_raw(self.as_raw())
}
}
}
impl<T> Drop for ComRef<T>
where
T: Interface,
{
fn drop(&mut self) {
unsafe {
self.as_unknown().Release();
}
}
}
/// A scope for automatic COM initialization and deinitialization.
///
/// Functions that need COM initialized can take a `&ComApartmentScope` argument and be sure that
/// it is so. It's recommended to use a thread local for this through the
/// [`INIT_MTA`](constant.INIT_MTA.html) or [`INIT_STA`](constant.INIT_STA.html) statics.
#[derive(Debug, Default)]
pub struct ComApartmentScope {
/// PhantomData used in lieu of unstable impl !Send + !Sync.
/// It must be dropped on the same thread it was created on so it can't be Send,
/// and references are meant to indicate that COM has been inited on the current thread so it
/// can't be Sync.
_do_not_send: PhantomData<Rc<()>>,
}
impl ComApartmentScope {
/// This thread should be the sole occupant of a single thread apartment
pub fn init_sta() -> Result<Self, HResult> {
unsafe { check_succeeded!(CoInitializeEx(ptr::null_mut(), COINIT_APARTMENTTHREADED)) }?;
Ok(Default::default())
}
/// This thread should join the process's multithreaded apartment
pub fn init_mta() -> Result<Self, HResult> {
unsafe { check_succeeded!(CoInitializeEx(ptr::null_mut(), COINIT_MULTITHREADED)) }?;
Ok(Default::default())
}
}
impl Drop for ComApartmentScope {
fn drop(&mut self) {
unsafe {
CoUninitialize();
}
}
}
thread_local! {
// TODO these examples should probably be in convenience functions.
/// A single thread apartment scope for the duration of the current thread.
///
/// # Example
/// ```
/// use comedy::com::{ComApartmentScope, INIT_STA};
///
/// fn do_com_stuff(_com: &ComApartmentScope) {
/// }
///
/// INIT_STA.with(|com| {
/// let com = match com {
/// Err(e) => return Err(e.clone()),
/// Ok(ref com) => com,
/// };
/// do_com_stuff(com);
/// Ok(())
/// }).unwrap()
/// ```
pub static INIT_STA: Result<ComApartmentScope, HResult> = ComApartmentScope::init_sta();
/// A multithreaded apartment scope for the duration of the current thread.
///
/// # Example
/// ```
/// use comedy::com::{ComApartmentScope, INIT_MTA};
///
/// fn do_com_stuff(_com: &ComApartmentScope) {
/// }
///
/// INIT_MTA.with(|com| {
/// let com = match com {
/// Err(e) => return Err(e.clone()),
/// Ok(ref com) => com,
/// };
/// do_com_stuff(com);
/// Ok(())
/// }).unwrap()
/// ```
pub static INIT_MTA: Result<ComApartmentScope, HResult> = ComApartmentScope::init_mta();
}
/// Create an instance of a COM class.
///
/// This is mostly just a call to `CoCreateInstance` with some error handling.
/// The CLSID of the class and the IID of the interface come from the winapi `RIDL` macro, which
/// defines `Class` and `Interface` implementations.
///
/// [`create_instance_local_server`](fn.create_instance_local_server.html) and
/// [`create_instance_inproc_server`](fn.create_instance_inproc_server.html) are convenience
/// functions for typical contexts.
pub fn create_instance<C, I>(ctx: CLSCTX) -> Result<ComRef<I>, HResult>
where
C: Class,
I: Interface,
{
get(|interface| unsafe {
CoCreateInstance(
&C::uuidof(),
ptr::null_mut(), // pUnkOuter
ctx,
&I::uuidof(),
interface as *mut *mut _,
)
})
.function("CoCreateInstance")
}
/// Create an instance of a COM class in the current process (`CLSCTX_LOCAL_SERVER`).
pub fn create_instance_local_server<C, I>() -> Result<ComRef<I>, HResult>
where
C: Class,
I: Interface,
{
create_instance::<C, I>(CLSCTX_LOCAL_SERVER)
}
/// Create an instance of a COM class in a separate process space on the same machine
/// (`CLSCTX_INPROC_SERVER`).
pub fn create_instance_inproc_server<C, I>() -> Result<ComRef<I>, HResult>
where
C: Class,
I: Interface,
{
create_instance::<C, I>(CLSCTX_INPROC_SERVER)
}
/// Call a COM method, returning a `Result`.
