com_impl/
lib.rs

1#![cfg(windows)]
2
3//! Implements a COM Object struct with automatic reference counting and implements
4//! IUnknown for you. This covers the most common use cases of creating COM objects
5//! from Rust. Supports generic parameters!
6//!
7//! ```
8//! use winapi::ctypes::c_void;
9//! use winapi::shared::winerror::{ERROR_INVALID_INDEX, HRESULT, HRESULT_FROM_WIN32, S_OK};
10//! use winapi::um::dwrite::{IDWriteFontFileStream, IDWriteFontFileStreamVtbl};
11//! use wio::com::ComPtr;
12//!
13//! #[repr(C)]
14//! #[derive(com_impl::ComImpl)]
15//! #[interfaces(IDWriteFontFileStream)]
16//! pub struct FileStream {
17//!     vtbl: com_impl::VTable<IDWriteFontFileStreamVtbl>,
18//!     refcount: com_impl::Refcount,
19//!     write_time: u64,
20//!     file_data: Vec<u8>,
21//! }
22//!
23//! impl FileStream {
24//!     pub fn new(write_time: u64, data: Vec<u8>) -> ComPtr<IDWriteFontFileStream> {
25//!         let ptr = FileStream::create_raw(write_time, data);
26//!         let ptr = ptr as *mut IDWriteFontFileStream;
27//!         unsafe { ComPtr::from_raw(ptr) }
28//!     }
29//! }
30//!
31//! #[com_impl::com_impl]
32//! unsafe impl IDWriteFontFileStream for FileStream {
33//!     unsafe fn get_file_size(&self, size: *mut u64) -> HRESULT {
34//!         *size = self.file_data.len() as u64;
35//!         S_OK
36//!     }
37//!
38//!     unsafe fn get_last_write_time(&self, write_time: *mut u64) -> HRESULT {
39//!         *write_time = self.write_time;
40//!         S_OK
41//!     }
42//!
43//!     unsafe fn read_file_fragment(
44//!         &self,
45//!         start: *mut *const c_void,
46//!         offset: u64,
47//!         size: u64,
48//!         ctx: *mut *mut c_void,
49//!     ) -> HRESULT {
50//!         if offset > std::isize::MAX as u64 || size > std::isize::MAX as u64 {
51//!             return HRESULT_FROM_WIN32(ERROR_INVALID_INDEX);
52//!         }
53//!
54//!         let offset = offset as usize;
55//!         let size = size as usize;
56//!
57//!         if offset + size > self.file_data.len() {
58//!             return HRESULT_FROM_WIN32(ERROR_INVALID_INDEX);
59//!         }
60//!
61//!         *start = self.file_data.as_ptr().offset(offset as isize) as *const c_void;
62//!         *ctx = std::ptr::null_mut();
63//!
64//!         S_OK
65//!     }
66//!
67//!     unsafe fn release_file_fragment(&self, _ctx: *mut c_void) {
68//!         // Nothing to do
69//!     }
70//! }
71//!
72//! fn main() {
73//!     let ptr = FileStream::new(100, vec![0xDE, 0xAF, 0x00, 0xF0, 0x01]);
74//!
75//!     // Do things with ptr
76//! }
77//! ```
78
79extern crate derive_com_impl;
80extern crate winapi;
81
82use std::sync::atomic::{AtomicUsize, Ordering};
83
84pub use derive_com_impl::{com_impl, ComImpl};
85
86#[repr(transparent)]
87/// Wrapper for the C++ VTable member of a COM object.
88///
89/// When you're using `#[derive(ComImpl)]`, this should be the first member of your struct.
90pub struct VTable<T> {
91    pub ptr: *const T,
92}
93
94impl<T> VTable<T> {
95    pub fn new(ptr: &'static T) -> Self {
96        VTable { ptr }
97    }
98}
99
100impl<T> std::fmt::Debug for VTable<T> {
101    fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
102        fmt.debug_tuple("VTable").field(&self.ptr).finish()
103    }
104}
105
106/// Trait that allows accessing the VTable for all of the COM interfaces your object
107/// implements.
108pub unsafe trait BuildVTable<T: 'static> {
109    const VTBL: T;
110    fn static_vtable() -> VTable<T>;
111}
112
113#[derive(Debug)]
114/// Refcounter object for automatic COM Object implementations. Atomically keeps track of
115/// the reference count so that the implementation of IUnknown can properly deallocate
116/// the object when all reference counts are gone.
117pub struct Refcount {
118    count: AtomicUsize,
119}
120
121impl Default for Refcount {
122    fn default() -> Self {
123        Refcount {
124            count: AtomicUsize::new(1),
125        }
126    }
127}
128
129impl Refcount {
130    #[inline]
131    /// `fetch_add(1, Acquire) + 1`
132    pub unsafe fn add_ref(&self) -> u32 {
133        self.count.fetch_add(1, Ordering::Acquire) as u32 + 1
134    }
135
136    #[inline]
137    /// `fetch_sub(1, Release) - 1`
138    pub unsafe fn release(&self) -> u32 {
139        self.count.fetch_sub(1, Ordering::Release) as u32 - 1
140    }
141}
com_impl/lib.rs

com_impl/
lib.rs
