derive-com-impl 0.1.0-alpha3

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!

#[macro_use]
extern crate derive_com_impl;

extern crate com_impl;
extern crate winapi;
extern crate wio;

use com_impl::{VTable, Refcount};
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(ComImpl)]
#[interfaces(IDWriteFontFileStream)]
pub struct FileStream {
vtbl: VTable<IDWriteFontFileStreamVtbl>,
refcount: 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]
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
}