///
/// An error is returned if the call fails. The error is augmented with the name of the interface
/// and method, and the file name and line number of the macro usage.
///
/// `QueryInterface` is not used, the receiving interface must already be the given type.
///
/// # Example
///
/// ```no_run
/// # extern crate winapi;
/// #
/// # use winapi::um::bits::IBackgroundCopyJob;
/// #
/// # use comedy::com::ComRef;
/// # use comedy::{com_call, HResult};
/// #
/// fn cancel_job(job: &ComRef<IBackgroundCopyJob>) -> Result<(), HResult> {
/// unsafe {
/// com_call!(job, IBackgroundCopyJob::Cancel())?;
/// }
/// Ok(())
/// }
/// ```
#[macro_export]
macro_rules! com_call {
($obj:expr, $interface:ident :: $method:ident ( $($arg:expr),* )) => {{
use $crate::error::ResultExt;
$crate::error::succeeded_or_err({
let obj: &$interface = &*$obj;
obj.$method($($arg),*)
}).function(concat!(stringify!($interface), "::", stringify!($method)))
.file_line(file!(), line!())
}};
// support for trailing comma in method argument list
($obj:expr, $interface:ident :: $method:ident ( $($arg:expr),+ , )) => {{
$crate::com_call!($obj, $interface::$method($($arg),+))
}};
}
/// Get an interface pointer that is returned through an output parameter.
///
/// If the call returns a failure `HRESULT`, return an error.
///
///
/// # Null and Enumerators
/// If the method succeeds but the resulting interface pointer is null, this will return an
/// `HResult` error with the successful return code. In particular this can happen with
/// enumeration interfaces, which return `S_FALSE` when they write less than the requested number
/// of results.
pub fn get<I, F>(getter: F) -> Result<ComRef<I>, HResult>
where
I: Interface,
F: FnOnce(*mut *mut I) -> HRESULT,
{
let mut interface: *mut I = ptr::null_mut();
let hr = succeeded_or_err(getter(&mut interface as *mut *mut I))?;
NonNull::new(interface)
.map(|interface| unsafe { ComRef::from_raw(interface) })
.ok_or_else(|| HResult::new(hr))
}
/// Call a COM method, create a [`ComRef`](com/struct.ComRef.html) from an output parameter.
///
/// An error is returned if the call fails. The error is augmented with the name of the interface
/// and method, and the file name and line number of the macro usage.
///
/// # Null and Enumerators
/// If the method succeeds but the resulting interface pointer is null, this will return an
/// `HResult` error with the successful return code. In particular this can happen with
/// enumeration interfaces, which return `S_FALSE` when they write less than the requested number
/// of results.
///
/// # Example
///
/// ```no_run
/// # extern crate winapi;
/// # use winapi::shared::guiddef::GUID;
/// # use winapi::um::bits::{IBackgroundCopyManager, IBackgroundCopyJob};
/// # use comedy::com::ComRef;
/// # use comedy::{com_call_getter, HResult};
///
/// fn create_job(bcm: &ComRef<IBackgroundCopyManager>, id: &GUID)
/// -> Result<ComRef<IBackgroundCopyJob>, HResult>
/// {
/// unsafe {
/// com_call_getter!(
/// |job| bcm,
/// IBackgroundCopyManager::GetJob(id, job)
/// )
/// }
/// }
/// ```
#[macro_export]
macro_rules! com_call_getter {
(| $outparam:ident | $obj:expr, $interface:ident :: $method:ident ( $($arg:expr),* )) => {{
use $crate::error::ResultExt;
let obj: &$interface = &*$obj;
$crate::com::get(|$outparam| {
obj.$method($($arg),*)
}).function(concat!(stringify!($interface), "::", stringify!($method)))
.file_line(file!(), line!())
}};
// support for trailing comma in method argument list
(| $outparam:ident | $obj:expr, $interface:ident :: $method:ident ( $($arg:expr),+ , )) => {
$crate::com_call_getter!(|$outparam| $obj, $interface::$method($($arg),+))
};
}
/// Get a task memory pointer that is returned through an output parameter.
