Crate com_impl

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Expand description

Implements a COM Object struct with automatic reference counting and implements IUnknown for you. This covers the most common use cases of creating COM objects from Rust. Supports generic parameters!

use winapi::ctypes::c_void;
use winapi::shared::winerror::{ERROR_INVALID_INDEX, HRESULT, HRESULT_FROM_WIN32, S_OK};
use winapi::um::dwrite::{IDWriteFontFileStream, IDWriteFontFileStreamVtbl};
use wio::com::ComPtr;

#[repr(C)]
#[derive(com_impl::ComImpl)]
#[interfaces(IDWriteFontFileStream)]
pub struct FileStream {
    vtbl: com_impl::VTable<IDWriteFontFileStreamVtbl>,
    refcount: com_impl::Refcount,
    write_time: u64,
    file_data: Vec<u8>,
}

impl FileStream {
    pub fn new(write_time: u64, data: Vec<u8>) -> ComPtr<IDWriteFontFileStream> {
        let ptr = FileStream::create_raw(write_time, data);
        let ptr = ptr as *mut IDWriteFontFileStream;
        unsafe { ComPtr::from_raw(ptr) }
    }
}

#[com_impl::com_impl]
unsafe impl IDWriteFontFileStream for FileStream {
    unsafe fn get_file_size(&self, size: *mut u64) -> HRESULT {
        *size = self.file_data.len() as u64;
        S_OK
    }

    unsafe fn get_last_write_time(&self, write_time: *mut u64) -> HRESULT {
        *write_time = self.write_time;
        S_OK
    }

    unsafe fn read_file_fragment(
        &self,
        start: *mut *const c_void,
        offset: u64,
        size: u64,
        ctx: *mut *mut c_void,
    ) -> HRESULT {
        if offset > std::isize::MAX as u64 || size > std::isize::MAX as u64 {
            return HRESULT_FROM_WIN32(ERROR_INVALID_INDEX);
        }

        let offset = offset as usize;
        let size = size as usize;

        if offset + size > self.file_data.len() {
            return HRESULT_FROM_WIN32(ERROR_INVALID_INDEX);
        }

        *start = self.file_data.as_ptr().offset(offset as isize) as *const c_void;
        *ctx = std::ptr::null_mut();

        S_OK
    }

    unsafe fn release_file_fragment(&self, _ctx: *mut c_void) {
        // Nothing to do
    }
}

fn main() {
    let ptr = FileStream::new(100, vec![0xDE, 0xAF, 0x00, 0xF0, 0x01]);

    // Do things with ptr
}

Structs

  • Refcount
    Refcounter object for automatic COM Object implementations. Atomically keeps track of the reference count so that the implementation of IUnknown can properly deallocate the object when all reference counts are gone.
  • VTable
    Wrapper for the C++ VTable member of a COM object.

Traits

  • BuildVTable
    Trait that allows accessing the VTable for all of the COM interfaces your object implements.

Attribute Macros

Derive Macros