///
/// If the call returns a failure `HRESULT`, return an error.
///
/// # Null
/// If the method succeeds but the resulting pointer is null, this will return an
/// `Err(HResult)` with the successful return code.
pub fn get_cotaskmem<F, T>(getter: F) -> Result<CoTaskMem<T>, HResult>
where
F: FnOnce(*mut *mut T) -> HRESULT,
{
let mut ptr = ptr::null_mut() as *mut T;
let hr = succeeded_or_err(getter(&mut ptr))?;
NonNull::new(ptr)
.map(|ptr| unsafe { CoTaskMem::new(ptr) })
.ok_or_else(|| HResult::new(hr))
}
/// Call a COM method, create a [`CoTaskMem`](handle/struct.CoTaskMem.html) from an output
/// parameter.
///
/// An error is returned if the call fails or if the pointer is null. The error is augmented with
/// the name of the interface and method, and the file name and line number of the macro usage.
///
/// # Null
/// If the method succeeds but the resulting pointer is null, this will return an `HResult`
/// error with the successful return code.
///
/// # Example
///
/// ```no_run
/// # extern crate winapi;
/// # use winapi::shared::winerror::HRESULT;
/// # use winapi::um::bits::IBackgroundCopyManager;
/// # use comedy::com::{ComRef, CoTaskMem};
/// # use comedy::{com_call_taskmem_getter, HResult};
/// #
/// fn get_error_description(bcm: &ComRef<IBackgroundCopyManager>, lang_id: u32, hr: HRESULT)
/// -> Result<CoTaskMem<u16>, HResult>
/// {
/// unsafe {
/// com_call_taskmem_getter!(
/// |desc| bcm,
/// IBackgroundCopyManager::GetErrorDescription(hr, lang_id, desc)
/// )
/// }
/// }
/// ```
#[macro_export]
macro_rules! com_call_taskmem_getter {
(| $outparam:ident | $obj:expr, $interface:ident :: $method:ident ( $($arg:expr),* )) => {{
use $crate::error::ResultExt;
$crate::com::get_cotaskmem(|$outparam| {
$obj.$method($($arg),*)
}).function(concat!(stringify!($interface), "::", stringify!($method)))
.file_line(file!(), line!())
}};
// support for trailing comma in method argument list
(| $outparam:ident | $obj:expr, $interface:ident :: $method:ident ( $($arg:expr),+ , )) => {
$crate::com_call_taskmem_getter!(|$outparam| $obj, $interface::$method($($arg),+))
};
}
/// A Windows COM task memory pointer that will be automatically freed.
// I have only found this useful with strings, so that is the only access provided here by
// `as_slice_until_null()`. `Deref<Target=T>` would not be generally useful as task memory
// is usually encountered as variable length structures.
#[repr(transparent)]
#[derive(Debug)]
pub struct CoTaskMem<T>(NonNull<T>);
impl<T> CoTaskMem<T> {
/// Take ownership of COM task memory, which will be freed with `CoTaskMemFree()` upon drop.
///
/// # Safety
///
/// `p` should be the only copy of the pointer.
pub unsafe fn new(p: NonNull<T>) -> CoTaskMem<T> {
CoTaskMem(p)
}
}
impl<T> Drop for CoTaskMem<T> {
fn drop(&mut self) {
unsafe {
CoTaskMemFree(self.0.as_ptr() as LPVOID);
}
}
}
impl CoTaskMem<u16> {
/// Interpret as a null-terminated `u16` array, return as a slice without terminator.
pub unsafe fn as_slice_until_null(&self) -> &[u16] {
for i in 0.. {
if *self.0.as_ptr().offset(i) == 0 {
return slice::from_raw_parts(self.0.as_ptr(), i as usize);
}
}
unreachable!()
}
}